Physico-chemical characteristics of dialdehyde carboxymethylcellulose/sericin graft copolymer

In recent years, increasing attention has been directed toward the application of natural polymers in fields such as biomedicine, pharmaceuticals, and dermatology, owing to their biocompatibility, biodegradability, and functional versatility. Among these, polysaccharides and proteins have emerged as dominant candidates for biomedical use, as they are inherently non-toxic to human tissues. In particular, proteins such as sericin have demonstrated the ability to support skin regeneration and healing, making them highly attractive for therapeutic applications. In this study, we synthesized a graft copolymer based on silk sericin and dialdehyde carboxymethyl cellulose (DCMC) and systematically investigated its physicochemical properties. The formation of covalent bonds between DCMC and sericin was confirmed using both Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) analysis. The cross-linking was achieved through a Schiff base reaction, where the aldehyde groups of DCMC reacted with the free amino groups of sericin under controlled conditions (temperature: 60 °C, pH: 5.5, reaction time: 1 h, and reactant ratio: 1:1). The degree of cross-linking in the resulting copolymer was determined to be approximately 86.2%. Given the importance of water absorption and interaction with biological fluids in biomedical materials, we investigated the sorption behavior of the synthesized DCMC/sericin graft copolymers. These materials exhibited a high water vapor sorption capacity, reaching up to 13 mmol/g at an optimal DCMC-to-sericin ratio of 1:1. Additionally, the polymer–solvent interaction was evaluated through the analysis of capillary-porous structures and the calculation of capillary radii for DCMC, sericin, and their graft copolymers. The Gibbs free energy of sorption for the DCMC/sericin samples was calculated and found to be approximately − 19 kJ/mol, indicating favorable interactions with aqueous media compared to the individual components. Furthermore, rheological analysis revealed that the storage modulus (G′) of the DCMC/sericin graft copolymers exceeded the loss modulus (G″), suggesting a predominantly gel-like behavior. This rheological profile supports the potential of the synthesized copolymers to be processed into gels, films, powders, and sponge-like structures, thereby broadening their applicability in wound dressings, tissue scaffolds, and other biomedical formulations.