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Abeid BA, Fabiilli ML, Estrada JB, Aliabouzar M. Ultra-high-speed dynamics of acoustic droplet vaporization in soft biomaterials: Effects of viscoelasticity, frequency, and bulk boiling point. Ultrason Sonochem 2024; 103:106754. [PMID: 38252981 PMCID: PMC10830863 DOI: 10.1016/j.ultsonch.2024.106754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 12/14/2023] [Accepted: 01/03/2024] [Indexed: 01/24/2024]
Abstract
Phase-shift droplets are a highly adaptable platform for biomedical applications of ultrasound. The spatiotemporal response of phase-shift droplets to focused ultrasound above a certain pressure threshold, termed acoustic droplet vaporization (ADV), is influenced by intrinsic features (e.g., bulk boiling point) and extrinsic factors (e.g., driving frequency and surrounding media). A deep understanding of ADV dynamics is critical to ensure the robustness and repeatability of an ADV-assisted application. Here, we integrated ultra-high-speed imaging, at 10 million frames per second, and confocal microscopy for a full-scale (i.e., from nanoseconds to seconds) characterization of ADV. Experiments were conducted in fibrin-based hydrogels to mimic soft tissue environments. Effects of fibrin concentration (0.2 to 8 % (w/v)), excitation frequency (1, 2.5, and 9.4 MHz), and perfluorocarbon core (perfluoropentane, perfluorohexane, and perfluorooctane) on ADV dynamics were studied. Several fundamental parameters related to ADV dynamics, such as expansion ratio, expansion velocity, collapse radius, collapse time, radius of secondary rebound, resting radius, and equilibrium radius of the generated bubbles were extracted from the radius vs time curves. Diffusion-driven ADV-bubble growth was fit to a modified Epstein-Plesset equation, adding a material stress term, to estimate the growth rate. Our results indicated that ADV dynamics were significantly impacted by fibrin concentration, frequency, and perfluorocarbon liquid core. This is the first study to combine ultra-high-speed and confocal microscopy techniques to provide insights into ADV bubble dynamics in tissue-mimicking hydrogels.
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Affiliation(s)
- Bachir A Abeid
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Jonathan B Estrada
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Mitra Aliabouzar
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI USA; Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
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2
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Aliabouzar M, Abeid BA, Kripfgans OD, Fowlkes JB, Estrada JB, Fabiilli ML. Real-time spatiotemporal characterization of mechanics and sonoporation of acoustic droplet vaporization in acoustically responsive scaffolds. Appl Phys Lett 2023; 123:114101. [PMID: 37705893 PMCID: PMC10497320 DOI: 10.1063/5.0159661] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/26/2023] [Indexed: 09/15/2023]
Abstract
Phase-shift droplets provide a flexible and dynamic platform for therapeutic and diagnostic applications of ultrasound. The spatiotemporal response of phase-shift droplets to focused ultrasound, via the mechanism termed acoustic droplet vaporization (ADV), can generate a range of bioeffects. Although ADV has been used widely in theranostic applications, ADV-induced bioeffects are understudied. Here, we integrated ultra-high-speed microscopy, confocal microscopy, and focused ultrasound for real-time visualization of ADV-induced mechanics and sonoporation in fibrin-based, tissue-mimicking hydrogels. Three monodispersed phase-shift droplets-containing perfluoropentane (PFP), perfluorohexane (PFH), or perfluorooctane (PFO)-with an average radius of ∼6 μm were studied. Fibroblasts and tracer particles, co-encapsulated within the hydrogel, were used to quantify sonoporation and mechanics resulting from ADV, respectively. The maximum radial expansion, expansion velocity, induced strain, and displacement of tracer particles were significantly higher in fibrin gels containing PFP droplets compared to PFH or PFO. Additionally, cell membrane permeabilization significantly depended on the distance between the droplet and cell (d), decreasing rapidly with increasing d. Significant membrane permeabilization occurred when d was smaller than the maximum radius of expansion. Both ultra-high-speed and confocal images indicate a hyper-local region of influence by an ADV bubble, which correlated inversely with the bulk boiling point of the phase-shift droplets. The findings provide insight into developing optimal approaches for therapeutic applications of ADV.
