Can rhamnose-based glycolipids nanoparticles be an alternative to fight biofilms on medical devices?

Biofilm development on medical devices is of particular concern and finding new strategies for preventing surface colonization and infection development are urgent. Antimicrobial biosurfactants such as rhamnolipids (RLs), emerge as one possible solution due their lack of resistance development. Using nanoparticles as delivery systems for these compounds may be a promising alternative in the context of biofilm-infections control. As such, the aim of this study was to encapsulate RLs into chitosan nanoparticles (RLs-NPs), test their antimicrobial activity and their biocompatibility profile.

Blank nanoparticles (b-NPs) and RLs-NPs were prepared by ionic gelation. For particles characterization, zeta potential, size distribution and encapsulation efficiency were performed. Minimal inhibitory concentration and biofilm inhibition ability were evaluated towards Staphylococcus aureus (ATCC 25923). To access NPs cytocompatibility the in vitro tetrazolium dye assay (MTT) and morphology observation were performed with a mouse fibroblastic cell line (L929).

RLs-NPs presented an encapsulation efficiency of 74.2±1.3%, a size ranging from 300 to 400 nm and a zeta potential of  37±1 mV. The minimum inhibitory concentration of RLs-NPs was 130 mg/mL and a 99% biofilm inhibition was achieved with these NPs meaning that their antimicrobial activity is also effective towards sessile bacteria. When compared to control, cell cultures grown in the presence of RLs-NPs presented no significant differences regarding the MTT reduction values and morphology analysis, suggesting that NPs up to 500 mg/mL did not significantly interfere with viability and proliferation.

The results revealed that the RLs-NPs were able to inhibit bacterial growth showing adequate cytocompatibility and might become, after additional studies, a possible approach to fight S. aureus biofilm associated infections.

Acknowledgments: Support for this work was provided by FCT through Portuguese government, PTDC/BTM-SAL/29335/2017 and Pest-UID/DTP/04138/2019