Increasing PVP Concentration Research Articles

Localized surface plasmon resonance properties of green synthesized silver nanoparticles

Silver (Ag) and silver-polyvinylpyrrolidone (Ag-PVP) nanoparticles (NPs) were effectively synthesized by a green synthesis method using Moringa oleifera with various PVP concentrations (1.70, 2.55 and 4.25 ppm). The localized surface plasmon resonance (LSPR) behavior of the Ag-PVP NPs was investigated using the Kretschmann configuration with a layer arrangement of prism/Au/Ag-PVP NPs/air. The Ag NPs were spherical with a face-centered cubic crystal structure and a dispersed particle size of 22 nm. The size of the NPs decreased to 20, 19 and 15 nm with increasing PVP concentrations. PVP plays a vital role in crystallite size regulation; the higher the concentration of PVP, the narrower the particle size distribution. The UV–visibleabsorption spectra showed an LSPR band at 326 nm which blue-shifted to 325, 323 and 321 nm as the PVP concentration increased. This is because the size of the NPs decreased with increasing PVP concentration. Fourier-transform infrared spectra verified the intermolecular interaction between PVP and the Ag NPs, as indicated by the peaks at 3,326–3,330 cm −1, corresponding to the hydroxyl group, and the sharp and strong peaks at 1,633–1,638 cm −1, corresponding to the carbonyl group. PVP compounds containing nitrogen (N) and oxygen (O) atoms were coordinated with Ag+, forming a closed layer on the particle surface, which inhibited agglomeration and shifted the wavelength to a lower value. The results showed that the LSPR angle shifted toward a larger incidence angle due to the Ag-PVP NPs. Increasing the PVP concentration caused a large shift in the LSPR angle owing to the change in the size and thickness of the PVP layer of NPs, which changed the dielectric constant of the NPs. This proves that the use of PVP can help control the microstructural and LSPR properties of green synthesized Ag-PVP NPs and potentially optimize the performance of SPR-based sensors in the future.

Polyvinylpyrrolidone Loaded-MnZnFe2O4 Magnetic Nanocomposites Induce Apoptosis in Cancer Cells Through Mitochondrial Damage and P53 Pathway

MnZnFe2O4 ferrite was successfully synthesized using metallic chlorides and polyvinylpyrolidone, by Co-precipitate method. Deferent concentrations of PVP (0.1, 0.3, 0.5, 0.7, and 0.9) wt%, were used as capping agent to stabilize the particles and prevent them from agglomeration. The PVP content had a vital influence on enhancing the properties of the ferrite nanoparticles. From X-ray data the degree of crystallinity and the Lattice constants (a) of the nanoparticles increased from (8.92 nm) and (8.344 A) to (19.94 nm) and (8.395 A) respectively with increasing PVP concentrations. The morphology and average particle size of the MnZn ferrite nanoparticles were evaluated by scanning electron microscopy (SEM), the values were in a good agreement with the XRD results. Fourier transform infrared spectroscopy (FT-IR) confirmed the cubic structure with octahedral and tetrahedral, also indicated the formation of bond between PVP and surface of metallic hydroxide of ferrite nanoparticles. Vibrating sample magnetometer (VSM) analysis was performed for all samples at room temperature, results showed that the specimens exhibited a paramagnetic behavior in the absence of PVP while in the presence of PVP they have super paramagnetic characteristics. The values of saturation magnetization (Ms) (1.78–17.67 emu/g), remnant magnetization (Mr) (0.0022–0.0696 emu/g) also increased with increasing pvp concentration. Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites were used it alone or as a combination therapy with NIR laser, and alternating magnetic field (AMF) as anti-proliferative agent against breast cancer cell lines AMJ-13, MCF-7,and ovarian cancer cell line SKOV-3 as well as against normal cell line HBL. While, its capability to induce apoptosis was detected using different techniques which is acridine orange/ethidium bromide (AO/EtBr) staining and mitochondrial membrane potential (MMP), and flow cytometry assay membrane potential (MMP). q-PCR was used to investigate the changes in the expression of P53 gene. The influence of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites in viability of breast and ovarian cancer cells alone or when they used as a combination therapy with laser photo-thermal therapy and alternating magnetic field (AMF) was also tested using MTT assay. Our results in the present study demonstrated that the inhibition activity of Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites against treated cancer cell lines increased when Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites used with NIR laser, while highly increased cytotoxic activities were observed after exposure of Polyvinylpyrrolidone loaded-MnZnFe2O4 nanocomposites to induction heating with AMF. Treated cancer cells with polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites significantly increased ROS synthesis, with subsequent reduction of the MMP. The results of the current study show that tested compounds suppressed cancers cells’ proliferation and has a growth inhibitory effect on different cancer cells, resulting in apoptosis as a novel pathway that involves mitochondrial damage mechanism via activated P53. Taken together the present data suggest that the Polyvinylpyrrolidone loaded-MnZnFe2O4 magnetic nanocomposites could be promising therapy protocol for cancer cells.