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Affiliation(s)
| | - Bachir A. Abeid
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | | | - Jonathan B. Estrada
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
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3
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Aliabouzar M, Kripfgans OD, Brian Fowlkes J, Fabiilli ML. Bubble nucleation and dynamics in acoustic droplet vaporization: a review of concepts, applications, and new directions. Z Med Phys 2023; 33:387-406. [PMID: 36775778 PMCID: PMC10517405 DOI: 10.1016/j.zemedi.2023.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 12/30/2022] [Accepted: 01/09/2023] [Indexed: 02/12/2023]
Abstract
The development of phase-shift droplets has broadened the scope of ultrasound-based biomedical applications. When subjected to sufficient acoustic pressures, the perfluorocarbon phase in phase-shift droplets undergoes a phase-transition to a gaseous state. This phenomenon, termed acoustic droplet vaporization (ADV), has been the subject of substantial research over the last two decades with great progress made in design of phase-shift droplets, fundamental physics of bubble nucleation and dynamics, and applications. Here, we review experimental approaches, carried out via high-speed microscopy, as well as theoretical models that have been proposed to study the fundamental physics of ADV including vapor nucleation and ADV-induced bubble dynamics. In addition, we highlight new developments of ADV in tissue regeneration, which is a relatively recently exploited application. We conclude this review with future opportunities of ADV for advanced applications such as in situ microrheology and pressure estimation.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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4
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Aliabouzar M, Quesada C, Chan ZQ, Fowlkes JB, Franceschi RT, Putnam AJ, Fabiilli ML. Acoustic droplet vaporization for on-demand modulation of microporosity in smart hydrogels. Acta Biomater 2023; 164:195-208. [PMID: 37121372 PMCID: PMC10538466 DOI: 10.1016/j.actbio.2023.04.037] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 04/10/2023] [Accepted: 04/25/2023] [Indexed: 05/02/2023]
Abstract
Microporosity in hydrogels is critical for directing tissue formation and function. We have developed a fibrin-based smart hydrogel, termed an acoustically responsive scaffold (ARS), which responds to focused ultrasound in a spatiotemporally controlled, user-defined manner. ARSs are highly flexible platforms due to the inclusion of phase-shift droplets and their tunable response to ultrasound through a mechanism termed acoustic droplet vaporization (ADV). Here, we demonstrated that ADV enabled consistent generation of micropores in ARSs, throughout the entire thickness (∼5.5 mm), utilizing perfluorooctane phase-shift droplets. Size characteristics of the generated micropores were quantified in response to critical parameters including acoustic properties, droplet size, and shear elastic modulus of fibrin using confocal microscopy. The findings showed that the length of the generated micropores correlated directly with excitation frequency, peak rarefactional pressure, pulse duration, droplet size, and indirectly with the shear elastic modulus of the fibrin matrix. The ADV-generated micropores in ARSs were further compared with cavitation-mediated micropores in fibrin gels without droplets. Additionally, the Keller-Miksis equation was used to predict an upper bound for micropore formation in ARSs at varying driving frequencies and droplet sizes. Finally, our in vivo studies showed that host cell migration following ADV-induced micropore formation was frequency-dependent, with up to 2.6 times higher cell migration at lower frequencies. Overall, these findings demonstrate a new potential application of ADV in hydrogels. STATEMENT OF SIGNIFICANCE: Interconnected micropores within a hydrogel can facilitate many cell-mediated processes. Most techniques for generating micropores are typically not biocompatible or do not enable controlled, in situ micropore formation. We used an ultrasound-based technique, termed acoustic droplet vaporization, to generate microporosity in smart hydrogels termed acoustically responsive scaffolds (ARSs). ARSs contain a fibrin matrix doped with a phase-shift droplet. We demonstrate that unique acoustic properties of phase-shift droplets can be tailored to yield spatiotemporally controlled, on-demand micropore formation. Additionally, the size characteristics of the ultrasound-generated micropores can be modulated by tuning ultrasound parameters, droplet properties, and bulk elastic properties of fibrin. Finally, we demonstrate significant, frequency-dependent host cell migration in subcutaneously implanted ARSs in mice following ultrasound-induced micropore formation in situ.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
| | - Carole Quesada
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Ze Qi Chan
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Renny T Franceschi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Dental School, University of Michigan, Ann Arbor, MI, USA
| | - Andrew J Putnam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
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Azami RH, Aliabouzar M, Osborn J, Kumar KN, Forsberg F, Eisenbrey JR, Mallik S, Sarkar K. Material Properties, Dissolution and Time Evolution of PEGylated Lipid-Shelled Microbubbles: Effects of the Polyethylene Glycol Hydrophilic Chain Configurations. Ultrasound in Medicine & Biology 2022; 48:1720-1732. [PMID: 35697583 PMCID: PMC9357055 DOI: 10.1016/j.ultrasmedbio.2022.04.216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 03/21/2022] [Accepted: 04/21/2022] [Indexed: 05/12/2023]
Abstract
Polyethylene glycol (PEG) is often added to the lipid coating of a contrast microbubble to prevent coalescence and improve circulation. At high surface density, PEG chains are known to undergo a transition from a mushroom configuration to an extended brush configuration. We investigated the effects of PEG chain configuration on attenuation and dissolution of microbubbles by varying the molar ratio of the PEGylated lipid in the shell with three (0%, 2% and 5%) in the mushroom configuration and two (10% and 20%) in the brush configuration. We measured attenuation through the bubble suspensions and used it to obtain the characteristic rheological properties of their shells according to two interfacial rheological models. The interfacial elasticity was found to be significantly lower in the brush regime (∼0.6 N/m) than in the mushroom regime (∼1.3 N/m), but similar in value within each regime. The dissolution behavior of microbubbles under acoustic excitation inside an air-saturated medium was studied by measuring the time-dependent attenuation. Total attenuation recorded a transient increase because of growth resulting from air influx and an eventual decrease caused by dissolution. Microbubble shell composition with varying PEG concentrations had significant effects on dissolution dynamics.
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Affiliation(s)
- Roozbeh H Azami
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA
| | - Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA
| | - Jenna Osborn
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA
| | - Krishna N Kumar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA
| | - Flemming Forsberg
- Department of Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - John R Eisenbrey
- Department of Radiology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
| | - Sanku Mallik
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, USA.
