Release characteristics of endogenous constituents by exposure of small intestine to modified beta-cyclodextrins

Development of rectal delivered thermo-reversible gelling film encapsulating a 5-fluorouracil hydroxypropyl-β-cyclodextrin complex

We have developed a novel 5-Fluorouracil (5FU) formulation for rectal application to improve its therapeutic efficiency in colorectal cancer. The results indicated that 5FU formed an inclusion complex with Hydroxypropyl-β-Cyclodextrin (HP-β-CD). The stoichiometry of the complex was 1:1, with apparent stability constant of 100.4M(-1). After investigating physicochemical properties of the 5FU-HP-β-CD complex encapsulated with thermo-reversible gelling film, the optimized formulation P407/P188/HPMC/5FU-HP-β-CD (18.5/2.5/0.2/15%) was selected and evaluated. The result showed that the 5FU-HP-β-CD complex increased the solubility of 5FU, prolonged and enhanced its releasing. As compared to the raw drug, the transport efficiency of the 5FU-HP-β-CD complex itself or entrapped in thermo-reversible gelling film were respectively 7.3- and 6.8-fold increased, and the cellular uptake of 5-FU 4.9- and 5.4-fold elevated. There was no irritation or damage to rectal sites in the 10h treatment period. Therefore, this HP-β-CD based formulation might improve the therapeutic effect of 5FU on colon-rectal cancer.

Strategies for the design of orally bioavailable antileishmanial treatments

Leishmaniasis is one of the six major tropical diseases targeted by the World Health Organization. The most serious, life-threatening form is visceral leishmaniasis (VL). No vaccine is yet available for human use and chemotherapy is the main mean of dealing with this disease. This review focuses on the development of drug delivery systems (DDS) for treatment of leishmaniasis. After an overview of the significance of leishmaniasis in 2013, current chemotherapy and its limitations are considered, leading to possible strategies to improve the treatment of VL: new drugs, combinations of existing drugs and DDS, particularly for oral administration. Nanostructured biomaterials such as lipid-based or polymeric nanoparticles have unique physicochemical properties, ultra-small and controllable size, large surface area to mass ratio and the possibility of surface modification which can be used to advantage for the oral administration of antileishmanial drugs. They can improve the rate of dissolution of poorly water-soluble drugs, increase intestinal residence time by bioadhesion and, especially when lipid additives are used, influence the route and efficiency of absorption. These recent advances in this very active field should lead to better management of this serious disease.

β-Cyclodextrin as a suitable solubilizing agent for in situ absorption study of poorly water-soluble drugs

To evaluate the intestinal permeability of poorly water-soluble compounds, it is of importance to completely dissolve them in a medium and to avoid precipitation during experiments. This study was undertaken to find an agent possessing a high-solubilizing capacity and exhibiting minimal modulating impact on membrane integrity and absorption systems such as passive diffusion and carrier-mediated permeation. Phenytoin dissolution was compared in the presence of seven solubilizing agents at concentrations of 1, 2, or 5% using a centrifugation method. The capacity to dissolve phenytoin was great in beta-cyclodextrin (beta-CD) and hydroxypropyl beta-cyclodextrin, followed by Tween 80. Those of methanol, dimethyl sulfoxide, dimethyl acetoamide, and polyethylene glycol 400 were much lower than expected. One percent beta-CD did not alter the absorption of fluorescein isothiocyanate-dextran 4,000 or the release of protein and lactate dehydrogenase into in situ loop contents, suggesting that 1% beta-CD had no significant impact on the integrity of the intestinal membrane. One percent beta-CD also did not alter the absorption of caffeine, ceftibuten, or rhodamine 123 from in situ jejunal loops, indicating no interference with passive diffusion and active transports mediated by a peptide transporter and P-glycoprotein. In conclusion, 1% beta-CD is a suitable solubilizing agent for evaluating in situ intestinal absorption of poorly water-soluble compounds.

A moderate interaction of maltosyl-alpha-cyclodextrin with Caco-2 cells in comparison with the parent cyclodextrin

The cytotoxicity of maltosyl-alpha-cyclodextrin (G2-alpha-CyD) and maltosyl-beta-cyclodextrin (G2-beta-CyD) toward Caco-2 cells was compared with that of natural alpha-cyclodextrin (alpha-CyD), beta-cyclodextrin (beta-CyD) and gamma-cyclodextrin (gamma-CyD). The degree of increase in cytotoxicity was dependent on the CyD's type and the concentration: the cytotoxicity of CyDs at the same concentration increased in the order of gamma-CyD<G2-beta-CyD<G2-alpha-CyD<<alpha-CyD, although beta-CyD could not be compared to other CyDs because of low solubility in water. Alpha-CyD decreased transepithelial electrical resistance (TEER) and increased the apical-to-basolateral (AP-to-BL) transport of [3H]mannitol, a paracellular transport marker, in a concentration-dependent manner, suggesting that alpha-CyD decreased the integrity of Caco-2 cell monolayers. In addition, alpha-CyD increased the AP-to-BL transport of rhodamine 123, a transcellular transport marker, under the experimental conditions being independent of P-glycoprotein. In contrast, G2-alpha-CyD, G2-betaCyD and gamma-CyD had slight effect on both TEER and the transport of mannitol and rhodamine 123 even at relatively high concentrations up to 150 mM. The inability of G2-alpha-CyD and G2-beta-CyD to effect TEER and the transport of mannitol and rhodamine 123 could be explained by the findings that these maltosylated CyDs released only a small amount of membrane constituents from Caco-2 cell monolayers and interacted only weakly with monolayers composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC) formed on water. These results indicate that G2-alpha-CyD has less cytotoxicity and less disturbing ability toward Caco-2 cell monolayers than alpha-CyD, and G2-beta-CyD has, at least, comparable cytotoxicity to beta-CyD toward them. Thus, from the safety point of view, highly water-soluble G2-alpha-CyD and G2-beta-CyD may be particularly useful in various pharmaceutical formulations.