Oligosaccharides and oligosaccharide-based noble metal nanoparticles: From preparation to biomedical applications

Oligosaccharides are increasingly valuable for preparing noble metal (NM) nanoparticles (NPs) due to excellent biocompatibility and abundant reducing functional groups (e.g., hydroxyl, amino, and aldehyde groups). High polarity oligosaccharides can be directly extracted using polar solvents. Cavitation, thermal effects, and free radicals can break down long-chain polysaccharides into shorter chains, yielding mixed oligosaccharides with low molecular weight polysaccharides as by-products. To further depolymerize polysaccharides into oligosaccharides, oxidizing agents (e.g., acids and hydrogen peroxide) are used to degrade the polysaccharides sufficiently to obtain oligosaccharides. Furthermore, enzymatic degradation minimizes structural damage to the products due to its specificity for glycosidic bonds, making it a widely favored method for preparing structurally specific oligosaccharides. More importantly, amino, hydroxyl, and aldehyde groups in oligosaccharides can be involved in reducing highly stable NM NPs. Notably, oligosaccharide-based NM NPs exhibit tumor-specific accumulation capabilities due to their inherent targeting properties, with accumulation levels at tumor sites 2-3 times higher than those of non-targeted particles. Furthermore, their surface functional groups enable efficient conjugation with drugs and immunomodulatory molecules. Additionally, the photothermal conversion efficiency is over 130 % higher than that of traditional photothermal therapeutic agents. They demonstrate significant potential in biomedical applications, including antibacterial therapy, cancer diagnosis, and treatment.