Feasibility Insights of the Green-Assisted Calcium-Phosphate Coating on Biodegradable Zinc Alloys for Biomedical Application: In Vitro and In Vivo Studies.

In the field of bone tissue engineering, recently developed Zn alloy scaffolds are considered potential candidates for biodegradable implants for bone regeneration and defect reconstruction. However, the clinical success of these alloys is limited due to their insufficient surface bioactivities. Further, the higher concentration of Zn2+ produced during degradation promotes antibacterial activity, but deteriorates osteogenic properties. This study fabricated an Azadirachta indica (neem)-assisted brushite-hydroxyapatite (HAp) coating on the recently developed Zn-2Cu-0.5Mg alloy to tackle the above dilemma. The microstructure, degradation behavior, antibacterial activity, and hemocompatibility, along with in vitro and in vivo cytocompatibility of the coated alloys, are systematically investigated. Microstructural analysis reveals flower-like morphology with uniformly grown flakes for neem-assisted deposition. The neem-assisted deposition significantly improves the adhesion strength from 12.7 to 18.8 MPa, enhancing the mechanical integrity. The potentiodynamic polarization study shows that the neem-assisted deposition decreases the degradation rate, with the lowest degradation rate of 0.027 mm/yr for the ZHN2 sample. In addition, the biomineralization process shows the apatite formation on the deposited coating after 21 days of immersion. In vitro cytotoxicity assay exhibits the maximum cell viability of 117% for neem-assisted coated alloy in 30% extract after 5d and the improved cytocompatibility which is due to the controlled release of Zn2+ ions. Meanwhile, neem-assisted coated alloy increases the ZOI by 32 and 24% for Gram-positive and Gram-negative bacteria, respectively. Acceptable hemolysis (<5%) and anticoagulation parameters demonstrate a promising hemocompatibility of the coated alloy. In vivo implantation illustrates a slight inflammatory response and vascularization after 2 weeks of subcutaneous implantation, and neo-bone formation in the defect areas of the rat femur. Micro-CT and histology studies demonstrate better osseointegration with satisfactory biosafety response for the neem-assisted coated alloy as compared to that without neem-assisted deposition. Hence, this neem-assisted brushite-Hap coating strategy elucidates a new perspective on the surface modification of biodegradable implants for the treatment of bone defects.

Influence of Copper on the Microstructural, Mechanical, and Biological Properties of Commercially Pure Zn-Based Alloys for a Potential Biodegradable Implant.

Three Zn-based alloys (Zn1Cu, Zn2Cu, and Zn3Cu) were developed by the addition of Cu (1, 2, and 3 wt %) into commercially pure Zn. This report systematically investigates the potential for these newly developed Zn-based alloys as biodegradable materials. Microstructural studies reveal the presence of spherical-shaped nanosized precipitates of ε-CuZn4 in the Zn1Cu alloy, whereas Zn2Cu and Zn3Cu alloys exhibit the presence of both micron- and nanosized precipitates of ε-CuZn4. The mechanical properties such as hardness, tensile and compressive strengths improve significantly with an increase in the amount of Cu in the alloy. The Zn3Cu alloy exhibits the highest yield strength (225 ± 9 MPa) and ultimate tensile strength (330 ± 12 MPa) among all of the alloys, which are ∼2.7 and 2 times higher than those of pure Zn. In vitro degradation behavior is evaluated by the potentiodynamic polarization study and immersion testing in Hank's solution for 20 and 75 days. The corrosion rate after both polarization and immersion testing follows the order of pure Zn < Zn1Cu < Zn3Cu < Zn2Cu. An electrochemical impedance spectroscopy (EIS) study also concludes that Zn2Cu shows the lowest corrosion resistance. The % cell viability values of 3T3 fibroblasts cells after 5 days of culture in a 50% diluted extract of pure Zn, Zn2Cu, and Zn3Cu alloys are 76 ± 0.024, 86.18 ± 0.033, and 92.9 ± 0.026%, respectively, establishing the improved cytocompatibility of the alloys as compared to pure Zn. Furthermore, an antibacterial study also reveals that the Zn3Cu alloy exhibits 80, 67, and 100% increases in the zone of inhibition (ZOI) for Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa bacteria, respectively, as compared to that of pure Zn.

Validated HPLC method for the determination of celecoxib in human serum and its application in a clinical pharmacokinetic study.

A simple high performance liquid chromatographic method using UV detection for the determination of celecoxib, a specific COX 2 inhibitor, in serum was developed. Serum samples containing the internal standard, tolbutamide, are eluted through a C18, Wakosil column. After extracting with dichloromethane, the eluent is monitored at 250 nm. The mobile phase comprised of 10 mM potassium dihydrogen ortho phosphate (pH 3.2) and acetonitrile (50:50 v/v) with a flow rate of 1 ml/min. Retention times of celecoxib and tolbutamide were 9.6 and 3.5 min, respectively. The mean absolute recovery value was about 70-80%, while the intra day and inter day coefficient of variation and percent error values of the assay method were less than 10%. The calibration curve was linear over a concentration range of 10-1000 ng/ml.