Name: highly-multiplexed tissue imaging with raman dyes
Uploaded: 2022-04-21T12:50:00
Description: Watch this Scientific Journal Video about Highly-Multiplexed Tissue Imaging with Raman Dyes at JoVE.com

We thank Ruth A. Singer and Richard K.P. Benninger for providing mouse pancreas tissues. W.M. acknowledges support from NIH R01 (GM128214), R01 (GM132860), R01 (EB029523) and US Army (W911NF-19-1-0214).

The protocol was conducted in accordance with the animal experimental protocol (AC-AABD1552) approved by the Institutional Animal Care and Use Committee at Columbia University.
1. Preparation of Raman-dye-conjugated antibodies
<ol>
	<li>Prepare the conjugation buffer as ~0.1 M NaHCO3 in PBS buffer, pH = 8.3, store at 4 &#176;C.</li>
	<li>Prepare N-hydroxysuccinimidy (NHS) ester-functionated MARS probe (Supplementary Material) solution as 3 mM in a...

<ol>
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K. P., Hodson, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+understanding+of+&#946;-cell+heterogeneity+and+in+situ+islet+function.">New understanding of &#946;-cell heterogeneity and in situ islet function.</a> Diabetes. 67 (4), 537 (2018).</li><li>Hu, F., 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=Supermultiplexed+optical+imaging+and+barcoding+with+engineered+polyynes.">Supermultiplexed optical imaging and barcoding with engineered polyynes.</a> Nature Methods. 15 (3), 194-200 (2018).</li><li>Hu, F., Shi, L., Min, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biological+imaging+of+chemical+bonds+by+stimulated+Raman+scattering+microscopy.">Biological imaging of chemical bonds by stimulated Raman scattering microscopy.</a> Nature Methods. 16 (9), 830-842 (2019).</li><li>. 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Here, we present the immuno-eprSRS protocol which is broadly applicable to common tissue types, including freshly-preserved mouse tissues, FFPE human tissues, and frozen mouse tissues. Immuno-eprSRS has been validated for a panel of epitopes in cells and tissues, as listed in Table 1. This one-shot platform is particularly suitable for applications where cyclic strategies do not function well. For example, cyclic fluorescence is demanding for thick tissues as multiple rounds of 3D immunolabeling are unpr...

