Fabrication of rod-like nanocapsules based on polylactide and 3,4-dihydroxyphenylalanine for a drug delivery system

Abstract

3,4-Dihydroxyphenylalanine (DOPA) has the property of self-polymerization to form a PDOPA polymer with crosslinking structure, and coats onto surfaces of diverse substrates at alkaline pH values. In this study, rod-like nanocapsules were facilely fabricated based on a bio-based polymer by taking advantage of the DOPA properties. A block-like poly(lactide)-b-amidated poly(3,4-dihydroxyphenylalanine) (PLA-b-APDOPA) copolymer was firstly synthesized through an amidation reaction with pre-prepared functional PLA and APDOPA. The DOPA compound and obtained PLA-b-APDOPA copolymer were subsequently coated onto the silica nanorods to get PLA-b-APDOPA/PDOPA@SiO₂ nanorods. Afterwards, PLA-b-APDOPA/PDOPA nanocapsules were formed by removal of the silica template. The structure of the copolymer was confirmed by a ¹H NMR spectrum. The formed nanorods and nanocapsules were observed by SEM and TEM. The structure and amount of the coated layers were determined by XPS and TGA. The results showed a rough surface of the nanorods after being coated with the polymers and the formation of a thin PDOPA layer and a thick PLA-b-APDOPA layer on the silica surface. Moreover, the formed nanocapsules had good biocompatibility. A model drug was successfully entrapped into the capsules, and could be slowly released from the nanocapsules in vitro depending on the pH buffer. The obtained rod-like nanocapsules could be used as carriers in biomedical fields.