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Yan WC, Chua QW, Ong XJ, Sharma VK, Tong YW, Wang CH. Fabrication of ultrasound-responsive microbubbles via coaxial electrohydrodynamic atomization for triggered release of tPA. J Colloid Interface Sci 2017; 501:282-293. [PMID: 28460221 DOI: 10.1016/j.jcis.2017.04.073] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 04/21/2017] [Accepted: 04/23/2017] [Indexed: 01/16/2023]
Abstract
A single-step fabrication method, coaxial electrohydrodynamic atomization (CEHDA), was developed to synthesize drug-loaded microbubbles (MBs) for combination treatment of ischemic stroke. The bioactivity of therapeutic agent (tPA, tissue plasminogen activator) after preparation was evaluated, showing that CEHDA could be very promising method for producing MBs with therapeutic functions. The bubble performance and tPA release profiles were also examined by exposing the bubbles to 2MHz ultrasound of various intensities. The results showed that the mean diameter of tPA-loaded MBs was found to fluctuate about its original diameter when exposed to ultrasound and higher intensity ultrasound was more effective in triggering the burst of CEHDA MBs. High ultrasound-triggered bubble disintegration effectiveness in a short period (first 5min) fits well with the requirement of short ultrasound exposure time for human brain. Moreover, a numerical model was also applied to investigate the stability of the fabricated MBs in the bloodstream. It was found that MB dissolution time increased with initial radius, decreased with initial surface tension and increased with initial shell resistance but it was barely affected by the average excessive bloodstream pressure.
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Affiliation(s)
- Wei-Cheng Yan
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Qing Wei Chua
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Xiu Jing Ong
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Vijay Kumar Sharma
- Division of Neurology, Department of Medicine, National University Hospital, Tower Block Level 10, 1E Kent Ridge Road, Singapore 119228, Singapore
| | - Yen Wah Tong
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore
| | - Chi-Hwa Wang
- Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
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Shah SS, Denham LV, Elison JR, Bhattacharjee PS, Clement C, Huq T, Hill JM. Drug delivery to the posterior segment of the eye for pharmacologic therapy. EXPERT REVIEW OF OPHTHALMOLOGY 2014; 5:75-93. [PMID: 20305803 DOI: 10.1586/eop.09.70] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Treatment of diseases of the posterior segment of the eye, such as age-related macular degeneration, cytomegalovirus retinitis, diabetic retinopathy, posterior uveitis and retinitis pigmentosa, requires novel drug delivery systems that can overcome the many barriers for efficacious delivery of therapeutic drug concentrations. This challenge has prompted the development of biodegradable and nonbiodegradable sustained-release systems for injection or transplantation into the vitreous as well as drug-loaded nanoparticles, microspheres and liposomes. These drug delivery systems utilize topical, systemic, subconjunctival, intravitreal, transscleral and iontophoretic routes of administration. The focus of research has been the development of methods that will increase the efficacy of spatiotemporal drug application, resulting in more successful therapy for patients with posterior segment diseases. This article summarizes recent advances in the research and development of drug delivery methods of the posterior chamber of the eye, with an emphasis on the use of implantable devices as well as micro- and nanoparticles.
