Effective pH-regulated release of covalently conjugated antibiotics from antibacterial hydrogels

This paper describes the development of a pH-sensitive ampicillin-loaded double-network hydrogel for the local delivery of antibiotics against Gram-positive bacteria. Covalent polymerization of a cationic monomer constituted the first network, whereas imine bond formation between the aldehyde end group of Pluronic F127 (F127-CHO) and the amine of polyethyleneimine constituted the second network. The hydrogel was loaded with the antibiotic ampicillin. Ampicillin was conjugated by forming a reversible imine bond with F127-CHO, which allowed its sustained release over an extended period of time. The antibiotic's release was dependent on the initial amount of drug conjugated in the hydrogel and was greater at pH 5 than at pH 7. The hydrogel displayed excellent biocompatibility and antimicrobial activity against Gram-positive bacteria in vitro. Therefore, in the future, the proposed hydrogel could be used for in situ delivery of antibiotics in post-operative patients.