Immobilization of fibronectin in chitosan substrates improves cell adhesion and proliferation

Covalent grafting of biomolecules is a strategy to improve the biocompatibility and bioactivity of materials. However, it is critical to maintain the biological activity of the biomolecule upon its attachment to the surface. In the present study we compared the biological properties of chitosan, in which the surface was enriched with fibronectin (Fn), using two methodologies: chemical immobilization, using a water-soluble carbodiimide; and simple adsorption. X-ray photoelectron spectroscopy studies confirmed the successful immobilization of Fn onto modifiedmembranes. SaOs- 2 cells were seeded onto these surfaces to assess the biological consequences of such modifications. The presence of Fn stimulated cell adhesion on chitosan. It was found that after 7 days of culture in the presence of covalently attached Fn, the cells are confluent; significantly fewer cells were detected in unmodified film and in film with adsorbed Fn. This result is consistent with the fact that considerable desorption of Fn from chitosan takes place within 24 h in culture medium. This study showed that Fn may be easily covalently attached onto chitosan substrates, improving the biological performance of the material. The technique could find applications in tissue-engineering strategies, as the surface modification of chitosan-based substrates could be carried out in more complex geometries, such as in scaffolds or particles

Electrospray deposition in vacuum as method to create functionally active protein immobilization on polymeric substrates

We demonstrate in this work the deposition of a large biological molecule (fibronectin) on polymeric substrates in a high vacuum environment using an electrospray deposition system. Fibronectin was deposited and its distribution and structure investigated and retention of function (ability to promote cell adhesion) on return to liquid environment is shown. AFM was used to monitor changes in the morphology of the surface before and after fibronectin deposition, whilst the biological activity of the deposited protein is assessed through a quantitative analysis of the biomolecular adhesion and migration of fibroblast cells to the modified surfaces. For the first time we have demonstrated that using high vacuum electrospray deposition it is possible to deposit large protein molecules on polymeric surfaces whilst maintaining the protein activity. The deposition of biological molecules such as proteins with the retention of their activity onto clean well-controlled surfaces under vacuum condition, offers the possibility for future studies utilizing high resolution vacuum based techniques at the atomic and molecular scale providing a greater understanding of protein–surface interface behaviour of relevance to a wide range of applications such as in sensors, diagnostics and tissue engineering

Experimental and computational examination of anastellin (FnIII1c)-polymer interactions

Using a combination of experimental and computational approaches, the interaction between anastellin, a recombinant fragment of fibronectin, and representative biomaterial surfaces has been examined. Anastellin and superfibronectin have been seen to exhibit antiangiogenic properties and other properties that may make it suitable for consideration for incorporation into biomaterials. The molecular interaction was directly quantified by atomic force microscope (AFM)-based force spectroscopy, complemented by adsorption measurements using quartz crystal microbalance (QCM). Using AFM, it was found that the anastellin molecule facilitates a stronger adhesion on polyurethane films (72.0 pN nm?1) than on poly (methyl methacrylate) films (68.6 pN nm?1). However, this is not consistent with the QCM adsorption measurements, which show no significant difference. Molecular dynamics simulations of the behavior of anastellin on polyurethane in aqueous solution were performed to rationalize the experimental data, and show that anastellin is capable of rapid adsorption to PU while its secondary structure is stable upon adsorption in water