Nanoparticles based on a PEGylated methacrylate copolymer as vehicles for hydrophilic antimicrobial additives: a study on chemical interactions with a benzoic acid probe molecule

Release systems for bioactive compounds have been increasingly developed in various fields, such as pharmacy, agriculture, food and cosmetics. The most challenging stage in the implementation of these technologies is the selection of vehicles because they must efficiently encapsulate active principles without altering their activity and allow their controlled release. Herein, we report the synthesis of a poly(ethylene glycol)-block-poly(2-dimethylaminoethyl methacrylate-co-(butyl methacrylate-co-methyl methacrylate)) via atom transfer radical polymerisation at a molar ratio of methacrylic monomers of 2:1:1. The copolymer was evaluated as a precursor in the fabrication of nanostructured vehicles for benzoic acid used as a probe molecule. Infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy showed that benzoic acid and the copolymer interacted through the formation of hydrogen bonds that involved amine groups on 2-dimethylaminoethyl methacrylate units and the carboxylic acid group. Polymer particles loaded with benzoic acid prepared via a modified nanoprecipitation method exhibited average diameters shorter than 200 nm. They were positively charged and colloidally stable in a pH range of 5.0 to 8.0. With these nanoparticles, benzoic acid achieved a controlled release.