Nanodiamond embedded polyaniline/polyvinylidene fluoride nanocomposites as microfiltration membranes for removal of industrial pollution.

Membrane fouling remains a challenge to the membrane technology. Herein, we report the fabrication of composite membranes of polyaniline/polyvinylidene fluoride (PANI/PVDF) blended with nanodiamond (ND) with improved antifouling properties. The designed membranes were characterized by XRD, FTIR and SEM techniques. Characterization analysis revealed that addition of ND has maintained the structural integrity and porosity of composite membranes. The membrane permeation and antifouling performances were tested for hydrophilicity, porosity, pure water flux, shrinkage ratio, salt rejection of zinc acetate and copper acetate, and their fouling recovery ratio (FRR) measurements. A high solvent content ratio of 0.55 and a low shrinkage ratio of <12% due to enhanced hydrophilicity and porosity of the composite membrane with fouling-recovery of membranes to 88% were achieved. Separation of copper and zinc ions from aqueous solution was achieved. These findings imply that ND-based PANI/PVDF composite membranes can effectively serve as microfiltration membranes in industrial and municipal wastewater treatment.

Spectrophotometric analysis of stability of gold nanoparticles during catalytic reduction of 4-nitrophenol.

Spectrophotometric monitoring of 4-nitrophenol (4-NP) reduction by sodium borohydride (NaBH4) using gold nanoparticles (GNPs) as a catalyst has been extensively studied, but the stability of GNPs in terms of change in the surface plasmon resonance (SPR) at different temperatures has not been explored. In the present investigation, our aim was to evaluate the SPR stability of GNPs as a catalyst during the reduction of 4-NP at different elevated temperatures (i.e. 30-60 °C) and sodium borohydride concentrations. Sensitivity of this degradation process toward concentration of GNPs at a range of temperatures is also evaluated. The spectrophotometric results reveal that up to 45 °C, 12 ± 1.5 nm catalyst has a consistent optical density (OD) during the entire 4-NP reduction process, which is related to the surface integrity of catalyst atoms. As the temperature approached 50 °C, the OD gradually decreased and showed a blue shift as the reaction proceeded, which could be related to a decrease in particle size or surface dissolution of gold atoms. The present study may find application in the design of catalysts for the reduction of organic pollutants in industrial wastewater at a range of temperatures.

Investigation of redox mechanism and DNA binding of novel 2-(x-nitrophenyl)-5-nitrobenzimidazole (x = 2, 3 and 4).

The present study describes the investigation of the binding modes of potential anti-cancerous nitrophenyl derivatives of 2-(x-nitrophenyl)-5-nitrobenzimidazole with calf thymus DNA. The -2-(x-nitrophenyl)-5-nitrobenzimidazoles under investigation differ only in position x of nitro group in nitrophenyl substituent relative to benzimidazole moiety leading to 1-NPNB (x = 2), 2-NPNB (x = 3) and 3-NPNB (x = 4). The DFT calculations predicted that derivatives were electrochemically reducible which was then confirmed by cyclic voltammetry. In cyclic voltammetry, the second reversible peak was dependent on first irreversible reduction. This revealed that electrochemical irreversible process was governed by some other process which was then followed by reversible second electron transfer. Thus, ECE (electron transfer leading to coupled chemical reaction followed by another electron transfer process) mechanism was attributed for electrochemical reduction. Experimental results based on UV-Vis spectroscopy vaguely showed intercalation of 1-NPNB, 2-NPNB and 3-NPNB into DNA which was assisted by cyclic voltammetry. However, thermal melting and florescence spectroscopy unambiguously established intercalation for all three compounds. Molecular docking analysis ascertained in pocket stacking of 5-nitrobenzimidazole moiety in 1-NPNB and 2-NPNB while nitro phenyl substitution in 3-NPNB stacks between DNA base pair during intercalation which was in agreement with DFT computed molecular geometry. Therefore, the relative positions of nitro group and 5-nitrobenzimidazole moieties in 2-(x-nitrophenyl)- 5-nitrobenzimidazole influenced the DNA binding pattern of compounds during intercalation. The cytotoxicity of these compounds was comparable to standard drug doxorubicin against both cancerous (MCF-7) and normal (MCF-10A) breast cells which depicts their anti-cancerous potential.

