Seisuke Takashima

Antibacterial effect of bactericide immobilized in resin matrix

OBJECTIVE Biomaterials with anti-microbial properties are highly desirable in the oral cavity. Ideally, bactericidal molecules should be immobilized within the biomaterial to avoid unwanted side-effects against surrounding tissues. They may then however loose much of their antibacterial efficiency. The aim of this study was to investigate how much antibacterial effect an immobilized bactericidal molecule still has against oral bacteria. METHODS Experimental resins containing 0, 1 and 3% cetylpyridinium chloride (CPC) were polymerized, and the bacteriostatic and bactericidal effects against Streptococcus mutans were determined. Adherent S. mutans on HAp was quantitatively determined using FE-SEM and living cells of S. mutans were quantified using real-time RT-PCR. The amount of CPC released from the 0%-, 1%- and 3%-CPC resin sample into water was spectrometrically quantified using a UV-vis recording spectrophotometer. RESULTS UV spectrometry revealed that less than 0.11 ppm of CPC was released from the resin into water for all specimens, which is lower than the minimal concentration generally needed to inhibit biofilm formation. Growth of S. mutans was significantly inhibited on the surface of the 3%-CPC-containing resin coating, although no inhibitory effect was observed on bacteria that were not in contact with its surface. When immersed in water, the antibacterial capability of 3%-CPC resin lasted for 7 days, as compared to resin that did not contain CPC. SIGNIFICANCE These results demonstrated that the bactericidal molecule still possessed significant contact bacteriostatic activity when it was immobilized in the resin matrix.

Highly blood compatible titania gel

We examined blood compatibility of titania gels prepared through a sol-gel processing or yielded on titanium substrates by treating with hydrogen peroxide or simple heating. The blood compatibility was evaluated in terms of blood clotting time and correlated to the crystalline phases, roughness, specific surface area, and wettability. The sol-gel derived titania gel heated above 200°C had good blood compatibility. Ti substrate treated with hydrogen peroxide and subsequently heated at 550°C showed the best blood compatibility among the Ti substrates with or without the chemical treatment and heat-treatment. The specimen consisted of rutile and anatase phases, and had hydrophilic surface.

In vitro apatite formation on organic polymers modified with a silane coupling reagent

γ-Methacryloxypropyltrimethoxysilane (γ-MPS) was grafted to high-density polyethylene, polyamide and silicone rubber substrates by the emulsion polymerization procedure in order to provide these organic polymers with in vitro apatite-forming ability. The contact angles towards distilled water of the γ-MPS-grafted specimens were lower than those of the original organic polymer specimens, indicating that the grafted substrates were more hydrophilic. The in vitro apatite formation in a simulated body fluid (Kokubo solution) was confirmed for several of the γ-MPS-grafted specimens.

Surface modification of polymers with grafting and coating of silane hybrids and their bioactivity

Hydrated silica rich Si-OH and Si-0- groups serve in a body environment as sites for nucleation of apatite, and are known as an essential chemical species for bioactive materials. Organic polymers having surface modified with the hydrated silica will show bioactivity: bone tissues grow toward the apatite layer and bond to materials. Thus MOPS-M (3-methacryloxypropyltrimethoxysilane) was grafted under emulsion polymerization procedure to high density polyethylene (HDPE), poly (vinyl chloride) (PVC) and polyamide (PA) substrates to examine in vitro deposition of apatite (bioactivity) after soaking in a simulated body fluid (Kokubo solution). Bioactivity was confirmed for the grafted PVC and PA substrates and discussed in terms of contact angle and relative amount of grafted silane molecules.

