We would like to thank Engineering and Physical Sciences Research Council (EPSRC, United Kingdom) Interdisciplinary Research Collaboration grant EP/K03197X/1, the Department of Health and the Wellcome Trust through the Health Innovation Challenge Fund (HICF). Funding Reference Number: 0510-069.

All human lung tissue was obtained following informed consent and the study was approved by the Regional Ethics Committee.
1. Preparation of Biological Samples
<ol>
	<li>Preparation of probes
	<ol>
		<li>Make up a 1 mM stock solution of each probe (e.g., Calcein AM, UBI-3, UBI-10, etc.) in sterile dH2O, using a fine balance to weigh the freeze-dried probe compound11. Calculate the volume of dH2O to add based on the weighed mass and molecular weight of the probe.</li>
	</ol>
	</li>
	<li>Preparation of bacterial cultures 
	NOTE: For this method, Staphylococcus aureus was used as the exemplar strain. Any appropriate bacterial strain can be selected.&#160;Any commercial dye that labels bacteria with an appropriate excitation and emission spectra can be selected to positively label the bacteria.
	<ol>
		<li>Select a single colony of desired bacterial strain from a fresh Lysogeny Broth (LB) agar plate using a sterile loop. Inoculate the colony into 10 mL of LB in a 50 mL centrifuge tube by dipping the end of the loop into the culture media. Incubate at 37 &#176;C, 250 rpm for 16 h (or overnight).</li>
		<li>Determine the OD595 of the overnight culture by adding 100 &#181;L of the overnight culture to 900 &#181;L LB in a 1 mL cuvette. Measure the OD at 595 nm (using a cuvette with 1 mL LB as a blank) in a spectrophotometer. Multiply the obtained OD by 10 to obtain the OD for the overnight culture.</li>
		<li>Subculture the overnight culture. Do this by adjusting the optical density at 595 nm (OD595) to 0.1 in 10 mL of fresh LB. Calculate the required volume of overnight culture to be added to 10 mL fresh LB to adjust the OD595 to 0.1. Incubate the culture at 37 &#176;C, 250 rpm until the culture reaches mid-log phase (OD595 0.6 - 0.8), approximately 4 h.</li>
		<li>Measure the culture optical density (step 1.2.2) and harvest 1 x 108 colony forming units (CFU) (OD595 ~1-1 x 108 CFU/mL) of the bacterial culture into a 1.5 mL microtube (e.g., if the bacterial culture is OD595 0.6, collect 1.67 mL). Centrifuge the culture at 10,000 x g at room temperature for 1 min to pellet the bacteria. Wash the pellet twice in phosphate buffered saline (PBS) by resuspending (pipetting up and down carefully) the pellet in 1 mL PBS, centrifuging as above, discarding the supernatant, and repeating. Take care not to dislodge the bacterial pellet when removing the supernatant. Resuspend the final pellet in 1 mL PBS. 
		NOTE: Prepare as many samples as required for each labeling procedure. The protocol may be paused here for up to 1 h, followed by step 1.2.5.1, 1.2.5.2, or 1.2.5.3.</li>
		<li>Bacterial staining
		<ol>
			<li>To label the bacteria with Calcein AM, add the dye to a final concentration of 1 &#181;M into the washed bacterial culture. Incubate the culture for 30 min at 37 &#176;C with shaking at 300 rpm. Wash the counterstained bacterial suspension in PBS 3 times by centrifugation as in step 1.2.4 to remove excess dye. Resuspend in 1 mL PBS, dilute 100 &#181;L 1:1 in PBS to obtain 200 &#181;L of OD595 0.5 Calcein AM stained bacteria. The protocol may be paused here for up to 1 h.</li>
			<li>To label the bacteria with test probes (e.g., UBI-3 or UBI-10), dilute 100 &#181;L of the bacterial culture 1:1 in PBS to obtain OD595 0.5 in 200 &#181;L PBS. Add either of the probes to a final concentration of 10 &#181;M. Invert the microtube several times to ensure thorough mixing of the bacteria and the probe. 
			NOTE: Imaging should be performed immediately after the addition of the probe to mimic the clinical scenario.</li>
			<li>To prepare the control unstained bacterial samples, dilute 100 &#181;L of the culture 1:1 with PBS to obtain 200 &#181;L of unstained OD595 0.5 sample.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Preparation of ex vivo human lung tissue 
	NOTE: Human lung tissue samples were obtained from patients undergoing surgical resection for lung carcinoma. All tissue used for imaging was obtained from samples of normal lung tissue away from the cancerous growth. Samples were taken fresh from the operating theatre and stored in microtubes or centrifuge tubes at -80 &#176;C until use.
	<ol>
		<li>Immediately before imaging, remove the human lung tissue sample from the freezer on dry ice. At room temperature, allow the tissue to thaw slightly; just enough to be sliced with a scalpel into 1 x 4 mm2 sections. 
		NOTE: The level of thawing is important; too frozen and the tissue will not slice without chipping off, too thawed and the tissue is too soft to slice.</li>
		<li>Using forceps, place the sliced human lung tissue into wells of a 96-well clear flat-bottom tissue culture plate. Return any unused human lung tissue immediately to the storage container and place on dry ice for transport back to the -80 &#176;C freezer.</li>
		<li>Add 100 &#181;L PBS to each lung tissue sample with a pipette. Use the pipette tip to ensure all the tissue is covered in the PBS (and not stuck to the walls of the well). The tissue will swell slightly and may float. Leave the PBS on the sample for a few minutes to allow any blood to leach from the tissue into the solution. Remove as much of the PBS as possible. The tissue may block the end of the pipette tip; try to angle the plate/tip placement in order to prevent this.</li>
		<li>Pipette 100 &#181;L of unstained, Calcein AM labeled, or test-probe labeled bacteria to each well containing lung tissue. Also set up controls with lung tissue and 100 &#181;L PBS. To these control wells, probes without bacteria can be added to measure any increase in background fluorescence and/or non-specific activation of the probe by lung tissue alone. A well with lung tissue and PBS should also be included.</li>
	</ol>
	</li>
</ol>
2. Imaging with the CLE Device with FCFM
<ol>
	<li>Set up of CLE device 
	NOTE: Prepare the CLE system 20 min before calibration to allow the laser to warm up.
	<ol>
		<li>Press the on/off switch on the back of the transformer of the system and turn on the designated computer. Press the on/off button on the front of the laser scanning unit (LSU). Confirm the appearance of the green light, indicating that the unit is switched on.</li>
		<li>Double click on the CLE software icon. Enter the login details and wait for the LSU to initialize (10 - 30 s).</li>
		<li>For use of new FCFM imaging fibers, installation with the supplied CD is necessary. Insert the installation CD into the computer CD drive and follow the onscreen instructions.</li>
		<li>Clean the FCFM imaging fiber connector unit with a fiber cleaner. Rub the connector on the cleaning ribbon in a forward motion to remove any dust/dirt. Remove the protective yellow cap from the front of the LSU.</li>
		<li>Prepare the LSU hub by gently rotating the silver hub anti-clockwise until it stops. Insert the FCFM imaging fiber connector into the hub with the flat side of the connector facing upwards. Hold the fiber in place and rotate the silver hub clockwise until it clicks twice. Complete the connection by rotating the silver hub clockwise by a further 45&#176;. 
