Polyvinyl Alcohol/polyvinyl Pyrrolidone Research Articles

Separable Microneedles for Synergistic Chemo-Photothermal Therapy against Superficial Skin Tumors.

It is extremely important to develop a minimally invasive and efficient approach for treatment of superficial skin tumors (SSTs). In this work, a near-infrared (NIR)-triggered transdermal therapeutic system based on two-stage separable microneedles (MNs) has been proposed for synergistic chemo-photothermal therapy against SSTs. Lauric acid and polycaprolactone as phase-change materials have been used to prepare the arrowheads of the two-stage separable MNs in which an anticancer drug (doxorubicin, DOX) and photothermal agent (indocyanine green, ICG) were embedded. The arrowheads are capped on the dissolvable support bases that consisted of poly(vinyl alcohol)/polyvinyl pyrrolidone (PVA/PVP). After inserting into skin tissue, the PVA/PVP support bases can be dissolved quickly owing to the absorption of the interstitial fluid, leading the arrowheads to be left in the skin tissue. Under NIR irradiation, the arrowheads embedded in the skin can be ablated because of the photothermal conversion of the ICG, resulting in liberation and penetration of the DOX from the MNs into the tumor tissue. A mouse model of melanoma tumor has been established to evaluate the synergistic effect of two-stage separable MN phototherapy and chemotherapy in the treatment of skin cancer.

Facilitating the conservation treatment of Eva Hesse\u2019s Addendum through practice-based research, including a comparative evaluation of novel cleaning systems

This paper describes the methodology and practice-based research underpinning the development of a successful cleaning strategy for Eva Hesse’s sculpture Addendum (1967, Tate Collection T02394). Research strands included: technical and art historical investigations to determine the materials and construction of the work of art and to define the aims of the conservation treatment; the production, soiling and accelerated ageing of mock-up samples using contemporary equivalent materials; and the systematic, iterative evaluation of soiling removal systems, which were further refined for appropriate use on the work of art. The comparative cleaning system evaluation was employed to determine options which offered optimal soiling removal efficacy and posed minimal risk to the work of art. Newly developed Nanorestore Gel® Peggy series (i.e. polyvinyl alcohol (PVA) and polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP)-based hydrogels), designed for the cleaning of modern and contemporary art, were evaluated with a range of other gels, emulsifiers and cosmetic sponges and assessed through a combination of empirical observation, microscopy and spectroscopic techniques. Promising options, combined with tailored aqueous phases derived from trials on mock-up samples, were then evaluated on discreet areas of the sculpture. After extensive testing, the top papier mâché section of Addendum was surface cleaned using an aqueous solution applied with cosmetic sponges, and the ropes were surface cleaned using a modified version of Nanorestore Gel® Peggy 5 (PVA/PVP) loaded with a tailored aqueous solution. The optimisation of this hydrogel, combined with the extensive supporting research, enabled the successful, low-risk, conservation treatment of Addendum for the first time since acquisition.

Influence of Gamma irradiation on the structural and optical characteristics of Li ion-doped PVA/PVP solid polymer electrolytes

Lithium ions-doped polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) films were prepared by solution casting technique and exposed to 100 kGy gamma radiation. The structural modifications in the samples before and after irradiation were studied using X-ray diffraction XRD and UV–Vis spectroscopy. The results indicated that absorbance $$ A\,(\lambda ) $$ and absorption index (k) increased, while semicrystalline nature of the blend decreased due to the addition of Li2SO4 and irradiation. The optical band gap $$ E_{\text{g}}^{\text{opt}} $$ of the composites showed significant decrease from 2.98 to 2.196 eV by adding Li2SO4 and from 2.83 to 2.08 eV after irradiation due to cross-linking. The Tauc’s relation indicated that allowed transitions are indirect for both irradiated and unirradiated samples. The Urbach energy ( $$ E_{\text{u}} $$ ) increased with increasing Li ion content and exposure to γ irradiation. The dependence of dielectric permittivity $$ \varepsilon_{1} $$ , dielectric loss $$ \varepsilon_{2} $$ and optical conductivity $$ \sigma_{opt} $$ on photon energy $$ h\nu $$ was also studied.

Spectroscopic and Discharge Studies on Graphene Oxide Doped PVA/PVP Blend Nanocomposite Polymer Films

Graphene oxide (GO) nanoparticles were synthesized by modified Hummers method. The synthesized GO nanoparticles were incorporated in polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend polymers for the preparation of nanocomposite polymer films by solution cast technique. Different characterizations such as XRD, UV–Vis and FTIR were carried-out on to the prepared nanocomposite polymer films. The thermal analysis of the films was studied by DSC. The morphology of PVA/PVP:GO polymer films confirms GO was exfoliated within the PVA/PVP matrix and also reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. From the conductivity studies the highest conductivity of PVA/PVP: GO (0.45: 0.3) was found to be 8.05 × 10–4 S/cm at room temperature. Solid state battery has been fabricated with the configuration of Mg+/(PVA/PVP:GO)/(I2 + C + electrolyte) and its cell parameters were calculated for a constant load of 100 kΩ.

