Sunlight-induced enhanced photocatalytic reduction of chromium (VI) and photocatalytic degradation of methylene blue dye and ciprofloxacin antibiotic by Sn3O4/SnS2 nanocomposite.

Detection of residual organic and inorganic species in water bodies, including drinking water, has led to developing strategies for their removal. Here, we report a very efficient method of removing Cr(VI), organic dye, and antibiotic from water using a type-II heterojunction based on Sn3O4/SnS2 solar photocatalyst. The toxic Cr(VI) species are reduced by photocatalytic methodology, while methylene blue (MB) dye and ciprofloxacin (CIP) antibiotics are removed by photocatalytic degradation. The structural, compositional, morphological, and optical properties of the hydrothermally synthesized photocatalyst have been studied. Under sunlight exposure, more than 99.9% of Cr(VI) is reduced within 60 min at a reaction rate of 0.066 min-1. While 99.6% of MB and 90% of CIP degradation are achieved in 90 min and 120 min, corresponding to photocatalytic degradation rates of 0.043 min-1 and 0.019 min-1, respectively. The total organic carbon after degradation corresponded to 85.1% for MB and 72.4% for CIP mineralization. The observed photocatalytic degradation is attributed to in situ generation of reactive oxygen species (ROS), e.g., superoxide radicals and hydroxyl radicals. The role of ROS towards photocatalytic degradation of MB and CIP, respectively, was confirmed from ROS scavenging studies. The MB and CIP degradation mechanism has been discussed by analyzing their degradation products.

Amine-amide functionalized graphene oxide sheets as bifunctional adsorbent for the removal of polar organic pollutants.

Effective mitigation of polar organic impurities from industrial effluents is a global environmental challenge. Here, we describe the solvothermal synthesis of ammonia-functionalized graphene oxide (NH3GO) sheets for adsorptive removal of diverse organic pollutants, such as cationic dye basic blue 41 (BB41), anionic dye methyl orange (MO), and ionic 4-nitrophenol (4-NP), in aqueous media. Structural analysis of NH3GO suggest a potent role of surface acidic and basic binding sites in adsorption of targets through an interplay of dynamic experimental variables, e.g., contact time, pH, initial adsorbate concentration, adsorbent mass, and temperature. At an initial pollutant concentration of 20 mg/L, equilibrium adsorption capacities for BB41, MO, and 4-NP were estimated at 199.5, 64.0, and 54.1 mg/g, respectively, with corresponding partition coefficients of 4156, 79.4, and 14.3 L/g, respectively. Experimental data of all three organic pollutants are best fitted by the pseudo-second-order kinetic model. The adsorption isotherm of BB41 follows a multilayer adsorption pattern, while those of MO and 4-NP fit into a monolayer adsorption pattern. The endothermic and spontaneous nature of the adsorption processes has also been explored for the three targets on NH3GO based on thermodynamic analysis. The prepared NH3GO sheets appear to be a promising adsorbent for the removal of polar organic dyes and aromatics in the solution phase.

A novel method of synthesis of small band gap SnS nanorods and its efficient photocatalytic dye degradation.

A facile one pot method has been developed for synthesis of stable (ξ=-37.5 mV), orthorhombic structured SnS nanorods capped with mercaptoacetic acid by precipitation method. The SnS nanorods were measured to be about 45 nm long with a diameter of 20 nm, as studied by transmission electron microscopy (TEM). The band gap of the MAA capped SnS nanorods was 1.81 eV, measured by diffused reflectance spectroscopy and was larger than the bulk SnS. The relative positions of highest valence band and lowest conduction band were determined from theoretical band structure calculation as 1.58 eV and -0.23 eV, respectively. The UV-Visible-NIR fluorescence emission spectrum of the SnS nanorods revealed intense emission peak at 1000 nm (1.239 eV) and weaker peaks at 935 nm, 1080 nm, 1160 nm which is likely to be due to Sn(2+) vacancies. The as-synthesized SnS nanorods exhibited more than 95% sunlight induced photocatalytic degradation of trypan blue in 4 h, following first order kinetics with high rate of degradation (k) (0.0124 min(-1)). The observed dye degradation is attributable to generation of reactive oxygen species (ROS), confirmed from terephthalic acid assay. The ROS generation has been explained on the basis of interaction between photoexcited electrons from conduction band with molecular oxygen adhered to the surface of nanorods owing to favourable redox potentials of O2/O2(-) (-0.20 eV) in normal hydrogen electrode (NHE) scale.

