Polymeric colloidal particulate systems: intelligent tools for intracellular targeting of antileishmanial cargos

Limitations of current chemotherapy and future of nanoformulation-based AmB delivery for visceral leishmaniasis-An updated review

Visceral leishmaniasis (VL) is the most lethal of all leishmaniasis diseasesand the second most common parasiticdisease after malaria and,still, categorized as a neglected tropical disease (NTD). According to the latest WHO study, >20 Leishmania species spread 0.7-1.0 million new cases of leishmaniasis each year. VL is caused by the genus, Leishmania donovani (LD), which affects between 50,000 and 90,000 people worldwide each year. Lack of new drug development, increasing drug resistance, toxicity and high cost even with the first line of treatmentof Amphotericin B (AmB), demands new formulation for treatment of VLFurther the lack of a vaccine, allowedthe researchers to develop nanofomulation-based AmB for improved delivery. The limitation of AmB is its kidney and liver toxicity which forced the development of costly liposomal AmB (AmBisome) nanoformulation. Success of AmBisome have inspired and attracted a wide range of AmB nanoformulations ranging from polymeric, solid lipid, liposomal/micellar, metallic, macrophage receptor-targetednanoparticles (NP) and even with sophisticated carbon/quantum dot-based AmBnano delivery systems. Notably, NP-based AmB delivery has shown increased efficacy due to increased uptake, on-target delivery and synergistic impact of NP and AmB. In this review, we have discussed the different forms of leishmaniasis disease and their current treatment options with limitations. The discovery, mechanism of action of AmB, clinical status of AmB and improvement with AmBisome over fungizone (AmB-deoxycholate)for VL treatment was further discussed. At last, the development of various AmB nanoformulation was discussed along with its adavantages over traditional chemotherapy-based delivery.

Nanoparticles Loaded with a New Thiourea Derivative: Development and In vitro Evaluation Against Leishmania amazonensis

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by protozoa of the genus Leishmania. Current treatments are restricted to a small number of drugs that display both severe side effects and a potential for parasites to develop resistance. A new N-(3,4-methylenedioxyphenyl)-N'- (2-phenethyl) thiourea compound (thiourea 1) has shown promising in vitro activity against Leishmania amazonensis with an IC₅₀ of 54.14 μM for promastigotes and an IC₅₀ of 70 μM for amastigotes.

OBJECTIVE

To develop a formulation of thiourea 1 as an oral treatment for leishmaniasis, it was incorporated into Nanoparticles (NPs), a proven approach to provide long-acting drug delivery systems.

METHODS

Poly (D,L-Lactic-co-Glycolic Acid) (PLGA) polymeric NPs containing thiourea 1 were obtained through a nanoprecipitation methodology associated with solvent evaporation. The NPs containing thiourea 1 were characterized for Encapsulation Efficiency (EE%), reaction yield (% w/w), surface charge, particle size and morphology by Transmission Electron Microscopy (TEM).

RESULTS

NPs with thiourea 1 showed an improved in vitro leishmanicidal activity with a reduction in its cytotoxicity against macrophages (CC₅₀>100 μg/mL) while preserving its IC₅₀ against intracellular amastigotes (1.46 ± 0.09 μg/mL). This represents a parasite Selectivity Index (SI) of 68.49, which is a marked advancement from the reference drug pentamidine (SI = 30.14).

CONCLUSION

The results suggest that the incorporation into NPs potentiated the therapeutic effect of thiourea 1, most likely by improving the selective delivery of the drug to the phagocytic cells that are targeted for infection by L. amazonensis. This work reinforces the importance of nanotechnology in the acquisition of new therapeutic alternatives for oral treatments.

Miniaturized neural system for chronic, local intracerebral drug delivery

Recent advances in medications for neurodegenerative disorders are expanding opportunities for improving the debilitating symptoms suffered by patients. Existing pharmacologic treatments, however, often rely on systemic drug administration, which result in broad drug distribution and consequent increased risk for toxicity. Given that many key neural circuitries have sub-cubic millimeter volumes and cell-specific characteristics, small-volume drug administration into affected brain areas with minimal diffusion and leakage is essential. We report the development of an implantable, remotely controllable, miniaturized neural drug delivery system permitting dynamic adjustment of therapy with pinpoint spatial accuracy. We demonstrate that this device can chemically modulate local neuronal activity in small (rodent) and large (nonhuman primate) animal models, while simultaneously allowing the recording of neural activity to enable feedback control.