Improved microfiltration and bacteria removal performance of polyethersulfone membranes prepared by modified vapor‐induced phase separation

Polyethersulfone (PES) microfiltration membranes were fabricated by a combined vapor‐induced phase separation and wet phase separation method. The effect of different non‐solvent additives in casting solution, ie, acetone, diethylene glycol, and triethylene glycol (TEG) was investigated on the membrane morphology and performance. Scanning electron microscopy images showed that the membrane containing TEG additive had a skinless symmetric structure with well interconnected pores. The permeability of the PES/PVP/TEG membranes increased by decreasing PES and TEG and increasing PVP concentration. Bacteria removal performance of the prepared membranes was investigated by the filtration of E. coli suspension. The membrane made from casting solution containing 15 wt.% PES, 16 wt.% PVP, and 20wt.% TEG showed a pure water flux of ~ 5370 L/m2 h at low transmembrane pressure of 10 psi and 100% bacteria removal efficiency. The results of in vitro cytotoxicity test and cell viability assay showed non‐toxic nature of the prepared membranes.

Jelly containing composite based on α-glucosyl stevia and polyvinylpyrrolidone: Improved dissolution property of curcumin

Curcumin (CUR) solutions prepared with α-glucosyl stevia (Stevia-G) and polyvinylpyrrolidone K-30 (PVP) by evaporation method showed 11,000-fold higher solubility compared to CUR alone. Tri-component formulations of CUR/Stevia-G/PVP in aqueous solution showed improved CUR stability for precipitation-triggering conditions of CUR, such as aqueous dilution and temperature changes. Fluorescence study with CUR and pyrene indicated that Stevia-G/PVP mixed solutions produce a more hydrophilic microenvironment around their molecules with increasing PVP concentration compared to Stevia-G solution alone. These results suggested the composite formation associated with the adsorption of the aggregated structure of Stevia-G onto PVP molecules. Jelly formulations were prepared with κ-carrageenan, and jelly formulations containing nanocomposites formed by CUR/Stevia-G/PVP obviously enhanced the dissolution properties of CUR compared to CUR powder. This result indicated that the composite formed by CUR/Stevia-G/PVP could be maintained even after the preparation of jelly and release into a dissolution media. Production of jelly formulations using Stevia-G and PVP are a promising way to improve the dissolution properties of CUR.

Frontal polymerization and characterization of interpenetrating polymer networks composed of poly(N-isopropylacrylamide) and polyvinylpyrrolidone

The synthesis of semi-interpenetrating polymer networks (IPN) of the hydrogel, poly(N-isopropylacrylamide)/polyvinylpyrrolidone (PNIPAm/PVP), by frontal polymerization, was carried out. The frontal parameters were studied, and the products were characterized. It was observed that the incorporation of PVP into PNIPAm shortened the response time, without changing the lower critical solution temperature (LCST) of PNIPAm. Furthermore, the compressive strength of IPN hydrogels increased with increase in PVP concentration. Also, the drug release behaviors of IPN hydrogels were explored using the model drug aspirin. It was demonstrated that the drug loading capacity of the hydrogels increased from 245 to 422 mg/g by increasing PVP concentration from 0 to 20%. The drug release data suggested that the drug could be released in an improved and controlled manner by the IPN hydrogels, without the loss of their intelligent properties. All these results indicate that IPNs based on PNIPAm/PVP hydrogels can be finely tuned by frontal polymerization and can be used as drug delivery systems.

