Thermo-responsive hydrogels from hyaluronic acid functionalized with poly(2-alkyl-2-oxazoline) copolymers with tuneable transition temperature

Hyaluronic acid (HA) based thermo-responsive physical hydrogels were obtained through a one-pot functionalization of HA of different molar masses (from 38 to 990 kg mol(-1)) with thermo-responsive poly(2-isopropyl-2-oxazoline)-co-poly(2-n-butyl-2-oxazoline) (PiPrOx-co-PnBuOx) copolymers. The cloud point (T-cp) of PiPrOx-co-PnBuOxs varied according to their monomeric composition. The functionalized HA's thermo-responsiveness was characterised through rheology and UV-vis spectrophotometry. The hydrogel transition temperature could notably be modified in a controlled way by varying the comonomers ratio in the graft, with the crossing temperature of storage modulus G' and loss modulus G '' being found to rise by about 1 degrees C when increasing the iPrOx unit content within the PiPrOx-co-PnBuOx grafted copolymer by 1% for a series of modified 990 kg mol(-1) HA. The thermal transition of the material from room temperature to 37 degrees C was found out to be almost instantaneous, which is interesting for applications in injectable systems.