Nanostructured delivery systems with improved leishmanicidal activity: a critical review

Leishmaniasis is a vector-borne zoonotic disease caused by protozoan parasites of the genus Leishmania, which are responsible for numerous clinical manifestations, such as cutaneous, visceral, and mucocutaneous leishmaniasis, depending on the site of infection for particular species. These complexities threaten 350 million people in 98 countries worldwide. Amastigotes living within macrophage phagolysosomes are the principal target of antileishmanial treatment, but these are not an easy target as drugs must overcome major structural barriers. Furthermore, limitations on current therapy are related to efficacy, toxicity, and cost, as well as the length of treatment, which can increase parasitic resistance. Nanotechnology has emerged as an attractive alternative as conventional drugs delivered by nanosized carriers have improved bioavailability and reduced toxicity, together with other characteristics that help to relieve the burden of this disease. The significance of using colloidal carriers loaded with active agents derives from the physiological uptake route of intravenous administered nanosystems (the phagocyte system). Nanosystems are thus able to promote a high drug concentration in intracellular mononuclear phagocyte system (MPS)-infected cells. Moreover, the versatility of nanometric drug delivery systems for the deliberate transport of a range of molecules plays a pivotal role in the design of therapeutic strategies against leishmaniasis. This review discusses studies on nanocarriers that have greatly contributed to improving the efficacy of antileishmaniasis drugs, presenting a critical review and some suggestions for improving drug delivery.

Miltefosine-loaded lipid nanoparticles: Improving miltefosine stability and reducing its hemolytic potential toward erythtocytes and its cytotoxic effect on macrophages

The toxic effects of miltefosine on the epithelial cells of the gastrointestinal tract and its hemolytic action on erythrocytes have limited its use as an antileishmanial agent. As part of our search for new strategies to overcome the side effects of miltefosine during the treatment of leishmaniasis, we have developed stable miltefosine-loaded lipid nanoparticles in an attempt to reduce the toxic effects of the drug. We have evaluated lipid nanoparticles containing varying amounts of miltefosine and cholesterol, prepared by sonication, in terms of their physicochemical properties, preliminary stability, hemolytic potential toward erythrocytes, and cytotoxicity to macrophages and to promastigote and amastigote forms of Leishmania (L.) chagasi. Miltefosine loading into lipid nanoparticles was 100% for low drug concentrations (7.0 to 20.0mg/mL). Particle size decreased from 143nm (control) to between 43 and 69nm. From fluorescence studies, it was observed that the presence of miltefosine and cholesterol (below 103μM) promoted ordering effects in the phospholipid region of the nanoparticles. The formulation containing 15mg/mL miltefosine was stable for at least six months at 4°C and in simulated gastrointestinal fluids, and did not promote epithelial gastrointestinal irritability in Balb/C mice. When loaded into lipid nanoparticles, the hemolytic potential of miltefosine and its cytotoxicity to macrophages diminished, while its antiparasitic activity remained unaltered. The results suggested that miltefosine-loaded lipid nanoparticles may be promising for the treatment of leishmaniasis and might be suitable for oral and parenteral use.

Bridging small interfering RNA with giant therapeutic outcomes using nanometric liposomes

The scope of RNAi based therapeutics is unquestionable. However, if we dissect the current trend of clinical trials for afore mentioned drug class, some stark trends appear: 1) naked siRNA only exerts influence in topical mode whilst systemic delivery requires a carrier and 2) even after two decades of extensive efforts, not even a single siRNA containing product is commercially available. It was therefore felt that a perspective simplifying the unique intricacies of working with a merger of siRNA and liposomes from a pharmaceutical viewpoint could draw the attention of a wider array of interested researchers. We begin from the beginning and attempt to conduit the gap between theoretical logic and experimental/actual constraints. This, in turn could stimulate the next generation of investigators, gearing them to tackle the conundrum, which is siRNA delivery.

Synergistic enhancement of parasiticidal activity of amphotericin B using copaiba oil in nanoemulsified carrier for oral delivery: an approach for non-toxic chemotherapy

BACKGROUND AND PURPOSE

The aim of this study was to devise a nanoemulsified carrier system (CopNEC) to improve the oral delivery of amphotericin B (AmB) by increasing its oral bioavailability and synergistically enhance its antileishmanial activity with copaiba oil (Cop).

EXPERIMENTAL APPROACH

The AmB encapsulated NEC (CopNEC-AmB) comprised of Cop, d-α-tocopheryl polyethylene glycol 1000 succinate and phosphatidylcholine was prepared by high-pressure homogenization method. Stability study of CopNEC-AmB was carried out in simulated gastric fluid and simulated intestinal fluid. The CopNEC-AmB and plain AmB were compared as regards their in vitro antileishmanial activity, pharmacokinetics, organ distribution and toxicity.

