A potential nanotechnology based drug delivery for the treatment of Leishmaniases

Purpose Leishmaniases is a group of diseases caused by protozoan parasites of the genus Leishmania. The estimated number of deaths from visceral leishmaniasis ranges from 20 000 to 50 000 annually. Visceral leishmaniasis is usually fatal within 2 years if left untreated. The most common treatment over the past 50 years has been pentavalent antimonials. Although effective, it has several disadvantages such as the need for parenteral administration, large doses, long treatment, severe toxicity, parasite resistance and variable efficacy. The buparvaquone (BPQ), a drug used for veterinary treatment of theileriosis, showed promising activity against protozoan parasites Leishmania spp. However due to its low aqueous solubility and bioavailability, it has failed in in vivo tests. To overcome these limitations, the use of nanotechnologies has emerged in recent decades, due to its potential advantages: high therapeutic efficacy, improved solubility of lipophilic molecules, reduced toxicity and modified release of the drug. The objectives are to develop, optimize and evaluate the physical and chemical characteristics of nanostructured lipid carriers (NLCs) for BPQ encapsulation. Methods The leishmanicidal activity was evaluated on promastigotes of L. amazonensis, L. brasiliensis and L. infantum. The BPQ solubility in liquid and solid lipid was evaluated using shake flask method. For liquid lipids, the quantification was performed by HPLC, and for solid lipids, the solubility was evaluated by optical microscopy. The NLCs preparation was performed by high-pressure homogenization. A surface response statistical experimental design (20 formulations) was carried out to evaluate the influence of the solid lipid: liquid lipid ratio (SL/LL) and surfactant concentrations (Lutrol&[reg] F68 and Tween&[reg] 80) on the hydrodynamic average diameter (HAD), polydispersity index (PDI) and zeta potential (ZP). Results The IC50 (concentration of an inhibitor where the response is reduced by half) for L. amazonensis, L. brasiliensis and L. infantum were 22.23, 17.68 and 6.59 nM, respectively. The lower IC50 for L. infantum indicates the potential use of the BPQ for visceral leishmaniasis. BPQ showed the highest solubility (10mg/g) in Miglyol&[reg] (esters of caprylic and capric acids) among the LL tested. For the SL screening, Softsan&[reg] 154 has the highest BPQ solubility (1mg/g). The influence of the LL/SL ratio and the surfactant concentration on the HAD can be expressed by a linear model. The lack of fit was not significant (p-value: 0.869 &[alpha]=0.05) and predicted R-squared of 91.04%, which show good suitability of the model. The optimization for HAD showed that lower LS/LL ratios and higher surfactant concentration led to smaller HADs. The formulations prepared for HAD model validation presented observed values of 215.4±3.7 nm and 231.2±2.3 nm and theoretical values of 183.8 to 217.4 nm and 200.8 to 232.4 nm (IC 95%), respectively. All the formulations presented 217.7