Multistage thermal decomposition in films of cadmium chloride-doped PVA–PVP polymeric blend

Films of cadmium chloride (CdCl2) doped polyvinyl alcohol (PVA)–polyvinyl pyrrolidone (PVP) polymer blend have been studied using thermogravimetry (TG) and differential scanning calorimetry (DSC), for doping levels ranging from 0.0 mass% to 50.5 mass%. At high doping levels (beyond 10.2 mass%), TG scans of these films showed several stages of decomposition at temperatures beyond 100 °C, indicating that the incorporation of CdCl2 results in deterioration of PVA–PVP blend, on thermal activation. The presence of melting peaks, which is due to melting of crystalline regions in CdCl2-doped PVA–PVP blend samples and the occurrence of thermal decomposition, in different stages, is confirmed by DSC curves. There is a decrease in decomposition temperature of the doped PVA–PVP blend, with an increase in salt (CdCl2) concentration. Kinetic analysis has been performed using iso-conversional models, using Flynn–Wall–Ozawa (FWO) equation, Kissinger–Akahira–Sunose (KAS) equation and Kissinger relation at four different stages of thermal decomposition, for the 10.2 mass% CdCl2-doped PVA–PVP blend. The higher values of activation energy, Ea= 197.5, 196.0 and 175.3 kJ mol−1 obtained from FWO, KAS and Kissinger models reveal that CdCl2-doped PVA–PVP sample has more thermal stability when compared to the undoped PVA–PVP blend.

UV irradiation induced microstructural changes in CdCl2 doped PVA–PVP blend

Films of cadmium chloride (CdCl2) doped polyvinyl alcohol (PVA)–polyvinyl pyrrolidone (PVP) blend were irradiated with ultraviolet (UV) light, of wavelength 254 nm. Modification in band structure of the doped polymeric blend films has been studied using optical (UV–Visible) and fluorescence (photo-luminescence) spectral analysis. On exposure to UV radiation, the PVA–PVP samples doped with CdCl2 from 5.4 up to 12.1 wt% (doping level) get blackened, possibly due to carbonization. Microstructural modifications in these films caused by UV irradiation have been studied with the help of scanning electron microscope (SEM) images. The molecular chemical changes caused by UV irradiation on CdCl2 doped PVA–PVP blend has been studied using Fourier transform infrared (FTIR) and FT-Raman spectra of these films, after UV exposure for 30 and 180 min. The results are compared with those of un-doped PVA–PVP blend films, which have been exposed to UV irradiation for the same time interval.

Spectroscopic analysis of CdCl2 doped PVA–PVP blend films

The changes in molecular chemical structure of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), caused by doping PVA–PVP blend with cadmium chloride (CdCl2), have been studied using ultraviolet–visible (UV-Vis) spectroscopy, Fourier transform Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The formation of cadmium nano-structures and microstructures in CdCl2-doped PVA–PVP blend has been visualized using scanning electron microscopy, in the range of doping levels varying from 0.5 up to 10.2 wt% (doping level in weight percentage). The incorporation of dopant in PVA–PVP blend is confirmed using energy dispersive X-ray spectroscopy. The optical absorbance (UV-Vis) spectra of PVA–PVP blend films doped with CdCl2 from 0.5 up to 2.2 wt%, showed a prominent absorption hump with peak at the wavelength 370 nm, in addition to other intermediate energy bands caused by the interactions of CdCl2 with molecules of PVA and PVP. The photo-luminescence (emission and fluorescence) spectra show significant quenching of fluorescence in CdCl2-doped PVA–PVP blend films. Analysis of FTIR and Raman spectra suggest the possible modes of interaction of cadmium ions (Cd2+) and chlorine ions (Cl−) with reactive functional groups (C–N, hydroxyl and carbonyl groups) of polymeric molecules in the blend. A reaction scheme for interaction of CdCl2 with PVA–PVP blend is proposed, on the basis of spectroscopic studies on these films.