Cytocompatibility on Silicone Modified with Organoalkoxysilane due to Emulsion Polymerization

γ-Methacryloxypropyltrimethoxysilane ( γ-MPS) molecules were grafted on silicone elastomer by emulsion polymerization. Fibroblast and osteoblastic cells wer e cultured to examine cytocompatibility of the grafted surface. A greater number of cells grew on the grafted silicone, even forming a cell layer, than on the original silicone. Moreove r, the cultured cells were agglomerated on the latter though they adhered well. Thus the γ-MPS grafting was concluded to improve cytocompatibility of silicone. Introduction Silicone is one of the most important biomaterials for restoring damaged tissues in clinical fields, such as finger joints, hydrocephalus shunts and breast implant. However, when implanted in the human body, the body recognizes it as foreign substance a nd results in encapsulation with a fibrous tissue. When silicone surface is provided with ability of i nducing spontaneous deposition of apatite in vivo, silicone will firmly be fixed to living bone us ing the apatite layer as the glue after Kokubo [1]. That is, such surface is cytocompatible and exhibits affini ty for cells. We have already reported that emulsion polymerization grafted polymer subs trate such as polyethylene (PE) with organoalkoxysilane molecules and provided them with bioactivity [2 ]. In this study, we grafted organoalkoxysilane onto the silicone surfaces and evaluated cytocom patibility. Materials and Methods A room temperature vulcanizing (RTV) type liquid and a solidifying agent were mixed for 30 min. The mixture was cast into a mold, and heated for 30 min at 150 °C . Rectangular specimens of 20x20x1mm were cut from a sheet of the silicone rubber. Those specimens we re washed with distilled water for 5 min in an ultrasonic cleaning bath and then soake d in thanol for 24 hours. The specimens were taken out and dried at room temperature under vacuum . The original specimens were denoted as “ NT “ below. The specimens were hung in the midst of a three-necked separa bl flask to which added were distilled water and sodium lauryl sulfate as the emulsifier. T he solution was stirred for 30min under an N2 flow at 60, 70 and 80 °C. γ-MPS (3ml) was added drop-wisely into the solution. Then, aqueous solutions of potassium peroxosulfate and sodium hydrogen sulfit were added. The resultant solution was further stirred for 30~120 min at those temper atur s under an atmosphere of flowing N2. The obtained specimens were ultrasonically washed with distilled wate r for 5 min and Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 687-690 doi:10.4028/www.scientific.net/KEM.240-242.687

Deactivation of Active Oxygen Species due to Metals and their Blood Compatibility

The deactivating behavior of the active oxygen species e xcept nitric oxide or NO was observed in the presence of some metals used in clinical fie lds by simple colorimetry. It was indicated that SUS316 and Ti were inert against most of the active oxygen species. Introduction Stainless steel (SUS), titanium and tantalum are typical metals used in orthopedic and cardiovascular fields. Blood compatibility is one of the m ost important properties that they should exhibit. It is common clinically to evaluate blood comp atibility in terms of partial thromboplastin time (PTT), prothrombin time (PT), and amount of fibrinogen (Fib) [1,2]. When materials contact with blood plasma and the values of those parameters do not change, the materials are then denoted to be well blood compatible. Tha t is, the materials causing no changes on substance related to homeostasis are of good blood compatibility. Metabolism in our body keeps many chemical species at steady concentr atio s, including active oxygen species, such as hydroxyl radical (•OH), singlet state oxy gen (O2), super oxide (O2 ) and hydrogen peroxide (H 2O2). In a preliminary study, Takashima et al. [3] found that st inless steel and titanium were blood compatible in terms of PTT, PT and Fib. Though metal surface is covered more or less with relevant metal oxides, me tals may interact with those oxygen species. That is, ability of metals to deactivate th m could be a measure of their blood compatibility. This in vitro deactivation of the active ox ygen species was investigated and correlated with blood clotting on several metals. Materials and Methods Pieces of metallic specimens (5 ×20×0.1 mm) were cut out of sheets of stainless steel (SUS316 , Japan Industrial Standard), commercially available chemic ally pure titanium, tantalum, zirconium, aluminum, nickel, copper and brass. They were wash ed with acetone and subsequently distilled water in an ultrasonic bath for 5 m in. They were then stored in an decicator until use. Because of short life of •OH, O2 and O2 , direct detection of them is hardly practical hence indirect evaluation was carried out in the present study. Chemicals to be reacted with those active oxygen species were taken as indi cators, such as Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 105-110 doi:10.4028/www.scientific.net/KEM.240-242.105