Enhanced cell adhesion to silicone implant material through plasma surface modification.

Silicone implant material is widely used in the field of plastic surgery. Despite its benefits the lack of biocompatibility this material still represents a major problem. Due to the surface characteristics of silicone, protein adsorption and cell adhesion on this polymeric material is rather low. The aim of this study was to create a stable collagen I surface coating on silicone implants via glow-discharge plasma treatment in order to enhance cell affinity and biocompatibility of the material. Non-plasma treated, collagen coated and conventional silicone samples (non-plasma treated, non-coated) served as controls. After plasma treatment the change of surface free energy was evaluated by drop-shape analysis. The quality of the collagen coating was analysed by electron microscopy and Time-Of-Flight Secondary Ion Mass Spectrometry. For biocompatibility tests mouse fibroblasts 3T3 were cultivated on the different silicone surfaces and stained with calcein-AM and propidium iodine to evaluate cell viability and adherence. Analysis of the different surfaces revealed a significant increase in surface free energy after plasma pre-treatment. As a consequence, collagen coating could only be achieved on the plasma activated silicone samples. The in vitro tests showed that the collagen coating led to a significant increase in cell adhesion and cell viability.

Transfer of mitochondrial function into a cytoplasmic respiratory-deficient mutant of Saccharomyces yeast by electro-fusion.

Electric field-induced fusion was induced between Saccharomyces cerevisiae protoplasts from the ρ (-) heterozygous diploid strain 2114 and the respiratory-competent diploid strain 3441, carrying chromosomal markers. Close membrane contact between the cells of the two different strains (ratio 1:1) was achieved by dielectrophoresis in a weak inhomogeneous alternating field (about 1 kV/cm, 2 MHz). Due to dielectrophoresis pearl chains of two or more cells of the two strains are formed between the electrodes. Cell fusion was induced by application of two single square field pulses sufficiently high to induce reversible electrical breakdown in the membrane contact zone between cells within a pearl chain (about 7 to 8 kV/cm field strength and 40 Ms duration). The two subsequent pulses were applied at an interval of about 10 s.Hybrids could be isolated on selection medium in a high yield (compared with conventional fusion techniques). The hybrids were diploid, respiratory-competent and produced prototrophic spores. Thus, the fused hybrids contained only the chromosomal markers of strain 2114 and the cytoplasmic marker for respiratory competence from strain 3441; electro-fusion thus resulted mainly in plasmogamy.