We present a detailed characterization of fibronectin (FN) adsorption and cell adhesion on poly(ethyl acrylate) (PEA) and poly(methyl acrylate) (PMA), two polymers with very similar physicochemical properties and chemical structure, which differ in one single methyl group in the lateral chain of the polymer. The globular solution conformation of FN was retained following adsorption onto PMA, whereas spontaneous organization of FN into protein (nano) networks occurred on PEA. This distinct distribution of FN at the material interface promoted a different availability, measured via monoclonal antibody binding, of two domains that facilitated integrin binding to FN: FNIII10 (RGD sequence) and FNIII9 (PHSRN synergy sequence). The enhanced exposure of the synergy domain on PEA compared to PMA triggered different focal adhesion assemblies: L929 fibroblasts showed a higher fraction of smaller focal plaques on PMA (40%) than on PEA (20%). Blocking experiments with monoclonal antibodies against FNIII10 (HFN7.1) and FNIII9 (mAb1937) confirmed the ability of these polymeric substrates to modulate FN conformation. Overall, we propose a simple and versatile material platform that can be used to tune the presentation of a main extracellular matrix protein (FN) to cells, for applications than span from tissue engineering to disease biology.

Simultaneous integration of photon emission and biocompatibility into nanoparticles is an interesting strategy to develop applications of advanced optical materials. In this work, we present the synthesis of biocompatible optical nanocomposites from the combination of near-infrared luminescent lanthanide nanoparticles and water-soluble chitosan. NaYF4:Yb,Er upconverting nanocrystal guests and water-soluble chitosan hosts are prepared and integrated together into biofunctional optical composites. The control of aqueous dissolution, gelation, assembly, and drying of NaYF4:Yb,Er nanocolloids and chitosan liquids allowed us to design novel optical structures of spongelike aerogels and beadlike microspheres. Well-defined shape and near-infrared response lead upconverting nanocrystals to serve as photon converters to couple with plasmonic gold (Au) nanoparticles. Biocompatible chitosan-stabilized Au/NaYF4:Yb,Er nanocomposites are prepared to show their potential use in biomedicine as we find them exhibiting a half-maximal effective concentration (EC50) of 0.58 mg mL–1 for chitosan-stabilized Au/NaYF4:Yb,Er nanorods versus 0.24 mg mL–1 for chitosan-stabilized NaYF4:Yb,Er after 24 h. As a result of their low cytotoxicity and upconverting response, these novel materials hold promise to be interesting for biomedicine, analytical sensing, and other applications.