Grant support has included NHLBI HL080532, NHLBI HL073449, NCRR RR16453, and an AHA National Grant-in Aid Award (to RVS). A special thanks is extended to the Distance Course Design and Consulting (DCDC) group, dcdcgroup.org, for their assistance with video production and to the US Department of Education Grant No. P336C050047 that founded the DCDC.

1. Microbubble stock preparation
<ol>
	<li>In 10 mls of PBS mix 200 mg 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine and 50 mg 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine with 1 g glucose.</li>
	<li>Heat the mixture in boiling water bath 20-30 minutes, pipette mixing every 5 minutes. </li>
	<li>The solution can be stored at 4&deg;C for up to 6 months.</li>
</ol>
2. Microbubble Preparation
<ol>
	<li>Take a 250 &mu;l of the prepared microbubble stock solution and incubate at 40&deg;C for 15 minutes. </li>
	<li>The pre-warmed microbubble solution is then transferred to a 1.5 mL microtube containing 50 &mu;l of glycerol. </li>
	<li>1-2 mg of purified plasmid DNA encoding an expression construct for the gene of interest (purified in this example by Qiagen Endotoxin free MegaPrep kit, Qiagen, Germantown, MD, with a optimal concentration of 4mg/ml). 2.4) Phosphate-buffered saline is added to a final volume of 500 &mu;l. Endotoxin free Qiagen maxipreps are used, as well as sterile PBS in order to ensure sterility.</li>
	<li>The air in the microtube is then replaced with Octafluoropropane gas. </li>
	<li>The microtube is then shaken vigorously in a dental amalgamator for 20 seconds. </li>
	<li>The subnatant containing residual DNA and buffer that has not bound to the microbubbles is then carefully removed and the microbubble layer is washed three times with sterile PBS to remove unattached DNA, and placed on ice between each wash cycle. We typically achieve a binding efficiency of 30-40%. All reagents are sterile and care is made to minimize contamination.</li>
	<li>The plasmid DNA-bound microbubbles are then placed on ice for up to two hours until use.</li>
	<li>The subnatant removed from the microtube after mixing and the PBS washes, can be used to determine the concentration of unbound DNA, and likewise the amount bound based upon the known initial concentration, by measuring the optical density of this solution at a wavelength of 260nm using a spectrophotometer. </li>
</ol>
3. Equipment Calibration
<ol>
	<li>Prior to first use, a 1 MHz cavitation transducer needs to be calibrated to ensure proper mechanical index and pulse repetition. A submergible 1 MHz, 13mm, unfocused transducer is connected to a 20 MHz Function/Arbitrary Waveform Generator through a power amplifier.</li>
	<li>The transducer is placed in a plastic container full of water, aimed directly at a hydrophone, which has been connected to a 500 MHz oscilloscope via a charge amplifier. </li>
	<li>Waveform, frequency, amplitude, burst cycle, and power amplification can all be modified to obtain the proper duty cycle and mechanical index optimal to cavitate the microbubbles. For this particular experiment, we have calibrated the system to a mechanical index equivalent to ~1.3 at 1 MHz. </li>
</ol>
4. Microbubble Delivery &amp; UTMD
<ol>
	<li>Prior to microbubble delivery and UTMD, C57BL/6 mice were anesthetized with 100mg/kg ketamine and 5mg/kg xylazine through IP injection.</li>
	<li>Microbubble delivery was administered intravenously through a direct injection into the left ventricle of the heart or through tail vein catheterization. For the direct cardiac injection, a volume up to 100 &mu;l of the plasmid DNA-loaded microbubble solution is injected through a 30 gauge needle inserted at the anterior 4th intercostal space under ultrasonic visualization into the left ventricle of the heart. </li>
	<li>The microbubble solution bolus resulting from the left interventricular injection is visualized using Visual Sonics&#x2019; 38 MHz high frequency ultrasound transducer placed in a stationary position on the thorax of the mouse in a long-axis view using VisualSonics&#x2019; Vevo 2100 Imaging System. All syringes and needles are sterile, insuring the most sterile environment possible for these injections.</li>
