Biodegradable, Liquid-Filled, Spherical Capsules With Pre-Determined Burst Times

Abstract

A biodegradable poly(lactic acid-co-glycolic acid) (PLGA) capsule is presented in a spherical geometry, which exploits the principle of osmosis as an internal program to achieve a delayed-burst release of its load. The capsule burst lag-time is accurately predicted by modeling the rate of water uptake by the capsule core as a function of the capsule shell thickness, radius of the capsule, core osmotic pressure and the membrane tensile strength. Elastoplastic and failure characterization of PLGA was conducted as a function of hydration under uniaxial and biaxial stretch and by a novel “beach ball” inflation technique. The presence of small amounts of moisture leads to a decrease in yield stress and a decrease in elongation at break. The above presentation suggests reproducible preparation and evaluation of spherical rupturable osmotic capsules.