This work was supported by the Princess Margaret Hospital Foundation, the National Science and Engineering Research Council of Canada, the Canadian Institute for Health Research, the Canadian Foundation of Innovation, and the Joey and Toby Tanenbaum/Brazilian Ball Chair in Prostate Cancer Research, a grant from the SUNY Research Foundation and startup support from University at Buffalo.

1. Synthesis of Pyropheophorbide-lipid
<ol>
	<li>Combine 200 mmol pyropheophorbide (prepared from Spirulina Pacifica algae as described previously; Zheng et al., Bioconj. Chem., 2002, 13-392)4, 98.7 mg 16:0 lysophophatidylcholine (1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine, Avanti Polar Lipids #855675), 76.3 mg of EDC , 48.7 mg DMAP (4-(dimethylamino)pyridine) in 5 ml amylene stabilized chloroform for a ratio of 1:1:2:2 Pyro:Lipid:EDC:DMPA.</li>
	<li>Stir the reaction mixture at room temperature under argon for 24 hr. Evaporate the chloroform under reduced pressure using a rotary evaporator with heating to 40 &#176;C. The mixture of pyro-lipid isomers (pyro attached at the sn-1 or sn-2 position) is produced.</li>
	<li>Resuspend pyro-lipid isomer mixture in 1 mM CaCl2, 50 mM Tris (pH 8), 0.5% Triton X-100 and 10% methanol at the concentration of 5 mg/ml. Add phospholipase A2 (PLA2) from honey bee venom at 0.1 mg/ml concentration and incubate the solution at 37 &#176;C for 24 hr to digest sn-1 pyro-lipid and to produce the pure sn-2 pyro-lipid isomer.</li>
	<li>Add additional 2 volumes of chloroform and 1.25 volumes of methanol, extract, and then remove the solvent using rotary evaporation at reduced pressure at 40 &#176;C. Resuspend the cleavage product in 1% MeOH in DCM and purify over a small diol silica column for the isomerically pure pyro-lipid.</li>
</ol>
2. Preparation of Porphysomes
<ol>
	<li>Dissolve pyropheophorbide-lipid, distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy (polyethylene glycol) (PEG-2000-PE) and cholesterol in chloroform separately, and record the concentrations respectively.</li>
	<li>Prepare porphysome lipid film in a 12x75 mm borosilicate test tube with a total lipid weight of 5 mg/tube by combining 65 molar % porphyrin-lipid, 5 molar % PEG-2000-PE and 30 molar % cholesterol.</li>
	<li>Dry the lipid films under a stream of nitrogen gas and let them further dried under vacuum for 1 hr. Store the lipid films at -20 &#176;C under argon until future hydration and extrusion.</li>
	<li>Add 1 ml phosphate buffered saline (PBS, 150 mM NaCl, 10 mM phosphate, pH 7.4) to each lipid film tube. Freeze the test tube in liquid nitrogen until completely frozen, and then thaw the tube in 65 &#176;C water bath until the sample has all melted. Vortex the tube for a total of 30 sec (3x at 10 sec each, with 5 sec re-heating in 65 &#176;C water bath between each vortexing).</li>
	<li>Repeat the freeze-thaw for 5 cycles or more upon needed until no large aggregates can be observed in the hydrated solution. Leave the porphysome suspension on ice when done.</li>
	<li>Assemble the high pressure extruder (10 ml) with two stacked 100 nm polycarbonate filters installed in. Connect the thermobarrel extruder to a thermostatted circulator for 65 &#176;C circulating water bath, and connect the extruder system to a nitrogen tank for high pressure supply.</li>
	<li>Transfer the porphysome suspension to the extruder chamber using a 9 inch glass transfer pipette. Set the pressure by turning the dial on the nitrogen tank regulator until a reading between 200 and 300 psig is observed as initial extrusion pressure. Open the valve of the pressure regulator gradually until sufficient porphysome flow rate is achieved or a maximum of 800 psig (5,440 kPa) of pressure is reached.</li>
	<li>After the first extrusion pass is complete, close the pressure control valve and release the pressure of the extruder by opening the pressure relief valve on the extruder top. Refill the extruder with the freshly extruded porphysome solution, and repeat the extrusion for at least 10 times to ensure the final extruded solution is homogeneous.</li>
	<li>Determine the concentration of final porphysome solution by measuring the absorption of a diluted sample in methanol by UV-Vis spectrometer. Calculate the concentration using the following equation with the extinction coefficient of 97,000 M-1cm-1 at 410 nm for pyropheophorbide-lipid.</li>
</ol>
<img alt="Equation 1" src="/files/ftp_upload/50536/50536eq1.jpg" />
<ol start="10">
	<li>Measure the final size distribution of porphysomes using a Malvern Zetasizer ZS90 by dynamic light scattering. Dilute porphysome solution in PBS and perform three measurements with 15 runs each for the averaged results.</li>
	<li>Determine the fluorescence quenching of porphysome by comparing the fluorescence emission of quenched porphysome (1 mM in PBS) and unquenched porphysome (1 mM in 1% Triton X-100) using Spectrofluorometer. Take the spectra before and after the detergent (Tirton X-100) is added, and normalize the signal reading to maximum fluorescence. Set the excitation to be 410 nm, and emission wavelength range to be 600-800 nm.</li>
	<li>Keep porphysomes solution under argon at 4 &#176;C until future use, and protect it from light by aluminum foil.</li>
</ol>
3. Preparation of Animal Xenograft Model
<ol>
	<li>Culture the KB cells in RPMI-1640 (with 10% FBS), and sustain the cells in 5% CO2 and moisturized atmosphere at 37 &#176;C.</li>
	<li>Harvest KB cells using standard cell culture technique. Keep the cell suspension (20,000 cells/ml) in phosphate buffered saline (PBS) on ice for short-term storage until time of injection.</li>
	<li>Prepare a KB xenografts on nude mice. Nude mice are purchased from Charles River Laboratories when they are 20 g (Category# Crl:NU(NCr)-Foxn1nu, 6-7 weeks-old), given standard diet and bedding (Harlan Laboratories; Diet: Irradiated LM-485, #7912; Bedding: Corncob bedding, &#188;&#8221;, #7097). Sterilize all the animal handling tools (syringe, forceps, and animal pad) prior to experiments. Anesthetize mice with 2% isoflurane v/v in 100% oxygen carrier gas. All animal protocols are approved by the institution (University Health Network in this case) animal care and use committee.</li>
	<li>Inject tumor cells suspended in PBS subcutaneously to the right flank of mice. Mice are ready to be used after 10 days when tumor reaches diameter of 4-5 mm and thickness of 2-3 mm.</li>
</ol>
4. In vivo Photothermal Therapy
<ol>
	<li>Inject porphysomes (containing 750 nmol pyro at 200 &#181;l volume) intravenously via tail vein. Conduct laser irradiation 24 hr post-injection of porphysomes.</li>
	<li>In this section, conduct all procedures in an enclosed laser safety room. Wear laser safety goggles during laser irradiation.</li>
	<li>Set up the laser irradiation equipment. Hold the laser fiber and a diffuser by a clamp on a stand. Set the laser power at low level and turn on the laser. Adjust the height of laser fiber to achieve an irradiation area of 9 mm in diameter (DPSS Laser, LaserGlow Technologies, Toronto, Canada), calibrate the laser power to 750 mW (1.18 W/cm2) using a power meter and then turn off the laser to prepare the animals.</li>
	<li>Anesthetize the animals with 2% isoflurane v/v in 100% oxygen carrier gas through nose cone no scavenging evident of isoflurane a human health risk hazard). Confirm that the animal is anesthetized deep enough by performing a toe pinch with forceps or fingers to animal&#39;s hind paws. The animals are ready for laser irradiation when they are unresponsive to this procedure.</li>
	<li>Monitor the tumor temperature by an infrared thermal camera (Mikroshot, LUMASENSE Technologies). Place the camera close to the tumor, focus it well and take a pre PTT image as well as a regular white-light image before PTT irradiation starts.</li>
	<li>Turn on the laser again, and increase the light power to 750 mW. Position the tumor in the center of laser beam to get the tumor fully covered, and start timing the irradiation. Take the tumor temperature image every 5 sec for a one minute laser treatment. Turn off the laser at 1 min. Stop the gas supply of 2% isoflurane, wait until the animal recovers from the anesthesia and put it back to the cage.</li>
	<li>Keep mice at normothermia animal room under 12:12 hr dark and light cycle according to animal protocols approved by University Health Network. Inject Buprenorphine (0.05 mg/kg, subcutaneously twice a day for a week following the laser irradiation to reduce the pain caused by the scar. Every two days, measure the tumor diameter using a caliper and take a photo. Calculate the tumor volume using the following equation: V=&#960;/6 &#183; a &#183; b2, where a is the long diameter, and b is the short one.</li>
	<li>Sacrifice the animals by putting them in CO2 chamber when the long diameter of the tumor reaches 10 mm, as it is the defined end point in our laboratory. Perform cervical dislocation following the CO2 treatment. Plot the survival curve.</li>
</ol>

