Md. Abdulla-Al-Mamun

Au-ultrathin functionalized core–shell (Fe3O4@Au) monodispersed nanocubes for a combination of magnetic/plasmonic photothermal cancer cell killing

Magnetic nanocubes, with a controlled precursor molar concentration of ferric nitrate fixed at 0.004 M to ferrous chloride ranging from 0.002 to 0.01 M, were synthesized by a new simple colloidal method at 60 °C under 1 M alkaline condition. The metallic Au-ultrathin layer was successfully functionalized on the magnetic nanocubes surface for the fabrication of the core–shell structure (Fe3O4@Au) by the borohydrate reduction of HAuCl4 in water/poly-L-histidine solution. The functionalized core–shell structure with varying molar-ratios of Fe3+/Fe2+ in aqueous media, core–shell structural characteristics (for example, size, morphology, and shell thickness), and physical properties (for example, crystalline, electronic, optical, and magnetic ones) of the resultant functional nanocubes were systematically investigated using UV-visible spectroscopy, SEM, TEM, XRD, XPS, EDX, and superconducting quantum interface device (SQUID) magnetometer analysis. The core–shell structure of Fe3O4@Au exhibits plasmonic properties with high magnetization and showed excellent hyperthermia-photothemal activity towards the cancer cell (HeLa) killing. For the hyperthermia killing of cancer cells under the alternating current magnetic field (AMF), the as-prepared Fe3O4 exhibited higher activity than the Fe3O4@Au nanoparticles. Interestingly, under the simultaneously combined AMF and photoirradiation with Fe3O4@Au, much higher cancer cell killing was found than with only AMF induced hyperthermia killing. The promoting effect of an Au-ultrathin shell supported on Fe3O4 showed strong absorption in the visible region due to localized surface plasmon resonance and increased the hyperthermia-photothermal temperature with the photothermal stability of the Fe3O4@Au nanoparticles, rather than only Fe3O4. It was found that the cell killing activity depends on the optical and magnetic properties of the Fe3O4@Au nanocubes. The optical and magnetic properties depended on the molar-concentration ratios of precursors of Fe(NO3)3·9H2O and FeCl2·4H2O. The synthesized Fe3O4@Au nanocubes have great potential for a combination of cancer imaging and local treatment as a cancer cell killing paradigm of “see and treat” applications.

Enhanced photocatalytic cytotoxic activity of Ag@Fe-doped TiO2 nanocomposites against human epithelial carcinoma cells

Fe-doped TiO2 nanopowders with controlled molar-atomic ratios of iron to titanium oxide (in percentage) ranging from nominal 1 to 10% were synthesized by a new simple sol–gel method. Metallic Ag nanoparticles were successfully deposited on the nanopowder of the Fe-doped TiO2 surface by citrate reduction of AgNO3 in water/CH3CN mixture. The molar ratio of iron to TiO2, phase formation, bandgaps, crystallinity, catalytic and plasmonic properties of the resultant composites were systematically investigated using UV-visible spectroscopy, SEM, TEM, XRD, XPS, EDX, and photoluminescence spectral analyses. The photocatalytic activity of Ag@Fe-doped TiO2 composite nanoclusters was evaluated through photocatalytic killing of cancer cells. For the photocatalytic killing of cancer cells under visible light irradiation, as-prepared Ag@Fe-doped TiO2 nanopowders exhibited higher activity than Fe-doped TiO2. The promoting effect of the Ag nanoparticles deposited on the Fe-doped TiO2 surface showed strong absorption in the visible region due to localized surface plasmon resonance of Ag and inhibited the recombination of photoelectrons and holes rather than only Fe-doped TiO2. The cytotoxic cell killing efficiency depends on the molar ratio of Fe content to TiO2. The optimum Fe content in Fe-doped TiO2 was determined to be 5% due to the Fe/TiO2 molar ratio. Based on the obtained results, a plausible mechanism was also proposed.

