Vacuum arc plasma deposition of thin titanium dioxide films on silicone elastomer as a functional coating for medical applications.

Silicone elastomer is a promising material for medical applications and is widely used for implants with blood and tissue contact. However, its strong hydrophobicity limits adhesion of tissue cells to silicone surfaces, which can impair the healing process. To improve the biological properties of silicone, a triggerless pulsed vacuum cathodic arc plasma deposition technique was applied to deposit titanium dioxide (TiO2) films onto the surface. Scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and contact angle measurements were used for coating characterization. Deposited films were about 150nm thick and exhibited good adhesion to the underlying silicone substrate. Surface wettability and roughness both increased after deposition of the TiO2 layer. In addition, cell-biological investigations demonstrated that the in-vitro cytocompatibility of TiO2-coated samples was greatly improved without impacting silicone's nontoxicity. For validation of use in medical devices, further investigations were conducted and demonstrated stability of surface properties in an aqueous environment for a period of 68days and the coating's resistance to several sterilization methods.

Endothelialization and characterization of titanium dioxide-coated gas-exchange membranes for application in the bioartificial lung.

Fouling on the gas-exchange hollow-fiber membrane (HFM) of extracorporeal membrane oxygenation (ECMO) devices by blood components and pathogens represents the major hurdle to their long-term application in patients with lung deficiency or unstable hemodynamics. Although patients are treated with anticoagulants, deposition of blood proteins onto the membrane surface may still occur after few days, leading to insufficient gas transfer and, consequently, to device failure. The aim of this study was to establish an endothelial cell (EC) monolayer onto the gas-exchange membrane of an ECMO device with a view to developing a hemocompatible bioartificial lung. Poly(4-methyl-1-pentene) (PMP) gas-exchange membranes were coated with titanium dioxide (TiO2), using the pulsed vacuum cathodic arc plasma deposition (PVCAPD) technique, in order to generate a stable interlayer, enabling cell adhesion onto the strongly hydrophobic PMP membrane. The TiO2 coating reduced the oxygen transfer rate (OTR) of the membrane by 22%, and it successfully mediated EC attachment. The adhered ECs formed a confluent monolayer, which retained a non-thrombogenic state and showed cell-to-cell, as well as cell-to-substrate contacts. The established monolayer was able to withstand physiological shear stress and possessed a "self-healing" capacity at areas of induced monolayer disruption. The study demonstrated that the TiO2 coating mediated EC attachment and the establishment of a functional EC monolayer. STATEMENT OF SIGNIFICANCE: Surface endothelialization is considered an effective approach to achieve complete hamocompatibility of blood-contacting devices. Several strategies to enable endothelial cell adhesion onto stents and vascular prostheses have already been described in the literature. However, only few studies investigated the feasibility of establishing an endothelial monolayer onto the gas exchange membrane of ECMO devices, using peptides or proteins that were weakly adsorbed via dip coating techniques. This study demonstrated the effectiveness of an alternative and stable titanium dioxide coating for gas-exchange membranes, which enabled the establishment of a confluent, functional and non-activated endothelial monolayer, while maintaining oxygen permeability.