		NOTE: If the fiber is not recognized, check that the FCFM imaging fiber has been installed and connected in the correct orientation.</li>
		<li>Follow the instructions that will pop-up for completing the FCFM imaging fiber calibration. There are 3 steps: (1) FCFM imaging fiber test (steps 2.1.7 - 2.1.8), (2) background acquisition (step 2.1.9), (3) fiber detection (step 2.1.10).</li>
		<li>Press the &#39;start laser&#39; button on the screen. The laser will center.</li>
		<li>Select fresh vials (yellow: calibrate; red: clean; blue: rinse) from the calibration kit and follow the onscreen instructions: place the distal end of the FCFM imaging fiber into the yellow vial and watch for the increase in fluorescence on the monitor, then place the fiber tip into the red vial (without stirring). Wait for the fluorescence (as shown on the computer monitor) to disappear. Finally rinse the fiber tip in the blue vial. 
		NOTE: If the fluorescence does not disappear, clean the FCFM imaging fiber with 8% H2O2 and lens cleaning tissues and begin again. Repeat the process until satisfactory results are obtained (the image quality is clear, and no marks from dirt are apparent).</li>
		<li>Place the FCFM imaging fiber into the blue vial. Press &#39;start laser&#39; followed by &#39;calculate&#39; when this becomes an option.</li>
		<li>Place the FCFM imaging fiber into the yellow vial. Press &#39;start laser&#39; followed by &#39;calculate&#39; when this becomes an option.</li>
		<li>During the automated calibration, clean the distal end of the FCFM imaging fiber by placing in the red vial for &#62;10 s, followed by the blue vial for &#62;4 s, as indicated by the software.</li>
	</ol>
	</li>
	<li>Data collection with CLE
	<ol>
		<li>Following setup, a window to select storage location and file prefix will open. Select the desired folder for data storage, and name the prefix accordingly.</li>
		<li>Place the foot pedals so that they can be easily accessed by the operator. Left pedal: laser on/off; center pedal: pause; right pedal: record/stop. 
		NOTE: The laser controls can also be accessed through onscreen controls.</li>
		<li>Click &#39;start&#39; onscreen or press the left foot-pedal to turn on the laser. This will start acquisition and obtain images using 100% laser power and a frame rate of 12 frames/s (default settings). 
		NOTE: For other applications, these settings can be altered on screen if necessary, depending on the sample type.</li>
		<li>Image each of the bacterial suspension samples.
		<ol>
			<li>Insert the distal end of the FCFM imaging fiber and move the fiber slowly through the suspension to interrogate the sample.</li>
			<li>Record videos of any length (up to 10 min) by pressing the right foot pedal or selecting the onscreen record controls, as the fiber moves slowly around the sample.</li>
			<li>Clean the distal end of the FCFM imaging fiber with 8% H2O2 and lens cleaning tissues between samples. 
			&#8203;NOTE: Typical video lengths of 10 - 30 s are sufficient for in vitro imaging.</li>
		</ol>
		</li>
		<li>Image each of the lung tissue samples.
		<ol>
			<li>Insert the distal end of the FCFM imaging fiber into the sample, ensuring that direct contact between the end of the fiber and the tissue is made. Gently move the end of the imaging fiber around to interrogate the sample. 
			NOTE: Lifting the end of the fiber away from the tissue will remove the tissue from the focal plane; however, this may be used to image labeled bacteria that are not adhered to the tissue.</li>
			<li>Record videos of any length (up to 10 min) by pressing the right foot pedal or selecting the onscreen record controls, as the fiber moves slowly around the sample. 
			NOTE: Typically, video lengths of 30 s are sufficient for ex vivo imaging on tissue.</li>
			<li>Clean the distal end of the FCFM imaging fiber with lens cleaning tissues and 8% H2O2 between samples.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Turning off the system
	<ol>
		<li>Switch the laser off by pressing the left foot pedal or by clicking the on-screen button.</li>
		<li>Disconnect the FCFM imaging fiber from the CLE device by turning the silver LSU hub anticlockwise until it stops. Remove the FCFM imaging fiber from the LSU hub by gently pulling the fiber connector from the LSU.</li>
		<li>Clean and disinfect the FCFM imaging fiber with 8% H2O2 and lens cleaning tissues. Return the protective caps to the proximal end of the FCFM imaging fiber and the front of the LSU unit. Place the fiber gently in the storage box.</li>
		<li>Close the data capture software and copy any saved files to an external USB device. Shut down the computer and turn off the LSU device by pressing the front panel I/O for 3 s until the green light disappears.</li>
		<li>Dispose of human lung tissue and bacteria according to local regulations.</li>
	</ol>
	</li>
</ol>
3. Data Analysis
<ol>
	<li>Open the software and import the files for analysis by selecting the appropriate directory on the computer through the &#39;Go to&#39; icon on the software dashboard. Alternatively, files can be dragged and dropped into the software dashboard.</li>
	<li>Double click on each video file to open them. The videos will automatically play with optimized color lookup table (LUT) and color table adjust. Disable the automatic intensity scaling, by clicking on the wand button above the intensity scale bar. The feature is disabled when there is no black shadowing around the button. 
	NOTE: Automatic intensity scaling must be disabled to prevent continuous contrast enhancement throughout each video, making it impossible to compare and analyze videos from the same data set.</li>
	<li>Select the desired intensity scaling by moving the minimum and maximum bars to give the best contrast. Use the histogram tool when selecting the intensity scaling to ensure the broadest dynamic range is captured. 
	NOTE: Ensure that the dynamic range is such that the images are not saturated (i.e. limit the white regions of the image, which indicate saturation), so that low intensity features are not missed.</li>
	<li>Once the desired scaling has been achieved, right click over the dropdown menu button listed as &#39;Default (Green)&#39;. Select the option to save the LUT. Save the LUT to a desired location.</li>
	<li>For each other video within the data set, apply the same LUT by right clicking over the &#39;Default (Green)&#39; drop down menu and select &#39;Load LUT&#39;. Select the appropriate file to apply consistent intensity scaling to all videos within a dataset.</li>
	<li>Export processed videos by clicking on the &#39;movie reel&#39; button. Select the desired video format, e.g. &#39;for presentation purposes&#39;, which will produce a .mpg file. Press &#39;Export&#39; and chose file location to save the video file. Snapshots of single frames can be exported by clicking the &#39;camera&#39; button. It is possible to save a .png, .bmp, or .jpg file. Choose the file destination and press save. 
	NOTE: Videos can then be imported into any software for preparation of presentations or further quantification. Labeled bacteria are visualized as green &#39;blinking&#39; dots in the video. The lung tissue structure will be apparent as ordered fluorescent strands, with alveolar space appearing black.</li>
</ol>