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Affiliation(s)
- Shalin S Shah
- Department of Ophthalmology, Louisiana State University Health Sciences Center (LSUHSC), 2020 Gravier St. Suite B, Room 3E6, New Orleans, LA 70112-2234, USA, Tel.: +1 678 296 2334, ,
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3
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Dzaharudin F, Suslov SA, Manasseh R, Ooi A. Effects of coupling, bubble size, and spatial arrangement on chaotic dynamics of microbubble cluster in ultrasonic fields. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:3425-34. [PMID: 24180753 DOI: 10.1121/1.4821202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Microbubble clustering may occur when bubbles become bound to targeted surfaces or are grouped by acoustic radiation forces in medical diagnostic applications. The ability to identify the formation of such clusters from the ultrasound echoes may be of practical use. Nonlinear numerical simulations were performed on clusters of microbubbles modeled by the modified Keller-Miksis equations. Encapsulated bubbles were considered to mimic practical applications but the aim of the study was to examine the effects of inter-bubble spacing and bubble size on the dynamical behavior of the cluster and to see if chaotic or bifurcation characteristics could be helpful in diagnostics. It was found that as microbubbles were clustered closer together, their oscillation amplitude for a given applied ultrasound power was reduced, and for inter-bubble spacing smaller than about ten bubble radii nonlinear subharmonics and ultraharmonics were eliminated. For clustered microbubbles, as for isolated microbubbles, an increase in the applied acoustic power caused bifurcations and transition to chaos. The bifurcations preceding chaotic behavior were identified by Floquet analysis and confirmed to be of the period-doubling type. It was found that as the number of microbubbles in a cluster increased, regularization occurred at lower ultrasound power and more windows of order appeared.
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Affiliation(s)
- Fatimah Dzaharudin
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Victoria 3010, Australia
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Threlfall G, Wu HJ, Li K, Aldham B, Scoble J, Sutalo ID, Raicevic A, Pontes-Braz L, Lee B, Schneider-Kolsky M, Ooi A, Coia G, Manasseh R. Quantitative guidelines for the prediction of ultrasound contrast agent destruction during injection. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1838-1847. [PMID: 23849383 DOI: 10.1016/j.ultrasmedbio.2013.04.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2012] [Revised: 04/08/2013] [Accepted: 04/21/2013] [Indexed: 06/02/2023]
Abstract
Experiments and theory were undertaken on the destruction of ultrasound contrast agent microbubbles on needle injection, with the aim of predicting agent loss during in vivo studies. Agents were expelled through a variety of syringe and needle combinations, subjecting the microbubbles to a range of pressure drops. Imaging of the bubbles identified cases where bubbles were destroyed and the extent of destruction. Fluid-dynamic calculations determined the pressure drop for each syringe and needle combination. It was found that agent destruction occurred at a critical pressure drop that depended only on the type of microbubble. Protein-shelled microbubbles (sonicated bovine serum albumin) were virtually all destroyed above their critical pressure drop of 109 ± 7 kPa Two types of lipid-shelled microbubbles were found to have a pressure drop threshold above which more than 50% of the microbubbles were destroyed. The commercial lipid-shelled agent Definity was found to have a critical pressure drop for destruction of 230 ± 10 kPa; for a previously published lipid-shelled agent, this value was 150 ± 40 kPa. It is recommended that attention to the predictions of a simple formula could preclude unnecessary destruction of microbubble contrast agent during in vivo injections. This approach may also preclude undesirable release of drug or gene payloads in targeted microbubble therapies. Example values of appropriate injection rates for various agents and conditions are given.
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Affiliation(s)
- Greg Threlfall
- CSIRO Materials Science and Engineering, Highett, Melbourne, Australia
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Mullin LB, Phillips LC, Dayton PA. Nanoparticle delivery enhancement with acoustically activated microbubbles. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2013; 60:65-77. [PMID: 23287914 PMCID: PMC3822910 DOI: 10.1109/tuffc.2013.2538] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The application of microbubbles and ultrasound to deliver nanoparticle carriers for drug and gene delivery is an area that has expanded greatly in recent years. Under ultrasound exposure, microbubbles can enhance nanoparticle delivery by increasing cellular and vascular permeability. In this review, the underlying mechanisms of enhanced nanoparticle delivery with ultrasound and microbubbles and various proposed delivery techniques are discussed. Additionally, types of nanoparticles currently being investigated in preclinical studies, as well as the general limitations and benefits of a microbubble- based approach to nanoparticle delivery, are reviewed.
