Chiang Mai Journal of Science

     This study explored the effects of synthesis parameters such as chitosan molecular weight, alginate loading, and crosslinker loading in optimizing chitosan-alginate hydrogel using response surface methodology prepared by ionotropic gelation. Box-Behnken design evaluated the effects of chitosan molecular weight, alginate loading (2.5 to 4.5 wt%), and crosslinker loading (0.10 M to 1.00 M) on encapsulation efficiency, swelling behaviour and urea release. The hydrogels were spherical and with a mean diameter of 3.82 ± 0.78 μm. FTIR analysis confirmed the interactions between chitosan, alginate and crosslinker added. Encapsulation efficiency was maximized at 89.43 ± 12.66%, with alginate concentration (3.5 wt%) being the most significant factor (p = 0.001264). Higher alginate concentrations improved encapsulation by facilitating crosslinking with Ca²⁺ ions. Swelling studies revealed an average swelling capacity of 33.27 ± 17.26%, peaking at 77%. Urea release over 2 hours averaged 20.08 ± 16.39%, with minimal release observed in formulations using lower molecular weight chitosan and moderate alginate concentrations (p = 0.01535). Statistical models indicated high adequacy for encapsulation efficiency (R² = 0.844) but limited predictive power for swelling (R² = 0.4987). The findings demonstrated the influence of formulation variables on hydrogel properties, underscoring their potential as nutrient delivery systems with controlled release and swelling behaviour.