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Aliabouzar M, Kripfgans OD, Estrada JB, Brian Fowlkes J, Fabiilli ML. Multi-time scale characterization of acoustic droplet vaporization and payload release of phase-shift emulsions using high-speed microscopy. Ultrason Sonochem 2022; 88:106090. [PMID: 35835060 PMCID: PMC9287562 DOI: 10.1016/j.ultsonch.2022.106090] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/27/2022] [Accepted: 07/04/2022] [Indexed: 05/16/2023]
Abstract
Acoustic droplet vaporization (ADV) is the phase-transitioning of perfluorocarbon emulsions, termed phase-shift emulsions, into bubbles using focused ultrasound. ADV has been utilized in many biomedical applications. For localized drug release, phase-shift emulsions with a bioactive payload can be incorporated within a hydrogel to yield an acoustically-responsive scaffold (ARS). The dynamics of ADV and associated drug release within hydrogels are not well understood. Additionally, emulsions used in ARSs often contain high molecular weight perfluorocarbons, which is unique relative to other ADV applications. In this study, we used ultra-high-speed brightfield and fluorescence microscopy, at frame rates up to 30 million and 0.5 million frames per second, respectively, to elucidate ADV dynamics and payload release kinetics in fibrin-based ARSs containing phase-shift emulsions with three different perfluorocarbons: perfluoropentane (PFP), perfluorohexane (PFH), and perfluorooctane (PFO). At an ultrasound excitation frequency of 2.5 MHz, the maximum expansion ratio, defined as the maximum bubble diameter during ADV normalized by the initial emulsion diameter, was 4.3 ± 0.8, 4.1 ± 0.6, and 3.6 ± 0.4, for PFP, PFH, PFO emulsions, respectively. ADV yielded stable bubble formation in PFP and PFH emulsions, though the bubble growth rate post-ADV was three orders of magnitudes slower in the latter emulsion. Comparatively, ADV generated bubbles in PFO emulsions underwent repeated vaporization/recondensation or fragmentation. Different ADV-generated bubble dynamics resulted in distinct release kinetics in phase-shift emulsions carrying fluorescently-labeled payloads. The results provide physical insight enabling the modulation of bubble dynamics with ADV and hence release kinetics, which can be used for both diagnostic and therapeutic applications of ultrasound.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Jonathan B Estrada
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
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Humphries BA, Aliabouzar M, Quesada C, Bevoor A, Ho KKY, Farfel A, Buschhaus JM, Rajendran S, Fabiilli ML, Luker GD. Ultrasound-Induced Mechanical Compaction in Acoustically Responsive Scaffolds Promotes Spatiotemporally Modulated Signaling in Triple Negative Breast Cancer. Adv Healthc Mater 2022; 11:e2101672. [PMID: 35106975 PMCID: PMC9117464 DOI: 10.1002/adhm.202101672] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 01/10/2022] [Indexed: 11/06/2022]
Abstract
Cancer cells continually sense and respond to mechanical cues from the extracellular matrix (ECM). Interaction with the ECM can alter intracellular signaling cascades, leading to changes in processes that promote cancer cell growth, migration, and survival. The present study used a recently developed composite hydrogel composed of a fibrin matrix and phase-shift emulsion, termed an acoustically responsive scaffold (ARS), to investigate effects of local mechanical properties on breast cancer cell signaling. Treatment of ARSs with focused ultrasound drives acoustic droplet vaporization (ADV) in a spatiotemporally controlled manner, inducing local compaction and stiffening of the fibrin matrix adjacent to the matrix-bubble interface. Combining ARSs and live single cell imaging of triple-negative breast cancer cells, it is discovered that both basal and growth-factor stimulated activities of protein kinase B (also known as Akt) and extracellular signal-regulated kinase (ERK), two major kinases driving cancer progression, negatively correlate with increasing distance from the ADV-induced bubble both in vitro and in a mouse model. Together, these data demonstrate that local changes in ECM compaction regulate Akt and ERK signaling in breast cancer and support further applications of the novel ARS technology to analyze spatial and temporal effects of ECM mechanics on cell signaling and cancer biology.
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Affiliation(s)
- Brock A. Humphries
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
| | - Mitra Aliabouzar
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
| | - Carole Quesada
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
| | - Avinash Bevoor
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
| | - Kenneth K. Y. Ho
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
| | - Alex Farfel
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
| | - Johanna M. Buschhaus
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
- Department of Biomedical Engineering University of Michigan Ann Arbor MI 48109 USA
| | - Shrila Rajendran
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
| | - Mario L. Fabiilli
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Department of Biomedical Engineering University of Michigan Ann Arbor MI 48109 USA
- Applied Physics Program University of Michigan Ann Arbor MI 48109 USA
| | - Gary D. Luker
- Department of Radiology University of Michigan Ann Arbor MI 48109 USA
- Center for Molecular Imaging University of Michigan Ann Arbor MI 48109 USA
- Department of Biomedical Engineering University of Michigan Ann Arbor MI 48109 USA
- Department of Microbiology and Immunology University of Michigan Ann Arbor MI 48109 USA
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Burgess MT, Aliabouzar M, Aguilar C, Fabiilli ML, Ketterling JA. Slow-Flow Ultrasound Localization Microscopy Using Recondensation of Perfluoropentane Nanodroplets. Ultrasound Med Biol 2022; 48:743-759. [PMID: 35125244 PMCID: PMC8983467 DOI: 10.1016/j.ultrasmedbio.2021.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/24/2021] [Accepted: 12/07/2021] [Indexed: 05/03/2023]
Abstract
Ultrasound localization microscopy (ULM) is an emerging, super-resolution imaging technique for detailed mapping of the microvascular structure and flow velocity via subwavelength localization and tracking of microbubbles. Because microbubbles rely on blood flow for movement throughout the vascular space, acquisition times can be long in the smallest, low-flow microvessels. In addition, detection of microbubbles in low-flow regions can be difficult because of minimal separation of microbubble signal from tissue. Nanoscale, phase-change contrast agents (PCCAs) have emerged as a switchable, intermittent or persisting contrast agent for ULM via acoustic droplet vaporization (ADV). Here, the focus is on characterizing the spatiotemporal contrast properties of less volatile perfluoropentane (PFP) PCCAs. The results indicate that at physiological temperature, nanoscale PFP PCCAs with diameters less than 100 nm disappear within microseconds after ADV with high-frequency ultrasound (16 MHz, 5- to 6-MPa peak negative pressure) and that nanoscale PFP PCCAs have an inherent deactivation mechanism via immediate recondensation after ADV. This "blinking" on-and-off contrast signal allowed separation of flow in an in vitro flow phantom, regardless of flow conditions, although with a need for some replenishment at very low flow conditions to maintain count rate. This blinking behavior allows for rapid spatial mapping in areas of low or no flow with ULM, but limits velocity tracking because there is no stable bubble formation with nanoscale PFP PCCAs.