<ol>
	<li>Lovell, J. 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=Porphysome+nanovesicles+generated+by+porphyrin+bilayers+for+use+as+multimodal+biophotonic+contrast+agents.">Porphysome nanovesicles generated by porphyrin bilayers for use as multimodal biophotonic contrast agents.</a> Nat. Mater. 10, 324-332 (2011).</li><li>Lovell, J. 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=Enzymatic+regioselection+for+the+synthesis+and+biodegradation+of+porphysome+nanovesicles.">Enzymatic regioselection for the synthesis and biodegradation of porphysome nanovesicles.</a> Angew Chem Int Ed Engl. 51, 2429-2433 (2012).</li><li>Liu, T. W., MacDonald, T. D., Shi, J., Wilson, B. C., Zheng, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intrinsically+Copper-64-Labeled+Organic+Nanoparticles+as+Radiotracers.">Intrinsically Copper-64-Labeled Organic Nanoparticles as Radiotracers.</a> Angewandte Chemie. , (2012).</li><li>Zheng, G., 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=Low-density+lipoprotein+reconstituted+by+pyropheophorbide+cholesteryl+oleate+as+target-specific+photosensitizer.">Low-density lipoprotein reconstituted by pyropheophorbide cholesteryl oleate as target-specific photosensitizer.</a> Bioconjug Chem. 13, 392-396 (2002).</li><li>Chen, B., Pogue, B. W., Hasan, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liposomal+delivery+of+photosensitising+agents.">Liposomal delivery of photosensitising agents.</a> Expert Opin Drug Deliv. 2, 477-487 (2005).</li><li>Jin, C. S., Zheng, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liposomal+nanostructures+for+photosensitizer+delivery.">Liposomal nanostructures for photosensitizer delivery.</a> Lasers Surg Med. 43, 734-748 (2011).</li><li>Olson, F., Hunt, C. A., Szoka, F. C., Vail, W. J., Papahadjopoulos, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+liposomes+of+defined+size+distribution+by+extrusion+through+polycarbonate+membranes.">Preparation of liposomes of defined size distribution by extrusion through polycarbonate membranes.</a> Biochim Biophys Acta. 557, 9-23 (1979).</li><li>Berger, N., Sachse, A., Bender, J., Schubert, R., Brandl, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Filter+extrusion+of+liposomes+using+different+devices:+comparison+of+liposome+size,+encapsulation+efficiency,+and+process+characteristics.">Filter extrusion of liposomes using different devices: comparison of liposome size, encapsulation efficiency, and process characteristics.</a> Int J Pharm. 223, 55-68 (2001).</li><li>Jesorka, A., Orwar, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liposomes:+technologies+and+analytical+applications.">Liposomes: technologies and analytical applications.</a> Annu Rev Anal Chem (Palo Alto Calif). 1, 801-832 (2008).</li><li>Lapinski, M. M., Castro-Forero, A., Greiner, A. J., Ofoli, R. Y., Blanchard, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+liposomes+formed+by+sonication+and+extrusion:+rotational+and+translational+diffusion+of+an+embedded+chromophore.">Comparison of liposomes formed by sonication and extrusion: rotational and translational diffusion of an embedded chromophore.</a> Langmuir. 23, 11677-11683 (2007).</li><li>Liu, D., Huang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Size+Homogeneity+of+a+Liposome+Preparation+is+Crucial+for+Liposome+Biodistribution+In+Vivo.">Size Homogeneity of a Liposome Preparation is Crucial for Liposome Biodistribution In Vivo.</a> Journal of Liposome Research. 2, 57-66 (1992).</li><li>Zhang, Y., Lovell, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porphyrins+as+Theranostic+Agents+from+Prehistoric+to+Modern+Times.">Porphyrins as Theranostic Agents from Prehistoric to Modern Times.</a> Theranostics. 2, 905-915 (2012).</li></ol>

