An eco-friendly route of γ-Fe2O3 nanoparticles formation and investigation of the mechanical properties of the HPMC-γ-Fe2O3 nanocomposites.

In recent times, biosynthetic approaches toward the synthesis of nanoparticles have been shown to have several advantages over physical and chemical methods. Here, we report the extracellular mycosynthesis of γ-Fe2O3 nanoparticles by Alternaria alternata. The fungal biomass when exposed to aqueous iron(III) chloride solution led to the formation of highly stable γ-Fe2O3 nanoparticles extracellularly. The influence of these biosynthesized γ-Fe2O3 nanoparticles on the properties of hydroxyl propyl methyl cellulose was also investigated. Characterization of the biosynthesized γ-Fe2O3 nanoparticles and HPMC-γ-Fe2O3 nanocomposite films were done by the different types of spectral and electron microscopic analysis. The size of the γ-Fe2O3 nanoparticles ranges from 75 to 650 nm. The mechanical effect of the agglomerated γ-Fe2O3 nanoparticles into the HPMC polymer matrix was also investigated.

Dextrin-mediated synthesis of Ag NPs for colorimetric assays of Cu(2+) ion and Au NPs for catalytic activity.

A facile one-pot approach for rapid synthesis of silver and gold nanoparticles (Ag NPs and Au NPs) with narrow size distribution and good stability was described by reducing silver nitrate and chloroauric acid with polysaccharide dextrin. Here, dextrin was used as both a reducing and stabilizing agent for synthesis of NPs. The as-synthesized Ag NPs and Au NPs were characterized by UV-visible absorption spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The Ag NPs and Au NPs exhibited an absorption maxima at 404 and 547 nm respectively. TEM images showed NPs in the range of 8-28 nm. The crystallinity of the NPs was measured by XRD analysis. Furthermore, the as-prepared Ag NPs revealed colorimetric sensor property for detection of Cu(2+) ions based on changes in absorbance resulting from metal ion-induced aggregation of NPs or direct deposition of metal ions onto NPs. The as-prepared Au NPs exhibited a notable catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4.

Antibacterial activity of Ag-Au alloy NPs and chemical sensor property of Au NPs synthesized by dextran.

Gold and silver-gold alloy nanoparticles with mean diameter of 10nm and narrow size distribution were prepared by reduction of the correspondent metal precursors using aqueous dextran solution which acts as both a reducing and capping agent. The formation of nanoparticles was characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and dynamic light scattering (DLS). The silver and gold nanoparticles exhibited absorption maxima at 425 and 551 nm respectively; while for the bimetallic Ag-Au alloy appeared 520 nm in between them. TEM images showed monodispersed particles in the range of 8-10nm. The crystallinity of the nanoparticles was assured by XRD analysis. DLS data gave particle size distribution. The dextran stabilized Au nanoparticles used as a colorimetric sensor for detection and estimation of pesticide present in water. The dextran stabilized Ag-Au alloy nanoparticles exhibited interesting antimicrobial activity against bacteria at micromolar concentrations.

Assessment of morphology and property of graphene oxide-hydroxypropylmethylcellulose nanocomposite films.

Graphene oxide (GO) was synthesized by Hummer's method and characterized by using Fourier transform infrared spectroscopy and Raman spectroscopy. The as synthesized GO was used to make GO/hydroxypropylmethylcellulose (HPMC) nanocomposite films by the solution mixing method using different concentrations of GO. The nanocomposite films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and thermo-gravimetric analysis. Mechanical properties, water absorption property and water vapor transmission rate were also measured. XRD analysis showed the formation of exfoliated HPMC/GO nanocomposites films. The FESEM results revealed high interfacial adhesion between the GO and HPMC matrix. The tensile strength and Young's modulus of the nanocomposite films containing the highest weight percentage of GO increased sharply. The thermal stability of HPMC/GO nanocomposites was slightly better than pure HPMC. The water absorption and water vapor transmission rate of HPMC film was reduced with the addition of up to 1 wt% GO.

Effect of PEG-salt mixture on the gelation temperature and morphology of MC gel for sustained delivery of drug.

Gelation temperature of MC was reduced from 59°C to 54°C with the addition of 10% PEG. Sodium tartrate (NaT) and sodium citrate (NaC) were added to the MC-PEG solution to further reduce the gelation temperature close to physiological temperature. Different techniques were used to measure the gelation temperature of all formulations. It was observed that NaC was more effective in reducing the gelation temperature of MC-PEG combination than NaT. Environmental scanning electron microscopy (ESEM) images of hydrogels containing NaC and NaT showed that NaC containing hydrogel having an interconnected microporous structure instead of the hollow rod like structure as in the case of NaT containing hydrogel. In vitro drug release studies showed that drug release time increased from 6 to 9h by only changing the type of salt from NaT to NaC in MC-PEG combination.

Synthesis of HPMC stabilized nickel nanoparticles and investigation of their magnetic and catalytic properties.

