Formation of carbon-added anatase-rich TiO2 layers on titanium and their antibacterial properties in visible light.

OBJECTIVE: To avoid risk of infections associated with dental implants, thermal oxidation processes for practical dental Ti alloys were studied for both high bonding strength and antibacterial properties in visible light. METHODS: Two-step thermal oxidation, comprising carburization (first step of treatment: in Ar-1%CO gas) and subsequent oxidation (second step of treatment: in air), was conducted on commercially pure (CP) Ti, Ti-6Al-4V (Ti64), and Ti-6Al-7Nb (Ti67) alloys to form TiO2 layers. Their bonding strengths and antibacterial properties against Escherichia coli (E. coli) in visible light (λ ≥ 400 nm) were evaluated. RESULTS: TiO2 layers formed on each metal were composed of anatase and/or rutile. Anatase fraction and carbon concentration in the layers decreased with increasing temperature in the second step of treatment. Antibacterial properties of the TiO2 layers were dependent on the temperature in the second step of treatment. An approximate antibacterial activity value of 2 (killing ∼99% bacteria) was obtained when the temperatures in the second step of treatment were 673 and 773 K for CP Ti, 773 K for Ti64, and 773 and 873 K for Ti67. It was found that the TiO2 layer must contain carbon and be anatase-rich to exhibit excellent antibacterial properties. Bonding strength between the substrate and TiO2 layers formed at 773 K in the second step of treatment exceeded 80 MPa and was independent of substrate type. SIGNIFICANCE: TiO2 layers, possessing both high bonding strength and excellent antibacterial properties, were successfully formed on practical dental Ti alloys via two-step thermal oxidation.

Visible-light-responsive antibacterial activity of Au-incorporated TiO2 layers formed on Ti-(0-10)at%Au alloys by air oxidation.

Rutile TiO2 layers were formed on substrates of Ti-(0-10)at%Au alloys by a simple process of air oxidation, and their antibacterial activities were evaluated under visible-light irradiation (λ ≥ 400 nm). Au was introduced into the TiO2 layers on Ti-(1-10)at%Au alloys and existed as both metallic Au nanoparticles and dissolved Au3+ ions. The TiO2 layers that formed on Ti-5at%Au and Ti-10at%Au alloys exhibited visible-light photocatalytic activity, that is, degradation of stearic acid and antibacterial activity against Escherichia coli. These visible-light activities were attributed to the surface plasmon resonance of metallic Au nanoparticles and the decrease in bandgap energy caused by dissolved Au3+ ions. The formation of hydroxyl radicals observed under visible-light irradiation is attributable to antibacterial activity. From a cost perspective, a Ti-5at%Au alloy is more suitable as a substrate for the formation of a TiO2 layer with antibacterial properties than a Ti-10at%Au alloy. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 991-1000, 2019.

Dietary kakrol (Momordica dioica Roxb.) flesh inhibits triacylglycerol absorption and lowers the risk for development of fatty liver in rats.

Kakrol (Momordica dioica Roxb.) is a cucurbitaceous vegetable native to India and Bangladesh. Bitter gourd (Momordica charantia Linn.), a species related to kakrol, has been shown to have pharmacological properties including antidiabetic and antisteatotic effects. In this study, we investigated the effect of dietary kakrol on lipid metabolism in rats. Sprague-Dawley rats were fed AIN-76 formula diets containing 3% freeze-dried powders of whole kakrol or bitter gourd for two weeks. Results showed significantly lowered liver cholesterol and triacylglycerol levels in rats fed on both diets. Fecal lipid excretion increased in rats fed the kakrol diet, and lymphatic transport of triacylglycerol and phospholipids decreased in rats fed the kakrol diet after permanent lymph cannulation. Furthermore, n-butanol extract from kakrol caused a significant concentration-dependent decrease in the pancreatic lipase activity in vitro. These results indicate that the mechanisms of action on lipid metabolism in kakrol and bitter gourd are different and that dietary kakrol reduces liver lipids by inhibiting lipid absorption.