Preparation and catalytic evaluation of Au/γ -Al2O3 nanoparticles for the conversion of 4-nitrophenol to 4-aminophenol by spectrophotometric method.

A set of catalysts having gold nanoparticles deposited on γ -Al2O3 ( Au/ γ -Al2O3) with lowest effective amount of gold content were prepared by successive impregnation and hydrogen reduction method. The structural features of prepared catalysts were analysed by X-ray diffraction (XRD), N2 physisorption, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). The catalytic activity was evaluated for the reduction of an organic pollutant 4-nitrophenol (4NP) to 4-aminophenol (4AP) by spectrophotometric analysis. Supported catalyst presented excellent catalytic ability to convert 4NP to 4AP in the presence of sodium borohydride (SBH) due to synergistic effect of Au NPs and mesoporous γ -Al2O3 support. The reduction reaction was also performed at a range of temperatures to calculate kinetic parameters. The development of highly stable Au/γ -Al2O3 catalysts with lowest noble metal content and recyclability made the process cost effective and may promote their applications in various fields including removal of organic pollutants in industrial waste water and high-temperature gas-phase reactions.

Electrochemical, spectroscopic and theoretical monitoring of anthracyclines' interactions with DNA and ascorbic acid by adopting two routes: Cancer cell line studies.

Pharmacodynamic interactions of three anthracycline antibiotics namely doxorubicin (DXH), epirubicin (EpiDXH) and daunorubicin (DNR) with DNA in the absence and presence of ascorbic acid (AA) as natural additive were monitored under physiological conditions (pH = 7.4, 4.7 and T = 309.5K). Route-1 (Anthracycline-AA-DNA) and Route-2 (Anthracycline-DNA-AA) were adopted to see the interactional behavior by cyclic voltammetry (CV) and UV-visible spectroscopy. In comparison to Route-2; voltammetric and spectral responses as well as binding constant (Kb) and Gibb's free energy change (ΔG) values revealed strongest and more favorable interaction of anthracycline-AA complex with DNA via Route-1. Kb, s (binding site sizes) and ΔG evaluated from experimental (CV, UV-Vis) and theoretical (molecular docking) findings showed enhanced binding strength of tertiary complexes as compared to binary drug-DNA complexes. The results were found comparatively better at pH 7.4. Consistency was observed in binding parameters evaluated from experimental and theoretical techniques. Diffusion coefficients (Do) and heterogeneous electron transfer rate constant (ks,h) confirmed the formation of complexes via slow diffusion kinetics. Percent cell inhibition (%Cinh) of anthracyclines for non-small cell cancer cell lines (NSCCLs) H-1299 and H-157 were evaluated higher in the presence of AA which further complimented experimental and theoretical results.

Investigating the scavenging of reactive oxygen species by antioxidants via theoretical and experimental methods.

Reactive oxygen (hydroxyl OH, hydroperoxyl OOH) species are highly unstable to be studied experimentally under normal conditions. The present study reports the antioxidant potential of the vitamins namely ascorbic acid, riboflavin and nicotinic acid against these reactive oxygen species (ROS) using the predictive power of Density Functional Theory (DFT) (B3LYP with 6311G basis set) calculations. The order of reactivity of aforementioned vitamins was assessed by determining the bond dissociation enthalpy (BDE) of the OH bond, which is the controlling factor, if hydrogen atom transfer (HAT) mechanism is considered. Transition state calculations were also carried out to determine the reaction barrier for the radical scavenging reaction of vitamins by calculating the forward and the backward activation energies using the same level of theory as mentioned above. The theoretical methodology was first validated by taking a model stable free radical, 2, 2-diphenyl-1, picrylhydrazyl radical (DPPH) and applying the proposed approach followed by the experimental studies using UV-visible spectroscopy and cyclic voltammetry. The close agreement between the theoretical prediction and experimental observations proved the authenticity of theoretical approach.

In vitro investigations of gold nanocages: Toxicological profile in human keratinocyte cell line.

