Gentamicin-Loaded Wound Dressing With Polyvinyl Alcohol/Dextran Hydrogel: Gel Characterization and In Vivo Healing Evaluation

To develop a gentamicin-loaded wound dressing, cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and dextran using the freezing–thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength, and thermal property were investigated. In vitro protein adsorption test, in vivo wound healing test, and histopathology were performed. Dextran decreased the gel fraction, maximum strength, and thermal stability of hydrogels. However, it increased the swelling ability, water vapor transmission rate, elasticity, porosity, and protein adsorption. The drug gave a little positive effect on the gel properties of hydrogels. The gentamicin-loaded wound dressing composed of 2.5% PVA, 1.13% dextran, and 0.1% drug was more swellable, flexible, and elastic than that with only PVA because of its cross-linking interaction with PVA. In particular, it could provide an adequate level of moisture and build up the exudates on the wound area. From the in vivo wound healing and histological results, this gentamicin-loaded wound dressing enhanced the healing effect more compared to conventional product because of the potential healing effect of gentamicin. Thus, this gentamicin-loaded wound dressing would be used as a potential wound dressing with excellent forming and improved healing effect in wound care.     

Polyvinyl Alcohol as a Water-Soluble Marker

The usefulness of partially hydrolyzed polyvinyl alcohol (PVA ${\displaystyle \overline{\text{P}}}$ =500) was examined by the absorption and excretion from the gastro-intestinal tract of adult rat. About 86% of orally injected PVA was excreted in feces in 48 hr, but no excretion was observed in urine. More than 50% of PVA injected into heart was excreted in urine in 12 hr, but no fecal PVA was observed. About 100% of orally injected PVA was recovered in the gastro-intestinal tract killed 5.5 hr after injection, but no PVA was observed in blood from the killed rats.     

The Polyvinyl Alcohol Sponge Model Implantation

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds^1-3. Because of this complexity, wound healing studies are most comprehensive when carried out in vivo. There are many in vivo models available to study acute wound healing, including incisional, excisional, dead space, and burns. Dead space models are artificial, porous implants which are used to study tissue formation and the effects of substances on the wound. Some of the commonly used dead space models include polyvinyl alcohol (PVA) sponges, steel wire mesh cylinders, expanded polytetrafluoroethylene (ePTFE) material, and the Cellstick^1,2.Each dead space model has its own limitations based on its material''s composition and implantation methods. The steel wire mesh cylinder model has a lag phase of infiltration after implantation and requires a long amount of time before granulation tissue formation begins¹. Later stages of wound healing are best analyzed using the ePTFE model^1,4. The Cellstick is a cellulose sponge inside a silicon tube model which is typically used for studying human surgery wounds and wound fluid². The PVA sponge is limited to acute studies because with time it begins to provoke a foreign body response which causes a giant cell reaction in the animal⁵. Unlike other materials, PVA sponges are easy to insert and remove, made of inert and non-biodegradable materials and yet are soft enough to be sectioned for histological analysis^2,5.In wound healing the PVA sponge is very useful for analyzing granulation tissue formation, collagen deposition, wound fluid composition, and the effects of substances on the healing process^1,2,5. In addition to its use in studying a wide array of attributes of wound healing, the PVA sponge has also been used in many other types of studies. It has been utilized to investigate tumor angiogenesis, drug delivery and stem cell survival and engraftment^1,2,6,7. With its great alterability, prior extensive use, and reproducible results, the PVA sponge is an ideal model for many studies^1,2.Here, we will describe the preparation, implantation and retrieval of PVA sponge disks (Figure 1) in a mouse model of wound healing.     

Immobilization of Champagne Yeasts by Inclusion into Cryogels of Polyvinyl Alcohol: Means of Preventing Cell Release from the Carrier Matrix

Wine champagnizing, a process involving the use of champagne yeasts immobilized by inclusion into cryogels of polyvinyl alcohol, has been studied. Treatment of yeast cells with the autoregulatory factor d ₁ was proposed as a means of preventing the cell release from the carrier matrix. Such a treatment inhibited growth and proliferation processes in yeast cells, without affecting the activity of fermentation; the resulting champagne had the same organoleptic and chemical characteristics as its counterparts obtained using conventional techniques.     