<ol>
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Dis. 57, 139-170 (2013).</li><li>Zumla, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+point+of+care+diagnostic+tests+for+viral+and+bacterial+respiratory+tract+infections-needs,+advances,+and+future+prospects.">Rapid point of care diagnostic tests for viral and bacterial respiratory tract infections-needs, advances, and future prospects.</a> Lancet Infect. Dis. 14 (11), 1123-1135 (2014).</li><li>Neumann, H., Kiesslich, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Yamada's Textbook of Gastroent. , 2944-2949 (2015).</li><li>Chauhan, S. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Confocal+laser+endomicroscopy.">Confocal laser endomicroscopy.</a> Gastrointest Endosc. 80 (6), 928-938 (2014).</li><li>Goetz, M., Malek, N. 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P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+rise+of+carbapenem+resistance+in+Europe:+just+the+tip+of+the+iceberg.">The rise of carbapenem resistance in Europe: just the tip of the iceberg.</a> Antimicrob Resist Infect Control. 2 (1), 6 (2013).</li><li>Chastre, J., Fagon, J. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventilator-associated+Pneumonia.">Ventilator-associated Pneumonia.</a> Am. J. Respir Crit Care Med. 165 (7), 867-903 (2002).</li><li>Krstaji&#263;, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-color+widefield+fluorescence+microendoscopy+enables+multiplexed+molecular+imaging+in+the+alveolar+space+of+human+lung+tissue.">Two-color widefield fluorescence microendoscopy enables multiplexed molecular imaging in the alveolar space of human lung tissue.</a> J Biomed Opt. 21 (4), 046009-046009 (2016).</li></ol>

KD: Founder Director of Edinburgh Molecular Imaging. Received consultancy from Mauna Kea Technologies as advisor. 
MB: Founder Director of Edinburgh Molecular Imaging.

Lower respiratory tract infections account for the second highest burden of disease globally12,13, and a substantial rise in the number of infections attributed to antimicrobial resistant bacteria has been reported14. Pneumonia remains a common cause for hospitalization. In the ICU, the development of a pneumonia is compounded by diagnostic uncertainty and is associated with an extremely high mortality rate15. During the onset of pneumonia, bacteria proliferate within the alveolar space of the distal lung, an area that is relatively sterile, with minimal microbiota in health.
This method describes relatively late stage ex vivo validation of bacteria-specific optical imaging probes11, but the design, synthesis, and probe evaluation prior to beginning this validation step is imperative, as previously shown11.
CLE is an emerging clinical technique for interrogating disease states in situ in real-time. It offers many advantages over traditional techniques for investigating suspected pulmonary pathology, which may involve a biopsy and collection of the lavage fluid. Biopsies are invasive and can cause morbidity and mortality in ventilated patients, and collected lavage fluid is often contaminated with bacteria from the upper airways. The use of CLE in the detection of pneumonia is however somewhat limited due to the poor availability of compatible imaging probes which may provide functional information of disease, despite many concerted efforts10. Combining CLE with optical agents offers the prospect of diagnosing pneumonia faster and less invasively compared to current standard practice.
The critical steps to this protocol are in the sample preparation and setup of the CLE platform. Obtaining human tissue relevant to the final clinical application is also important, such as human lung tissue as demonstrated within this study. It is necessary to use human tissue because the extent of tissue autofluorescence shows large inter-species variation, and may therefore mislead the sensitivity of the bacteria-probe being imaged. Additionally, obtaining ethics for retrieval and use of human lung tissue is essential. From a technical level, correct cleaning, attachment of the imaging fiber to the imaging LSU platform, and calibration is essential for good resolution and consistent imaging, as is ensuring equivalent numbers of bacteria are added to each lung tissue sample. To further expand the utility of this method for screening panels of probes, repeating the procedure with a range of pathogens, such as those likely to be causative agents of pneumonia is necessary.
The largest limitation of this technique is that the clinically approved CLE device has only one laser (488 nm). Therefore, currently, the selection of fluorophore for probe design is limited for use with this system, though clinically approved single color devices do exist with excitation wavelengths of 660 nm and near-infrared. It is highly desirable to have a second laser line implemented within the same device to enable a probe to be developed with a spectrally distinct fluorophore to improve bacteria-probe sensitivity over the level of tissue autofluorescence. Whilst dual-color CLE devices are under development, they are either not clinically approved and/or their cost is significant16.
CLE in vitro using pathogenic bacteria and ex vivo human lung tissue to screen potential probes bridges the gap between conventional in vitro techniques such as flow cytometry and CLSM, and clinical utility. This step offers confidence when selecting promising compounds to carry forward to be coupled with clinical CLE imaging; and will provide indication as to whether the tested probe maintains target specificity, or demonstrates any off-target labeling, such as binding directly to tissue, or shows instability with host proteolytic enzymes. It would also be pertinent to add each of the activatable probes directly to samples of human lung tissue plus bacteria, to fully characterize the speed of probe binding and activation in real-time.
We believe that our pipeline for rapidly screening novel bacteria-specific probes to assess their potential for imaging within the distal lung of patients will result in much faster translation to the clinic. This is largely because the bacteria-specific probe could be delivered locally within the lung through a catheter inserted down the working channel of a bronchoscope, meaning that microdose (&#60;100 &#181;g) amounts could be delivered. Therefore, systemic delivery and biodistribution of the compound is not a concern, as is the case for many other infection targets within the body, or with nuclear imaging. Moreover, delivering the imaging probe in such a small dose reduces the risk of toxicity related complications (although toxicity screening would be required for translation). Following instillation of the probe, the catheter could then be replaced by the FCFM fiber and the same region of the lung interrogated by CLE, much the same way we have performed within this method. Imaging should be performed rapidly following installation of the probe before the probe washes away to undetectable concentrations.
It is also important to note that screening of disease-identifying probes by this technique should not be limited to bacterial-imaging agents, but could also extend to the validation of probes with alternative targets, such as inflammation. This approach should also be adaptable to other disease locations within the body where imaging via FCFM is permissible.