Gold nanocages (AuNCs) are comparatively novel nanostructures, as many of their characteristics are still to be exploited. The purpose of present study was to systematically investigate the toxicological effects of AuNCs on human keratinocyte cell line (HaCaT) utilizing Dark Field (DF)/Bright Field (BF) imaging and flow cytometry cell cycle techniques. We have applied surface modification, concentration, and incubation time of AuNCs as variables to investigate their effect on the cellular imaging and cell cycle response of HaCaT cells. The results indicate that the AuNCs interact with HaCaT cells in accordance to their surface charge and concentration. Cellular uptake is evident from DF images which lead to the cell cycle perturbations and apoptosis in HaCaT cells. AuNCs cause a prominent G2/M phase arrest after 24 h of incubation. To the best of our knowledge toxicological effects of AuNCs on cell cycle of HaCaT cell line in vitro are not reported previously.

Interaction of gold nanoparticles with free radicals and their role in enhancing the scavenging activity of ascorbic acid.

The present study investigates the interaction of citrate stabilized gold nanoparticles (12±1.5nm) (GNPs) with free radicals; 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable and electrochemically generated superoxide, O2(-). Different experiments were designed to understand the interaction between GNPs and DPPH by employing cyclic voltammetry, UV-vis spectroscopy and computational chemistry using 6-311G basis set. The increase in heterogeneous rate constant, ksh, of DPPH upon addition of GNPs pointed towards possible complex formation, DPPH-GNPs which were further explained by a model assuming surface adsorption of DPPH on GNPs. Further, the model was validated by studying interaction of GNPs with a biologically important free radical, O2(-). Exciting result in terms of disappearance of anodic peak after GNPs addition confirmed that gold nanoparticles interacted with stable as well as unstable free radicals. Also, the stoichiometry of the most stable complex GNP-DPPH was determined from UV-vis spectroscopy by applying Job's method. The GNP-DPPH complex was found to be active with 46.0% reduction of the IC50 value of standard antioxidant, ascorbic acid (AA), indicating its role in enhancing antioxidant activity. Hence, this study presents a simple and potential approach to enhance the efficiency of natural antioxidants without modifying their structure, or involving the complex functionalization of GNPs with antioxidants.

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases.

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms.

Interaction of antihypertensive acetazolamide with nonsteroidal anti-inflammatory drugs.

The binding of antihypertensive acetazolamide with eleven nonsteroidal anti-inflammatory drugs (NSAIDs) was investigated at pH 3, 7 and 9.5 with the objective of monitoring their interactive pharmacokinetics during digestion and absorption in human body. The results of UV-Vis spectroscopy and cyclic voltammetry revealed two NSAIDs (acetaminophen and dichlofenic sodium) to interact with acetazolamide in stomach fluid conditions forming complexes of 1:1 and 1:2 stoichiometry. The complexation ratio was also verified by computational methods. The strong binding propensity of acetaminophen and dichlofenic sodium with acetazolamide prohibited their combined therapy. However, the poor binding affinity of aspirin and mefinamic acid suggested these drugs as preferred NSAIDs to be prescribed with acetazolamide.

Characterization and DNA binding studies of unexplored imidazolidines by electronic absorption spectroscopy and cyclic voltammetry.

UV-Vis spectroscopic behavior of four imidazolidine derivatives i.e., [5-benzylideneimidazolidine-2,4-dione (NBI), 5-(2-hydroxybenzylidene)imidazolidine-2,4-dione (HBI), 5-(4-methoxybenzylidene)imidazolidine-2,4-dione (MBI) and 5-(3,4-di-methoxybenzylidene)imidazolidine-2,4-dione (DBI)] was studied in a wide pH range. Spectroscopic response of the studied compounds was found sensitive to pH and the attached substituents. Incited by anti-tumor activity, structural miscellany and biological applications of imidazolidines, the DNA binding affinity of some novel derivatives of this class of compounds was examined by cyclic voltammetry (CV) and UV-Vis spectroscopy at pH values of blood (7.4) and lysosomes (4.5). The CV results showed the following order of binding strength: KNBI (6.40×10(6)M(-1))>KHBI (1.77×10(5)M(-1))>KMBI (2.06×10(4)M(-1))>KDBI (1.01×10(4)M(-1)) at pH 7.4. The same order was also obtained from UV-Vis spectroscopy. The greater affinity of NBI justified its preferred candidature as an effective anti-cancer drug. The DNA binding propensity of these compounds was found comparable or greater than most of the clinically used anticancer drugs.

