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

[This retracts the article DOI: 10.1039/C5RA05624A.].

Retraction: 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.

[This retracts the article DOI: 10.1039/C5RA03432A.].

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

[This retracts the article DOI: 10.1039/C4RA04484C.].

Retraction: 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.

[This retracts the article DOI: 10.1039/C4RA12207K.].

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

[This retracts the article DOI: 10.1039/C5RA04382D.].

Retraction: 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.

[This retracts the article DOI: 10.1039/C5RA17747B.].

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

Retraction of 'Electrodeposition of a porous strontium-substituted hydroxyapatite/zinc oxide duplex layer on AZ91 magnesium alloy for orthopedic applications' by D. Gopi et al., J. Mater. Chem. B, 2014, 2, 5531-5540, https://doi.org/10.1039/C4TB00960F.

Energy transport mechanism in the form of proton soliton in a one-dimensional hydrogen-bonded polypeptide chain.

The dynamics of protons in a one-dimensional hydrogen-bonded (HB) polypeptide chain (PC) is investigated theoretically. A new Hamiltonian is formulated with the inclusion of higher-order molecular interactions between peptide groups (PGs). The wave function of the excitation state of a single particle is replaced by a new wave function of a two-quanta quasi-coherent state. The dynamics is governed by a higher-order nonlinear Schrödinger equation and the energy transport is performed by the proton soliton. A nonlinear multiple-scale perturbation analysis has been performed and the evolution of soliton parameters such as velocity and amplitude is explored numerically. The proton soliton is thermally stable and very robust against these perturbations. The energy transport by the proton soliton is more appropriate to understand the mechanism of energy transfer in biological processes such as muscle contraction, DNA replication, and neuro-electric pulse transfer on biomembranes.

Conserved lamin A protein expression in differentiated cells in the earthworm Eudrilus eugeniae.

Lamin A is an intermediate filament protein found in most of the differentiated vertebrate cells but absent in stem cells. It shapes the skeletal frame structure beneath the inner nuclear membrane of the cell nucleus. As there are few studies of the expression of lamin A in invertebrates, in the present work, we have analyzed the sequence, immunochemical conservation and expression pattern of lamin A protein in the earthworm Eudrilus eugeniae, a model organism for tissue regeneration. The expression of lamin A has been confirmed in E. eugeniae by immunoblot. Its localization in the nuclear membrane has been observed by immunohistochemistry using two different rabbit anti-sera raised against human lamin A peptides, which are located at the C-terminus of the lamin A protein. These two antibodies detected 70 kDa lamin A protein in mice and a single 65 kDa protein in the earthworm. The Oct-4 positive undifferentiated blastemal tissues of regenerating earthworm do not express lamin A, while the Oct-4 negative differentiated cells express lamin A. This pattern was also confirmed in the earthworm prostate gland. The present study is the first evidence for the immunochemical identification of lamin A and Oct-4 in the earthworm. Along with the partial sequence obtained from the earthworm genome, the present results suggest that lamin A protein and its expression pattern is conserved from the earthworm to humans.

Opuntia ficus indica peel derived pectin mediated hydroxyapatite nanoparticles: synthesis, spectral characterization, biological and antimicrobial activities.

In the present study, we have adapted a facile and efficient green route for the synthesis of HAP nanoparticles using pectin as a template which was extracted from the peel of prickly pear (Opuntia ficus indica) fruits. The concentration of pectin plays a major role in the behavior of crystallinity, purity, morphology as well as biological property of the as-synthesized HAP nanoparticles. The extracted pectin and the as-synthesized nanoparticles were characterized by various analytical techniques. The in vitro apatite formation on the surface of the as-synthesized nanoparticles in simulated body fluid (SBF) for various days showed an enhanced bioactivity. Also, the antimicrobial activity was investigated using various microorganisms. All the results revealed the formation of pure, low crystalline and discrete granular like HAP nanoparticles of size around 25 nm with enhanced biological and antimicrobial activities. Hence the as-synthesized nanoparticles can act as a better bone regenerating material in the field of biomedicine.

Synthesis and spectral characterization of silver/magnesium co-substituted hydroxyapatite for biomedical applications.

