Ephemeral biogels to control anti-biofilm agent delivery: From conception to the construction of an active dressing.

Chronic wound colonization by bacterial biofilms is common and can cause various complications. An anti-biofilm strategy was developed around the co-entrapment of a commercially available antiseptic, PHMB (polyhexamethylene biguanide 4mgmL-1), with EDTA (Ethylen diamine tetra acetic acid, 20mM) in a gelatin gel. The two active compounds act synergistically against bacterial biofilms, but their efficiency is strongly reduced (16-fold) when entrapped inside the 5% gelatin gel, and they weaken the mechanical properties (50-fold) of the gel. Increasing the gelatin concentration to 7% allows for good mechanical properties but large diffusional constraints. An active ephemeral gel, a chemical gel with controlled hydrolysis, was conceived and developed. When the ephemeral gel was solubilized after 48h, PHMB delivery increased, leading to good anti-biofilm activity. The various gels were examined over 24 and 48h of contact with P. aeruginosa and S. aureus biofilms, two types of bacterial biofilms frequently encountered in chronic wounds. The ephemeral gel eradicated the dense biofilms (>6.107CFU·cm-2) produced by either single or mixed strains; a similar efficiency was measured for biofilms from strains of both laboratory and clinical origin. The formulation was then adapted to develop a dressing prototype that is active against biofilms and fulfils the requirements of an efficient wound care system.

Synergistic antibiofilm efficacy of various commercial antiseptics, enzymes and EDTA: a study of Pseudomonas aeruginosa and Staphylococcus aureus biofilms.

A multistep strategy was used to generate a combined antibiofilm treatment that could efficiently decrease the biomass of dense biofilms (≥6 × 10(7) CFU/cm(2)). Several compounds that exhibited activity against various targets were tested individually and in combination to search for possible synergistic effects. First, the antibiofilm activity of various commercially available antiseptics was tested on Pseudomonas aeruginosa and Staphylococcus aureus. Second, antiseptics were mixed with ethylene diamine tetra-acetic acid (EDTA), which is an ion chelator that can disturb biofilm organisation, and additive effects on biofilm biomass degradation were found for both strains. Then, enzymes with the ability to destabilise the biofilm matrix by hydrolysing either its proteins or its polysaccharides were used; as expected, they did not decrease bacterial viability but were revealed as efficient biomass reducers. The combination of antiseptics, EDTA and proteases, all at low concentrations, revealed a synergistic effect leading to total eradication of dense biofilms both of P. aeruginosa and S. aureus.

Gelatin-alginate gels and their enzymatic modifications: controlling the delivery of small molecules.

The release of molecules entrapped within biogels is dictated by diffusion laws. Innovative biogel architectures are conceived and tested to control small molecule delivery from gelatin gels. The ionic interactions modulate the release of small molecules. Alginate is then added to gelatin gels and further hydrolyzed; the influence of viscosity is discussed. Next, various mixed gels are compared, such as a gelatin-alginate IPN and the original architecture of an alginate gel entrapped in a gelatin gel with or without a polysaccharidase. The relative influence of ionic interactions and diffusional constraints on the delivery of small charged molecules is explored, and a solution for controlling diffusion is proposed for any situation.