This technique describes a rapid screening process for evaluating bacteria-specific optical imaging agents within ex vivo human lung tissue by CLE using FCFM for the rapid identification of compounds with potential clinical utility for visualizing bacteria in the distal lung in situ.
There is an urgent global requirement to ration antimicrobial prescribing in the era of rising antimicrobial resistance1. To this end, the development of diagnostic methods which act to identify bacterial infection with high specificity, sensitivity, and in real-time are highly sought2. Current techniques to confirm a diagnosis of pneumonia in critically unwell patients, such as those within intensive care units (ICUs), often rely on interpreting non-specific clinical or radiological features alongside bacterial culture techniques from aspirated fluids/tissues, which can take up to 3 days to produce results. Furthermore, bacterial culture from fluid instilled into the distal lung and retrieved is prone to contamination from more proximal airways3 and is often culture negative due to concomitant antimicrobial therapy or poor sampling techniques. Additionally, molecular techniques such as polymerase chain reaction are overly sensitive when used on aspirated fluids, risking overtreatment of patients. An emerging diagnostic approach is molecular optical imaging, making in situ molecular pathology of tissues a possibility; however, the development and validation of optical imaging compounds is required. Nonetheless, direct visualization of bacteria, via activatable optical probes is potentially a very powerful method to allow the study of the presence and evolution of pneumonia in the patient, and importantly, could be used to study host-pathogen interactions in response to therapies in real-time in situ. 
CLE is an established investigative procedure in multiple diseases4, including within the fields of gastroenterology5, oncology6,7, and for interrogating airways and alveolar sacs8,9. It enables point-of-care structural imaging of diseased tissue using a fiber imaging bundle, which passes through the working channel of a clinical endoscope and forms direct contact with the tissue surface to be imaged by confocal microscopy. However, one limitation that remains is the need for generic contrast agents. Therefore, the use of disease specific probes, such as specific bacterial agents, could vastly expand the utility of this modality by directly visualizing bacteria at the site of suspected infection. Optical agents offer many advantages over other techniques by enabling real-time, high resolution imaging with diagnostic potential. Moreover, optical probes offer the prospect of multiplexing for interrogating multiple targets, all achieved at a relatively low cost. A number of optical agents are under development for such a purpose, however none have yet been successfully implemented within the clinic10. We have synthesized a library of small molecule chemical probes with specificity towards bacteria and developed a rapid, effective pipeline for evaluation of probe function for detecting bacterial pneumonia in situ11.
To identify suitable probe candidates, the following prerequisites had to be fulfilled prior to interrogation of the probe on ex vivo human lung tissue by FCFM: i) aqueous solubility, ii) specificity and selectivity for rapidly labeling clinically relevant bacteria, iii) a high signal-to-noise ratio, and iv) resistance to degradation within the lung environment. The latter was assessed by bronchoalveolar lavage fluid (BALF) from patients with acute respiratory distress syndrome (ARDS), which is a condition that is characterized by proteolytic and inflammatory environments in the lung in the ICU. Moreover, the probes had to have a suitable fluorophore for detection by a clinically approved optical CLE imaging device within human lung alveolar tissue.
The pipeline to interrogate each of these prerequisites was as follows (at each stage, only probes that passed were carried forward to the next): (1) a library of probes to be investigated was synthesized; (2) each probe was added to a panel of live bacteria for confocal laser scanning microscopy (CLSM) to ensure bacterial labeling; (3) selectivity of bacterial labeling over mammalian cells in co-cultures with primary human neutrophils was established by CLSM; (4) stability and successful labeling of bacteria in the presence of the ARDS patient BALF was determined by CLSM and Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) Mass Spectrometry; (5) optimal concentration of candidates was determined by CLSM, ensuring selectivity for bacteria over mammalian cells was maintained; (6) candidates were imaged by FCFM in suspension and on ex vivo human lung alveolar tissue to ensure stability and that the signal-to-noise was adequate for detection. Step 6 is described in detail within this protocol. Methodology for steps 1&#160;- 5 has been previously reported11.

<table><tbody><tr><td>1-14 Microfuge</td><td>SciQuip</td><td>90616</td><td>Small benchtop microcentrifuge</td></tr><tr><td>96-well plate</td><td>Corning</td><td>3370</td><td>Assay plate</td></tr><tr><td>Calcein AM</td><td>Sigma Aldrich</td><td>17783&amp;nbsp;</td><td>Commercial fluorescent dye</td></tr><tr><td>Cellvizio 488 nm Research CLE</td><td>Mauna Kea Technologies</td><td>LC-0001-488</td><td>Confocal laser endomicroscopy device</td></tr><tr><td>Cletop-S</td><td>Cletop</td><td>14110601</td><td>Fibre cleaner</td></tr><tr><td>Eppendorf (1.5 mL)</td><td>Eppendorf</td><td>30120086</td><td>1.5 mL microfuge tube</td></tr><tr><td>Eppendorf Research Plus Pipettes</td><td>Fisher Scientific</td><td>11568663</td><td>Micro pipettes</td></tr><tr><td>Falcon tube (50 mL)</td><td>Scientific Lab Supplies</td><td>352070</td><td>50 ml centrifugation tube</td></tr><tr><td>Gibco Phosphate Buffered Saline</td><td>Thermo Fisher Scientific</td><td>10010023</td><td>PBS - wash media</td></tr><tr><td>IC-Viewer</td><td>Mauna Kea Technologies</td><td>LW-0001</td><td>Data collection and processing software for the research CellVizio 488 nm system</td></tr><tr><td>Incu-Shake midi</td><td>Sciquip</td><td>SQ-4020</td><td>Floor standing shaking incubator</td></tr><tr><td>Lysogeny Broth&amp;nbsp;</td><td>Sigma Aldrich (Miller)</td><td>L3522</td><td>LB Growth media for S. aureus</td></tr><tr><td>non-standard research AlveoFlex 488 nm</td><td>Mauna Kea Technologies</td><td>MP-0002-AF3</td><td>Fibred confocal fluorescence microscopy fibre</td></tr><tr><td>Quanti Kit 488 nm</td><td>Mauna Kea Technologies</td><td>LQ-0005</td><td>Calibration kit for the CellVizio 488 system</td></tr><tr><td>S. aureus ATCC 25923</td><td>ATCC</td><td>25923</td><td>Bacterial strain used in this study</td></tr><tr><td>Semi-micro spectrophotometry cuvette</td><td>Sigma Aldrich&amp;nbsp;</td><td>C5416-100EA</td><td>For spectrophotometry&amp;nbsp;</td></tr><tr><td>Thermomixer comfort</td><td>Eppendorf</td><td>41102422</td><td>Benchtop heater with shaking</td></tr><tr><td>UV 1101 Biotech photometer</td><td>Biochrom WPA</td><td></td><td>Spectrophotometer</td></tr></tbody></table>

optical screening of novel bacteria-specific probes on ex vivo human lung tissue by confocal laser endomicroscopy

Improving the speed and accuracy of bacterial detection is important for patient stratification and to ensure the appropriate use of antimicrobials. To achieve this goal, the development of diagnostic techniques to recognize bacterial presence in real-time at the point-of-care is required. Optical imaging for direct identification of bacteria within the host is an attractive approach. Several attempts at chemical probe design and validation have been investigated, however none have yet been successfully translated into the clinic. Here we describe a method for ex vivo validation of bacteria-specific probes for identification of bacteria within the distal lung, imaged by fibered confocal fluorescence microscopy (FCFM). Our model used ex vivo human lung tissue and a clinically approved confocal laser endomicroscopy (CLE) platform to screen novel bacteria-specific imaging compounds, closely mimicking imaging conditions expected to be encountered with patients. Therefore, screening compounds by this technique provides confidence of potential clinical tractability.

