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Kaushik A, Abeid BA, Estrada JB, Fowlkes JB, Fabiilli ML, Aliabouzar M. The radial dynamics and acoustic emissions of phase-shift droplets are impacted by mechanical properties of tissue-mimicking hydrogels. ULTRASONICS SONOCHEMISTRY 2024; 109:106984. [PMID: 39018892 PMCID: PMC11305293 DOI: 10.1016/j.ultsonch.2024.106984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/27/2024] [Accepted: 07/08/2024] [Indexed: 07/19/2024]
Abstract
Acoustic droplet vaporization (ADV) offers a dynamic approach for generating bubbles on demand, presenting new possibilities in biomedical applications. Although ADV has been investigated in various biomedical applications, its potential in tissue characterization remains unexplored. Here, we investigated the effects of surrounding media on the radial dynamics and acoustic emissions of ADV bubbles using theoretical and experimental methodologies. For theoretical studies, bubble dynamics were combined with the Kelvin-Voigt material constitutive model, accounting for viscoelasticity of the media. The radial dynamics and acoustic emissions of the ADV-bubbles were recorded via ultra-high-speed microscopy and passive cavitation detection, respectively. Perfluoropentane phase-shift droplets were embedded in tissue-mimicking hydrogels of varying fibrin concentrations, representing different elastic moduli. Radial dynamics and the acoustic emissions, both temporal and spectral, of the ADV-bubbles depended significantly on fibrin elastic modulus. For example, an increase in fibrin elastic modulus from ≈0.2 kPa to ≈6 kPa reduced the maximum expansion radius of the ADV-bubbles by 50%. A similar increase in the elastic modulus significantly impacted both linear (e.g., fundamental) and nonlinear (e.g., subharmonic) acoustic responses of the ADV-bubbles, by up to 10 dB. The sensitivity of ADV to the surrounding media was dependent on acoustic parameters such as driving pressure and the droplets concentration. Further analysis of the acoustic emissions revealed distinct ADV signal characteristics, which were significantly influenced by the surrounding media.
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Affiliation(s)
- Anuj Kaushik
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA
| | - Bachir A Abeid
- Department of Mechanical Engineering, 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
| | - Mitra Aliabouzar
- Department of Radiology, University of Michigan, Ann Arbor, MI, USA; Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA.
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2
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Ramesh R, Thimonier C, Desgranges S, Faugeras V, Coulouvrat F, Laurent J, Marrelec G, Contino-Pépin C, Urbach W, Tribet C, Taulier N. Acoustic Droplet Vaporization of Perfluorohexane Emulsions Induced by Heterogeneous Nucleation at an Ultrasonic Frequency of 1.1 MHz. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:15716-15729. [PMID: 37889478 DOI: 10.1021/acs.langmuir.3c02272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
Droplets made of liquid perfluorocarbon undergo a phase transition and transform into microbubbles when triggered by ultrasound of intensity beyond a critical threshold; this mechanism is called acoustic droplet vaporization (ADV). It has been shown that if the intensity of the signal coming from high ultrasonic harmonics are sufficiently high, superharmonic focusing is the mechanism leading to ADV for large droplets (>3 μm) and high frequencies (>1.5 MHz). In such a scenario, ADV is initiated due to a nucleus occurring at a specific location inside the droplet volume. But the question on what induces ADV in the case of nanometer-sized droplets and/or at low ultrasonic frequencies (<1.5 MHz) still remains. We investigated ADV of perfluorohexane (PFH) nano- and microdroplets at a frequency of 1.1 MHz and at conditions where there is no superharmonic focusing. Three types of droplets produced by microfluidics were studied: plain PFH droplets, PFH droplets containing many nanometer-sized water droplets, and droplets made of a PFH corona encapsulating a single micron-sized water droplet. The probability to observe a vaporization event was measured as a function of acoustic pressure. As our experiments were performed on droplet suspensions containing a population of monodisperse droplets, we developed a statistical model to extrapolate, from our experimental curves, the ADV pressure thresholds in the case where only one droplet would be insonified. We observed that the value of ADV pressure threshold decreases as the radius of a plain PFH droplet increases. This value was further reduced when a PFH droplet encapsulates a micron-sized water droplet, while the encapsulation of many nanometer-sized water droplets did not modify the threshold. These results cannot be explained by a model of homogeneous nucleation. However, we developed a heterogeneous nucleation model, where the nucleus appears at the surface in contact with PFH, that successfully predicts our experimental ADV results.
