In vivo interactions between novel filler free silicone rubber and blood

CD41 Western blotting: a new method to detect platelet adhesion to artificial surfaces used in extracorporeal circulation procedures

Cardiopulmonary bypass (CPB) surgery is associated with platelet activation and reduced platelet counts due to artificial surface activation of blood elements and non-physiological flow-patterns. As shown in former studies, coating of medical devices can improve hemocompatibility in extracorporeal circulation systems. In this study, we demonstrate a new method to determine platelet adhesion on 18 coated and non-coated membrane oxygenators in a simulated CPB model with CD41 Western blot. Platelet loss and the release of beta-TG (platelet activation marker) were determined during a 120 min recirculation phase. At the end of the run the membrane oxygenators (with tubing system) were rinsed and the amount of adsorbed proteins on the surface was analyzed by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting technique. Uncoated devices showed significantly higher concentrations of CD41 and of fibrinogen adsorption compared to the coated membrane oxygenators. These results correspond with the release of beta-TG and platelet loss indicating less platelet adhesion on the coated oxygenators compared with the uncoated group. This new method may be useful in choosing less platelet activating materials for all kind of blood contacting devices to improve thrombogenicity including platelet functionality.

Characterization of plasma polymerized silicone coatings useful as biomaterials

Plasma polymerization techniques were used to deposit a layer of filler-free silicone rubber on a variety of substrate materials. The thickness of the deposited film was 0.5-0.8 micron. As it is the surface of the biomaterial that comes in direct contact with the body fluids, the surface of the biomaterial is of paramount importance. In this study, the plasma polymerized biomaterials were characterized. Thus, the scanning electron microscope (SEM) showed the surfaces to be smooth. To study the surface layer of the deposited polymer, Fourier-transform infrared spectrometry in the attenuated total reflection (ATR) mode was used. The deposited material was indeed silicone polymer with adsorption bands at 1262, 1020, and 802 cm-1 for the Si-CH3 bending, Si-0-Si stretching, and Si-CH3 bending, respectively. To find the bonding nature of the polymer, electron spectrometry for chemical analysis (ESCA) was used. The silicone polymer was shown to be highly cross-linked. To find the molecular weight between cross-links, swelling studies were done. Thus the results of the study show that the plasma polymerization could produce a filler-free silicone layer on a variety of substrate materials.

Toxicity evaluation of a novel filler free silicone rubber biomaterial by cell culture techniques

Cytotoxicity of a novel filler free silicone rubber (FFSR) was evaluated by studying its effect on mouse L929 cells. Silastic and a laboratory rubber tubing (RT) were used as control materials. Three different experimental methods were used. In method A, after six days of cell culturing in the sample extracts, there were 95, 80, and 50% of control viable cells for FFSR, Silastic, and RT, respectively. Similarly, in method B, after six days of direct contact between samples and the cells, there were 80, 40, and 20% of control viable cells for FFSR, Silastic, and RT, respectively. For the Agar Overlay Test, method C, the cells under the FFSR samples were normal and healthy compared to those under Silastic and RT. From these studies it was concluded that FFSR had the least cytotoxicity of the three materials studied.

Use of plasma polymerization for preparing silicone-coated membranes for possible use in blood oxygenators

The plasma polymerization of hexamethylcyclotrisiloxane (D3) and octamethylcyclotetrasiloxane (D4) over the microporous polypropylene membrane Celgard 2400, over polypropylene filter membranes, and over glass slides was investigated. The rate of polymer deposition was dependent upon the location of the substrate materials in the reaction vessel. The increase in weight of all the substrates was linear with the time of reaction, indicating a uniform polymerization rate. The rate of polymer deposition over polypropylene filters was found to be 2.27 micrograms/cm(2)/min for both D3, and D4, whereas over the glass slides it was 1.53 and 1.87 microgram/cm(2)/min for D3 and D4, respectively. The coated Celgard membranes showed better blood compatibility that Silastic sheeting or glass.