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Affiliation(s)
- Lee B Mullin
- Joint Department of Biomedical Engineering The University of North Carolina at Chapel Hill, and North Carolina State University
| | - Linsey C Phillips
- Joint Department of Biomedical Engineering The University of North Carolina at Chapel Hill, and North Carolina State University
| | - Paul A Dayton
- Joint Department of Biomedical Engineering The University of North Carolina at Chapel Hill, and North Carolina State University
- Author to whom correspondence should be addressed Paul A. Dayton Campus Box 7575, UNC Chapel Hill Chapel Hill, NC 27599
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Kagadis GC, Loudos G, Katsanos K, Langer SG, Nikiforidis GC. In vivosmall animal imaging: Current status and future prospects. Med Phys 2010; 37:6421-42. [DOI: 10.1118/1.3515456] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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The use of contrast enhanced ultrasound in carotid arterial disease. Eur J Vasc Endovasc Surg 2010; 39:381-7. [PMID: 20060758 DOI: 10.1016/j.ejvs.2009.12.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 12/10/2009] [Indexed: 11/22/2022]
Abstract
Traditionally, stroke risk stratification has centred on the degree of internal carotid artery stenosis, and the presence of focal neurological symptoms. However, degree of stenosis alone is a relatively poor predictor of future stroke in asymptomatic patients; the Asymptomatic Carotid Surgery Trial highlighting the need to identify a subgroup of asymptomatics that may benefit from intervention. Attempting to define this subgroup has inspired imaging research to identify, in vivo, high-risk plaques. In addition to pre-operative risk stratification of carotid stenosis, contrast enhanced ultrasound (CEUS) may be employed in monitoring response to plaque-stabilising therapies. Unlike most contrast agents used for computed tomography and magnetic resonance imaging, microbubbles used in CEUS remain within the vascular space and can hence be used to study the vasculature. In addition to improving current carotid structural scans, CEUS has potential to add extra information on plaque characteristics. Furthermore, by targeting microbubbles to specific ligands expressed on vascular endothelium, CEUS may have the ability to probe plaque biology. This review describes the current carotid ultrasound examination and the need to improve it, rationale for imaging neovascularisation, use of CEUS to image neovascularisation, microbubbles in improving the structural imaging of plaque, potential problems with CEUS, and future directions.
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Medel R, Crowley RW, McKisic MS, Dumont AS, Kassell NF. Sonothrombolysis: an emerging modality for the management of stroke. Neurosurgery 2009; 65:979-93; discussion 993. [PMID: 19834413 DOI: 10.1227/01.neu.0000350226.30382.98] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE Ischemic stroke and intracranial hemorrhage remain a persistent scourge in Western civilization. Therefore, novel therapeutic modalities are desperately needed to expand the current limitations of treatment. Sonothrombolysis possesses the potential to fill this void because it has experienced a dramatic evolution from the time of early conceptualization in the 1960s. This process began in the realm of peripheral and cardiovascular disease and has since progressed to encompass intracranial pathologies. Our purpose is to provide a comprehensive review of the historical progression and existing state of knowledge, including underlying mechanisms as well as evidence for clinical application of ultrasound thrombolysis. METHODS Using MEDLINE, in addition to cross-referencing existing publications, a meticulous appraisal of the literature was conducted. Additionally, personal communications were used as appropriate. RESULTS This appraisal revealed several different technologies close to broad clinical use. However, fundamental questions remain, especially in regard to transcranial high-intensity focused ultrasound. Currently, the evidence supporting low intensity ultrasound's potential in isolation, without tissue plasminogen, remains uncertain; however, possibilities exist in the form of microbubbles to allow for focal augmentation with minimal systemic consequences. Alternatively, the literature clearly demonstrates, the efficacy of high-intensity focused ultrasound for independent thrombolysis. CONCLUSION Sonothrombolysis exists as a promising modality for the noninvasive or minimally invasive management of stroke, both ischemic and hemorrhagic. Further research facilitating clinical application is warranted.
