Abstract:

Carboxymethyl chitosan （CMCS）, a water-soluble derivative of chitosan, has garnered significant attention as a multifunctional biomaterial for cosmetic applications, driven by the growing consumer demand for natural and sustainable ingredients. Its performance is governed by structural parameters including substitution position, degree of substitution （DS）, molecular weight （M_w）, and degree of deacetylation （DD）. Research demonstrates the effectiveness of CMCS as an emulsifier and thickener, where its amphiphilic nature stabilizes emulsions and gels, potentially replacing traditional stabilizers like carbomer in oil-in-water systems. For moisturization, CMCS exhibits superior hygroscopicity and water retention compared to chitosan, with a performance rivaling that of hyaluronic acid. Studies confirm its antioxidant capacity through radical scavenging （against DPPH, superoxide, and hydroxyl radicals）, which is enhanced further by grafting natural antioxidants. CMCS shows significant antimicrobial activity against various pathogens, which is amplified when combined with metal oxide nanoparticles. As a delivery vehicle, it effectively encapsulates bioactive compounds like vitamin C and niacinamide for sustained release while enhancing skin permeability. In UV protection, CMCS-based high-molecular absorbers and nanocomposites substantially improve performance. Despite these advantages, critical challenges in cosmetic applications remain, such as performance inconsistencies due to uncontrolled synthesis conditions affecting structural parameters, the lack of standardized characterization in commercial products, and limited clinical validation with predominant reliance on in vitro data. Future development requires establishing quantitative structure-property relationships through precision synthesis, developing industry-wide characterization standards, generating robust human efficacy data, and advancing multifunctional CMCS composites. Addressing these gaps is crucial to unlocking the full potential of CMCS as a high-performance cosmetic ingredient.

Key words: carboxymethyl chitosan, structure-activity relationship, biocompatibility, physicochemical property, cosmetics application