Magnesium ion conducting polyvinyl alcohol–polyvinyl pyrrolidone-based blend polymer electrolyte

Structural, thermal, electrical and electrochemical behaviour of polymer blend electrolytes comprising polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) as host polymers and Mg(ClO4)2 as dopant salt have been investigated. The changes in the structural properties on the incorporation of dopant in the blends were investigated by XRD and FTIR analyses. Thermal properties of pure PVA–PVP blend and their complexes were examined by DSC to measure how the thermal transitions of the prepared films were affected by different concentration of Mg(ClO4)2. The ionic conductivity and dielectric behaviour were explored using A.C. impedance spectroscopy. The trend of ionic conductivity increases almost proportionally to the content of magnesium salt and can be related to an increase of amorphous phase at high level of dopant salt. The electrochemical stability of the optimum conducting blend polymer electrolyte is found to be ∼3.5 V. The Mg2+ transference number for the sample with optimized conductivity was found to be 0.31.

Swelling, mechanical and friction properties of PVA/PVP hydrogels after swelling in osmotic pressure solution

The potential of polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) hydrogels as articular cartilage replacements was in vitro evaluated by using a macromolecule–based solution to mimic the osmotic environment of cartilage tissue. The effects of osmotic pressure solution on the morphology, crystallinity, swelling, mechanical and friction properties of PVA/PVP hydrogels were investigated by swelling them in non–osmotic and osmotic pressure solutions. The results demonstrated that swelling ratio and equilibrium water content were greatly reduced by swelling in osmotic solution, and the swelling process was found to present pseudo–Fickian diffusion character. The crystallization degree of hydrogels after swelling in osmotic solution increased more significantly when it compared with that in non–osmotic solution. After swelling in osmotic solution for 28days, the compressive tangent modulus and storage modulus of hydrogels were significantly increased, and the low friction coefficient was reduced. However, after swelling in the non–osmotic solution, the compressive tangent modulus and friction coefficient of hydrogels were comparable with those of as–prepared hydrogels. The better material properties of hydrogels in vivo than in vitro evaluation demonstrated their potential application in cartilage replacement.

Electrospun polyvinyl alcohol-polyvinyl pyrrolidone nanofibrous membranes for interactive wound dressing application

Cross-linked polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) composite nanofibrous membranes have been prepared by electrospinning. Mechanical properties of the membranes improved significantly with PVP addition. PVP improved hydrophilicity and sustainable degradation of the membranes. Biocompatibility of the membranes was assessed by in vitro culture of native skin cells (L929 fibroblast and HaCaT keratinocytes). Tests showed sustained release of the antibiotic ciprofloxacin hydrochloride monohydrate by the membranes. Further, zone of inhibition study against Staphylococcus aureus growth demonstrated protective action against external pathogenic microbes. These studies show these simple PVA–PVP nanofibrous membranes are promising interactive antibiotic-eluting wound dressing materials.

A redox‐mediator‐doped gel polymer electrolyte applied in quasi‐solid‐state supercapacitors

ABSTRACTMethylene blue (MB) redox mediator was introduced into polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend host to prepare a gel polymer electrolyte (PVA‐PVP‐H2SO4‐MB) for a quasi‐solid‐state supercapacitor. The electrochemical properties of the supercapacitor with the prepared gel polymer electrolyte were evaluated by cyclic voltammetry, galvanostatic charge–discharge, electrochemical impedance spectroscopy, and self‐discharge measurements. With the addition of MB mediator, the ionic conductivity of gel polymer electrolyte increased by 56% up to 36.3 mS·cm−1, and the series resistance reduced, because of the more efficient ionic conduction and higher charge transfer rate, respectively. The electrode specific capacitance of the supercapacitor with PVA‐PVP‐H2SO4‐MB electrolyte is 328 F·g−1, increasing by 164% compared to that of MB‐undoped system at the same current density of 1 A·g−1. Meanwhile, the energy density of the supercapacitor increases from 3.2 to 10.3 Wh·kg−1. The quasi‐solid‐state supercapacitor showed excellent cyclability over 2000 charge/discharge cycles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39784.

The surface lubricative properties of PVA/PVP hydrogels treated with radiation used as artificial cartilage

In this work, poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogels were prepared by cycled freezing and thawing process, and subsequently with irradiation crosslink processing. The exterior micro-structure and frictional coefficients of compound hydrogels with and without radiation treatment were compared. The changes of surface lubricative properties were observed in physiological condition in vitro. Without radiation treatment, the friction coefficient of PVA/PVP hydrogels increased rapidly in water because of the solubility and exudation of PVP, which could induce the decline of their lubricative action. While after radiation treatment, the surface lubricative properties of PVA/PVP hydrogels in water were improved and stable due to the crosslink between PVA and PVP.

