When closure gels: Wound healing

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  • Published: Dec 15, 2013
  • Author: David Bradley
  • Channels: Chemometrics & Informatics
thumbnail image: When closure gels: Wound healing

Dendritic dressing

A Dendritic Thioester Hydrogel Based on Thiol–Thioester Exchange as a Dissolvable Sealant System for Wound Closure

Effective wound closure is vital in an emergency to avoid significant blood loss following injury and to reduce the risk of infection. Of course, temporary closure of a serious wound usually requires it to be opened again once the patient reaches the hospital, but this process can cause damage of its own. Now, researchers in the US have developed a novel dendritic thioester hydrogel that can seal wounds rapidly but be dissolved subsequently to allow the wound to be opened gently if surgery is necessary. Analytical assessment of the associated rheological data demonstrate efficacy.

Researchers working at Boston University and the Beth Israel Deaconess Medical Center in Boston, in Massachusetts, USA, describe details of their wound-repairing gel and the results of tests on human skin, in the journal Angewandte Chemie. The material could save life and limb for anyone living or working in a remote area far from emergency healthcare or in military action. In such scenarios, a temporary wound closure system is often the best option to save lives as it can stem blood loss for several hours. It must be able to stick readily to skin and tissue be easy to apply without causing cross contamination of infectious agents. Finally, a wound-healing agent must be easy to remove in a controlled manner to allow surgeons access to damage tissues so that a more permanent repair can be carried and, of course, any damage to underlying tissues be treated.

Unfortunately, there is no single wound-closure system available for emergency use or otherwise that meets all of these criteria, the researchers explain. Removal of blood-clotting agents or dressings commonly requires cutting and tearing or surgical excision; which can cause more damage to the injured party.

Viscoelasticity and rheology

The team, led by Mark Grinstaff suggests their new wound-closure system based on a synthetic biocompatible gel meets all of the criteria necessary for a modern, alternative approach to injury. The gel is cross-linked through branched thioesters, they explain, thus thiol–thioester exchange can be used to dissolve away the gel when it needs to be removed. In this reaction, a thioester bond reacts with a thiolate anion to produce new thioester and thiolate products. The advantage of this reaction is that it takes place in an aqueous environment under physiological conditions. This type of reaction also occurs in natural biological processes. When the thioester gel is treated with cysteine methyl ester, the thioester bridges are rapidly split and the gel dissolves.

The team, which includes Cynthia Ghobril, Kristie Charoen, Edward Rodriguez and Ara Nazarian, explains further that an open wound can be treated by simply mixing and applying the two requisite starting materials. The gel forms within seconds, sticks well to the skin and remains intact for several days even under normal stresses and strains that a wound might undergo. The measurements on viscoelasticity and rheology support the observations. Of additional clinical benefit, the gel absorbs any liquid exiting the wound and so does not cause a build up of potentially harmful substances that are usually present in conventional dressings. The chemistry of the material allows treatment with cysteine methyl ester to dissolve the gel over the course of thirty minutes or so, which would be sufficient time for the medical staff to cope with any more serious underlying problems that might arise.

Injury claim

To simulate injury to a vein, the researchers filled a section of bovine jugular vein with buffer solution and punctured it. Once the gel was applied, the damaged vein was completely sealed; after dissolution of the gel, the buffer solution flowed out again. Tests on human skin were also carried out to demonstrate strong adhesion and the ease with which the material can be dissolved and removed.

Related Links

Angew Chem, 2013, 52, in press: "A Dendritic Thioester Hydrogel Based on Thiol–Thioester Exchange as a Dissolvable Sealant System for Wound Closure"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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