Fabrication of SnS/TiO2@GO Composite Coated Glassy Carbon Electrode for Concomitant Determination of Paracetamol, Tryptophan, and Caffeine in Pharmaceutical Formulations.

Designing an electrochemical sensor which is simple, cheap, sensitive, fast, and accurate is inevitable, as it is important in drug quality control, point-of-care diagnosis, and other clinical studies. Sensors for simultaneous determination of paracetamol, tryptophan, and caffeine have not been reported so far, and we report an electrochemical sensor via incorporating tin sulfide (SnS) and titanium dioxide (TiO2) on graphene oxide (GO) sheets (SnS/TiO2@GO ternary composite) for their separate and simultaneous determination through cyclic voltammetry and differential pulse voltammetry techniques. The surface morphology and structural properties of the composite were characterized by analytical techniques. The electrochemical study of SnS/TiO2@GO composite modified glassy carbon electrode (GC-SnS/TiO2@GO) showed high activity toward the oxidation of paracetamol, tryptophan, and caffeine with significant decrease in overpotential due to large surface and high carrier mobility. The peak currents during separate determination of paracetamol, tryptophan, and caffeine increased linearly with the increase in concentration from 9.8 nM to 280 µM for paracetamol, from 13.3 nM to 157 µM for tryptophan, and from 16.6 nM to 333 µM for caffeine. The detection limit (3σ/ S) was 7.5, 7.8, and 4.4 nM for paracetamol, tryptophan, and caffeine, respectively. The electron transfer coefficient (α), surface coverage concentration (Γ), number of electrons transferred ( n), and diffusion coefficient ( D) were calculated and discussed. The fabricated electrode showed low detection limit, wide linear range, and excellent reproducibility, selectivity, and stability. The study was also extended to the analysis of commercial tablets, beverage and human blood serum.Therefore, the present electrode holds great promise for identification and quantification of drugs in combination.

Surface Grafted Hyper-Branched Polyglycerol Stabilized Ag and AuNPs Heterogeneous Catalysts for Efficient Reduction of Congo Red.

Six types of insoluble polymer-supported beads immobilized with Ag and AuNPs nanoparticle catalysts were synthesized using newly prepared three different types of polymer-supported poly(styrene)-co-poly(vinyl benzene chloride) matrix (PS-PVBC), surface grafted with (i) triethanolamine (TEA), (ii) glycidyl trimethyl ammonium chloride (GTMAC) and (iii) hyper-branched polyglycerol (HPG) and Ag and AuNPs as a catalytic moiety and thus yield polymer-supported nanoparticle catalysts viz., PS-PVBC-TEA-AgNPs and AuNPs, PS-PVBC-g-GTMAC-AgNPs and AuNPs and PS-PVBC-g-GTMAC-AgNPs and AuNPs catalyst respectively. These bead-shaped heterogonous nanoparticle catalysts were characterized by UV-Vis, FTIR, FESEM, HRTEM and TGA techniques. The efficiency for stabilization/loading of metal nanoparticles with respect to varied intensities of hyper-branched chain grafted onto their matrix was screened by determining their comparative catalytic activity. The catalytic potential of these catalysts was inspected through reduction of Congo Red (CR) keeping pseudo first order identical reaction condition. The observed k(obs) values reveal that irrespective of metal the catalyst derived from hyper-branched polyglycerol as stabilizing agent viz., PS-PVBC-g-HPG-AgNPs and PS-PVBC-g-HPG-AuNPs shows (k(obs) = 3.98 x 10⁻² min⁻¹ and k(obs) = 4.54 x 10⁻² min⁻¹) four and two times greater activity than the catalyst derived from TEA and GTMAC hyper-branched chain. Further, for the same reaction PS-PVBC-g-HPG-AuNPs showed more efficiency than the PS-PVBC-g-HPG AgNPs catalyst. The stability and reusability of the superior catalyst viz., PS-PVBC-g-HPG-AuNPs catalyst was observed to be good even at the sixth cycle. This catalyst can be continuously used to conduct the reduction of various dyes in continuous mode operation in industrial scale.

Collagen Biocomposites Derived from Fish Waste: Doped and Cross-Linked with Functionalized Fe3O4 Nanoparticles and Their Comparative Studies with a Green Approach.

