Hydrogel microcontainers with tunable physical properties prepared by polyionic complexation

Abstract

Synthesis of hydrogel hollow capsules provides the opportunity to extend the applications of gel materials as carriers. We report on biocompatible poly(vinylamine) (PVAm) hydrogel hollow microcontainers derived from well-defined precursor polymer, poly(N-vinylformamide) (PNVF). Herein, PNVF particles were synthesized via dispersion polymerization, varying either of crosslinking agent concentrations or steric stabilizer concentrations with the aim of probing the key factors that facilitate hollow structure. Uniform PVAm hydrogel capsules were consecutively prepared from PNVF, provided PNVF were attained in a sufficiently cross-linked structure. Subsequently, taking advantage of protonated amine in PVAm at alkaline condition, we constructed PVAm-hyaluronic acid (HA) complexes with two descriptions of HA, possessing different molecular weight. We thus confirmed complex structures with NMR cryoporometry analysis that PVAm-short HA chain complexes (PVAm-SHA) contains denser shell structure than that of PVAm-long HA chain complex (PVAm-LHA). This, in turn, leads to the PVAm-SHA with higher stability against external stimuli, near-infrared (NIR) laser irradiation. For imparting light absorption in NIR region, we introduced gold nanorod (AuNR) to the PVAm-HA complexes. Consequently, PVAm-SHA exhibited improved durability and light stability when compared with PVAm-LHA during the local heating of AuNRs by NIR irradiation. In this study, we thus practically synthesized hydrogel hollow capsules in different size and also verified the structural change of polyion shell complexes by varying the chain length of HA, leading to enhancement of mechanical strength and light durability. As a consequence, the hollow PVAm-HA capsules developed in the present study can serve as promising microcontainers for therapeutic delivery systems.