Symbiotic Utilization of Polyvinyl Alcohol by Mixed Cultures

Polyvinyl alcohol (PVA)-utilizing cultures were obtained from various sources. They were mixed cultures even after cyclical transfer to liquid and plate media with PVA as a sole source of carbon. Component bacteria were isolated from the several mixed cultures, and it was shown that PVA was utilized symbiotically by two bacterial members which could not utilize PVA in each respective pure culture. From a mixed culture, strains VM15, VM15A (Pseudomonas putida) and VM15C (Pseudomonas sp.) were isolated as members essential for PVA utilization. VM15C was the predominant strain in the mixed-culture population and produced PVA-degrading enzyme. The culture supernatant of VM15A enabled VM15C to grow on PVA. VM15A was presumed to supply VM15C with a unique growth stimulant which was distinct from usual growth factors.     

Neurotoxic Organophosphate Degradation with Polyvinyl Alcohol Gel-Immobilized Microbial Cells

A genetically engineered strain of Escherichia coli that expresses organophosphorus hydrolase (OPH) was immobilized in a polyvinyl alcohol (PVA) cryogel to form a porous biocatalyst that successfully degrades organophosphorus (OP) neurotoxins. The impacts of both diffusion and reaction on biocatalyst efficiency were determined to enable prediction and optimization of the biocatalyst performance. The kinetic rate parameters and activation energies of pure OPH, free cell suspensions, and the immobilized cell biocatalyst were compared. Diffusion was a determining factor for paraoxon hydrolysis because of the very rapid OPH kinetics for its model substrate. Both the paraoxon diffusion through the PVA matrix and the diffusion associated with microbial transport of paraoxon were shown to impact the biocatalyst reaction. However, the enhancement in storage stability resulting from diffusional limitations provides an advantage to diffusion-limited operation. This research may serve as a guide to define the influence of diffusion in biological reaction systems. The broad substrate specificity and hydrolytic efficiency of OPH coupled with the ability to genetically engineer the enzyme for specific target OP neurotoxins enhance the suitability of OPH-based technologies for detoxification of these compounds. Cryoimmobilization provides a suitable vehicle as a cost-effective, efficient technology for bioremediation of environmental media contaminated with OP compounds.     

Formation of Hydrogen Peroxide by a Polyvinyl Alcohol Degrading Enzyme

A method for purification and crystallization, and some properties of ribonuclease from Aspergillus sp. [EC 2.7.7.17] (RNase L) are reported. The purification procedure consisted of six steps, including acetone precipitation, column chromatographies on Duolite A–2 and DEAE-cellulose, repeated chromatography on DEAE-Sephadex A–50 column and affinity chromatography on 5’-AMP-Sepharose 4B column. Crystallization was performed by the dialysis against ammonium sulfate solution at 60% saturation.

The crystalline enzyme was shown to be homogeneous by polyacrylamide disc electrophoresis and ultracentrifugation. Svedberg value of the crystalline enzyme was 4.2. The enzyme was the most active at pH 3.5 and 60~65°C, and it was inhibited markedly with Fe.³⁺

RNase L has no absolute base specificity, and produces four kinds of 3’-mononucleotides from yeast RNA. However, the susceptibility of four nucleotide residues to RNase L increases in the order; G < A < C < U and is quite different from those of RNase T₂, RNase M and RNase R.     

Production of Polyvinyl Alcohol Oxidase by a Symbiotic Mixed Culture

Production of polyvinly alcohol (PVA) oxidase by Pseudomonas sp. strain VM15C, a PVA degrader of a symbiotic PVA-utilizing mixed culture, was examined in various cultures. Despite the absence of PVA in the culture in nutrient broth, VM15C showed approximately the same productivity of PVA oxidase activity as that in the culture with PVA as the sole carbon source, whereas the productivity in the culture with glucose was lower than that of either the nutrient broth or the PVA culture. PVA oxidase activity produced in the nutrient broth culture was predominantly present in the cells, and most of the activity appeared to be in the cytoplasm. In contrast, in the culture with PVA as the sole carbon source, the activity was present in the culture fluid in a larger ratio than in the nutrient broth culture. Thus, production of PVA oxidase activity by this strain was constitutive and repressible, although localization of the produced activity was changed by growth conditions.     

