Modern wound dressings: Manufacturing and properties

The main directions of research aimed at the development of new wound dressings are considered. An important modern trend is the use of biocompatible natural and synthetic polymers and their compositions as the bases of wound dressings. The new products are free of the disadvantages of traditional textile materials, have flexible design, and possess combined properties (including antimicrobial activity), which expands their functions. Important advantages of new dressings are the atraumatic character, effective curative action, and reduced therapy time. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 40, No. 2, pp. 24–31, February, 2006.     

Wound healing dressings and drug delivery systems: a review

The variety of wound types has resulted in a wide range of wound dressings with new products frequently introduced to target different aspects of the wound healing process. The ideal dressing should achieve rapid healing at reasonable cost with minimal inconvenience to the patient. This article offers a review of the common wound management dressings and emerging technologies for achieving improved wound healing. It also reviews many of the dressings and novel polymers used for the delivery of drugs to acute, chronic and other types of wound. These include hydrocolloids, alginates, hydrogels, polyurethane, collagen, chitosan, pectin and hyaluronic acid. There is also a brief section on the use of biological polymers as tissue engineered scaffolds and skin grafts. Pharmacological agents such as antibiotics, vitamins, minerals, growth factors and other wound healing accelerators that take active part in the healing process are discussed. Direct delivery of these agents to the wound site is desirable, particularly when systemic delivery could cause organ damage due to toxicological concerns associated with the preferred agents. This review concerns the requirement for formulations with improved properties for effective and accurate delivery of the required therapeutic agents. General formulation approaches towards achieving optimum physical properties and controlled delivery characteristics for an active wound healing dosage form are also considered briefly.     

Antimicrobial properties of silver-containing wound dressings: a microcalorimetric study

The studies reported here have been undertaken to assess the potential use of isothermal microcalorimetry in studying the antimicrobial efficacy of wound dressings that contain antimicrobial agents. The microcalorimetric technique allows non-invasive and non-destructive analysis to be performed directly on a test sample, regardless of whether it is homogeneous or heterogeneous in nature. Microcalorimetry is an established procedure that offers quantitative measurements and has the distinct advantage over traditional antimicrobial test methodologies in that calorimetric measurements are made continuously over real-time, thus the dynamic response of microorganisms to an antimicrobial agent is observed in situ. The results described in this paper are for interaction of two silver-containing wound care products AQUACEL Ag Hydrofiber (ConvaTec, Deeside, UK) and Acticoat 7 with SILCRYST (Smith and Nephew Healthcare, UK) with the wound pathogenic organisms Staphylococcus aureus and Pseudomonas aeruginosa. Both dressings are shown, microcalorimetrically, to have the capacity to kill these common wound pathogens within 1-2 h of contact. A dose-response study was conducted with the AQUACEL Ag dressing. Microcalorimetry is shown to be rapid, simple and effective in the study of the antimicrobial properties of gel forming wound dressings.     

Differential cytotoxicity of Mn(II) and Mn(III): special reference to mitochondrial [Fe-S] containing enzymes.

Manganese (Mn)-induced neurodegenerative toxicity has been associated with a distorted iron (Fe) metabolism at both systemic and cellular levels. In the current study, we examined whether the oxidation states of Mn produced differential effects on certain mitochondrial [Fe-S] containing enzymes in vitro. When mitochondrial aconitase, which possesses a [4Fe-4S] cluster, was incubated with either Mn(II) or Mn(III), both Mn species inhibited the activities of aconitase. However, the IC(10) (concentration to cause a 10% enzyme inhibition) for Mn(III) was ninefold lower than that for Mn(II). Following exposure of mitochondrial fractions with Mn(II) or Mn(III), there was a significant inhibition by either Mn species in activities of Complex I whose active site contains five to eight [Fe-S] clusters. The dose-time response curves reveal that Mn(III) was more effective in blocking Complex I activity than Mn(II). Northern blotting was used to examine the expression of mRNAs encoding transferrin receptor (TfR), which is regulated by cytosolic aconitase. Treatment of cultured PC12 cells with Mn(II) and Mn(III) at 100 microM for 3 days resulted in 21 and 58% increases, respectively, in the expression of TfR mRNA. Further studies on cell growth dynamics after exposure to 25-50 microM Mn in culture media demonstrated that the cell numbers were much reduced in Mn(III)-treated groups compared to Mn(II)-treated groups, suggesting that Mn(III) is more effective than Mn(II) in cell killing. In cells exposed to Mn(II) and Mn(III), mitochondrial DNA (mtDNA) was significantly decreased by 24 and 16%, respectively. In contrast, rotenone and MPP+ did not seem to alter mtDNA levels. These in vitro results suggest that Mn(III) species appears to be more cytotoxic than Mn(II) species, possibly due to higher oxidative reactivity and closer radius resemblance to Fe.     

