Study on Occluding Dentinal Tubules with a Nanosilver-Loaded Silica System In Vitro.

The effects of most clinical treatments for dentin hypersensitivity are not long-lasting. To overcome the defects, the mesoporous silica nanoparticles and silver nanoparticles entered the field of oral materials. This study aimed to synthesize a novel, low-cytotoxic dentin desensitizer and investigate its occlusion effects on dentinal tubules. The biphasic stratification approach, a chemical reduction method, and the Stöber method were used to synthesize silver nanoparticle-loaded and nonporous silica-encapsulated mesoporous silica (Ag-MSNs@nSiO2), which was a noncrystalline structure with an average size of approximately 128 nm and a silver content of 3.506%. Atomic absorption spectrometry and the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide cell viability assay showed that Ag-MSNs@nSiO2 slowly released silver ions and had nearly no cytotoxicity. An electron microscope was used to observe the blocking effects on the dentinal tubules of sensitive tooth disc models, which were randomly divided into the following four groups: a deionized water group, a 5.9 M silver nitrate solution group, an Ag-MSNs@nSiO2 group, and a Gluma desensitizer group. There were no significant differences in the relative area of open dentinal tubules between the Ag-MSNs@nSiO2 group and the Gluma desensitizer group (P > 0.05). Detection of protein structures showed that multilevel structures of bovine serum albumin in dentin tubules were significantly changed by silver ions from Ag-MSNs@nSiO2. These results suggest that nearly noncytotoxic Ag-MSNs@nSiO2 was successfully synthesized by a series of methods. Ag-MSNs@nSiO2 occluded dentin tubules immediately and effectively. Moreover, the blockage effects may be enhanced and maintained by continuous condensation of proteins in dentinal tubules.

Nuclear import of Nkx2-2 is mediated by multiple pathways.

Nkx2-2 homeoprotein is essential for the development of the central nervous system and pancreas. Although the nuclear localization signals of Nkx2-2 have been identified, the responsible transport receptor is still unknown. Here, we demonstrate that imp α1 not only interacts with Nkx2-2 but also transports it into the nucleus in vitro by acting together with imp ß1. However, the nuclear import of Nkx2-2 in cells was not inhibited in response to knockdown expression of endogenous imp ß1 or over-expression of Bimax2. Furthermore, imp ß1 and imp 13, but not imp 4, directly interact with Nkx2-2 and are capable of transporting Nkx2-2 in an in vitro import assay. By GST pull-down assay, we demonstrate that mutation of NLS1 or NLS2 has no effect on interaction with imp α1 or imp 13, but significantly reduced binding to imp ß1. Thus, the nuclear import of Nkx2-2 is mediated not only by the classical import pathway but also directly by imp ß1 or imp 13.