In this study, we have demonstrated a method for the rapid-screening of novel bacteria-specific probes in an ex vivo human alveolar lung tissue model of infection using a clinically approved CLE device.
CLE by FCFM is well suited for obtaining structural information within the distal lung, as this region (due to a high abundance of elastin and collagen) is naturally highly fluorescent when excited with a 488 nm laser8. Conversely, the alveolar space does not fluoresce, and as such enables high contrast between tissue structure and air space to be visualized (Figure 1).
The addition of disease related probes or contrast agents, such as bacteria-specific probes should enable functional information about disease processes to be obtained in real-time. We have previously described the synthesis and initial in vitro screening of a library of bacteria-specific probes11; where bacterial-specificity, proteolytic stability, and retention within the bacterial membrane over time was determined. A promising bacteria-specific probe (UBI-10) was identified within the study, as well as one that showed poor retention within the bacterial cell membrane (UBI-3). These were compared to a control of commercial counterstaining (Calcein AM) that was used to labeled S. aureus.
Unstained, Calcein AM, UBI-3, and UBI-10 labeled S. aureus were imaged in suspension by FCFM with 100% 488 nm laser power and a frame rate of 12 frames/s (Figure 2). Where unlabeled bacteria in PBS were imaged, no fluorescent signal was detectable. This is in contrast to when labeled bacteria were imaged. Where bacterial suspensions with UBI-3 or UBI-10 were imaged by FCFM, it was apparent that the general background fluorescence of the solution was elevated compared to PBS only controls, this is because NBD (the probe fluorophore) does emit a small amount of fluorescence signal in aqueous solution, however, bright punctate dots are clearly visible throughout the solution, without the need for a wash step. This is due to an increase in fluorescence signal emitted from NDB in a polar environment i.e., the bacterial membrane. Calcein AM is not an activatable probe, so a wash step after bacterial staining was required to remove the high fluorescent background of unbound probe in the solution. Like UBI-3 and UBI-10 labeled bacteria, bacteria labeled with Calcein AM were detected in solution by FCFM as bright green punctate dots. As the data are collected in video format, these dots appear to &#39;twinkle&#39; as they move between cores and in-and-out of focus, a characteristic trait of imaging labeled bacteria by this method.
The labeled bacteria were subsequently added to small slices of ex vivo human lung tissue and imaged again by FCFM (Figure 3). Where only PBS or unlabeled S. aureus was added to the lung tissue, only the lung tissue autofluorescent structure was detected (seen as bright green strands of collagen and elastin and dark areas of alveolar space). No punctate dots were detected for these control conditions. Similarly, only lung tissue structure (and no punctate dots) was visualized for the lung tissue condition with S. aureus plus UBI-3; indicating that this probe was not retained stably within the bacterial cell membrane i.e., it was washed out and/or is degraded in the presence of native proteolytic enzymes within the lung tissue (as previously demonstrated11).
However, bright punctate dots were visible in both the Calcein AM labeled positive control S. aureus sample, and with the most promising bacteria-specific probe (UBI-10) S. aureus sample. The &#39;twinkling&#39; dots were visible despite the strong tissue autofluorescence (Figure 3). Thus, the results obtained by FCFM were in concurrence with the in vitro pre-screening of the panel of bacteria-specific probes by CLSM, and demonstrated a clinically relevant detection method for imaging infections in real-time.
The results presented here demonstrate that the lung is an appropriate organ system for imaging by FCFM due to its distinctive autofluorescence. The bright distinctive structures allow the CLE operator to determine that they are in the alveolar space. These regions, coupled with the dark alveolar air sacs provide the perfect backdrop for imaging fluorescently labeled bacteria with high contrast.
Although the detection of bacteria presented within this study is determined qualitatively by visualizing bright punctate dots, it could be possible to quantify the number of punctate dots frame by frame using a secondary software in order to further characterize probe libraries.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56284/56284fig1.jpg" /> 
Figure 1: Static image of human lung tissue autofluorescence.&#160;Confocal laser endomicroscopy (CLE) image of ex vivo human lung tissue using fibered confocal fluorescence microscopy (FCFM), at 488 nm excitation, 100% laser power, and 12 frames/s. Elastin and collagen are highly fluorescent (false colored green), whereas alveolar space is not, and appears as black regions. This figure has been modified from Akram et al.11 <a href="https://cloudflare.jove.com/files/ftp_upload/56284/56284fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56284/56284fig2.jpg" /> 
Figure 2: Confocal laser endomicroscopy (CLE) image of labeled S. aureus in suspension. Fibered confocal fluorescence microscopy (FCFM) was used to image pre-labeled bacteria, at 488 nm excitation, 100% laser power, and 12 frames/s. Labeled bacteria show as highly fluorescent punctate dots (false colored green). This figure has been modified from Akram et al.11&#160;<a href="https://cloudflare.jove.com/files/ftp_upload/56284/56284fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56284/56284fig3.jpg" /> 
Figure 3: Confocal laser endomicroscopy (CLE) image of ex vivo human lung tissue with labeled S. aureus. Fibered confocal fluorescence microscopy (FCFM) was used to image ex vivo human lung tissue and labeled S. aureus, at 488 nm excitation, 100% laser power, and 12 frames/s. Labeled bacteria show as highly fluorescent punctate dots (false colored green) within the lung tissue sample when labeled with Calcein AM or UBI-10. The highest contrast is observed where bacteria are imaged within the alveolar space. This figure has been modified from Akram et al.11&#160;&#160;<a href="https://cloudflare.jove.com/files/ftp_upload/56284/56284fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Optical Screening of Novel Bacteria-specific Probes on Ex Vivo Human Lung Tissue by Confocal Laser Endomicroscopy at JoVE.com

Optical Screening of Novel Bacteria-specific Probes on Ex Vivo Human Lung Tissue by Confocal Laser Endomicroscopy

This technique describes an efficient screening process for evaluating bacteria-specific optical imaging agents within ex vivo human lung tissue, by fibered confocal fluorescence microscopy for the rapid identification of small molecule chemical probe-candidates with translatable potential.