Rheological and Performance Research on a Regenerable Polyvinyl Alcohol Fracturing Fluid

A regenerable polyvinyl alcohol/organic boron fracturing fluid system with 1.6 wt% polyvinyl alcohol (PVOH) and 1.2 wt% organic boron (OBT) was studied, and its main regeneration mechanism is the reversible cross-linking reaction between B(OH)₄^- and hydroxyl groups of PVOH as the change of pH. Results of rheology evaluations show that both the apparent viscosity and the thermal stability of the fracturing fluid decreased with the regeneration number of times increasing. In addition, the apparent viscosity of the fluid which was without regeneration was more sensitive to the shear action compared with that of the fluid with regeneration once or twice. When the fracturing fluid was without regeneration, the elasticity was dominating due to the three-dimensional network structure of the formed gel; the viscosity gradually occupied the advantage when the fracturing fluid was regenerated once or twice. The settling velocity of proppant was accelerated by both the regeneration process and the increasing temperature, but it was decelerated when the proppant ratio increased. Results of core damage tests indicate that less permeability damage was caused by the PVOH/OBT fracturing fluid compared with that caused by the guar gum fracturing fluid after gel breaking.     

聚乙烯醇高效降解菌的筛选及降解特性研究

以聚乙烯醇为唯一碳源从环境中筛选获得了高效降解聚乙烯醇的微生物菌株XT11, 初步鉴定为假单胞菌属(Pseudomonas sp.)。对菌株Pseudomonas XT11的生长过程及PVA降解过程进行了研究, 发现该菌株在54 h内可将1 g/L的聚乙烯醇(PVA)降解。同时研究了温度、pH值及酵母膏浓度对该菌株降解PVA的影响, 结果表明其最适温度、pH值和酵母膏浓度分别为30℃、7.0和0.5 g/L。研究了PVA浓度对PVA降解率的影响, 发现随着PVA浓度的增大, PVA的降解率降低。     

Electrospun Ultrafine Fibers from Black Bean Protein Concentrates and Polyvinyl Alcohol

In this study, ultrafine fibers were produced from black bean protein concentrates (BPCs) and polyvinyl alcohol (PVA) by electrospinning. The BPC was denatured under acidic (pH 2) or basic (pH 11) conditions. Polymer solutions containing different PVA concentrations (11% or 21%, w/v) and different BPC: PVA ratios (50:50 or 75:25, v/v) were used for fiber production. The electrical conductivity and rheological properties of the fiber-forming solutions were evaluated, as well as the morphology, size distribution, infrared spectrum, and thermal properties of the electrospun fibers. The fibers showed a homogeneous morphology and diameters ranging from 115 to 541 nm. Fibers from the solution containing BPC denatured at pH 11, 11% PVA, and 75:25 (v/v) BPC: PVA presented the lowest diameter, and those from BPC denatured at pH 2 had less beads than the fibers obtained from BPC denatured at pH 11. The solution formulation affected the thermal properties of the fibers, with weight loss increases ranging from 39.0% to 60.9%. The polymeric solutions containing PVA and BPC (whether denatured under basic or acidic conditions) resulted in ultrafine electrospun fibers with highly favorable characteristics that could potentially be used for the encapsulation of bioactive compounds and food applications.

     

聚乙烯醇高效降解菌的筛选及降解特性研究

以聚乙烯醇为唯一碳源从环境中筛选获得了高效降解聚乙烯醇的微生物菌株XT11,初步鉴定为假单胞菌属(Pseudomonas sp.).对菌株Pseudomonas XT11的生长过程及PVA降解过程进行了研究,发现该菌株在54 h内可将1 g/L的聚乙烯醇(PVA)降解.同时研究了温度、pH值及酵母膏浓度对该菌株降解PVA的影响,结果表明其最适温度、pH值和酵母膏浓度分别为30℃、7.0和0.5 g/L.研究了PVA浓度对PVA降解率的影响,发现随着PVA浓度的增大,PVA的降解率降低.     