Complex tissue systems are composed of distinct cellular subpopulations whose spatial locations and interaction networks are deeply intertwined with their functions and dysfunctions1,2. To reveal the tissue architecture and interrogate its complexity, knowledge of the spatial locations of proteins at single-cell resolution is essential. Hence, highly multiplexed protein-imaging technologies have been increasingly appreciated and could become a cornerstone for studying tissue biology3,4,5. Current common multiplexed protein imaging methods can be classified into two main categories. One is serial immunofluorescence imaging relying on multiple rounds of tissue staining and imaging, and the other is imaging mass cytometry coupled with heavy metal tagged antibodies6,7,8,9,10,11,12.
Here, an alternative strategy for multiplexed antibody-based protein imaging is introduced. Unlike the prevalent fluorescence imaging modality, which can only visualize 4-5 channels simultaneously due to the broad excitation and emission spectra (full width at half maximum (FWHM) ~500 cm-1), Raman microscopy exhibits much narrower spectral linewidth (FWHM ~10 cm-1) and hence provides scalable multiplexity. Recently, by harnessing the narrow spectrum, a novel scheme of Raman microscopy named electronic pre-resonance stimulated Raman scattering (epr-SRS) microscopy has been developed, providing a powerful strategy for multiplexed imaging13. By probing the electronically coupled vibrational modes of Raman dyes, epr-SRS achieves a drastic enhancement effect of 1013-fold on Raman cross-sections and overcomes the sensitivity bottleneck of conventional Raman microscopy (Figure 1A)13,14,15. As a result, the detection limit of epr-SRS has been pushed to sub-&#181;M, which enables Raman detection of interesting molecular markers such as specific proteins and organelles inside cells13,16. In particular, utilizing Raman dye-conjugated antibodies, epr-SRS imaging of specific proteins in cells and tissues (called immuno-eprSRS) was demonstrated with comparable sensitivity to standard immunofluorescence (Figure 1B)13,17. By tuning the pump wavelength by only 2 nm, the epr-SRS signal will be completely off (Figure 1B), which showcases high vibrational contrast.
On the probe side, a set of rainbow-like Raman probes called Manhattan Raman scattering (MARS) dyes has been developed for antibody conjugation13,18,19,20. This unique Raman palette consists of novel dyes bearing &#960;-conjugated triple bonds (Supplementary Material), each displaying a single and narrow epr-SRS peak in the bioorthogonal Raman spectral range (Figure 1C). By modifying the structure of the core chromophore and isotopically editing both atoms of the triple bond (Supplementary Material), spectrally separated Raman probes have been developed. Leveraging the scalable multiplexity, epr-SRS microscopy coupled with the MARS dye palette offers an optical strategy for one-shot multiplex protein imaging in cells and tissues.
Immuno-eprSRS provides an alternative strategy to current multiplex protein imaging methods with unique strengths. Compared to fluorescence approaches with cyclic staining, imaging, and signal removal, this Raman-based platform ensures single-round staining and imaging. Therefore, it circumvents practical complexity in cyclic procedures and largely simplifies the protocol, hence opening new territories of multiplexed protein imaging. For instance, harnessing a Raman-dye-tailored tissue clearing protocol, immuno-eprSRS has been extended to three dimensions for highly multiplexed protein mapping in thick intact tissues17. Over 10 protein targets were visualized along millimeter-thick mouse brain tissues17. More recently, coupling immuno-eprSRS with an optimized biomolecule-retention expansion microscopy (ExM) protocol21, one-shot nanoscale imaging of multiple targets has also been demonstrated22. Compared to imaging mass spectroscopy4,9, epr-SRS is nondestructive and has intrinsically optical sectioning ability. Furthermore, epr-SRS is more time-efficient on tissue scanning. Typically, a tissue region of 0.25 mm2 with a pixel size of 0.5 &#181;m takes merely a few minutes to image for a single epr-SRS channel. For example, the total imaging time of four SRS channels plus four fluorescence channels in Figure 4 is about 10 min.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>16% Paraformaldehyde, EM Grade</td>
			<td>Electron Microscopy Sciences</td>
			<td>15710</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-tubulin</td>
			<td>Abcam</td>
			<td>ab18251</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>&#945;-tubulin</td>
			<td>BioLegend</td>
			<td>625902</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>&#946;-III-tubulin</td>
			<td>BioLegend</td>
			<td>657402</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>&#946;-III-tubulin</td>
			<td>Abcam</td>
			<td>ab41489</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>&#946;-tubulin</td>
			<td>Abcam</td>