Negotiation of intracellular membrane barriers by TAT-modified gold nanoparticles.

This paper contributes to the debate on how nanosized objects negotiate membrane barriers inside biological cells. The uptake of peptide-modified gold nanoparticles by HeLa cells has been quantified using atomic emission spectroscopy. The TAT peptide from the HIV virus was singled out as a particularly effective promoter of cellular uptake. The evolution of the intracellular distribution of TAT-modified gold nanoparticles with time has been studied in detail by TEM and systematic image analysis. An unusual trend of particles disappearing from the cytosol and the nucleus and accumulating massively in vesicular bodies was observed. Subsequent release of the particles, both by membrane rupture and by direct transfer across the membrane boundary, was frequently found. Ultimately, near total clearing of particles from the cells occurred. This work provides support for the hypothesis that cell-penetrating peptides can enable small objects to negotiate membrane barriers also in the absence of dedicated transport mechanisms.

Diorganotin(IV) derivatives of ONO tridentate Schiff base: synthesis, crystal structure, in vitro antimicrobial, anti-leishmanial and DNA binding studies.

Six new diorganotin(IV) derivatives of N'-(2-hydroxybenzylidene)formohydrazide (H(2)L) with general formula R(2)SnL, where R = Ph (1), Me (2), Bu (3), Oct (4), t-Bu (5), Et (6), and L = [OC(6)H(4)CHNNCHO] have been synthesized and characterized by different analytical techniques. Crystal structure of Me(2)SnL (2) authenticated distorted square-pyramidal geometry around the Sn atom. The CV and UV-Vis spectroscopic data indicated intercalation of complexes into DNA with binding affinity varying in the sequence: 3 (1.69 x 10(4) M(-1)) > 1 (1.10 x 10(4) M(-1)) > 2 (9.61 x 10(3) M(-1)). Some of these compounds were found to be good antibacterial, antifungal and leishmanicidal agents.

Electrochemical reduction mechanism of camptothecin at glassy carbon electrode.

Camptothecin (CPT) is a cytotoxic quinoline alkaloid endowed with the inhibition of topoisomerase I, an essential enzyme for the normal functioning of DNA. The redox behaviour of CPT was investigated at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry. It was shown that CPT can undergo reduction in a pH-dependent mechanism. In acid media only one irreversible charge transfer reaction was observed whereas by increasing the pH of the supporting electrolyte, two reduction peaks occurred. The diffusion coefficient of CPT was calculated in pH 4.5 0.1M acetate buffer using cyclic voltammetry to be D(CPT)=5.77x10(-6)cm(2)s(-1). Differential pulse voltammetry measurements were carried out over a wide pH range and allowed the determination of the number of electrons and protons transferred during each step in the CPT reduction mechanism, one electron and one proton. The use of square wave voltammetry proved the quasi-reversibility of CPT reduction as a function of the pH of the supporting electrolyte. Based upon the results obtained a reduction mechanism was proposed and the observed waves were attributed to the hydroxylation of the lactone ring of CPT to a lactol ring.

Voltammetric and spectroscopic investigations of 4-nitrophenylferrocene interacting with DNA.

Cyclic voltammetry (CV) coupled with UV-vis and fluorescence spectroscopy were used to probe the interaction of potential anticancer drug, 4-nitrophenylferrocene (NFC) with DNA. The electrostatic interaction of the positively charged NFC with the anionic phosphate of DNA was evidenced by the findings like negative formal potential shift in CV, ionic strength effect, smaller bathochromic shift in UV-vis spectroscopy, incomplete quenching in the emission spectra and decrease in viscosity. The diffusion coefficients of the free and DNA bound forms of the drug were evaluated from Randles-Sevcik equation. The binding parameters like binding constant, ratio of binding constants (K(red)/K(ox)), binding site size and binding free energy were determined from voltammetric data. The binding constant was also determined from UV-vis and fluorescence spectroscopy with a value quite close to that obtained from CV.