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Affiliation(s)
- Mark T Burgess
- Lizzi Center for Biomedical Engineering, Riverside Research, New York, New York, USA.
| | - Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Christian Aguilar
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeffrey A Ketterling
- Lizzi Center for Biomedical Engineering, Riverside Research, New York, New York, USA
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Aliabouzar M, Ley AW, Meurs S, Putnam AJ, Baker BM, Kripfgans OD, Fowlkes JB, Fabiilli ML. Micropatterning of acoustic droplet vaporization in acoustically-responsive scaffolds using extrusion-based bioprinting. Bioprinting 2022; 25:e00188. [PMID: 35087958 PMCID: PMC8789001 DOI: 10.1016/j.bprint.2021.e00188] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Acoustically-responsive scaffolds (ARSs) are composite hydrogels that respond to ultrasound in an on-demand, spatiotemporally-controlled manner due to the presence of a phase-shift emulsion. When exposed to ultrasound, a gas bubble is formed within each emulsion droplet via a mechanism termed acoustic droplet vaporization (ADV). In previous in vitro and in vivo studies, we demonstrated that ADV can control regenerative processes by releasing growth factors and/or modulating micromechanics in ARSs. Precise, spatial patterning of emulsion within an ARS could be beneficial for ADV-induced modulation of biochemical and biophysical cues. However, precise patterning is limited using conventional bulk polymerization techniques. Here, we developed an extrusion-based method for bioprinting ARSs with micropatterned structures. Emulsions were loaded within bioink formulations containing fibrin, hyaluronic acid and/or alginate. Experimental as well as theoretical studies elucidated the interrelations between printing parameters, needle geometry, rheological properties of the bioink, and the process-induced mechanical stresses during bioprinting. The shear thinning properties of the bioinks enabled use of lower extrusion pressures resulting in decreased shear stresses and shorter residence times, thereby facilitating high viability for cell-loaded bioinks. Bioprinting yielded greater alignment of fibrin fibers in ARSs compared to conventionally polymerized ARSs. Bioprinted ARSs also enabled generation of ADV at high spatial resolutions, which were otherwise not achievable in conventional ARSs, and acoustically-driven collapse of ADV-induced bubbles. Overall, bioprinting could aid in optimizing ARSs for therapeutic applications.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Adam W.Y. Ley
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Sabine Meurs
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Andrew J. Putnam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Brendon M. Baker
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D. Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - J. Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Mario L. Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
- Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
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Jin H, Quesada C, Aliabouzar M, Kripfgans OD, Franceschi RT, Liu J, Putnam AJ, Fabiilli ML. Release of basic fibroblast growth factor from acoustically-responsive scaffolds promotes therapeutic angiogenesis in the hind limb ischemia model. J Control Release 2021; 338:773-783. [PMID: 34530052 PMCID: PMC8526405 DOI: 10.1016/j.jconrel.2021.09.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 09/07/2021] [Accepted: 09/10/2021] [Indexed: 01/18/2023]
Abstract
Pro-angiogenic growth factors have been studied as potential therapeutics for cardiovascular diseases like critical limb ischemia (CLI). However, the translation of these factors has remained a challenge, in part, due to problems associated with safe and effective delivery. Here, we describe a hydrogel-based delivery system for growth factors where release is modulated by focused ultrasound (FUS), specifically a mechanism termed acoustic droplet vaporization. With these fibrin-based, acoustically-responsive scaffolds (ARSs), release of a growth factor is non-invasively and spatiotemporally-controlled in an on-demand manner using non-thermal FUS. In vitro studies demonstrated sustained release of basic fibroblast growth factor (bFGF) from the ARSs using repeated applications of FUS. In in vivo studies, ARSs containing bFGF were implanted in mice following induction of hind limb ischemia, a preclinical model of CLI. During the 4-week study, mice in the ARS + FUS group longitudinally exhibited significantly more perfusion and less visible necrosis compared to other experimental groups. Additionally, significantly greater angiogenesis and less fibrosis were observed for the ARS + FUS group. Overall, these results highlight a promising, FUS-based method of delivering a pro-angiogenic growth factor for stimulating angiogenesis and reperfusion in a cardiovascular disease model. More broadly, these results could be used to personalize the delivery of therapeutics in different regenerative applications by actively controlling the release of a growth factor.
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Affiliation(s)
- Hai Jin
- Department of Medical Ultrasound, Guangzhou First People's Hospital, School of Medicine, South China University of Technology, Guangzhou, China; Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Carole Quesada
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Renny T Franceschi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Dental School, University of Michigan, Ann Arbor, MI, USA
| | - Jianhua Liu
- Department of Medical Ultrasound, Guangzhou First People's Hospital, School of Medicine, South China University of Technology, Guangzhou, China
| | - Andrew J Putnam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA.
