Chitosan/alginate composite porous hydrogels reinforced with PHEMA/PEI core–shell particles and pineapple-leaf cellulose fibers: their physico-mechanical properties and ability to incorporate AgNP

In this work, porous chitosan/alginate hydrogels (CS/Alg) were fabricated by the addition of two reinforcing fillers, PHEMA/PEI core–shell particles and pineapple-leaf cellulose fibers, using a freeze-drying method. At the optimum ratio and mixing conditions, the porous hydrogels obtained after freeze-drying showed an interconnected porous structure with pore size in a range of 50–100 µm and porosity in a range of 80–85%. With the incorporation of PHEMA/PEI core–shell particles and pineapple-leaf cellulose fibers, the composite hydrogels (CS/Alg/PF) maintained their structure when submerged in deionized water and acidic and basic media, with low volume shrinkage. Water adsorption reached equilibrium within 30 min, and the percentage water uptake ratios of CS/Alg and CS/Alg/PF in deionized water increased from 1165% to 1391%, largely due to the presence of pineapple-leaf cellulose fibers. However, the presence of both PHEMA/PEI particles and pineapple-leaf cellulose fibers increased the compressive modulus of the resulting hydrogels from 0.028 MPa to 0.083 MPa. Moreover, the pineapple-leaf cellulose fibers improved the storage modulus of the hydrogels as revealed by dynamic mechanical analysis. CS/Alg/PF was also utilized as a template for loading silver nanoparticles (AgNP) through a reduction reaction of silver ions at ambient temperature without the use of any additional chemical reducing agents. The physico-mechanical properties and antibacterial activity of the AgNP-loaded CS/Alg/PF hydrogels were evaluated as well.