LbL films and microcapsules based on protamine and pectin-Ag nanocomposite

Abstract

Nanocomposites based on silver nanoparticles and biopolymers are promising materials for biomedical applications due to their antimicrobial potential. This work aimed to design layer-by-layer (LbL) films and microcapsules based on pectin-Ag nanocomposite (AgNC) and protamine (PtS) suitable for antimicrobial surface protection and theranostic applications. Biocompatible AgNC with strong antimicrobial properties was previously synthesized by the «green» chemistry method. The physico-chemical properties of (PtS/AgNC)n multilayers were investigated by quartz crystal microbalance (QCM) and atomic force microscopy (AFM) methods. (PtS/AgNC)n multilayers were also tribologically tested. It was determined that LbL-films formed from aqueous solutions of polymers are elastic (μ = 1.06 MPa) and have a thickness of 67.1 ± 9.3 nm, while using of polymer solutions in 0.15 M NaCl resulted in the formation of more viscous (μ = 0.31 MPa) films with a thickness of 410.8 ± 88.4 nm. We have also designed (PtS/AgNC)n microcapsules (MCs) based on the same biopolymers. For MCs fabrication, polymers had been layered on the 5 μm CaCO3 core, which was subsequently dissolved by HCl. We also demonstrated that MCs are suitable for incorporating cationic photosensitizer methylene blue. To perform in vivo biodistribution experiments, the surface of MCs was modified by 1) arginine residues (NH2 -groups) of protamine layer exposed on the surface of MCs from under the AgNC layer using Cy5.5 NHS ester and 2) carboxylic groups of the terminal pectin layer using Cy5.5 amine derivative and EDC/NHS coupling reaction. Due to the abundance of carboxylic groups on the surface, the MCs modified by Cy5.5 amine derivative had stronger fluorescence emission compared to MCs modified by Cy5.5 NHS ester. The new Cy5.5-MCs are to be tested for in vivo biodistribution in the future.