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Aliabouzar M, Kripfgans OD, Wang WY, Baker BM, Brian Fowlkes J, Fabiilli ML. Stable and transient bubble formation in acoustically-responsive scaffolds by acoustic droplet vaporization: theory and application in sequential release. Ultrason Sonochem 2021; 72:105430. [PMID: 33401189 PMCID: PMC7803826 DOI: 10.1016/j.ultsonch.2020.105430] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 12/09/2020] [Accepted: 12/14/2020] [Indexed: 05/08/2023]
Abstract
Acoustically-responsive scaffolds (ARSs), which are fibrin hydrogels containing monodispersed perfluorocarbon (PFC) emulsions, respond to ultrasound in an on-demand, spatiotemporally-controlled manner via a mechanism termed acoustic droplet vaporization (ADV). Previously, ADV has been used to control the release of bioactive payloads from ARSs to stimulate regenerative processes. In this study, we used classical nucleation theory (CNT) to predict the nucleation pressure in emulsions of different PFC cores as well as the corresponding condensation pressure of the ADV-generated bubbles. According to CNT, the threshold bubble radii above which ADV-generated bubbles remain stable against condensation were 0.4 µm and 5.2 µm for perfluoropentane (PFP) and perfluorohexane (PFH) bubbles, respectively, while ADV-generated bubbles of any size in perfluorooctane (PFO) condense back to liquid at ambient condition. Additionally, consistent with the CNT findings, stable bubble formation from PFH emulsion was experimentally observed using confocal imaging while PFO emulsion likely underwent repeated vaporization and recondensation during ultrasound pulses. In further experimental studies, we utilized this unique feature of ADV in generating stable or transient bubbles, through tailoring the PFC core and ultrasound parameters (excitation frequency and pulse duration), for sequential delivery of two payloads from PFC emulsions in ARSs. ADV-generated stable bubbles from PFH correlated with complete release of the payload while transient ADV resulted in partial release, where the amount of payload release increased with the number of ultrasound exposure. Overall, these results can be used in developing drug delivery strategies using ARSs.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - William Y Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Brendon M Baker
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA.
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12
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Lu X, Jin H, Quesada C, Farrell EC, Huang L, Aliabouzar M, Kripfgans OD, Fowlkes JB, Franceschi RT, Putnam AJ, Fabiilli ML. Spatially-directed cell migration in acoustically-responsive scaffolds through the controlled delivery of basic fibroblast growth factor. Acta Biomater 2020; 113:217-227. [PMID: 32553916 DOI: 10.1016/j.actbio.2020.06.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 05/22/2020] [Accepted: 06/09/2020] [Indexed: 12/24/2022]
Abstract
Hydrogels are commonly used in regenerative medicine for the delivery of growth factors (GFs). The spatial and temporal presentations of GFs are critical for directing regenerative processes, yet conventional hydrogels do not enable such control. We have developed a composite hydrogel, termed an acoustically-responsive scaffold (ARS), where release of a GF is non-invasively and spatiotemporally-controlled using focused ultrasound. The ARS consists of a fibrin matrix doped with a GF-loaded, phase-shift emulsion. The GF is released when the ARS is exposed to suprathreshold ultrasound via a mechanism termed acoustic droplet vaporization. In this study, we investigate how different spatial patterns of suprathreshold ultrasound can impact the biological response upon in vivo implantation of an ARS containing basic fibroblast growth factor (bFGF). ARSs were fabricated with either perfluorohexane (bFGF-C6-ARS) or perflurooctane (bFGF-C8-ARS) within the phase-shift emulsion. Ultrasound generated stable bubbles in bFGF-C6-ARS, which inhibited matrix compaction, whereas transiently stable bubbles were generated in bFGF-C8-ARS, which decreased in height by 44% within one day of implantation. The rate of bFGF release and distance of host cell migration were up to 6.8-fold and 8.1-fold greater, respectively, in bFGF-C8-ARS versus bFGF-C6-ARS. Ultrasound increased the formation of macropores within the fibrin matrix of bFGF-C8-ARS by 2.7-fold. These results demonstrate that spatially patterning suprathreshold ultrasound within bFGF-C8-ARS can be used to elicit a spatially-directed response from the host. Overall, these findings can be used in developing strategies to spatially pattern regenerative processes. STATEMENT OF SIGNIFICANCE: Hydrogels are commonly used in regenerative medicine for the delivery of growth factors (GFs). The spatial and temporal presentations of GFs are critical for directing regenerative processes, yet conventional hydrogels do not enable such control. We have developed a composite hydrogel, termed an acoustically-responsive scaffold (ARS), where GF release is non-invasively and spatiotemporally-controlled using focused ultrasound. The ARS consists of a fibrin matrix doped with a phase-shift emulsion loaded with GF, which is released when the ARS is exposed to ultrasound. In this in vivo study, we demonstrate that spatially patterning ultrasound within an ARS containing basic fibroblast growth factor (bFGF) can elicit a spatially-directed response from the host. Overall, these findings can be used in developing strategies to spatially pattern regenerative processes.
