Cytotoxicity testing of wound-dressing materials

A method was developed for testing the cytotoxicity of various bandage-like wound dressings and gel wound dressings. In this method, the ability of human polymorphonuclear neutrophils (PMNs) to initiate a respiratory burst after exposure to the various wound dressings is used as a marker of cytotoxicity. Luminol-amplified chemiluminescence stimulated with opsonised zymosan or phorbol 12-myristate 13-acetate (PMA) is used to measure the degree of activation of the respiratory burst, i.e. the NADPH oxidase activity, after exposure to wound dressings. Opsonised zymosan (material from yeast cell walls) is a phagocytic stimulus that activates the NADPH oxidase by binding to FC-receptors and complement receptors, and functions as an artificial bacterium, whereas PMA activates the NADPH oxidase by direct activation of protein kinase C. NADPH oxidase activity was inhibited by several wound dressings. The down-regulation of the respiratory burst is detrimental to the bactericial effect of PMNs, and can be used as a marker for the cytotoxicity of wound dressing materials.     

Clinical trials of amniotic membranes in burn wound care

Four test conditions of increasing complexity were used to evaluate the clinical efficacy of amniotic membranes as biologic dressings on donor sites and burn wounds in children. These were the clean-skin donor-site wound, the uncontaminated shallow partial-thickness burn wound, the bed of freshly excised full-thickness wounds, and the granulating surface of colonized burn wounds. The rate of epithelialization under amniotic membranes was the same as that under 5% scarlet red ointment or 0.5% silver nitrate solution dressings. Preservation of a healthy excised wound bed and maintenance of a low bacterial count in contaminated wounds paralleled the experience with human allograft dressings despite technical difficulties and the absence of vascularization of amniotic membrane and its fragile structure. Tentative conclusions are drawn as to the mechanisms by which biologic dressings exert their beneficial effects.     

Swelling of hydrocolloid dressings

Wound healing is promoted by dressings that maintain a moist environment. Specifically, hydrocolloid dressings allow excess fluid to escape without permitting wound desiccation. However, the fluid handling capacity of hydrocolloid dressings depends on many factors such as the physicochemical properties of the gel formulation, and the design of the dressing. We measured the moisture uptake kinetics of different hydrocolloid dressings by placing the gel side of a sample in contact with water. The time evolution of the thickness was measured by means of a video camera linked to a computer. The theory of Tanaka and Fillmore 1979 was used to predict the kinetics of uniaxial swelling of a cylindrical gel sample. The model allows to associate to an experimental curve a total thickness increase h_f — h₀ (where h_f and h₀ are respectively the final and initial thickness) and a characteristic time τ. The model also relates h_f — h₀ and τ to the physicochemical composition of the dressing, and to the initial thickness h₀. The influence of h₀ is discussed by means of experiments performed on dressings with different initial thickness.     

Wound dressings for a proteolytic-rich environment

Wound dressings have experienced continuous and significant changes over the years based on the knowledge of the biochemical events associated with chronic wounds. The development goes from natural materials used to just cover and conceal the wound to interactive materials that can facilitate the healing process, addressing specific issues in non-healing wounds. These new types of dressings often relate with the proteolytic wound environment and the bacteria load to enhance the healing. Recently, the wound dressing research is focusing on the replacement of synthetic polymers by natural protein materials to delivery bioactive agents to the wounds. This article provides an overview on the novel protein-based wound dressings such as silk fibroin keratin and elastin. The improved properties of these dressings, like the release of antibiotics and growth factors, are discussed. The different types of wounds and the effective parameters of healing process will be reviewed.     

Experimental evaluation of the effectiveness of wound dressings based on biologically active substances from marine hydrobionts

This article presents the experimental data on the testing of new wound dressings, viz., porous plates, prepared on the basis of chitosan and calcium alginate that contain biologically active substances (BASs) derived from marine hydrobionts. In a burn wound model in guinea pigs, we revealed a positive effect of tested samples of wound dressings on the wound-healing process; the data of planimetric and pathomorphological studies showing the acceleration of the process of regeneration in the wound are discussed. It was noted that the dynamics and patomorphological characteristics of the wound healing process differed depending on the structure of the BAS included into the composition of wound dressings (peptides, sulfated polysaccharides, a complex of amino acids and peptides).     