We have nothing to disclose.

In the development of drug delivery technologies, multifunctional nanoparticles are currently under wide investigations for accurate tracking of the drug delivery vehicle while maintaining a high drug payload. Porphyrin-loaded liposomes have been developed for better pharmacokinetic properties and more efficient delivery than direct administration of porphyrin, but obstacles exist, including the restricted loading amount of porphyrin and rapid redistribution of porphyrin from liposomes to plasma proteins5,6. I...

Porphysomes are novel multifunctional nanovesicles that we recently developed which are capable of multimodal imaging and therapy1. They are formed from self-assembled porphyrin bilayers and contain an extremely high density of porphyrin (over 83, 000/porphysome particle), which generates large extinction coefficient and results in unique structure-dependent fluorescence self-quenching. Porphysomes have good in vivo pharmacokinetic and biodistribution properties: they exhibit a blood half-life of 12 hr following systematic administration, and passively accumulate in xenograft tumors with 7.5% ID/g at 24 hr post-injection2.
Their unique structure and physiochemical properties make porphysome a good candidate for multimodal imaging and image-guided therapy. First of all, containing porphyrin, porphysomes are intrinsically suitable for fluorescence imaging of tumors upon the tumor accumulation1. In addition, each porphyrin has a stable site for chelating radioisotopes, therefore, porphysomes can be easily labeled with radioisotopes such as 64Cu for PET imaging3. Furthermore, the absorbed light energy is dissipated thermally under laser irradiation exposure when porphysome structure is intact, so porphysomes also exhibit unique photoacoustic imaging and PTT capabilities. It has been shown that 24 hr after intravenous injection of porphysomes, laser irradiation of the porphysome-accumulated tumor induced a rapid temperature increase and strong photothermal tumor ablation. This demonstrated that porphysomes are efficient photothermal enhancers with extinction coefficient as high as gold nanoparticles (AuNPs)1. On the other hand, in comparison with other inorganic photothermal agents, including AuNPs, porphysomes show an outstanding advantage in biosafety due to their organic nature. Porphysomes are enzymatically biodegradable and induce minimal acute toxicity in mice with intravenous doses as high as 1,000 mg/kg1. Furthermore, similar to liposomes, the large aqueous core of porphysomes could be passively or actively loaded with therapeutic or imaging agents. The optical properties and biocompatibility of porphysomes demonstrate the multimodal potential of organic nanoparticles for biophotonic imaging and therapy.
In this paper, we introduce the synthesis method of pyropheophorbide-lipid conjugates, the manufacturing and the characterization method of porphysomes using high-pressure extrusion. In vivo PTT on mice is conducted as well to demonstrate the efficiency of porphysome-enabled PTT in the tumor treatment using a subcutaneous xenograft tumor model.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>Rotary evaporator</td>
			<td>Thermo-Savant</td>
			<td>SPD131DDA</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Votex</td>
			<td>Scientific Industries</td>
			<td>SI-0236</td>
			<td>Model number: G560</td>
		</tr>
		<tr>
			<td>High pressure extruder</td>
			<td>LIPEX, Northern Lipids Inc.</td>
			<td>T.001</td>
			<td>10 ml Thermobarrel Extruder</td>
		</tr>
		<tr>
			<td>Heated bath circulators (Thermostatted circulator)</td>
			<td>Thermo SCIENTIFIC</td>
			<td>SC100-S5P</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Polycarbonate filters</td>
			<td>Avanti Polar Lipids</td>
			<td>610005</td>
			<td>Pore size 100 nm, and membrane diameter 19 mm</td>
		</tr>
		<tr>
			<td>Zetasizer</td>
			<td>Malvern Instruments</td>
			<td>ZS90</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>UV/Visible Spectrophototmeter</td>
			<td>Varian Australia</td>
			<td>Cary 50 Bio UV/ Visible Spectrophotometer</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Spectrofluorometer</td>
			<td>HORIBA Scientific</td>
			<td>FluoroMax-4</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Transmission Electron Microscopy (TEM)</td>
			<td>Hitachi</td>
			<td>H-7000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cell culture incubator</td>
			<td>SANYO</td>
			<td>MCO-18AIC</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Powermeter</td>
			<td>Thorlabs</td>
			<td>PM100D</td>
			<td>with sensor S142C</td>
		</tr>
		<tr>
			<td>671nm Laser</td>
			<td>LaserGlow Technologies</td>
			<td>LRS-0671_PFN-02000-05</td>
			<td>S/N:10097270</td>
		</tr>
		<tr>
			<td>Infrared Thermometer</td>
			<td>Mikroshot, LUMASENSE Technologies</td>
			<td>9102409</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Laser protective eye goggles</td>
			<td>LaserGlow Technologies</td>
			<td>AGF6602XX</td>
			<td>Optical Density: 1.5+ at 630-700 nm</td>
		</tr>
	</tbody>
</table>