The formation of α-phase SnS nanorods by PVP assisted polyol synthesis: Phase stability, micro structure, thermal stability and defects induced energy band transitions

We report the formation of single phase of SnS nanostructure through PVP assisted polyol synthesis by varying the source concentration ratio (Sn:S) from 1:1M to 1:12M. The effect of PVP concentration and reaction medium towards the preparation of SnS nanostructure is systematically studied through confocal Raman spectrometer, X-ray diffraction, thermogravimetry analysis, scanning electron microscope, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–Vis–NIR absorption and fluorescence spectrophotometers. The surface morphology of SnS nanostructure changes from nanorods to spherical shape with increasing PVP concentration from 0.15M to 0.5M. Raman analysis corroborates that Raman active modes of different phases of Sn-S are highly active when Raman excitation energy is slightly greater than the energy band gap of the material. The presence of intrinsic defects and large number of grain boundaries resulted in an improved thermal stability of 20 °C during the phase transition of α-SnS. Band gap calculation from tauc plot showed the direct band gap of 1.5 eV which is attributed to the single phase of SnS, could directly meet the requirement of an absorber layer in thin film solar cells. Finally, we proposed an energy band diagram for as synthesized single phase SnS nanostructure based on the experimental results obtained from optical studies showing the energy transitions attributed to band edge transition and also due to the presence of intrinsic defects.

Growth of Ultralong Ag Nanowires by Electroless Deposition in Hot Ethylene Glycol for Flexible Transparent Conducting Electrodes

High aspect ratio silver (Ag) nanowires with an average length of 25.4 μm and diameter of 102.8 nm were successfully prepared by electroless deposition in hot ethylene glycol (160°C) for 1 h in the presence of PVP. It was found that both PVP concentration and molecular weight significantly influence the morphology and yield of Ag nanowires in solution. Using PVP MW = 55,000, addition of lower amounts of PVP led to formation of large irregularly shaped Ag particles together with a few rod-like structures. Increasing PVP concentration generally resulted in longer and thinner Ag nanowires. On the other hand, low molecular weight PVP produced spherical Ag particles even at high PVP concentration. Ag nanowire flexible transparent conducting electrodes attained a sheet resistance of about 92.5 Ω/sq at an optical transmittance of about 79.6% without any heat treatment. In addition, no significant change in optical and electrical properties was observed after several cycles of bending and adhesion test.

Promotion of Copper Corrosion Inhibition by Application of a Square Wave Potential Regime to Copper Specimens in Polyvinylpyrrolidone Solutions

Enhancement of corrosion inhibition of copper by polyvinylpyr r olidone (PVP) upon application of a square wave potential regime to copper specimens was investigated. The results indicated a marked decrease of copper corrosion rate upon application of a square wave to copper specimens in PVP – containing solutions. The inhibition enhancement was found to incr ease when increasing PVP concentration, and with a larger time of exposure with application of the square wave potential regime. A 500 Hz frequency was the optimal frequency for promotion of inhibition by PVP. SEM micrographs revealed that application of t he square wave converted the dendritic coverage of PVP to a more uniform layer of PVP at copper surface. The enhancement of corrosion inhibition by application of the square wave might be explained on basis of the enhanced adsorption of PVP onto copper sur face by application of the square wave potential regime. Application of square wave potential regime apparently influences the PVP adsorption coverage at the copper surface .

Influence of the Polyvinyl Pyrrolidone Concentration on Particle Size and Dispersion of ZnS Nanoparticles Synthesized by Microwave Irradiation

Zinc sulfide semiconductor nanoparticles were synthesized in an aqueous solution of polyvinyl pyrrolidone via a simple microwave irradiation method. The effect of the polymer concentration and the type of sulfur source on the particle size and dispersion of the final ZnS nanoparticle product was carefully examined. Microwave heating generally occurs by two main mechanisms: dipolar polarization of water and ionic conduction of precursors. The introduction of the polymer affects the heating rate by restriction of the rotational motion of dipole molecules and immobilization of ions. Consequently, our results show that the presence of the polymer strongly affects the nucleation and growth rates of the ZnS nanoparticles and therefore determines the average particle size and the dispersion. Moreover, we found that PVP adsorbed on the surface of the ZnS nanoparticles by interaction of the C–N and C=O with the nanoparticle’s surface, thereby affording protection from agglomeration by steric hindrance. Generally, with increasing PVP concentration, mono-dispersed colloidal solutions were obtained and at the optimal PVP concentration (5%), sufficiently small size and narrow size distributions were obtained from both sodium sulfide and thioacetamide sulfur sources. Finally, the sulfur source directly influences the reaction mechanism and the final particle morphology, as well as the average size.