静电纺丝用作难愈合伤口敷料的研究进展

静电纺丝伤口敷料作为一种新型功能性敷料,具有较大的比表面积、可调控的孔隙率和良好的生物性能,既有益于细胞呼吸,又 可抑制细菌感染伤口,并能促进细胞增殖和加速创面愈合,是未来伤口敷料研发领域发展的新方向。介绍静电纺丝纳米纤维的原理、特点, 重点阐述各类聚合物、生物活性物质在静电纺丝伤口敷料制备中的应用进展。     

The dependence of efficacy of cell growth on biosynthetic medicinal materials on the microstructure of their surface

The efficacy of the novel class of dressings was studied. The natural and synthetic polymeric components of them are arranged not in layers, but in a unified structure, i.e., form a new composite material. In particular, it was determined whether the interaction of a dressing surface with cells of injured tissue and/or culture grown in vitro depends on the microstructure of the surface. The efficiency of cell growth has been considered from the point of view of stimulation of cell growth. The microstructure of the surface was studied by the method of high-resolution electron microscopy. The results of the study showed that the structure of biosynthetic dressings depends on variations of the composition and ratio of components. The role of the microstructure of the dressing in the efficacy of its function was demonstrated. Factors producing the most significant effect on the regenerating properties of wound dressings were revealed.     

THE AVOIDANCE OF EXCESSIVE SUPERHEATING DURING STEAM STERILIZATION OF DRESSINGS

SUMMARY: During the steam sterilization of dressings some degree of superheating occurs. With dressings normally hydrated, that is with about 5% moisture content, the small degree of superheating which occurs is unlikely to be of consequence; but if dressings contain less than 1% of moisture before sterilization, a significant degree of superheating may occur. The use of drums is neither an advantage nor a disadvantage in regulating superheating, which occurs to the same degree whether the air is removed initially by vacuum pump or by downward displacement. The use of a high initial vacuum does not increase the risk of superheating.     

Electrospinning of honey and propolis for wound care

Phytochemicals and naturally derived compounds, such as plant extracts and bee products, are regarded as complementary and alternative medicines for the treatment of skin wounds, due to their antibacterial, anti-inflammatory, and antioxidant properties. In recent years, it has been shown that dressings impregnated with honey (particularly Manuka honey) are effective for the topical treatment of wounds and burns, and some of them are currently used in clinics. This has stimulated the development of more advanced dressings based on polymeric nanofibres that can release honey and other bee products (like propolis) to promote wound healing. In this review, the current literature on the electrospinning of honey and propolis is analyzed and the effectiveness of the resulting dressings to inhibit bacterial growth and stimulate cellular proliferation and tissue repair is discussed.     

Effects of mildew on the growth and yield of spring barley: 1969-72

Mildew decreased grain yield by decreasing ear number and grain size (but not grain number/ear), the damage depending on the earliness and severity of mildew. In 1971 when mildew was early and severe, ethirimol seed dressings at 0.22 kg a.i./ha, which gave only early protection, increased yield more than did ethirimol sprays applied to protect the flag leaf and ear. In 1972 sprays were better than seed dressings at this rate because mildew was less severe during the seedling stages.     

VACUUM DRYING OF STEAM STERILIZED DRESSINGS

SUMMARY: The degree of vacuum and time of application needed to dry steam sterilized dressings has been investigated. If the steam supply is dry, and the pressure in the drying stage is reduced to an absolute pressure of 50 mm Hg, dressings will be cool and dry without holding the vacuum, provided they are not damp before sterilization.     

Effect of a controlled abacterial environment on the Pseudomonas aeruginosa infection of suppurative wounds

The present work deals with the data on the isolation rate of P. aeruginosa from suppurative wounds of different origin during their treatment by the commonly used methods under dressings and by the open method under the conditions of controlled germ-free environment. The results of the immunotyping of P. aeruginosa strains isolated from patients treated by different methods are presented. The dynamics of changes in the isolation rate of P. aeruginosa at different periods of treatment, both by the open method and with the use of dressings, is shown. Among P. aeruginosa strains isolated from suppurative wounds, those belonging to immunotypes 6, 7 and 2, as well as nontyping strains, occurred most frequently. Treatment in the controlled germ-free environment permits the protection of the wound surface from hospital infection. During treatment with the use of dressings the cases of hospital infection were revealed (31.3%). Such infection occurred, as a rule, at a later period of treatment.     

Morphological characteristics of the healing of burn wounds covered by an activated-charcoal tissue dressing

Activated-charcoal cloth and dressings product based upon this material were applied for covering burn wounds. As a control served a gauze dressings with greases and solution topical drugs. The healing of deep thermal burns of 3rd degree on rabbits studied by a histological method was differed by a rapid decreasing of inflammation reaction, active epithelialization and soft scar formation. A clinical use in 15 burned patients was shown that in combination with enzymatic and antimicrobial drug solutions these materials accelerate healing and epithelialization of superficial burn wounds and improve treatment of deep burn wounds before autodermoplasty.     

Secondary correction of the burned eyelid deformity.

We describe our experience in late reconstructions of 35 burned eyelids. On this basis we advocate wide, aggressive release of all scar contractures, including the distal part of the levator when necessary. To cover the resultant defects we use generous full-thickness skin grafts, if available, for both the upper and lower lids. Rarely has a tarsorrhaphy been required, and properly constructed dressings provide satisfactory lid immobilization and permit conjunctival hygiene. During the postoperative period the vision need not be obstructed by a tarsorrhaphy, Frost sutures, or the dressings.     

