Achieving high antimicrobial activity: Composite alginate hydrogel beads releasing activated charcoal with an immobilized active agent.

New composites based on Ca-alginate hydrogels were produced that release activated charcoal (AC) particles with adsorbed povidone iodine (PVP-I) as a model antimicrobial substance in a physiological-like environment. Composite beads with different alginate (0.5-1.5%w/w) and AC (1-20%w/w) concentrations were analyzed by FE-SEM and characterized regarding textural parameters, swelling, and AC release kinetics. PVP-I was easily adsorbed onto AC particles within the optimized beads (0.5%w/w alginate, 20%w/w AC) as indicated by UV-vis spectroscopy, EDX and FT-IR analyses. The obtained beads have shown strong bactericidal effects against two standard bacterial strains (Staphylococcus aureus and Pseudomonas aeruginosa) and clinical multi-resistant wound isolates (MRSA, Escherichia coli, Pseudomonas aeruginosa, Еnterococcus faecalis and Proteus mirabilis) and, at the same time, exhibited negligible PVP-I desorption in physiological saline solution. Thus, the obtained composites could provide utilization of potent antiseptics such as iodine, in wound dressings, without the concern of systemic absorption.