Modelling of water absorption kinetics and biocompatibility study of synthesized cellulose nanofiber-assisted starch-graft-poly(acrylic acid) hydrogel nanocomposites

To prepare superabsorbent hydrogels, starch-graft-poly(acrylic acid) reinforced by cellulose nanofibers (CNF), was synthesized through free radical graft polymerization. The results of its biocompatibility tests exhibited that by increasing incubation time from 1 to 5 days, the numbers of living cells were increased on both reinforced and unreinforced hydrogels. However, the fraction of cells on the surfaces of the reinforced hydrogel is comparable to unreinforced samples. The swelling amounts in NaCl, CaCl2, and AlCl(3)solutions were 193 +/- 9, 110 +/- 8, and 99 +/- 7 (g(water)/g(absorbent)) for 5 wt% CNF-reinforced hydrogels and 109 +/- 8, 62 +/- 7, and 56 +/- 6 (g(water)/g(absorbent)) for unreinforced hydrogels, respectively. Compressive strength and Young's modulus of 5 wt% CNF-assisted hydrogels were also 63.3 and 31.6 kPa corresponding to 69% and 140% improvements compared with unreinforced one. The graft polymerization of acrylic acid monomer was controlled by monomer content and cross-linking percentage, in order to achieve the highest swelling capacity for hydrogels. Hydrogel swelling in water was 312 g(water)/g(absorbent) for unreinforced hydrogel and 523 g(water)/g(absorbent) for 5 wt% CNF-reinforced sample and water absorption kinetics results was in agreement with the pseudo-second-order model. The prepared CNF-reinforced starch-graft-poly(acrylic acid) hydrogels can be used in a wide range of medical application due to the enhanced hydrophilicity, mechanical strength, and biocompatibility. Graphic abstract