Mollusk shells as marine bioactive materials: Composition, bioactivities, and prospects for food and health applications.

Marine mollusk processing generates large quantities of shells that serve as abundant but underutilized biofunctional materials. Composed mainly of calcium carbonate with a minor organic matrix of proteins, polysaccharides, and chitin, mollusk shells exhibit characteristic activities such as antioxidant, anti-inflammatory, antimicrobial, osteogenic, hepatoprotective, gastrointestinal protective, and neuroprotective effects. These functions support their potential use as natural calcium sources, food preservation agents, functional ingredients, and biocompatible materials for tissue engineering and drug delivery. Safety concerns-particularly heavy metals and microplastics-are critically assessed alongside current mitigation approaches. Overall, current evidence supports MMSs as promising marine biomaterials with broad food and health applications. Persistent challenges include limited mechanistic understanding, species-dependent variability, and the lack of standardized processing and toxicological frameworks. Addressing these gaps will enable the safe and sustainable utilization of mollusk shells as high-value marine biomaterials.