Thermo-chemical modification to produce citric acid–yeast superabsorbent composites for ketoprofen delivery
Owing to their unique physicochemical/biological properties and natural abundance, native yeast microbes were used to prepare a novel eco-friendly superabsorbent composite through thermo-chemical modification of yeast with citric acid in semi-dry conditions. The structure and morphology of the as-produced citric acid–yeast superabsorbent composites were characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The surface characteristics were studied systematically, including carboxyl content, degree of esterification, degree of substitution and zeta potential. The detailed formation mechanism was proposed. The evaluation of equilibrium welling showed that the species were able to absorb up to 38 times their weight in distilled water, and the water absorption capacity was affected by reaction temperature and external solution (the charge number, salt concentration and pH value). The results implied that citric acid–yeast superabsorbent composites exhibited enhanced water absorption, salt tolerance and pH sensitivity. The excellent swelling performance and special functional groups allowed the citric acid–yeast composites to target drug delivery. Ketoprofen, as a model drug, was utilized to monitor the loading and cumulative release efficiency to evaluate the suitability of citric acid–yeast composites as drug carriers. Its pH-sensitivity, biocompatibility and degradability make it a potential candidate for drug delivery.