			<td>ab131205</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Agarose, low gellling temperature</td>
			<td>Sigma Aldrich</td>
			<td>A9414</td>
			<td>For brain embedding</td>
		</tr>
		<tr>
			<td>Anti-a-tubulin antibody produced in rabbit (&#945;-tubulin)</td>
			<td>Abcam</td>
			<td>ab52866</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Calbindin antibody produced in mouse (Calbindin)</td>
			<td>Abcam</td>
			<td>ab82812</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-GABA B receptor R2&#160; antibody produced in guinea pig (GABA B receptor R2)</td>
			<td>Millipore Sigma</td>
			<td>AB2255</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-GFAP antibody produced in goat (GFAP)</td>
			<td>Thermo Scientific</td>
			<td>PA5-18598</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Glucagon&#160; antibody produced in mouse (Glucagon)</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-514592</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-insulin antibody produced in guinea pig (insulin)</td>
			<td>DAKO</td>
			<td>IR00261-2</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-MBP antibody produced in rat (MBP)</td>
			<td>Abcam</td>
			<td>ab7349</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-NeuN antibody produced in rabbit (NeuN)</td>
			<td>Thermo Scientific</td>
			<td>PA5-78639</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Pancreatic polypeptide (PP) antibody produced in goat- Pancreatic polypeptide (PP)</td>
			<td>Sigma Aldrich</td>
			<td>SAB2500747</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Pdx1 antibody produced in rabbit (Pdx1)</td>
			<td>Milipore</td>
			<td>06-1379</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Somatostatin antibody produced in rat (Somatostatin)</td>
			<td>Abcam</td>
			<td>ab30788</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Anti-Vimentin antibody produced in chicken (Vimentin)</td>
			<td>Abcam</td>
			<td>ab24525</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Band-pass filter</td>
			<td>KR Electronics</td>
			<td>KR2724</td>
			<td>8 MHz</td>
		</tr>
		<tr>
			<td>BNC 50 Ohm Terminator</td>
			<td>Mini Circuits</td>
			<td>STRM-50</td>
			<td></td>
		</tr>
		<tr>
			<td>BNC cable</td>
			<td>Thorlabs</td>
			<td>2249-C</td>
			<td>Coaxial Cable, BNC Male / Male</td>
		</tr>
		<tr>
			<td>Broadband dielectric mirror</td>
			<td>Thorlabs</td>
			<td>BB1-E03</td>
			<td>750 - 1100 nm</td>
		</tr>
		<tr>
			<td>C57BL/6J mice</td>
			<td>Jackson Laboratory</td>
			<td>000664</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Condenser</td>
			<td>Olympus</td>
			<td></td>
			<td>oil immersion, 1.4 N.A.</td>
		</tr>
		<tr>
			<td>Cytokeratin 18</td>
			<td>Abcam</td>
			<td>ab7797</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Cytokeratin 18</td>
			<td>Abcam</td>
			<td>ab24561</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>DC power supply</td>
			<td>TopWard</td>
			<td>6302D</td>
			<td>Bias voltage is 64 V</td>
		</tr>
		<tr>
			<td>Dichroic mount</td>
			<td>Thorlabs</td>
			<td>KM100CL</td>
			<td>Kinematic Mount for up to 1.3&#34; (33 mm) Tall Rectangular Optics, Left Handed</td>
		</tr>
		<tr>
			<td>Donkey anti-Chicken IgY (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>703-005-155</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Goat IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>705-005-147</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Guinea Pig IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>706-005-148</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Mouse IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>715-005-151</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Rabbit IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>711-005-152</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Rat IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>712-005-153</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>Donkey anti-Sheep IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>713-005-147</td>
			<td>Secondary antibodies for MARS conjugation</td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>Fisher Scientific</td>
			<td>14-190-250</td>
			<td></td>
		</tr>
		<tr>
			<td>EpCAM</td>
			<td>Abcam</td>
			<td>ab71916</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma Aldrich</td>
			<td>443611</td>
			<td></td>
		</tr>
		<tr>
			<td>Fast-speed look-in amplifier</td>
			<td>Zurich Instruments</td>
			<td>HF2LI</td>
			<td>DC - 50 MHz</td>
		</tr>
		<tr>
			<td>FFPE Kidney Sample</td>
			<td>USBiomax</td>
			<td>HuFPT072</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibrillarin</td>
			<td>Abcam</td>
			<td>ab5821</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Giantin</td>
			<td>Abcam</td>
			<td>ab24586</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Glucagon</td>
			<td>Santa Cruz Biotechnology</td>
			<td>sc-514592</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>H2B</td>
			<td>Abcam</td>
