High Water Content Physically Cross-linked Hybrid Hydrogels Based on Polyester Dendrimers and Cellulose Nanofibrils: A Comprehensive Study

Structurally perfect cationic polyester dendrimers based on 2,2 dimethylolpropionic acid (bis-MPA) were exploited in combination with anionic cellulose nanofibrils (CNFs) in the fabrication of a comprehensive library of electrostatically cross-linked hybrid hydrogels. Three distinct families of cationic bis-MPA dendrimers ranging from first to third generation were used, displaying up to 24 peripheral ammonium groups. The dendrimer families covering different hydrolytic stability and peripheral ammonium groups, beta-alanine, cysteamine hydrochloride, and N,N-dimethylcysteamine hydrochloride were chosen as ammonium groups. The self-assembly process occurred spontaneously without external stimuli, resulting in well-organized and self-supporting hydrogels. The water content of the hydrogels reached values up to 99.6 wt % with a storage modulus ranging from 1.2 to 3.0 kPa which is within the range of skin tissue. The antibacterial activity of the dendrimers and the formed hydrogels was evaluated against Gram-negative and Gram-positive bacteria strains, and the cytotoxicity was determined by measured cell viability prevention of diverse cell lines. The hydrogels based on TMP-G1-[Cys](6) exhibited the highest antibacterial activity without showcasing toxicity. To demonstrate its effectiveness, the hydrogel was freeze-dried, resulting in a porous aerogel that exhibited significantly greater antibacterial activity than commercially available band-aids.