one minute, sub-one-watt photothermal tumor ablation using porphysomes, intrinsic multifunctional nanovesicles

We recently developed porphysomes as intrinsically multifunctional nanovesicles. A photosensitizer, pyropheophorbide &alpha;, was conjugated to a phospholipid and then self-assembled to liposome-like spherical vesicles. Due to the extremely high density of porphyrin in the porphyrin-lipid bilayer, porphysomes generated large extinction coefficients, structure-dependent fluorescence self-quenching, and excellent photothermal efficacy. In our formulation, porphysomes were synthesized using high pressure extrusion, and displayed a mean particle size around 120 nm. Twenty-four hr post-intravenous injection of porphysomes, the local temperature of the tumor increased from 30 &deg;C to 62 &deg;C rapidly upon one minute exposure of 750 mW (1.18 W/cm2), 671 nm laser irradiation. Following the complete thermal ablation of the tumor, eschars formed and healed within 2 weeks, while in the control groups the tumors continued to grow and all reached the defined end point within 3 weeks. These data show how porphysomes can be used as potent photothermal therapy (PTT) agents.

Pyropheophorbide is conjugated to the phospholipid as a stable lipid monomer (Figure 1a) and the conjugates self-assemble to form porphysomes by membrane extrusion method using a high pressure extruder. It is usually difficult to extrude porphysome-lipid suspension during the first 3 cycles of extrusion with relatively slow flow rate. As more extrusions are repeated, the flow rate of extruded solution gradually increases, and pressure can be slightly decreased if needed. Porphysome size, concentration, a...

Watch this Scientific Journal Video about One Minute, Sub-One-Watt Photothermal Tumor Ablation Using Porphysomes, Intrinsic Multifunctional Nanovesicles at JoVE.com

One Minute, Sub-One-Watt Photothermal Tumor Ablation Using Porphysomes, Intrinsic Multifunctional Nanovesicles

We developed novel intrinsic multifunctional nanovesicles called porphysomes, which have structure-dependent fluorescence self-quenching and unique photothermal properties, thus functioning as potent photothermal therapy agents. We formulated porphysomes using high pressure extrusion and investigated their photothermal therapy efficacy in a xenograft tumor model.

We recently developed porphysomes as intrinsically multifunctional nanovesicles. A photosensitizer, pyropheophorbide &alpha;, was conjugated to a ...

one-minute-sub-one-watt-photothermal-tumor-ablation-using-porphysomes

Research

JoVE Journal

Bioengineering

10.7K Views.  University of Toronto. We developed novel intrinsic multifunctional nanovesicles called porphysomes, which have structure-dependent fluorescence self-quenching and unique photothermal properties, thus functioning as potent photothermal therapy agents. We formulated porphysomes using high pressure extrusion and investigated their photothermal therapy efficacy in a xenograft tumor model.