KEY RESULTS

The optimal CopNEC-AmB had a small globule size, low polydispersity index, high ζ potential and encapsulation efficiency. The high resolution transmission electron microscopy illustrated spherical particle geometry with homogeny in their sizes. The optimal CopNEC-AmB was found to be stable in gastrointestinal fluids showing insignificant changes in globule size and encapsulation efficiency. The AUC0-48 value of CopNEC-AmB in rats was significantly improved showing 7.2-fold higher oral bioavailability than free drug. The in vitro antileishmanial activity of CopNEC-AmB was significantly higher than that of the free drug as Cop synergistically enhanced the antileishmanial effect of AmB by causing drastic changes in the morphology of Leishmania parasite and rupturing its plasma membrane. The CopNEC-AmB showed significantly less haemolytic toxicity and cytotoxicity and did not change the histopathology of kidney tissues as compared with AmB alone.

CONCLUSIONS AND IMPLICATIONS

This prototype CopNEC formulation showed improved bioavailability and had a non-toxic synergistic effect on the antileishmanial activity of AmB.

Development of a liposome formulation for improved biodistribution and tumor accumulation of pentamidine for oncology applications

Pentamidine isethionate, widely used for the treatment of parasitic infections, has shown strong anticancer activity in cancer cells and models of melanoma and lung cancer. Systemic administration of pentamidine is associated with serious toxicities, particularly renal, affecting as many as 95% of patients (O'Brien et al., 1997). This work presents the development of a liposome pentamidine formulation for greater tumor accumulation and lower drug exposure to vulnerable tissues. Liposomes formulated with saturated/unsaturated phospholipids of different chain lengths, varying cholesterol content, and surface PEG were explored to understand the effects of such variations on drug release, encapsulation efficiency, stability and in vivo performance. Saturated phospholipids with longer chain lengths, higher cholesterol content and PEG resulted in greater stability. The optimal formulation obtained showed significantly lower clearance rate (3.6 ± 1.2 mL/h/Kg) and higher AUC0-inf (348 ± 31 μmol/L × h) in vivo when compared to free drug (414 ± 138 mL/h/Kg and 2.58 ± 0.74 μmol/L × h, respectively). In tumor-bearing mice, liposomal delivery decreased kidney drug levels by up to 5-fold at 6 and 24h post-administration. Tumor drug exposure was up to 12.7-fold greater with liposomal administration compared to free drug. Overall, the liposomal pentamidine formulation developed has significant potential for the treatment of solid tumors.

Targeted chemotherapy of visceral leishmaniasis by lactoferrin-appended amphotericin B-loaded nanoreservoir: in vitro and in vivo studies

Aim: Exploitation of lactoferrin-appended amphotericin B bearing nanoreservoir (LcfPGNP-AmB) for targeted eradication of Leishmania donovani. Materials & methods: LcfPGNP-AmB was architechtured through ionic adsorption of lactoferrin over core poly (d,l-lactide-co-glycolide) nanoparticles and characterized. Anti-Leishmania activity in visceral leishmaniasis models, immunomodulatory potential, biodistribution and toxicity profile were also assessed. Results: LcfPGNP-AmB (size, 196.0 ± 5.28 nm; zeta-potential, +21.7 ± 1.52 mV; encapsulation efficiency, ∼89%) showed reduced toxicity, increased protective proinflammatory mediators expression and down-regulation of disease-promoting cytokines. Biodistribution study illustrated preferential accumulation of LcfPGNP-AmB in liver and spleen. LcfPGNP-AmB showed augmented antileishmanial activity by significantly reducing (∼88%) splenic parasite burden of infected hamsters, compared with commercial-formulations. Conclusion: Superior efficacy, desired stability and reliable safety of cost-effective LcfPGNP-AmB, suggest its potential for leishmaniasis therapeutics.

Antigen presenting cells targeting and stimulation potential of lipoteichoic acid functionalized lipo-polymerosome: a chemo-immunotherapeutic approach against intracellular infectious disease