熊果苷聚乙烯醇面膜治疗黄褐斑的临床观察

目的:观察熊果苷结合高分子化合物聚乙烯醇(Polyvinyl Alcohol,PVA)面膜治疗黄褐斑的临床疗效。方法:48例黄褐斑患者随机分为两组,治疗组24例,外用熊果苷PVA面膜,对照组24例,予vitC导入治疗,一个月为一疗程。结果:熊果苷治疗组有效率为79.2%;高于对照组(20.8%),差异具有统计学意义(x~2=12.34,P<0.01)。未见明显不良反应。结论:熊果苷PVA面膜疗效确切,配制操作简单,便于临床推广使用。     

抗坏血酸在高粘度聚乙烯醇胶体溶液中分散均一性考察

目的:考察了采用实验室常用的磁力搅拌法和改进的机械搅拌法后,聚乙烯醇胶体溶液中抗坏血酸的分布均一度。接着,在机械搅拌法的基础上,研究了抗坏血酸粉末与抗坏血酸溶液在胶中分散的均一性。方法:分散混合方法:机械搅拌法,磁力搅拌法;均一性检验方法:以单位质量胶载药量RSD值作为指标;统计学分析方法:t检验。结果:采用磁力搅拌法不能够较好地混合抗坏血酸与PVA胶体溶液;而机械搅拌法RSD值控制在10%以内,说明胶中抗坏血酸均一分布,符合生产要求。T检验表明两种方法具有显著性差异。药物溶于水后分散更为均一。结论:解决药物在高粘度溶液介质中均匀分散的问题。     

Polyvinyl Alcohol with Cadmium Iodide and Fructose as an Aqueous Mounting Medium

An aqueous histologic and cytologic mounting medium containing polyvinyl alcohol, cadmium iodide and fructose is described. It is used in the preparation of permanent slides and may be applied to sections stained and rinsed in water or in any concentration of ethyl alcohol. The medium forms a hard, tough, quick-drying film which adheres well to the slide and cover glass. It is nonfluorescent, clear, optically homogeneous, and isotropic; it does not admit bubbles under the cover glass or crystallize on drying. It prevents or minimizes the bleeding of many stains from the sections; a list of 60 dyes, mostly basic, is given. The fresh medium has a pH of 4.4. The refractive index of the fresh medium is n_D²⁰ 1.4674; the dried film is n_D 1.6020 which may be lowered to n_D 1.5150 by decreasing the cadmium iodide in the formula. The viscosity at 25°C. is 7,299 centipoises. The medium has the following composition: distilled water, 40 g.; cadmium iodide, 34 g.; polyvinyl alcohol (Elvanol 51-05, du Pont's low viscosity grade) 18 g.; fructose, 8 g. The medium is prepared as follows: wash the polyvinyl alcohol with absolute methyl alcohol; dry and then grind in a mortar; dissolve the cadmium iodide in the water; add the polyvinyl alcohol while stirring with a speed-controlled motor-driven mixer; heat to 75°C. on a water bath with continuous stirring until dissolved; remove from the water bath and add the fructose while stirring; replace water lost by evaporation. The medium is ready for use when the foam has dispersed after standing.     

Changes in Sulfhydryl Groups and Hydrodynamic Behavior of Thiolated Polyvinyl Alcohol Reacted with Oxidized Lipid

A synthetic polymer, thiolated polyvinyl alcohol (SH-PVA), was used for examining the reaction between sulfhydryls and lipids during dough mixing. When SH-PVA was incubated with linoleic acid hydroperoxide at a concentration of 1/12 to 1/4 mole to a mole of SH group, progressive oxidation of sulfhydryl was observed and a part of disulfides seemed to be further oxidized in some cases. The hydrodynamic behavior of SH-PVA treated with oxidized linoleic acid was similar to that of SH-PVA treated with an oxidizing agent, potassium bromate; non-Newtonian flow and increase in viscosity were observed. The peak of the gel filtration pattern of SH-PVA shifted to a faster elution position upon treatment with oxidized linoleic acid. These results probably indicate the formation of an interchain disulfide linkage. In view of these results, we discussed the role of lipids involved in oxidation of free SH groups in the rheological properties of gluten and dough.     

