ABSTRACT
Objective To investigate elastic modulus of double-stranded DNA (dsDNA) biofilm adsorbed on microcantilever substrate. Methods Parsegian’s empirical potentials based on mesoscopic continuum liquid crystal theory was employed to describe the interaction energy among coarse-grained DNA cylinders; Monte Carlo method was used to simulate the distribution pattern of DNA chains before and after loading. The thought experiment method combined with the compression bar model in the sense of macroscopic continuum mechanics was adopted to predict the elastic modulus of DNA biofilm. Results The elastic modulus of dsDNA biofilm ranged from 0.1 MPa to 80 MPa. Conclusions It was found out that the classic hypothesis with uniform hexagonal pattern may underestimate the elastic modulus of DNA biofilm when compared with that in random pattern. Moreover, either the increase of packing density or the decrease of buffer salt concentration will help to enhance elastic modulus of DNA biofilm. These results have great significances in further understanding the mechanical properties and regulation rules of DNA biofilm related with clinical work.
ABSTRACT
BACKGROUND: Microarc oxidation (MAO) is a break-through anodyzing technology for forming oxide films on valve metal.Use of this technology allows thick, porous oxide layers to be formed on the surface of pure titanium. Few biocompatibility reports using this treatment have been found.OBJECTIVE: The blood compatibility of a novel surface modified titanium substrata biomaterial using MAO was investigated.DESIGN: Positive and negative control, contrast observation and gold standard control.SETTING: Wuhan Union Hospital.MATERIALS: A healthy male adult New-Zealand rabbit, weighing 2.5 kg and ordinary grade, was selected in this study.Pure titanium sticks TA1 (Baoji Yingnaite Non-ferrous Metal Co., Ltd.), MAO-Ti and 20 g/L potassium oxalate were also selected in this study.METHODS: The study was carried out in the Laboratory of General Surgery, Union Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology in May 2006. ① Materials: Titanium substrate of 10 mm in diameter and 2 mm in depth was put in an electrolyte which was quipped with deionized water, dibasic sodium phosphate, and ethanoic acid calcium for MAO treatment for 10 minutes. ② Groups: Three groups were analysed: test group, negative control group and positive control group. Test group: MAO-Ti was dipped in 10 mL saline; Positive control group: 10 mL deionized water was added in each tube; Negative control group: 10 mL saline was added in each tube. ③ Operation: Fresh whole blood was collected from rabbit and then mixed with the liquids in the three groups respectively after anti-coagulation. In addition, UV-Visible Spectrophotometer was used to evaluate the hemolytic ratio. A hemolytic ratio below or equal to 5% indicated that this novel material fitted the requirements. On the contrary, a hemolytic ratio higher than 5% proofed the existence of a hemolyzation.MAIN OUTCOME MEASURES: The hemolytic ratio of materials in three groups.RESULTS: The hemolytic ratio of the test group was 0.90%. The result indicated that this new material had no haemolysis effect.CONCLUSION: The material does not resolve red blood cells and is coincident with the international and governmental standard.