Optical Screening of Novel Bacteria-specific Probes on Ex Vivo Human Lung Tissue by Confocal Laser Endomicroscopy

Improving the speed and accuracy of bacterial detection is important for patient stratification and to ensure the appropriate use of antimicrobials. To ...

optical-screening-novel-bacteria-specific-probes-on-ex-vivo-human

Research

JoVE Journal

Immunology and Infection

7.4K Views.  University of Edinburgh. Deze techniek beschrijft een efficiënte screeningsproces voor de evaluatie van de bacteriën-specifieke optische beeldvorming agenten binnen ex vivo menselijke longweefsel, door fibered confocal fluorescentie microscopie voor de snelle identificatie van klein molecuul chemische sonde-kandidaten met vertaalbare potentieel.

Video: Optical Screening of Novel Bacteria-specific Probes on Ex Vivo Human Lung Tissue by Confocal Laser Endomicroscopy

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution. Traditionally, multiple experiments are run in parallel, with individual samples removed from the study at sequential time points for evaluation by light microscopy. Several intravital techniques have been developed, with confocal, multiphoton, and second harmonic microscopy all demonstrating their ability to be used for imaging in situ 1. With these systems, however, the required infrastructure is complex and expensive, involving scanning laser systems and complex light sources. Here we present a protocol for the design and assembly of a high-resolution microendoscope which can be built in a day using off-the-shelf components for under US$5,000. The platform offers flexibility in terms of image resolution, field-of-view, and operating wavelength, and we describe how these parameters can be easily modified to meet the specific needs of the end user.
We and others have explored the use of the high-resolution microendoscope (HRME) in in vitro cell culture 2-5, in excised 6 and living animal tissues 2,5, and in human tissues in vivo 2,7. Users have reported the use of several different fluorescent contrast agents, including proflavine 2-4, benzoporphyrin-derivative monoacid ring A (BPD-MA) 5, and fluoroscein 6,7, all of which have received full, or investigational approval from the FDA for use in human subjects. High-resolution microendoscopy, in the form described here, may appeal to a wide range of researchers working in the basic and clinical sciences. The technique offers an effective and economical approach which complements traditional benchtop microscopy, by enabling the user to perform high-resolution, longitudinal imaging in situ.

High-resolution Fiber-optic Microendoscopy for in situ Cellular Imaging

In many biological and clinical situations it is advantageous to study cellular processes as they evolve in their native microenvironment. Here we describe the assembly and use of a low-cost fiber-optic microscope which can provide real time imaging in cell culture, animal studies, and clinical patient studies.

Many biological and clinical studies require the longitudinal study and analysis of morphology and function with cellular level resolution.  ...

Bioengineering

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the tumor microenvironment and respond adequately to tumor antigens. The recent development of improved imaging approaches, such as 2-photon microscopy, and the use of powerful mouse tumor models have shed light on some of the mechanisms that regulate anti-tumor T cell activities. Whereas such systems have provided valuable insights, they do not always predict human responses. In human, our knowledge in the field mainly comes from a description of fixed tumor samples from human patients, as well as in vitro studies. However, in vitro models lack the complex three-dimensional tumor milieu and, therefore, are incomplete approximations of in vivo T cell activities. Fresh slices made from explanted tissue represent a complex multi-cellular tumor environment that can act as an important link between co-cultured studies and animal models. Originally set up in murine lymph nodes1 and previously described in a JoVE article2, this approach has now been transposed to human tumors to examine the dynamics of both plated3&#160;as well as resident&#160;T cells4.
Here, a protocol for the preparation of human lung tumor slices, immunostaining of resident CD8 T and tumor cells, and tracking of CD8 T lymphocytes within the tumor microenvironment using confocal microscopy is described. This system is uniquely placed to screen for novel immunotherapy agents favoring T cell migration in tumors.

Ex Vivo Imaging of Resident CD8 T Lymphocytes in Human Lung Tumor Slices Using Confocal Microscopy

This protocol describes a method to image resident tumor-infiltrating CD8 T cells labeled with fluorescently coupled antibodies within human lung tumor slices. This technique permits real-time analyses of CD8 T cell migration using confocal microscopy.

CD8 T cell are key players in the fight against cancer. In order for CD8 T cells to kill tumor cells they need to enter into the tumor, migrate within the ...

Cancer Research

Video-rate Scanning Confocal Microscopy and Microendoscopy

Confocal microscopy has become an invaluable tool in biology and the biomedical sciences, enabling rapid, high-sensitivity, and high-resolution optical sectioning of complex systems. Confocal microscopy is routinely used, for example, to study specific cellular targets1, monitor dynamics in living cells2-4, and visualize the three dimensional evolution of entire organisms5,6. Extensions of confocal imaging systems, such as confocal microendoscopes, allow for high-resolution imaging in vivo7 and are currently being applied to disease imaging and diagnosis in clinical settings8,9.
Confocal microscopy provides three-dimensional resolution by creating so-called "optical sections" using straightforward geometrical optics. In a standard wide-field microscope, fluorescence generated from a sample is collected by an objective lens and relayed directly to a detector. While acceptable for imaging thin samples, thick samples become blurred by fluorescence generated above and below the objective focal plane. In contrast, confocal microscopy enables virtual, optical sectioning of samples, rejecting out-of-focus light to build high resolution three-dimensional representations of samples.
Confocal microscopes achieve this feat by using a confocal aperture in the detection beam path. The fluorescence collected from a sample by the objective is relayed back through the scanning mirrors and through the primary dichroic mirror, a mirror carefully selected to reflect shorter wavelengths such as the laser excitation beam while passing the longer, Stokes-shifted fluorescence emission. This long-wavelength fluorescence signal is then passed to a pair of lenses on either side of a pinhole that is positioned at a plane exactly conjugate with the focal plane of the objective lens. Photons collected from the focal volume of the object are collimated by the objective lens and are focused by the confocal lenses through the pinhole. Fluorescence generated above or below the focal plane will therefore not be collimated properly, and will not pass through the confocal pinhole1, creating an optical section in which only light from the microscope focus is visible. (Fig 1). Thus the pinhole effectively acts as a virtual aperture in the focal plane, confining the detected emission to only one limited spatial location.
Modern commercial confocal microscopes offer users fully automated operation, making formerly complex imaging procedures relatively straightforward and accessible. Despite the flexibility and power of these systems, commercial confocal microscopes are not well suited for all confocal imaging tasks, such as many in vivo imaging applications. Without the ability to create customized imaging systems to meet their needs, important experiments can remain out of reach to many scientists.
In this article, we provide a step-by-step method for the complete construction of a custom, video-rate confocal imaging system from basic components. The upright microscope will be constructed using a resonant galvanometric mirror to provide the fast scanning axis, while a standard speed resonant galvanometric mirror will scan the slow axis. To create a precise scanned beam in the objective lens focus, these mirrors will be positioned at the so-called telecentric planes using four relay lenses. Confocal detection will be accomplished using a standard, off-the-shelf photomultiplier tube (PMT), and the images will be captured and displayed using a Matrox framegrabber card and the included software.

