No abstract

Graphene-based materials (GBMs) are widely used in many fields, including biomedicine. To date, much attention had been paid to the potential unexpected toxic effects of GBMs. Here, we review the recent literature regarding the impact of GBMs on programmed cell death (PCD). Apoptosis, autophagy, and programmed necrosis are three major PCDs. Mechanistic studies demonstrated that the mitochondrial pathways and MAPKs (JNK, ERK, and p38)- and TGF-β-related signaling pathways are implicated in GBMs-induced apoptosis. Autophagy, unlike apoptosis and necroptosis which are already clear cell death types, plays a vital pro-survival role in cell homeostasis, so its role in cell death should be carefully considered. However, GBMs always induce unrestrained autophagy accelerating cell death. GBMs trigger autophagy through inducing autophagosome accumulation and lysosome impairment. Mitochondrial dysfunction, ER stress, TLRs signaling pathways, and p38 MAPK and NF-κB pathways participate in GBMs-induced autophagy. Programmed necrosis can be activated by RIP kinases, PARP, and TLR-4 signaling in macrophages after GBMs exposure. Though apoptosis, autophagy, and necroptosis are distinguished by some characteristics, their numerous signaling pathways comprise an interconnected network and correlate with each other, such as the TLRs, p53 signaling pathways, and the Beclin-1 and Bcl-2 interaction. A better understanding of the mechanisms of PCD induced by GBMs may allow for a thorough study of the toxicology of GBMs and a more precise determination of the consequences of human exposure to GBMs. These determinations will also benefit safety assessments of the biomedical and therapeutic applications of GBMs.

Modifying the surface of the transmucosal area is a key research area because this process positively affects the three functions of implants: attachment to soft tissue, inhibiting bacterial biofilm adhesion, and the preservation of the crestal bone. To exploit the potential of titania nanotube arrays (TNTs) with or without using bovine serum albumin (BSA) to modify the surface of a dental implant in contact with the transmucosal area, BSA was loaded into TNTs that were fabricated by anodizing Ti sheets; the physical characteristics of these arrays, including their morphology, chemical composition, surface roughness, contact angle, and surface free energy (SFE), were assessed. The effect of Ti surfaces with TNTs or TNTs-BSA on human gingival fibroblasts (HGFs) was determined by analyzing cell morphology, early adhesion, proliferation, type I collagen ( COL-1 ) gene expression, and the extracellular secretion of COL-1. The results indicate that early HGF adhesion and spreading behavior is positively correlated with surface characteristics, including hydrophilicity, SFE, and surface roughness. Additionally, TNT surfaces not only promoted early HGF adhesion, but also promoted COL-1 secretion. BSA-loaded TNT surfaces promoted early HGF adhesion, while suppressing late proliferation and COL-1 secretion. Therefore, TNT-modified smooth surfaces are expected to be applicable for uses involving the transmucosal area. Further study is required to determine whether BSA-loaded TNT surfaces actually affect closed loop formation of connective tissue because BSA coating actions in vivo are very rapid.

Evidence indicates that microRNAs (miRNAs) play vital roles in regulating osteogenic differentiation and bone formation. Methods : Here, we show that a polyethyleneimine (PEI)-functionalized graphene oxide (GO) complex efficiently loaded with the miR-214 inhibitor is assembled into silk fibroin/hydroxyapatite (SF/HAP) scaffolds that spatially control the release of the miR-214 inhibitor. Results : SF/HAP/GO scaffolds with nanosized GO show high mechanical strength, and their hierarchical microporous structures promote cell adhesion and growth. The SF/HAP/GO-PEI scaffolds loaded with mir-214 inhibitor (SF/HAP/GPM) were tested for their ability to enhance osteogenic differentiation by inhibiting the expression of miR-214 while inversely increasing the expression of activating transcription factor 4 (ATF4) and activating the Akt and ERK1/2 signaling pathways in mouse osteoblastic cells (MC3T3-E1) in vitro . Similarly, the scaffolds activated the osteoblastic activity of endogenous osteoblast cells to repair critical-sized bone defects in rats without the need for loading osteoblast cells. Conclusion : This technology is used to increase osteogenic differentiation and mineralized bone formation in bone defects, which helps to achieve cell-free scaffold-based miRNA-inhibitor therapy for bone tissue engineering.

The canonical Wnt/β-catenin signaling is important in the differentiation of human mesenchymal stem cells into osteoblasts. Accumulating evidence suggests that the expression of β-catenin is, in part, regulated by specific microRNAs (miRNAs). The aim of the present study was to investigate the putative roles of miRNAs in osteoblast differentiation. Polymerase chain reaction (PCR) arrays were used to identify miRNAs that were differentially expressed between differentiated and non-differentiated periodontal ligament stem cells (PDLSCs), and reverse transcription-quantitative PCR (RT-qPCR) was used for validation. Since miR-214 was revealed to be significantly downregulated during PDLSC differentiation, its function was further investigated via silencing and overexpression. In addition, osteogenic differentiation of PDLSCs was evaluated at 10 and 21 days following induction, using Alizarin red staining and RT-qPCR analysis for mRNA expression levels of the osteogenic differentiation markers alkaline phosphatase (ALP), osteocalcin and bone sialoprotein. Furthermore, the potential target genes of miR-214 were investigated using a dual-luciferase reporter assay, RT-qPCR and western blot analysis, whereas a TOPflash/FOPflash reporter plasmid system followed by a luciferase assay was used to examine the effects of miR-214 on Wnt/β-catenin signaling. The present results demonstrated that miR-214 was significantly downregulated during the osteoblastic differentiation of PDLSCs. Notably, its overexpression inhibited PDLSC differentiation, whereas its knockdown promoted PDLSC differentiation, as revealed by alterations in mRNA expression of osteoblast-specific genes and ALP. In addition, miR-214 was demonstrated to directly interact with the 3′-untranslated region of the β-catenin gene CTNNB1, and suppressed Wnt/β-catenin signaling through the inhibition of β-catenin. The results of the present study suggested that miR-214 may participate in the regulation of the Wnt/β-catenin signaling pathway, and may have potential as a candidate target for the development of preventive or therapeutic agents for the treatment of patients with osteogenic disorders.