BACKGROUND:Micro-arc oxidation technique is used to modify the surface properties of titanium and titanium al oy.
OBJECTIVE:To explore the surface properties of micro-arc oxidation film and its effect on the attachment, proliferation and alkaline phosphatase activity of MC3T3-E1.
METHODS:Forty-six pure titanium discs, 10 mm in diameter and 2 mm in thickness, were randomly divided into two groups. The discs of the experimental groups were treated by micro-arc oxidation technique in an electrolytic solution containing 0.02 mol/L sodiumβ-glycerophosphate and 0.2 mol/L calcium acetate;while the discs of the control group was machine-polished. The surface appearance of the discs was observed by a scanning electron microscopy, the ratio of calcium to phosphorus on the coating surface was detected by X-ray spectroscopy, and the crystal ine phase composition of the coating was detected by X-ray diffraction analysis. cellular morphology in the process of attachment was observed under the scanning electron microscope. cellproliferation was determined by cellcounting kit-8 at 2, 4, 74 days, while alkaline phosphatase activity were determined at 7 and 14 days.
RESULTS AND CONCLUSION:After micro-arc oxidation treatment, a rough and porous calcium-phosphate film was formed on the surface of titanium. The elements of micro-arc oxidation coating main mainly included Ca, P, O and Ti, and the micro-arc oxidation film was mainly composed of titanium oxide, calcium titanate, calcium phosphate and calcium metaphosphate. Under the scanning electron microscope, pseudopods appeared to grow out of the cells on the surface of micro-arc oxidation coating after 1 hour culture, and the typical morphology of the MC3T3-E1 cells could be observed at 4 hours. MC3T3-E1 proliferation (4 and 7 days of culture) and alkaline phosphatase activity (7 and 14 days of culture) were enhanced significantly in the micro-arc oxidation group compared with the control group. These findings indicate that the rough and porous calcium-phosphate coating produced by micro-arc oxidation technique on pure titanium surface could promote the early attachment, proliferation and osteogenic differentiation of MC3T3-E1.

Objective:To explore the value of bedside chest radiograph in the diagnosis and follow-up of severe and critical COVID-19.Methods:Twenty-nine patients with severe or critical COVID-19 were collected from January 23 to February 23, 2020，from four COVID-19 designated hospitals in Guangdong Province. Bedside radiography was taken in all the 29 patients, ranged from 1 to 16 times for each patient. Twenty-seven patients underwent follow-up, and the number of re-examination ranged 1 to 15 times, and the interval of review is 1 to 8 days.The imaging findings of bedside chest radiography and the imaging changes on follow-up chest radiography were analyzed retrospectively.Results:Twenty-nine patients were collected. The radiography showed the lesions involved all more than 3 lung fields. The films showed consolidation shadow in 19 cases, multiple patches of shadow in 23 cases, reticular pattern in 12 cases, strips shadow in 14 cases, interlobar fissure thickening in 18 cases, and "white lung" in 4 cases.The complications included pleural effusion in 4 cases, pneumothorax in 2 cases, mediastinal and subcutaneous emphysema in 1 case. The radiography showed the lesions progressed in 15 cases, with expanded involvement of the lung.The increase of lesion density was found in 6 cases, new lesions were noted in 5 cases, while both of them were found in 4 cases. Nine cases showed improvement, with reduced range and decreased density. Patchy or consolidation shadow turned to strips shadow or articular pattern shadow in 8 cases.There was no significant change in 3 cases with large consolidation shadow.Conclusions:Bedside chest radiography has a good value in the follow-up of severely and critically ill patients with COVID-19, and can provide great help for clinicians to evaluate their condition.