Study of double network hydrogels based on sodium methacrylate alginate and carboxymethyl chitosan

[Display omitted] •Double network hydrogel was formed by covalent and physical crosslinking successively.•The distribution of polyelectrolyte complexes was regulated by covalent crosslinking.•The compressive strength and light transmittance were significantly improved by PEGDA.•The drug release behavior was pH sensitive and correlated with the content of PEGDA. Based on sodium methacrylate alginate (MASA) and carboxymethyl chitosan (CMCS), double network (DN) hydrogels were formed by covalent crosslinking and physical crosslinking in succession. Covalent crosslinking was achieved by using poly(ethylene glycol) diacrylate (PEGDA) as the crosslinker and initiated by ammonium persulfates, while physical crosslinking was realized by the electrostatic interactions between the carboxyl group of MASA and the amino group of CMCS induced by acetic acid atmosphere. With the addition of PEGDA (1.25 wt% of mixture solution), the compressive strength of hydrogel was increased from 9.0 kPa to 73.3 kPa. Compared with the physically cross-linked hydrogels, the light transmittance of the DN hydrogels at 600 nm was significantly increased from 23.7% to 93.8%. The drug release studied by taking berberine hydrochloride hydrate (Ber) as the model drug showed that drug release behaviors of the DN hydrogels were pH sensitive and notably correlated with the content of PEGDA. In addition, DN hydrogels existed excellent water absorption rate (38.3-fold). Therefore, the enhanced mechanical properties, high transparency, excellent water absorption rate, and pH sensitivity of the DN hydrogel suggested the promising applications of the hydrogels as visual transdermal drug delivery systems.