The complete construction of a custom, real-time confocal scanning imaging system is described. This system, which can be readily used for video-rate microscopy and microendoscopy, allows for an array of imaging geometries and applications not accessible using standard commercial confocal systems, at a fraction of the cost.

Confocal microscopy has become an invaluable tool in biology and the biomedical sciences, enabling rapid, high-sensitivity, and high-resolution optical ...

The Establishment of a Lung Colonization Assay for Circulating Tumor Cell Visualization in Lung Tissues

Metastasis is the major cause of cancer death. The role of circulating tumor cells (CTCs) in promoting cancer metastasis, in which lung colonization by CTCs critically contributes to early lung metastatic processes, has been vigorously investigated. As such, animal models are the only approach that captures the full systemic process of metastasis. Given that problems occur in previous experimental designs for examining the contributions of CTCs to blood vessel extravasation, we established an in vivo lung colonization assay in which a long-term-fluorescence cell-tracer, carboxyfluorescein succinimidyl ester (CFSE), was used to label suspended tumor cells and lung perfusion was performed to clear non-specifically trapped CTCs prior to lung removal, confocal imaging, and quantification. Polymeric fibronectin (polyFN) assembled on CTC surfaces has been found to mediate lung colonization in the final establishment of metastatic tumor tissues. Here, to specifically test the requirement of polyFN assembly on CTCs for lung colonization and extravasation, we performed short term lung colonization assays in which suspended Lewis lung carcinoma cells (LLCs) stably expressing FN-shRNA (shFN) or scramble-shRNA (shScr) and pre-labeled with 20 &#956;M of CFSE were intravenously inoculated into C57BL/6 mice. We successfully demonstrated that the abilities of shFN LLC cells to colonize the mouse lungs were significantly diminished in comparison to shScr LLC cells. Therefore, this short-term methodology may be widely applied to specifically demonstrate the ability of CTCs within the circulation to colonize the lungs.

An animal model is needed to decipher the role of circulating tumor cells (CTCs) in promoting lung colonization during cancer metastasis. Here, we established and successfully performed an in vivo assay to specifically test the requirement of polymeric fibronectin (polyFN) assembly on CTCs for lung colonization.

Metastasis is the major cause of cancer death. The role of circulating tumor cells (CTCs) in promoting cancer metastasis, in which lung colonization by ...

Probe-based Confocal Laser Endomicroscopy of the Urinary Tract: The Technique

Probe-based confocal laser endomicroscopy (CLE) is an emerging optical imaging technology that enables real-time in vivo microscopy of mucosal surfaces during standard endoscopy. With applications currently in the respiratory1 and gastrointestinal tracts,2-6 CLE has also been explored in the urinary tract for bladder cancer diagnosis.7-10 Cellular morphology and tissue microarchitecture can be resolved with micron scale resolution in real time, in addition to dynamic imaging of the normal and pathological vasculature.7
The probe-based CLE system (Cellvizio, Mauna Kea Technologies, France) consists of a reusable fiberoptic imaging probe coupled to a 488 nm laser scanning unit. The imaging probe is inserted in the working channels of standard flexible and rigid endoscopes. An endoscope-based CLE system (Optiscan, Australia), in which the confocal endomicroscopy functionality is integrated onto the endoscope, is also used in the gastrointestinal tract. Given the larger scope diameter, however, application in the urinary tract is currently limited to ex vivo use.11 Confocal image acquisition is done through direct contact of the imaging probe with the target tissue and recorded as video sequences. As in the gastrointestinal tract, endomicroscopy of the urinary tract requires an exogenenous contrast agent&mdash;most commonly fluorescein, which can be administered intravenously or intravesically. Intravesical administration is a well-established method to introduce pharmacological agents locally with minimal systemic toxicity that is unique to the urinary tract. Fluorescein rapidly stains the extracellular matrix and has an established safety profile.12 Imaging probes of various diameters enable compatibility with different caliber endoscopes. To date, 1.4 and 2.6 mm probes have been evaluated with flexible and rigid cystoscopy.10 Recent availability of a &lt; 1 mm imaging probe13 opens up the possibility of CLE in the upper urinary tract during ureteroscopy. Fluorescence cystoscopy (i.e. photodynamic diagnosis) and narrow band imaging are additional endoscope-based optical imaging modalities14 that can be combined with CLE to achieve multimodal imaging of the urinary tract. In the future, CLE may be coupled with molecular contrast agents such as fluorescently labeled peptides15 and antibodies for endoscopic imaging of disease processes with molecular specificity.

Probe-based confocal laser endomicroscopy enables real-time microscopy of the human urinary tract during cystoscopy, providing dynamic, intravital imaging of pathological states such as bladder cancer with cellular resolution. Endomicroscopy may augment the diagnostic accuracy of standard white light endoscopy and provide intraoperative image guidance to improve surgical resection.

Probe-based  confocal laser endomicroscopy (CLE) is an emerging optical imaging technology  that enables real-time in vivo microscopy of mucosal surfaces ...

Medicine

Multimodal Imaging and Spectroscopy Fiber-bundle Microendoscopy Platform for Non-invasive, In Vivo Tissue Analysis

Recent fiber-bundle microendoscopy techniques enable non-invasive analysis of in vivo tissue using either imaging techniques or a combination of spectroscopy techniques. Combining imaging and spectroscopy techniques into a single optical probe may provide a more complete analysis of tissue health. In this article, two dissimilar modalities are combined, high-resolution fluorescence microendoscopy imaging and diffuse reflectance spectroscopy, into a single optical probe. High-resolution fluorescence microendoscopy imaging is a technique used to visualize apical tissue micro-architecture and, although mostly a qualitative technique, has demonstrated effective real-time differentiation between neoplastic and non-neoplastic tissue. Diffuse reflectance spectroscopy is a technique which can extract tissue physiological parameters including local hemoglobin concentration, melanin concentration, and oxygen saturation. This article describes the specifications required to construct the fiber-optic probe, how to build the instrumentation, and then demonstrates the technique on in vivo human skin. This work revealed that tissue micro-architecture, specifically apical skin keratinocytes, can be co-registered with its associated physiological parameters. The instrumentation and fiber-bundle probe presented here can be optimized as either a handheld or endoscopically-compatible device for use in a variety of organ systems. Additional clinical research is needed to test the viability of this technique for different epithelial disease states.

Multimodal Imaging and Spectroscopy Fiber-bundle Microendoscopy Platform for Non-invasive, In Vivo Tissue Analysis

The assembly and use of a multimodal microendoscope is described which can co-register superficial tissue image data with tissue physiological parameters including hemoglobin concentration, melanin concentration, and oxygen saturation. This technique can be useful for evaluating tissue structure and perfusion, and can be optimized for individual needs of the investigator.

