Horseradish peroxidase (HRP) and toluidine blue (TB) were incorporated in polyion complex membrane composed of double stranded DNA(dsDNA) and chitosan prepared on the surface of an glassy carbon (GC) disk electrode to fabricate highly sensitive and selective reagentless H2O2 biosensor. The embedded-TB in the DNA/chitosan membrane exhibited excellent electrochemical redox property with an electron transfer rate constant of 3.12 ± 0.5 sec−1, and shuttled electron effectively from the base GC electrode to catalytic center of the HRP. Under the applied potential of -0.22V (versus Ag/AgCl) and pH 7.0, the resulting electrode (HRP/DNA–TB/chitosan/GCE) exhibited rapid (<10 s) and sensitive response to H2O2. The calibration curve of H2O2, plotting steady-state cathodic current versus H2O2 concentration, was linear up to 0.1mM with a detection limit of 1 μM H2O2 (S/N = 3). The H2O2 response was scarcely interfered by ascorbic acid and uric acid, which potentially reduce oxidized intermediate of the HRP and interfere with the response of peroxidase-based electrodes.
Spinal fusion is one of the most common surgical interventions for spine reconstruction. Despite the efforts to promote osteogenesis after spinal fusion, osteogenesis after spinal fusion remains a clinical challenge and new methods are still needed. The bone morphogenetic protein-2 (BMP-2) is a widely reported factor that can facilitate the osteogenesis in spinal fusion. In previous research, we found that the delivery of chitosan nanospheres could promote the effects of BMP-2 on osteogenic activity. The coralline hydroxyapatite (CHA) is one of the most frequently used implants in bone fusion. However, up to now no study has focused on the osteogenic efficacy of the CHA composite with recombinant human BMP-2 (rhBMP-2)-loaded chitosan nanospheres. This study aimed to investigate the effects of the CHA implant with rhBMP-2-loaded chitosan nanospheres on osteogenesis in spinal fusion. Methods: The rhBMP-2-loaded microspheres and CHA composite (rhBMP-2 microspheres/CHA) were prepared and were used for implantation of the rats. All SD rats were divided into four groups: the rhBMP-2 microspheres/CHA composite group (containing 0.5 mg rhBMP-2), the rhBMP-2-loaded CHA (rhBMP-2/CHA) composite group (containing 0.5 mg rhBMP-2), the blank CHA group, and the negative control group. The microsphere morphology was scanned and analyzed using a scanning electron microscope. Micro-computed tomography examination and three-dimensional reconstruction were performed 4 weeks after the surgery. Hematoxylin and eosin staining was conducted for histological analysis. Both alkaline phosphatase (ALP) and calcium content were measured. Results: The rhBMP-2-loaded CHA (rhBMP-2/CHA) composite was successfully prepared. Spherical regularity and a smooth and unwrinkled surface of the spheres were observed in all chitosan (CS)/rhBMP-2 microspheres. No side effects, infections, or abnormal behaviors were found in the animals. After 4 weeks of surgery, obvious new bone formation and bone fusion could be observed around the implant in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group. No ectopic osteogenesis was found in the vertebral canal or other muscle tissues. After 4 weeks of implantation, in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group, osteoid tissues could be found, and bone cells, bone marrow, and trabecular bone turned into mature sclerotin, obvious bone tissue formation could be also seen. Both ALP activity and calcium content in the rhBMP-2 microspheres/CHA composite group (6.52 ± 0.50 kat/g and 17.54 ± 2.49 μg/mg) were significantly higher than in all other groups. Conclusion: The composite with rhBMP-2-loaded CS nanospheres could enhance osteogenic efficacy and increase the ALP activity and calcium content. These results might provide a novel method for osteogenesis in spinal fusion and offer new insight into the role of BMP-2 in osteogenesis.
The electrochemical behavior of a new magnesium alloy (AZ61) containing rare earth elements-cerium (Mg-Al-Zn-Mn-Ce alloys) was investigated in 3% NaCl electrolyte using electrochemical methods such as linear sweep voltammetry, Tafel curves and electrochemical impedance spectroscopy. Scanning electron microscopy was used to characterize the surface morphologies of magnesium and its alloys. The results shows that compared with that of the most commonly used Mg alloy–AZ61, the cerium containing magnesium alloy exhibited higher electrochemical activity, and higher corrosion resistance. The electrochemical activity of Mg-Al-Zn-Mn-Ce was higher than that of Mg and Mg-Al-Zn-Mn-Ce alloys in 3% NaCl. The corrosion resistive order decreased in the following sequence: Mg-Al-Zn-Mn-Ce > Mg-Al-Zn-Mn > Mg. The electrolytes favored anodic magnesium oxidation, but the alloying element of Ce facilitated the formation of dense passive films on alloy surfaces.
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