			<td>ab1790</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>HeLa</td>
			<td>ATCC</td>
			<td>ATCC CCL-2</td>
			<td></td>
		</tr>
		<tr>
			<td>High O.D. bandpass filter</td>
			<td>Chroma Technology</td>
			<td>ET890/220m</td>
			<td>Filter the Stokes beam and transmit the pump beam</td>
		</tr>
		<tr>
			<td>Hydrophobic pen</td>
			<td>Fisher Scientific</td>
			<td>NC1384846</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>ThermoFisher</td>
			<td>701265</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Integrated SRS laser system</td>
			<td>Applied Physics &#38; Electronics, Inc.</td>
			<td>picoEMERALD</td>
			<td>picoEMERALD provides an output pulse train at 1,064 nm with 6-ps pulse width and 80-MHz repetition rate, which serves as the Stokes beam. The frequency doubled beam at 532 nm is used to synchronously seed a picosecond optical parametric oscillator (OPO) to produce a mode-locked pulse train with five~6 ps pulse width (the idler beam of the OPO is blocked with an interferometric filter). The output wavelength of the OPO is tunable from 720&#8211;950 nm, which serves as the pump beam. The intensity of the 1,064-nm Stokes beam is modulated sinusoidally by a built-in EOM at 8 MHz with a modulation depth of more than 90%. The pump beam is spatially overlapped with the Stokes beam by using a dichroic mirror inside picoEMERALD. The temporal overlap between pump and Stokes pulse trains is achieved with a built-in delay stage and optimized by the SRS signal of pure D2O at the microscope.</td>
		</tr>
		<tr>
			<td>Inverted laser-scanning microscope</td>
			<td>Olympus</td>
			<td>FV1200MPE</td>
			<td></td>
		</tr>
		<tr>
			<td>Kinematic mirror mount</td>
			<td>Thorlabs</td>
			<td>POLARIS-K1-2AH</td>
			<td>2 Low-Profile Hex Adjusters</td>
		</tr>
		<tr>
			<td>Lectin from Triticum vulgaris (wheat)</td>
			<td>Sigma Aldrich</td>
			<td>L0636-5 mg</td>
			<td></td>
		</tr>
		<tr>
			<td>Long-pass dichroic beam splitter</td>
			<td>Semrock</td>
			<td>Di02-R980-25x36</td>
			<td>980 nm laser BrightLine&#160;single-edge laser-flat dichroic beamsplitter</td>
		</tr>
		<tr>
			<td>MAP2</td>
			<td>BioLegend</td>
			<td>801810</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Microscopy imaging software</td>
			<td>Olympus</td>
			<td>FluoView</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoQuant Plate</td>
			<td>Tecan</td>
			<td></td>
			<td>For absorbance-based, small volume analyses in a plate reader.</td>
		</tr>
		<tr>
			<td>Normal donkey serum</td>
			<td>Jackson ImmunoResearch</td>
			<td>017-000-121</td>
			<td></td>
		</tr>
		<tr>
			<td>NucBlue Fixed Cell ReadyProbes Reagent (DAPI)</td>
			<td>Thermo Scientific</td>
			<td>R37606</td>
			<td></td>
		</tr>
		<tr>
			<td>Nunc 4-Well Dishes</td>
			<td>Fisher Scientific</td>
			<td>12-566-300</td>
			<td></td>
		</tr>
		<tr>
			<td>Objective lens</td>
			<td>Olympus</td>
			<td>XLPlan N</td>
			<td>x25, 1.05-NA, MP, working distance&#8201;=&#8201;2&#8201;mm</td>
		</tr>
		<tr>
			<td>Paint brush</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Periscope assembly</td>
			<td>Thorlabs</td>
			<td>RS99</td>
			<td>includes the top and bottom units, &#216;1&#34; post, and clamping fork.</td>
		</tr>
		<tr>
			<td>pH meter</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Plate reader</td>
			<td>Tecan</td>
			<td>Infinite 200 PRO</td>
			<td>An easy-to-use multimode plate reader. Absorbance measurement capabilities over a spectral range of 230&#8211;1000 nm.</td>
		</tr>
		<tr>
			<td>ProLong Gold antifade reagent</td>
			<td>Thermo Scientific</td>
			<td>P36930</td>
			<td></td>
		</tr>
		<tr>
			<td>PSD95</td>
			<td>Invitrogen</td>
			<td>51-6900</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Sephadex G-25 Medium</td>
			<td>GE Life Sciences</td>
			<td>17-0033-01</td>
			<td>gel filtration resin for desalting and buffer exchange</td>
		</tr>
		<tr>
			<td>Shielded box with BNC connectors</td>
			<td>Pomona Electronics</td>
			<td>2902</td>
			<td>Aluminum Box With Cover, BNC Female/Female</td>
		</tr>
		<tr>
			<td>Si photodiode</td>
			<td>Thorlabs</td>
			<td>FDS1010</td>
			<td>350&#8211;1100 nm, 10 mm x 10 mm Active Area</td>
		</tr>
		<tr>
			<td>Synapsin 2</td>
			<td>ThermoFisher</td>
			<td>OSS00073G</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Tissue Path Superfrost Plus Gold Slides</td>
			<td>Fisher Scientific</td>
			<td>22-035813</td>
			<td>Adhesive slide to attract and chemically bond fresh or formalin-fixed tissue sections firmly to the slide surface (tiisue bindling glass slides)</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Fisher Scientific</td>
			<td>BP151-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibratome</td>
			<td>Leica</td>
			<td>VT1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Vimentin</td>
			<td>Abcam</td>
			<td>ab8069</td>
			<td>Primary antibodies</td>
		</tr>
		<tr>
			<td>Xylenes</td>
			<td>Sigma Aldrich</td>
			<td>214736</td>
			<td></td>
		</tr>
	</tbody>
</table>