Flavonoid compounds: a review of anticancer properties and interactions with cis‐diamminedichloroplatinum(II)

Flavonoid compounds, especially quercetin and genistein, have antitumor activity. These compounds are cytotoxic to cancer cells but have no or insignificant activity in normal cells. These beneficial properties prompted synthesis of flavonoid synthetic derivatives, e.g., flavopiridol; 5‐amino‐2,3‐fluorophenyl)‐6,8‐difluoro‐7‐methyl‐4H‐1‐benzopyran‐4‐one; B43‐genistein and EGF‐genistein). cis‐DDP (cis‐diamminedichloroplatinum(II)) is one of the most effective drugs used for chemotherapy, but its actions are limited by many side effects. Beneficial synergistic effects of flavonoids (e.g., quercetin, genistein, butein, tannic acid) and cis‐DDP were found in cis‐DDP‐sensitive and resistant cancer cells that resulted in a lower toxicity for cis‐DDP. Further studies focused on the synthesis of complexes of compounds belonging to different groups, e.g., cis‐bis(3‐aminoflavone)dichloroplatinum(II) where introduction of the flavone ligand altered the DNA‐binding properties of the complex as compared to cis‐DDP alone. The beneficial anticancer and antioxidant properties of flavonoids and their synthetic derivatives have prompted further research on the synergistic interactions of these compounds with routinely applied chemotherapeutic drugs, e.g. cis‐DDP. Drug Dev. Res. 63:200–211, 2004. © 2004 Wiley‐Liss, Inc.     

Poly(hydroxybutyrate-hydroxyvalerate) microspheres containing progesterone: preparation, morphology and release properties.

The biodegradable polyesters, poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate-hydroxyvalerate) (PHBV) were investigated for use as sustained delivery carriers of a model drug, progesterone. Spherical microspheres containing the drug were prepared by an emulsion solvent-evaporation method with gelatin as an emulsifier. Methylene chloride as the polymer solvent yielded smoother microspheres than chloroform. The surface texture was also dependent upon the temperature of the preparation and polymer used. Surface crystals were observed when the drug loading was increased beyond 5 per cent w/w. Thermograms of the microspheres did not show an endotherm corresponding to the melting of the drug because the drug dissolved in the melted polymer while heating. The amount of residual solvent in the microspheres (gas chromatographic assay) ranged from 3.4 to 58.4 ppm and was dependent on the processing temperature, concentration of the polymer in the solvent and the polymer composition. In vitro release of the drug was slowest from microspheres made from copolymer containing 9 per cent hydroxyvalerate. A less porous microsphere matrix was formed by this copolymer.     

Chemical and biological properties of indole glucosinolates (glucobrassicins): a review

Glucosinolates are a group of secondary products commonly, but not exclusively, found in plants of the family Cruciferae. They give rise, upon enzymic hydrolysis, to a range of volatile, pungent and physiologically active compounds. Recently, particular attention has been focused upon those that are trytophan-derived--the indole glucosinolates (glucobrassicins). When chemically or enzymically hydrolysed these compounds give rise to a range of involatile indole compounds which have been implicated in the anti-carcinogenic and mixed-function-oxidase stimulatory activities of brassica vegetables. This review details the chemical and physiological properties of indole glucosinolates and their products and suggests possible areas for future research.     

New cytokine dressings. II. Stimulation of oxidative burst in leucocytes in vitro and reduction of viable bacteria within an infected wound.

Recently, we have developed the new dressings containing rhG-CSF or rhGM-CSF. In the present study we investigated either in vitro or in vivo biological activity of the dressings. Human whole blood samples were incubated with extracts from the collagen- or polyurethane-based dressings containing rhG-CSF or/and rhGM-CSF and phagocytic and oxidative metabolic activities were quantitated using Phagotest or Bursttest kits. The results indicate that both the number of phagocyting cells and the intensity of phagocytosis per cell, as well as the level of the oxidative burst in particular, were stimulated by one or both of the cytokines extracted. Next, the experimental skin wounds in mice were infected with 107 CFU of Pseudomonas aeruginosa strain ATCC 27853 and treated locally with the rhG-CSF-containing dressing. The analysis of the biopsies taken from the wounds indicated that in mice treated with the cytokine-containing dressing on the third day the log of CFU per biopsy was 5.0 vs. 6.2 in the control (P<0.001), and on the 8th day was lower than 4 vs. 5.4 in control (P<0.0001). Our findings clearly suggest that the newly designed dressings containing the incorporated CSFs can be used as effective topical cytokine-delivery system in the treatment of bacterial infections in wounds. Copyright