Praziquantel-lipid nanocapsules: an oral nanotherapeutic with potential Schistosoma mansoni tegumental targeting

Abstract

Purpose: Lipid nanocapsules (LNCs) have shown potential to increase the bioavailability and efficacy of orally administered drugs. However, their intestinal translocation to distal target sites and their implication in pharmacokinetic (PK)-pharmacodynamic (PD) relationships are yet to be elucidated. In this study, the effect of LNCs on the PD activity and pharmacokinetics of praziquantel (PZQ), the mainstay of schistosomiasis chemotherapy, was investigated.

Materials and methods: The composition of LNCs was modified to increase PZQ payload and to enhance membrane permeability. PZQ-LNCs were characterized in vitro for colloidal properties, entrapment efficiency (EE%), and drug release. PD activity of the test formulations was assessed in Schistosoma mansoni-infected mice 7 days post-oral administration of a single 250 mg/kg oral dose. Pharmacokinetics of the test formulations and their stability in simulated gastrointestinal (GI) fluids were investigated to substantiate in vivo data.

Results: PZQ-LNCs exhibited good pharmaceutical attributes in terms of size (46-62 nm), polydispersity index (0.01-0.08), EE% (>95%), and sustained release profiles. Results indicated significant efficacy enhancement by reduction in worm burden, amelioration of liver pathology, and extensive damage to the fluke suckers and tegument. This was partly explained by PK data determined in rats. In addition, oral targeting of the worms was supported by the stability of PZQ-LNCs in simulated GI fluids and scanning electron microscopy (SEM) visualization of nanostructures on the tegument of worms recovered from mesenteric/hepatic veins. Cytotoxicity data indicated tolerability of PZQ-LNCs.

Conclusion: Data obtained provide evidence for the ability of oral LNCs to target distal post-absorption sites, leading to enhanced drug efficacy. From a practical standpoint, PZQ-LNCs could be suggested as a potential tolerable single lower dose oral nanomedicine for more effective PZQ mass chemotherapy.

Keywords: Schistosoma mansoni; bioavailability; lipid nanocapsules; oral targeting; pharmacokinetics; praziquantel; tegument.

Figure 1

Release of PZQ from PZQ–LNC and PZQ–OA–MFS–LNC formulations containing 5 or 25 mg/mL of PZQ in comparison to PZQ in PBS (pH 7.4) at 37°C. Note: Data represent mean ± SD (n=3). Abbreviations: LNC, lipid nanocapsules; MFS, miltefosine; OA, oleic acid; PZQ, praziquantel.

Figure 2

Histopathological study of H&E-stained liver sections of different groups of mice infected with Schistosoma mansoni. Notes: Infected untreated group showing: (A) multiple granulomas of variable sizes and shapes with preserved hepatic architecture (×100); (B) cellular granuloma composed of lymphocytes, histiocytes, epithelioid cells, and eosinophil cells, surrounding the bilharzial egg (×400); (C) Kupffer cell hyperplasia and bilharzial pigment (×400); (D) fatty changes in hepatocytes (×400); (E) hepatic sinusoids with lymphocytic infiltration (×400); and (F) infected PZQ suspension-treated mice (×100); (G) infected PZQ–LNC-25-treated mice (×100), and (H) infected PZQ–OA–MFS–LNC-25-treated mice (×100) showing small cellular granulomas with mild amelioration of liver pathology. Abbreviations: LNC, lipid nanocapsules; MFS, miltefosine; OA, oleic acid; PZQ, praziquantel.

Figure 3

SEM images of male worms recovered from the hepatic and mesenteric veins of mice of the four study groups. Notes: SEM of a male Schistosoma mansoni worm recovered from infected untreated mice (Group 1) showing (A) normal OS and VS (×1,000), (B) dorsal tegument surface with uniform size, regularly distributed T, and visible S (×5,000), and (C) apically situated S (×15,000); infected PZQ suspension-treated mice (Group 2) showing (A) distorted OS (×3,500), (B) flattening of some T with loss of S (×5,000), and (C) distorted S (×15,000); infected PZQ–LNC-25-treated mice (Group 3) showing (A) distorted OS (×3,500), (B) severe tegumental damage with erosion of the surface and appearance of subtegumental tissue (×5,000), and (C) distorted S (×15,000); and infected PZQ–OA–MFS–LNC-25-treated mice (Group 4) showing (A) distorted OS (×1,500), (B) severe tegumental damage with erosion of the surface and appearance of subtegumental tissue (×5,000), and (C) distorted S (×15,000). Abbreviations: LNC, lipid nanocapsules; MFS, miltefosine; OA, oleic acid; OS, oral sucker; PZQ, praziquantel; S, spines; SEM, scanning electron microscopy; T, tubercles; VS, ventral sucker.

Figure 4

Mean plasma levels of PZQ following oral administration of 250 mg/kg dose of PZQ as suspension and LNC formulations to rats (n=5). Note: Error bars represent standard error of the mean. Abbreviations: LNC, lipid nanocapsules; MFS, miltefosine; OA, oleic acid; PZQ, praziquantel.

Figure 5

Cytotoxic effect of PZQ-loaded LNCs in comparison to PZQ solution on PBMCs using MTT assay and expressed as IC₅₀ values after 24 h of incubation. Abbreviations: LNCs, lipid nanocapsules; MFS, miltefosine; MTT, 3-(4,5-dimethiazol-zyl)-2-5-diphenyltetrazolium bromide; OA, oleic acid; PBMCs, peripheral blood mononuclear cells; PZQ, praziquantel.

Figure 6

SEM of a male Schistosoma mansoni worm (×35,000) recovered from a mouse treated with (A) PZQ suspension, (B) PZQ–LNC-25 or (C) PZQ–OA–MFS–LNC-25 showing nanostructures of similar size to LNCs in between spines and on damaged schistosomal surface (indicated by arrows), only in worms recovered from mice treated with PZQ–LNC formulations (B and C). Abbreviations: LNCs, lipid nanocapsules; MFS, miltefosine; OA, oleic acid; PZQ, praziquantel; SEM, scanning electron microscopy.