Synergistic enhanced photocatalytic and photothermal activity of Au@TiO2 nanopellets against human epithelial carcinoma cells

The photocatalytic and plasmonic photothermal cancer cell-killing activity of the metallic Au-capped TiO(2) (Au@TiO(2)) composite colloidal nanopellets has been investigated on HeLa cells under UV-visible (350-600 nm) light irradiation. The Au@TiO(2) composite nanopellets with the uniform Au-capped TiO(2) structure were successfully synthesized by simple reduction of HAuCl(4) on the surface of TiO(2) nanoparticles. The morphological structure and surface properties of Au@TiO(2) were characterized by using UV-visible absorption spectroscopy, TEM, SEM, XPS, EDX and XRD analyses. The formation of hydroxyl radicals (˙OH) was confirmed by photoluminescence (PL) spectra. The photocatalytic and photothermal cell-killing activity of the Au@TiO(2) nanopellets was found to vary with the molar ratio of Au to TiO(2). The direct involvement of the metal particles in mediating the electron transfer from the photoexcited TiO(2) under the band gap excitation is considered to carry out the efficient photocatalytic reaction on the cells. The plasmonic absorption spectra of Au@TiO(2) suspensions were also measured for the evaluation of photothermal cell killing. The charge separation, the interfacial charge-transfer and photothermal activity promoted the photocatalytic-photothermal cancer-cell killing more than TiO(2) alone. The cytotoxic effect of Au@TiO(2) nanopellets with low concentration of gold (TiO(2) : Au molar ratio > 1 : 1) was found to be 100%, whereas that of the commercial TiO(2) (P25) was ca. 50%. The comparative study of the cell viability using Au alone and TiO(2) alone revealed that the synergistic effect of photocatalytic hydroxyl radical formation and Au-plasmonic photothermal heat generation plays a vital role in the cancer cell killing. A plausible mechanism was also proposed for photocatalytic cancer cell killing based on the obtained results.

Enhancement of cumulative photoirradiated and ac magnetic-field induced cancer (HeLa) cell killing efficacy of mixed α and γ-Fe2O3 magnetic nanoparticles

In this current study we synthesized mixed α and γ-Fe2O3 nanoparticles and their synergistic toxic effect against HeLa cells was investigated under ac (alternating current) magnetic-field induction and photoirradiation conditions at room temperature. The experiment was designed to find out the cancer cell killing efficacy of as-synthesized bare γ-Fe2O3, bare α-Fe2O3 and mixed α and γ-Fe2O3 nanoparticles under combined ac magnetic-field induction and photoirradiation conditions. The toxic effect of nanoparticles was obtained by counting the percentage of viable cells after all the treatments were completed using various concentrations. The results revealed that the highest toxic effect was obtained using mixed α and γ-Fe2O3 nanoparticles under combined ac magnetic-field induction and photoirradiation conditions at a dose of 60 μg mL−1 MEM (minimum essential medium), i.e., approximately 98% cancer cells were killed, whereas under only ac magnetic-field induction or only photoirradiation conditions, only 89% and 66% cancer cells were destroyed using the same dose of same nanomaterials, respectively. We also noticed that 55% and 79% cancer cells were destroyed using bare α-Fe2O3 and bare γ-Fe2O3 nanoparticles, respectively, under combined ac magnetic-field induction and photoirradiation conditions using the same dose. To the best of our understanding, the mechanism or reason for almost 100% HeLa cell killing under the combined conditions can be ascribed to the combined or additive effect of ac magnetic-field induced hyperthermia and photocatalytic cytotoxicity.

Enhancement Effect of Laser Ablation in Liquid On Hydrogen Production Using Titanium(Iv) Oxide and Graphite Silica

Photocatalytic hydrogen production from methanol solution containing mixture of TiO2 and graphite silica (GS) was enhanced by the laser ablation in liquid. Addition of TiO2 to lased GS increased the amount of hydrogen gas evolved two times as large as that of GS-TiO2 mixture. This may be attributed mainly to the aggregation of TiO2 and GS fined by the laser ablation.