Polyvinyl Alcohol Coatings Research Articles

Nanoparticle penetration of human cervicovaginal mucus: the effect of polyvinyl alcohol.

Therapeutic nanoparticles must rapidly penetrate the mucus secretions lining the surfaces of the respiratory, gastrointestinal and cervicovaginal tracts to efficiently reach the underlying tissues. Whereas most polymeric nanoparticles are highly mucoadhesive, we previously discovered that a dense layer of low MW polyethylene glycol (PEG) conferred a sufficiently hydrophilic and uncharged surface to effectively minimize mucin-nanoparticle adhesive interactions, allowing well-coated particles to rapidly diffuse through human mucus. Here, we sought to investigate the influence of surface coating by polyvinyl alcohol (PVA), a relatively hydrophilic and uncharged polymer routinely used as a surfactant to formulate drug carriers, on the transport of nanoparticles in fresh human cervicovaginal mucus. We found that PVA-coated polystyrene (PS) particles were immobilized, with speeds at least 4000-fold lower in mucus than in water, regardless of the PVA molecular weight or incubation concentration tested. Nanoparticles composed of poly(lactide-co-glycolide) (PLGA) or diblock copolymers of PEG-PLGA were similarly immobilized when coated with PVA (slowed 29,000- and 2500-fold, respectively). PVA coatings could not be adequately removed upon washing, and the residual PVA prevented sufficient coating with Pluronic F127 capable of reducing particle mucoadhesion. In contrast to PVA-coated particles, the similar sized PEG-coated formulations were slowed only ~6- to 10-fold in mucus compared to in water. Our results suggest that incorporating PVA in the particle formulation process may lead to the formation of mucoadhesive particles for many nanoparticulate systems. Thus, alternative methods for particle formulation, based on novel surfactants or changes in the formulation process, should be identified and developed in order to produce mucus-penetrating particles for mucosal applications.

Application and Evaluation of the Performance of Poly (Vinyl Alcohol) and its Blend with Nitrocelulose in Leather Top Coating

A 5% aqueous solution of polyvinyl alcohol (PVA) (m.wt. 125, 000), nitrocellulose and PVA/nitrocellulose blend were applied as a topcoat on dyed goatskin leather. The FT-IR spectroscopy of the cast polymer films indicated that each of the films in dry state consist of only pure polymer. The microscopic and physical characteristics of the coatings were also determined. The PVA coatings were found to have a glossy appearance, smooth handle and good extensibility, with excellent rubbing fastness and light fastness properties. However, the coatings have only a moderate adhesion of finish and have poor heat fastness and flexing endurance properties. The properties were found to improve when PVA was used in blend with nitrocellulose emulsion. The nitrocellulose coatings were, however, found to exhibit an almost all round superior coating property.

Electrospinning of Porphyrin/Polyvinyl Alcohol (PVA) Nanofibers and Their Acid Vapor Sensing Capability

Fluorescing 5,10,15,20-terakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP)-embedded and -coated polyvinyl alcohol (PVA) nanofibers were fabricated by using the electrospinning technique. To improve nonpolar solvent solubility of TMPyP/PVA nanofibers, tetraethyl orthosilicate (TEOS) was used as a cross-linking agent. UV-vis spectroscopy showed a strong Q band and two relatively weak Soret bands from the TMPyP/PVA nanofibers, and revealed that the TMPyP molecules were homogeneously loaded to the fibers. Scanning electron microscopy revealed that the electrospun nanofibers had ultrafine structures with an average diameter of ca. 250 nm. X-ray photoelectron spectroscopy confirmed the compositional structure of TMPyP/PVA/TEOS nanofibers and revealed the relative coverage of TMPyP molecules on the surface of TMPyP-embedded and TMPyP-coated PVA/TEOS fibers. For the comparison of the acid vapor sensitivity, TMPyP-embedded PVA/TEOS films, and TMPyP-embedded PVA/TEOS fibers, TMPyP-coated PVA/TEOS fibers were exposed to 1N nitric-acid vapor for 20-60 seconds. Fluorescence microscopy revealed that TMPyP-coated PVA/TEOS nanofibers exhibited better acid-sensing capability than TMPyP-embedded PVA/TEOS nanofibers and films.

