No abstract

To mimic the uniformly elongated endothelium in natural linear vessels, bovine aortic endothelial cells (BAECs) are cultured on micro- to nanogrooved, model poly(dimethylsiloxane) (PDMS) substrates preadsorbed with about 300 ng/cm(2) of fibronectin. BAEC alignment, elongation, and projected area were investigated for channel depths of 200 nm, 500 nm, 1 microm, and 5 microm, as well as smooth surfaces. Except for the 5 microm case, the ridge and channel widths were held nearly constant about 3.5 microm. With increasing channel depth, the percentage of aligned BAECs increased by factors of 2, 2, 1.8, and 1.7 for 1, 4, 24, and 48 h. Maximum alignment, about 90%, was observed for 1 microm deep channels at 1 h. The alignment of BAECs on grooved PDMS was maintained at least until cells reached near confluence. F-actin and vinculin at focal adhesions also aligned with channel direction. Analysis of confocal microscopy images showed that focal adhesions localized at corners and along the sidewalls of 1-microm deep channels. In contrast, focal adhesions could not form on the bottom of the 5-microm deep channels. Cell proliferation was similar on grooved and smooth substrates. In summary, PDMS substrates engraved with micro- and nanochannels provide a powerful method for investigating the interplay between topography and cell/cytoskeletal alignment.

This article reports that surface modification of poly(dimethylsiloxane) (PDMS) influences fibronectin (Fn) adsorption and enhances cell attachment. Controlled adsorption of Fn on chemically activated polymer substrates is known to influence cellular function. Thin films of PDMS were spun cast on silicon wafers to obtain homogeneous and molecularly smooth surfaces. The films were made hydrophilic by exposure to ultraviolet ozone activation (PDMS*). The films then were characterized by contact angle goniometry, ellipsometry, atomic force microscopy (AFM), Rutherford backscattering spectrometry and X-ray photoelectron spectroscopy. Contact angle measurements indicated higher hydrophobicity of the nonactivated PDMS substrates than PDMS*. AFM scans of the substrates indicated higher surface roughness of PDMS* (Ra = 0.55 nm) than PDMS (Ra = 0.25 nm). Although Fn surface density (Gamma) was slightly higher on PDMS than on PDMS*, due to hydrophobic interactions between substrate and Fn, cell function was greatly enhanced on the Fn-coated PDMS* (PDMS*-Fn) than on PDMS (PDMS-Fn). Higher attachment of MC3T3-E1 osteoblast-like cells was observed on PDMS*-Fn than on PDMS-Fn. Moreover, cell spreading and cytoskeleton organization after 72 h was clearly favored on the Fn-coated PDMS* surfaces.

Bioactive glass (BG) can directly bond to living bone without fibrous tissue encapsulation. Key mechanistic steps of BG's activity are attributed to calcium phosphate formation, surface hydroxylation and fibronectin (FN) adsorption. In the present study, self-assembled monolayers (SAMs) of alkanesilanes with different surface chemistry (OH, NH 2 and COOH) were used as a model system to mimic BG's surface activity. Calcium phosphate (Ca-P) was formed on SAMs by immersion in a solution that simulates the electrolyte content of physiological fluids. FN adsorption kinetics and monolayer coverage was determined on SAMs with or without Ca-P coating. The surface roughness was also examined on these substrates before and after FN adsorption. The effects of FN-adsorbed, Ca-P-coated SAMs on the function of MC3T3-E1 were evaluated by cell growth, expression of alkaline phosphatase activity and actin cytoskeleton formation. We demonstrate that, although the FN monolayer coverage and the root mean square (rms) roughness are similar on -OH and -COOH terminated SAMs with or without Ca-P coating, higher levels of ALP activity, more actin cytoskeleton formation and more cell growth are obtained on -OH-and -COOH-terminated SAMs with Ca-P coating. In addition, although the FN monolayer coverage is higher on Ca-P-coated -NH 2 -terminated SAMs and SiO x surfaces, higher levels of ALP activity and more cell growth are obtained on Ca-P-coated -OH-and -COOH-terminated SAMs. Thus, with the same Ca-P coatings, different surface functional groups have different effects on the function of osteoblastic cells. These findings represent new insights into the mechanism of bioactivity of BG and thereby may lead to designing superior constructs for bone grafting.

No abstract