Designing highly tunable nanostructured peptide hydrogels using differential thermal histories to achieve variable cellular responses

In this study, we demonstrate a unique and promising approach to access peptide-based diverse nanostructures in a single gelator regime that is capable of exhibiting different surface topographies and variable physical properties, which, in turn, can effectively mimic the extracellular matrix (ECM) and regulate variable cellular responses. These diverse nanostructures represent different energy states in the free energy landscape, which have been created through different self-assembling pathways by providing variable energy inputs by simply altering the gelation induction temperature from 40 °C to 90 °C. The highly entangled network structure with long fibers was created by higher energy inputs, i.e., inducing the gelation at a higher temperature in the 70-90 °C range, whereas the less entangled nanoscale network with short fibers was obtained at a lower gelation induction temperature of 40-60 °C. It is worth mentioning that the highly entangled network structures with long fibers can be easily obtained by heating the less ordered structure, as evidenced by the thermoreversibility study. In addition, tuneable mechanical properties were achieved by merely adjusting the self-assembly pathways; the gels formed at high gelation induction temperatures showed high mechanical strengths in contrast to the gels formed at low gelation induction temperatures. Further, a detailed comparison was made with one of the important ECM proteins, i.e., collagen, to elucidate the potential of the hydrogels in mimicking the structural and mechanical properties of ECM. Interestingly, the highly entangled network structures with long fibers enhanced cellular survival as well as adhesion, comparable to that of the collagen gel, while a considerable proportion of cells were unable to adhere to the less entangled structures with short fibers. Such diverse nanostructures in a single gelator regime can be instrumental in controlling different cellular behaviours and could further pave the path for the development of responsive biomaterials.