Synthesis and antibacterial properties of silver nanoparticles.

Nanometer sized silver particles were synthesized by inert gas condensation and co-condensation techniques. Both techniques are based on the evaporation of a metal into an inert atmosphere with the subsequent cooling for the nucleation and growth of the nanoparticles. The antibacterial efficiency of the nanoparticles was investigated by introducing the particles into a media containing Escherichia coli. The antibacterial investigations were performed in solution and on petri dishes. The silver nanoparticles were found to exhibit antibacterial effects at low concentrations. The antibacterial properties were related to the total surface area of the nanoparticles. Smaller particles with a larger surface to volume ratio provided a more efficient means for antibacterial activity. The nanoparticles were found to be completely cytotoxic to E. coli for surface concentrations as low as 8 microg of Ag/cm2.

Effect of surface modification on protein retention and cell proliferation under strain.

When culturing cells on flexible surfaces, it is important to consider extracellular matrix treatments that will remain on the surface under mechanical strain. Here we investigate differences in laminin deposited on oxidized polydimethylsiloxane (PDMS) with plasma treatment (plasma-only) vs. plasma and aminopropyltrimethoxysilane treatment (silane-linked). We use specular X-ray reflectivity (SXR), transmission electron microscopy (TEM), and immunofluorescence to probe the quantity and uniformity of laminin. The surface coverage of laminin is approximately 45% for the plasma-only and 50% for the silane-linked treatment as determined by SXR. TEM and immunofluorescence reveal additional islands of laminin aggregates on the plasma-only PDMS compared with the relatively smooth and uniform silane-linked laminin surface. We also examine laminin retention under strain and vascular smooth muscle cell viability and proliferation under static and strain conditions. Equibiaxial stretching of the PDMS surfaces shows greatly improved retention of the silane-linked laminin over plasma-only. There are significantly more cells on the silane-linked surface after 4 days of equibiaxial strain.

Evaluation of polydimethylsiloxane modification methods for cell response.

Many methods exist in the literature to modify surfaces with extracellular matrix (ECM) proteins prior to cell seeding. However, there are few studies that systematically characterize and compare surface properties and cell response results among modification methods that use different bonding mechanisms. In this work, we compare cell response and physical characterization results from fibronectin or laminin attached to polydimethylsiloxane (PDMS) elastomer surfaces by physical adsorption, chemisorption, and covalent attachment to determine the best method to modify a deformable surface. We evaluate modification methods based on completeness and uniformity of coverage, surface roughness, and hydrophilicity of attached ECM protein. Smooth muscle cell adhesion, proliferation, morphology, and phenotype were also evaluated. We found that chemisorption methods resulted in higher amounts of protein attachment than physical adsorption and covalent bonding of the ECM proteins. Cell response to protein-modified surfaces was similar with respect to cell adhesion, area, aspect ratio, and phenotype. When all the data are considered, the chemisorption methods, most notably silane_70, provide the best surface properties and highest cell proliferation.