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Affiliation(s)
- R Ramesh
- CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, LIB, Sorbonne Université, F-75006 Paris, France
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris Cité, F-75005 Paris, France
| | - C Thimonier
- CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, LIB, Sorbonne Université, F-75006 Paris, France
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris Cité, F-75005 Paris, France
- Département de Chimie, P.A.S.T.E.U.R., École Normale Supérieure, Université PSL, Sorbonne Université, CNRS, 75005 Paris, France
| | - S Desgranges
- Équipe Systèmes Amphiphiles Bioactifs et Formulations Eco-compatibles, UPRI, Avignon Université, 84000 Avignon, France
| | - V Faugeras
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris Cité, F-75005 Paris, France
| | - F Coulouvrat
- Institut Jean le Rond d'Alembert, CNRS, Sorbonne Université, 4 Place Jussieu, 75005 Paris, France
| | - J Laurent
- Laboratoire de Physique et Mécanique des Milieux Hétérogénes, CNRS, ESPCI Paris, PSL Research University, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - G Marrelec
- CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, LIB, Sorbonne Université, F-75006 Paris, France
| | - C Contino-Pépin
- Équipe Systèmes Amphiphiles Bioactifs et Formulations Eco-compatibles, UPRI, Avignon Université, 84000 Avignon, France
| | - W Urbach
- Laboratoire de Physique de l'École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, F-75005 Paris, France
| | - C Tribet
- PASTEUR, Département de Chimie, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France
| | - N Taulier
- CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, LIB, Sorbonne Université, F-75006 Paris, France
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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] [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] [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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5
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Wear KA, Shah A. Nominal Versus Actual Spatial Resolution: Comparison of Directivity and Frequency-Dependent Effective Sensitive Element Size for Membrane, Needle, Capsule, and Fiber-Optic Hydrophones. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2023; 70:112-119. [PMID: 36178990 DOI: 10.1109/tuffc.2022.3211183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Frequency-dependent effective sensitive element radius [Formula: see text] is a key parameter for elucidating physical mechanisms of hydrophone operation. In addition, it is essential to know [Formula: see text] to correct for hydrophone output voltage reduction due to spatial averaging across the hydrophone sensitive element surface. At low frequencies, [Formula: see text] is greater than geometrical sensitive element radius ag . Consequently, at low frequencies, investigators can overrate their hydrophone spatial resolution. Empirical models for [Formula: see text] for membrane, needle, and fiber-optic hydrophones have been obtained previously. In this article, an empirical model for [Formula: see text] for capsule hydrophones is presented, so that models are now available for the four most common hydrophone types used in biomedical ultrasound. The [Formula: see text] value was estimated from directivity measurements (over the range from 1 to 20 MHz) for five capsule hydrophones (three with [Formula: see text] and two with [Formula: see text]). The results suggest that capsule hydrophones behave according to a "rigid piston" model for k a g ≥ 0.7 ( k = 2π /wavelength). Comparing the four hydrophone types, the low-frequency discrepancy between [Formula: see text] and ag was found to be greatest for membrane hydrophones, followed by capsule hydrophones, and smallest for needle and fiber-optic hydrophones. Empirical models for [Formula: see text] are helpful for choosing an appropriate hydrophone for an experiment and for correcting for spatial averaging (over the sensitive element surface) in pressure and beamwidth measurements. When reporting hydrophone-based pressure measurements, investigators should specify [Formula: see text] at the center frequency (which may be estimated from the models presented here) in addition to ag .
