Nanostructured Films Exhibiting Multiple Stimuli Responsive Behavior and Improved Cell Adhesion for Tissue Engineering

Introduction. The design of smart and nanostructured surfaces has allowed to achieve significant advances in tissue engineering. Emphasis has been given to layer-by-layer (LbL) adsorption of polymers for being a simple and versatile technique. In this study, we report the use of chitosan and an elastin-like recombinamer (ELR) containing RGD to produce such nanosctructured multilayers. ELRs are smart genetically engineered

polypeptides which allow conceiving ultrathin films with biologically relevant sequences.

Methods. The buildup of chitosan/ELR-RGD films was monitored using a quartz-crystal microbalance. Their

wettability and smart properties were studied by contact angle measurements as a function of temperature, pH and ionic strength. The topography was observed by AFM. SaOs-2 cell adhesion was also studied in vitro.

Results. Chitosan and ELR-RGD films were constructed based on electrostatic and hydrophobic interactions. Contact angle measurements revealed cyclic, acute and independent wettability changes around stimuli transition values of 50 ºC, pH 11, and ionic strength of 1.25 M. Below each transition value, the surfaces were moderately hydrophobic. Above, they acquired an extremely hydrophilic character. The transition was also evident in the topography changes, becoming rougher with increasing pH. SaOs-2 cells showed increased adhesion and activity for films ending with ELR-RGD ending films, comparing to chitosan and a nonfunctional ELR-RDG peptide.

Conclusion. This work demonstrates the potential to use natural and recombinant macromolecules to engineer multilayered and nanostructured surfaces, which can be further extrapolated to more complex devices. The potential of this work can stimulate the development of other similar biomedical products processed through LbL for pharmaceuticals delivery and structures for tissue engineering.