Nickel nanoparticles synthesized from NiCl2·6H2O by hydrazine hydrate in mixed solvent of ethanol and water in the presence of hydroxypropylmethylcellulose (HPMC) as protective and stabilizing agents. The morphology and sizes of synthesized Ni nanoparticles were studied by field-emission-scanning-electron microscopy (FESEM). Structural properties of nanoparticles were examined by X-ray diffraction (XRD). The polymer stabilized Ni nanoparticles were characterized by Fourier-transform infrared (FTIR) spectroscopy. The magnetic measurement showed that the resultant Ni nanoparticles were ferromagnetic. Also, the saturation magnetization (MS), remanent magnetization (MR) and coercivity (MR) were observed to increase with decreasing temperature. The results of magnetic characterization showed that the magnetic properties of the HPMC stabilized Ni nanoparticles are quite different from those of the bared Ni nanoparticles. All the observed magnetic properties essentially reflected the very typical nanoparticle type nature. Consequently, the resulting Ni nanoparticles were found to be highly active and recyclable catalyst for Suzuki coupling reactions.

Effect of xanthan gum and guar gum on in situ gelling ophthalmic drug delivery system based on poloxamer-407.

The aim of this investigation was to develop a novel in situ gelling formulation based on poloxamer-407 (PM) for the sustained release of an ophthalmic drug. In an attempt to reduce the concentration of PM without compromising the in situ gelling capability and also to increase the drug release time, xanthan gum (XG) and guar gum (GG) were added into PM to develop different formulations. At concentrations of 18% and above, the PM was able to undergo sol-gel transition below body temperature. It was found that XG and GG at a weight ratio of 3:7 were able to convert PM solution into gel below body temperature at PM concentrations below 18%. Both the in vitro and in vivo studies indicated that the PM with an XG-GG combination had a better ability to retain the drug than PM itself. The results indicated that the developed in situ gelling formulations containing PM with XG-GG may be a better alternative than a conventional eye drop.

Synergistic effect of salt mixture on the gelation temperature and morphology of methylcellulose hydrogel.

Gelation temperature of methylcellulose (MC) can be altered by adding different additives. Pure MC showed sol-gel transition at 60°C. Sodium citrate and sodium tartrate were used alone and in combination to see the effect of individual salt and combination of salts on the gelation temperature of MC. The gelation temperature of all the binary and ternary combinations of MC and salts were measured with different methods such as test tube tilting method (TTM), UV-vis spectroscopy, viscometry, and by rheometer and also the morphology of gels were characterized with the help of environmental scanning electron microscopy (ESEM). It was observed that when 0.1 M sodium citrate (NaC) and 0.1 M sodium tartrate (NaT) were used separately, the gelation temperature of MC was reduced up to 44°C and 47°C respectively but when mixture of NaC and NaT (0.1 (M) NaC and 0.1 (M) (NaT)) were used the gelation temperature was further reduced to 36°C. It was clear from ESEM images that when NaC and NaT were used separately the formation of network was not distinguishable. But, well-connected network structure was observed when a mixture 0.1 M NaC and 0.1 M NaT was used.

Synthesis of methylcellulose-silver nanocomposite and investigation of mechanical and antimicrobial properties.

In this paper we reported preparation of methylcellulose-silver nanocomposite films by mixing of aqueous solution of methylcellulose with silver nitrate followed by casting. The silver nanoparticles were generated in methylcellulose matrix through reduction and stabilization by methylcellulose. The surface plasmon band at 412 nm indicated the formation of Ag nanoparticles. The MC-Ag nanocomposite films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR). The X-ray diffraction analysis of synthesized MC-Ag nanocomposite films revealed that metallic silver was present in face centered cubic crystal structure. Average crystallite size of silver nanocrystal was 22.7 nm. The FTIR peaks of as-synthesized MC-Ag nanocomposite fully designated the strong interaction between Ag nanoparticles and MC matrix. Nano-sized silver modified methylcellulose showed enhanced mechanical properties i.e. the introduction of Ag leading to both strengthening and toughening of MC matrix. The methylcellulose-silver nanocomposite films offered excellent antimicrobial activity against various microorganisms.

Effect of PVA on the gel temperature of MC and release kinetics of KT from MC based ophthalmic formulations.

The effect of molecular weight of poly(vinyl alcohol) (PVA) and sodium chloride on the gelation temperature of methylcellulose (MC) was studied with the objective to develop a MC based formulation for sustained delivery of ketorolac tromethamine a model ophthalmic drug. Pure MC showed sol-gel transition at 61.2 °C. In order to reduce the gelation temperature of MC and to increase the drug release time, PVA was used. Different techniques such as test tube tilting method, UV-vis spectroscopy, viscometry and rheometry were used to measure gelation temperature of all the binary combinations of MC and PVA. It was observed that the gelation temperature of MC was reduced with the addition of 4% PVA and also the extent of reduction of the gelation temperature of MC was dependent on the molecular weight of PVA. The strong interactions between MC and PVA molecules were established using Fourier transform infrared spectroscopy. To study the in vitro drug release properties of the MC-PVA binary combinations, 6% sodium chloride was used to reduce the gelation temperature further up to physiological temperature. It was observed that the drug release time increased from 5 to 8h with the increase of molecular weight of PVA from 9×10(3) to 1.3×10(5) and this was due to the higher viscosity, better gel strength and greater interactions between the drug and PVA molecules in case of PVA (1.3×10(5)) compared to PVA (9×10(3)). In order to have an idea about the nature of interactions between the functional moieties of the drug and the polymer unit of PVA, a theoretical study was carried out.