Color stability and surface roughness of chitosan- and nanodiamond-modified bisacrylic resin

Abstract: The aim of this study is to evaluate the effect of chitosan or nanodiamond incorporation on the color stability and surface roughness of a bisacrylic resin subjected to artificial aging. Four bisacrylic resins were evaluated, namely, control, chitosan-modified material, nanodiamond-modified material, and chitosan-nanodiamond-modified material. Twenty-four specimens were prepared for each material. The surface roughness was determined using a profilometer with a cut-off of 0.25 mm. The baseline color was measured according to the CIE L*a*b* system using a reflectance spectrophotometer. After these tests, the specimens were individually immersed in cola soft drink, red wine, or distilled water (n = 8) for 28 days. After the aging, the surface roughness and final color were re-evaluated. The color stability was determined using the difference between the coordinates obtained before and after the aging process. The data on roughness and color change were evaluated using ANOVA and the Tukey test (α = 0.05). The results show that the incorporation of nanodiamonds and chitosan into a bisacrylic resin provided a better color stability to the materials (p = 0.007). The storage in red wine resulted in a higher variation in the surface roughness values, especially when only the nanodiamond was incorporated to the material (p < 0.05). The incorporation of both chitosan and nanodiamonds are promising in providing an improvement in the properties of the bisacrylic resin when they are simultaneously incorporated in the product.

The effect of nanodiamonds on candida albicans adhesion and surface characteristics of PMMA denture base material - an in vitro study

Abstract Candida albicans is the main causative pathogen of denture stomatitis, which affects many complete denture patients. Objective: To evaluate the effect of different concentrations of nanodiamonds (NDs) added to polymethyl methacrylate (PMMA) denture base material on Candida albicans adhesion as well as on surface roughness and contact angle. Methodology: Acrylic resin specimens sized 10×10×3 mm3 were prepared and divided into four groups (n=30) according to ND concentration (0%, 0.5%, 1%, 1.5% by wt). Surface roughness was measured with a profilometer, and the contact angle with a goniometer. The effect of NDs on Candida albicans adhesion was evaluated using two methods: 1) slide count and 2) direct culture test. Analysis of variance (ANOVA) and Tukey's post hoc test were used in the statistical analyses. Results: Addition of NDs decreased the Candida albicans count significantly more than in the control group (p<0.05), with a lowest of 1% NDs. Addition of NDs also significantly decreased the surface roughness (p<0.05), but the contact angle remained the same. Incorporation of NDs into the PMMA denture base material effectively reduced Candida albicans adhesion and decreased surface roughness. Conclusion: PMMA/NDs composites could be valuable in the prevention of denture stomatitis, which is considered one of the most common clinical problems among removable denture wearers.

Carboxyl nanodiamond as intracellular transporters of anticancer drug--podophyllotoxin / 药学学报

The purpose of this study is to investigate the intracellular transporters effect and the cytotoxicity of carboxyl nanodiamond (CND) - podophyllotoxin (PPT). Nanodiamond (ND) was treated with mixed carboxylic acid and finally got 64 nm CND by centrifugation, and then it was reacted with PPT to form CND-PPT. UV spectrophotometry was used to calculate the content of PPT in CND-PPT, the particle size distribution and zeta potential were measured by Dynamic laser scattering instrument. CND, PPT, CND-PPT and CND + PPT (physical mixture of CND and PPT) were characterized by Fourier transform infrared spectroscopy, at the same time, thermal analysis and element analysis were used to estimate the content of the PPT in CND-PPT. The affect of CND, PPT, CND-PPT on HeLa cell was measured with MTT assay. The results showed that content of PPT combined with CND accounted for about 10%. MTT assay showed that CND has low cytotoxicity and CND-PPT can increase the water soluble of PPT. As a conclusion, CND as a hydrophilic pharmaceutical carrier combined with PPT is able to increase the water solubility of PPT, at low concentration, CND-PPT can enhance the antitumor activity in comparison with PPT, so CND can be used as a potential anticancer drug carrier.