Elemental maps in human allantochorial placental vessels cells: 2. MgCl2 and MgSO4 effects.

Extracellular magnesium salts are known to interfere with ionic channels in the cellular membranes. The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K+ and Ca2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro-Particule Induced X-ray Emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMC) and of vascular endothelial cells (VEC) in the placental human allantochorial vessels in a physiological medium (Hanks' solution) modified by the addition of 2 mM MgCl2 or 2 mM MgSO4 which block the calcium-sensitive K+ channels (K(Ca)), the ATP-sensitive K+ channels (K(ATP)) and the voltage-sensitive K+ (K(df)) and Ca2+ channels. In VSMC (media layer), the addition of MgCl2 induced no modification of the K, Cl, P, S and Ca concentrations but increased the Na and Mg concentrations and the addition of MgSO4 only significantly increased the Mg concentration, the other ion concentrations remaining constant. In endothelium (VEC), MgCl2 or MgSO4 addition implicated the same observations as in VSMC. These results confirmed the blockage of K(df), K(Ca), K(ATP) and Ca channels in VSMC and VEC by magnesium salts, the relationship between Mg2+ ions and internal Na and demonstrated the possible intervention of a Na+/Mg2+ exchanger.

Anomalous antibacterial activity and dye degradation by selenium doped ZnO nanoparticles.

Selenium doped ZnO nanoparticles synthesized by mechanochemical method were spherically shaped of size distribution of 10.2±3.4 nm measured by transmission electron microscopy. Diffused reflectance spectroscopy revealed increase in the band gap, ranging between 3.47 eV and 3.63 eV due to Se doping in ZnO nanoparticles. The antibacterial activity of pristine and Se doped ZnO nanoparticles was attributed to ROS (reactive oxygen species) generation in culture media confirmed by TBARS assay. Compared to complete inhibition of growth by 0.45 mg/mL of pristine ZnO nanoparticles, the batches of 0.45 mg/mL of selenium doped ZnO nanoparticles exhibited only 51% inhibition of growth of Escherichia coli. The reduced antibacterial activity of selenium doped ZnO nanoparticles was attributed to two opposing factors, e.g., ROS generation for inhibition of growth, countered by sustaining growth of E. coli due to availability of Se micronutrients in culture media, confirmed by inductively coupled plasma mass spectrometer measurement. Higher ROS generation by selenium doped ZnO nanoparticles was attributed to creation of oxygen vacancies, confirmed from green emission peak observed at 565 nm. The impact of higher ROS generation by selenium doped ZnO nanoparticles was evident from enhanced photocatalytic degradation of trypan blue dye, than pristine ZnO nanoparticles.

Correlation between defects in capped ZnO nanoparticles and their antibacterial activity.

Antibacterial activity of ZnO nanoparticles (NPs) triggered by generation of reactive oxygen species (ROS) depends on the fate of photoexcited charge carriers. Batches of wide band gap ZnO NPs of 7-9nm sizes, capped with polyethylene glycol (PEG), ascorbic acid (AsA), mercaptoacetic acid (MAA) and polysorbate 80 (T-80) were synthesized by precipitation method. These capped ZnO NPs exhibited ROS induced antibacterial activity, where the ROS was measured by TBARS assay. The PEG capped and AsA capped ZnO NPs exhibited weaker antibacterial activity and were correlated with strong and broad green emission peak owing to oxygen vacancies. The oxygen vacancies were trap sites of photoexcited electrons which inhibited interaction between the photoexcited electrons and oxygen on the surface of the ZnO NPs and accounted for lesser ROS generation and subsequently weaker antibacterial activity. Contrastingly MAA capped and T-80 capped ZnO NPs did not exhibit significant green emission peak, but exhibited 13% and 43% inhibition of growth of E. coli, respectively. The lack of oxygen vacancy defects in MAA capped and T-80 capped ZnO NPs perhaps led to lesser trapping of charge carriers, which is favorable for higher ROS generation and consequently higher antibacterial activity.

Development of oxaliplatin encapsulated in magnetic nanocarriers of pectin as a potential targeted drug delivery for cancer therapy.