Video: One Minute, Sub-One-Watt Photothermal Tumor Ablation Using Porphysomes, Intrinsic Multifunctional Nanovesicles

Contrast Ultrasound Targeted Treatment of Gliomas in Mice via Drug-Bearing Nanoparticle Delivery and Microvascular Ablation

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the microvasculature are controlled by varying ultrasound pulsing parameters.  Specifically, we are testing whether such approaches may be used to treat malignant brain tumors through drug delivery and microvascular ablation.  Preliminary studies have been performed to determine whether targeted drug-bearing nanoparticle delivery can be facilitated by the ultrasound mediated destruction of "composite" delivery agents comprised of 100nm poly(lactide-co-glycolide) (PLAGA) nanoparticles that are adhered to albumin shelled microbubbles. We denote these agents as microbubble-nanoparticle composite agents (MNCAs). When targeted to subcutaneous C6 gliomas with ultrasound, we observed an immediate 4.6-fold increase in nanoparticle delivery in MNCA treated tumors over tumors treated with microbubbles co-administered with nanoparticles and a 8.5 fold increase over non-treated tumors. Furthermore, in many cancer applications, we believe it may be desirable to perform targeted drug delivery in conjunction with ablation of the tumor microcirculation, which will lead to tumor hypoxia and apoptosis. To this end, we have tested the efficacy of non-theramal cavitation-induced microvascular ablation, showing that this approach elicits tumor perfusion reduction, apoptosis, significant growth inhibition, and necrosis. Taken together, these results indicate that our ultrasound-targeted approach has the potential to increase therapeutic efficiency by creating tumor necrosis through microvascular ablation and/or simultaneously enhancing the drug payload in gliomas.

Insonation of microbubbles is a promising strategy for tumor ablation at reduced time-averaged acoustic powers, as well as for the targeted delivery of therapeutics. The purpose of the present study is to develop low duty cycle ultrasound pulsing strategies and nanocarriers to maximize non-thermal microvascular ablation and payload delivery to subcutaneous C6 gliomas.

We are developing minimally-invasive contrast agent microbubble based therapeutic approaches in which the permeabilization and/or ablation of the ...

Optical Frequency Domain Imaging of Ex vivo Pulmonary Resection Specimens: Obtaining One to One Image to Histopathology Correlation

Lung cancer is the leading cause of cancer-related deaths1. Squamous cell and small cell cancers typically arise in association with the conducting airways, whereas adenocarcinomas are typically more peripheral in location. Lung malignancy detection early in the disease process may be difficult due to several limitations: radiological resolution, bronchoscopic limitations in evaluating tissue underlying the airway mucosa and identifying early pathologic changes, and small sample size and/or incomplete sampling in histology biopsies. High resolution imaging modalities, such as optical frequency domain imaging (OFDI), provide non-destructive, large area 3-dimensional views of tissue microstructure to depths approaching 2 mm in real time (Figure 1)2-6. OFDI has been utilized in a variety of applications, including evaluation of coronary artery atherosclerosis6,7 and esophageal intestinal metaplasia and dysplasia6,8-10.
Bronchoscopic OCT/OFDI has been demonstrated as a safe in vivo imaging tool for evaluating the pulmonary airways11-23 (Animation). OCT has been assessed in pulmonary airways16,23 and parenchyma17,22 of animal models and in vivo human airway14,15. OCT imaging of normal airway has demonstrated visualization of airway layering and alveolar attachments, and evaluation of dysplastic lesions has been found useful in distinguishing grades of dysplasia in the bronchial mucosa11,12,20,21. OFDI imaging of bronchial mucosa has been demonstrated in a short bronchial segment (0.8 cm)18. Additionally, volumetric OFDI spanning multiple airway generations in swine and human pulmonary airways in vivo has been described19. Endobronchial OCT/OFDI is typically performed using thin, flexible catheters, which are compatible with standard bronchoscopic access ports. Additionally, OCT and OFDI needle-based probes have recently been developed, which may be used to image regions of the lung beyond the airway wall or pleural surface17.
While OCT/OFDI has been utilized and demonstrated as feasible for in vivo pulmonary imaging, no studies with precisely matched one-to-one OFDI:histology have been performed. Therefore, specific imaging criteria for various pulmonary pathologies have yet to be developed. Histopathological counterparts obtained in vivo consist of only small biopsy fragments, which are difficult to correlate with large OFDI datasets. Additionally, they do not provide the comprehensive histology needed for registration with large volume OFDI. As a result, specific imaging features of pulmonary pathology cannot be developed in the in vivo setting. Precisely matched, one-to-one OFDI and histology correlation is vital to accurately evaluate features seen in OFDI against histology as a gold standard in order to derive specific image interpretation criteria for pulmonary neoplasms and other pulmonary pathologies. Once specific imaging criteria have been developed and validated ex vivo with matched one-to-one histology, the criteria may then be applied to in vivo imaging studies. Here, we present a method for precise, one to one correlation between high resolution optical imaging and histology in ex vivo lung resection specimens. Throughout this manuscript, we describe the techniques used to match OFDI images to histology. However, this method is not specific to OFDI and can be used to obtain histology-registered images for any optical imaging technique. We performed airway centered OFDI with a specialized custom built bronchoscopic 2.4 French (0.8 mm diameter) catheter. Tissue samples were marked with tissue dye, visible in both OFDI and histology. Careful orientation procedures were used to precisely correlate imaging and histological sampling locations. The techniques outlined in this manuscript were used to conduct the first demonstration of volumetric OFDI with precise correlation to tissue-based diagnosis for evaluating pulmonary pathology24. This straightforward, effective technique may be extended to other tissue types to provide precise imaging to histology correlation needed to determine fine imaging features of both normal and diseased tissues.