Antigen presenting cells (APC) are well-recognized therapeutic targets for intracellular infectious diseases, including visceral leishmaniasis. These targets have raised concerns regarding their potential for drug delivery due to overexpression of a variety of receptors for pathogen associated molecular pathways after infection. Since, lipoteichoic acid (LTA), a surface glycolipid of Gram-positive bacteria responsible for recognition of bacteria by APC receptors that also regulate their activation for pro-inflammatory cytokine secretion, provides additive and significant protection against parasite. Here, we report the nanoarchitechture of APC focused LTA functionalized amphotericin B encapsulated lipo-polymerosome (LTA-AmB-L-Psome) delivery system mediated by self-assembly of synthesized glycol chitosan-stearic acid copolymer (GC-SA) and cholesterol lipid, which can activate and target the chemotherapeutic agents to Leishmania parasite resident APC. Greater J774A and RAW264.7 macrophage internalization of FITC tagged LTA-AmB-L-Psome compared to core AmB-L-Psome was observed by FACSCalibur cytometer assessment. This was further confirmed by higher accumulation in macrophage rich liver, lung and spleen during biodistribution study. The LTA-AmB-L-Psome overcame encapsulated drug toxicity and significantly increased parasite growth inhibition beyond commercial AmB treatment in both in vitro (macrophage-amastigote system; IC50, 0.082 ± 0.009 μg/mL) and in vivo (Leishmania donovani infected hamsters; 89.25 ± 6.44% parasite inhibition) models. Moreover, LTA-AmB-L-Psome stimulated the production of protective cytokines like interferon-γ (IFN-γ), interleukin-12 (IL-12), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase and nitric oxide with down-regulation of disease susceptible cytokines, like transforming growth factor-β (TGF-β), IL-10, and IL-4. These data demonstrate the potential use of LTA-functionalized lipo-polymerosome as a biocompatible lucrative nanotherapeutic platform for overcoming toxicity and improving drug efficacy along with induction of robust APC immune responses for effective therapeutics of intracellular diseases.

Overexpressed Macrophage Mannose Receptor Targeted Nanocapsules- Mediated Cargo Delivery Approach for Eradication of Resident Parasite: In Vitro and In Vivo Studies

PURPOSE

Since, Leishmania protozoans are obligate intracellular parasites of macrophages, an immunopotentiating macrophage-specific Amphotericin B (AB) delivery system would be ideally appropriate to increase its superiority for leishmaniasis treatment and to eliminate undesirable toxicity. Herein, we report AB entrapped mannose grafted chitosan nanocapsules (MnosCNc-AB) that results in effective treatment of visceral leishmaniasis, while also enhancing L. donovani specific T-cell immune responses in infected host.

METHODS

MnosCNc-AB were prepared via synthesized mannosylated chitosan deposition on interface of oil/water nanoemulsion intermediate and were characterized. J774A.1 macrophage uptake potential, antileishmanial activity and immunomodulatory profile were evaluated in hamster. Tissue localization, biodistribution and toxicity profile were also investigated.

RESULTS

MnosCNc-AB had nanometric size (197.8 ± 8.84 nm), unimodal distribution (0.115 ± 0.04), positive zeta potential (+31.7 ± 1.03 mV) and 97.5 ± 1.13% cargo encapsulation efficiency. Superior macrophage internalization of mannosylated chitosan nanocapsules compared to unmodified chitosan nanocapsules was observed by fluorescence-based assessment, further confirmed by rapid blood clearance and, greater localization and higher accumulation in macrophage rich liver and spleen. While, MnosCNc-AB mediated cargo distribution to kidney decreased. Augmented in vitro antileishmanial activity and in vivo pro-inflammatory mediator's expression were observed with MnosCNc-AB, led to significant reduction (∼90%) in splenic parasite burden.

CONCLUSIONS

Results demonstrated that mannose ligand grafted chitosan nanocapsules could improve selective delivery of AB into macrophages via interactions with overexpressed mannose receptors thus reduce undesirable toxicity. Study provides evidence for MnosCNc-AB potential to leishmaniasis therapeutics and presents valuable therapeutic strategies for combating chronic macrophage-resident microbial infections.

Drug delivery systems, CNS protection, and the blood brain barrier

Present review highlights various drug delivery systems used for delivery of pharmaceutical agents mainly antibiotics, antineoplastic agents, neuropeptides, and other therapeutic substances through the endothelial capillaries (BBB) for CNS therapeutics. In addition, the use of ultrasound in delivery of therapeutic agents/biomolecules such as proline rich peptides, prodrugs, radiopharmaceuticals, proteins, immunoglobulins, and chimeric peptides to the target sites in deep tissue locations inside tumor sites of brain has been explained. In addition, therapeutic applications of various types of nanoparticles such as chitosan based nanomers, dendrimers, carbon nanotubes, niosomes, beta cyclodextrin carriers, cholesterol mediated cationic solid lipid nanoparticles, colloidal drug carriers, liposomes, and micelles have been discussed with their recent advancements. Emphasis has been given on the need of physiological and therapeutic optimization of existing drug delivery methods and their carriers to deliver therapeutic amount of drug into the brain for treatment of various neurological diseases and disorders. Further, strong recommendations are being made to develop nanosized drug carriers/vehicles and noninvasive therapeutic alternatives of conventional methods for better therapeutics of CNS related diseases. Hence, there is an urgent need to design nontoxic biocompatible drugs and develop noninvasive delivery methods to check posttreatment clinical fatalities in neuropatients which occur due to existing highly toxic invasive drugs and treatment methods.