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Benton RP, Al Rifai N, Stone K, Clark A, Zhang B, Haworth KJ. Impact of Perfluoropentane Microdroplets Diameter and Concentration on Acoustic Droplet Vaporization Transition Efficiency and Oxygen Scavenging. Pharmaceutics 2022; 14:pharmaceutics14112392. [PMID: 36365210 PMCID: PMC9694497 DOI: 10.3390/pharmaceutics14112392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/25/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022] Open
Abstract
Acoustic droplet vaporization is the ultrasound-mediated phase change of liquid droplets into gas microbubbles. Following the phase change, oxygen diffuses from the surrounding fluid into the microbubble. An in vitro model was used to study the effects of droplet diameter, the presence of an ultrasound contrast agent, ultrasound duty cycle, and droplet concentration on the magnitude of oxygen scavenging in oxygenated deionized water. Perfluoropentane droplets were manufactured through a microfluidic approach at nominal diameters of 1, 3, 5, 7, 9, and 12 µm and studied at concentrations varying from 5.1 × 10-5 to 6.3 × 10-3 mL/mL. Droplets were exposed to an ultrasound transduced by an EkoSonicTM catheter (2.35 MHz, 47 W, and duty cycles of 1.70%, 2.34%, or 3.79%). Oxygen scavenging and the total volume of perfluoropentane that phase-transitioned increased with droplet concentration. The ADV transition efficiency decreased with increasing droplet concentration. The increasing duty cycle resulted in statistically significant increases in oxygen scavenging for 1, 3, 5, and 7 µm droplets, although the increase was smaller than when the droplet diameter or concentration were increased. Under the ultrasound conditions tested, droplet diameter and concentration had the greatest impact on the amount of ADV and subsequent oxygen scavenging occurred, which should be considered when using ADV-mediated oxygen scavenging in therapeutic ultrasounds.
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Affiliation(s)
- Rachel P. Benton
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Nour Al Rifai
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Kateryna Stone
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Abigail Clark
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH 45267, USA
| | - Bin Zhang
- Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Kevin J. Haworth
- Department of Internal Medicine, Division of Cardiovascular Health and Disease, University of Cincinnati, Cincinnati, OH 45267, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45229, USA
- Correspondence: ; Tel.: +1-513-558-3536
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7
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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. ULTRASONICS SONOCHEMISTRY 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] [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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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 (AMSTERDAM, NETHERLANDS) 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] [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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9
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Spatiotemporal control of myofibroblast activation in acoustically-responsive scaffolds via ultrasound-induced matrix stiffening. Acta Biomater 2022; 138:133-143. [PMID: 34808418 PMCID: PMC8738148 DOI: 10.1016/j.actbio.2021.11.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/02/2021] [Accepted: 11/15/2021] [Indexed: 01/17/2023]
Abstract
Hydrogels are often used to study the impact of biomechanical and topographical cues on cell behavior. Conventional hydrogels are designed a priori, with characteristics that cannot be dynamically changed in an externally controlled, user-defined manner. We developed a composite hydrogel, termed an acoustically-responsive scaffold (ARS), that enables non-invasive, spatiotemporally controlled modulation of mechanical and morphological properties using focused ultrasound. An ARS consists of a phase-shift emulsion distributed in a fibrin matrix. Ultrasound non-thermally vaporizes the emulsion into bubbles, which induces localized, radial compaction and stiffening of the fibrin matrix. In this in vitro study, we investigate how this mechanism can control the differentiation of fibroblasts into myofibroblasts, a transition correlated with substrate stiffness on 2D substrates. Matrix compaction and stiffening was shown to be highly localized using confocal and atomic force microscopies, respectively. Myofibroblast phenotype, evaluated by α-smooth muscle actin (α-SMA) immunocytochemistry, significantly increased in matrix regions proximal to bubbles compared to distal regions, irrespective of the addition of exogenous transforming growth factor-β1 (TGF-β1). Introduction of the TGF-β1 receptor inhibitor SB431542 abrogated the proximal enhancement. This approach providing spatiotemporal control over biophysical signals and resulting cell behavior could aid in better understanding fibrotic disease progression and the development of therapeutic interventions for chronic wounds. STATEMENT OF SIGNIFICANCE: Hydrogels are used in cell culture to recapitulate both biochemical and biophysical aspects of the native extracellular matrix. Biophysical cues like stiffness can impact cell behavior. However, with conventional hydrogels, there is a limited ability to actively modulate stiffness after polymerization. We have developed an ultrasound-based method of spatiotemporally-controlling mechanical and morphological properties within a composite hydrogel, termed an acoustically-responsive scaffold (ARS). Upon exposure to ultrasound, bubbles are non-thermally generated within the fibrin matrix of an ARS, thereby locally compacting and stiffening the matrix. We demonstrate how ARSs control the differentiation of fibroblasts into myofibroblasts in 2D. This approach could assist with the study of fibrosis and the development of therapies for chronic wounds.
