New core-shell hydroxyapatite/Gum-Acacia nanocomposites for drug delivery and tissue engineering applications.

Core-shell hydroxyapatite (HAP) - gum acacia (GA) nanocomposite, in which the HAP acts as a core while the GA serves as a shell, was synthesized by precipitation techniqueusing Ca(NO3)2.4H2O and NH4H2PO4as precursors for Ca and P, respectively. The crystallite size and morphology of the synthesized core-shell HAP-GA nanocomposite was evaluated by X-ray diffraction measurement and transmission electron microscopy. The crystallite size of GA-HAP nanocomposite is markedly decreased from 89 nm to 63 nm when the concentration of GA in the reaction mixture is increased from 0 to 10%. Transmission electron micrographs confirm encapsulation of GA over the HAP particles, leading to the formation of GA shell-HAP core assembly, which is quite evident for 10% GA-HAP composites. The nature of functional groups present in HAP was identified using FT-IR and Raman spectroscopies while its chemical composition was analyzed by energy dispersive X-ray analysis. The Ca/P ratio of the synthesized HAP's was found to be 1.67. The elemental composition of the HAP samples was evaluated by X-ray photoelectron spectroscopy. The peaks at binding energies 286.5 and 289.3 eV of C 1S and the peaks at 530.6 eV and 532.1 eV of the O 1S spectra further substantiate encapsulation of GA over the HAP particles, resulting in the formation of GA-HAP nanocomposite. Pellet samples of HAP were immersed in simulated body fluid to ascertain their bioactivity using scanning electron micrographs. The drug, naringenin, was loaded within the core of HAP by pellet pressing method. The drug-loaded core-shell HAP composites were subjected to microbial studies, hemolytic studies and MTT assay to assess their biocompatibility.

Incorporation of ZrO2 particles in the oxide layer formed on Mg by anodizing: Influence of electrolyte concentration and current modes.

HYPOTHESIS: The objectives of the present study are to ascertain, particle incorporation during the initial stages of microarc oxidation (MAO), feasibility of increasing the level of particle incorporation through manipulation of process variables and, the use of MgO-ZrO2 composite coatings either as a pre-treatment or as a post-treatment for MAO coated Mg. EXPERIMENTS: Anodic oxide coatings were prepared using 0.3M NaOH+15g/l ZrO2 and 3M NaOH+15g/l ZrO2 at 10V under direct current, pulsed current (PC) unipolar and PC bipolar modes. MAO coatings were prepared using 5g/l NaOH+15g/l Na2SiO3 at 250V under direct current mode for 2min. FINDINGS: The study reveals that it is possible to incorporate ZrO2 particles in the anodic oxide layer, suggesting such a possibility during the initial stages of MAO. When the MgO-ZrO2 composite coating is used as a pre-treatment, it helps to reduce the size and density of the pores of the MAO coatings and increased the corrosion resistance. When it is used as a post-treatment, lamellar shaped Mg(OH)2 with a very high surface area is formed on the surface, which would be beneficial to impart a better bioactivity and to facilitate immobilization of biomolecules.

A Facile Method to Modify the Characteristics and Corrosion Behavior of 304 Stainless Steel by Surface Nanostructuring toward Biomedical Applications.

The study addresses how surface nanostructuring of AISI 304 stainless steel (SS) by surface mechanical attrition treatment (SMAT) influences its characteristic properties and corrosion behavior in Ringer's solution. SMAT of 304 SS induced plastic deformation, enabled surface nanocrystallization, refined the grain size, transformed the austenite phase to strain induced α'-martensite phase, increased the surface roughness, induced defects/dislocations, imparted compressive residual stresses at the surface, decreased the contact angle, and increased surface energy. The change in properties of 304 SS following treatment using 5 and 8 mm ⌀ balls for 15, 30, 45, and 60 min has caused a deleterious influence on its corrosion resistance in Ringer's solution, while an improvement in corrosion behavior is observed for those treated using 2 mm ⌀ balls. The increase in surface roughness, transformation of the austenite to α'-martensite phase, a higher extent of deformation, and the presence of larger number of defects/dislocations are main factors responsible for the lower corrosion resistance observed for 304 SS treated using 5 and 8 mm ⌀ balls in Ringer's solution. In spite of having these attributes with a relatively lower extent, 304 SS treated using 2 mm ⌀ balls offered a better corrosion resistance and exhibits a better passivity. For those treated using 2 mm ⌀ balls, the ability of the nanocrystalline surface to promote passivation outweighs the deleterious influences caused by the limited amount of deformation and defects/dislocations. Based on the findings of this study, it is recommend that SMAT of 304 SS using 2 mm ⌀ balls for 15-30 min is the optimum condition to achieve the suitable surface profile, surface characteristics with better corrosion resistance.

Tailoring the composition of fluoride conversion coatings to achieve better corrosion protection of magnesium for biomedical applications.

The methodology of deposition of fluoride conversion coatings is modified with the use of galvanic coupling, agitation of the electrolyte solution, and addition of K2CO3, which helps to provide a better understanding of the mechanism and new avenues to tailor the composition of the coating. A very good correlation exists between the F/O ratio of the coatings prepared under varying experimental conditions and their icorr, |Z| and phase angle maximum; the higher the F/O ratio, the better the corrosion protective ability of the coatings in Hank's balanced salt solution. The corrosion behaviour of the coatings of the present study suggests that fluoride conversion coatings show much promise for their use for biomedical applications, as long as their uniformity is improved and the composition is tailored to enrich the MgF2 phase, encompassing a higher F/O ratio.

