Biocompatible drug-delivery materials are important because they provide controlled release of biologically active agents to enhance the effectiveness of medical treatments. Montmorillonite (Mnt) has been utilized in drug-delivery systems for delayed-release application because it can safely encapsulate drug molecules via intercalation reactions. The objective of the present study was to evaluate the delivery characteristics of the drug ciprofloxacin (CIP) from a composite with Mnt (Mnt-CIP) in which the Mnt was first prepared by acid treatment and vibration ball milling. The surfaces of Mnt were modified by reacting the Mnt suspension in 1.0 M HCl acid and by dispersing the powder with a vibration ball mill, then the CIP drug was added at pH 4 and stirred. The goal was to improve the sustained-release performance of the CIP. This Mnt-CIP drug-release system was characterized by X-ray diffraction, X-ray fluorescence analysis, Fourier-transform infrared spectroscopy, surface area measurement using the Brunauer-Emmett-Teller (BET) method, and ultraviolet spectroscopy. The X-ray diffraction results confirmed the intercalation of CIP into the interlayer space of Mnt. The in vitro release properties of the intercalated CIP were investigated using a simulated phosphate-buffered saline solution (pH 7.4) at 36±0.5°C. The CIP drug exhibited a continued release for 3 h. Moreover, Mnt prepared by HCl acid treatment and dispersion in the vibration ball mill delayed the drug dissolution rate. In summary, the Mnt-CIP composite prepared in this study exhibited slow and sustained release characteristics, indicating that Mnt mined from the Gampo-40 mining area in Gyeongju can be used in various drug-delivery applications.
The structure and elastic properties of rocksalt and wurtzite Ti–Al–N ternary solid solutions were investigated using first principles calculations. We also performed an experimental evaluation using the sputtering method to obtain the reliability. The phase transition of (Ti1−xAlx)N solid solutions was occurred at x = 0.5–0.75 for both calculations and experimental results. The bulk modulus of rocksalt and wurtzite solid solutions decreases with increasing Al content. On the other hand, shear moduli and Young's moduli gradually increase with Al content only in rocksalt solid solutions. The theoretical and experimental results indicate that the overall mechanical properties of rocksalt solid solutions are superior to those of wurtzite solid solutions. Therefore, controlling the crystal structure of the Ti–Al–N ternary metastable system was crucial for optimizing the material properties.
The recycling of coated cemented carbide scraps is becoming increasingly significant for the recovery of rare metals. However, coatings consisting of Group IV and V transition metal nitrides are one of the challenging factors in obtaining high-purity materials. We investigated the structural, elastic, and mechanical properties of Group IV and V transition-metal nitrides (TiN, VN, ZrN, NbN, HfN, and TaN) using first-principle calculations. Convergence tests were performed to obtain reliable calculated results. The equilibrium structures of the nitrides were in good agreement with those of a previous study, indicating the reliability of the data. Group IV transition metal nitrides show a higher covalent bonding nature. Thus, they exhibit a higher degree of brittleness than that of Group V transition metal nitrides. In contrast, Group V transition metal nitrides show weaker resistance to shear loading and more ductile behavior than Group IV transition metal nitrides because of the metallic bonds characterized by valence electron concentration. The results of the crystal orbital Hamilton population analysis showed good agreement with the shear resistance tendencies of all transition metal nitrides.
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