highly-multiplexed tissue imaging with raman dyes

Visualizing a vast scope of specific biomarkers in tissues plays a vital role in exploring the intricate organizations of complex biological systems. Hence, highly multiplexed imaging technologies have been increasingly appreciated. Here, we describe an emerging platform of highly-multiplexed vibrational imaging of specific proteins with comparable sensitivity to standard immunofluorescence via electronic pre-resonance stimulated Raman scattering (epr-SRS) imaging of rainbow-like Raman dyes. This method circumvents the limit of spectrally-resolvable channels in conventional immunofluorescence and provides a one-shot optical approach to interrogate multiple markers in tissues with subcellular resolution. It is generally compatible with standard tissue preparations, including paraformaldehyde-fixed tissues, frozen tissues, and formalin-fixed paraffin-embedded (FFPE) human tissues. We envisage this platform will provide a more comprehensive picture of protein interactions of biological specimens, particularly for thick intact tissues. This protocol provides the workflow from antibody preparation to tissue sample staining, to SRS microscope assembly, to epr-SRS tissue imaging.

Figure 3&#160;shows example images of epr-SRS in different samples, including fixed cells (Figure 3A), paraformaldehyde (PFA)-fixed mouse tissues (Figure 3B), and formalin-fixed paraffin-embedded (FFPE) human specimens (Figure 3C). The spatial resolution of SRS microscopy is diffraction-limited, the typical lateral resolution is ~300 nm, and the axial resolution is 1-2 &#181;m using near-infrared light ...

Watch this Scientific Journal Video about Highly-Multiplexed Tissue Imaging with Raman Dyes at JoVE.com

Highly-Multiplexed Tissue Imaging with Raman Dyes

Electronic pre-resonance stimulated Raman scattering (epr-SRS) imaging of rainbow-like Raman dyes is a new platform for highly multiplexed epitope-based protein imaging. Here, we present a practical guide including antibody preparation, tissue sample staining, SRS microscope assembly, and epr-SRS tissue imaging.

Visualizing a vast scope of specific biomarkers in tissues plays a vital role in exploring the intricate organizations of complex biological systems. ...

Highly-multiplexed vibrational imaging provides a one-shot optical approach to interrogate multiple protein markers in tissues with subcellular resolution. This platform provides a comprehensive picture of protein interactions of biological systems. The main advantage of this technique is its cycle-free multiplexity.This technique is particularly suitable for applications where cycling strategies do not function well, such as in thick tissue sections. This method enables individual cell characterization in situ for understanding structures of the complex system, such as building tissue atlas, phenotyping tumor micro environments, and the profiling brain circuit. To begin, prepare approximately 0.1 molar sodium bicarbonate in PBS buffer at PHA 0.3 to be used as conjugation buffer and store it at four degrees Celsius.Then prepare three millimolar n-hydroxysuccinimide ester functionated MARS probe solution in anhydrous dimethyl sulfoxide. Dissolve the antibody solids in the conjugation buffer to a concentration of two milligrams per milliliter. For antibodies dissolved in other buffers, concentrate them in a centrifugal filter and then add into the conjugation buffer to a concentration of one to two milligrams per milliliter.To perform the conjugation reaction for secondary antibodies, add 15-fold molar excess of dye solution to the antibodies solution in a glass vial slowly with stirring and incubate the reaction mixture at room temperature with stirring for one hour. To perform the purification, prepare the slurry by adding 10 milliliters of gel filtration resin powder into 40 milliliters of PBS buffer in a 50 milliliter tube. Keep the solution in a water bath at 90 degrees Celsius for one hour.Then decant the supernatant, add the PBS up to 40 milliliters, and store the slurry at four degrees Celsius. Pack the size exclusion column with the slurry solution to the height of 10 to 15 centimeters, then rinse and wash the column with approximately 10 milliliters of PBS to further pack the resin. Subsequently, pipette the conjugation reaction mixture to the column.After loading the reaction mixture, immediately add one milliliter of PBS as the elution buffer. Afterward, collect the eluent of the conjugate solution by looking at the color on the column or by measuring the absorbance at 280 nanometers. Using the centrifugal filter, concentrate the collected solution to one to two milligrams per milliliter.Using a hydrophobic pen, draw a boundary around the tissue sections on the slide. Then incubate the tissues with 0.3 to 0.5%PBST for 10 minutes and a blocking buffer for 30 minutes. To prepare the primary staining solution, add all primary antibodies to 200 to 500 microliters of staining buffer at desired concentrations.Centrifuge the primary staining solution at 13, 000 times G for five minutes and use the supernatant if precipitate appears. Then incubate the tissue in the primary antibody solution at four degrees Celsius for one to two days. Wash the slides thrice with 0.3 to 0.5%PBST for five minutes at room temperature in a slide standing jar and make sure that the tissues are immersed in the solution.Later, incubate the tissue in 200 to 500 microliters of blocking buffer for 30 minutes. To prepare the secondary staining solution, add all secondary antibodies to 200 to 500 milliliters of staining buffer with desired concentrations. Then centrifuge the secondary staining solution at 13, 000 times G for five minutes and use the supernatant if precipitate appears.Next, incubate the tissues in 200 to 500 microliters of secondary antibody solution at four degrees Celsius for one to two days. Then wash the slides twice with 0.3 to 0.5%PBST at room temperature for five minutes each. Further, incubate with 200 to 500 microliters of DAPI solution for 30 minutes.Again, wash the slides thrice with PBS at room temperature for five minutes each and transfer the floating tissue sections to the glass slides with the glass dropping pipette. Spread the tissue with a tissue brush and clean the surrounding with wipes if needed. Subsequently, mount the tissue in a drop of anti-fade reagents with a glass coverslip and secure it with nail polish.To perform multichannel-eprSRS imaging, set the laser power of the pump beam to 10 to 40 milliwatt and the stokes beam to 40 to 80 milliwatt on the laser control panel. Then set the pixel dwell time to two to four microseconds and use multiple frames averaging typically 10 to 20 frames on the microscopy software. Further, set the time constants of the lock-in amplifier to half of the pixel dwell time.Raman dye imaging of distinct protein markers and HeLa cells paraformaldehyde-fixed mouse brain cortex and humid kidney FFPE tissue were performed through immuno labeling. The immuno-eprSRS imaging of HeLa cells with an alpha-tubulin revealed fine subcellular structures such as microtubules. The eprSRS imaging of MARS 2145 stained astrocytes and MARS 2228 stained cerebellar granule neurons in mouse brain tissue demonstrated three-dimensional patterns with subcellular resolution.The seven-color SRS fluorescence tandem imaging of hormones and transcription factors on frozen mouse islet tissue was performed. The obtained images revealed a good contrast and correct patterns. The eight-color SRS fluorescence tandem imaging of cell type markers on paraformaldehyde-fixed mouse cerebellum tissues was performed.Different types of cells were identified such as cerebellar granule neurons, Purkinje neurons, astrocytes, oligodendrocytes, and GABAergic neurons. This procedure can be further combined with tissue clearing to perform highly multiplexed protein imaging in thick intact tissues. Our group has developed a Raman-dye-tailored tissue clearing protocol for it.

