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Surface segregation of Ge is seen in the Cu-5at%Ge alloy with an activation enthalpy equal to 17 kJ/mol. Oxidation of the alloy in the temperature range 400 to 600 K shows the formation of Cu2O and GeO which on further heating in vacuum at 650 K converts to GeO2 with the reduction of Cu2O to Cu.

X-ray photoelectron and Auger spectroscopic techniques have been employed to study surface segregation and oxidation of Cu-1 at%Sn, Cu-9at%Pd and Cu-25at%Pd alloys. Both Cu-Pd(9%) and Cu-Pd(25%) alloys show segregation of Cu when heated above 500 K. The Pd concentration was reduced by 50% at 750 K compared to the bulk composition; the enthalpy of segregation of Cu is around - 6kJ/mol. Sn segregation is seen from 470 to 650 K in the Cu-Sn(1%) alloy, and a saturation plateau of Sn concentration above 650 K is observed. Surface oxidation of Cu-Sn(1%) and Cu-Pd(9%) alloys at 500 K showed the formation of Cu2O on the surface with total suppression of Sn or Pd on the respective alloy surfaces. On vacuum annealing the oxidised Cu-Sn alloy surface at 550 K, a displacement reaction 2Cu2O+Sn→4Cu+SnO2 was observed. However, under similar annealing of the oxidised Cu-Pd(9%) alloy surface at 500 K, oxide oxygen was totally desorbed leaving the Cu-Pd alloy surface clean. In the case of the Cu-Pd(25%) alloy, only dissociatively chemisorbed oxygen was seen at 500 K which desorbed at the same temperature. Oxygen spill-over from copper to palladium is suggested as the mechanism of oxygen desorption from the oxidised Cu-Pd alloy surfaces.

Calcium deficient hydroxyapatite (CDHA) nanoparticles with a Ca/P ratio of 1.6 were synthesized by accelerated sonochemical process. The synthesis was carried out using calcium nitrate and diammonium hydrogen phosphate in an ultrasonic bath operated at a fixed frequency of 135 kHz and 250 Watts power. The effect of ultrasonic radiation as a function of time over the formation and structure of nanoparticles were investigated using X-ray diffraction, spectroscopy and microscopy methods. The synthesized nanocrystals showed X-ray powder diffraction pattern corresponding to that of hydroxyapatite stoichiometry with CDHA characteristics. HPO2- 4 Fourier transform infrared vibration band observed at 875 cm-1. Transmission electron microscopic analysis confirmed the nanocrystalline nature and growth of acicular, rod and needle-like CDHA nanocrystals morphology with increasing irradiation time. � 2014 American Scientific Publishers. All rights reserved.

Strontium-substituted apatites have provoked increased interest in recent years for their beneficial effects on osteoporotic bone treatment and replacement. In this study, rod- and acicular-shaped, strontium-substituted calcium deficient hydroxyapatite (CDHA) nanoparticles with (Ca + Sr)/P ratio of 1.61 were synthesized via accelerated microwave processing. The X-ray powder diffraction analysis indicates the synthesized nanoparticles as apatite phase with diffraction patterns similar to those of hydroxyapatite. The hydrodynamic diameter of the particles were observed to be similar to 200-500 nm and found to increase with strontium substitution along with an increase in the negative zeta potential by dynamic light scattering method, suggesting the particles to be agglomerates in water. The morphology of the nanoparticles was studied using transmission electron microscopy (TEM), where, pure CDHA showed globular and strontium substituted CDHAs showed rod and acicular shape for 5% and 10% Sr substitution, respectively. The average size of the particles in TEM was measured to be 33 nm x 5 nm, 40 nm x 6 nm, and 55 nm x 8 nm (L x W) for pure and strontium-substituted CDHAs, respectively. Inductively coupled plasma spectroscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy further confirm the substitution of strontium and deficiency of calcium in the synthesized nanoparticles. Thermal stability and in vitro solubility of CDHA nanoparticles were observed to increase with strontium substitution. The MTT [3-(4, 5-Dimethylthiazole-2-yl)-2, 5-diphenyl tetrazolium bromide] assay indicate that the substituted nanoparticles are non-toxic to human periodontal ligament fibroblast (HPDLF) cells. Cell uptake study by fluorescence microscopy using rhodamine-123 and actin/DAPI stained HPDLF cells show cellular localization of the nCDHA, nSr5CDHA, nSr10CDHA nanoparticles without any adverse effects. The strontium-substituted CDHAs showed significant antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria by colony count method. The 10% Sr substituted CDHA show the maximum microbial reduction of around 56% for E. coli and 35% for S. aureus with 1 x 105 cells/mL of respective bacterial culture. Refereed/Peer-reviewed

Glass ionomer cements (GICs) are clinically attractive filling materials often employed in the field of dentistry as restorative and luting materials. The present work aims to formulate bioactive nanocrystalline calcium deficient hydroxyapatite (nCDHA)-GIC composite cements with improved mechanical and resorption properties of the set cement than GICs. The nCDHA was synthesized via an accelerated microwave process and characterized by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) methods. The synthesized nCDHA was mixed with GIC in different compositions (5, 10 and 15 wt%) maintaining the powder to liquid ratio. Cylinders of dimensions 8 mm height and 4 mm diameter were formed using a Teflon mold following a conventional cement forming technique. The XRD and FT-IR of the cylinders showed increased intensity and characteristic bands of CDHA with increase in nCDHA content. The surface cracks and the elemental composition of the set cements were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Decreased surface hardness was observed for composite cements with increase in nCDHA addition. The cement cylinders were tested for ionic release in Millipore water (pH = 7) via inductive coupled plasma (ICP) spectroscopy and in demineralization solution of pH = 5 to find out the weight loss in an acidic environment at 37 C performed periodically for 5 weeks. The ionic release percentage, weight loss and compressive strength were observed to increase with an increase in nCDHA addition. Refereed/Peer-reviewed

