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Aqueous PEG-HEMA hydrogel synthesis and protein release for wound dressing applications

Rayment, Erin A. & George, Graeme A. (2006) Aqueous PEG-HEMA hydrogel synthesis and protein release for wound dressing applications. In Australasian Society of Biomaterials Conference, Rotorua, New Zealand.

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, including venous leg ulcers, pressure sores, ischemic ulcers and diabetic foot ulcers, costing upwards of US$ 9 billion to treat. Many wound dressings currently on the market are primarily antimicrobials, e.g. Actisorb Plus (Johnson & Johnson) and Acticoat (Smith & Nephew), which while they control bacterial growth do not attend to potential growth factor deficiencies. In contrast, there are several types of interactive dressings, e.g. Promogran (Johnson & Johnson), which claim to maintain a moist wound environment and interact with cells or matrix proteins in the wound. An advantage of synthetic scaffolds over these animal- and plant-derived products is that they are well-defined and completely pathogen-free.

The ideal candidate for a wound dressing is the hydrogel. Hydrogels are hydrophilic polymer networks which can absorb from 10-20% up to thousands of times their dry weight in water. They can either be chemically stable or have the ability to degrade and ultimately disintegrate, a fact that is often exploited in drug and protein delivery. Copolymers of PEG and 2-hydroxylethyl methacrylate (HEMA) have earlier been claimed for use as a hydrogel for protein release. PHEMA has been used for a number of years in the production of soft contact lenses and intraocular lenses, as it exhibits high biocompatibility and low thrombogenecity. In addition, PHEMA has the imbibed water content properties desirable in hydrogels. PEG is also highly biocompatible and exhibits versatile physical properties.

Aqueous solutions of distilled 2-hydroxylethyl methacrylate (HEMA) (Sigma-Aldrich, Australia) and poly(ethylene glycol) (PEG 10,000 and PEG 20,000) (Sigma-Aldrich, Australia) were prepared in two separate ratios [(50% water, 30% PEG and 20% HEMA) and (50% water, 40% PEG and 10% HEMA)]. They were purged with argon and then irradiated by a 60Co source to give a total dose of 5 KGy, 10 KGy, and 20 KGy respectively.

Un-irradiated and irradiated samples were then analysed by a Perkin Elmer System 2000 NIR FT-Raman. Small samples of copolymers were also immersed in water and weighed at appropriate intervals to give an idea of water uptake into the system. Finally, samples were immersed in various protein solutions of 2 mg/mL bovine serum albumin (BSA) in phosphate buffered saline (PBS) and 2mg/mL BSA in PBS with 12 % w/v PEG 10,000 and 0.22M KCl, respectively. These loaded polymers were then studied using a total protein assay at 37°C to give an idea of protein release.

From solvent extraction it has been shown that PEG is not chemically bound to the crosslinked PHEMA in contrast to the earlier report. Samples prepared with a ratio of 50% water, 40% PEG and 10% HEMA were discounted immediately for their lack of mechanical strength. Water uptake results showed that selected hydrogels could swell to >300% of their original weight and >450% of their volume in water. Protein release was performed to identify differences between the original polymers ("C"), polymers that had been immersed in water and then dried ("C") and these dried polymers that had taken up protein in a solution that contained 12 % w/v PEG 10,000 and 0.22M KCl ("C" + PEG/KCl). Results showed that the original polymers were superior in both cases.

This method of hydrogel synthesis appears to be promising for the generation of wound dressings. A complete conversion of the HEMA monomer can be easily obtained and the resulting copolymers appear cool and flexible to touch. Finally, protein release was superior in these novel polymers as compared to PHEMA alone.

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ID Code: 5700
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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