A Functional Wound Dressing as a Potential Treatment for Cutaneous Leishmaniasis

The novel treatments based on tissue engineering, cell therapy and nanotechnology for cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a global public health issue. Conventional treatments have substantial costs, side effects, and parasite resistance. Due to easy application and inexpensive cost, topical treatment is the optimal approach for CL. It could be used alone or with systemic treatments. Electrospun fibers as drug release systems in treating skin lesions have various advantages such as adjustable drug release rate, maintaining appropriate humidity and temperature, gas exchange, plasticity at the lesion site, similarity with the skin extracellular matrix (ECM) and drug delivery with high efficiency. Hydrogels are valuable scaffolds in the treatment of skin lesions. The important features of hydrogels include preserving unstable drugs from degradation, absorption of wound secretions, high biocompatibility, improving the re-epithelialization of the wound and preventing the formation of scars. One of the issues in local drug delivery systems for the skin is the low permeability of drugs in the skin. Polymeric scaffolds that are designed as microneedle patches can penetrate the skin and overcome this challenge. Also, drug delivery using nanocarriers increases the effectiveness of drugs in lower and more tolerable doses and reduces the toxicity of drugs. The application of cell therapy in the treatment of parasitic and infectious diseases has been widely investigated. The complexity of leishmaniasis treatment requires identifying new treatment options like cell therapy to overcome the disease. Topics investigated in this study include drug delivery systems based on tissue engineering scaffolds, nanotechnology and cell therapy-based studies to reduce the complications of CL.

Immunoinformatics Approach to Design a Multi-Epitope Vaccine against Cutaneous Leishmaniasis

Cutaneous Leishmaniasis (CL), a neglected vector-borne disease caused by protozoan parasite Leishmania major (L. major), is a major public health concern, and the development of new strategies to reduce the disease incidence has become a top priority. Advances in immunoinformatics and in-silico epitope prediction could be a promising approach to designing a finest vaccine candidate. In this study, we aimed to design a peptide-based vaccine against CL using computational tools and identified ten B-cell-derived T-cell epitopes from the glycoprotein gp63 of L. major. All of the potential immunodominant epitopes were used to design a vaccine construct along with a linker and an adjuvant at the N-terminal for enhancing its immunogenicity. Additionally, many characteristics of the proposed vaccine were examined, and it was confirmed to be non-allergenic, non-toxic, and thermally stable. To assess the vaccine interaction with the innate immune toll-like receptor-4 (TLR-4), a 3D structure of the vaccine construct was developed. Molecular docking and molecular dynamic simulation were used to confirm the binding and to assess the stability of the vaccine-TLR4 complex and interactions, respectively. In conclusion, our multi-epitope vaccine will provide a gateway to analyze the protein function of a potential vaccine candidate against CL.

Cutaneous/Mucocutaneous Leishmaniasis Treatment for Wound Healing: Classical versus New Treatment Approaches

Cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (ML) show clinical spectra that can range from a localized lesion (with a spontaneous healing process) to cases that progress to a generalized systemic disease with a risk of death. The treatment of leishmaniasis is complex since most of the available drugs show high toxicity. The development of an effective topical drug formulation for CL and ML treatment offers advantages as it will improve patient’s compliance to the therapy given the possibility for self-administration, as well as overcoming the first pass metabolism and the high costs of currently available alternatives. The most common dosage forms include solid formulations, such as membranes and semi-solid formulations (e.g., ointments, creams, gels, and pastes). Topical treatment has been used as a new route of administration for conventional drugs against leishmaniasis and its combinations, as well as to exploit new substances. In this review, we discuss the advantages and limitations of using topical drug delivery for the treatment of these two forms of leishmaniasis and the relevance of combining this approach with other pharmaceutical dosage forms. Emphasis will also be given to the use of nanomaterials for site-specific delivery.

Models for cytotoxicity screening of antileishmanial drugs: what has been done so far?

A growing number of studies have demonstrated the in vitro potential of an impressive number of antileishmanial candidates in the past years. However, the lack of uniformity regarding the choice of cell types for cytotoxicity assays may lead to uncomparable and inconclusive data. In vitro assays relying solely on non-phagocytic cell models may not represent a realistic result as the effect of an antileishmanial agent should ideally be presented based on its cytotoxicity profile against reticuloendothelial system cells. In the present review, we have assembled studies published in the scientific literature from 2015 to 2021 that explored leishmanicidal candidates, emphasising the main host cell models used for cytotoxicity assays. The pros and cons of different host cell types as well as primary cells and cell lines are discussed in order to draw attention to the need to establish standardised protocols for preclinical testing when assessing new antileishmanial candidates.

Nanomedicine-based strategies to improve treatment of cutaneous leishmaniasis

Nanomedicine strategies were first adapted and successfully translated to clinical application for diseases, such as cancer and diabetes. These strategies would no doubt benefit unmet diseases needs as in the case of leishmaniasis. The latter causes skin sores in the cutaneous form and affects internal organs in the visceral form. Treatment of cutaneous leishmaniasis (CL) aims at accelerating wound healing, reducing scarring and cosmetic morbidity, preventing parasite transmission and relapse. Unfortunately, available treatments show only suboptimal effectiveness and none of them were designed specifically for this disease condition. Tissue regeneration using nano-based devices coupled with drug delivery are currently being used in clinic to address diabetic wounds. Thus, in this review, we analyse the current treatment options and attempt to critically analyse the use of nanomedicine-based strategies to address CL wounds in view of achieving scarless wound healing, targeting secondary bacterial infection and lowering drug toxicity.

