Thermoresponsive biopolymer hydrogels with tunable gel characteristics

Here we describe the design of thermosensitive biopolymer-based hydrogels with adjustable gel properties. It is demonstrated that formulations comprising predetermined contents of hydrophobically modified chitosan biopolymer with n-dodecyl groups (HC) undergo a quick fine-tunable gelation in the presence of beta-glycerophosphate disodium salt (GP) triggered by increasing temperature. In-depth rheological characterizations revealed that with increasing HC content in solutions, the gel point shifts to lower temperatures as more compact networks with considerably improved gel strength are formed. The evolution of hydrogels was also investigated by the small angle light scattering (SALS) technique. It was realized that the incorporation of HC chains induce a gel to be accomplished through formation of smaller but more homogenous microdomains with the aid of pendant hydrophobic moieties in the lower temperature range. Moreover, time sweep rheological characterization of the thermogelling systems disclosed that the gelation process proceeds faster in the presence of HC chains. The Fredrickson-Larson (F-L) theory was implemented as an alternative approach to determine the gel point. In view of the obtained results which were consistent with the classical Winter-Chambon theory, the F-L theory can be proposed as a robust and less tedious method to precisely determine the gel point in such systems. The developed hydrogels can be proposed as promising injectable matrices with predetermined gel features for various biomedical applications.