Dual-Janus Hydrogel Composite for Moisturizing and Antimicrobial Conservation of Bone Relics

Bone relics are a subset of cultural heritage, providing invaluable insight into the annals of human civilization. Conservation of unearthed bone relics is imperative, as they are susceptible to damage from environmental changes such as desiccation and microbial attack. However, current conservation methods lack materials that simultaneously provide moisturization and microbial protection. Herein, we propose a dual-Janus polyacrylamide (PAM) hydrogel composite that integrates brominated isobutylene isoprene rubber (BIIR) and polydimethylsiloxane (PDMS) elastomer, named BIIR–PAM-PDMS (BPP). This composite features a three-layer structure that uniquely addresses both critical preservation needs: the PAM hydrogel serves as a vehicle for delivering water to the ivory through the PDMS layer while BIIR seals in moisture over an extended period; meanwhile, the strategic integration of chlorhexidine digluconate (CD) and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) within PDMS and PAM layers, respectively, effectively inhibits the proliferation of bacteria and fungi on the ivory surface. Tackling the challenge of layer separation due to incompatibility between hydrophobic elastomers and hydrophilic hydrogel, the interaction between PAM and water is disrupted by introducing glycerol, releasing more PAM chains to interact with BIIR by polar interactions and PDMS by hydrogen bonds, thus enhancing the interface adhesion. Applied to the conservation of ivory from Sanxingdui, the BPP composite demonstrates superior capabilities in moisture retention, microbial inhibition, and morphology maintenance for the unearthed ivory over 130 days, showcasing a promising preservation paradigm for bone heritage artifacts.