Electrospun nanofibers have attracted much attention in recent years as scaffolds for improved osteo-regeneration. In the present study, polycaprolactone/poly(1,4-butylene adipate-copolycaprolactam) blends were electrospun as potential biodegradable scaffolds for bone tissue engineering. The morphology of the scaffold was observed to be bead-free nanofibers with average diameter of about 400 nm by scanning electron microscopy. The semi crystalline nature, molecular interactions among the polymers, lowering of thermal degradation temperature and improved wetability of the blends compared to polycaprolactone were confirmed by wide angle X-ray diffraction analysis, Fourier transform infrared spectroscopy, simultaneous thermal analysis and contact angle measurements. Enzymatic in vitro degradation study using lipase enzyme showed the electrospun blend fiber mat to be biodegradable with degradation rate higher than that of polycaprolactone. Direct contact in vitro cytotoxicity test and MTT reduction calorimetric assay using mouse fibroblast cells indicated the non-cytotoxic reactivity and cell viability of the scaffold. Human osteoblast cell culture studies of the polymer blend fibers showed improved cellular response with good adhesion and proliferation, demonstrating the viability of the electrospun blend mat for bone tissue engineering applications. � 2011 American Scientific Publishers. All rights reserved.

Eggshell is an attractive natural source of calcium for the synthesis of hydroxyapatite (HA) as it contains minor amounts of biologically relevant elements such as Mg, Sr, and Si. The mineral phase of the human bone is essentially a calcium deficient hydroxyapatite (CDHA) which shows more bioactivities and absorbance than stoichiometric HA does. Hence, we have attempted to develop a protein delivery system based on eggshell derived CDHA (ECDHA) nanoparticles for bone tissue engineering. Nanoparticles with Ca/P molar ratio of 1.67, 1.61 and 1.51 to form CDHAs with compositions covering the properties of stable HA phase (Ca/P. = 1.67) to degradable tricalcium phosphate (TCP) phase (Ca/P. = 1.5) were synthesized by microwave-accelerated wet chemical synthesis using eggshell as well as synthetic calcium hydroxide as calcium precursors. The delivery profiles of bovine serum albumin (BSA), a model protein by the nanocarriers, were studied. Both eggshells derived and synthetic CDHA samples showed maximum amount of loading of 57% and 37%, respectively at a Ca/P ratio of 1.51, comparing to stoichiometric HA. ECDHA also showed a much more BSA release (25%) than synthetically derived CDHA (6.5%) did. To further improve the release profile, alginate coating was carried out on CDHA nanoparticles and the BSA release profiles were evaluated. A maximum release of 65% was observed for alginate coated ECDHA at a Ca/P ratio of 1.51 for a period of 2 days. The ECDHA nanoparticle with a Ca/P ratio similar to degradable TCP and with alginate coating seems to be an ideal protein delivery agent. � 2014 Elsevier B.V.

Cell viability and in vitro osteoblast cell responses to characterized anatase and rutile titania nanofiber scaffold surfaces were investigated. Poly(vinyl acetate) (PVAc)/titanium isopropoxide (TIP) composite microfibers with average fiber diameter of about 3 tan were fabricated via electrospinning. The microfibers were calcined to 500 and 900 degrees C to obtain the anatase and rutile phase titania (TiO2) nanofibers of about 500 nm diameter. The weight loss pattern of PVAc/TIP microfibers was determined by simultaneous thermo-gravimetric analysis (TG-DTA). The morphology of fibers was characterized by scanning electron microscopy (SEM). X-ray diffraction (XRD) and Raman spectroscopic analysis confirm the varied phases of the fibers formed at different calcination temperatures. The obtained nanofibers by well conceived heat treatment showed the fibers to have rough surface that could be shaped by sintering of crystalline titania nanoparticles. MIT reduction calorimetric assay using vero cells; cell adhesion and proliferation study using osteoblast cells indicated a notable difference in cell viability and osteoblast cell response to the sintered fibers with rutile phase showing improved properties for scaffold applications compared to anatase. Thus, the biological evaluation of phase controlled titania nanofibers indicated that rutile phase could serve as a better candidate for tissue engineering applications. Refereed/Peer-reviewed

The biomineralization of pristine chitosan film without any prior surface treatment was evaluated by immersing the film in simulated body fluid (SBF) at 37 degrees C for 3 weeks. The film was prepared by solvent casting method using chitosan of known degree of deacetylation (DD). The formation of the hydroxyapatite (HA) phase on the film surface after immersion was studied periodically by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) methods. The electron micrographs showed the morphology of the deposited apatite as small globules appearing uniformly throughout the films surfaces. The Ca/P ratio of the apatite was found to increase with increase in immersion time and approaching towards the stoichiometric value of the HA phase. The mineralized chitosan film could be of promising support to hard tissue regeneration. Refereed/Peer-reviewed