Research

JoVE Journal

Bioengineering

Rejection of Fluorescence Background in Resonance and Spontaneous Raman Microspectroscopy

Raman spectroscopy is often plagued by a strong fluorescent background, particularly for biological samples. If a sample is excited with a train of ...

Non-contact, Label-free Monitoring of Cells and Extracellular Matrix using Raman Spectroscopy

Non-destructive, non-contact and label-free technologies to monitor cell and tissue cultures are needed in the field of biomedical research.1-5 However, ...

Protocol for Relative Hydrodynamic Assessment of Tri-leaflet Polymer Valves

Limitations of currently available prosthetic valves, xenografts, and homografts have prompted a recent resurgence of developments in the area of ...

Sensing of Barrier Tissue Disruption with an Organic Electrochemical Transistor

The gastrointestinal tract is an example of barrier tissue that provides a physical barrier against entry of pathogens and toxins, while allowing the ...

Long-term Intravital Immunofluorescence Imaging of Tissue Matrix Components with Epifluorescence and Two-photon Microscopy

Besides being a physical scaffold to maintain tissue morphology, the extracellular matrix (ECM) is actively involved in regulating cell and tissue ...

Universal Hand-held Three-dimensional Optoacoustic Imaging Probe for Deep Tissue Human Angiography and Functional Preclinical Studies in Real Time

The exclusive combination of high optical contrast and excellent spatial resolution makes optoacoustics (photoacoustics) ideal for simultaneously ...

Perfusable Vascular Network with a Tissue Model in a Microfluidic Device

A spheroid (a multicellular aggregate) is regarded as a good model of living tissues in the human body. Despite the significant advancement in the ...

Conducting Multiple Imaging Modes with One Fluorescence Microscope

Fluorescence microscopy is a powerful tool to detect biological molecules in situ and monitor their dynamics and interactions in real-time. In addition to ...

Establishing Single-Cell Based Co-Cultures in a Deterministic Manner with a Microfluidic Chip

Cell co-culture assays have been widely used for studying cell-cell interactions between different cell types to better understand the biology of diseases ...

Blood Flow Imaging with Ultrafast Doppler

The pulsed-Doppler effect is the main technique used in clinical echography to assess blood flow. Applied with conventional focused ultrasound Doppler ...