	<li>Immediately following the injection, microbubble destruction is carried out for ~5 minutes using a second, smaller sized low frequency 1.0 MHz transducer held directly over the desired organ, targeting destruction to this region. In this example, the ultrasound was administered to the liver at a pulse repetition frequency of 1.0 MHz, with a mechanical index equivalent to approximately 1.3-1.5, and pulse repetition period of 100 ms for every 20 cycles. Alternatively, the pulse can be gated to the ECG of the mouse (not shown in this experiment) to a burst of 3 frames of ultrasound, every 4-6 cardiac cycles. We obtain greater efficiency of transfection with protocols that allow the capillary bed to refill with bubbles between bursts of ultrasound. </li>
</ol>
5. Alternative Delivery Method
We chose to highlight the interventricular injection due to the complexity of the procedure, but in many instances, such as prolonged infusion of microbubbles, a tail vein injection is the preferred method. For the tail-vein method of microbubble delivery, the mouse is anesthetized the same way. A syringe containing the plasmid DNA-bound microbubbles is connected to a 27 gauge needle/tail vein catheter. The tail vein catheter is inserted into the distal third of either the right or left lateral veins that along the tail of the mouse. The syringe containing the microbubbles is placed in an infusion pump that automatically administers a uniform preset volume of solution over a preset period of time. We typically infuse 200-300&mu;l at a rate of 3ml/hour.
Animal use
All animals were handled in accordance with good animal practice as defined by the relevant national and/or local animal welfare bodies, and all animal work was approved by the appropriate committee (University of Hawaii Institutional Animal Care and Use Committee, approval number 07-100-3). Appropriate anesthesia (ketamine/ zylazine) was used and analgesics (Bupivicaine and Buprenorphine) were available, though not required.
6. Representative Results: 
The effectiveness of the UTMD-mediated plasmid DNA delivery can be evaluated through a variety of methods depending 
upon the genes encoded in the construct, such as, but not limited to; luciferase in vivo imaging, B-gal ex vivo staining, and/or immunohistology. 
In particular, in vivo bioluminescence imaging allows one to monitor the presence and duration of gene expression serially in mice transfected
with a plasmid encoding a bioluminescent reporter gene (luciferase). The Xenogen In Vivo Imaging System (IVIS) (Caliper Life Sciences, 
Hopkinton, MA) is used for bioluminescent imaging. Images are typically taken of all mice the first day after UTMD mediated transfection and 
is repeated every three to four days until bioluminescent gene expression is no longer visually detectable through the system (Figure 1). 
To prepare mice for bioluminescent imaging, mice first receive an IP injection of the luciferase reporter probe D-luciferin (Caliper Life 
Sciences) and are then anesthetized ~3 minutes later. Biodistribution of the D-luciferin substrate is allowed to proceed for ~10 minutes 
before the animal is placed in the IVIS imaging chamber and a full body image scan is taken. During the acquisition, the photons emitted 
from the firefly luciferase/D-luciferin photochemical reaction are measured. Figure 1 also illustrates similar IVIS bioluminescent imaging 
of the liver following UTMD, and Figure 2 is an epifluorescence (100X) image of the transfected liver using an anti-luciferase primary 
antibody (Sigma-Aldrich) and AlexFluor-568 conjugated secondary antibody (Invitrogen). It is clear to see that the UTMD mediated liver 
transfection has affected not only the endothelial cells, but the hepatocyes as well.
<img src="/files/ftp_upload/2963/2963fig1.jpg" alt="Figure 1" /> 
Figure 1. Xenogen/IVIS imaging of cardiac UTMD treated mice. (A) Negative Control Mouse: Plasmid + PBS 
followed by cardiac directed UTMD, (B) Treatment Mouse: Plasmid + Microbubbles followed by cardiac directed UTMD, and (C) Treatment Mouse: Plasmid + Microbubbles followed by liver directed UTMD.
<img src="/files/ftp_upload/2963/2963fig2.jpg" alt="Figure 2" /> 
Figure 2. Immunohistochemistry of liver UTMD (anti-luciferase in red). (A) Plasmid with no UTMD, 
and (B) Plasmid with UTMD. Confocal image (100X); nuclei are DAPI stained blue.

