Elena Martines

A parallel-plate flow chamber to study initial cell adhesion on a nanofeatured surface

Cells in the human body come across many types of information, which they respond to. Both material chemistry and topography of the surface where they adhere have an effect on cell shape, proliferation, migration, and gene expression. It is possible to create surfaces with topography at the nanometric scale to allow observation of cell-topography interactions. Previous work has shown that 100-nm-diameter pits on a 300-nm pitch can have a marked effect in reducing the adhesion of rat fibroblasts in static cultures. In the present study, a flow of cell suspension was used to investigate cell adhesion onto nanopits in dynamic conditions, by means of a parallel-plate flow chamber. A flow chamber with inner nanotopography has been designed, which allows real-time observation of the flow over the nanopits. A nanopitted pattern was successfully embossed into polymethylmethacrylate to meet the required shape of the chamber. Dynamic cell adhesion after 1 h has been quantified and compared on flat and nanopitted polymethylmethacrylate substrates. The nanopits were seen to be significantly less adhesive than the flat substrates (p<0.001), which is coherent with previous observations of static cultures.

A Biodegradable and Biocompatible Regular Nanopattern for Large‐Scale Selective Cell Growth

A biodegradable substrate with a regular array of nanopillars fabricated by electron-beam lithography and hot embossing is used to address the mechanisms of nanotopographical control of cell behavior. Two different cell lines cultured on the nanopillars show striking differences in cell coverage. These changes are topography- and cell-dependent, and are not mediated by air bubbles trapped on the nanopattern. For the first time, a strong cell-selective effect of the same nanotopography has been clearly demonstrated on a large area; while fibroblast proliferation is inhibited, endothelial cell spreading is visibly enhanced. The reduced fibroblast proliferation indicates that a reduction of available surface area induced by nanotopography might be the main factor affecting cell growth on nanopatterns. The results presented herein pave the way towards the development of permanent vascular replacements, where non-adhesive, inert, surfaces will induce rapid in situ endothelialization to reduce thrombosis and occlusion.

Laminin adsorption on nanostructures: switching the molecular orientation by local curvature changes.

This work addresses the influence that the nanometric features of biologically relevant surfaces have on the conformation and properties of adsorbed laminin. It was observed that the adsorption kinetics and the nanomorphology of laminin were affected by the change in local curvature of chemically homogeneous nanostructured surfaces. The nanostructured surfaces were prepared by exploiting the self-assembly process of carboxylated polystyrene NPs, with diameters of 45, 109, and 209 nm, onto a polyelectrolyte multilayer formed by alternate deposition of poly(acrylic acid) and poly(allylamine hydrochloride) on gold. The anchored polymeric NPs were finally coated with a homogeneous layer of poly(allylamine hydrochloride), providing three surfaces with different nanometric local curvature. Atomic force microscopy was employed to characterize the relevant morphological parameters of the nanostructured surfaces. Quartz crystal microbalance with dissipation monitoring was employed to determine the adsorbed mass of laminin as well as its adsorption rate as a function of the local surface curvature. A model is proposed to explain the higher and faster laminin adsorption on surfaces with lower local curvature, where a switching of laminin anchoring orientation from a side-on to an end-on geometry can be predicted by a simple curvature-dependent parameter, γ, connecting the average nanostructure height h and the macromolecule radius of gyration R(g). The results provide a framework to understand the dependence of biomolecule orientation on local nanostructure.

Nano patterned surfaces for biomaterial applications

Bionanotechnology has seen much interest in the past few years. The development in new nanotechnologies and the transfer of such to biomedical applications has been received with large expectations. Here we will describe some of the most common techniques to prepare surfaces with nanometric sized features and how they have been applied to control cell behavior. The focus, however, will be on electron beam lithography and its use in biological applications. We will show that such highly ordered surfaces exhibit low adhesive properties for cells. Also, such topographies change the wetting properties to be either more hydrophilic or hydrophobic depending on the surface energy of the flat surface. Today, little research has found its way to the commercial market. This is mainly down to the ability to make large areas or large quantities of nano patterned materials. We will describe a few methods by which we think it would be possible to mass produce nano topographically patterned surfaces.