IDO is an enzyme that tumors use to create a state of immunosupression. 1-d-methyltryptophan (1-MT) is an IDO pathway inhibitor. After being successfully evaluated in preclinical studies, current clinical trials are actually analyzing its efficacy as monotherapy or in combination with multiple chemotherapeutic agents such as paclitaxel. 1-MT very poor solubility in water and many other solvents precludes its ease parenteral administration. It is currently administered by oral route because high daily doses were well-tolerated and effectively inhibited the IDO activity although only 25% of dose was recovered in plasma. The present work describes the preparation and characterization of 1-MT nanocrystals in order to enhance its solubility, dissolution rate, biodisponibility as well as facilitate its administration by parenteral route. A bottom-down approach of nanoprecipitation with an antisolvent was used for the fabrication of the nanocrystals and the choice of stabilizers was critical for reducing the size. Thermal analysis and x-ray diffraction indicated modifications in the drug crystalline state by the process. Through the reduction size and crystalline state modifications the dissolution characteristics of raw material were significantly increased. In a Lewis Lung cancer mice model, the nanocrystals strategy facilitated the sc administration and its antitumoral activity was similar to that of i.v. paclitaxel. The best efficacy was achieved when sc 1-MT nanocrystals were administered in combination with oral paclitaxel loaded in poly(anhydride) nanoparticles. Take together, 1-MT nanocrystals delivery performs a nanotechnological strategy suitable to modify the current route and schedule for its administration.

Glibenclamide is a sulfonylurea used for the oral treatment of type II diabetes mellitus. This drug shows low bioavailability as consequence of its low solubility. In order to solve this problem, the interaction with cyclodextrin has been proposed. This study tries to provide an explanation about the processes involved in the formation of GB-beta CDs complexes, which have been interpreted in different ways by several authors. Among native cyclodextrins, beta CD presents the most appropriate cavity to host glibenclamide molecules showing A(L) solubility diagrams (K-1:1 approximate to 1700 M-1). However, A(L)- solubility profiles were found for pa) derivatives, highlighting the coexistence of several phenomena involved in the drug solubility enhancement. At low CD concentration, the formation of inclusion complexes can be studied and the stability constants can be calculated (K-1:1 approximate to 1700 M-1) Whereas at high CD concentration, the enhancement of GB solubility would be mainly attributed to the formation of nanoaggregates of CD and GB-CD complexes (sizes between 100 and 300 nm). The inclusion mode into beta CD occurs through the cyclohexyl ring of GB, adopting a semi-folded conformation which maximizes the hydrogen bond network. As consequence of all these phenomena, a 150-fold enhancement of drug solubility has been achieved using beta-cyclodextrin derivatives. Thus, its use has proven to be an interesting tool to improve the oral administration of glibenclamide in accordance with dosage bulk and dose/solubility ratio requirements. (C) 2017 Elsevier B.V. All rights reserved.

The aim of this work was to evaluate the capability of zein nanoparticles as oral carriers for glibenclamide (GB). Nanoparticles were prepared by a desolvation procedure in the presence of lysine as stabilizer. A central composite design was used to optimize this preparative process. Under the selected conditions, nanoparticles displayed a size of about 190 nm, a surface charge of -37 mV and a payload of 45 mu g GB/mg. Small-angle neutron scattering and X-ray diffraction techniques suggested an internal fractal-like structure, based on the repetition of spherical blocks of zein units (about 20 nm) grouped to form the nanoparticles. This structure, stabilized by lysine molecules located at the surface, would determine the release of GB (molecularly trapped into the nanoparticles) by a pure diffusion mechanism. Moreover, GB-loaded nanoparticles induced a significant hypolipidemic effect with a reduction of about 15% in the fat content of C. elegans worms. In addition, did not induce any significant modification in the lifespan of worms. In summary, the employment of zein nanoparticles as delivery systems of glibenclamide may be an interesting approach to develop new oral formulations of this antidiabetic drug.

The sorption and release of tyrosol and caffeic acid, two biophenolic antioxidants with known health benefits, in different insoluble cyclodextrin polymers have been studied. Cyclodextrin polymers were synthesized by cross-linking, beta-cyclodextrin or 50:50 w/w nominal mixtures of alpha- and beta-cyclodextrins using either epichlorohydrin (EP) or toluene-2,4-diisocyanate (TDI) as cross-linking agents. An analogous sucrose polymer was prepared using EP as cross-linking reagent. Freundlich isotherms and isosteric heats of sorption for tyrosol and caffeic acid in the insoluble beta-cyclodextrin polymer cross-linked with epichlorohydrin at 50 degrees C were obtained and discussed. Finally, the release of tyrosol and caffeic acid has been studied from loaded polymer disks, the microstructures of which were characterized by mercury intrusion porosimetry. Caffeic acid shows greater affinity than tyrosol for the polymeric matrices as it presents a higher sorption and a lower and slower release. However, tyrosol has a higher isosteric heat of sorption for low coverages.