The present work is aimed at the synthesis of antibacterial and bioactive silver/magnesium co-substituted hydroxyapatite (Ag/Mg-HAP) powders. For this purpose, firstly, different concentrations (0.5, 1.5, 2.5wt.%) of silver substituted HAP (Ag-HAP) powders were prepared by ultrasonic irradiation technique and were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Secondly, magnesium (Mg) is co-substituted as secondary material into Ag-HAP to offset the potential cytotoxicity of Ag, as higher concentration of Ag is toxic. The antibacterial activity of as-synthesized powders was evaluated by Escherichia coli (E. coli) and was found to be effectively high against bacterial colonization. Also, the in vitro cell-material interaction is evaluated with human osteosarcoma MG63 (HOS MG63) cells for cell proliferation. The results showed the evidence of cytotoxic effects of the higher concentration of Ag-HAP characterized by poor cellular viability whereas, Ag/Mg-HAP showed better cell viability indicating that co-substitution of Mg in Ag-HAP effectively offset the negative effects of Ag and improve performance compared with pure HAP. Thus, the as synthesized Ag/Mg-HAP will serve as a better candidate for biomedical applications with good antibacterial property and bone bonding ability.

Novel banana peel pectin mediated green route for the synthesis of hydroxyapatite nanoparticles and their spectral characterization.

Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] is the main inorganic component of natural bone and is widely used in various biomedical applications. In this paper, we have reported the synthesis of HAP nanoparticles by banana peel pectin mediated green template method. The pectin extracted from the peels of banana and its various concentrations were exploited in our study to achieve a controlled crystallinity, particle size as well as uniform morphology of HAP. The extracted pectin was characterized by spectral techniques like Fourier transform infrared spectroscopy (FTIR) for the functional group analysis, proton-1 nuclear magnetic resonance spectroscopy ((1)H NMR) and carbon-13 nuclear magnetic resonance spectroscopy ((13)C NMR) for the identification of H and C atoms in the extracted pectin, respectively. The HAP nanoparticles were synthesized using different concentrations of the as-extracted pectin. The purity, crystallinity and morphology of the as-synthesized HAP nanoparticles were evaluated by FTIR, X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX) and transmission electron microscopy (TEM), respectively. Moreover the antibacterial activity of HAP nanoparticles was evaluated against the gram positive and negative bacteria like Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), respectively. The experimental results revealed that the HAP nanoparticles synthesized in the presence of an optimized concentration of pectin are pure, low crystalline, spherical and discrete particles with reduced size. Also, the HAP sample derived in the presence of pectin showed an enhanced antibacterial activity than that of the HAP synthesized in the absence of pectin. Hence, the HAP nanoparticles synthesized using pectin as a green template can act as a good biomaterial for biomedical applications.

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 Ringer's 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.

Nano breathers and molecular dynamics simulations in hydrogen-bonded chains.

Non-linear localization phenomena in biological lattices have attracted a steadily growing interest and their existence has been predicted in a wide range of physical settings. We investigate the non-linear proton dynamics of a hydrogen-bonded chain in a semi-classical limit using the coherent state method combined with a Holstein-Primakoff bosonic representation. We demonstrate that even a weak inherent discreteness in the hydrogen-bonded (HB) chain may drastically modify the dynamics of the non-linear system, leading to instabilities that have no analog in the continuum limit. We suggest a possible localization mechanism of polarization oscillations of protons in a hydrogen-bonded chain through modulational instability analysis. This mechanism arises due to the neighboring proton-proton interaction and coherent tunneling of protons along hydrogen bonds and/or around heavy atoms. We present a detailed analysis of modulational instability, and highlight the role of the interaction strength of neighboring protons in the process of bioenergy localization. We perform molecular dynamics simulations and demonstrate the existence of nanoscale discrete breather (DB) modes in the hydrogen-bonded chain. These highly localized and long-lived non-linear breather modes may play a functional role in targeted energy transfer in biological systems.

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 Ringer's 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 Ringer's solution. Moreover, we believe that the top porous strontium hydroxyapatite layer can provide potential bioactivity to the 316L SS.

A novel green template assisted synthesis of hydroxyapatite nanorods and their spectral characterization.

