Functional self-healing aldehyde-derived nanoparticle-crosslinked gelatin/PNIPAm-based adhesive gels†

Abstract

The combination of lower critical solution temperature (LCST) and upper critical solution temperature (UCST) polymers provides varying dissolution to the system, with tunable physiochemical properties. In the current work, injectable, fluorescent, and thermo-responsive poly-N-isopropylacrylamide (PNIPAm)-gelatin nanocomposite gels were prepared by combining non-covalent interactions and Schiff base chemistry. The incorporation of aldehyde-based nanoparticles (2.5–10%) facilitated the crosslinking of the matrix via the formation of imine linkages with gelatin, which significantly reduced the pore size of the gels from 30–40 micron to 4–5 μm. The temperature-dependent viscoelastic properties showed that the storage modulus increased significantly above 40 °C, which confirmed the thermosensitive behaviour of the gels owing to the combined effect of PNIPAm and gelatin. Higher storage modulus over loss modulus for all crosslinked gels indicates the elastic behaviour of the gels. The introduction of imine linkages offered instant self-healing features and the nanoparticles provide photoluminescence to the polymeric gel system. Furthermore, the tackiness offered by gelatin enhances the adherence to human skin and the gels are found to be biocompatible towards fibroblast cell lines (L929) and are promising for drug delivery systems, injectable materials, and optically trackable adhesives. The findings provide new insights into the multifunctional properties of thermoresponsive PNIPAm-gelatin nanocomposite gels with dynamic imine linkages for biological applications.