Fabrication and controlled release behavior of metal-polyphenol-decorated alginate hydrogel beads.
Hydrogel-based controlled release systems are widely used in pharmaceutical and agricultural fields. To achieve controlled release of hydrophilic drugs, which otherwise release rapidly through hydrated polymer networks, we developed a facile ferric ion co-crosslinking strategy to fabricate composite hydrogel beads. The highly porous composite hydrogel beads were prepared by blending recycled household formaldehyde adsorbent (RFA) with sodium alginate (Alg) at a 1:1 (w/w) ratio, followed by Fe3+-induced crosslinking and subsequent surface functionalization with tannic acid (TA). Through altering the Alg hydrogel structure, RFA enabled the hydrogel to synergistically restrict drug molecules, and coupled with the blocking function of MPC, this composite structure provided effective regulation of water-soluble drug molecule release. The carrier demonstrated pronounced swelling and disassembly of the metal-polyphenol microfilm, resulting in rapid GV release under alkaline pH conditions. In acidic environments, the conversion of ternary metal-polyphenol complexes into double or single complexes weakened the "on-off" effect, thereby accelerating GV release compared to neutral conditions. The release of GV was governed by combination of diffusion-controlled processes and progressive hydrogel bead relaxation. Additionally, the carrier exhibited no detectable toxicity in murine fibroblast cells and rice seed germination, indicating its favorable biosafety. These findings demonstrated that the controlled-release system had potential to be further explored for environmental protection and hazardous substance management.