Recent fiber-bundle microendoscopy techniques enable non-invasive analysis of in vivo tissue using either imaging techniques or a combination of ...

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular and molecular processes that govern metastatic dissemination and growth are still elusive. Live imaging allows visualization of the dynamic and spatial interactions of cells and their microenvironment. Solid tumors commonly metastasize to the lungs. However, the anatomical location of the lungs poses a challenge to intravital imaging. This protocol provides a relatively simple and quick method for ex vivo live imaging of the dynamic interactions between tumor cells and their surrounding stroma within lung metastasis. Using this method, the motility of cancer cells as well as interactions between cancer cells and stromal cells in their microenvironment can be visualized in real time for several hours. By using transgenic fluorescent reporter mice, a fluorescent cell line, injectable fluorescently labeled molecules and/or antibodies, multiple components of the lung microenvironment can be visualized, such as blood vessels and immune cells. To image the different cell types, a spinning disk confocal microscope that allows long-term continuous imaging with rapid, four-color image acquisition has been used. Time-lapse movies compiled from images collected over multiple positions and focal planes show interactions between live metastatic and immune cells for at least 4 hr. This technique can be further used to test chemotherapy or targeted therapy. Moreover, this method could be adapted for the study of other lung-related pathologies that may affect the lung microenvironment.

Ex vivo Live Imaging of Lung Metastasis and Their Microenvironment

We describe a relatively simple method for ex vivo live imaging of the tumor cell-stroma interactions within lung metastasis, utilizing fluorescent reporters in mice. Using spinning-disk confocal microscopy, this technique enables visualization of live cells for at least 4 hr and could be adapted to study other inflammatory lung conditions.

Metastasis is a major cause for cancer-related morbidity and mortality. Metastasis is a multistep process and due to its complexity, the exact cellular ...

Spatio-Temporal In Vivo Imaging of Ocular Drug Delivery Systems using Fiberoptic Confocal Laser Microendoscopy

Subconjunctival injection is an attractive route to administer ocular drugs due to easy trans-scleral access that bypasses anterior ocular barriers, such as the cornea and conjunctiva. While therapeutic effects and pharmacokinetics of the drugs upon subconjunctival injection have been described in some studies, very few assess the ocular distribution of drugs or drug delivery systems (DDS). The latter is critical for the optimization of intraocular DDS design and drug bioavailability to achieve the desired ocular localization and duration of action (e.g., acute versus. prolonged). This study establishes the use of fiberoptic confocal laser microendoscopy (CLM) to qualitatively study the ocular distribution of fluorescent liposomes in real-time in live mice after sub-conjunctival injection. Being designed for in vivo visual inspection of tissues at the microscopic level, this is also the first full description of the CLM imaging method to study spatio-temporal distribution of injectables in the eye after subconjunctival injection.

Spatio-Temporal In Vivo Imaging of Ocular Drug Delivery Systems using Fiberoptic Confocal Laser Microendoscopy

We present a protocol for the use of fiberoptic confocal laser microendoscopy (CLM) to non-invasively study the spatio-temporal distribution of liposomes in the eye after subconjunctival injection.

Subconjunctival injection is an attractive route to administer ocular drugs due to easy trans-scleral access that bypasses anterior ocular barriers, such ...

Confocal Laser Scanning Microscopy-Based Quantitative Analysis of Aspergillus fumigatus Conidia Distribution in Whole-Mount Optically Cleared Mouse Lung

Aspergillus fumigatus conidia are airborne pathogens that can penetrate human airways. Immunocompetent people without allergies exhibit resistance and immunological tolerance, while in immunocompromised patients, conidia can colonize airways and cause severe invasive respiratory disorders. Various cells in different airway compartments are involved in the immune response that prevents fungal invasion; however, the spatio-temporal aspects of pathogen elimination are still not completely understood. Three-dimensional (3D) imaging of optically cleared whole-mount organs, particularly the lungs of experimental mice, permits detection of fluorescently labeled pathogens in the airways at different time points after infection. In the present study, we describe an experimental setup to perform a quantitative analysis of A. fumigatus conidia distribution in the airways. Using fluorescent confocal laser scanning microscopy (CLSM), we traced the location of fluorescently labeled&#160;conidia in the bronchial branches and the alveolar compartment 6 hours after oropharyngeal application to mice. The approach described here was previously used for detection of the precise pathogen location and identification of the pathogen-interacting cells at different phases of the immune response. The experimental setup can be used to estimate the kinetics of the pathogen elimination in different pathological conditions.

Confocal Laser Scanning Microscopy-Based Quantitative Analysis of Aspergillus fumigatus Conidia Distribution in Whole-Mount Optically Cleared Mouse Lung

We describe the method for quantitative analysis of the distribution of Aspergillus fumigatus conidia (3 &#181;m in size) in the airways of mice. The method also can be used for the analysis of microparticles and nanoparticle agglomerate distribution in the airways in various pathological condition models.

Aspergillus fumigatus conidia are airborne pathogens that can penetrate human airways. Immunocompetent people without allergies exhibit resistance and ...

Advanced Imaging of Lung Homing Human Lymphocytes in an Experimental In Vivo Model of Allergic Inflammation Based on Light-sheet Microscopy

Overwhelming tissue accumulation of highly activated immune cells represents a hallmark of various chronic inflammatory diseases and emerged as an attractive therapeutic target in the clinical management of affected patients. In order to further optimize strategies aiming at therapeutic regulation of pathologically imbalanced tissue infiltration of pro-inflammatory immune cells, it will be of particular importance to achieve improved insights into disease- and organ-specific homing properties of peripheral lymphocytes. The here described experimental protocol allows to monitor lung accumulation of fluorescently labeled and adoptively transferred human lymphocytes in the context of papain-induced pulmonary inflammation. In contrast to standard in vitro assays frequently used for the analysis of immune cell migration and chemotaxis, the now introduced in vivo setting takes into account lung-specific aspects of tissue organization and the influence of the complex inflammatory scenario taking place in the living murine organism. Moreover, three-dimensional cross-sectional light-sheet fluorescence microscopic imaging does not only provide quantitative data on infiltrating immune cells, but also depicts the pattern of immune cell localization within the inflamed lung. Overall, we are able to introduce an innovative technique of high value for immunological research in the field of chronic inflammatory lung diseases, which can be easily applied by following the provided step-by-step protocol.

The here introduced protocol allows characterization of the lung homing capacity of primary human lymphocytes under in vivo inflammatory conditions. Pulmonary infiltration of adoptively transferred human immune cells in a mouse model of allergic inflammation can be imaged and quantified by light-sheet fluorescence microscopy of chemically cleared lung tissue.

Optical Screening of Novel Bacteria-specific Probes on Ex Vivo Human Lung Tissue by Confocal Laser Endomicroscopy

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