A closer look in the antimicrobial properties of deep eutectic solvents based on fatty acids

Microbial infection is a serious and challenging clinical complication that has attracted widespread interest in last decades. In this context, we present a strategy based on deep eutectic solvents (DES) to explore these unmet medical needs. DES systems based on saturated fatty acids, namely, capric acid (CA), myristic acid (MA), lauric acid (LA) and stearic acid (SA) were produced and fully characterized at a physicochemical level. The thermal characterization results indicate a depression of the melting point in DES form when compared with the starting compounds to near-physiological levels, whereas via polarized optic microscopy insights on the homogeneity/separation of the counterparts were obtained. Regarding, physicochemical properties, temperature also has a great effect on the viscosity of the eutectic systems, the higher the temperature the lower the viscosity observed. The antimicrobial potential of DES systems was evaluated against a broad spectrum of microorganisms. The obtained results show that DES retain the antimicrobial of the counterparts possibly present synergistic effects between components, mainly in the CA:MA formulation. The systems revealed significant antimicrobial activity against the tested Gram-positive bacteria and C. albicans, with the CA:LA system showing the greatest overall inhibitory/bactericidal activity. This system was then used for a biofilm removal/detachment assay where relevant activity is evident against the prementioned organisms and E. coli without need of additional physical force. The obtained results illustrate the potential of saturated fatty acid-based DES when compared with isolated fatty acids as preventive/therapeutic options against microbial infections and/or components of novel thermoresponsive biomedical devices for antibacterial purposes.

This work received funding from Foundation for Science and Tech-nology, through project PTDC/BBB- 490 EBB/1676/2014 – Des.Zyme and post-doctoral grant SFRH/BPD/116779/2016. The authors would also like to acknowledge the financial support by ERC-2016-CoG 725034 (ERC Consolidator Grant Des.solve)