Biodegradability, antimicrobial activity and properties of PVA/PVP hydrogels prepared by γ-irradiation

Polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) hydrogel has been prepared by using γ-irradiation technique. In the present study the conclusion on miscibility of PVA/PVP blends, confirmed qualitatively and quantitatively by using Fourier transform infrared spectroscopy and differential scanning calorimetry, respectively. PVA and PVP are found to form a thermodynamically miscible pair. The physical properties such as gel fraction and water absorption performance of the prepared hydrogels were measured, it was found that the gel fraction increases with increasing irradiation dose while the swelling of PVA/PVP blended hydrogels nearly tends to increase with increasing PVP content and reduced with enhanced irradiation doses. The hydrogel pore structure of various PVA/PVP compositions were tested with SEM. Ability of PVA/PVP hydrogels to absorb and release antimicrobial compounds was tested using amoxicillin as an antibacterial and ketoconazole as an antifungal. Antimicrobial activity of PVA/PVP hydrogels was examined using four bacteria, and four fungi. No antibacterial or antifungal activities of non-loaded PVA/PVP of various compositions were detected while the loading ones found to have antimicrobial activity. Results showed resistance of Pseudomonas aeruginosa and Candida albicans to PVA/PVP, while Bacillus subtilis was very sensitive. Biodegradation of PVA/PVP hydrogels was investigated by burial method in two types of local soils (clay and sandy soils). The highest degradation rate was found to be achieved using clay soil. Also, effect of irradiation dose on its biodegradability was tested. The results showed that the radiation prepared PVA/PVP hydrogels can be use as biomaterials.

Mineralization of radiation-crosslinked polyvinyl alcohol/polyvinyl pyrrolidone hydrogels

A study of the calcification of the polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) hydrogels during their exposure to a calcium chloride solution or a simulated body fluid has been carried out. On the basis of the experiments, using a two-compartment permeation cell, the diffusion of calcium ions and their subsequent deposition in the hydrogels were elucidated. Steady-batch experiments were also performed to further elaborate the deposition pattern and the types of calcium deposits. It was demonstrated that Fick's second law of diffusion can describe the diffusion of calcium ions through PVA/PVP hydrogels at 310 K. The diffusion coefficient was determined to be (4.4+/-0.1)x10(-10) m2/s and the partition coefficient for the hydrogels was 0.06. Formation of calcium deposits was noticed taking place both on the surface and inside the hydrogels. The deposits formed on the surface have flake morphology, while the deposits inside the hydrogels are more like globular aggregates. Both types of deposits have been characterized as being comprised calcium and hydroxyl ion deficient apatites with chloride ions the most likely substituting species at the hydroxyl sites.

Interfacial behaviour of binary polymer mixtures I. Effect of uncharged polymers and of their mixtures on the stability of silver iodide sol

The adsorption from aqueous solutions of methylcellulose (MC), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), adsorption of their binary mixtures on silver iodide sol, and the effect of these polymers and polymer mixtures on the stability of silver iodide sol, have been studied. All these polymers show high affinity-type adsorption isotherms and the adsorption is only partially reversible upon dilution. The order of preferential adsorption for the polymers is as follows; PVP &>; PVA &>; MC. The weakly adsorbed polymers, at high surface coverage, can be displaced from the interface by the preferentially adsorbed polymers. Synergism has been found in the flocculating effect of the MC—PVP and the PVA—PVP mixtures. At the onset of the stabilizing region, some increase in the effectiveness of the above two mixtures has also been observed. Non-additivity can be observed when the difference in the segment affinity of the two polymers for the particle surfaces is high enough. When synergism occurs, the conformation of the weakly adsorbed polymer appears to be distorted at the solid/liquid interface by the preferentially absorbed polymer. This “irregularly” extended polymer conformation is especially favourable for bridging flocculation.

Interfacial behaviour of binary polymer mixturesI. Effect of uncharged polymers and of their mixtures on the stability of silver iodide sol

The adsorption from aqueous solutions of methylcellulose (MC), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), adsorption of their binary mixtures on silver iodide sol, and the effect of these polymers and polymer mixtures on the stability of silver iodide sol, have been studied. All these polymers show high affinity-type adsorption isotherms and the adsorption is only partially reversible upon dilution. The order of preferential adsorption for the polymers is as follows; PVP &>; PVA &>; MC. The weakly adsorbed polymers, at high surface coverage, can be displaced from the interface by the preferentially adsorbed polymers. Synergism has been found in the flocculating effect of the MC—PVP and the PVA—PVP mixtures. At the onset of the stabilizing region, some increase in the effectiveness of the above two mixtures has also been observed. Non-additivity can be observed when the difference in the segment affinity of the two polymers for the particle surfaces is high enough. When synergism occurs, the conformation of the weakly adsorbed polymer appears to be distorted at the solid/liquid interface by the preferentially absorbed polymer. This “irregularly” extended polymer conformation is especially favourable for bridging flocculation.