Corrosion behaviour of Ti-15Mo alloy for dental implant applications.

The corrosion behaviour of Ti-15Mo alloy in 0.15M NaCl solution containing varying concentrations of fluoride ions (190, 570, 1140 and 9500 ppm) is evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and chronoamperometric/current-time transient (CTT) studies to ascertain its suitability for dental implant applications. The study reveals that there is a strong dependence of the corrosion resistance of Ti-15Mo alloy on the concentration of fluoride ions in the electrolyte medium. Increase in fluoride ion concentration from 0 to 9500 ppm shifts the corrosion potential (E(corr)) from -275 to -457 mV vs. SCE, increases the corrosion current density (i(corr)) from 0.31 to 2.30 microA/cm(2), the passive current density (i(pass)) from 0.07 to 7.32 mA/cm(2) and the double-layer capacitance (C(dl)) from 9.63 x 10(-5) to 1.79 x 10(-4)F and reduces the charge transfer resistance (R(ct)) from 6.58 x 10(4) to 6.64 x 10(3)Omega cm(2). In spite of the active dissolution, the Ti-15Mo alloy exhibit passivity at anodic potentials at all concentrations of the fluoride ions studied. In dental implants since the exposure of the alloy will be limited only to its 'neck', the amount of Mo ions released from Ti-15Mo alloy is not likely to have an adverse and hence, in terms of biocompatibility this alloy seems to be acceptable for dental implant applications. The results of the study suggest that Ti-15Mo alloy can be a suitable alternative for dental implant applications.

Effect of acute and long-term oral tobacco use on oesophageal motility.

BACKGROUND AND AIMS: Nicotine administration is known to decrease lower oesophageal sphincter (LOS) pressure. Although a few studies have assessed the effect of tobacco on the LOS, the effect of acute and long-term oral tobacco use on oesophageal motility is not known. The study was designed to investigate the effect of acute and long-term oral tobacco use on LOS and distal oesophageal motility. METHODS: Thirty-six healthy men (aged 18-65 years, median 34 years; 18 oral tobacco users, 18 non-tobacco users) underwent oesophageal manometry using a water-perfusion system. After baseline manometry, tobacco users were asked to keep 0.5 g tobacco in their mouth for 10 min; non-users of tobacco were kept in quiet surroundings for a similar period. Manometry was then repeated. RESULTS: The LOS basal pressures were similar in tobacco users and non-tobacco users (mean +/- SD 15.4 +/- 6.3 vs 13.4 +/- 5.3 mmHg). In the distal oesophageal body, the velocity (4.4 +/- 3.1 vs 4.9 +/- 2.6 cm/s), amplitude (92.7 +/- 38.3 vs 84.8 +/- 33.2 mmHg) and duration of contraction (2.1 +/- 0.7 vs 1.7 +/- 0.9 s) were similar in tobacco users and non-users. Acute tobacco use did not affect these parameters. The numbers of abnormal waves (triple peaks and non-transmitted contractions) were also similar in the two groups. CONCLUSION: Oral tobacco use does not appear to affect LOS pressures and distal oesophageal motility acutely or in the long term.

Intestinal giardiasis: an unusual cause for hypoproteinemia.

Malabsorption is a well-known complication of infection with Giardia lamblia. However, selective protein-losing enteropathy is rare. We report a child with anasarca due to hypoalbuminemia as a result of gastrointestinal protein loss. Investigations established giardiasis as the etiology. The child returned to normal health after treatment with metronidazole.

Surgical management of the Budd-Chiari syndrome: early experience.

BACKGROUND: Early decompression is needed in the Budd-Chiari syndrome (BCS) to prevent liver dysfunction and death. AIMS: To study the technical difficulties during surgery and the results of surgery for BCS. METHODS: Retrospective review of nine patients operated on between 1994 and January 1998 for BCS--1 for uncontrolled fundal variceal bleed and 8 for chronic BCS. Isolated hepatic vein block was found in 5, inferior vena cava (IVC) block in 1 and a combination in 3 patients. Preoperative liver biopsies did not reveal cirrhosis in any patient. Portacaval shunt (3), portorenal shunt (2), mesocaval shunt (1), mesoatrial shunt (2) and devascularisation (1) were the operations performed. RESULTS: In 3 patients, side-to-side portacaval shunt was not possible because of caudate lobe hypertrophy (1), aberrant right hepatic artery (1) and presence of IVC stent (1); they required portorenal (2) or interposition mesocaval (1) shunts. Both mesoatrial shunts were unsuccessful. Devascularisation was effective in controlling the acute bleed. There was no intraoperative death. Postoperatively there were 3 deaths. Of the 6 survivors, 5 are asymptomatic over a mean follow up of 19.7 months. CONCLUSIONS: Side-to-side portacaval shunt is effective in the management of BCS; results with the mesoatrial shunt are disappointing.

Multiple abdominal venous thrombosis in HIV-seropositive patient.

HIV infection is known to be associated with endothelial dysfunction leading to thrombosis. We report a patient with multiple abdominal venous thrombosis and splenic hematoma who was seropositive for HIV-1. No cause for the hypercoagulable state was detected; prothrombin time, activated partial thromboplastin time, and levels of protein S, protein C and antithrombin III were normal. He tested negative for VDRL and anticardiolipin antibodies.