Neat deep eutectic solvents exhibit potent antibiofilm activity: overcoming dilution bias in eutectic solvent antimicrobial assays

AIMS: Chronic wound infections are driven by multidrug‑resistant, biofilm‑forming bacteria that impede antimicrobial penetration and limit therapeutic success. This study aimed to evaluate deep eutectic solvents (DESs) as intrinsically active antimicrobial and antibiofilm agents and to determine how their physicochemical properties influence biological performance. METHODS AND RESULTS: Four DES formulations: choline chloride-lactic acid, choline chloride-malonic acid, betaine-lactic acid, and betaine-malonic acid, were evaluated for antimicrobial and antibiofilm activity against six clinically relevant wound‑associated bacterial strains. All DESs exhibited potent antimicrobial activity, with minimum inhibitory concentrations typically ranging from ~0.2-0.8% (v/v), and achieved near‑complete eradication of mature biofilms at higher concentrations. Temperature‑dependent viscosity and ionic conductivity measurements revealed composition‑dependent transport behaviour. CONCLUSIONS: These findings support a structure-transport-activity relationship, in which hydrogen-bond organisation and ionic mobility are associated with DES antimicrobial potency and highlight their relevance as solvent‑active therapeutic platforms of interest for strategies targeting biofilm-associated infections.