Bone defects and periodontal disease are pathological conditions that may become neglected diseases if not treated properly. Hydroxyapatite (HA), along with tricalcium phosphate and bioglass ceramic, is a biomaterial widely applied to orthopedic and dental uses. The in vivo performance of HA is determined by the interaction between HA particles with bone cells, particularly the bone mineralizing cells osteoblasts. It has been reported that HA-induced osteoblastic differentiation by increasing the expression of osteogenic transcription factors. However, the pathway involved and the events that occur in the cell membrane have not been well understood and remain controversial. Advances in gene editing and the discovery of pharmacologic inhibitors assist researchers to better understand osteoblastic differentiation. This review summarizes the involvement of extracellular signal-regulated kinase (ERK), p38, Wnt, and bone morphogenetic protein 2 (BMP2) in osteoblastic cellular regulation induced by HA. These advances enhance the current understanding of the molecular mechanism of HA as a biomaterial. Moreover, they provide a better strategy for the design of HA to be utilized in bone engineering.

Bovine bone is a considerable source for the production of hydroxyapatite. The recent study reported a novel method to extract hydroxyapatite from bovine bone without producing hazardous residue. The bovine bones were cut and boiled in the opened chamber followed by boiling in pressurized tank. The bones were then soaked into 95% ethanol. Calcination was then conducted in 800°C, 900°C and 1,000°C, for 2 hours. The result was then grinded and sieved. The powder then was characterized using Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) to measure the purity of hydroxyapatite. It is concluded that the hydroxyapatite derived from this process showed 100% purity, resulting 35.34 ± 0.39% w/w from the wet bone weight and 72.3% w/w from the dried weight. The present extraction method has been proven to yield high amount of pure hydroxyapatite as well as reducing the use of hazardous reagent.

Osteomyelitis is an infectious disease which is also a major complication of bone defects. This study aims to determine the effect of bovine hydroxyapatite-gelatin-based bone implants with gentamicin as an antibiotic (BHA-GEL-GEN implant) on the regeneration of bone defects in vivo. The BHA-GEL-GEN and BHA-GEL implants were made by direct compression. In vivo study was carried out with Wistar rats. The rats were divided into three groups: negative control, BHA-GEL implant, and BHA-GEL-GEN implants. The defect model used was the burr hole defect model with diameter 2.2mm and 2mm deep. After 2, 7, 14, and 28 days, the rats were sacrificed. Bone integrity was carried out using X-ray radiography. Radiological examination was performed using haematoxylin and eosin (HE) staining and immunohistochemical techniques with anti-vascular endothelial growth factor (VEGF) and anti-alkaline phosphatase (ALP) antibodies. Based on the radiograph, the implanted group had accelerated bone growth in the defect area. Semiquantitative data from HE staining showed that the implanted group had accelerated migration of osteoclasts, osteoblasts, and osteocytes in the defect area. The immunoreactive score showed that the BHA-GEL-GEN group had higher VEGF expression compared to two other groups. The three groups did not provide a significant difference in ALP expression. In conclusion, the BHA-GEL-GEN implant causes accelerated bone defects repair by accelerating tissue vascularity and does not interfere with the bone remodeling process. Therefore, the BHA-GEL-GEN implant is potentially a biomedical material for osteomyelitis therapy.