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10
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Osborn J, Anderson MS, Beddingfield M, Zhang LG, Sarkar K. Acoustic Droplet Vaporization of Perfluorocarbon Droplets in 3D-Printable Gelatin Methacrylate Scaffolds. ULTRASOUND IN MEDICINE & BIOLOGY 2021; 47:3263-3274. [PMID: 34456086 DOI: 10.1016/j.ultrasmedbio.2021.07.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/19/2021] [Accepted: 07/20/2021] [Indexed: 06/13/2023]
Abstract
Scientists face a significant challenge in creating effective biomimetic constructs in tissue engineering with sustained and controlled delivery of growth factors. Recently, the addition of phase-shift droplets inside the scaffolds is being explored for temporal and spatial control of biologic delivery through vaporization using external ultrasound stimulation. Here, we explore acoustic droplet vaporization (ADV) in gelatin methacrylate (GelMA), a popular hydrogel used for tissue engineering applications because of its biocompatibility, tunable mechanical properties and rapid reproducibility. We embedded phase-shift perfluorocarbon droplets within the GelMA resin before crosslinking and characterized ADV and inertial cavitation (IC) thresholds of the embedded droplets. We were successful in vaporizing two different perfluorocarbon---perfluoropentane (PFP) and perfluorohexane (PFH)--cores at 2.25- and 5-MHz frequencies and inside hydrogels with varying mechanical properties. The ADV and IC thresholds for PFP droplets in GelMA scaffolds increased with frequency and in stiffer scaffolds. The PFH droplets exhibited ADV and IC activity only at 5 MHz for the range of excitations below 3MPa investigated here and at threshold values higher than those of PFP droplets. The results provide a proof of concept for the possible use of ADV in hydrogel scaffolds for tissue engineering.
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Affiliation(s)
- Jenna Osborn
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, USA
| | - Megan S Anderson
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, USA
| | - Morgan Beddingfield
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, USA
| | - Lijie Grace Zhang
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, USA
| | - Kausik Sarkar
- Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, USA.
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Krafft MP, Riess JG. Therapeutic oxygen delivery by perfluorocarbon-based colloids. Adv Colloid Interface Sci 2021; 294:102407. [PMID: 34120037 DOI: 10.1016/j.cis.2021.102407] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 03/18/2021] [Accepted: 03/25/2021] [Indexed: 02/06/2023]
Abstract
After the protocol-related indecisive clinical trial of Oxygent, a perfluorooctylbromide/phospholipid nanoemulsion, in cardiac surgery, that often unduly assigned the observed untoward effects to the product, the development of perfluorocarbon (PFC)-based O2 nanoemulsions ("blood substitutes") has come to a low. Yet, significant further demonstrations of PFC O2-delivery efficacy have continuously been reported, such as relief of hypoxia after myocardial infarction or stroke; protection of vital organs during surgery; potentiation of O2-dependent cancer therapies, including radio-, photodynamic-, chemo- and immunotherapies; regeneration of damaged nerve, bone or cartilage; preservation of organ grafts destined for transplantation; and control of gas supply in tissue engineering and biotechnological productions. PFC colloids capable of augmenting O2 delivery include primarily injectable PFC nanoemulsions, microbubbles and phase-shift nanoemulsions. Careful selection of PFC and other colloid components is critical. The basics of O2 delivery by PFC nanoemulsions will be briefly reminded. Improved knowledge of O2 delivery mechanisms has been acquired. Advanced, size-adjustable O2-delivering nanoemulsions have been designed that have extended room-temperature shelf-stability. Alternate O2 delivery options are being investigated that rely on injectable PFC-stabilized microbubbles or phase-shift PFC nanoemulsions. The latter combine prolonged circulation in the vasculature, capacity for penetrating tumor tissues, and acute responsiveness to ultrasound and other external stimuli. Progress in microbubble and phase-shift emulsion engineering, control of phase-shift activation (vaporization), understanding and control of bubble/ultrasound/tissue interactions is discussed. Control of the phase-shift event and of microbubble size require utmost attention. Further PFC-based colloidal systems, including polymeric micelles, PFC-loaded organic or inorganic nanoparticles and scaffolds, have been devised that also carry substantial amounts of O2. Local, on-demand