Optical Frequency Domain Imaging of Ex vivo Pulmonary Resection Specimens: Obtaining One to One Image to Histopathology Correlation

A method to image ex vivo pulmonary resection specimens with optical frequency domain imaging (OFDI) and obtain precise correlation to histology is described, which is essential to developing specific OFDI interpretation criteria for pulmonary pathology. This method is applicable to other tissue types and imaging techniques to obtain precise imaging to histology correlation for accurate image interpretation and assessment. Imaging criteria established with this technique would then be applicable to image assessment in future in vivo studies.

Lung cancer is the leading cause of cancer-related deaths1. Squamous cell and small cell cancers typically arise in association with the conducting ...

Viral Nanoparticles for In vivo Tumor Imaging

The use of nanomaterials has the potential to revolutionize materials science and medicine. Currently, a number of different nanoparticles are being investigated for applications in imaging and therapy. Viral nanoparticles (VNPs) derived from plants can be regarded as self-assembled bionanomaterials with defined sizes and shapes. Plant viruses under investigation in the Steinmetz lab include icosahedral particles formed by Cowpea mosaic virus (CPMV) and Brome mosaic virus (BMV), both of which are 30 nm in diameter. We are also developing rod-shaped and filamentous structures derived from the following plant viruses: Tobacco mosaic virus (TMV), which forms rigid rods with dimensions of 300 nm by 18 nm, and Potato virus X (PVX), which form filamentous particles 515 nm in length and 13 nm in width (the reader is referred to refs. 1 and 2 for further information on VNPs).
From a materials scientist's point of view, VNPs are attractive building blocks for several reasons: the particles are monodisperse, can be produced with ease on large scale in planta, are exceptionally stable, and biocompatible. Also, VNPs are "programmable" units, which can be specifically engineered using genetic modification or chemical bioconjugation methods 3. The structure of VNPs is known to atomic resolution, and modifications can be carried out with spatial precision at the atomic level4, a level of control that cannot be achieved using synthetic nanomaterials with current state-of-the-art technologies.
In this paper, we describe the propagation of CPMV, PVX, TMV, and BMV in Vigna ungiuculata and Nicotiana benthamiana plants. Extraction and purification protocols for each VNP are given. Methods for characterization of purified and chemically-labeled VNPs are described. In this study, we focus on chemical labeling of VNPs with fluorophores (e.g. Alexa Fluor 647) and polyethylene glycol (PEG). The dyes facilitate tracking and detection of the VNPs 5-10, and PEG reduces immunogenicity of the proteinaceous nanoparticles while enhancing their pharmacokinetics 8,11. We demonstrate tumor homing of PEGylated VNPs using a mouse xenograft tumor model. A combination of fluorescence imaging of tissues ex vivo using Maestro Imaging System, fluorescence quantification in homogenized tissues, and confocal microscopy is used to study biodistribution. VNPs are cleared via the reticuloendothelial system (RES); tumor homing is achieved passively via the enhanced permeability and retention (EPR) effect12. The VNP nanotechnology is a powerful plug-and-play technology to image and treat sites of disease in vivo. We are further developing VNPs to carry drug cargos and clinically-relevant imaging moieties, as well as tissue-specific ligands to target molecular receptors overexpressed in cancer and cardiovascular disease.

Viral Nanoparticles for In vivo Tumor Imaging

Plant viral nanoparticles (VNPs) are promising platforms for applications in biomedicine. Here, we describe the procedures for plant VNP propagation, purification, characterization, and bioconjugation. Finally, we show the application of VNPs for tumor homing and imaging using a mouse xenograft model and fluorescence imaging.

The use of nanomaterials has the potential to revolutionize materials science and medicine. Currently, a number of different nanoparticles are being ...

Construction of a Preclinical Multimodality Phantom Using Tissue-mimicking Materials for Quality Assurance in Tumor Size Measurement

World Health Organization (WHO) and the Response Evaluation Criteria in Solid Tumors (RECIST) working groups advocated standardized criteria for radiologic assessment of solid tumors in response to anti-tumor drug therapy in the 1980s and 1990s, respectively. WHO criteria measure solid tumors in two-dimensions, whereas RECIST measurements use only one-dimension which is considered to be more reproducible 1, 2, 3,4,5. These criteria have been widely used as the only imaging biomarker approved by the United States Food and Drug Administration (FDA) 6. In order to measure tumor response to anti-tumor drugs on images with accuracy, therefore, a robust quality assurance (QA) procedures and corresponding QA phantom are needed.
To address this need, the authors constructed a preclinical multimodality (for ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI)) phantom using tissue-mimicking (TM) materials based on the limited number of target lesions required by RECIST by revising a Gammex US commercial phantom 7. The Appendix in Lee et al. demonstrates the procedures of phantom fabrication 7. In this article, all protocols are introduced in a step-by-step fashion beginning with procedures for preparing the silicone molds for casting tumor-simulating test objects in the phantom, followed by preparation of TM materials for multimodality imaging, and finally construction of the preclinical multimodality QA phantom. The primary purpose of this paper is to provide the protocols to allow anyone interested in independently constructing a phantom for their own projects. QA procedures for tumor size measurement, and RECIST, WHO and volume measurement results of test objects made at multiple institutions using this QA phantom are shown in detail in Lee et al. 8.

