Biocompatible noisy nanotopographies with specific directionality for controlled anisotropic cell cultures

All cells are exposed to extra-cellular physical stimuli determined by the details of the micro-/nano-environment within which they exist. These stimuli are present in organs and tissues where specific directional signals coexist with biotopographical noise (e.g. cellular debris, residues of apoptotic cells , protein accumulation, sclerotic plaques). Here, we present a platform for the investigation of the impact of this noise based on nanostructured plastic scaffolds with a controlled level of anisotropy. Two different types of topographical noise are introduced into fully ordered nanostructures . Starting from nanogratings, we randomly introduce nanomodifications, whose density determines the overall substrate directionality. A general quantitative definition of directionality is discussed and applied to our nanostructures . Substrate biocompatibility is assayed by culturing PC12 cells and evaluating cell viability and NGF-induced neuronal-differentiation efficiency. The suitability for high-resolution microscopy on living cells is demonstrated by visualizing focal adhesion complexes by total internal reflection fluorescence (TIRF) microscopy . Finally, we show the impact of noise in modulating focal adhesion maturation in PC12 cells upon NGF-induced neuronal differentiation. Our results indicate design rules both for biocompatible textured substrates allowing the study of cell -environment interaction in vitro and for tissue engineering applications.