Collagen-based nanobiocomposites can reabsorb and are biodegradable. These properties are effectively controlled by the number of cross-links. This study demonstrates an effortless and proficient approach for the functionalization of Fe3O4 NPs for cross-linking collagen obtained from biowaste, viz., fish scales of Lates Calcarifer, a marine origin. The size of Fe3O4 NPs (10-40 nm) was confirmed using particle size analysis. The physico-chemical properties of the aminosilane-coated Fe3O4 NPs cross-linked via succinylated collagen (FFCSC) were characterized using different analytical techniques and compared with succinylated collagen doped with Fe3O4 NPs (FDSC). Thermogravimetric analysis indicates cross-linked product FFCSC to be more stable than the FDSC. Also, the antibacterial effect was more pronounced for FFCSC than for FDSC nanobiocomposites. FFCSC exhibited improved mechanical properties which are essential for materials used for wound dressing purposes. Moreover, the cell viability of fibroblasts (3T3-L1) and their morphology studied by SEM and fluorescence microscopy showed biocompatibility of both FDSC and FFCSC. Thus, the current investigation, involves a waste to wealth approach where the collagen-based nanobiocomposites present an easy way to recycle the biowaste to value-added products using simple and clean methods, which are suitable for use in biomedical and environmental applications.

Multiwalled Carbon Nanotubes/Gold Nanoparticles Hybrid Electrodes for Enzyme-Free Electrochemical Glucose Sensor.

We followed a facile strategy to fabricate glucose sensors using mildly oxidized multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (AuNPs) and thiol acids including mercaptoacetic acid (MAA), mercaptopropionic acid (MPA), and mercaptosuccinic acid (MSA). The thiol acids separately bonded to MWCNTs anchored AuNPs of average diameter 14 nm, and yielded three different nanohybrids; MWCNTs-MAA-AuNPs, MWCNTs-MPA-AuNPs and MWCNTs-MSA-AuNPs. The nanohybrids after coating onto glassy carbon (GC) electrode resulted into enzyme free glucose sensors (GC-MWCNTs-MAA-AuNPs, GC-MWCNTs-MPA-AuNPs and GC-MWCNTs-MSA-AuNPs). Their electrocatalytic glucose sensing ability was examined through cyclic voltammetry and amperometry. GC-MWCNTs-MSA-AuNPs electrode showed high stability and activity in the electrocatalytic oxidation of glucose compared to other two sensors. It also showed a wide range of response for glucose concentration from 0.12 to 4.0 µM, and low detection limit of 0.036 µM (S/N = 3). The optimum rate of applied potential was 0.8 V/s, which proves the effective sensing of glucose. The selective sensing of glucose in the presence of H2O2, uric acid and blood cancer drug (imatinib mesylate) was verified through amperometry. The electrode can be a new addition to glucose sensors and bioanalytical techniques.

Core-Shell Nanostructured Fe3O4-Poly(styrene-co-vinylbenzyl chloride) Grafted PPI Dendrimers Stabilized with AuNPs/PdNPs for Efficient Nuclease Activity.

Four different novel magnetic core-shell nanocomposites stabilized with Au/Pd nanoparticles (NPs) were prepared by a simple procedure and demonstrated their catalytic activity for effective cleavage of pBR322 DNA. Initially, the Fe3O4-poly(styrene-divinylbenzene-vinylbenzyl chloride) (ST-DVB-VBC) matrix functionalized with 3-aminobenzoic acid was prepared and grafted with PPI-G(2) and PPI-G(3) dendrimers. Each core-shell matrix was immobilized with AuNPs and PdNPs separately. The resulting composites were characterized by FT-IR, UV-vis, SEM, TEM, XRD, VSM, XPS, Raman, and TGA. The magnetic core-shell nanocomposites at concentrations from 30 to 50 µM were employed separately to study DNA cleavage by agarose gel electrophoresis. Among the four magnetic core-shell nanocomposites, Fe3O4-poly(ST-DVB-VBC)-PPI-G(3)-AuNPs showed higher activity than others for DNA cleavage, and formed Form-II and -III DNA. When the concentration of Fe3O4-poly(ST-DVB-VBC)-PPI-G(3)-AuNPs was increased from 40 to 45 and 45 to 50 µM, Form-III (linear) DNA was observed with 10 and 22%, respectively, in addition to Form-II. This observation suggests formation of linear DNA from the supercoiled DNA via nicked DNA-intermediated consecutive cleaving process. The magnetic core-shell nanocomposites were stable and monodispersed, and exhibited rapid magnetic response. These properties are crucial for their application in biomolecular separations and targeted drug-delivery in the future.