Superparamagnetic iron oxide nanoparticles (SPIONs) and oxaliplatin (OHP) were in-situ encapsulated in pectin cross-linked with Ca(2+) forming 100-200 nm sized magnetically functionalized pectin nanocarriers, referred here as MP-OHP nanocarriers. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies revealed formation of spherical nanostructures. The magnetic measurements by vibration sample magnetometer (VSM) revealed high saturation magnetization (M s=45.65 emu/g). The superparamagnetic property of MP-OHP was confirmed from the blocking temperature (T B) determined from field cooled and zero field cooled magnetization, measured by superconducting quantum unit interference device (SQUID) magnetometry. The stability of the aqueous dispersion of MP-OHP nanocarriers was confirmed from its high zeta potential (-30.5 mV). The drug encapsulation efficiency (55.2±4.8% w/w) and the drug loading content (0.10±0.04 wt%) in MP-OHP nanocarriers were determined from corresponding platinum contents in OHP and MP-OHP batches measured by inductively coupled plasma mass spectrometry (ICPMS). These nanocarriers exhibited a sustained release of OHP in phosphate buffer solution maintained at pH 5.5 and 7.4, where the drug release profile satisfied a combination of diffusion and swelling controlled mechanism. The cytotoxicity effect of MP-OHP nanocarriers was studied on MIA-PaCa-2 (pancreas) cancer cell line, where the GI50 values were more than 5 mg/mL and it exhibited 10 folds higher cytoxicity than the equivalent concentration of free drug.

Development of diclofenac sodium loaded magnetic nanocarriers of pectin interacted with chitosan for targeted and sustained drug delivery.

A novel spherical magnetic nanocarrier of 100-150 nm dimensions made of pectin interacted with chitosan (MPCh-DS0.05) resulted in 99.5% encapsulation efficiency of diclofenac sodium (DS) as a model drug. Similarly, magnetic nanocarrier made of only pectin crosslinked with Ca(2+) (MPDS-0.05) resulted in only 60.6% encapsulation efficiency of DS. The increase in drug encapsulation efficiency (%) in MPCh-DS0.05 batch was due to synergistic drug encapsulation properties of pectin and chitosan. The structural and morphological features of these magnetic nanocarriers were studied by X-ray diffractometry (XRD), Fourier transform infrared-spectrometry (FT-IR), thermogravimetry, electron microscopy and dynamic light scattering (DLS) measurements. The magnetic properties were measured by vibrating sample magnetometer (VSM) and superconducting quantum unit interference device measurements (SQUID). The in vitro drug release was pH sensitive and exhibited sustained release sequentially in simulated gastric fluid (negligible release in 0-2h), simulated intestinal fluid (~69% release in 2-5h), simulated colonic fluid (5-60 h) and also in phosphate buffer at pH 7.4 (0-48 h). The drug release profile in phosphate buffer solution at pH 7.4 was in good agreement with swelling controlled mechanism on the basis of Korsemeyer-Peppas model.

Development of a novel probe sonication assisted enhanced loading of 5-FU in SPION encapsulated pectin nanocarriers for magnetic targeted drug delivery system.

A novel probe sonication method is developed to enhance loading of 5-fluorouracil (5-FU) in SPION encalsulated pectin nanocarriers of 100-150 nm size (referred here as MP-5FU nanocarriers). Probe sonication at 20 kHz for 60 min resulted in 5-FU loading efficiency of 33.2 ± 2.5%w/w and corresponding drug loading content of 18.2 ± 1.1 wt%. These are two folds higher than literature report of 5-FU loading in pectin. The enhanced loading is attributed to increase in the rate of dissolution of 5-FU in pectin due to transmission of kHz order sonic waves which increases temperature and pressure in the medium due to formation and collapsing of cavitation bubbles. The fabricated MP-5FU nanocarriers with saturation magnetization (43.13 emu/g) exhibited pH responsive, swelling controlled in vitro release of 5-FU in simulated gastric fluid at pH 1.2, in simulated intestinal fluid at pH 6.8, in simulated colonic fluid at pH 5.5, and in phosphate buffer solution at pH 7.4. The cytotoxicity of MP-5FU was measured by sulforhodamine B (SRB) assay and its GI(50) was more than 5mg/mL for cancer cells of HT-29 (colon) and Hep G2 (liver), while it was 3.7 mg/mL for cancer cells of MIA-PaCa-2 (Pancreas).