Modulating Up-Energy Transfer and Violet-Blue Light Emission in Gold Nanoparticles with Surface Adsorption of Poly(vinyl pyrrolidone) Molecules

Au-nanoparticles (Au-NPs) with a polymer surface layer of poly(vinyl pyrrolidone) (PVP) exhibit a combined Stoke emission of an intense violet-blue band 300−550 nm in a coupled polariton−plasmon structure. Nascent Au-NPs, mostly polygonal shapes (10−45 nm widths), cobridge an adhesive PVP surface layer (2−3 nm thickness) that congregates the Au-surface-plasmons (SPs) in a localized state, showing a marked blue shift of Au-SPs band 450 nm from 530 nm in bared Au-NPs. In an up-energy transfer, the SPs recombine coexcited n → nπ* (PVP) photons (∼412 nm) and ultimately emit two 260 and 345 nm anti-Stoke bands. When increasing PVP concentration to a critical value of 11.0 g L−1 (0.1 mol L−1) in a rheo-optical Au-PVP nanofluid, the first band grows in intensity markedly at the expense of the other band like the Stoke bands. Dielectric field and viscosity of the fluid mediate the Au ← PVP energy transfer useful for biological and optical probes.

Segmental Relaxation of Hydrophilic Poly(vinylpyrrolidone) in Chloroform Studied by Broadband Dielectric Spectroscopy

Dielectric relaxation caused by the segmental motion of poly(vinylpyrrolidone) (PVP) was studied in chloroform solutions with 5−40 wt % PVP at temperatures between 298 and 210 K above the melting temperature of chloroform (210 K) to obtain information on the dynamics of hydrophilic polymer. The asymmetric broadening of the loss peak and the fragility, i.e., the degree of deviation from the Arrhenius temperature dependence of relaxation time, increase with increasing PVP concentration. Both are due to increase in cooperativity of the segmental motion of PVP. The temperature-independent shape of the loss peak at a fixed concentration satisfies the time−temperature superposition and can be interpreted to be due to the small concentration fluctuation in the PVP/chloroform solutions. The repulsive force between PVP chains is expected to make the mixture homogeneous in chloroform, which is a good solvent of PVP.

Controlling Size and Distribution for Nano-sized Polystyrene Spheres

Highly monodisperse polystyrene (PS) nanospheres were fabricated by surfactant-free emulsion polymerization in water using styrene, 2,2'-azobis(2-methyl propionamidine) dihydrochloride (AIBA), and poly(vinyl pyrrolidone) (PVP). The size and distribution of the PS nanospheres were systematically investigated in terms of initiator concentration, stabilizer concentration, reaction temperature, reaction time, and reactant concentration. With increasing AIBA initiator concentration, PS particle sizes are raised proportionally, and can be controlled from 120 to 380 nm. Particle sizes were reduced with increasing PVP concentration. This decrease occurs because a high PVP concentration leads to a large number of primary nuclei in the early stage of polymerization. When the reaction temperature increased, the sizes of the PS particles decrease slightly. The particles grew quickly during the initial reaction stage (1-3 h) and the growth rate became steady-state after 6 h. The PS sizes approximately doubled when the reactant (styrene, PVP, azo-initiator) concentrations were increased by a factor of eight.