Electrochemical behaviour of dimethyl-2-oxoglutarate on glassy carbon electrode.

The electrochemical behaviour of dimethyl-2-oxoglutarate (MOG), a key intermediate in the Krebs cycle and an important nitrogen transporter in the metabolic pathways in biological processes, was investigated by cyclic voltammetry, square wave voltammetry and differential pulse voltammetry using a glassy carbon electrode. The reduction of MOG is an irreversible diffusion-controlled process that occurs in a cascade mechanism. For electrolytes with pH <3.0 and pH >7.0 one peak occurred and for 3.0

Spectrophotometric analysis of flavonoid-DNA binding interactions at physiological conditions.

Mode of interactions of three flavonoids [morin (M), quercetin (Q), and rutin (R)] with chicken blood ds.DNA (ck.DNA) has been investigated spectrophotometrically at different temperatures including body temperature (310 K) and at two physiological pH values, i.e. 7.4 (human blood pH) and 4.7 (stomach pH). The binding constants, K(f), evaluated using Benesi-Hildebrand equation showed that the flavonoids bind effectively through intercalation at both pH values and body temperature. Quercetin, somehow, showed greater binding capabilities with DNA. The free energies of flavonoid-DNA complexes indicated the spontaneity of their binding. The order of binding constants of three flavonoids at both pH values were found to be K(f(Q)) > K(f(R)) > K(f(M)) and at 310 K.

Synthesis, spectroscopic characterization, X-ray structure and evaluation of binding parameters of new triorganotin(IV) dithiocarboxylates with DNA.

Three new triorganotin(IV) dithiocarboxylates (1-3) with general formula R(3)SnL, where R=C(4)H(9) (1), C(6)H(11) (2), C(6)H(5) (3) and L=4-(4-nitrophenyl)piperazine-1-carbodithioate, have been synthesized and characterized by elemental analysis, Raman, FT-IR, multinuclear NMR ((1)H, (13)C and (119)Sn) and mass spectrometry. The crystal structure of complex 3 confirmed distorted trigonal-bipyramidal geometry around Sn atom. The interaction of compounds 1-3 with DNA was investigated by cyclic voltammetry (CV) and UV-vis spectroscopy. The positive peak potential shift in CV and hypochromic effect in spectroscopy evidenced intercalative mode of interaction. The results indicate that the binding affinity varies in this sequence: 1>3>2.

Electrochemical and spectroscopic investigations of protonated ferrocene-DNA intercalation.

The interaction of protonated ferrocene (PF) with chicken blood DNA (CB-DNA) has been investigated in vitro by cyclic voltammetry (CV) and UV-Vis spectroscopy as well as viscosity measurements under stomach pH and body temperature. The peak potentials shift in CV, hyperchromism in UV absorption titration, an increase in the viscosity of DNA and the results of the effect of ionic strength on the binding constant strongly support the intercalation of PF into the DNA double helix. The diffusion coefficients of PF in the presence and absence of DNA were 9.54 x 10(-11) and 1.34 x 10(-10) m2/s, respectively. The binding constant of the PF-DNA complex and the number of binding sites on a DNA molecule were calculated as being 3.07 x 10(2) M(-1) and 2.96, with the help of the Scatchard equation. An expression by Carter et al. was used for determining the binding site size (0.17 bp). The binding constant was also determined by UV absorption titration.

Charge transfer complexes of picolines with sigma- and pi-acceptors.

In the present study CT complexes of 2-, 3- and 4-Picolines with (DDQ) 2, 3-dichloro-5, 6-dicyano parabenzoquinone (pi-acceptor) and (I2) Iodine (sigma-acceptor) have been investigated spectrophotometrically in three different solvents (CCl4, CHCl3 and CH2Cl2) at six different temperatures. The formation constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters were calculated by Van(')t Hoff equation. The DeltaH degrees , DeltaG degrees and DeltaS degrees values are all negative implying that the formation of studied complexes is exothermic in nature.