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Navarro-Becerra JA, Castillo JI, Di Ruzza F, Borden MA. Monodispersity Increases Adhesion Efficiency and Specificity for Ultrasound-Targeted Microbubbles. ACS Biomater Sci Eng 2023; 9:991-1001. [PMID: 36153974 DOI: 10.1021/acsbiomaterials.2c00528] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ultrasound molecular imaging with targeted microbubbles (MBs) can be used to noninvasively diagnose, monitor, and study the progression of different endothelial-associated diseases. Acoustic radiation force (Frad) can initiate and enhance MB adhesion at the target site. The goal of this study was to elucidate the effects of various MB parameters on Frad targeting. Monodisperse or polydisperse MBs with the immune-stealth cloaked (buried)-ligand architecture were conjugated with targeting RGD or nonspecific isotype control RAD peptides and then pumped through an αvβ3 integrin-coated microvessel phantom at a wall shear stress of 3.5 dyn/cm2. Targeting was assessed by measuring MB attachment for varying Frad time and frequency, as well as MB concentration and size distribution. We first confirmed that primary Frad is necessary to target the cloaked-ligand MBs. MB targeting increased monotonically with αvβ3 integrin density and Frad time. MB attachment and, to a lesser extent specificity, also increased when driven by Frad near resonance. MB targeting increased with MB concentration, although a shift in behavior was observed with increasing MB-MB interactions and aggregations forming from secondary Frad effects as MB concentration was increased. These secondary Frad effects reduced targeting specificity. Finally, after having validated our approach by testing different parameters with the appropriate controls, we then determined the effects of monodispersity on adhesion efficiency and specific targeting. We observed that both MB targeting efficiency and specificity were greatly enhanced for monodisperse vs polydisperse MBs. Analysis of videomicroscopy images indicated that secondary Frad effects may have disproportionally inhibited targeting of polydisperse MBs. In conclusion, our in vitro results indicate that monodisperse MBs driven near resonance and at a low concentration (∼106 MB/mL) can be used to maximize the adhesion efficiency (up to 88%) and specificity of RGD-MB targeting.
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Affiliation(s)
- J Angel Navarro-Becerra
- Mechanical Engineering Department, University of Colorado Boulder, Boulder, Colorado 80309-0427, United States
| | - Jair I Castillo
- Biomedical Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309-0427, United States
| | - Federico Di Ruzza
- Biomedical Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309-0427, United States.,Chemical Science and Technology Department, University of Rome Tor Vergata, Roma 00133, Italy
| | - Mark A Borden
- Mechanical Engineering Department, University of Colorado Boulder, Boulder, Colorado 80309-0427, United States.,Biomedical Engineering Program, University of Colorado Boulder, Boulder, Colorado 80309-0427, United States
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Zalloum IO, Paknahad AA, Kolios MC, Karshafian R, Tsai SSH. Controlled Shrinkage of Microfluidically Generated Microbubbles by Tuning Lipid Concentration. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13021-13029. [PMID: 36260341 DOI: 10.1021/acs.langmuir.2c01439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Monodisperse microbubbles with diameters less than 10 μm are desirable in several ultrasound imaging and therapeutic delivery applications. However, conventional approaches to synthesize microbubbles, which are usually agitation-based, produce polydisperse bubbles that are less desirable because of their heterogeneous response when exposed to an ultrasound field. Microfluidics technology has the unique advantage of generating size-controlled monodisperse microbubbles, and it is now well established that the diameter of microfluidically made microbubbles can be tuned by varying the liquid flow rate, gas pressure, and dimensions of the microfluidic channel. It is also observed that once the microbubbles form, the bubbles shrink and eventually stabilize to a quasi-equilibrium diameter, and that the rate of stabilization is related to the lipid solution. However, how the lipid solution concentration affects the degree of bubble shrinkage, and the stable size of microbubbles, has not been thoroughly examined. Here, we investigate whether and how the lipid concentration affects the degree of microbubble shrinkage. Namely, we utilize a flow-focusing microfluidic geometry to generate monodisperse bubbles, and observe the effect of gas composition (2.5, 1.42, and 0.17 wt % octafluoropropane in nitrogen) and lipid concentration (1-16 mg/mL) on the degree of microbubble shrinkage. For the lipid system and gas utilized in these experiments, we observe a monotonic increase in the degree of microbubble shrinkage with decreasing lipid concentration, and no dependency on the gas composition. We hypothesize that the degree of shrinkage is related to lipid concentration by the self-assembly of lipids on the gas-liquid interface during bubble generation and subsequent lipid packing on the interface during shrinkage, which is arrested when a maximum packing density is achieved. We anticipate that this approach for creating and tuning the size of monodisperse microbubbles will find utility in biomedical applications, such as contrast-enhanced ultrasound imaging and ultrasound-triggered gene delivery.
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Affiliation(s)
- Intesar O Zalloum
- Department of Physics, Toronto Metropolitan University, Toronto, Ontario M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST), A Partnership Between Toronto Metropolitan University and St. Michael's Hospital, 209 Victoria Street, Toronto, Ontario M5B 1T8, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, 209 Victoria Street, Toronto, Ontario M5B 1W8, Canada
| | - Ali A Paknahad
- Department of Mechanical and Industrial Engineering, Toronto Metropolitan University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST), A Partnership Between Toronto Metropolitan University and St. Michael's Hospital, 209 Victoria Street, Toronto, Ontario M5B 1T8, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, 209 Victoria Street, Toronto, Ontario M5B 1W8, Canada
| | - Michael C Kolios
- Department of Physics, Toronto Metropolitan University, Toronto, Ontario M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST), A Partnership Between Toronto Metropolitan University and St. Michael's Hospital, 209 Victoria Street, Toronto, Ontario M5B 1T8, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, 209 Victoria Street, Toronto, Ontario M5B 1W8, Canada
| | - Raffi Karshafian
- Department of Physics, Toronto Metropolitan University, Toronto, Ontario M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST), A Partnership Between Toronto Metropolitan University and St. Michael's Hospital, 209 Victoria Street, Toronto, Ontario M5B 1T8, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, 209 Victoria Street, Toronto, Ontario M5B 1W8, Canada
| | - Scott S H Tsai
- Department of Mechanical and Industrial Engineering, Toronto Metropolitan University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada
- Institute for Biomedical Engineering, Science and Technology (iBEST), A Partnership Between Toronto Metropolitan University and St. Michael's Hospital, 209 Victoria Street, Toronto, Ontario M5B 1T8, Canada
- Keenan Research Centre for Biomedical Science, Unity Health Toronto, 209 Victoria Street, Toronto, Ontario M5B 1W8, Canada
- Graduate Program in Biomedical Engineering, Toronto Metropolitan University, 350 Victoria Street, Toronto, Ontario M5B 2K3, Canada
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