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Affiliation(s)
- Ricky Medel
- Department of Neurological Surgery, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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Geis NA, Mayer CR, Kroll RD, Hardt SE, Katus HA, Bekeredjian R. Spatial distribution of ultrasound targeted microbubble destruction increases cardiac transgene expression but not capillary permeability. ULTRASOUND IN MEDICINE & BIOLOGY 2009; 35:1119-1126. [PMID: 19427103 DOI: 10.1016/j.ultrasmedbio.2009.01.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2008] [Revised: 12/31/2008] [Accepted: 01/26/2009] [Indexed: 05/27/2023]
Abstract
Ultrasound targeted microbubble destruction (UTMD) has evolved as a promising tool for organ specific gene and drug delivery. Using DNA-loaded microbubbles, cardiac transfection has been shown to be feasible. However, two-dimensional properties of the ultrasound beam limit cardiac transgene expression to the focal zone, thus, reducing its potential therapeutic effect. The aim of this study was to test if spatial distribution of ultrasound targeted microbubble destruction in the heart could lead to augmented transgene expression or increased capillary permeability. Lipid microbubbles containing plasmids with a luciferase transgene were used to target rat hearts. The diagnostic ultrasound probe was fixed in a mid-short axis view with a gel stand-off between the chest and probe. Ultrasound (1.3 MHz) with a mechanical index of 1.6 was intermittently applied to rats during microbubble infusion. Rats were randomized to either stay in that position or move horizontally in a cranio-caudal direction (3 mm sweep) relative to the ultrasound probe during UTMD. After 4 days, organs were harvested and analyzed for reporter gene expression. Another group of rats received Evans Blue, followed by UTMD with unloaded microbubbles. Again, rats were randomized into a static or moving group. Hearts were harvested to evaluate extravasation of Evans Blue. Moving rats in a cranio-caudal direction significantly increased transgene expression by 19-fold in the anterior heart, by sixfold in the posterior heart and by 32-fold in the apex. Interestingly, Evans Blue extravasation was not augmented in the moving group. Spatial distribution of UTMD may increase transgene expression due to sonication of larger areas in the heart. In contrast, capillary permeability does not increase, indicating less capillary damage.
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Affiliation(s)
- Nicolas A Geis
- Internal Medicine III, University of Heidelberg, Heidelberg 69120, Germany
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Torchilin V. Multifunctional and stimuli-sensitive pharmaceutical nanocarriers. Eur J Pharm Biopharm 2008; 71:431-44. [PMID: 18977297 DOI: 10.1016/j.ejpb.2008.09.026] [Citation(s) in RCA: 441] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 08/29/2008] [Accepted: 09/02/2008] [Indexed: 11/26/2022]
Abstract
Currently used pharmaceutical nanocarriers, such as liposomes, micelles, and polymeric nanoparticles, demonstrate a broad variety of useful properties, such as longevity in the body; specific targeting to certain disease sites; enhanced intracellular penetration; contrast properties allowing for direct carrier visualization in vivo; stimuli-sensitivity, and others. Some of those pharmaceutical carriers have already made their way into clinic, while others are still under preclinical development. In certain cases, the pharmaceutical nanocarriers combine several of the listed properties. Long-circulating immunoliposomes capable of prolonged residence in the blood and specific target recognition represent one of the examples of this kind. The engineering of multifunctional pharmaceutical nanocarriers combining several useful properties in one particle can significantly enhance the efficacy of many therapeutic and diagnostic protocols. This paper considers the current status and possible future directions in the emerging area of multifunctional nanocarriers with primary attention on the combination of such properties as longevity, targetability, intracellular penetration, contrast loading, and stimuli-sensitivity.
