L. Kavitha

Electrodeposition of a porous strontium-substituted hydroxyapatite/zinc oxide duplex layer on AZ91 magnesium alloy for orthopedic applications

Magnesium alloy is a potential biomedical implant because of its outstanding biodegradability and mechanical properties. But the poor corrosion resistance of AZ91 magnesium alloy in physiological solution limits its biomedical applications. In order to improve the corrosion resistance and biological performance of AZ91 magnesium alloy, we have fabricated a strontium-substituted porous hydroxyapatite (Sr-HAP)/zinc oxide (ZnO) duplex layer on AZ91 magnesium alloy by electrodeposition. The porous Sr-HAP/ZnO duplex-layer coating on AZ91 magnesium alloy was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy and energy dispersive X-ray analysis. Also, the mechanical properties of the duplex-layer coating were evaluated using adhesion and Vickers micro-hardness tests. The effects of the duplex-layer coating on the corrosion behavior of AZ91 magnesium alloy were also investigated in simulated body fluid using electrochemical studies. The potentiodynamic polarization and electrochemical impedance spectroscopy results indicated that the corrosion resistance of AZ91 magnesium alloy was significantly improved by the duplex-layer coating. The in vitro cell-material interaction of the duplex-layer coating was observed with human osteosarcoma MG63 cells for cell viability at 1, 4 and 7 days of incubation and the coating exhibited good biocompatibility. Hence, from the obtained results we believe that the duplex-layer made of ZnO together with porous Sr-HAP on AZ91 magnesium alloy could provide effective corrosion protection and enhanced bioactivity. Thus, duplex-layer-coated AZ91 magnesium alloy can serve as a promising candidate for orthopedic applications.

Investigation on corrosion protection and mechanical performance of minerals substituted hydroxyapatite coating on HELCDEB-treated titanium using pulsed electrodeposition method

The present work aims to investigate the effects of minerals (strontium, magnesium and zinc) substituted hydroxyapatite (M-HAP) coating on high-energy low-current DC electron beam (HELCDEB)-treated titanium (Ti). The M-HAP coating was developed over the untreated and HELCDEB-treated Ti by pulsed electrodeposition, and was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and electrochemical techniques. The M-HAP coating was obtained on Ti treated at 500 and 700 keV HELCDEB. The coating on the 700 keV HELCDEB-treated Ti showed better corrosion resistance properties than the coating obtained on the 500 keV HELCDEB-treated and untreated Ti. The M-HAP coating on the HELCDEB-treated Ti showed typical flower-like morphology, and exhibited better resistance to corrosion in simulated body fluid (SBF), along with increased microhardness and decreased contact angle. An in vitro study of the coating was conducted by immersion in the SBF solution for 1–7 days. The results clearly showed that the M-HAP coating on 700 keV HELCDEB-treated Ti enhanced its corrosion resistivity and mechanical properties. The coating may have many applications in orthopedics because it could improve implant fixation in human bone.

Investigation of anticorrosive, antibacterial and in vitro biological properties of a sulphonated poly(etheretherketone)/strontium, cerium co-substituted hydroxyapatite composite coating developed on surface treated surgical grade stainless steel for orthopedic applications

In the present investigation, a sulphonated poly(etheretherketone)/strontium, cerium co-substituted hydroxyapatite (S-PEEK/Sr,Ce-HAp) composite coating is obtained on high energy low current DC electron beam (HELCDEB) treated 316L stainless steel (316L SS) by electrodeposition. The surface of the 316L SS was treated using HELCDEB with an energy of 500 keV and a beam current of 1.5 mA. The as-formed coatings on HELCDEB treated 316L SS were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and high resolution scanning electron microscopy (HRSEM). Electrochemical results show that the S-PEEK/Sr,Ce-HAp coating with an optimum 2 wt% S-PEEK concentration on HELCDEB treated 316L SS possesses maximum corrosion resistance in Ringer’s solution. The antibacterial activity and in vitro bioactivity of the composite coatings were investigated. The results revealed that the HELCDEB treatment of the 316L SS improved anticorrosion performance and also that the combination of S-PEEK and Sr,Ce-HAp in the coating greatly improved the bioactivity and biocompatibility of the as-developed composite coating on HELCDEB treated 316L SS.

Ball flower like manganese, strontium substituted hydroxyapatite/cerium oxide dual coatings on the AZ91 Mg alloy with improved bioactive and corrosion resistance properties for implant applications

Bio-degradable metals and alloys have been suggested as revolutionary potential materials for bone-related treatment. Of these materials, the AZ91 magnesium alloy (AZ91 Mg alloy) emerges as an attractive candidate due to its non-toxicity and outstanding mechanical properties. Even though magnesium alloys are widely studied as orthopedic implants for bone replacement and bone regeneration, their undesirable rapid corrosion rate under physiological conditions has limited their actual clinical applications. Therefore, increasing the corrosion resistance of the AZ91 Mg alloy is one of the key issues to address for the development of bio-degradable implants. In this study, a cerium oxide (CeO2) coating is developed on the AZ91 Mg alloy by electrodeposition with a view of minimizing its corrosion rate during the bone healing period. Further, to improve the clinical application of AZ91 Mg alloy, manganese (Mn) and strontium (Sr) substituted hydroxyapatite (Mn, Sr-HAP) coatings were developed on the CeO2 coated AZ91 Mg alloy. Hence, this study reports on the development of a Mn, Sr-HAP/CeO2 dual coating on the AZ91 Mg alloy to make it a suitable alternative material for orthopedic implants.

