Gas-Bubble Encapsulating Microcapsules (GEMs) Charles C. K Yeh

Format:

Book

Thesis/Dissertation

Author/Creator:

Yeh, Charles C. K., author.

Contributor:

University of Pennsylvania. Chemical and Biomolecular Engineering., degree granting institution.

Language:

English

Subjects (All):

0541.

0542.

0794.

Local Subjects:

0541.

0542.

0794.

Physical Description:

1 electronic resource (133 pages)

Contained In:

Dissertations Abstracts International 87-07B

Place of Publication:

Ann Arbor : ProQuest Dissertations and Theses, 2025

Language Note:

English

Summary:

Cavitation in drought-stressed plants illustrates how negative pressure can spontaneously generate gas bubbles. Separately, certain aquatic microorganisms regulate buoyancy by producing intracellular gas vesicles. Inspired by both natural phenomena, we present gas bubble-encapsulating microcapsules (GEMs) that combine these principles, mimicking the cavitation within plants by leveraging negative pressure to nucleate gas bubbles spontaneously and the buoyancy regulation of microbial gas vesicles by modulating their gaseous volume fraction. GEMs are derived from poly(d,l-lactide-co-glycolide) (PLGA) microcapsules with an aqueous core and solid polymeric shell. GEMs are formed when microcapsules experience a phenomenon known as osmosis-induced cavitation when transferred into an environment that imposes a high osmotic pressure. In this phenomenon, the internal aqueous phase experiences a large negative pressure, triggering cavitation where nucleation and growth of gas bubbles occur from dissolved air to form GEMs. This cavitation-based approach enables precise post-fabrication control of bubble size by simple modulation of the external salt concentration. We demonstrate that the buoyancy imparted by these internal gas bubbles allows for the effective purification of GEMs from impurities, such as polymer debris and defective microcapsules. Our strategy offers a straightforward, scalable, and highly controllable approach for producing GEMs. It also establishes a synthetic analogue to microbial gas vesicle systems with potential applications in purification, ultrasound theranostics, gastric drug delivery and pressure-responsive delivery of active agents.We harness the gas bubble within these GEMs to open a new avenue of microcapsule application in ultrasound- or impact-induced release. While microcapsules that are designed to release cargo under uniaxial compressive loadings have been developed, they are filled with liquid, rendering them insensitive to hydrostatic pressure. The bubble within GEMs overcomes this limitation, by imparting compressibility, rendering GEMs sensitive to hydrostatic pressure. GEMs with a well-defined thickness to diameter ratio (t/D) and volume fraction of gas are subjected to a known hydrostatic pressure through the means of a drop tower. These data establish a relationship between how the thickness to diameter ratio and volume fraction of bubble influence the rupture pressure and drug release, helping to establish the foundation for a new class of on-demand therapeutics that take advantage of pressure inputs.GEMs can also be used to deliver oxygen where the gas bubble can also be used as a reservoir to load and unload oxygen. While large amounts of oxygen can be loaded into the bubble, it can be difficult to control the release of oxygen because it is a small and diffusive molecule. To limit its diffusion, we encapsulate the bubble in a secondary shell composed of polyvinyl alcohol (PVA). The secondary shell is formed during osmosis induced cavitation by precipitating PVA that is dissolved within the core of the microcapsule during bubble growth. By controlling the concentration of PVA in the microcapsule, we can tune the t/D ratio of the secondary shell and thus control the release rate of oxygen through GEMs

Notes:

Advisors: Lee, Daeyeon; Hammer, Daniel A. Committee members: Issadore, David; Meaney, David F.

Source: Dissertations Abstracts International, Volume: 87-07, Section: B.

Ph.D. University of Pennsylvania 2025

Vendor supplied data

Local Notes:

School code: 0175

ISBN:

9798276006031

Access Restriction:

Restricted for use by site license