Effect of a Synthetic Dressing Formed on a Burn Wound in Rats: a Comparison of Allografts, Collagen Sheets, and Polyhydroxyethylmethacrylate in the Control of Wound Infection

Allograft dressings to control Pseudomonas wound infections in rats were studied on surgical wounds and escharectomized burn wounds. The effects of allografts were compared with a collagen sheet (Aviderm) and a synthetic dressing, polyhydroxyethylmethacrylate (Hydron), formed on the wound by mixing the polymer and the solvent. The results indicated that infections in surgical wounds were more easily controlled by dressings than similar contaminations in burn wounds. A procedure was described for the formation of a synthetic dressing directly on the wound from a mixture of polymer and solvent. This type of preparation completely filled the wound area and sealed the edges, preventing further contamination, and gave excellent coverage of the wound. With 24 h of coverage of escharectomized burn wounds, allografts provided the best dressing for reduction of wound organisms. At 96 h of coverage, Hydron and Aviderm produce significant reductions in the Pseudomonas resident in the burn wound. The results support the thesis that suitable dressings promote local host defense processes which kill the contaminating bacteria.     

SCAB, CANKER, AND BRANCH BLISTER OF APPLE AT EAST MALLING IN RELATION TO NUTRITIONAL TREATMENT OF THE HOST

On the sandy loam at East Mailing, moderate annual dressings of inorganic sources of nitrogen and potash exerted no consistent influence on the incidence of apple scab, even when the dressings were continued over an eleven-year period on established trees of four different varieties on M.IX rootstock. Likewise, no influence of such dressings continued over five seasons was shown on the incidence of apple canker on the rootstock M.VIII, which was grown under conditions favourable for severe infection.
There was evidence from early observations that grassing-down to excess can reduce the incidence of scab, but only at the expense of nitrogen starvation in the trees. Short-term mixed leys had no such effect.
The incidence of branch blister, a functional disease associated with adverse soil conditions and retarded vigour, was greatly reduced in the variety Cox's Orange Pippin by potash manuring, and was further influenced by the rootstock.     

Seed treatments with benomyl and other fungicides for the control of Ascochyta pisi on peas

In three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl-1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed-gave complete control of Ascochyta infection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dressing.     

Technique to Improve the Rate of Healing of Incised Abscesses

In a comparative investigation incised skin abscesses were treated by either introducing sterile fusidic acid gel into the cavity on one occasion only or applying daily superficial dressings impregnated with sodium fusidate ointment. In comparison with the dressing group, the intracavity use of fusidic acid gel reduced the mean healing time of incised abscesses by approximately one-half. When abscesses were analysed according to site and size, the reduction in mean healing time was equally striking. No hypersentisivity or irritation to fusidic acid or its sodium salt applied by either method was observed.The procedure of introducing fusidic acid gel into an incised abscess cavity is a promising alternative to superficial antibiotic dressings or wicks in the treatment of incised abscesses.     

Use of Irradiated Amnion as a Biological Dressing in the Treatment of Radiation Induced Ulcers

The management of moist skin desquamation (ulceration) following radiation therapy has been a concern since the inception of this therapy. The treatment of skin reactions focuses on promoting healing, improving patient comfort preventing infection and decreasing trauma to the area. Various dressings like topical preparations, hydrocolloid and gentian violet 1 % dressing have been used for its treatment. We present our experience with the use of amnion as a biological dressing in patients with radiation induced ulceration following pelvic radiation using megavoltage beam. The preliminary experience with treatment in 14 patients proved to be cost effective due to a shorter duration of ulcer healing (median of 7 days), fewer dressing changes (median of 4 dressings) and diminished use of analgesics.     

GNPs-CS/KGM as Hemostatic First Aid Wound Dressing with Antibiotic Effect: In Vitro and In Vivo Study

Ideal wound dressing materials should create a good healing environment, with immediate hemostatic effects and antimicrobial activity. In this study, chitosan/konjac glucomannan (CS/KGM) films embedded with gentamicin-loaded poly(dex-GMA/AAc) nanoparticles (giving GNP-CS/KGM films) were prepared as novel wound dressings. The results revealed that the modified CS/KGM films could be used as effective wound dressings and had significant hemostatic effects. With their microporous structure, the films could effectively absorb water from blood and trap blood cells. The gentamicinloaded poly(dex-GMA/AAc) nanoparticles (GNPs) also further promoted blood clotting, with their favorable water uptake capacity. Thus, the GNP-CS/KGM films had wound healing and synergistic effects that helped to stop bleeding from injuries, and also showed good antibiotic abilities by addition of gentamicin to the NPs. These GNPCS/KGM films can be considered as promising novel biodegradable and biocompatible wound dressings with hemostatic capabilities and antibiotic effects for treatment of external bleeding injuries.