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Affiliation(s)
- Xiaofang Lu
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Hai Jin
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; School of Medicine, Second Affiliated Hospital of South China University of Technology, Guangzhou, China
| | - Carole Quesada
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Easton C Farrell
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Leidan Huang
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Ultrasound, Second Affiliated Hospital of Army Medical University, Chongqing, China
| | - Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Renny T Franceschi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA; Dental School, University of Michigan, Ann Arbor, MI, USA
| | - Andrew J Putnam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
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Aliabouzar M, Jivani A, Lu X, Kripfgans OD, Fowlkes JB, Fabiilli ML. Standing wave-assisted acoustic droplet vaporization for single and dual payload release in acoustically-responsive scaffolds. Ultrason Sonochem 2020; 66:105109. [PMID: 32248042 PMCID: PMC7217719 DOI: 10.1016/j.ultsonch.2020.105109] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 03/20/2020] [Accepted: 03/25/2020] [Indexed: 05/04/2023]
Abstract
An ultrasound standing wave field (SWF) has been utilized in many biomedical applications. Here, we demonstrate how a SWF can enhance drug release using acoustic droplet vaporization (ADV) in an acoustically-responsive scaffold (ARS). ARSs are composite fibrin hydrogels containing payload-carrying, monodispersed perfluorocarbon (PFC) emulsions and have been used to stimulate regenerative processes such as angiogenesis. Elevated amplitudes in the SWF significantly enhanced payload release from ARSs containing dextran-loaded emulsions (nominal diameter: 6 μm) compared to the -SWF condition, both at sub- and suprathreshold excitation pressures. At 2.5 MHz and 4 MPa peak rarefactional pressure, the cumulative percentage of payload released from ARSs reached 84.1 ± 5.4% and 66.1 ± 4.4% under + SWF and -SWF conditions, respectively, on day 10. A strategy for generating a SWF for an in situ ARS is also presented. For dual-payload release studies, bi-layer ARSs containing a different payload within each layer were exposed to temporally staggered ADV at 3.25 MHz (day 0) and 8.6 MHz (day 4). Sequential payload release was demonstrated using dextran payloads as well as two growth factors relevant to angiogenesis: basic fibroblast growth factor (bFGF) and platelet-derived growth factor BB (PDGF-BB). In addition, bubble growth and fibrin degradation were characterized in the ARSs under +SWF and -SWF conditions. These results highlight the utility of a SWF for modulating single and dual payload release from an ARS and can be used in future therapeutic studies.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Aniket Jivani
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Depatment of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Xiaofang Lu
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Applied Physics Program, University of Michigan, Ann Arbor, MI, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
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Aliabouzar M, Davidson CD, Wang WY, Kripfgans OD, Franceschi RT, Putnam AJ, Fowlkes JB, Baker BM, Fabiilli ML. Spatiotemporal control of micromechanics and microstructure in acoustically-responsive scaffolds using acoustic droplet vaporization. Soft Matter 2020; 16:6501-6513. [PMID: 32597450 PMCID: PMC7377967 DOI: 10.1039/d0sm00753f] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Acoustically-responsive scaffolds (ARSs), which are composite fibrin hydrogels, have been used to deliver regenerative molecules. ARSs respond to ultrasound in an on-demand, spatiotemporally-controlled manner via a mechanism termed acoustic droplet vaporization (ADV). Here, we study the ADV-induced, time-dependent micromechanical and microstructural changes to the fibrin matrix in ARSs using confocal fluorescence microscopy as well as atomic force microscopy. ARSs, containing phase-shift double emulsion (PSDE, mean diameter: 6.3 μm), were exposed to focused ultrasound to generate ADV - the phase transitioning of the PSDE into gas bubbles. As a result of ADV-induced mechanical strain, localized restructuring of fibrin occurred at the bubble-fibrin interface, leading to formation of locally denser regions. ADV-generated bubbles significantly reduced fibrin pore size and quantity within the ARS. Two types of ADV-generated bubble responses were observed in ARSs: super-shelled spherical bubbles, with a growth rate of 31 μm per day in diameter, as well as fluid-filled macropores, possibly as a result of acoustically-driven microjetting. Due to the strain stiffening behavior of fibrin, ADV induced a 4-fold increase in stiffness in regions of the ARS proximal to the ADV-generated bubble versus distal regions. These results highlight that the mechanical and structural microenvironment within an ARS can be spatiotemporally modulated using ultrasound, which could be used to control cellular processes and further the understanding of ADV-triggered drug delivery for regenerative applications.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA.
| | | | - William Y Wang
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA. and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Renny T Franceschi
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Andrew J Putnam
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA. and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
| | - Brendon M Baker
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA. and Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA and Applied Physics Program, University of Michigan, Ann Arbor, MI, USA
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Aliabouzar M, Lu X, Kripfgans OD, Fowlkes JB, Fabiilli ML. Acoustic Droplet Vaporization in Acoustically Responsive Scaffolds: Effects of Frequency of Excitation, Volume Fraction and Threshold Determination Method. Ultrasound Med Biol 2019; 45:3246-3260. [PMID: 31561948 PMCID: PMC6823163 DOI: 10.1016/j.ultrasmedbio.2019.08.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 08/11/2019] [Accepted: 08/23/2019] [Indexed: 05/03/2023]
Abstract