Whitening of polyvinyl alcohol used as restoration material for Shohekiga

Polyvinyl alcohol (PVA) has been used to prevent flaking of paint pigments on traditional Japanese Shohekiga painted screens and panels. However, over time these PVA coatings whiten. To date, the mechanism of this whitening has not been studied from the point of view of polymer degradation. In this study, a piece of whitened PVA was obtained from a painted wooden panel. The PVA whitening mechanism was studied in this piece using scanning electron microscopy (SEM) and functional group analysis by Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). SEM showed that the surface of the whitened PVA thin film was irregular and rugged, and many micrometer-sized cracks were observed. This suggests that efficient scattering of all visible light from the cracks causes whitening. FT-IR and XPS measurements revealed that inter- and intra-chain dehydration and chemical crosslinking (C–O ether linkage) occur on the surface of the whitened PVA. Polyvinyl alcohol (PVA), which has been used to prevent flaking of paint pigments on traditional Japanese Shohekiga, became white and we investigated its phenomenon. The surface of whitened PVA was irregular and rugged, and many micrometer size cracks were observed. This suggests that efficient scattering of all visible region light from the cracks causes whitening. Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy measurements revealed that interchain dehydration and chemical crosslinking (C–O ether linkage) occurred on the surface of whitened PVA.

Magnetic microrheometer for in situ characterization of coating viscosity

A magnetic microrheometer has been designed to characterize the local viscosity of liquid-applied coatings in situ during solidification. The apparatus includes NdFeB magnets mounted on computer-controlled micropositioners for the manipulation of ∼1 μm diameter superparamagnetic particles in the coating. Magnetic field gradients at 20-70 T/m are generated by changing magnet size and the gap distance between the magnets. A specimen stage located between two magnets is outfitted with a heater and channels to control process conditions (temperature and air flow), and a digital optical microscope lens above the stage is used to monitor the probe particle position. Validation studies with glycerol and polyimide precursor solution showed that microrheometry results match traditional bulk rheometry within an error of 5%. The viscosities of polyvinyl alcohol (PVA) solution and polyimide precursor solution coatings were measured at different shear rates (0.01-5 s(-1)) by adjusting the magnetic field gradient. The effect of proximity to the substrate on the particle motion was characterized and compared with theoretical predictions. The magnetic microrheometer was used to characterize the time-viscosity profile of PVA coatings during drying at several temperatures. The viscosity range measured by the apparatus was 0.1-20 Pa s during drying of coatings at temperatures between room temperature and 80 °C.

Improvement of Coke Strength by PVA Coating on the Surface of Coke

Due to enlargement, stabilized and efficient operation of blast furnaces (BF), cokes with high strength have been required in BF in recent years. Recently, on the coke reactivity with carbon dioxide, it is reported that high reactive cokes can improve the reduction of iron ore in BF and reduce carbon dioxide emissions from BF. These coke strength (DI) and coke reactivity (CRI) have been primarily controlled by the blending operation of coals in coke production. However, it is difficult to get the cokes which possess both high DI and high CRI, because the blending operation for increasing DI usually results in the decrease of CRI. To get high DI, we investigated the effect of coating on coke with polyvinyl alcohol (PVA) on coke strength. Coke particles were dipped into the PVA aqueous solution and dried out. DI and CRI/CSR of the PVA coated coke prepared by the above method were measured. Those results showed that 0.011 g/g-coke PVA coating on the surface of the coke resulted in the increase of the DI by 4.2 points and no change in the CRI/CSR values. It may be possible to control the coke strength (DI) and the coke reactivity (CRI) independently without any change of coal blending by using our new method.

