Biodegradable thermosensitive polymer, poly(dl-lactide-co-glycolide-b-ethylene glycol-b-dl-lactide-co-glycolide) (PLGA-PEG-PLGA) is a desirable ophthalmic drug delivery system because it can be formulated into an injectable solution which forms a gel in situ to provide prolonged drug release.
The polymer molecule exhibits a hydrophilic core region and hydrophilic ends. An aqueous solution of this polymer is reverse thermosensitive, meaning it is fluid and injectable at room temperature and will rapidly form a hydrogel at body temperature (e.g. after subcutaneous injection).
The polymer is biodegradable due to the instability of ester bonds in the aqueous physiological environment. This process continues at a slow rate and will eliminate the hydrogel from the body in several weeks in a non-toxic way.