Development of Antimicrobial Surfaces Using Diamond-like Carbon or Diamond-like Carbon-Based Coatings.

The medical device market is a high-growth sector expected to sustain an annual growth rate of over 5%, even in developed countries. Daily, numerous patients have medical devices implanted or inserted within their bodies. While medical devices have significantly improved patient outcomes, as foreign objects, their wider use can lead to an increase in device-related infections, thereby imposing a burden on healthcare systems. Multiple materials with significant societal impact have evolved over time: the 19th century was the age of iron, the 20th century was dominated by silicon, and the 21st century is often referred to as the era of carbon. In particular, the development of nanocarbon materials and their potential applications in medicine are being explored, although the scope of these applications remains limited. Technological innovations in carbon materials are remarkable, and their application in medicine is expected to advance greatly. For example, diamond-like carbon (DLC) has garnered considerable attention for the development of antimicrobial surfaces. Both DLC itself and its derivatives have been reported to exhibit anti-microbial properties. This review discusses the current state of DLC-based antimicrobial surface development.

Comprehensive hemocompatibility analysis on the application of diamond-like carbon to ePTFE artificial vascular prosthesis.

The aim of this study was to obtain comprehensive data regarding the hemocompatibility of diamond-like carbon (DLC)-coated expanded polytetrafluoroethylene (ePTFE). DLC increased the hydrophilicity and smoothened the surface and fibrillar structure, respectively, of the ePTFE. DLC-coated ePTFE had more albumin and fibrinogen adsorption and less platelet adhesion than uncoated ePTFE. There were scarce red cell attachments in in vitro human and in vivo animal (rat and swine) whole blood contact tests in both DLC-coated and uncoated ePTFE. DLC-coated ePTFE had a similar but marginally thicker band movement than uncoated-ePTFE with SDS-PAGE after human whole blood contact test. In addition, survival studies of aortic graft replacement in rats (1.5 mm graft) and arteriovenous shunt in goats (4 mm graft) were performed to compare the patency and clot formation between DLC-coated and uncoated ePTFE grafts. Comparable patency was observed in both animal models. However, clots were observed in the luminal surface of the patent 1.5 mm DLC-coated ePTFE grafts, but not in that of uncoated ePTFE grafts. In conclusions, hemocompatibility of DLC-coated ePTFE was high and comparable to that of uncoated ePTFE. However, it failed to improve the hemocompatibility of 1.5 mm ePTFE graft probably because increased fibrinogen adsorption canceled the other beneficial effects of DLC.

Diamond-like carbon coating to inner surface of polyurethane tube reduces Staphylococcus aureus bacterial adhesion and biofilm formation.

Staphylococcus aureus is one of the main causative bacteria for polyurethane catheter and artificial graft infection. Recently, we developed a unique technique for coating diamond-like carbon (DLC) inside the luminal resin structure of polyurethane tubes. This study aimed to elucidate the infection-preventing effects of diamond-like carbon (DLC) coating on a polyurethane surface against S. aureus. We applied DLC to polyurethane tubes and rolled polyurethane sheets with our newly developed DLC coating technique for resin tubes. The DLC-coated and uncoated polyurethane surfaces were tested in smoothness, hydrophilicity, zeta-potential, and anti-bacterial properties against S. aureus (biofilm formation and bacterial attachment) by contact with bacterial fluids under static and flow conditions. The DLC-coated polyurethane surface was significantly smoother, more hydrophilic, and had a more negative zeta-potential than did the uncoated polyurethane surface. Upon exposure to bacterial fluid under both static and flow conditions, DLC-coated polyurethane exhibited significantly less biofilm formation than uncoated polyurethane, based on absorbance measurements. In addition, the adherence of S. aureus was significantly lower for DLC-coated polyurethane than for uncoated polyurethane under both conditions, based on scanning electron microscopy. These results show that applying DLC coating to the luminal resin of polyurethane tubes may impart antimicrobial effects against S. aureus to implantable medical polyurethane devices, such as vascular grafts and central venous catheters.

Intraluminal diamond-like carbon coating with anti-adhesion and anti-biofilm effects for uropathogens: A novel technology applicable to urinary catheters.

OBJECTIVES: To examine anti-adhesion and anti-biofilm effects of a diamond-like carbon coating deposited via a novel technique on the inner surface of a thin silicon tube. METHODS: Diamond-like carbon coatings were deposited into the lumen of a silicon tube with inner diameters of 2 mm. The surface of the diamond-like carbon was evaluated using physicochemical methods. We used three clinical isolates including green fluorescent protein-expressing Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus. We employed a continuous flow system for evaluation of both bacterial adhesion and biofilm formation. Bacterial adhesion assays consisted of counting the number of colony-forming units and visualization of adhered bacterial cells by scanning electron microscope to evaluate the diamond-like carbon-coated/uncoated samples. The biofilm structure was analyzed by confocal laser scanning microscopy on days 3, 5, 7 and 14 for green fluorescent protein-expressing Pseudomonas aeruginosa. RESULTS: The smooth and carbon-rich structure of the intraluminal diamond-like carbon film remained unchanged after the experiments. The numbers of colony-forming units suggested lower adherence of green fluorescent protein-expressing Pseudomonas aeruginosa and Escherichia coli in the diamond-like carbon-coated samples compared with the uncoated samples. The scanning electron microscope images showed adhered green fluorescent protein-expressing Pseudomonas aeruginosa cells without formation of microcolonies on the diamond-like carbon-coated samples. Finally, biofilm formation on the diamond-like carbon-coated samples was lower until at least day 14 compared with the uncoated samples. CONCLUSIONS: Intraluminal diamond-like carbon coating on a silicone tube has anti-adhesion and anti-biofilm effects. This technology can be applied to urinary catheters made from various materials.

Development of an optical fiber SPR sensor for living cell activation.

Surface plasmon resonance (SPR) sensors provide a useful means to study the interactions of biological molecules and the reaction of living cells on a sensor chip. However, conventional SPR sensors are bulky, expensive and complicated to use as common diagnostic equipment. In this study, we developed a relatively small and simple SPR system, using optical fibers of 250 microm diameter to detect the activation of living cells attached to the fiber tip. For this system, the core of 200 microm diameter with 1cm length of an optical fiber was coated by gold film with 50 nm thickness to cause plasmon resonance. The light provided by a white LED and attenuated due to a SPR phenomenon in the sensor part was detected and analyzed using a spectrum detector. The difference in solvents with various refractive indexes and protein-bindings to the sensor tip was detected with sufficient sensitivity. Moreover, it detected a sustained increase of AR in a real-time manner, when RBL-2H3 mast cells were fixed onto the fiber tip and stimulated by an antigen. This small fiber SPR system might serve as a useful tool for various clinical examinations either within or outside the body.