Relative Humidity Sensor Based on Tilted Fiber Bragg Grating With Polyvinyl Alcohol Coating

A relative humidity (RH) sensor based on tilted fiber Bragg grating (TFBG) is proposed by utilizing polyvinyl alcohol (PVA) as the sensitive cladding film. RH increasing in the PVA coating will result in reduction of refractive index. Due to the TFBG's sensitivity to ambient refractive index, the spectral properties of PVA-coated TFBG are modified under exposure to different ambient humidity levels ranging from 20% to 98% RH. The transmission power of TFBG has different linear behaviors for two different humidity ranges (20%-74% RH and 74%-98% RH), and the sensitivity for each humidity range reaches as high as 2.52 and 14.947 dBm/%RH, respectively. Combining the advantages of optical fiber grating and PVA as a smart material, this design involves simple configuration, low cost, compactness, a small degree of hysteresis, stability, and wide dynamic sensing range as well. Therefore, the sensor could be applied in real-time RH monitoring for normal as well as extremely humid environments.

Silver Nanoparticle-Doped Polyvinyl Alcohol Coating as a Mediumfor Surface-Enhanced Raman Scattering Analysis

A simple polymer substrate for inducing Surface-Enhanced Raman Scattering (SERS) has been investigated. This SERS substrate consists of a solid support, such as a glass slide covered with polyvinyl alcohol (PVA) impregnated with fine silver nanoparticles. The preparation simply involves mixing aqueous PVA polymer with solid AgNO3 to produce a solution that can be easily spin coated on the glass substrate and dried to obtain a hard translucent coating. Aqueous solution of FeSO4.7H2O was used to reduce Ag+ ions to silver nanoparticles. The effects of various experimental conditions of sample preparation were investigated in order to improve the Raman enhancement efficiency of the substrate. The overall substrate performance was evaluated with the use of biologically important compounds: benzoic acid, p-amino benzoic acid, pyridine and dopamine. The spectral features of these compounds closely matched with those reported in literature. The use of the polymer matrix made the SERS substrate resistant to scratching, therefore, improving it to be more suitable for field applications. The hydrophilic nature of the polymer provides additional advantages for probing biological samples. The shelf-life of the dried, unreduced substrates is at least one month.

Low temperature deposition of TiO 2 thin films on polyvinyl alcohol fibers with photocatalytical and antibacterial activities

Fine particles of photoactive anatase-type TiO 2 coated polyvinyl alcohol (PVA) fibers (TiO 2/PVA) were prepared successfully via a simple dip-coating method. Tetrabutyl orthotitanate (TBOT) was hydrolyzed in presence of hydrolysis control agent tetrabutylammonium hydroxide (TBA)OH and the TiO 2 fine particles were crystallized under microwave (MW) irradiation. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) analyses indicated that the fine particles obtained with MW irradiation have much higher crystallinity with a single phase anatase compared with the non-MW-treated solution. The continuous layers of titania were found on PVA fibers by the scanning electron microscopy (SEM) analysis. The fibers with anatase coatings showed high photocatalytic property on the photodegradation of methylene blue (MB) and high antibacterial activity.

Effect of cell media on polymer coated superparamagnetic iron oxide nanoparticles (SPIONs): Colloidal stability, cytotoxicity, and cellular uptake studies

The influence of the composition of the polymer coated polyvinyl alcohol (PVA), vinyl alcohol/vinyl amine copolymer (A-PVA) and polyethylenimine (PEI) coated superparamagnetic iron oxide nanoparticles (SPIONs) on the colloidal stability, cytotoxicity and cellular uptake of these particles in different cell media is reported in this paper. Although all examined polymer coated SPIONs were stable in water and PBS buffer these colloidal systems had different stabilities in DMEM or RPMI media without and supplemented with fetal calf serum (FCS). We found that A-PVA coating onto the surface of the SPIONs decreased the cytotoxicity of the polymer compared to the same concentration of A-PVA alone. As well, polyplexes of PEI-SPIONs with DNA in concentration used for transfection experiments showed no cytotoxicity compared to PEI and PEI-SPIONs. Our data show that the choice of medium largely influences the uptake of these particles by HeLa cells. The optimal medium is different for the different examined polymer coated SPIONs and it should be determined in each case, individually.

