Development and characterization of an amphotericin B - loaded nanoemulsion applied to Candida auris biofilms control

Abstract

Nanoemulsions (NE) belong to the class of emulsions widely used in the scientific field in order to improve drugs bioavailability and selectivity, especially in the control of microbial resistance. Among the resistant microorganisms, Candida auris is highly resistant to conventional treatments and has caused serious public health concerns. The amphotericin B (AmB) has shown good antifungal activity, however, with a considerable level of toxicity. In light of this, the incorporation of AmB in NE comprises an efficient strategy to overcome side effects besides enhancing its action. Furthermore, NE can be lower cost and less complex to develop compared to other systems already available. This work aimed to design, characterize and evaluate AmB-loaded NE (denominated NEA) against C. auris biofilm. NE were prepared by a mixture of phosphate buffered saline (PBS - aqueous phase), cholesterol and sunflower oil (oil phase) and Polyoxyethylene (20) cetyl ether (Brij® 58) and soy phosphatidylcholine (surfactants). The proposed nanosystem was successfully characterized and the encapsulation efficiency (EE) and release assays were evaluated using HPLC. NEA was applied against developing and mature biofilms formed by C. auris CDC B11903. The characterization assays results showed a clear liquid NE with the size ranging from 44 to 47 nm, good uniformity and zeta potential (ZP) ranging from −3.77 to −3.56 mV. The thermal data analysis confirmed that the drug incorporation did not change the NE profile. Cryo-TEM images exhibited spherical shape with nanostructures well dispersed with an average size of 40 nm. NEA EE ranged from 69 to 17%, having a slower release potential compared to free AmB. In vitro studies performed against C. auris biofilms displayed promising results with high antibiofilm capacity regarding to the growth control (with no treatment). Considering the aforementioned, NE displayed essential characteristics for an effective nanocarrier, exhibiting good EE, slow AmB release and activity against C. auris biofilms.