Background: Osteoarthritis (OA) is a chronic disease in the joints. One of the proinflammatory cytokines that is thought to have a major role in the inflammatory process, the emergence of pain, and cartilage damage in OA is tumor necrosis factor α (TNF-α). Meloxicam is a nonsteroidal anti-inflammatory drug class of drugs that is relatively selective in inhibiting the activity of cyclooxygenase 2 (COX-2) formation. This study is conducted to prove the change in TNF-α level in the use of meloxicam with model in animals suffering from OA. Methods: The OA rat model was induced with sodium monoiodoacetate intra-articularly. Rats were divided into 5 groups: negative control group, positive control group, and treatment groups with various doses of meloxicam. Hyperalgesia effect was evaluated using a warm plate test, and TNF-α level was determined using enzyme-linked immunosorbent assay. Results: The treatment groups that received meloxicam at a dose of 1.0, 3.0, or 10.0 mg/kg body weight (BW) did not show significant differences in rat knee joint diameter (p = 0.99), but showed a significant difference in sensitivity to heat stimulation (p = 0.02) compared to the control group. Osteoarthritis rats experienced a significant reduction in TNF-α level after being given meloxicam at a dose of 10 mg/kg BW compared with the control group. This shows that the 10 mg/kg BW of meloxicam is a potential dose in reducing the TNF-α level in OA rat models. Conclusions: Based on these data, it can be concluded that the inhibition of pain and the development of OA by meloxicam in animal models may be assigned to a decreased level of TNF-α.

Submicron hydroxyapatite has been reported to have beneficial effects in bone tissue engineering. This study aimed to fabricate submicron-scale bovine hydroxyapatite (BHA) using the high-energy dry ball milling method. Bovine cortical bone was pretreated and calcined to produce BHA powder scaled in microns. BHA was used to fabricate submicron BHA with milling treatment for 3, 6, and 9 h and was characterized by using dynamic light scattering, scanning electron microscope connected with energy dispersive X-Ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffractometry to obtain its particle size, calcium-to-phosphorus (Ca/P) ratio, functional chemical group, and XRD peaks and crystallinity. Results showed that the particle size of BHA had a wide distribution range, with peaks from ~5 to ~10 µm. Milling treatment for 3, 6, and 9 h successfully gradually reduced the particle size of BHA to a submicron scale. The milled BHA’s hydrodynamic size was significantly smaller compared to unmilled BHA. Milling treatment reduced the crystallinity of BHA. However, the treatment did not affect other characteristics; unmilled and milled BHA was shaped hexagonally, had carbonate and phosphate substitution groups, and the Ca/P ratio ranged from 1.48 to 1.68. In conclusion, the fabrication of submicron-scale BHA was successfully conducted using a high-energy dry ball milling method. The milling treatment did not affect the natural characteristics of BHA. Thus, the submicron-scale BHA may be potentially useful as a biomaterial for bone grafts.

Traditional small-scale gold mining mostly use mercury to extract the gold from ores. However, mercury contamination in the environment can affect the composition and structure of the bacterial community. The purpose of this study was to determine the effect of mercury contamination on the bacterial community in the traditional gold mining waste disposal site and in the rice field. Mercury analysis was carried out using the CVAFS method. Analysis of bacterial communities and structure was carried out based on the results of metabarcoding of the V3-V4 16S rRNA regions obtained from paired-end Illumina MiSeq reads. The results showed that the sample from the mining waste disposal site had a mercury level of 230 mg/kg, while the sample from the rice field had 3.98 mg/kg. The results showed that there were differences in microbial composition and community structure in both locations. With the total reads of 57,031, the most dominant phylum was Firmicutes in the mining disposal site sample. Meanwhile, with the total reads of 33,080, the sample from rice field was dominated by Planctomycetes. The abundant classes of bacteria in the mining waste disposal site, from the highest were Bacilli, Gammaproteobacteria and Planctomycetia, while the sample from the rice field was dominated by the Planctomycetia and Acidobacteria subdivision 6. The families that dominated the sample in disposal site were Bacillaceae and Aeromonadaceae, while the sample from the rice field was dominated by Gemmataceae. The abundant genera in both locations were Bacillus and Gemmata. This study concluded that the high level of mercury in the soil reduced the richness and diversity of bacterial phyla and lower taxa. There was also a shift in the dominance of phyla and lower taxa in both locations. This study provides an understanding of the microbial community structure in the area that is highly contaminated with mercury to open insight into the potential of these bacteria for mercury bioremediation.