Flexible doctor blade-coated abiotic cathodes for implantable glucose/oxygen biofuel cells

Implantable devices powered by batteries have been used for sixty years. In recent devices, lithium-based batteries are the most widely used power source. However, lithium batteries have many disadvantages in terms of safety, reliability, and longevity and require regular monitoring and substitution. Implantable glucose biofuel cells (BFCs) are increasingly seen as a potential future technology for replacing lithium-based batteries because they do not require surgical replacement after 8-10 years and have a theoretically unlimited lifetime thanks to the continued recovery of glucose and oxygen present in the human body. This paper shows the fabrication of flexible implantable abiotic cathodes, based on a nitrogen/iron-doped graphene catalyst, for glucose/oxygen biofuel cell application. An ink, based on nitrogen-iron doped graphene as the abiotic catalyst and chitosan as a binder, was prepared and coated on a flexible teflonated gas diffusion layer using doctor blade coating. The characterization of the biocathode shows an open potential circuit corresponding to the potential of the abiotic catalyst and a high oxygen reduction current density of up to 66 μA cm^-2 under physiological conditions. Those cathodes remain stable for up to two years with a current density loss of only 25%. The flexible abiotic electrode cytotoxicity was evaluated by cell culture experiments showing living cells' high tolerance on the biocathode surface. This work demonstrates that this abiotic catalyst can be a promising alternative for the development of implantable glucose BFCs due to its stability and its cytocompatibility.

Effect of core materials for core fabrication for dental implants on in-vitro cytocompatibility of MC3T3-E1 cells

Background

Despite the wide use of dental materials for CAD/CAM system in prosthetic treatment, the effect of the materials, which are used as dental implants core fabricated, on cells involved in dental implant osseointegration is uncertain. This study aimed to investigate and compare the effect of single core materials used for dental implants fabricated by the dental prostheses fabrication process and the CAD/CAM milling method on MC3T3-E1 cells.

Methods

The materials used for prostheses restoration in this experiment were Porcelain Fused Gold (P.F.G), Lithium disilicate glass ceramic (LiSi₂), Zirconia (ZrO₂), Nickel-Chromium (Ni-Cr) and Cobalt-Chromium (Co-Cr). MC3T3-E1 cells were cultured and used, the cell adhesion and morphology were observed and analyzed using confocal laser scanning microscopy (CLSM). Methoxyphenyl tetrazolium salt (MTS) and alkaline phosphatase (ALP) assay were used to observe the cell proliferation and differentiation.

Results

CLSM revealed irregular cell adhesion and morphology and the filopodia did not spread in the Ni-Cr specimen group. Significantly high cell proliferation was observed in the ZrO₂ specimen group. The LiSi₂ specimen group presented significantly high cell differentiation. Intergroup comparison of cell proliferation and differentiation between the Ni-Cr specimen group and all other specimen groups showed significant differences (p < .05).

Conclusion

Cell proliferation and differentiation were observed from the cores, which were fabricated with all specimen groups on cytocompatibility except the Ni-Cr specimen group.

Regulation of osteoblast behaviors via cross-talk between Hippo/YAP and MAPK signaling pathway under fluoride exposure

Titanium is widely used in implant materials, while excessive fluoride may have negative effects on the osseointegration between the titanium and osteoblasts. Although the underlying mechanisms are still not clear, the mitogen-activated protein kinase (MAPK) or Yes-associated protein (YAP) signaling pathways are thought to be involved. This study evaluated the role of Hippo/YAP and MAPK signaling pathway in osteoblast behaviors under excessive fluoride exposure in vitro and in vivo. Commercially pure Ti (cp-Ti) samples were exposed to fluoride (0, 0.1, and 1.0 mM NaF) for 7 days. Cell adhesion was observed using a laser scanning confocal microscope. Cell viability and apoptosis were evaluated by CCK-8 assay and flow cytometry, respectively. The expressions of osteoblast markers and key molecules in MAPK and YAP pathway were detected by Western blot. In vivo studies were evaluated by histology methods in C57/BL6 mice model. Our results showed that 1.0 mM NaF destroyed the passivation film on cp-Ti surface, which further inhibited the osteoblast adhesion and spreading. Meanwhile, compared to other groups, 1.0 mM NaF led to a remarkable reduction in cell viability (P < 0.05), as well as increased apoptosis (P < 0.05) and downregulation of osteogenesis protein expression (P < 0.05). MAPK and YAP signaling pathways were also activated under 1.0 mM NaF exposure, and JNK seemed to regulate YAP phosphorylation in response to NaF impacts on osteoblasts. In vivo fluorosis mouse model further indicated that 100 ppm NaF group (high fluoride group) increased bone resorption and inhibited the nuclear translocation of YAP. The osteoblast behaviors were negatively altered under excessive fluoride, and MAPK/JNK axis contributed to YAP signaling activation in regulating NaF-induced osteoblast behaviors. KEY MESSAGES: • Excessive fluoride inhibited osteoblast behaviors and bone formation. • YAP and MAPK signaling pathways were activated in osteoblasts under fluoride exposure. • Fluoride regulated osteoblast behaviors via the cross-talk between YAP and MAPK.