Rational Design of Immunomodulatory Hydrogels for Chronic Wound Healing

With all the advances in tissue engineering for construction of fully functional skin tissue, complete regeneration of chronic wounds is still challenging. Since immune reaction to the tissue damage is critical in regulating both the quality and duration of chronic wound healing cascade, strategies to modulate the immune system are of importance. Generally, in response to an injury, macrophages switch from pro-inflammatory to an anti-inflammatory phenotype. Therefore, controlling macrophages' polarization has become an appealing approach in regenerative medicine. Recently, hydrogels-based constructs, incorporated with various cellular and molecular signals, have been developed and utilized to adjust immune cell functions in various stages of wound healing. Here, the current state of knowledge on immune cell functions during skin tissue regeneration is first discussed. Recent advanced technologies used to design immunomodulatory hydrogels for controlling macrophages' polarization are then summarized. Rational design of hydrogels for providing controlled immune stimulation via hydrogel chemistry and surface modification, as well as incorporation of cell and molecules, are also dicussed. In addition, the effects of hydrogels' properties on immunogenic features and the wound healing process are summarized. Finally, future directions and upcoming research strategies to control immune responses during chronic wound healing are highlighted.

Unveiling the Amphotericin B Degradation Pathway and Its Kinetics in Lipid-Based Solutions

The purpose of this work was to determine the degradation pathway of Amphotericin B (AmB) and its kinetics in lipid-based solutions. Mixtures of AmB in lipophilic solvent media were stored under different conditions, such as surface area, temperature, light exposure, presence of antioxidants and other co-solutes. AmB was quantified by HPLC and UV-Vis spectrometry. Empirical models were proposed, and degradation rate constants were estimated by nonlinear regression. The HPLC method was precise and accurate with linearity from 4.45 to 52.0 nM. Surface area studies revealed that adsorption to glass did not affect AmB loss. Unsaturated oils and methanol better preserved AmB compared to medium chain-triglyceride. Temperature increased AmB loss in a nonlinear behavior and the presence of antioxidants reduced its degradation. Under dark conditions, autoxidation was the predominant degradation pathway of AmB in oil, which undergoes a complex degradation. Under light exposure, photo-oxidation accounted for AmB loss, which appeared to be of pseudo-first order. AmB oily samples should be preferably stored in glass vials protected from light with the addition of antioxidants. Furthermore, this work encourages further investigation in other media for future complex modeling and estimation of AmB degradation and kinetics in lipid-based formulations.

Molecular modeling and simulation study of homoserine kinase as an effective leishmanial drug target

Leishmaniasis is a tropical neglected disease that imposes major health concerns in many endemic countries worldwide and requires urgent attention to the identification of new drug targets as well as drug candidates. In the current study, we propose homoserine kinase (HSK) inhibition as a strategy to induce pathogen mortality via generating threonine deficiency. We introduce a homology-based molecular model of leishmanial HSK that appears to possess all conserved structural as well as functional features in the GHMP kinase family. Furthermore, 200 ns molecular dynamics data of the enzyme in open and closed state attempts to provide the mechanistic details involved in the substrate as well as phosphate binding to this enzyme. We discuss the structural and functional significance of movements involved in various loops (motif 1, 2, 3) and lips (upper and lower) in the transition of leishmanial HSK from closed to open state. Virtual screening data of more than 40,000 compounds from the present investigation tries to identify a few potential HSK inhibitors that possess important features to act as efficient HSK inhibitors. These compounds can be considered an effective starting point for the identification of novel drug-like scaffolds. We hope the structural wealth that is offered in this report will be utilized in designing competent experimental and therapeutic interventions for leishmaniasis management. Graphical abstract.

Antifungal and Antiparasitic Drug Delivery

Fungal and parasitic diseases affect more than a billion people across the globe, one-sixth of the world’s population, mostly located in developing countries. The lack of effective and safer treatments combined with a deficient diagnosis lead to serious chronic illness or even death. There is a mismatch between the rate of drug resistance and the development of new medicines. Formulation of antifungal and antiparasitic drugs adapted to different administration routes is challenging, bearing in mind their poor water solubility, which limits their bioavailability and efficacy. Hence, there is an unmet clinical need to develop vaccines and novel formulations and drug delivery strategies that can improve the bioavailability and therapeutic effect by enhancing their dissolution, increasing their chemical potency, stabilising the drug and targeting high concentration of drug to the infection sites. This Editorial regards the ten research contributions presented in the Special Issue “Antifungal and Antiparasitic Drug Delivery”.

Development and Characterization of a Semi-Solid Dosage Form of Meglumine Antimoniate for Topical Treatment of Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) is treated with painful intralesional injections of meglumine antimoniate (MA). With the aim of developing an alternative topical treatment for CL, a gel-based formulation with 30% MA was prepared and its physicochemical properties, stability and rheological behavior were studied. The following were assessed: drug release on propylene hydrophilic membranes ex vivo human skin permeation, tolerance in healthy volunteers, cytotoxicity in three cell lines and anti-leishmanial activity against Leishmania infantum promastigotes and amastigotes. The MA gel formulation was found to have suitable pH, and good spreadability and stability. Low quantities of pentavalent antimony (Sb^V) were observed in release and permeation tests, whereas retention was high in both non-damaged and damaged skin (71,043.69 ± 10,641.57 and 10,728 ± 2254.61 µg/g/cm² of Sb^V, respectively). The formulation did not have a toxic effect on the cell lines, and presented lower Sb^V IC₅₀ values against amastigotes (15.76 ± 4.81 µg/mL) in comparison with the MA solution. The high amount of drug retained in the skin and the Sb^V IC₅₀ values obtained suggest that this semi-solid dosage form has potential as an alternative treatment of CL.