Resonant Enhanced Large Third-Order Optical Nonlinearities and Responses of Polyvinyl Alcohol Coating Films Containing J-like Aggregates of a Cyanine Dye

The third-order optical nonlinearities and responses of polyvinyl alcohol (PVA) coating films containing J-like aggregates of a cyanine dye called NK-3261 were measured by a femtosecond degenerate four-wave mixing (DFWM) technique under resonant conditions. The temporal profiles of the DFWM signal of the PVA coating films containing the J-like aggregates of NK-3261 consisted of three components, i.e., the coherent instantaneous nonlinear response (electronic response) and two slow responses with decay time constants of ca. 1.2 ps and ca. 5.6 ps. The electronic component of the effective third-order nonlinear optical susceptibility, χe(3), of one of the films was as high as ca. 1.1 ×10-7 esu at 850 nm.

Single-cell analysis using capillary electrophoresis: influence of surface support properties on cell injection into the capillary.

Capillary electrophoresis (CE) is an important tool of chemical cytometry. Whole-cell analysis using CE starts with cell injection into the capillary by either siphoning or electroosmosis. However, strong adherence of the cell to the support surface can prevent efficient cell injection and lead to irreproducible analysis. Here we evaluated several surfaces as potential cell supports for HT29 cells (human colon adenocarcinoma). These cells strongly adhered to the surface of untreated glass or polystyrene. Hydrophobic coating with dimethyldichlorosilane (DMS) or Sigmacote did not significantly reduce cell adhesion. In contrast, cell adhesion was reduced significantly when the surface was modified with hydrophilic polymers (hydrogels) such as poly(2-hydrohyethyl methacrylate) (PHEMA) and polyvinyl alcohol (PVA). In addition to their pronounced antiadhesive properties, PHEMA and PVA coatings were the most biocompatible (had highest survival of cells in contact with surface). Hydrogel-coated polystyrene plates were tested as a commercial alternative to hydrogel-coated glass slides. The cell adhesive properties of such plates were similar to those of PHEMA and PVA. However, the biocompatibility of the plates was lower than that of the other surfaces tested. Moreover, in contrast to PHEMA- and PVA-coated glass slides, the plates were sensitive to UV light and therefore should not be used when fluorescent image microscopy with UV excitation precedes CE. The analyses of the data obtained showed that PHEMA- and PVA-coated glass slides were the most suitable cell supports for cell injection into the capillary.

Simultaneous stereoselective analysis of tramadol and its main phase I metabolites by on-line capillary zone electrophoresis–electrospray ionization mass spectrometry

On-line combination of partial filling capillary electrophoresis and electrospray ionization mass spectrometry was demonstrated for the simultaneous enantioseparation of tramadol and its main phase I metabolites. The partial filling technique was efficient at avoiding MS contamination by the chiral selector. Different experimental factors were investigated, including the chiral selector nature and concentration, plug length as well as the separation temperature. The best enantioseparation of the investigated compounds was achieved with a coated polyvinyl alcohol capillary and a 40 m M ammonium acetate buffer, pH 4.0, adding sulfobutyl ether β-cyclodextrin (2.5 mg/ml) as the chiral selector. The charged cyclodextrin not only allowed enantioseparation of tramadol and its metabolites, but also improved the selectivity of compounds with the same molecular mass. Finally, CE–electrospray ionisation-MS was successfully applied to the stereoselective analysis of tramadol and its main metabolites in plasma after a simple liquid–liquid extraction.