This paper describes in-house procedures of constructing a preclinical multimodality phantom made of tissue-mimicking (TM) materials for quality assurance (QA) of tumor size measurement in animal imaging modalities such as ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI).

World Health Organization (WHO) and the Response Evaluation Criteria in Solid Tumors (RECIST) working groups advocated standardized criteria for ...

Production of Large Numbers of Size-controlled Tumor Spheroids Using Microwell Plates

Tumor spheroids are increasingly recognized as an important in vitro model for the behavior of tumor cells in three dimensions. More physiologically relevant than conventional adherent-sheet cultures, they more accurately recapitulate the complexity and interactions present in real tumors. In order to harness this model to better assess tumor biology, or the efficacy of novel therapeutic agents, it is necessary to be able to generate spheroids reproducibly, in a controlled manner and in significant numbers.
The AggreWell system consists of a high-density array of pyramid-shaped microwells, into which a suspension of single cells is centrifuged. The numbers of cells clustering at the bottom of each microwell, and the number and ratio of distinct cell types involved depend only on the properties of the suspension introduced by the experimenter. Thus, we are able to generate tumor spheroids of arbitrary size and composition without needing to modify the underlying platform technology. The hundreds of microwells per square centimeter of culture surface area in turn ensure that extremely high production levels may be attained via a straightforward, nonlabor-intensive process. We therefore expect that this protocol will be broadly useful to researchers in the tumor spheroid field.

We introduce a protocol for the generation of large numbers (thousands to hundreds of thousands) of uniform size- and composition-controlled tumor spheroids, using commercially available microwell plates.

Tumor spheroids are increasingly recognized as an important in vitro model for the behavior of tumor cells in three dimensions. More physiologically ...

PLGA Nanoparticles Formed by Single- or Double-emulsion with Vitamin E-TPGS

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible member of the aliphatic polyester family of biodegradable polymers. PLGA has long been a popular choice for drug delivery applications, particularly since it is already FDA-approved for use in humans in the form of resorbable sutures. Hydrophobic and hydrophilic drugs are encapsulated in PLGA particles via single- or double-emulsion. Briefly, the drug is dissolved with polymer or emulsified with polymer in an organic phase that is then emulsified with the aqueous phase. After the solvent has evaporated, particles are washed and collected via centrifugation for lyophilization and long term storage. PLGA degrades slowly via hydrolysis in aqueous environments, and encapsulated agents are released over a period of weeks to months. Although PLGA is a material that possesses many advantages for drug delivery, reproducible formation of nanoparticles can be challenging; considerable variability is introduced by the use of different equipment, reagents batch, and precise method of emulsification. Here, we describe in great detail the formation and characterization of microparticles and nanoparticles formed by single- or double-emulsion using the emulsifying agent vitamin E-TPGS. Particle morphology and size are determined with scanning electron microscopy (SEM). We provide representative SEM images for nanoparticles produced with varying emulsifier concentration, as well as examples of imaging artifacts and failed emulsifications. This protocol can be readily adapted to use alternative emulsifiers (e.g. poly(vinyl alcohol), PVA) or solvents (e.g.&#160;dichloromethane, DCM).

We describe the production and characterization of nanoparticles and microparticles composed of poly(lactic-co-glycolic acid) using vitamin E-TPGS as an emulsifier. By varying formulation parameters such as the concentration of emulsifier, it is possible to produce nanoparticles with mean diameters ranging from 220 nm to&#160;1.98 &#181;m.

Poly(lactic-co-glycolic acid) (PLGA) is a biocompatible member of the aliphatic polyester family of biodegradable polymers. PLGA has long been a popular ...

Longitudinal Measurement of Extracellular Matrix Rigidity in 3D Tumor Models Using Particle-tracking Microrheology

The mechanical microenvironment has been shown to act as a crucial regulator of tumor growth behavior and signaling, which is itself remodeled and modified as part of a set of complex, two-way mechanosensitive interactions. While the development of biologically-relevant 3D tumor models have facilitated mechanistic studies on the impact of matrix rheology on tumor growth, the inverse problem of mapping changes in the mechanical environment induced by tumors remains challenging. Here, we describe the implementation of particle-tracking microrheology (PTM) in conjunction with 3D models of pancreatic cancer as part of a robust and viable approach for longitudinally monitoring physical changes in the tumor microenvironment, in situ. The methodology described here integrates a system of preparing in vitro 3D models embedded in a model extracellular matrix (ECM) scaffold of Type I collagen with fluorescently labeled probes uniformly distributed for position- and time-dependent microrheology measurements throughout the specimen. In vitro tumors are plated and probed in parallel conditions using multiwell imaging plates. Drawing on established methods, videos of tracer probe movements are transformed via the Generalized Stokes Einstein Relation (GSER) to report the complex frequency-dependent viscoelastic shear modulus, G*(&#969;). Because this approach is imaging-based, mechanical characterization is also mapped onto large transmitted-light spatial fields to simultaneously report qualitative changes in 3D tumor size and phenotype. Representative results showing contrasting mechanical response in sub-regions associated with localized invasion-induced matrix degradation as well as system calibration, validation data are presented. Undesirable outcomes from common experimental errors and troubleshooting of these issues are also presented. The 96-well 3D culture plating format implemented in this protocol is conducive to correlation of microrheology measurements with therapeutic screening assays or molecular imaging to gain new insights into impact of treatments or biochemical stimuli on the mechanical microenvironment.

