Thermoresponsive gelators as advanced materials for topical medicines

Abstract: Topical drug delivery to sites such as the vagina, rectum, and eye, is a necessity for eliciting local effects and offers enhanced systemic bioavailability when a drug is subject to extensive presystemic metabolism. However, retention at these sites is poor. One potential approach to enhance retention is by use of in situ gelators which transition from a liquid to gel when warmed by the body. ABA triblock copolymers composed of thermoresponsive blocks (A) and poly(ethylene glycol) (B) have been explored as thermoresponsive gelators for topical drug delivery. The class of thermoresponsive bock and molecular weight greatly impacts the rheological behaviour of the polymers in solution, which has been related to nanostructure of the systems by Small-Angle Neutron Scattering. Synthetic materials of this type have been demonstrated to have significant advantages over the commercially-available poloxamers, exhibiting tight control over gelation temperatures, greater resistance to dissolution, improved adhesion, and the ability to elicit sustained delivery of drugs relevant to topical medicines over several days.