Environmentally benign heterogeneous nano-particle catalysts: synthesis, characterization and catalytic activity of 4-nitrophenol.

Pollution free catalyst is an attractive area of current interest. The p-Aminophenol is one of the most significant catalyst, because it involves the manufacture of various pharmaceuticals. Crosslinked poly(styrene)-co-poly(4-vinylimidazole) (PSPVIM) was prepared by varying the crosslinked monomer ratio as 2% and 10% respectively. The 2 (w%) of DVB, 25 (w%) of N-VIm as functional monomer and 73 (w%) of styrene as support monomer as organic phase and gelatin, boric acid and polyvinyl alcohol as aqueous phase was used to prepare cross-linked poly(styrene)-co-poly(N-vinyl imidazole) (PVIM) beads (Type-I). Similarly, Type II beads were also prepared by fixing the 10% as a cross linking ratio (DVB). The immobilization of Ag NPs onto the PS-VIm polymer matrix was performed using AgNO3 as a metal precursor solution. The k(obs) determined from UV-Vis results, reveals that the degree of reduction of 4-nitrophenol using Type-I catalysts is more effective than Type-II catalyst due to lower immobilization of AgNPs at higher cross-linked bead matrix. It was found that on increasing the amount of catalyst i.e., type-I PS-PVIm-AgNPs, the rate constant also increases. Therefore, PS-PVIm-AgNPs (Type-I) heterogeneous catalyst is superior for the reduction of 4-NP.

Development of stable pollution free TiO2/Au nanoparticle immobilized green photo catalyst for degradation of methyl orange.

Two types of heterogeneous nanoparticle immobilized photocatalysts viz., PSP4VP-TiO2 and PSP4VP-TiO2-Au were synthesized by immobilization of TiO2 and TiO2-Au nanoparticles individually onto the insoluble cross-linked poly(styrene)-co-poly(4-vinylpyridine) as a common matrix. These two different green photocatalysts were characterized by FT-IR, SEM, HRTEM and EDS analyses and proves that the respective nanoparticles were found to immobilize onto the matrix. The photocatalytic efficiency of these catalysts was examined using degradation of methyl orange as a model reaction and found they are excellent in UV and sunlight. The stability and recycle/reusability of the catalysts were also observed to be good.

Catalysis by hydrophobically modified poly(propylenimine) dendrimers having quaternary ammonium and tertiary amine functionality.

Four different quaternary ammonium chloride-modified poly(propylenimine) (PPI) dendrimers were synthesized by alkylation of a PPI dendrimer having eight dimethylamino end groups with 1-bromooctane or 1-bromododecane. By varying the mole ratio of alkyl bromide to dendrimer, averages of 4-10 quaternary ammonium groups were formed. The new amphiphilic dendrimers are surface active and are micellar catalysts in water. The dendrimers have critical aggregation concentrations between 8.5 x 10(-4) and 9.0 x 10(-5) M. Decarboxylation of 6-nitrobenzisoxazole-3-carboxylate at 25 degrees C was 650 times faster than in water alone in the presence of a dendrimer quaternized with eight dodecyl chains at a concentration of 2.45 mM in quaternary ammonium groups. The order of the catalytic efficiency of the new dendrimers decreased with the length and number of hydrophobic alkyl groups in the order (C(12))(8) > (C(12))(4) > (C(8))(10) > (C(8))(5). The pseudo-first-order rate constants for basic hydrolysis of p-nitrophenyl hexanoate in pH 9.4 buffer at 30 degrees C using the (C(12))(8) and (C(12))(4) dendrimers were 26 and 13 times higher than those for hydrolysis with no dendrimer. The kinetic data were fit to a single-site binding model to evaluate the contributions of binding constants of reactants to the dendrimers and catalytic rate constants of the bound species to the overall catalytic activity.