RESUMEN
In this study, the interplay between the structural complexity, microstructure, and mechanical properties of calcium phosphates (CaPs) derived from fish bones, prepared at various calcination temperatures, and their corresponding sintered ceramics was explored. Fourier-transform infrared analysis revealed that the calcined powders primarily consisted of hydroxyapatite (HAp) and carbonated calcium hydroxyapatite, with an increasing concentration of Mg-substituted ß-tricalcium phosphate (ß-TCP) as the calcination temperature was increased. X-ray diffraction patterns showed enhanced sharpness of the peaks at higher temperatures, indicating a larger crystallite size and improved crystallinity. The ceramics exhibited a significantly larger crystallite size and an increased concentration of the ß-TCP phase. Rietveld analysis revealed a larger volume of the ß-TCP phase in the ceramics than in their calcined powders; this could be attributed to a newly formed ß-TCP phase due to the decomposition of HAp. Extended X-ray absorption fine structure analysis revealed the incorporation of Mg in the Ca2 site of HAp, Ca2 site of ß-TCP, and Ca5 site of ß-TCP, with a higher substitution of Mg in the Ca5 site of ß-TCP at elevated temperatures. The mechanical properties of HAp ceramics can be improved by increasing the calcination temperature because of their improved relative density and dense porous structure at elevated temperatures. This comprehensive investigation sheds light on the phase evolution, microstructural changes, and consequential impact on the mechanical properties of CaPs derived from fish bones, thereby facilitating the development of tailored CaP ceramics for biomedical applications.
RESUMEN
The comprehensive control of hydroxyapatite (HAp), involving morphological and structural variations, particle sizes, and defect formations, has garnered considerable attention for its versatile functionalities, rendering it applicable in diverse contexts. This work examined the shape, structure and optical characteristics, and defect formation in hydroxyapatite (HAp) extracted from Nile tilapia (Oreochromis niloticus) scales with various pre-treatments through experiments and density functional theory (DFT) calculations. Utilizing scanning electron microscopy, our findings revealed that dried fish scales (FS-D) exhibited a layered pattern of collagen fibers, while boiled fish scales (FS-B) had smoother surfaces and significantly reduced collagen content. After calcination, the FS-D sample produced nanorods with an average length of 150 ± 44 nm, whereas the FS-B samples yielded agglomerated spherical particles whose size increased with the rising calcining temperature. In-depth analysis through X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the presence of biphasic calcium phosphates in the FS-B samples, while the FS-D sample presented a pure HAp phase. The boiled fish scale calcined at 800 °C (FS-B800) exhibited an optical band gap (Eg) of 5.50 eV, whereas the dried fish scale calcined at 800 °C (FS-D800) showed two Eg values of 2.87 and 3.97 eV, as determined by UV-visible spectroscopy. DFT calculations revealed that the band gap of 3.97 eV correlated with OH- vacancies, while that of 2.87 eV indicated Mn-substituted HAp, explaining the blue powder. The Eg value for the white powder resembled pure HAp, S- and Cl- substituted OH- vacancies, and various cations substituting Ca sites of HAp. Different pre-treatment procedures influence the characteristics of HAp, offering opportunities for applications in bone replacement and scaffolds for bone tissue engineering.
RESUMEN
This work aimed to develop new antibiotic-coated/ antibiotic-loaded hydroxyapatite (HAp) scaffolds for orthopaedic trauma, specifically to treat the infection after fixation of skeletal fracture. The HAp scaffolds were fabricated from the Nile tilapia (Oreochromis niloticus) bones and fully characterized. The HAp scaffolds were coated with 12 formulations of poly (lactic-co-glycolic acid) (PLGA) or poly (lactic acid) (PLA), blended with vancomycin. The vancomycin release, surface morphology, antibacterial properties, and the cytocompatibility of the scaffolds were conducted. The HAp powder contains elements identical to those found in human bones. This HAp powder is suitable as a starting material to build scaffolds. After the scaffold fabrication, The ratio of HAp to ß-TCP changed, and the phase transformation of ß-TCP to α-TCP was observed. All antibiotic-coated/ antibiotic-loaded HAp scaffolds can release vancomycin into the phosphate-buffered saline (PBS) solution. PLGA-coated scaffolds obtained faster drug release profiles than PLA-coated scaffolds. The low polymer concentration in the coating solutions (20%w/v) gave a faster drug release profile than the high polymer concentration (40%w/v). All groups showed a trace of surface erosion after being submerged in PBS for 14 days. Most of the extracts can inhibit Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA). The extracts not only caused no cytotoxicity to Saos-2 bone cells but also can increase cell growth. This study demonstrates that it is possible to use these antibiotic-coated/ antibiotic-loaded scaffolds in the clinic as an antibiotic bead replacement.
RESUMEN
We investigated the effects of both intrinsic defects and hydrogen atom impurities on the magnetic properties of MgO samples. MgO in its pure defect-free state is known to be a nonmagnetic semiconductor. We employed density-functional theory and the Heyd-Scuseria-Ernzerhof (HSE) density functional. The calculated formation energy and total magnetic moment indicated that uncharged [Formula: see text] and singly charged [Formula: see text] magnesium vacancies are more stable than oxygen vacancies (VO) under O-rich growth conditions and introduce a magnetic moment to MgO. The calculated density of states (DOS) results demonstrated that magnetic moments of VMg result from spin polarization of an unpaired electron of the partially occupied valence band, which is dominated by O 2p orbitals. Based on our calculations, VMg is the origin of magnetism and ferromagnetism in MgO. In contrast, the magnetic moment of the magnetic VMg-MgO crystal is suppressed by hydrogen (H) atoms, and unpaired electrons are donated to the unpaired electronic states of VMg when the defect complex Hi-VMg is formed. This suggests that H causes a reduction in magnetization of the ferromagnetic MgO. We then performed experimental studies to verify the DFT predictions by subjecting the MgO sample to a thermal treatment that creates Mg vacancies in the structure and intentionally doping the MgO sample with hydrogen atoms. We found good agreement between the DFT results and the experimental data. Our findings suggest that the ferromagnetism and diamagnetism of MgO can be controlled by heat treatment and hydrogen doping, which may find applications in magnetic sensing and switching under different environmental conditions.
RESUMEN
The aim of this study is to synthesize Titania nanotubes (TNTs) on the 3D-printed Ti-6Al-4V surface and investigate the loading of antibacterial vancomycin drug dose of 200 ppm for local drug treatment application for 24 h. The antibacterial drug release from synthesized nanotubes evaluated via the chemical surface measurement and the linear fitting of Korsmeyer-Peppas model was also assessed. The TNTs were synthesized on the Ti-6Al-4V surface through the anodization process at different anodization time. The TNTs morphology was characterized using field emission scanning electron microscope (FESEM). The wettability and the chemical composition of the Ti-6Al-4V surface and the TNTs were assessed using the contact angle meter, Fourier transform infrared spectrophotometer (FTIR) and the X-ray photoelectron spectroscopy (XPS). The vancomycin of 200 ppm release behavior under controlled atmosphere was measured by the high-performance liquid chromatography (HPLC) and hence, the position for retention time at 2.5 min was ascertained. The FESEM analysis confirmed the formation of nanostructured TNTs with vertically oriented, closely packed, smooth and unperforated walls. The maximum cumulative vancomycin release of 34.7% (69.5 ppm) was recorded at 24 h. The wetting angle of both Ti-6Al-4V implant and the TNTs were found below 90 degrees. This confirmed their excellent wettability.