Single walled carbon nanotubes reinforced mineralized hydroxyapatite composite coatings on titanium for improved biocompatible implant applications

A surface coating strategy encompassing the use of bioactive trace elements and reinforcing material will have a significant influence on the mechanical and osseointegration properties of bioceramic coated implants. Here, we developed mineral substituted hydroxyapatite (M-HAP) and carbon nanotube reinforced mineralized hydroxyapatite (CNT/M-HAP) composite coating on titanium (Ti) by pulsed electrodeposition which is a promising approach to produce bioimplants with better osseointegration capacity and improved mechanical properties. The role of CNT and minerals like strontium, magnesium and zinc, in enhancing the mechanical and biological properties of the HAP coating was investigated using various techniques. The structural and morphological analyses were carried out using Fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray analysis and elemental mapping. The mechanical characterization results revealed enhanced adhesion strength for the composite coating. Also, an improved viability of osteoblast cells was observed in vitro on the CNT/M-HAP composite coating. The ability of the composite coated Ti implant to induce bone formation was evaluated in vivo in Wistar rats. Thus, the as-developed composite coated Ti that combines the good osteoconductivity of M-HAP together with the mechanical strength of CNT can be used as a potential implant material for orthopedic applications.

Fabrication of divalent ion substituted hydroxyapatite/gelatin nanocomposite coating on electron beam treated titanium: mechanical, anticorrosive, antibacterial and bioactive evaluations

The key property in the fabrication of a biomaterial is to facilitate the replacement and/or regeneration of damaged tissues and organs. To obtain such a biomaterial, we fabricated a triple mineral (strontium, magnesium and zinc) substituted hydroxyapatite/gelatin (M-HAP/Gel) nanocomposite coating on electron beam treated titanium (Ti) metal. The influence of gelatin concentration in M-HAP was studied to investigate its effect on morphological changes, crystallinity, mechanical and anticorrosion properties. The M-HAP/Gel nanocomposite coating (with 3 wt% gelatin) on treated Ti resulted in better mechanical and anticorrosion properties as a consequence of the electron beam treatment of Ti. A reduced number of bacterial colonies were observed for the M-HAP/Gel composite against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) microbes which evidences a lower chance of implant failure after implantation. Moreover, the cell proliferation assay, live/dead staining of MT3C3-E1 cells and cell viability of fibroblast stem cells on the resultant nanocomposite revealed that the M-HAP/Gel composite will definitely be an effective implant material for better cell growth in orthopedic applications.

Smart rose flower like bioceramic/metal oxide dual layer coating with enhanced anti-bacterial, anti-cancer, anti-corrosive and biocompatible properties for improved orthopedic applications

Metallic implants suffer from numerous problems such as stress shielding, poor prolonged osseointegration and corrosion under in vivo environments. Such problems are often faced by bone cancer patients as they receive orthopedic implants after cancerous bone resection. Unfortunately, there are no orthopedic materials developed so far that simultaneously increase healthy bone growth as takes place in traditional orthopedic implant applications, while inhibiting cancerous bone growth. Based on these issues, the long-term objective of this study was to introduce a new implant material in an integrated way. Hence we have fabricated a selenium (Se), and manganese (Mn) substituted flower like hydroxyapatite (HAP) coating on zirconium oxide (ZrO2) coated AZ91 magnesium alloy. The flower like Se,Mn-HAP/ZrO2 dual layer coating on the AZ91 magnesium alloy was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM) and energy dispersive X-ray (EDX) analysis. Also, the mechanical properties of the dual layer coating were evaluated using adhesion and Vickers micro-hardness tests. The effect of the dual layer coating on the corrosion behavior of the AZ91 magnesium alloy was also investigated in simulated body fluid (SBF) using electrochemical studies. The cell–material interaction of the dual layer coating was observed in vitro with human osteosarcoma MG63 cells for cell proliferation at 1, 4 and 7 days of incubation and in vivo in Wistar rats for 14 and 28 days of implantation. From the results it was found that the dual layer coated AZ91 Mg alloy has an optimal structure and morphology, as indicated by SEM, showing a desired surface for the osteoblast adhesion, viability and proliferation. The new ceramic coating has induced an increased adhesion strength and microhardness, improved corrosion resistance, enhanced osteoblast proliferation and inhibited the growth of cancerous cells. Therefore, based on these results, we propose a new dual layer coated AZ91 Mg alloy which satisfies the requirements in bone cancer treatment and signifies progress in the field of implant materials.