Biomimetic
hydrogels with "built-in" antimicrobial properties can significantly
decrease the infection risks posed by wounds.
Hydrogels
are molecule networks that hold water within their grid. Antimicrobial
hydrogels can be produced by mixing with or attaching antimicrobial components
to a polymer gel. Researchers at the Hebei University of Technology, Tianjin
(China), Radboud University, Nijmegen (the Netherlands), and the University of
Queensland, Brisbane (Australia) chose an alternative route and used photodynamic
antimicrobial chemotherapy as their model. In this technique, photosensitizers
enter an excited state when irradiated with light. Through a non-radiative
transition, the photosensitizer enters a different, long-lived excited state.
The transition can transfer energy to oxygen molecules, forming highly reactive
oxygen species that kill microbes.
To
date, synthetic gels
with photodynamic antimicrobial activity have been neither biocompatible nor
biodegradable. Products from biological sources, in contrast, harbor the risk
of contamination or immune reactions and deliver results that are difficult to
reproduce.
The
team overcame this challenge by using fully synthetic hydrogels with biomimetic
properties, which are properties that mimic biological systems. They selected a
polymer with a helical backbone (polyisocyanide with grafted ethylene glycol
chains) that forms porous, highly biocompatible hydrogels with a thread-like
architecture that resembles the structures and mechanical properties of biogels
based on collagen and fibrin.
The
researchers combined this type of hydrogel with a photosensitizer based on a polythiophene.
In solution it forms disordered clumps and absorbs violet light. Incorporation
into the spiral-shaped regions of the hydrogel forces the polythiophenes into a
straight, linear configuration. In this form, the absorption is significantly
stronger and shifted into the red region of the spectrum. This is preferable
because red light can penetrate deeper and causes less bleaching of the
pigment.
The
researchers thus obtained a gel with outstanding antimicrobial power against
bacteria, such as Escherichia coli and Bacillus subtilis, as well as fungi like
Candida albicans. This could be a starting point for making wound dressings
with "built-in infection stoppers." The advantages of this method of
fighting pathogens: it is non-invasive and its effect is controllable both in
location and duration. Even antibiotic-resistant bacteria can be killed and the
risk of causing new resistances is much lower.
See:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)
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