Particle-tracking microrheology can be used to non-destructively quantify and spatially map changes in extracellular matrix mechanical properties in 3D tumor models.

The mechanical microenvironment has been shown to act as a crucial regulator of tumor growth behavior and signaling, which is itself remodeled and ...

Real-time Monitoring of High Intensity Focused Ultrasound (HIFU) Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound (HMIFU)

Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a technique that can perform and monitor high-intensity focused ultrasound (HIFU) ablation. An oscillatory motion is generated at the focus of a 93-element and 4.5 MHz center frequency HIFU transducer by applying a 25 Hz amplitude-modulated signal using a function generator. A 64-element and 2.5 MHz imaging transducer with 68kPa peak pressure is confocally placed at the center of the HIFU transducer to acquire the radio-frequency (RF) channel data. In this protocol, real-time monitoring of thermal ablation using HIFU with an acoustic power of 7 W on canine livers in vitro is described. HIFU treatment is applied on the tissue during 2 min and the ablated region is imaged in real-time using diverging or plane wave imaging up to 1,000 frames/second. The matrix of RF channel data is multiplied by a sparse matrix for image reconstruction. The reconstructed field of view is of 90&#176; for diverging wave and 20 mm for plane wave imaging and the data are sampled at 80 MHz. The reconstruction is performed on a Graphical Processing Unit (GPU) in order to image in real-time at a 4.5 display frame rate. 1-D normalized cross-correlation of the reconstructed RF data is used to estimate axial displacements in the focal region. The magnitude of the peak-to-peak displacement at the focal depth decreases during the thermal ablation which denotes stiffening of the tissue due to the formation of a lesion. The displacement signal-to-noise ratio (SNRd) at the focal area for plane wave was 1.4 times higher than for diverging wave showing that plane wave imaging appears to produce better displacement maps quality for HMIFU than diverging wave imaging.

Real-time Monitoring of High Intensity Focused Ultrasound HIFU Ablation of In Vitro Canine Livers Using Harmonic Motion Imaging for Focused Ultrasound HMIFU

This article describes real-time monitoring of HIFU ablation in canine liver with high frame rate ultrasound imaging using diverging and plane wave imaging. Harmonic Motion Imaging for Focused Ultrasound is used to image the decrease of acoustic radiation force induced displacement in the ablated region.

Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a technique that can perform and monitor high-intensity focused ultrasound (HIFU) ablation. An ...

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and trade one defect for another. Tissue engineering holds the promise to address this increasing demand. However, most tissue engineering strategies fail to generate stable and functional tissue substitutes because of poor vascularization. This paper focuses on an in vivo tissue engineering chamber model of intrinsic vascularization where a perfused artery and a vein either as an arteriovenous loop or a flow-through pedicle configuration is directed inside a protected hollow chamber. In this chamber-based system angiogenic sprouting occurs from the arteriovenous vessels and this system attracts ischemic and inflammatory driven endogenous cell migration which gradually fills the chamber space with fibro-vascular tissue. Exogenous cell/matrix implantation at the time of chamber construction enhances cell survival and determines specificity of the engineered tissues which develop. Our studies have shown that this chamber model can successfully generate different tissues such as fat, cardiac muscle, liver and others. However, modifications and refinements are required to ensure target tissue formation is consistent and reproducible. This article describes a standardized protocol for the fabrication of two different vascularized tissue engineering chamber models in vivo.

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

This is a guideline for constructing in vivo vascularized tissue using a microsurgical arteriovenous loop or a flow-through pedicle configuration inside a tissue engineering chamber. The vascularized tissues generated can be employed for organ regeneration and replacement of tissue defects, as well as for drug testing and disease modeling.

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and ...

A Rapid and Chemical-free Hemoglobin Assay with Photothermal Angular Light Scattering

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis of the intrinsic photothermal response of hemoglobin molecules, the sensor enables high-sensitivity, chemical-free measurement of [Hb]. [Hb] detection capability with a limit of 0.12 g/dl over the range of 0.35 - 17.9 g/dl has been demonstrated previously. The method can be readily implemented using inexpensive consumer electronic devices such as a laser pointer and a webcam. The use of a micro-capillary tube as a blood container also enables the hemoglobin assay with a nanoliter-scale blood volume and a low operating cost. Here, detailed instructions for the PT-AS optical setup and signal processing procedures are presented. Experimental protocols and representative results for blood samples in anemic conditions ([Hb] = 5.3, 7.5, and 9.9 g/dl) are also provided, and the measurements are compared with those from a hematology analyzer. Its simplicity in implementation and operation should enable its wide adoption in clinical laboratories and resource-limited settings.

A photo-thermal angular light scattering (PT-AS) sensor enables the rapid and chemical-free hemoglobin assay of nanoliter-scale blood samples. Here, details of the PT-AS setup and a measurement protocol for the hemoglobin concentration in blood are provided. Representative results for anemic blood samples are also presented.

Photo-thermal angular light scattering (PT-AS) is a novel optical method for measuring the hemoglobin concentration ([Hb]) of blood samples. On the basis ...