Interactions of cross-linked and uncross-linked chitosan hydrogels with surfactants for biomedical applications

Abstract

The swelling equilibrium of Chitosan and sodium tripolyphosphate (NaTPP) cross-linked chitosan hydrogels in  aqueous solutions of surfactants differing in structure and hydrophobicity at 25⁰C is reported. Anionic
surfactant sodium dodecylsulfate (SDS), the cationic surfactant hexadecyltrimethylammonium bromide (HTAB) and neutral surfactants Triton X-100 were employed. The surfactants induced abrupt change in the gel volume. The equilibrium swelling ratio first decreased sharply as the concentration of the surfactant increased and remained almost constant up to the critical micelles concentration (CMC) of the surfactants and then
increased again as the concentration increased above the CMC of the surfactants used. The equilibrium volume change of hydrogel was significantly increased from HTAB > Triton X-100 > SDS> the mixed SDS/Triton X- 100 system. A decrease in equilibrium swelling ratio of the gel in SDS/TX-100 mixtures was observed with an increase in the mole ratio of SDS. The results also revealed that cross-linking with 3% or 5% w/v NaTPP exhibited lower equilibrium swelling values. This swelling study showed that cross-linking density, surfactant type, and their respective concentrations were important parameters that could affect equilibrium swelling of chitosan gel. Structural elucidation of the nanocomposites was monitored using Infra-red Spectroscopy (IR), and X-Ray Diffractography (XRD).

Keywords: Chitosan Hydrogel, Surfactants, Swelling Equilibrium and Hydrophobicity