<ol>
	<li>Bekeredjian, R., Chen, S., Frenkel, P. A., Grayburn, P. A., Shohet, R. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound-targeted+microbubble+destruction+can+repeatedly+direct+highly+specific+plasmid+expression+to+the+heart.">Ultrasound-targeted microbubble destruction can repeatedly direct highly specific plasmid expression to the heart.</a> Circulation. 108, 1022-1026 (2003).</li><li>Bekeredjian, R., Katus, H. A., Kuecherer, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Therapeutic+use+of+ultrasound+targeted+microbubble+destruction:+a+review+of+non-cardiac+applications.">Therapeutic use of ultrasound targeted microbubble destruction: a review of non-cardiac applications.</a> Ultraschall Med. 27, 134-140 (2006).</li><li>Chen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regeneration+of+pancreatic+islets+in+vivo+by+ultrasound-targeted+gene+therapy.">Regeneration of pancreatic islets in vivo by ultrasound-targeted gene therapy.</a> Gene Ther. 17, 1411-1420 (2010).</li><li>Miao, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound+enhances+gene+delivery+of+human+factor+IX+plasmid.">Ultrasound enhances gene delivery of human factor IX plasmid.</a> Hum Gene Ther. 16, 893-905 (2005).</li><li>Shimoda, M., Chen, S., Noguchi, H., Matsumoto, S., Grayburn, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+non-viral+gene+delivery+of+human+vascular+endothelial+growth+factor+improves+revascularisation+and+restoration+of+euglycaemia+after+human+islet+transplantation+into+mouse+liver.">In vivo non-viral gene delivery of human vascular endothelial growth factor improves revascularisation and restoration of euglycaemia after human islet transplantation into mouse liver.</a> Diabetologia. 53, 1669-1679 (2010).</li><li>Shohet, R. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Echocardiographic+destruction+of+albumin+microbubbles+directs+gene+delivery+to+the+myocardium.">Echocardiographic destruction of albumin microbubbles directs gene delivery to the myocardium.</a> Circulation. 101, 2554-2556 (2000).</li><li>Sirsi, S., Borden, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbubble+Compositions,+Properties+and+Biomedical+Applications.">Microbubble Compositions, Properties and Biomedical Applications.</a> Bubble Sci Eng Technol. 1, 3-17 (2009).</li><li>Li, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrasound-targeted+microbubble+destruction+enhances+AAV-mediated+gene+transfection+in+human+RPE+cells+in+vitro+and+rat+retina+in+vivo.">Ultrasound-targeted microbubble destruction enhances AAV-mediated gene transfection in human RPE cells in vitro and rat retina in vivo.</a> Gene Ther. 16, 1146-1153 (2009).</li><li>Lindner, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbubbles+in+medical+imaging:+current+applications+and+future+directions.">Microbubbles in medical imaging: current applications and future directions.</a> Nat Rev Drug Discov. 3, 527-532 (2004).</li><li>Newman, C. M., Bettinger, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+therapy+progress+and+prospects:+ultrasound+for+gene+transfer.">Gene therapy progress and prospects: ultrasound for gene transfer.</a> Gene Ther. 14, 465-475 (2007).</li><li>Vancraeynest, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myocardial+injury+induced+by+ultrasound-targeted+microbubble+destruction:+evidence+for+the+contribution+of+myocardial+ischemia.">Myocardial injury induced by ultrasound-targeted microbubble destruction: evidence for the contribution of myocardial ischemia.</a> Ultrasound Med Biol. 35, 672-679 (2009).</li></ol>

