Design of Micelle Nanocontainers Based on PDMAEMA-b-PCL-b-PDMAEMA Triblock Copolymers for the Encapsulation of Amphotericin B

Abstract

The clinical application of amphotericin B (AmB), a broad spectrum antifungal agent, is limited by its poor solubility in aqueous medium and also by its proven renal toxicity. In this work, AmB was encapsulated in micelles obtained from the self-assembly of PDMAEMA-b-PCL-b-PDMAEMA triblock copolymers. The amount of encapsulated AmB depended on the copolymer composition, and short blocks of polycaprolactone (PCL) and poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) showed better performance. All the studied formulations exhibited a controlled release of AmB along 150 h. The formulations presented reduced hemotoxicity while maintaining antifungal activities against Candida albicans, Candida krusei, and Candida glabrata comparable with free AmB. A reduction on the hemotoxicity was found to be due to the slow release and subsequent low aggregation achieved with the use of polymer micelle nanocontainers.

Keywords: amphotericin B; antifungal agent; hemotoxicity; micelles.

Scheme 1

Structure of PDMAEMA-b-PCL-b-PDMAEMA amphiphilic triblock copolymers

Fig. 1

Particle size distribution of micelles at pH 5.0 for the set of samples obtained from PCL of a 2 and b 10 kDa. TEM images of the micelles obtained from representative samples: c P2D2 and d P10D2 supported on a Formvar® coated copper grid

Fig. 2

UV-Vis spectrum of AmB dissolved in PBS and DMSO, and AmB encapsulated in micelles obtained from representative copolymer samples P2D2 and P10D2

Fig. 3

Release profiles of AmB under sink conditions achieved by the incorporation of SDS in the release medium from AmB encapsulated in micelles obtained from copolymers containing a segment of PCL of a 2 and b 10 kDa

Fig. 4

Effect of PDMAEMA block length on the release profiles in formulations obtained from PDMAEMA-b-PCL-b-PDMAEMA with different lengths of PCL: a 2 and b 10 kDa (n = 3)

Scheme 2

Encapsulation of AmB in micelles obtained from copolymers containing PCL of 2 and 10 kDa

Fig. 5

Effect of the composition of PDMAEMA-b-PCL-b-PDMAEMA and concentration of AmB on the hemolytic activity (n = 3)

Fig. 6

Hemolytic activity of AmB encapsulated in micelles obtained from PDMAEMA-b-PCL-b-PDMAEMA with different lengths of PCL: a 2 and b 10 kDa (n = 3)

Fig. 7

a Representative picture showing the inhibition halos observed for C. albicans using AmB dissolved in DMSO and encapsulated in micelles obtained from the evaluated copolymer; the final concentration of AmB in each cylinder was 9 ppm. Inhibition halos of b C. albicans, c C. krusei, and d C. glabrata obtained at four different concentrations of free and encapsulated AmB