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.

Development of Zn-2Cu-xMn/Mg Alloys for Orthopedic Applications: Mechanical Performance to In Vitro Degradation under Different Physiological Environments

Zinc (Zn) and its alloys are considered futuristic biodegradable materials for their acceptable mechanical properties, suitable corrosion rate, and good biocompatibility. In this study, we report newly developed biodegradable Zn-2Cu-xMn/Mg (x = 0, 0.1, and 0.5) alloys, aiming to achieve good mechanical strength with excellent elongation, desirable wear resistance, and suitable corrosion rate. The effect of Mn/Mg addition on the structural, mechanical, wear, and degradation behaviors of the Zn-2Cu-xMn/Mg alloys was thoroughly investigated. Degradation and tribological behaviors of the alloys were explored in the presence of simulated body fluid (SBF), Dulbecco's modified Eagle medium (DMEM), and DMEM with a 10% fetal bovine serum (FBS) solution. Alloy elements and hot rolling improve their mechanical properties significantly due to precipitation hardening, grain refinement, and solid solution strengthening owing to the formation of MnZn13 and Mg2Zn11 phases. Among all the alloys, the Zn-2Cu-0.5Mn alloy achieved the highest ultimate tensile strength (UTS) of ∼405 MPa and yield strength (YS) of ∼293 MPa with an excellent elongation of ∼51%. The corrosion behavior of the alloys as determined by a potentiodynamic polarization study under different solutions follows the sequence Zn-2Cu < Zn-2Cu-0.5Mn < Zn-2Cu-0.1Mn < Zn-2Cu-0.1Mg < Zn-2Cu-0.5Mg. The corrosion rate by immersion testing for 30 and 90 days also follows the same sequence. The corrosion rate in different solutions follows the order SBF > DMEM + 10%FBS > DMEM. The addition of Mn/Mg also improves the wear resistance and slows the wear rate under wet conditions. The bending test results also indicate the highest bending strength of ∼375 MPa for the Zn-2Cu-0.5Mn alloy, among all the alloys. The bending and tensile strengths deteriorate continuously after the immersion for 30 and 90 days in the solution of SBF, DMEM, and DMEM + 10%FBS. Therefore, the Zn-2Cu-xMn/Mg (x = 0.1 and 0.5) alloys can be considered potential biodegradable implant materials.

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.

Correlating the efficacy of knee viscosupplementation with osteoarthritic changes on roentgenological examination

This study was designed to identify the roentgenological changes of the knee that correlated with an unfavourable outcome when treated with an intra-articular knee viscoelastic supplementation. A prospective cohort of 60 patients receiving a standard course of intra-articular knee viscoelastic supplementation with a commercial uncross-linked hyaluronic acid derivative of an intermediate molecular weight were studied. Follow up was for 12 weeks post-treatment with clinical improvement measured using the Western Ontario and McMasters Universities Osteoarthritis Index. X-Rays of the relevant knee were viewed and graded for the severity of joint space, osteophyte, tibial spine, sclerosis, cyst formation, alignment and general severity by an observer blinded to the outcome of the treatment. There were no appreciable differences noted in the age, sex, length of follow up, pre-treatment, the severity of symptoms before treatment and number of intra-articular injections given per course in each X-ray category identified. There was a significant amount of improvement in patients with a minor loss of medial and lateral joint space in all outcome measures. Minimal changes in tibial spine and global appearance also indicated a positive outcome in stiffness, pain and overall improvement. Thus, patients with moderate to severe osteoarthritic changes in joint space on roentgenological examination would not significantly benefit from intra-articular knee viscoelastic supplementation. In addition, we feel that changes in the tibial spine and global appearance are not reviewed consistently enough to be included as part of our recommendation. As such, we conclude that only patients with a minimal to mild loss in joint space on roentgenological examination should form part of the target group who are likely to benefit from intra-articular knee viscoelastic supplementation.

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.

Interaction-induced enhancement in the activity and selectivity of a titania-supported ammonium salt of a 12-molybdophosphoric acid catalyst during ammoxidation of 2-methylpyrazine

A titania-supported ammonium salt of 12-molybdophosphoric acid has been synthesized, and the salt-support interaction, which enhanced the reaction rate, has been correlated with the activity of the catalyst in the ammoxidation of 2-methylpyrazine.

Staged bilateral total knee replacement--a safer approach in older patients

Simultaneous bilateral total knee replacement has been advocated for bilateral symptomatic arthritis of the knee. The alternative is staged bilateral total knee replacement. We retrospectively reviewed all the total knee replacements performed in our hospital between January 1996 and July 1999. A total of 455 patients had 533 total knee replacements: 54 patients had simultaneous bilateral total knee replacement, 34 patients had staged bilateral total knee replacement and 367 patients had unilateral total knee replacements. Four patients who had simultaneous bilateral total knee replacement died in the immediate post-operative period. During the same period, no deaths were observed in the other two groups. Risk factors were assessed and in our series, age was the only factor found to be associated with mortality following simultaneous bilateral total knee replacement. A staged operation appears to be safer than simultaneous bilateral total knee replacement for patients who are 75 years or older.

Occurrence of vesicular - arbuscular mycorrhizae in kaempferia galangal linn

The presence of vesicular - arbuscular mycorrhizae in the roots of Kaempferia galangal is reported in the article.