Improved Paper Pulp from Plants with Suppressed Cinnamoyl-CoA Reductase or Cinnamyl Alcohol Dehydrogenase

Transgenic plants severely suppressed in the activity of cinnamoyl-CoA reductase were produced by introduction of a partial sense CCR transgene into tobacco. Five transgenic lines with CCR activities ranging from 2 to 48% of wild-type values were selected for further study. Some lines showed a range of aberrant phenotypes including reduced growth, and all had changes to lignin structure making the polymer more susceptible to alkali extraction. The most severely CCR-suppressed line also had significantly decreased lignin content and an increased proportion of free phenolic groups in non-condensed lignin. These changes are likely to make the lignin easier to extract during chemical pulping. Direct Kraft pulping trials confirmed this. More lignin could be removed from the transgenic wood than from wild-type wood at the same alkali charge. A similar improvement in pulping efficiency was recently shown for poplar trees expressing an antisense cinnamyl alcohol dehydrogenase gene. Pulping experiments performed here on CAD-antisense tobacco plants produced near-identical results – the modified lignin was more easily removed during pulping without any adverse effects on the quality of the pulp or paper produced. These results suggest that pulping experiments performed in tobacco can be predictive of the results that will be obtained in trees such as poplar, extending the utility of the tobacco model. On the basis of our results on CCR manipulation in tobacco, we predict that CCR-suppressed trees may show pulping benefits. However, it is likely that CCR-suppression will not be the optimal target for genetic manipulation of pulping character due to the potential associated growth defects.     

聚乙烯醇复合水凝胶外用膜剂的制备与性能*

摘要目的：考察PVA/ 葡聚糖/ 羧甲基纤维素钠复合水凝胶外用膜剂的制备方法,并与纯PVA 水凝胶贴膜进行对比,考察本膜 剂在物理性能和药物体系的体外释放行为上所具备的优越性。方法：利用冷冻-解冻物理交联方法制备水凝胶装载胰岛素模型药 物的外用膜剂,通过万能拉力机和差示扫描量热法考察膜剂的物理性能,利用高效液色谱法考察该膜剂的体外释放行为。结果： PVA复合水凝胶外用贴膜相较于纯PVA水凝胶贴膜的韧性减小、刚性增加,体外释放变好。结论：通过将具有材料友好性的PVA 和多糖葡聚糖、羧甲基纤维素钠合并使用制备胰岛素复合水凝胶贴膜,既能保证贴膜具有良好的物理性能,又具有较好地释放行 为,优于目前文献报道的纯PVA水凝胶贴膜性能,有望继续研究优化性能。     

Electric Field-Controlled Benzoic Acid and Sulphanilamide Delivery from Poly(Vinyl Alcohol) Hydrogel

The controlled release of benzoic acid (3.31 Å) and sulphanilamide (3.47 Å) from poly(vinyl alcohol), PVA, hydrogels fabricated by solution casting at various cross-linking ratios, were investigated. The PVA hydrogels were characterized in terms of the degree of swelling, the molecular weight between cross-links, and the mesh size. The drug release experiment was carried out using a modified Franz diffusion cell, at a pH value of 5.5 and at temperature of 37°C. The amount of drug release and the diffusion coefficients of the drugs from the PVA hydrogels increased with decreasing cross-linking ratio, as a larger mesh size was obtained with lower cross-linking ratios. With the application of an electric field, the amount of drug release and the diffusion coefficient increased monotonically with increasing electric field strength, since the resultant electrostatic force drove the ionic drugs from the PVA matrix. The drug size, matrix pore size, electrode polarity, and applied electric field were shown to be influential controlling factors for the drug release rate.KEY WORDS: electrophoresis force, ionic drug delivery, iontophoresis, poly(vinyl alcohol)     

Enhanced Degradation of Polyvinyl Alcohol by Pycnoporus cinnabarinus after Pretreatment with Fenton’s Reagent

Degradation of polyvinyl alcohol (PVA) was investigated by using a combination of chemical treatment with Fenton’s reagent and biological degradation with the white rot fungus Pycnoporus cinnabarinus. Inclusion of the chemical pretreatment resulted in greater degradation of PVA than the degradation observed when biological degradation alone was used.