Ultrasound-induced vaporization of liquid perfluorocarbon (PFC) droplets into microbubbles, termed acoustic droplet vaporization (ADV), has potential therapeutic and diagnostic applications. Recently, we demonstrated how ADV-a threshold-based phenomenon-can modulate the release of biomolecules from composite hydrogels, thereby stimulating regenerative processes, such as angiogenesis. These composite hydrogels, called acoustically responsive scaffolds (ARSs), consist of monodispersed, micron size PFC emulsions embedded within a fibrin matrix. This study investigated the effects of frequency of excitation (2.25, 5, 7.5 and 10 MHz) and volume fraction (0.05%, 0.2% and 1% [v/v]) of monodispersed, double emulsions in the ARSs on the ADV threshold. We determined and compared the ADV thresholds via acoustic methods, including active detection, passive detection and attenuation, as well as an echogenicity-based method using B-mode imaging. The ADV threshold determined via these four techniques showed an increasing trend with frequency of excitation. Further analysis of the wave propagation showed that the amplitudes of high frequency harmonics were diminished in ARSs with high volume fractions of emulsion. The ADV threshold inversely correlated with the volume fraction of emulsion at the lowest excitation frequency. However, at higher frequencies, possibly due to the high acoustic reflectivity of the PFC emulsions, the ADV threshold correlated directly with the volume fraction of the emulsion. Additionally, the ADV efficiency correlated with the supra-threshold acoustic pressure. Overall, these results elucidate fundamental acoustic properties of the ARSs, which can be used in future applications.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Xiaofang Lu
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA
| | - Oliver D Kripfgans
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA; Applied Physics Program, University of Michigan, Ann Arbor, Michigan, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - J Brian Fowlkes
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA; Applied Physics Program, University of Michigan, Ann Arbor, Michigan, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Mario L Fabiilli
- Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA; Applied Physics Program, University of Michigan, Ann Arbor, Michigan, USA; Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
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Osborn J, Aliabouzar M, Zhou X, Rao R, Zhang LG, Sarkar K. Lipid-Coated Microbubbles: Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells Using Microbubbles and Low Intensity Pulsed Ultrasound on 3D Printed Scaffolds (Adv. Biosys. 2/2019). ACTA ACUST UNITED AC 2019. [DOI: 10.1002/adbi.201970021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Jenna Osborn
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
| | - Mitra Aliabouzar
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
| | - Xuan Zhou
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
| | - Raj Rao
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
- Orthopaedic Surgery; School of Medicine; George Washington University; Washington DC 20052 USA
| | - Lijie Grace Zhang
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
| | - Kausik Sarkar
- Mechanical and Aerospace Engineering; George Washington University; Washington DC 20052 USA
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Aliabouzar M, Kumar KN, Sarkar K. Effects of droplet size and perfluorocarbon boiling point on the frequency dependence of acoustic vaporization threshold. J Acoust Soc Am 2019; 145:1105. [PMID: 30823782 PMCID: PMC7112712 DOI: 10.1121/1.5091781] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Phase shift liquid perfluorocarbon (PFC) droplets vaporizable by ultrasound into echogenic microbubble above a threshold pressure, termed acoustic droplet vaporization (ADV), are used for therapeutic and diagnostic applications. This study systematically investigated the effect of excitation frequency (2.25, 10, and 15 MHz) on the ADV and inertial cavitation (IC) thresholds of lipid-coated PFC droplets of three different liquid cores-perfluoropentane (PFP), perfluorohexane (PFH), and perfluorooctyl bromide (PFOB)-and of two different sizes-average diameters smaller than 3 μm and larger than 10 μm-in a tubeless setup. This study found that the ADV threshold increases with frequency for the lowest boiling point liquid, PFP, for both large and small size droplets. For higher boiling point liquids, PFH and PFOB, this study did not detect vaporization for small size droplets at the excitation levels (maximum 4 MPa peak negative) studied here. The large PFOB droplets experienced ADV only at the highest excitation frequency 15 MHz. For large PFH droplets, ADV threshold decreases with frequency that could possibly be due to the superharmonic focusing being a significant effect at larger sizes and the higher excitation pressures. ADV thresholds at all the frequencies studied here occurred at lower rarefactional pressures than IC thresholds indicating that phase transition precedes inertial cavitation.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Krishna N Kumar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
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Osborn J, Aliabouzar M, Zhou X, Rao R, Zhang LG, Sarkar K. Enhanced Osteogenic Differentiation of Human Mesenchymal Stem Cells Using Microbubbles and Low Intensity Pulsed Ultrasound on 3D Printed Scaffolds. ACTA ACUST UNITED AC 2018; 3:e1800257. [PMID: 32627376 DOI: 10.1002/adbi.201800257] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 10/08/2018] [Indexed: 11/05/2022]
Abstract
Lipid-coated microbubbles, clinically approved as contrast enhancing agents for ultrasound imaging, are investigated for the first time for their possible applications in bone tissue engineering. Effects of microbubbles (average diameter 1.1 µm) coated by a mixture of lipids (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000], and 1,2-dipalmitoyl-3-trimethylmmonium-propane) in the presence of low intensity pulsed ultrasound (LIPUS) on human mesenchymal stem cells seeded on 3D printed poly(lactic acid) porous scaffolds are investigated. LIPUS stimulation (30 mW cm-2 , 1.5 MHz, 20% duty cycle) for 3 min a day with 0.5% v/v microbubbles results in a significant increase in proliferation (up to 19.3%) when compared to control after 1, 3, and 5 d. A 3-week osteogenic differentiation study shows a significant increase in total protein content (up to 27.5%), calcium deposition (up to 4.3%), and alkaline phosphatase activity (up to 43.1%) initiated by LIPUS with and without the presence of microbubbles. The microbubbles are found to remain stable during exposure, and their sustained oscillations demonstrably help focus the LIPUS energy toward enhanced cellular response. Integrating LIPUS and microbubbles promises to be a novel and effective strategy for bone tissue engineering and regeneration therapies.
