ABSTRACT
A microentrapment system may be defined as any small particle in which a substance is held on the surface or within a dry powder substrate. In the 1950s, Smith Kline revolutionized the oral delivery of drugs by introducing the Spansule™ system for sustained delivery. Spansules are gelatin capsules filled with small drug particles or drugs in sugar that have been coated with varying thicknesses of a slowly soluble coating material. In the industrial arena, pioneering work on microencapsulation began in the 1940s with research on the use of a gelatin coating applied by a technique called coacervation. A micromatrix is an entrapment system in which the entrapped material is dissolved, dispersed, adsorbed, or absorbed throughout the particle. A component of wound dressings is a major area where polyurethanes are used topically. Thin films and membranes constructed of suitable polyurethane combine good mechanical strength and elastomeric properties.
