So Nagashima

Adhesion behavior of mouse liver cancer cells on nanostructured superhydrophobic and superhydrophilic surfaces

The control of cancer cell adhesion behavior on certain surfaces has been widely studied in recent years to enhance cell adhesion, which is required for bio-sensing, implant biomaterials, or to prevent infections from bacteria or germs. In addition, it helps to preserve the original functions of medical devices such as implants, catheters, injection syringes, and vascular stents. In this study, we explored the behavior of mouse liver cancer cells on nanostructured surfaces in extreme wetting conditions of a superhydrophobic or superhydrophilic nature. Oxygen plasma treatment of polymeric surfaces induced the formation of nanostructures such as bumps or hairs with various aspect ratios, which is defined as the height to diameter ratio. A superhydrophobic surface with a contact angle (CA) of 161.1° was obtained through the hydrophobic coating of a nanostructured surface with a high aspect ratio of 25.8. On the other hand, an opposite extreme wetting surface with a superhydrophilic nature with a CA of 1.7° was obtained through the hydrophilic coating of the same structured surface. The mouse liver cancer cells significantly proliferated on a mild hydrophilic surface with a low aspect ratio nanostructure due to the mild roughness and improvements of mechanical anchoring. However, the superhydrophilic surface with a high aspect ratio nanostructure (i.e., hair shaped) suppressed the growth of the cancer cells due to the limited number of sites for focal adhesion, which restricted the adhesion of cancer cells and resulted in a decrease in the cell-covered area. The superhydrophobic nanostructured surface with a high aspect ratio further restricted the adhesion and growth of the cancer cells; the cell activity was extremely suppressed and the spherical shape of the cancer cells was maintained. Thus, this simple method for fabricating nanostructured surfaces with various wetting conditions might be useful for producing biomedical devices such as stents, implants, drug delivery devices, and detection and/or sensing devices for cancer cells.

Ultrastructural characterization of surface-induced platelet activation on artificial materials by transmission electron microscopy

Platelet adhesion is one of the most pivotal events of blood clotting for artificial surfaces. However, the mechanisms of surface‐induced platelet activation have not been fully been elucidated or visualized so far. In this study, we attempted to observe the internal structures and adhesion interfaces of human platelets attached to artificial surfaces by transmission electron microscopy (TEM) during the platelet activation process. We prepared observation samples by a conventional embedding method using EPON 812 resin. The sectioning was sliced perpendicular to the a‐platelet/material interface. Observation by TEM indicates that internal granules coalesce in the center of the platelet accompanied by pseudopodial growth in the early stage of platelet activation. Pseudopodia from a platelet attach to the material interface not along a plane but at a point. In addition, along with the process of platelet activation, the gap between the platelet membrane and the material surface at the interface disappeared and a‐platelet/material adhesion became much tighter. In the fully activated platelet stage, the platelet becomes thinner and tightly adheres to the substrate. As a result of comparative observation of an adherent platelet on polycarbonate (PC) and on amorphous carbon (a‐C:H), it was found that internal granules release was inhibited more remarkably on a‐C:H coating rather than on PC. Despite numerous technical difficulties in preparing sectional samples, such a study might prove the essential mechanism of biomaterial‐related thrombosis, and it might become possible to modify the surfaces of materials to minimize material‐related thrombosis. Microsc. Res. Tech. 76:342–349, 2013.

Spontaneous formation of aligned DNA nanowires by capillarity-induced skin folding

