J.M. Irache

Increased oral bioavailability of paclitaxel by its encapsulation through complex formation with cyclodextrins in poly(anhydride) nanoparticles

The aim of this work was to study the oral bioavailability in rats of paclitaxel (PTX) when encapsulated as a complex with cyclodextrins in poly(anhydride) nanoparticles (NP). For this purpose three different cyclodextrins were selected: beta-cyclodextrin (CD), 2-hydroxypropyl-beta-cyclodextrin (HPCD) and 6-monodeoxy-6-monoamino-beta-cyclodextrin (NHCD). A single dose of 10mg paclitaxel per kg body weight as PTX-cyclodextrin nanoparticles was used. Plasma curves were characterised by a plateau of paclitaxel concentration close to the C(max) from T(max) till 24h post-administration. For PTX-CD NP and PTX-HPCD NP, these sustained levels of the anticancer drug were found to be between 27 and 33-fold higher than the reported value of drug activity whereas the relative oral bioavailability of paclitaxel was calculated to be higher than 80%. These facts would be directly related with a synergistic effect obtained by the combination of the bioadhesive properties of poly(anhydride) nanoparticles and the inhibitory effect of cyclodextrins on the activity of P-glycoprotein and cythocrome P450.

Spray-drying of poly(anhydride) nanoparticles for drug/antigen delivery

Gantrez AN nanoparticles can be obtained by desolvation of the poly(anhydride) with an aqueous medium, followed by a purification step and freeze-drying. In order to simplify this method, a spray-drying procedure was evaluated here. For this purpose, suspensions of nanoparticles were mixed with carbohydrates before their drying. Lactose, in a saccharide/polymer ratio of 2, was found to be the most suitable excipient regarding the physicochemical characteristics and stability of the resulting nanoparticles. These conditions can be successfully applied to the preparation of conventional, combined cyclodextrin/polyanhydride or pegylated nanoparticles. The capabilities of the new procedure were also studied by the characterization of nanoparticles loaded with either an antigenic extract (HS from Brucella ovis) or atovaquone. In all cases, the new formulations displayed similar physico-chemical characteristics to those of nanoparticles obtained by lyophilization. In summary, the spray-drying procedure can be an adequate alternative to lyophilization in the preparative process of poly(anhydride) nanoparticles.

Micro-organism-like nanoparticles for oral antigen delivery

The aim of this work was to design and evaluate microorganism-like nanoparticles able to either mimic adhesion and colonization patterns of bacteria or to enhance and modulate the host immune response. Thus poly(anhydride) nanoparticles were either coated with adhesive factors (either with flagellin from Salmonella enteritidis or mannosamine) or loaded with lipopolysaccharide of Brucella ovis. The mucosal affinity of the nanoparticles was investigated by bioadhesion and fluorescence microscopy studies. The immunoadjuvant properties were checked by the oral route using ovalbumin as an antigen model. The results indicated that both flagellin and mannosamine nanoparticles display a stronger mucosal affinity to normal mucosa and Peyer’s patches than control ones, whereas LPS entrapped ones did not. Surprisingly, LPS formulation was unable to enhance the immune response by the oral route. However, flagellin and mannosamine nanoparticles induced stronger and more balanced serum levels of both IgG1 (Th2) and IgG2a (Th1) than control ones. In addition, oral immunization with ligand formulations induced high levels of fecal IgA.

Nanoparticules mucopénétrantes : véhicules pour l’administration orale du paclitaxel

Paclitaxel is an anticancer drug used as solution for perfusion for the treatment of certain types of cancers. In the last years, a number of strategies have been proposed for the development of an oral formulation of this drug. However, this task is quite complicated due to the poor aqueous solubility of paclitaxel as well as the fact that this compound is substrate of the intestinal P-glycoprotein and the cytochrome P450 enzymatic complex. In this work, we have developed pegylated nanoparticles with mucopenetrating properties in order to conduct paclitaxel onto the surface of the enterocyte. These nanoparticles displayed a size of about 180 nm and a drug loading close to 15% by weight. The pharmacokinetic study in mice has shown that these nanoparticles were capable to offer therapeutic plasma levels of paclitaxel up to 72 hours. In addition, the oral relative bioavailability of paclitaxel when loaded in nanoparticles pegylated with poly(ethylene glycol) 2000 (PEG) was found to be 85%. In a subcutaneous model of tumour in mice, these pegylated nanoparticles administered orally every 3 days have demonstrated a similar efficacy than Taxol® administered intravenously every day during 9 days. All of these results suggested that these pegylated nanoparticles were capable to cross the mucus layer of the gut and, then, reach the surface of the enterocytes. The PEG molecules would facilitate the adhesion of nanoparticles to this epithelial surface, minimise the pre-systemic metabolism of paclitaxel and, thus, promote its absorption.

Encapsulation of ganciclovir in albumin nanoparticles enhances the thymidine kinase suicide gene therapy

The therapeutic combination of the herpesvirus thymidine kinase (tk) and ganciclovir has shown great clinical promise as gene therapy for the treatment of hepatocarcinoma. The aim of this study was to evaluate the efficacy of the loading of ganciclovir in albumin nanoparticles to induce hepatoxicity in animals previously treated with adenoviral vectors expressing the tk gene (AdCMVtk). The use of these carriers dramatically increased the drug toxic effects, including high transaminase levels (AST and ALT levels). In addition, the histologic analysis of the liver also revealed a great cellular damage with necrotizing area and perivascular inflammatory reactions. These nanoparticulate carriers offered the additional advantage of increasing the plasmatic half-life of the drug and its tissue distribution, as it was determined by the pharmacokinetic analysis. Thereby, they constitute a very effective system for the prolonged delivery of ganciclovir in vivo, improving the disposition of ganciclovir in the liver.

Radiomarcaje y estudios de biodistribución de nanopartículas poliméricas como adyuvantes para la vacunación oftálmica frente a la brucelosis

PURPOSE To optimize radiolabeling with (99m)Tc of mannosylated Gantrez(®) nanoparticles loaded with the Brucella Ovis antigen (Man-NP-HS) and to carry out biodistribution studies in mice after ocular administration of the nanoparticles. MATERIAL AND METHODS Man-NP-HS nanoparticles were prepared by the solvent displacement method. They were purified, lyophilized and characterized. Following this, they were radiolabeled with 74 MBq of (99m)TcO4(-) previously reduced with an acidic stannous chloride solution, working in absence of oxygen and at a final pH of 4. Radiolabeling yield was evaluated by TLC. Biodistribution studies were carried out in mice after ocular administration of the formulation and control of free (99m)TcO4(-). To do so, the animals were humanely killed at 2 and 24hours after the ocular administration and activity in organs was measured in a Gamma counter. RESULTS Radiolabeling yield obtained was greater than 90%. Biodistribution studies of (99m)Tc-Man-NP-HS showed radioactivity accumulated at 2 and 24hours in nasal and ocular mucosa and gastrointestinal tract, in contrast to biodistribution of free (99m)TcO4(-) that remained concentrated in the skin around the eye and gastrointestinal tract. CONCLUSION Biodistribution studies of (99m)Tc-Man-NP-HS after ocular instillation have made it possible to demonstrate its biodistribution in nasal mucosa and gastrointestinal tract. This characteristic is essential as an antigenic delivery system throughout the ocular mucosa. This, together with its elevated immune response, effective protection and intrinsic avirulence make them a suitable anti-Brucella vaccine candidate.