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Analysis of aqueous PEG-HEMA wound dressing synthesis, protein release and biocompatibility in a three-dimensional skin model

Rayment, Erin A., Upton, Zee, & George, Graeme A. (2006) Analysis of aqueous PEG-HEMA wound dressing synthesis, protein release and biocompatibility in a three-dimensional skin model. In Australian Society of Medical Research Conference, Brisbane, Australia.

Abstract

Chronic wounds are an important and costly medical issue. American figures show that more than four million people each year are affected by chronic wounds, costing more than US$ 9 billion to treat. Many wound dressings on the market are primarily antimicrobials, e.g. Acticoat (Smith & Nephew), which while controlling bacterial growth, do not address other imbalances in the chronic wound. The ideal candidate for a wound dressing is the hydrogel – a hydrophilic polymer network, which can absorb from 10-20% up to thousands of times their dry weight in water. Poly(2-hydroxylethyl methacrylate) (PHEMA) has been used extensively in the production of soft contact lenses, as it exhibits high biocompatibility and low thrombogenecity. Poly(ethylene glycol) (PEG) is also highly biocompatible and exhibits versatile physical properties. In view of this, we have evaluated the potential of PEG-HEMA as a potential wound dressing.

Aqueous solutions of distilled HEMA (Sigma-Aldrich, Australia) and PEG (20,000) (Sigma-Aldrich, Australia) were prepared (50% water, 30% PEG and 20% HEMA) alongside PHEMA alone (71.4% water and 28.6% HEMA). They were purged with argon and irradiated by a 60Co source to give a total dose of 5 KGy and 10 KGy respectively. Polymer samples were characterised by NIR FT-Raman spectroscopy, water uptake and solvent uptake. Next, samples were immersed in solutions of 2 µg/mL horseradish peroxidase (HRP) in both water and 0.22 M KCl, respectively. These loaded polymers were then studied through the release of HRP and subsequent catalytic conversion of 2,2'-Azinobis [3-ethylbenzothiazoline-6-sulfonic acid]-diammonium salt (ABTS). Cell assays were also performed to study the potential toxicity of these wound dressings, along with a commercially available dressing (Allevyn™, Smith & Nephew). Using a human skin equivalent (HSE) model, the skin substitutes were topically exposed to the wound dressings for a seven day period, followed by histological and immunohistochemical staining.

Aqueous crosslinked polymers of HEMA and PEG were prepared successfully. The FT-Raman spectroscopy results showed that doses as low as 5 KGy allowed complete monomer conversion, while uptake studies indicated that these polymers were hydrogels that could swell to over 250% of their original weight with water. From solvent extraction, it was also demonstrated that PEG is not chemically bound to the crosslinked PHEMA, but affected protein uptake and release. Importantly, HRP release from the loaded polymers indicated that this protein could be taken up into the hydrogels and also released in a controlled manner. In optimal combinations, approximately 700 ng of HRP was released over a week, which corresponds well to the physiologically relevant amount of growth factors successfully used in a recent wound healing study in our laboratory. Finally, these novel polymers appear to be biologically inert on a HSE in an unwounded model, as determined by histological and immunohistochemical staining.

Taken together, the data suggest that this method of hydrogel synthesis appears to be promising for the generation of novel wound dressings. Future studies will involve placing the hydrogels containing growth factors on a wounded HSE to identify whether their release enhances the wound healing process. In terms of its application to chronic wounds, concurrent studies using chronic wound fluid are directed at identifying the key proteases responsible for the increased levels of proteolytic activity in this environment, since ultimately we also intend to evaluate the incorporation of protease inhibitors in this novel wound dressing.

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ID Code: 5699
Item Type: Conference Paper
Additional Information: For more information please contact the author: g.george@qut.edu.au
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > CLINICAL SCIENCES (110300) > Dermatology (110304)
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2006 (please consult author)
Deposited On: 01 Dec 2006
Last Modified: 15 Jan 2009 17:16

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