This study describes the antileishmanial efficacy of the novel drug formulation of amphotericin B (AmB) attached to functionalized carbon nanotubes (f-CNTs) and compares it with AmB.

f-CNTs were prepared in a two-step chemical carboxylation and amidation process. The AmB was then attached to make f-CNT–AmB and its construction was confirmed by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The cytotoxicity of the constructed compound, f-CNT–AmB, was assessed in vitro using the J774A.1 macrophage cell line and in vivo using healthy BALB/c mice. Antileishmanial activity of AmB and f-CNT–AmB was assessed in vitro using a macrophage (J774A.1 cell line) model of Leishmania donovani infection. Antileishmanial activity was assessed in vivo by comparing the parasite load of hamsters treated with a 5 day course of AmB, f-CNTs or f-CNT–AmB initiated at 30 days after infection with L. donovani parasites.

The FTIR spectroscopy and TEM data demonstrate the successful attachment of AmB to f-CNTs. The in vitro cytotoxicity of AmB, f-CNTs and f-CNT–AmB was measured by the cytotoxic concentration required to kill 50% of the cells: 0.48 ± 0.06 μg/mL; 7.31 ± 1.16 μg/mL; 0.66 ± 0.17 μg/mL, respectively, in the J774A.1 cell line. The in vivo toxicity assessment of the compounds in BALB/c mice revealed no hepatic or renal toxicity. Against intracellular amastigotes the in vitro antileishmanial efficacy of f-CNT–AmB was significantly higher than that of AmB (IC₅₀ 0.00234 ± 0.00075 μg/mL versus 0.03263 ± 0.00123 μg/mL; P ≤ 0.0001). The percentage inhibition of amastigote replication in hamsters treated with f-CNT–AmB was significantly more than that with AmB (89.85% ± 2.93% versus 68.97% ± 1.84%; P = 0.0004).

The results of these experiments clearly demonstrate that f-CNT–AmB has significantly greater antileishmanial efficacy than AmB and had no significant cytotoxic effects.