Enhanced antibacterial and corrosion resistance properties of Ag substituted hydroxyapatite/functionalized multiwall carbon nanotube nanocomposite coating on 316L stainless steel for biomedical application.

The present study reports the fabrication of silver substituted hydroxyapatite/functionalized multiwall carbon nanotube (Ag-HA/f-MWCNT) on 316L stainless steel (SS) implant by spray pyrolysis technique. XRD results show an enhanced crystallinity and crystallite sizes with increasing concentration of silver in HA/f-MWCNT. The vibrational spectral analysis revealed the presence of P-O stretching vibration of phosphate group (PO43-) in all the samples. The morphology of Ag substituted HA/f-MWCNT coatings revealed regular rod-like particles arranged in the form of sheet exhibiting slight variation in the size of the particle with increasing the Ag concentration. All the samples indicate the presence of calcium, phosphor, carbon, silver and oxygen constituents in the coating surface. The minimum inhibitory concentration of the nanocomposite decreased from 0.25 mg to 0.125 mg with the increase of Ag concentration, and AO/EB results confirmed the mode of cell distraction. The 1 and 3 wt% Ag-HA/f-MWCNT nanocomposite revealed less toxic effect to the normal human osteoblast cells. The corrosion efficiencies of the fabricated films in the stimulated body fluid reveal the increase in polarization resistance with a decrease in current density (icorr) from 3.9 to 3.5 µA due to the increase of Ag concentration. The estimated hemolysis rate for 1 and 3 wt% Ag substituted HA/f-MWCNT was less than 10%. Therefore, it can be concluded that 3 wt% Ag substituted HA/f-MWCNT coating on passivated 316L SS is nonhemolytic and most suited as a novel alternative to dental and orthopaedic implants.

High-dose BCNU/Melphalan conditioning regimen before autologous stem cell transplantation in newly diagnosed multiple myeloma.

Single-agent high-dose melphalan (HDM, 200 mg/m2) has been the most commonly used conditioning regimen prior to autologous stem cell transplant, since its introduction in 1992. We used a more aggressive alkylator-based conditioning regimen in an attempt to overcome early relapse and combat drug resistance. We present a retrospective comparison and long-term follow-up of newly diagnosed patients with multiple myeloma (MM) treated with induction followed by either high-dose carmustine (BCNU) and HDM, or HDM alone, both followed by autologous stem cell transplant (ASCT). Between 1997 and 2002, 104 patients were treated with BCNU/HDM; from 2001 to 2008, 103 patients were treated with HDM alone. Median follow-up of survivors was 78 and 68 months for the BCNU/HDM and HDM groups, respectively. The median PFS was significantly increased with the BCNU/HDM regimen (40.4 vs 20.5 months, P<0.001). Median overall survival was increased with the BCNU/HDM regimen when compared with HDM alone (88.4 vs 67.2 months, P=0.07), but the difference was not statistically significant. Transplant-related mortality was similar in both groups (2.9% with BCNU and HDM vs 3.9% with HDM alone). Our findings suggest that the BCNU/HDM preparative regimen should be investigated further and potentially compared in a prospective randomized manner with HDM alone.

Preferential killing of bacterial cells by hybrid carbon nanotube-MnO2 nanocomposite synthesized by novel microwave assisted processing.

We present a comprehensive study on the enhanced effect of CNT addition on the structural, optical, morphological and antibacterial properties of CNT-MnO2 nanocomposite synthesized by microwave assisted processing. X-ray diffraction pattern of the hybrid CNT/MnO2 nanocomposite revealed the shifting of highly oriented MnO2 preferential planes. SEM images show porous MnO2 nanospheres uniformly and discretely attached on the walls of carbon nanotube network. Significant variation in the peak shape and IR absorption intensity with CNT addition, indicate the interaction of CNT ions with MnO2 nanoparticles. Optical studies reveal a decrease in energy band gap caused by a significative reduction of electron-hole recombination in manganese activated CNT nanocomposite favouring photocatalytic activity. The antibacterial activity of pure MnO2 and the CNT/MnO2 hybrid was investigated by using both Gram positive and Gram negative bacteria as test organisms. The hybrid nanocomposite revealed higher antibacterial activity compared with pure MnO2 nanoparticles, due to reduced particle size and high specific surface area of CNT. Also, compared to Gram positive bacteria, Gram negative bacteria shows enhanced antibacterial activity due to the improved particle surface reactivity to visible light through effective charge transfer between MnO2 and CNT content of the nanopowder synthesized through microwave processing. Owing to the high surface area, large inner volume and other important physico-chemical properties, the antibacterial activity of carbon-based nanocomposites may interestingly be studied in the near future.

Substrate effect on the properties of functionalized multiwalled carbon nanotubes grown by e-beam evaporation for high performance H2O2 detection.

In the present study, the properties of functionalized multiwalled carbon nanotube thin films deposited on Ta and Al2O3 substrates were compared for better electrochemical sensing performance towards H2O2. We pioneer the fabrication of high quality carbon nanotubes by electron beam evaporation at a high vacuum of 10-6 mTorr. The fabricated films were further characterised using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Crystallographic properties revealed that the carbon nanotube (CNT) film grown on the Al2O3 substrate exhibits a preferentially oriented (002) peak with high intensity compared to that on Ta. CNTs fabricated on a Ta substrate show better morphology with tightly packed grains and decreased nanotube diameter than the film on sapphire. TEM images confirmed the well adherent and dense nature of the nanotubes on Ta. Electrochemical H2O2 sensors were constructed to demonstrate the sensing performance of CNT/Ta and CNT/sapphire electrodes. CV curves of the samples show high sensitivity for the MWCNT film grown on Ta due to the highly conductive acid resisting nature of the substrate, overcoming the obstacles to electrochemical H2O2 sensing. Compared with the CNT/sapphire electrode, the CNT/Ta electrode exhibited high electrocatalytic activity towards the oxidation of H2O2, as distinct nanotubes are electrochemically linked with the conductive Ta substrate. The CNTs on Ta revealed a very low detection limit of 0.07 µm due to the nanoporous morphology of the film which supported better penetration of electrolytes into the electrode material. The synergetic electrocatalytic effect of the CNT/Ta electrode with excellent redox chemistry is promising for the development of highly sensitive biosensors.