Hydroxyapatite [HAP, Ca10(PO4)6(OH)2] is the main inorganic component of bone material and is widely used in various biomedical applications due to its excellent bioactivity and biocompatibility. In this paper we have reported the synthesis of hydroxyapatite nanorods by green template method using the extracts of three different natural sources which contain tartaric acid and also from commercially available one. The extracts of banana, grape and tamarind are taken as the sources of tartaric acid. The as-synthesized samples were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Also the antibacterial activity of HAP with different concentrations against two pathogen bacteria strains Escherichia coli (E. coli) and Klebsiella (Gram-negative bacteria) were tested. The results show that the particles of all the samples are of nanosized and pure. The crystallinity decreases as changing the sources of tartaric acid from commercial to natural one and also changing the natural sources from banana to tamarind extracts. The formation of nanorods are found in all the samples but the nanorods with uniform size distribution can be obtained only by using the tamarind extract as the source of tartaric acid. Moreover, the as-synthesised HAP nanorods derived from natural sources exhibited a strong antibacterial activity against both E. coli and Klebsiella at a concentration of 100 µl. The HAP nanorods synthesized by this method can act as a potential candidate for various biomedical applications.

Synthesis and spectroscopic investigations of hydroxyapatite using a green chelating agent as template.

Hydroxyapatite [Ca(10)(PO(4))(6)(OH)(2), HAP] particles have been successfully synthesized by a cost-effective, eco-friendly green template method using natural and commercially available sucrose as a chelating agent. The sucrose used in this method has been extracted from various sources, three from natural and one from commercially available sources are exploited in our study to achieve a controlled crystallinity, particle size as well as uniform morphology. Spectral characterizations involving Fourier transform infrared spectroscopy (FT-IR) for the functional group analysis of sucrose and HAP; carbon-13 nuclear magnetic resonance spectroscopy ((13)C NMR) for the identification of the carbon atoms in sucrose and in HAP; liquid chromatography/mass spectrometry (LC-MS) for the determination of the hydrolyzed products of sucrose; and X-ray diffraction (XRD) techniques for the phase identification of the HAP particles were performed. The morphology of the HAP particles were assessed thoroughly using a scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX). The experimental results indicate that the obtained HAP using the natural sucrose as a chelating agent is of phase pure, with a well defined morphology having discrete particles without any agglomeration than the HAP from commercially available sucrose. Further, the reduced particle size can be achieved from the stem sugarcane extract as the source of the chelating agent.

Synthesis of hydroxyapatite nanoparticles by a novel ultrasonic assisted with mixed hollow sphere template method.

Hydroxyapatite (HAP) is the main inorganic component of bone material and is widely used in various biomedical applications due to its excellent bioactivity and biocompatibility. In this paper, we have reported the synthesis of hydroxyapatite nanoparticles by a novel ultrasonic assisted mixed template directed method. In this method glycine-acrylic acid (GLY-AA) hollow spheres were used as an organic template which could be prepared by mixing of glycine with acrylic acid. The as-synthesized HAP nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and tunnelling electron microscope (TEM) to investigate the nature of bonding, crystallinity, size and shape. The thermal stability of as-synthesized nanoparticles was also investigated by the thermo gravimetric analysis (TGA). The effect of ultrasonic irradiation time on the crystallinity and size of the HAP nanoparticles in presence of glycine-acrylic acid hollow spheres template were investigated. From the inspection of the above results it is confirmed that the crystallinity and size of the HAP nanoparticles decrease with increasing ultrasonic irradiation time. Hence the proposed synthesis strategy provides a facile pathway to obtain nano sized HAP with high quality, suitable size and morphology.

Spectroscopic investigation on formation and growth of mineralized nanohydroxyapatite for bone tissue engineering applications.

Synthetic calcium hydroxyapatite (HAP,Ca(10)(PO(4))(6)(OH)(2)) is a well-known bioceramic material used in orthopaedic and dental applications because of its excellent biocompatibility and bone-bonding ability. Substitution of trace elements, such as Sr, Mg and Zn ions into the structure of calcium phosphates is the subject of widespread investigation. In this paper, we have reported the synthesis of Sr, Mg and Zn co-substituted nanohydroxyapatite by soft solution freezing method. The effect of pH on the morphology of bioceramic nanomaterial was also discussed. The in vitro bioactivity of the as-synthesized bioceramic nanomaterial was determined by soaking it in SBF for various days. The as-synthesized bioceramic nanomaterial was characterized by Fourier transform infrared spectroscopy, X- ray diffraction analysis, Scanning electron microscopy and Energy dispersive X-ray analysis and Transmission electron microscopic techniques respectively. The results obtained in our study have revealed that pH 10 was identified to induce the formation of mineralized nanohydroxyapatite. It is observed that the synthesis of bioceramic nanomaterial not only support the growth of apatite layer on its surface but also accelerate the growth which is evident from the in vitro studies. Therefore, mineralized nanohydroxyapatite is a potential candidate in bone tissue engineering.