No conflicts of interest declared.

UTMD represents a novel approach to gene delivery. As a platform technology it can be combined with any of the many potential gene therapy strategies, to deliver a myriad of bioactive molecules when a high degree of tissue specificity is desired. The main biological limitation of the technique is the low efficiency of transfection. Another important consideration is the accessibility of the target organ to ultrasound, which can be markedly diminished by intervening bone or air. The technique requires optimization of tech...

<table border="1">
	<tbody>
		<tr>
			<th>Name of the reagent/equipment</th>
			<th>Company</th>
			<th>Catalogue number</th>
			<th>Comments</th>
		</tr>
		<tr>
			<td>1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine</td>
			<td>Sigma-Aldrich</td>
			<td>P-5911</td>
			<td>component of the microbubble lipid shell</td>
		</tr>
		<tr>
			<td>1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine</td>
			<td>Sigma-Aldrich</td>
			<td>P-3275</td>
			<td>component of the microbubble lipid shell</td>
		</tr>
		<tr>
			<td>glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G5400</td>
			<td>thought to stabilize the microbubbles</td>
		</tr>
		<tr>
			<td>phosphate-buffered saline</td>
			<td>Sigma-Aldrich</td>
			<td>P5368</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sigma-Aldrich</td>
			<td>G5516</td>
			<td>believed to prevent microbubbles from coalescing</td>
		</tr>
		<tr>
			<td>Octafluoropropane gas</td>
			<td>AirGas</td>
			<td>N/A</td>
			<td>inert gas used in clinical applications</td>
		</tr>
		<tr>
			<td>VialMix dental amalgamator</td>
			<td>Bristol-Myers Squibb</td>
			<td>N/A</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>1 MHz, 13mm, unfocused transducer</td>
			<td>Olympus</td>
			<td>A303S-SU</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>20 MHz Function/Arbitrary Waveform Generator</td>
			<td>Agilent</td>
			<td>33220A</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Power Amplifier</td>
			<td>Krohn-Hite Co.</td>
			<td>Model 7500</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Hydrophone</td>
			<td>Bruel and Kjaer</td>
			<td>Type 1803</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Charge Amplifier</td>
			<td>Bruel and Kjaer</td>
			<td>Type 2634</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>500 MHz Oscilloscope</td>
			<td>LeCroy</td>
			<td>9354L</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>VisualSonics&#x2019; Vevo 2100 Imaging System with 34 MHz transducer</td>
			<td>VisualSonics</td>
			<td>2100</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>27G one inch tail vein catheters</td>
			<td>VisualSonics</td>
			<td>N/A</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Genie Plus infusion pump</td>
			<td>Kent Scientific</td>
			<td>GENIE</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

introduction to the ultrasound targeted microbubble destruction technique

In UTMD, bioactive molecules, such as negatively charged plasmid DNA vectors encoding a gene of interest, are added to the cationic shells of lipid microbubble contrast agents7-9. In mice these vector-carrying microbubbles can be administered intravenously or directly to the left ventricle of the heart. In larger animals they can also be infused through an intracoronary catheter. The subsequent delivery from the circulation to a target organ occurs by acoustic cavitation at a resonant frequency of the microbubbles. It seems likely that the mechanical energy generated by the microbubble destruction results in transient pore formation in or between the endothelial cells of the microvasculature of the targeted region10. As a result of this sonoporation effect, the transfection efficiency into and across the endothelial cells is enhanced, and transgene-encoding vectors are deposited into the surrounding tissue. Plasmid DNA remaining in the circulation is rapidly degraded by nucleases in the blood, which further reduces the likelihood of delivery to non-sonicated tissues and leads to highly specific target-organ transfection.

Watch this Scientific Journal Video about Introduction to the Ultrasound Targeted Microbubble Destruction Technique at JoVE.com

Introduction to the Ultrasound Targeted Microbubble Destruction Technique

Ultrasound Targeted Microbubble Destruction (UTMD) can be used to direct site-specific delivery of bioactive molecules, including therapeutic genes, to target organs accessible to ultrasound, such as the heart and liver1-6.

In UTMD, bioactive molecules, such as negatively charged plasmid DNA vectors encoding a gene of interest, are added to the cationic shells of lipid ...

introduction-to-ultrasound-targeted-microbubble-destruction

Research

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Bioengineering

15.4K Views.  University of Hawaii. Ultrasound Targeted Microbubble Destruction (UTMD) can be used to direct site-specific delivery of bioactive molecules, including therapeutic genes, to target organs accessible to ultrasound, such as the heart and liver1-6.

Video: Introduction to the Ultrasound Targeted Microbubble Destruction Technique

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 ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Analysis of Targeted Viral Protein Nanoparticles Delivered to HER2+ Tumors

The HER2+ tumor-targeted nanoparticle, HerDox, exhibits tumor-preferential accumulation and tumor-growth ablation in an animal model of HER2+ cancer. HerDox is formed by non-covalent self-assembly of a tumor targeted cell penetration protein with the chemotherapy agent, doxorubicin, via a small nucleic acid linker. A combination of electrophilic, intercalation, and oligomerization interactions facilitate self-assembly into round 10-20 nm particles. HerDox exhibits stability in blood as well as in extended storage at different temperatures. Systemic delivery of HerDox in tumor-bearing mice results in tumor-cell death with no detectable adverse effects to non-tumor tissue, including the heart and liver (which undergo marked damage by untargeted doxorubicin). HER2 elevation facilitates targeting to cells expressing the human epidermal growth factor receptor, hence tumors displaying elevated HER2 levels exhibit greater accumulation of HerDox compared to cells expressing lower levels, both in vitro and in vivo. Fluorescence intensity imaging combined with in situ confocal and spectral analysis has allowed us to verify in vivo tumor targeting and tumor cell penetration of HerDox after systemic delivery. Here we detail our methods for assessing tumor targeting via multimode imaging after systemic delivery.