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Affiliation(s)
- Jenna Osborn
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA
| | - Mitra Aliabouzar
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA
| | - Xuan Zhou
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA
| | - Raj Rao
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA.,Orthopaedic Surgery, School of Medicine, George Washington University, Washington, DC, 20052, USA
| | - Lijie Grace Zhang
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA
| | - Kausik Sarkar
- Mechanical and Aerospace Engineering, George Washington University, Washington, DC, 20052, USA
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Aliabouzar M, Zhang GL, Sarkar K. Acoustic and mechanical characterization of 3D-printed scaffolds for tissue engineering applications. Biomed Mater 2018; 13:055013. [DOI: 10.1088/1748-605x/aad417] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Abstract
Phase shift droplets vaporizable by acoustic stimulation offer the advantages of producing microbubbles as contrast agents in situ as well as higher stability and the possibility of achieving smaller sizes. Here, the acoustic droplet vaporization (ADV) threshold of a suspension of droplets with a perfluoropentane (PFP) core (diameter 400-3000 nm) is acoustically measured as a function of the excitation frequency in a tubeless setup at room temperature. The changes in scattered responses-fundamental, sub-, and second harmonic-are investigated, a quantitative criterion is used to determine the ADV phenomenon, and findings are discussed. The average threshold obtained using three different scattered components increases with frequency-1.05 ± 0.28 MPa at 2.25 MHz, 1.89 ± 0.57 MPa at 5 MHz, and 2.34 ± 0.014 MPa at 10 MHz. The scattered response from vaporized droplets was also found to qualitatively match with that from an independently prepared lipid-coated microbubble suspension in magnitude as well as trends above the determined ADV threshold value.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Krishna N Kumar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052, USA
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Aliabouzar M, Lee SJ, Zhou X, Zhang GL, Sarkar K. Effects of scaffold microstructure and low intensity pulsed ultrasound on chondrogenic differentiation of human mesenchymal stem cells. Biotechnol Bioeng 2017; 115:495-506. [DOI: 10.1002/bit.26480] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/24/2017] [Accepted: 08/15/2017] [Indexed: 01/07/2023]
Affiliation(s)
- Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering; The George Washington University; Washington DC
| | - Se-jun Lee
- Department of Mechanical and Aerospace Engineering; The George Washington University; Washington DC
| | - Xuan Zhou
- Department of Mechanical and Aerospace Engineering; The George Washington University; Washington DC
| | - Grace Lijjie Zhang
- Department of Mechanical and Aerospace Engineering; The George Washington University; Washington DC
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering; The George Washington University; Washington DC
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Aliabouzar M, Zhang LG, Sarkar K. Lipid Coated Microbubbles and Low Intensity Pulsed Ultrasound Enhance Chondrogenesis of Human Mesenchymal Stem Cells in 3D Printed Scaffolds. Sci Rep 2016; 6:37728. [PMID: 27883051 PMCID: PMC5121887 DOI: 10.1038/srep37728] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 10/31/2016] [Indexed: 12/12/2022] Open
Abstract
Lipid-coated microbubbles are used to enhance ultrasound imaging and drug delivery. Here we apply these microbubbles along with low intensity pulsed ultrasound (LIPUS) for the first time to enhance proliferation and chondrogenic differentiation of human mesenchymal stem cells (hMSCs) in a 3D printed poly-(ethylene glycol)-diacrylate (PEG-DA) hydrogel scaffold. The hMSC proliferation increased up to 40% after 5 days of culture in the presence of 0.5% (v/v) microbubbles and LIPUS in contrast to 18% with LIPUS alone. We systematically varied the acoustic excitation parameters-excitation intensity, frequency and duty cycle-to find 30 mW/cm2, 1.5 MHz and 20% duty cycle to be optimal for hMSC proliferation. A 3-week chondrogenic differentiation results demonstrated that combining LIPUS with microbubbles enhanced glycosaminoglycan (GAG) production by 17% (5% with LIPUS alone), and type II collagen production by 78% (44% by LIPUS alone). Therefore, integrating LIPUS and microbubbles appears to be a promising strategy for enhanced hMSC growth and chondrogenic differentiation, which are critical components for cartilage regeneration. The results offer possibilities of novel applications of microbubbles, already clinically approved for contrast enhanced ultrasound imaging, in tissue engineering.
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Affiliation(s)
- Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
| | - Lijie Grace Zhang
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
- Department of Biomedical Engineering, The George Washington University, Washington, DC, 20052, USA
- Department of Medicine, The George Washington University, Washington, DC, 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC, 20052, USA
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Zhou X, Castro NJ, Zhu W, Cui H, Aliabouzar M, Sarkar K, Zhang LG. Improved Human Bone Marrow Mesenchymal Stem Cell Osteogenesis in 3D Bioprinted Tissue Scaffolds with Low Intensity Pulsed Ultrasound Stimulation. Sci Rep 2016; 6:32876. [PMID: 27597635 PMCID: PMC5011779 DOI: 10.1038/srep32876] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 08/16/2016] [Indexed: 12/14/2022] Open
Abstract
3D printing and ultrasound techniques are showing great promise in the evolution of human musculoskeletal tissue repair and regeneration medicine. The uniqueness of the present study was to combine low intensity pulsed ultrasound (LIPUS) and advanced 3D printing techniques to synergistically improve growth and osteogenic differentiation of human mesenchymal stem cells (MSC). Specifically, polyethylene glycol diacrylate bioinks containing cell adhesive Arginine-Glycine-Aspartic acid-Serene (RGDS) peptide and/or nanocrystalline hydroxyapatite (nHA) were used to fabricate 3D scaffolds with different geometric patterns via novel table-top stereolithography 3D printer. The resultant scaffolds provide a highly porous and interconnected 3D environment to support cell proliferation. Scaffolds with small square pores were determined to be the optimal geometric pattern for MSC attachment and growth. The optimal LIPUS working parameters were determined to be 1.5 MHz, 20% duty cycle with 150 mW/cm(2) intensity. Results demonstrated that RGDS peptide and nHA containing 3D printed scaffolds under LIPUS treatment can greatly promote MSC proliferation, alkaline phosphatase activity, calcium deposition and total protein content. These results illustrate the effectiveness of the combination of LIPUS and biomimetic 3D printing scaffolds as a valuable combinatorial tool for improved MSC function, thus make them promising for future clinical and various regenerative medicine application.
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Affiliation(s)
- Xuan Zhou
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Nathan J. Castro
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Wei Zhu
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Haitao Cui
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Mitra Aliabouzar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
| | - Lijie Grace Zhang
- Department of Mechanical and Aerospace Engineering, The George Washington University, Washington DC 20052, USA
- Department of Biomedical Engineering, The George Washington University, Washington DC 20052, USA
- Department of Medicine, The George Washington University, Washington DC 20052, USA
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