ABSTRACT
The daily life of people in the intelligent age is inseparable from electronic device, and a number of bacteria on touch screens are increasingly threatening the health of users. Herein, a photocatalytic TiO2/Ag thin film was synthesized on a glass by atomic layer deposition and subsequent in situ reduction. Ultraviolet-visible (UV-Vis) spectra showed that this film can harvest the simulated solar light more efficiently than that of pristine TiO2. The antibacterial tests in vitro showed that the antibacterial efficiency of the TiO2/Ag film against S. aureus and E. coli was 98.2% and 98.6%, under visible light irradiation for 5 min. The underlying mechanism was that the in-situ reduction of Ag on the surface of TiO2 reduced the bandgap of TiO2 from 3.44 to 2.61 eV due to the formation of Schottky heterojunction at the interface between TiO2 and Ag. Thus, TiO2/Ag can generate more reactive oxygen species for bacterial inactivation on the surface of electronic screens. More importantly, the TiO2/Ag film had great biocompatibility with/without light irradiation. The platform not only provides a more convenient choice for the traditional antibacterial mode but also has limitless possibilities for application in the field of billions of touch screens.
ABSTRACT
Osteogenesis of mesenchymal stem cells (MSCs) is essential for bone repair. Recently, microRNAs have been proven to play an important role in the regulation of MSC differentiation, including osteogenesis. Here, the function of microRNA-21 (miR-21) in the osteogenic differentiation of human umbilical cord mesenchymal stem cells (hUMSCs) was investigated. Briefly, the miR-21 mimics (m-miR-21) and the antisense miR-21 (as-miR-21) were transfected to hUMSCs, and the capacity of miR-21 for the osteogenic differentiation of hUMSCs was evaluated by the expression of osteogenic markers encoding alkaline phosphatase (ALP), runt-related gene-2 (RUNX-2) and osteocalcin (OCN), as well as by Alizarin red S staining. The results indicated that the overexpression of miR-21 elevated the expression level of the osteogenesis-related genes of hUMSCs. During this process, the PI3K-AKT signaling pathway activity had an increasing tendency responding to miR-21 up-regulation. This enhancement promoted the phosphorylation of GSK-3ß, leading to the stabilization and high concentration accumulation of ß-catenin in cytoplasm to activate the transcription of RUNX-2, and finally increased the osteogenesis of hUMSCs. This work demonstrated that miR-21 and its target PI3K-AKT-GSK3ß pathway played an important role in the osteogenic differentiation of hUMSCs by stabilizing ß-catenin.
