Peptide-PNIPAAm conjugate based hydrogels: synthesis and characterisation

Thermo-responsive PNIPAAm rich hydrogels with controllable properties have been prepared by introducing small quantities of peptide-PNIPAAm bioconjugates where the peptide self-assembled into a beta-sheet rich fibrillar network. This was achieved in a one pot synthesis using a thiol-modified peptide as the chain-transfer agent in the free radical polymerisation of NIPAAm. Varying the quantity of modified peptide offered control over the composition of the polymer/conjugate mixture; the higher the peptide concentration, the higher the fraction of conjugate present within the mixture and the greater the degree of aggregation of the PNIPAAm formulations. Once above a critical concentration transparent, doubly thermo-responsive hydrogels formed and the elastic modulus was proportional to the concentration of peptide present. When heated, the hydrogels exhibited an LCST transition due to the PNIPAAm and the temperature was not influenced significantly by the conjugate present, nor the gelled state of the sample. Materials with such controllable thermal and mechanical properties may have great potential to be used in numerous regenerative medical applications.