O2 delivery can be triggered by external stimuli, including focused ultrasound irradiation or tumor microenvironment. PFC colloid functionalization and targeting can help adjust their properties for specific indications, augment their efficacy, improve safety profiles, and expand the range of their indications. Many new medical and biotechnological applications involving fluorinated colloids are being assessed, including in the clinic. Further uses of PFC-based colloidal nanotherapeutics will be briefly mentioned that concern contrast diagnostic imaging, including molecular imaging and immune cell tracking; controlled delivery of therapeutic energy, as for noninvasive surgical ablation and sonothrombolysis; and delivery of drugs and genes, including across the blood-brain barrier. Even when the fluorinated colloids investigated are designed for other purposes than O2 supply, they will inevitably also carry and deliver a certain amount of O2, and may thus be considered for O2 delivery or co-delivery applications. Conversely, O2-carrying PFC nanoemulsions possess by nature a unique aptitude for 19F MR imaging, and hence, cell tracking, while PFC-stabilized microbubbles are ideal resonators for ultrasound contrast imaging and can undergo precise manipulation and on-demand destruction by ultrasound waves, thereby opening multiple theranostic opportunities.
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Affiliation(s)
- Marie Pierre Krafft
- University of Strasbourg, Institut Charles Sadron (CNRS), 23 rue du Loess, 67034 Strasbourg, France.
| | - Jean G Riess
- Harangoutte Institute, 68160 Ste Croix-aux-Mines, France
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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. ULTRASONICS SONOCHEMISTRY 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] [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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13
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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. ULTRASONICS SONOCHEMISTRY 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] [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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Melich R, Bussat P, Morici L, Vivien A, Gaud E, Bettinger T, Cherkaoui S. Microfluidic preparation of various perfluorocarbon nanodroplets: Characterization and determination of acoustic droplet vaporization (ADV) threshold. Int J Pharm 2020; 587:119651. [DOI: 10.1016/j.ijpharm.2020.119651] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 07/08/2020] [Accepted: 07/10/2020] [Indexed: 12/16/2022]
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15
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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] [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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16
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Norris EG, Dalecki D, Hocking DC. Using Acoustic Fields to Fabricate ECM-Based Biomaterials for Regenerative Medicine Applications. RECENT PROGRESS IN MATERIALS 2020; 2:1-24. [PMID: 33604591 PMCID: PMC7889011 DOI: 10.21926/rpm.2003018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Ultrasound is emerging as a promising tool for both characterizing and fabricating engineered biomaterials. Ultrasound-based technologies offer a diverse toolbox with outstanding capacity for optimization and customization within a variety of therapeutic contexts, including improved extracellular matrix-based materials for regenerative medicine applications. Non-invasive ultrasound fabrication tools include the use of thermal and mechanical effects of acoustic waves to modify the structure and function of extracellular matrix scaffolds both directly, and indirectly via biochemical and cellular mediators. Materials derived from components of native extracellular matrix are an essential component of engineered biomaterials designed to stimulate cell and tissue functions and repair or replace injured tissues. Thus, continued investigations into biological and acoustic mechanisms by which ultrasound can be used to manipulate extracellular matrix components within three-dimensional hydrogels hold much potential to enable the production of improved biomaterials for clinical and research applications.
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Affiliation(s)
- Emma G Norris
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
| | - Diane Dalecki
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA
| | - Denise C Hocking
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York, USA
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, USA
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