Leishmaniasis, a neglected vector-borne parasitic infection caused by various species of the genus Leishmania, belonging to the trypanosomatidae family among protozoa, poses a significant global health challenge, with over 20 species contributing to a spectrum of diseases characterized by protean manifestations [1]. The primary mode of transmission involves phlebotomine sandflies [2], encompassing both anthroponotic and zoonotic cycles, while alternate routes, such as human-to-human transmission through infected needles, transfusion, or congenital means, underscore the complex dynamics of this parasitic affliction [3]. The sources of transmission, often reliant on canines, rodents, or humans, vary according to the parasite species, the vector genus, and geographical region, adding layers of intricacy to the already multifaceted nature of Leishmania infections [4].

The three main types of Leishmaniasis - visceral or kala-azar leishmaniasis (VL), cutaneous leishmaniasis (CL), and mucocutaneous leishmaniasis (MCL) - impose considerable burdens on affected populations, both in terms of morbidity and mortality [5]. CL, in particular, manifests as a chronic ailment caused by flagellate protozoa of the genus Leishmania [6].

Among therapeutic options, miltefosine (MT) has emerged as a notable contender, gaining approval from the United States Food and Drug Administration (FDA) for the treatment of CL [7]. The precise mechanism of MT's action, initially developed as an anticancer agent, has not well been understood; however, its antileishmanial effect is attributed to its ability to disrupt leishmanial membrane lipids and mitochondrial function [8,9].

Despite its promise, MT faces challenges, including variable effectiveness, cost considerations, adverse effects, and treatment duration [10]. Addressing these limitations is imperative, given the epidemiological impact of Leishmaniasis and the need for safe, effective, and affordable treatment options. Thus, novel techniques, such as nanotechnology in drug delivery, are needed to overcome existing constraints and enhance the therapeutic potential of MT [11].

Nanotechnology, with its ability to manipulate materials at the nanoscale, provides innovative solutions in drug delivery, promising targeted and controlled release of therapeutic agents [[12], [13], [14]]. Regarding Leishmaniasis, employing nanocarriers can potentially enhance drug bioavailability, reduce systemic toxicity, and improve treatment outcomes [15]. Polyethylene glycol (PEG)ylated liposome, liposome nanoparticles coated with PEG, has emerged as a promising nanocarrier for drug delivery due to their biocompatibility, prolonged circulation time, reduced clearance by the reticuloendothelial system (RES), and ability to encapsulate both hydrophilic and hydrophobic drugs [[16], [17], [18]]. In addition, PEG can enhance drug solubility and stability and facilitate targeted delivery to affected tissues, potentially optimizing therapeutic efficacy while minimizing adverse effects [[19], [20], [21]]. Therefore, using PEGylated liposomes to unleash the complete capabilities of MT against CL is an interesting area to explore.

In this study, MT was loaded into PEGylated liposome nanoparticles (MT-PEG-Lip) to develop a therapeutic platform for treating CL caused by Leishmania major (L. major). The nanoformulation was characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and spectrophotometry. In vitro evaluations compared MT-PEG-Lip to standard MT, assessing antileishmanial effects on L. major. Subsequently, In vivo evaluation indicated the potential of the formulation to enhance the efficacy of MT in CL-infected BALB/c mice. In vivo evaluation methods included lesion size measurement, limited dilution assay (LDA), and histopathological studies.