Injectable Pasty Biodegradable Polyesters Derived from Castor Oil and Hydroxyl-Acid Lactones

Pasty polymers offer a platform for injectable implants for drug delivery. A library of biodegradable pasty polymers was synthesized by bulk ring-opening polymerization of lactide, glycolide, trimethylene carbonate, or caprolactone using castor oil or 12-hydroxy stearic acid as hydroxyl initiators and stannous octoate as the catalyst. Some of the polymers behaved as Newtonian liquids. Pasty polymers of poly(caprolactone) and poly(trimethylene carbonate) were stable under physiologic conditions for over 1 month in vitro, whereas polymers of poly(lactic- -glycolic acid) degraded within 10 days. These pasty polymers offer a platform for pasty injectable biodegradable carriers for drugs and fillers. SIGNIFICANCE STATEMENT: New injectable pasty, in situ forming drug delivery systems are described and are advantageous due to their ease of administration, tunable viscosity, and biodegradability. Polyesters based on lactide, glycolide, trimethylene carbonate, and caprolactone, which are commonly used as absorbable implants and drug carriers, were conjugated onto natural hydroxyl fatty acids. These polymers have potential use as wrinkle fillers and drug carriers.