Cyclopropenium-Based Biodegradable Polymers

Cationic polymers offer a wide range of potential biomedical applications. Often, these materials suffer from a lack of degradability under biological conditions, preventing their translation in vivo. We present herein the synthesis and characterization of a series of novel biodegradable polymers bearing cationic cyclopropenium along a polyester backbone, either linear or cross-linked. The polymers are synthesized stepwise via the reaction between diol-functionalized tris(amino)-cyclopropenium (TAC) monomers and diacyl chlorides. Incorporation of the TAC moiety with a permanent, pH-independent charge, and hydrophobic groups with sufficient bulkiness causes the polyelectrolyte to form an aqueous dispersion of nanoparticles with a positive surface charge. Smaller hydrophobic TAC substituents inhibit nanoparticle formation because of a lack of hydrophobic bonds within the core of the nanoparticle. The polymers undergo hydrolytic degradation and swell significantly, displaying an important framework for the drug-delivery capabilities of a hydrolytically degradable cationic polyester. One polymer displayed potent antimicrobial activity against Staphylococcus epidermidis. These polymers may have use for the delivery of anionic bioactive agents.