S. Ramya

Corrosion protection performance of porous strontium hydroxyapatite coating on polypyrrole coated 316L stainless steel.

Polypyrrole/strontium hydroxyapatite bilayer coatings were achieved on 316L stainless steel (316L SS) by the electropolymerisation of pyrrole from sodium salicylate solution followed by the electrodeposition of porous strontium hydroxyapatite. The formation and the morphology of the bilayer coatings were characterised by Fourier transform infrared spectroscopy (FT-IR) and high resolution scanning electron microscopy (HRSEM), respectively. The corrosion resistance of the coated 316L SS specimens was investigated in Ringers solution by electrochemical techniques and the results were substantiated with inductively coupled plasma atomic emission spectrometry (ICP-AES). The passive film underneath the polypyrrole layer is effective in protecting 316L SS against corrosion in Ringers solution. Moreover, we believe that the top porous strontium hydroxyapatite layer can provide potential bioactivity to the 316L SS.

Development of strontium and magnesium substituted porous hydroxyapatite/poly(3,4-ethylenedioxythiophene) coating on surgical grade stainless steel and its bioactivity on osteoblast cells

The present study deals with the successful development of bilayer coatings by electropolymerisation of poly(3,4-ethylenedioxythiophene) (PEDOT) on surgical grade stainless steel (316L SS) followed by the electrodeposition of strontium (Sr) and magnesium (Mg) substituted porous hydroxyapatite (Sr, Mg-HA). The bilayer coatings were characterised by Fourier transform infrared spectroscopy (FT-IR) and high resolution scanning electron microscopy (HRSEM). Corrosion resistance of the obtained coatings was investigated in Ringers solution by electrochemical techniques and the results were in good agreement with those obtained from chemical analysis, namely inductively coupled plasma atomic emission spectrometry (ICP-AES). Also, the mechanical and biological properties of the bilayer coatings were analyzed. From the obtained results it was evident that the PEDOT/Sr, Mg-HA bilayer exhibited greater adhesion strength than the Sr, Mg-HA coated 316L SS. In vitro cell adhesion test of the Sr, Mg-HA coating on PEDOT coated specimen is found to be more bioactive compared to that of the single substituted hydroxyapatite (Sr or Mg-HA) on the PEDOT coated 316L SS. Thus, the PEDOT/Sr, Mg-HA bilayer coated 316L SS can serve as a prospective implant material for biomedical applications.

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 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.