Preparation of Polyvinyl Pyrrolidone-Based Hydrogels by Radiation-Induced Crosslinking with Potential Application as Wound Dressing

Polyvinyl pyrrolidone/polyethylene glycol hydrogels (PVP/PEG) and PVP/PEG/Starch were prepared by irradiating the mixtures of aqueous solutions of PVP, PEG and starch with electron beam at different doses. Their properties were evaluated to identify their usability in wound dressing applications. The physical properties of the prepared hydrogels, such as gel content, swelling, water content and degree of water evaporation with varying composition and irradiation dose were examined to evaluate the usefulness of the hydrogels for wound dressing. The gel content increases with increasing PVP concentration due to increased crosslink density, and decreases with increasing the PEG concentration. PEG seems to act not only as plasticizer but also to modify the gel properties as gelation% and maximum swelling. Mechanical experiments were conducted for both PVP/PEG and PVP/PEG/Starch. The adding of PEG and starch to PVP significantly improves elongation and tensile strength of prepared hydrogels, respectively. The crystallinity of both prepared hydrogels was investigated with varying their components, XRD studies indicated that the crystallinity in the gel was mainly due to PVP and mainly decreased with enhanced starch content. The prepared hydrogels had sufficient strength to be used as wound dressing and could be considered as a good barrier against microbes.

Molecular and Thermodynamic Aspects of Solubility Advantage from Solid Dispersions

The solubility behavior of solid dispersions of two drugs with similar structures was studied. Valdecoxib (VLB) and etoricoxib (ETB) were used as model drugs, and their solid dispersions were prepared with 1, 2, 5, 10, 15, and 20% w/w poly(vinylpyrrolidone) (PVP) by the quench cooling method. The interactions between the drug and polymer molecules were studied by Fourier transform infrared spectroscopy (FT-IR). The thermodynamic aspects of solubility behavior were studied by plotting van't Hoff plots. Both the drugs showed significant differences in their solubility behavior. In the case of VLB, solubility was found to increase significantly with increasing PVP concentration. ETB however did not show any significant solubility enhancement and was found to have decreased solubility at high PVP concentrations. H-bonding interactions were established between VLB and PVP molecules, while none were observed in ETB-PVP dispersions. Solution thermodynamics of amorphous and crystalline forms of both the drugs were studied by van't Hoff plots. The results obtained showed very high negative value of Gibbs free energy for VLB as compared to ETB, thus demonstrating high spontaneity of VLB solubilization. Entropy of amorphous VLB was found to be highly favorable, while being slightly unfavorable for ETB. From this study H-bonding interactions were found to play a major role in dictating the solubility behavior of these drugs from solid dispersions.

Broadband Dielectric Study of Dynamics of Polymer and Solvent in Poly(vinyl pyrrolidone)/Normal Alcohol Mixtures

Broadband dielectric measurements of poly(vinyl pyrrolidone) (PVP)-monohydroxyl alcohol mixtures of various normal alcohols with the number of carbon atoms per molecule ranging from 1 to 9 were made in the frequency range of 20 Hz to 20 GHz at 25 degrees C. Two relaxation processes due to the reorientation of dipoles on the PVP and alcohol molecules were observed. The relaxation process at frequencies higher than 100 MHz is the primary process of alcohols, and that at frequencies lower than 10 MHz is attributed to the local chain motion of PVP. For mixtures of alcohol molecules that are smaller than propanol, the relaxation time of the alcohol increases with increasing PVP concentration, whereas for mixtures of alcohol molecules larger than butanol, the relaxation time of the alcohol decreases with increasing PVP concentration. The increase in the density of hydrogen-bonding sites upon the addition of PVP reduces the relaxation time of alcohol in the mixture, and vice versa. The relaxation time of the local chain motion of PVP increases with PVP concentration and solvent viscosity. Different time scales of the molecular motions of polymer and solvent coexist in homogeneous mixtures with hydrogen-bonded polar solvent and polymer.

Production of hydrogel wound dressings using gamma radiation

Hydrogel wound dressings have been prepared using the gamma rays irradiation technique. The dressings are composed of poly(vinyl pyrrolidone) (PVP), poly(ethylene glycol) (PEG) and agar. The influence of some process parameters on the properties of the dressings has been investigated as: the gel fraction, maximum swelling, swelling kinetics, and mechanical properties. The gel fraction increases with increasing PVP concentration due to increased crosslink density, and decreases with increasing the PEG concentration. PEG seems to act not only as plasticizer but also to modify the gel properties as gelation% and maximum swelling. The prepared hydrogels dressings could be considered as a good barrier against microbes.