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Affiliation(s)
- Vladimir Torchilin
- Department of Pharmaceutical Sciences and Center for Pharmaceutical Biotechnology and Nanomedicine, Northeastern University, MA 02115, USA
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Ravi S, Amoros J, Arockia Jayalatha K. Effective Method of Characterizing Specific Liquid Fluorocarbon Interactions Using Ultrasound. J Phys Chem B 2008; 112:6420-5. [DOI: 10.1021/jp800812c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- S. Ravi
- Department of Physics, National College, Tiruchirapalli 620 001, India, Departmento de Fisica Applicada, Universitad de Cantabria, Avda, Los Castros, 39005 Santander, Spain, and Department of Physics, Cauvery College for Women, Tiruchirapalli 620 018, India
| | - J. Amoros
- Department of Physics, National College, Tiruchirapalli 620 001, India, Departmento de Fisica Applicada, Universitad de Cantabria, Avda, Los Castros, 39005 Santander, Spain, and Department of Physics, Cauvery College for Women, Tiruchirapalli 620 018, India
| | - K. Arockia Jayalatha
- Department of Physics, National College, Tiruchirapalli 620 001, India, Departmento de Fisica Applicada, Universitad de Cantabria, Avda, Los Castros, 39005 Santander, Spain, and Department of Physics, Cauvery College for Women, Tiruchirapalli 620 018, India
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Soman NR, Marsh JN, Hughes MS, Lanza GM, Wickline SA. Acoustic activation of targeted liquid perfluorocarbon nanoparticles does not compromise endothelial integrity. IEEE Trans Nanobioscience 2006; 5:69-75. [PMID: 16805101 DOI: 10.1109/tnb.2006.875052] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Perfluorocarbon nanoparticles consisting essentially of liquid perfluoro-octyl bromide (PFOB) core surrounded by a lipid monolayer can serve as highly specific site-targeted contrast and therapeutic agents after binding to cellular biomarkers. Based on previous findings that ultrasound applied at 2 MHz and 1.9 mechanical index (MI) for a 5-min duration dramatically enhances the cellular interaction of targeted PFOB nanoparticles with melanoma cells in vitro without inducing apoptosis or other harmful effects to cells that are targeted, we sought to define mechanisms of interaction and the safety profile of ultrasound used in conjunction with liquid perfluorocarbon nanoparticles for targeted drug delivery, as compared with conventional microbubble ultrasound contrast agents under identical insonification conditions. Cell-culture inserts were used to grow a confluent monolayer of human umbilical vein endothelial cells. Definity in conjunction with continuous wave ultrasound (2.25 MHz for 1 and 5 min) increased the permeability of monolayer by four to six times above the normal, decreased transendothelial electrical resistance (a sign of reduced membrane integrity), and decreased cell viability by approximately 50%. Histological evaluation demonstrated extensive disruptions of cell monolayers. Nanoparticles (both nontargeted and targeted) elicited no changes in these different measures under similar insonification conditions and did not disrupt cell monolayers. We hypothesize that ultrasound facilitates drug transport from the perfluorocarbon nanoparticles not by cavitation-induced effects on cell membrane but rather by direct interaction with the nanoparticles that stimulate lipid exchange and drug delivery.
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Affiliation(s)
- Neelesh R Soman
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA.
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Lentz YK, Anchordoquy TJ, Lengsfeld CS. DNA acts as a nucleation site for transient cavitation in the ultrasonic nebulizer. J Pharm Sci 2006; 95:607-19. [PMID: 16432878 DOI: 10.1002/jps.20511] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Several new technologies based upon ultrasound technology have been proposed as a method to enhance the delivery of genetic therapeutics. Using ultrasonic nebulization and a well-established method to quantitatively monitor transient cavitation, this study investigates the extent and factors influencing the degradation of DNA. Results from our studies show that the presence of DNA greatly enhances cavitation, and that the number of transient cavitation events also increases with the hydrodynamic diameter and number of DNA molecules in solution. More importantly, removing saturated gases from the plasmid DNA solutions resulted in a decrease in transient cavitation events but not degradation rate, suggesting that the cavitation event responsible for degradation occurs locally at the DNA molecule. Finally, complexing plasmid DNA with the cationic polymer polyethylenimine protected the native structure by reducing the molecule's potential to act as a heterogeneous nucleation site for transient cavitation.