This article details the procedures for optical imaging analysis of the tumor-targeted nanoparticle, HerDox. In particular, detailed use of the multimode imaging device for detecting tumor targeting and assessing tumor penetration is described here.

The HER2+ tumor-targeted nanoparticle, HerDox, exhibits tumor-preferential accumulation and tumor-growth ablation in an animal model of HER2+ cancer. ...

Manufacture of Concentrated, Lipid-based Oxygen Microbubble Emulsions by High Shear Homogenization and Serial Concentration

Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using sonication, mechanical agitation, microfluidic devices, or homogenization. Recently, lipid-based oxygen microbubbles (LOMs) have been designed to deliver oxygen intravenously during medical emergencies, reversing life-threatening hypoxemia, and preventing subsequent organ injury, cardiac arrest, and death. We present methods for scaled-up production of highly oxygenated microbubbles using a closed-loop high-shear homogenizer. The process can produce 2 L of concentrated LOMs (90% by volume) in 90 min. Resulting bubbles have a mean diameter of ~2 &#956;m, and a rheologic profile consistent with that of blood when diluted to 60 volume %. This technique produces LOMs in high capacity and with high oxygen purity, suggesting that this technique may be useful for translational research labs.

We describe methods for the manufacture of large volumes of lipid-based oxygen microbubbles (LOMs) designed for intravenous oxygen delivery using high-shear homogenization and serial concentration.

Gas-filled microbubbles have been developed as ultrasound contrast and drug delivery agents. Microbubbles can be produced by processing surfactants using ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

A Microfluidic Chip for ICPMS Sample Introduction

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). The chip produces monodisperse aqueous sample droplets in perfluorohexane (PFH). Size and frequency of the aqueous droplets can be varied in the range of 40 to 60 &#181;m and from 90 to 7,000&#160;Hz, respectively. The droplets are ejected from the chip with a second flow of PFH and remain intact during the ejection. A custom-built desolvation system removes the PFH and transports the droplets into the ICPMS. Here, very stable signals with a narrow intensity distribution can be measured, showing the monodispersity of the droplets. We show that the introduction system can be used to quantitatively determine iron in single bovine red blood cells. In the future, the capabilities of the introduction device can easily be extended by the integration of additional microfluidic modules.

We present a discrete droplet sample introduction system for inductively coupled plasma mass spectrometry (ICPMS). It is based on a cheap and disposable microfluidic chip that generates highly monodisperse droplets in a size range of 40&#8722;60 &#181;m at frequencies from 90 to 7,000 Hz.

This protocol discusses the fabrication and usage of a disposable low cost microfluidic chip as sample introduction system for inductively coupled plasma ...

Synthesis of Gold Nanoparticle Integrated Photo-responsive Liposomes and Measurement of Their Microbubble Cavitation upon Pulse Laser Excitation

Photo-responsive nanoparticles (NPs) have received considerable attention because of their potential in providing spatial, temporal, and dosage control over the drug release. However, most of the relevant technologies are still in the development process and are unprocurable by clinics. Here, we describe a facile fabrication of these photo-responsive NPs with commercially available gold NPs and thermo-responsive liposomes. Calcein is used as a model drug to evaluate the encapsulation efficiency and the release kinetic profile upon heat/light stimulation. Finally, we show that this photo-triggered release is due to the membrane disruption caused by microbubble cavitation, which can be measured with hydrophone.

This protocol describes a simple preparation method for gold nanoparticle integrated photo-responsive liposomes with the commercially available materials. It also shows how to measure the microbubble cavitation process of the synthesized liposomes upon the treatment of pulsed laser.

Photo-responsive nanoparticles (NPs) have received considerable attention because of their potential in providing spatial, temporal, and dosage control ...

An Experimental Protocol for Assessing the Performance of New Ultrasound Probes Based on CMUT Technology in Application to Brain Imaging