Significance Developing a method that is capable of manipulating the size, geometry, and alignment of DNA nanowires would expand their uses in fabricating functional materials and performing genetic analysis. Here, we present an approach that yields arrays of size-controllable straight or undulated DNA nanowires. This approach uses a template composed of a thin skin that dynamically changes its surface morphology in response to water. In particular, we exploit capillary forces of water containing DNA molecules to induce a wrinkle-to-fold transition of the template surface in an unconventional way, which in turn stretches and confines the molecules in the folded regions without any external forces and consequently forms the nanowires. This approach could make possible new fabrication opportunities for functional materials. Although DNA nanowires have proven useful as a template for fabricating functional nanomaterials and a platform for genetic analysis, their widespread use is still hindered because of limited control over the size, geometry, and alignment of the nanowires. Here, we document the capillarity-induced folding of an initially wrinkled surface and present an approach to the spontaneous formation of aligned DNA nanowires using a template whose surface morphology dynamically changes in response to liquid. In particular, we exploit the familiar wrinkling phenomenon that results from compression of a thin skin on a soft substrate. Once a droplet of liquid solution containing DNA molecules is placed on the wrinkled surface, the liquid from the droplet enters certain wrinkled channels. The capillary forces deform wrinkles containing liquid into sharp folds, whereas the neighboring empty wrinkles are stretched out. In this way, we obtain a periodic array of folded channels that contain liquid solution with DNA molecules. Such an approach serves as a template for the fabrication of arrays of straight or wrinkled DNA nanowires, where their characteristic scales are robustly tunable with the physical properties of liquid and the mechanical and geometrical properties of the elastic system.

Diamond-Like Carbon Coatings for Joint Arthroplasty

With the increase in the average human lifespan, there is an 6 increased demand for high quality health-related products. Biomedi7 cal implants such as hip joints, vascular grafts, and dental roots have 8 proven to be effective for the treatment of major injuries to improve 9 the overall quality of life. Joint replacement is a common orthope10 dic procedure wherein dysfunctional joints, including hips and knees, 11 are replaced with implants. These implants are primarily composed 12 of metals (e.g. titanium, stainless steel), metal alloys (e.g. titanium– 13 aluminum–vanadium alloys, cobalt–chromium–molybdenum alloys), 14 ceramics (alumina-based), or polymeric materials (e.g. ultra-high 15 molecular weight polyethylene (UHMWPE)). Such implants demon16 strate adequate short-term biocompatibility and mechanical prop17 erties; however, they are far from being completely biostable or 18 inert. Accordingly, these implants suffer from several drawbacks with 19 respect to long-term use, such as cytotoxicity to surrounding tissues, 20 the release of metal ions or wear debris that causes allergic reactions, 21 corrosion, and frictional wear. To reduce such risks, the biological 22 compatibility and long-term stability of joint replacement implants 23 need to be improved. 24

Human Umbilical Vein Endothelial Cell Interaction with Fluorine-Incorporated Amorphous Carbon Films

A major clinical concern in coronary intervention for cardiovascular disease is late stent thrombosis after the implantation of drug eluting stents (DES). DES widely used in clinical settings currently utilize polymer coatings, which can induce persistent arterial wall inflammation and delayed vascular healing, resulting in impaired endothelialization. We examined the viability of human umbilical vein endothelial cells (HUVECs) for fluorine-incorporated amorphous carbon (a-C:H:F) coatings, which are known to be anti-thrombogenic. a-C:H:F and a-C:H were synthesized on the tissue culture dishes using radio frequency plasma enhanced chemical vapor deposition by varying the ratio of hexafluoroethane and acetylene. HUVECs were seeded on coated dishes for 6 days. The results indicate that the a-C:H:F surface does not disturb HUVEC proliferation in 6 days of culture and is promising for stent materials that allows the preservation of endothelialization, even if the fluorine concentration of a-C:H surface affects the early adhesion of endothelial cells.

Diamond-Like Carbon Coatings with Special Wettability for Automotive Applications

Surface modification is an effective way of improving the tribological properties of base materials and is now actively being used in the automotive industry. Surface wettability can affect the overall performance of automotive components, such as windshields and mirrors, and controlling the surface hydrophobicity or hydrophilicity has been a major focus of research work in this industry. Diamond-like carbon (DLC), which is an amorphous carbon compound with outstanding mechanical and tribological properties, has gained considerable attention as a superior functional coating material and has been successfully applied to a range of mechanical automotive components, leading to better performance and durability. Recently, DLC-based materials with special wettability have been successfully used for the development of superhydrophobic and superhydrophilic surfaces, and a variety of industrial as well as biomedical applications have been proposed. Undoubtedly, being able to control the surface wettability using such DLC-based materials with tunable wettability would expand the original capabilities of the materials used in the automotive industry today. In this chapter, after giving a brief introduction to the fundamentals of surface wettability in relation to DLC coatings, we review recent studies on the control of surface wettability using DLC-based materials and then discuss future outlook.