Simultaneous viscoelasticity and sprayability in antimicrobial acetic acid-alginate fluid gels

Acetic acid is a promising alternative to antibiotics for topical applications, particularly burn wounds, however its site specificity and retention are impaired by poor material properties. In this study, acetic acid was investigated as both the gelling agent and antimicrobial active in alginate fluid gels. The formed microstructure was found to be directly dependent on acetic acid concentration, leading to highly tuneable material properties. At clinically relevant concentrations of 2.5-5 % acetic acid, the fluid gels were elastically dominated at rest, with viscosities up to 7 orders of magnitude greater than acetic acid alone. These material properties imparted long term surface retention and microparticle barrier function, not seen with either acetic acid or alginate solutions. Most notably, sprayability was enhanced simultaneously with the increased viscosity and elasticity due to the introduction of a discretised microstructure, leading to a remarkable tenfold increase in spray coverage. Formulation was found not to inhibit antimicrobial activity, despite the less acidic pH, with common burn wound pathogens Staphylococcus aureus and Pseudomonas aeruginosa being equally susceptible to the fluid gels as to acetic acid solutions.