The possibility to perform an early and repeatable assessment of imaging performance is fundamental in the design and development process of new ultrasound (US) probes. Particularly, a more realistic analysis with application-specific imaging targets can be extremely valuable to assess the expected performance of US probes in their potential clinical field of application.
The experimental protocol presented in this work was purposely designed to provide an application-specific assessment procedure for newly-developed US probe prototypes based on Capacitive Micromachined Ultrasonic Transducer (CMUT) technology in relation to brain imaging.
The protocol combines the use of a bovine brain fixed in formalin as the imaging target, which ensures both realism and repeatability of the described procedures, and of neuronavigation techniques borrowed from neurosurgery. The US probe is in fact connected to a motion tracking system which acquires position data and enables the superposition of US images to reference Magnetic Resonance (MR) images of the brain. This provides a means for human experts to perform a visual qualitative assessment of the US probe imaging performance and to compare acquisitions made with different probes. Moreover, the protocol relies on the use of a complete and open research and development system for US image acquisition, i.e. the Ultrasound Advanced Open Platform (ULA-OP) scanner.
The manuscript describes in detail the instruments and procedures involved in the protocol, in particular for&#160;the calibration, image acquisition and registration of US and MR images. The obtained results prove the effectiveness of the overall protocol presented, which is entirely open (within the limits of the instrumentation involved), repeatable, and covers the entire set of acquisition and processing activities for US images.

The development of new ultrasound (US) probes based on Capacitive Micromachined Ultrasonic Transducer (CMUT) technology requires an early realistic assessment of imaging capabilities. We describe a repeatable experimental protocol for US image acquisition and comparison with magnetic resonance images, using an ex vivo bovine brain as an imaging target.

The possibility to perform an early and repeatable assessment of imaging performance is fundamental in the design and development process of new ...

Comprehensive Evaluation of the Effectiveness and Safety of Placenta-Targeted Drug Delivery Using Three Complementary Methods

No effective treatments currently exist for placenta-associated pregnancy complications, and developing strategies for the targeted delivery of drugs to the placenta while minimizing fetal and maternal side effects remains challenging. Targeted nanoparticle carriers provide new opportunities to treat placental disorders. We recently demonstrated that a synthetic placental chondroitin sulfate A binding peptide (plCSA-BP) could be used to guide nanoparticles to deliver drugs to the placenta. In this protocol, we describe in detail a system for assessing the efficiency of drug delivery to the placenta by plCSA-BP that employs three separate methods used in combination: in vivo imaging, high-frequency ultrasound (HFUS), and high-performance liquid chromatography (HPLC). Using in vivo imaging, plCSA-BP-guided nanoparticles were visualized in the placentas of live animals, while HFUS and HPLC demonstrated that plCSA-BP-conjugated nanoparticles efficiently and specifically delivered methotrexate to the placenta. Thus, a combination of these methods can be used as an effective tool for the targeted delivery of drugs to the placenta and development of new treatment strategies for several pregnancy complications.

We describe a system that utilizes three methods to evaluate the safety and effectiveness of placenta-targeted drug delivery: in vivo imaging to monitor nanoparticle accumulation, high-frequency ultrasound to monitor placental and fetal development, and HPLC to quantify drug delivery to tissue.

No effective treatments currently exist for placenta-associated pregnancy complications, and developing strategies for the targeted delivery of drugs to ...

Preparing Protein Producing Synthetic Cells using Cell Free Bacterial Extracts, Liposomes and Emulsion Transfer

The bottom-up assembly approach for construction of synthetic cells is an effective tool for isolating and investigating cellular processes in a cell mimicking environment. Furthermore, the development of cell-free expression systems has demonstrated the ability to reconstitute the protein production, transcription and translation processes (DNA&#8594;RNA&#8594;protein) in a controlled manner, harnessing synthetic biology. Here we describe a protocol for preparing a cell-free expression system, including the production of a potent bacterial lysate and encapsulating this lysate inside cholesterol-rich lipid-based giant unilamellar vesicles (GUVs) (i.e., stable liposomes), to form synthetic cells. The protocol describes the methods for preparing the components of the synthetic cells including the production of active bacterial lysates, followed by a detailed step-by-step preparation of the synthetic cells based on a water-in-oil emulsion transfer method. These facilitate the production of millions of synthetic cells in a simple and affordable manner with a high versatility for producing different types of proteins. The obtained synthetic cells can be used to investigate protein/RNA production and activity in an isolated environment, in directed evolution, and also as a controlled drug delivery platform for on-demand production of therapeutic proteins inside the body.

This protocol describes the method, materials, equipment and steps for bottom-up preparation of RNA and protein producing synthetic cells. The inner aqueous compartment of the synthetic cells contained the S30 bacterial lysate encapsulated within a lipid bilayer (i.e., stable liposomes), using a water-in-oil emulsion transfer method.

The bottom-up assembly approach for construction of synthetic cells is an effective tool for isolating and investigating cellular processes in a cell ...