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Affiliation(s)
- Y K Lentz
- University of Colorado Health Sciences Center, School of Pharmacy, Denver, 80262, USA.
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Laraudogoitia Zaldumbide E, Moya Mur JL. [Update in cardiac imaging techniques. Echocardiography and magnetic resonance imaging]. Rev Esp Cardiol 2006; 59 Suppl 1:31-7. [PMID: 16540018 DOI: 10.1157/13084446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article is a review of the main developments in cardiac imaging techniques reported in publications during 2005. Recent advances in digital technology have led to steadily increasing reliance on imaging techniques in the management of cardiovascular disease. We discuss advances in two techniques that fall under the remit of the echocardiography working group: echocardiography and magnetic resonance imaging.
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Abstract
Ashrafian and colleagues describe the use of myocardial contrast echocardiography to assess a 63-year-old man with ischemic heart disease.
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Affiliation(s)
| | | | - Roxy Senior
- * To whom correspondence should be addressed: E-mail:
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Frenkel V, Oberoi J, Stone MJ, Park M, Deng C, Wood BJ, Neeman Z, Horne M, Li KCP. Pulsed high-intensity focused ultrasound enhances thrombolysis in an in vitro model. Radiology 2006; 239:86-93. [PMID: 16493016 PMCID: PMC2386885 DOI: 10.1148/radiol.2391042181] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To evaluate the use of pulsed high-intensity focused ultrasound exposures to improve tissue plasminogen activator (tPA)-mediated thrombolysis in an in vitro model. MATERIALS AND METHODS All experimental work was compliant with institutional guidelines and HIPAA. Clots were formed by placing 1 mL of human blood in closed-off sections of pediatric Penrose tubes. Four experimental groups were evaluated: control (nontreated) clots, clots treated with pulsed high-intensity focused ultrasound only, clots treated with tPA only, and clots treated with pulsed high-intensity focused ultrasound plus tPA. The focused ultrasound exposures (real or sham) were followed by incubations of the clots in tPA with saline or in saline only. Thrombolysis was measured as the relative reduction in the mass of the clot. D-Dimer assays also were performed. Two additional experiments were performed and yielded dose-response curves for two exposure parameters: number of pulses per raster point and total acoustic power. Radiation force-induced displacements caused by focused ultrasound exposures were simulated in the clots. A Tukey-Kramer honestly significant difference test was performed for comparisons between all pairs of experimental groups. RESULTS The clots treated with focused ultrasound alone did not show significant increases in thrombolysis compared with the control clots. The clots treated with focused ultrasound plus tPA showed a 50% ([30.2/20.1]/20.1) increase in the degree of thrombolysis compared with the clots treated with tPA only (P < .001), further corroborating the d-dimer assay results (P < .001). Additional experiments revealed how increasing both the number of pulses per raster point and the total acoustic power yielded corresponding increases in the thrombolysis rate. In the latter experiment, simulations performed at a range of power settings revealed a direct correlation between increased displacement and observed thrombolysis rate. CONCLUSION The rate of tPA-mediated thrombolysis can be enhanced by using pulsed high-intensity focused ultrasound exposure in vitro.
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Affiliation(s)
- Victor Frenkel
- Departments of Diagnostic Radiology and Laboratory Medicine, Clinical Center, National Institutes of Health, 10 Center Drive, Bldg 10, Room 1C657, Bethesda, MD 20892, USA.
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Martina AD, Meyer-Wiethe K, Allémann E, Seidel G. Ultrasound Contrast Agents for Brain Perfusion Imaging and Ischemic Stroke Therapy. J Neuroimaging 2006. [DOI: 10.1111/j.1552-6569.2005.tb00314.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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