Cell Sensing and Response to Micro- and Nanostructured Surfaces Produced by Chemical and Topographic Patterning

Microfabricated implants for applications in therapeutic delivery, tissue engineering, and biosensing

By adapting microfabrication techniques originally developed in the microelectronics industry novel devices for drug delivery, tissue engineering and biosensing have been engineered for in vivo use. Implant microfabrication uses a broad range of techniques including photolithography, and micromachining to create devices with features ranging from 0.1 to hundreds of microns with high aspect ratios and precise features. Microfabrication offers device feature scale that is relevant to the tissues and cells to which they are applied, as well as offering ease of en masse fabrication, small device size, and facile incorporation of integrated circuit technology. Utilizing these methods, drug delivery applications have been developed for in vivo use through many delivery routes including intravenous, oral, and transdermal. Additionally, novel microfabricated tissue engineering approaches propose therapies for the cardiovascular, orthopedic, and ocular systems, among others. Biosensing devices have been designed to detect a variety of analytes and conditions in vivo through both enzymatic-electrochemical reactions and sensor displacement through mechanical loading. Overall, the impact of microfabricated devices has had an impact over a broad range of therapies and tissues. This review addresses many of these devices and highlights their fabrication as well as discusses materials relevant to microfabrication techniques.

Supercritical CO2-assisted embossing for studying cell behaviour on microtextured surfaces

Recently, cell responses to micro- and nanoscale structures have attracted much attention. Although interesting phenomena have been observed, we have encountered some difficulties in elucidating purely topographical effects on cell behaviour. These problems are partially attributable to the introduction of functional groups and the persistence of chemicals during surface processing. In this study, we introduced supercritical CO(2)-assisted embossing, which plasticizes a polycarbonate plate by dissolving supercritical CO(2) and thus can emboss wide-scale patterns onto the plate at a lower temperature than the polycarbonate glass transition temperature. Uniform micro- and nanopatterned surfaces were observed across the whole area of the polycarbonate plate surfaces. Nickel, fluorine, and nitrogen were not detected on the fabricated surfaces, and the surface carbon-to-oxygen ratios were equivalent to the theoretical ratio (C:O=84.2:15.8) calculated from the polycarbonate molecular structure. Human mesenchymal stem cells were cultured on the fabricated microlens and nanogroove substrata. Cell-adhered areas became smaller on the microlens than on non-treated polycarbonate. Meanwhile, cells aligned along the ridges of nanogrooves with valleys deeper than 90 nm. This supercritical CO(2)-assisted embossing can produce fine substrates for studying the effects of surface topography of synthetic materials on cell behaviours.

Ultrathin Coatings with Change in Reactivity over Time Enable Functional In Vitro Networks Of Insect Neurons

It's just not cricket! A novel coating system that enables covalent attachment of biomolecules in a nonfouling environment without use of additional chemical crosslinkers is presented. Concanavalin A is patterned on the coatings to direct cell adhesion and growth of neurons from the cricket Gryllus bimaculatus and generate functional, patterned in vitro insect neuronal networks for the first time.

Extracellular matrix remodelling during cell adhesion monitored by the quartz crystal microbalance

A cell's ability to remodel adsorbed protein layers on surfaces is influenced by the nature of the protein layer itself. Remodelling is often required to accomplish cellular adhesion and extracellular matrix formation which forms the basis for cell spreading, increased adhesion and expression of different phenotypes. The adhesion of NIH3T3 (EGFP) fibroblasts to serum protein (albumin or fibronectin) precoated tantalum (Ta) and oxidised polystyrene (PS(ox)) surfaces was examined using the quartz crystal microbalance with dissipation (QCM-D) monitoring and fluorescence microscopy. The cells were either untreated or treated with cycloheximide to examine the contribution of endogenous protein production during cell adhesion to the QCM-D response over a period of 2h. Following adsorption of albumin onto Ta and PS(ox) there was no difference detected between the response to seeding untreated and cycloheximide treated cells. The QCM-D was able to detect differences in the untreated cellular responses to fibronectin versus serum precoated Ta and PS(ox) substrates, while cycloheximide treatment of the cells produced the same QCM-D response for fibronectin and serum precoatings on each of the materials. This confirmed that the process of matrix remodelling by the cells is dependent on the underlying substrate and the preadsorbed proteins and that the QCM-D response is dominated by changes in the underlying protein layer. Changes in dissipation correspond to the development of the actin cytoskeleton as visualised by actin staining.

Surface energy effects on osteoblast spatial growth and mineralization

While short-term surface energy effects on cell adhesion are relatively well known, little is revealed as regards its later stage effects on cell behavior. We examined surface energy effects on osteoblastic cell growth and mineralization by using human fetal osteoblastic (hFOB) cells cultured on plasma-treated quartz (contact angle, theta=0 degrees) and octadecyltrichlorosilane (OTS)-treated quartz (theta=113 degrees). hFOB cells formed a homogeneous cell layer on plasma-treated quartz, while those cultured on OTS-treated quartz produced randomly distributed clump-like structures that were filled with cells (confirmed by confocal microscopy). Mineral deposition by hFOB cells was spatially homogeneous when cultured on hydrophilic surfaces. Furthermore, cells on hydrophilic surfaces exhibited increased mineralized area as well as enhanced mineral-to-matrix ratio (assessed by Fourier transform infrared spectroscopy), relative to cells on hydrophobic surfaces. Experiments using other types of osteoblast-like cells (MC3T3-E1, MG63, and SAOS-2) revealed more or less similar effects in spatial growth morphology. It was concluded that hydrophilic surfaces induce homogeneous spatial osteoblastic cell growth and mineral deposition and enhance the quantity (e.g., area) and quality (e.g., mineral-to-matrix ratio) of mineralization relative to hydrophobic surfaces. Our data suggest that surface energy effects on osteoblastic cell differentiation, especially mineralization, may be correlated with surface energy dependent changes in spatial cell growth.