Glibenclamide is an antidiabetic drug showing low bioavailability as consequence of its low solubility. To solve this drawback, the interaction with cyclodextrins has been proposed. The formation of GB-beta CDs inclusion complexes was carried out using different methods, beta CD derivatives and drug-to-cyclodextrin ratios. The structures of the corresponding complexes have been studied by molecular modelling, X-ray diffraction and differential thermal analysis. The dissolution behavior of inclusion complexes has been compared to that of pure GB. Dimeric inclusion complexes were obtained with different CD disposals, head-to-head for beta CD and head-to-tail for HP beta CD and RM beta CD. Amorphous inclusion complexes were obtained by employing methods of freeze-drying or coevaporation in ammonia-water. However, crystalline structures were formed by kneading and coevaporation in ethanol/water in the case of GB-beta CD complexes. The arrangement of these structures depended on the GB:beta CD ratio, yielding cage type structures for 1:3 and 1:5 ratios and channel-type structures for higher GB contents. The amount of GB released and its dissolution rate was considerably increased by the use of amorphous inclusion complexes; whereas, slower GB release rates were found from crystalline inclusion complexes formed by kneading or coevaporation in ethanol/water. In addition, it was found that the porous structure strongly conditioned the GB dissolution rate from crystalline products.

Gels obtained by complexation of octablock star polyethylene oxide/polypropylene oxide copolymers ( Tetronic 90 R4) with alpha-cyclodextrin (alpha- CD) were evaluated as matrices for drug release. Both molecules are biocompatible so they can be potentially applied to drug delivery systems. Two different types of matrices of Tetronic 90 R4 and alpha-CD were evaluated: gels and tablets. These gels are capable to gelifying in situ and show sustained erosion kinetics in aqueous media. Tablets were prepared by freeze-drying and comprising the gels. Using these two different matrices, the release of two model molecules, L-tryptophan ( Trp), and a protein, bovine serum albumin ( BSA), was evaluated. The release profiles of these molecules from gels and tablets prove that they are suitable for sustained delivery. Mathematical models were applied to the release curves from tablets to elucidate the drug delivery mechanism. Good correlations were found for the fittings of the release curves to different equations. The results point that the release of Trp from different tablets is always governed by Fickian diffusion, whereas the release of BSA is governed by a combination of diffusion and tablet erosion.

The interactions of diflunisal (DF) with chitosans (CS) of different molecular weights and carboxymethylchitosan (CMCS), a water-soluble derivative, have been investigated. The interactions in solution have been studied by solubility assays in which the highest solubilisation (13-fold) was obtained with CMCS. Solid dispersions were prepared by coevaporation and kneading methods. Solid state characterisation was performed by X-ray diffraction analysis, scanning electron microscopy, thermomicroscopy, differential thermal analysis and infrared spectroscopy. Drug-polymer electrostatic interactions and hydrogen bonds are the main binding forces in these systems. The kneading method gave rise to amorphous systems regardless of the polymer employed. However, coevaporation resulted in the formation of different polymorphs of diflunisal (form II or III) depending on the type of polymer used. Therefore, it seems that drug-polymer interactions determine the crystallization pattern of the drug. Finally, diflunisal release from these systems improved markedly with CMCS and significantly in the presence of low molecular weight CS.

Tyrosol (TY), 4-(2-hydroxyethyl)phenol, is an olive oil biophenol with antioxidant activity and positive effects on human health. This study has investigated the interactions of TY with cyclodextrins (CD) and a CD polymer. Complexation of TY with beta-CD, hydroxypropyl-beta-CD (HP-beta-CD), and methyl-beta-CD (Me-beta-CD) has been evaluated both in aqueous solution and in the solid state. The techniques employed in solution to determine the apparent stability constants of the respective complexes were fluorescence and UV-visible spectroscopies. Complexation with beta-CD and its derivatives involved an increase of both the UV absorbance and the intrinsic fluorescence of TY; a bathochromic shift of the UV spectrum was detected as well. The apparent stability constants obtained with native beta-CD, Me-beta-CD and HP-beta-CD presented similar values. Complexes in the solid state were obtained by coevaporation and kneading. They were characterised by X-ray diffraction analysis and differential thermal analysis. The interaction of TY with beta-CD led to a crystalline complex; the same diffraction pattern was obtained by coevaporation and kneading. The complexes obtained with methyl- and HP-beta-CD were amorphous irrespective of the preparation method. In addition, the retention of TY in an insoluble polymer of CD crosslinked with epichlorohydrin has been quantified. In approximately 20 min, 1 mg of TY per gram of polymer was retained.

Tyrosol and caffeic acid are biophenols that contribute to the beneficial properties of virgin olive oil. The influence of hydroxypropyl-beta-cyclodextrin (HP beta-CD) on their respective antioxidant capacities was analyzed. The ORAC antioxidant activity of tyrosol (expressed as mu M Trolox equivalents/mu M Tyrosol) was 0.83 +/- 0.03 and it increased up to 1.20 +/- 0.11 in the presence of 0.8 mM HP beta-CD. However, the ORAC antioxidant activity of caffeic acid experienced no change. The different effect of HP beta-CD on each compound was discussed. In addition, the effect of increasing concentrations of different cyclodextrins in the development of ORAC-fluorescence (ORAC-FL) assays was studied. The ORAC signal was higher for HP beta-CD, followed by M beta-CD, beta-CD, gamma-CD and finally alpha-CD. These results could be explained by the formation of inclusion complexes with fluorescein.

Complexation of ebastine (EB) with hydroxypropyl and methyl-beta-cyclodextrin (HP-beta-CD and Me-beta-CD) was studied in aqueous solutions and in the solid state. The formation of inclusion complexes in aqueous solutions was analysed by the solubility method. The assays were designed using low CD concentrations compared with the solubility of these derivatives in order to avoid non-inclusion phenomena and to obtain a linear increase in EB solubility as a function of CD concentration. The values of complexation efficiency for HP-beta-CD and Me-beta-CD were 1.9 x 10(-2) and 2.1 x 10(-2), respectively. It seems that the non polar character of the methyl moiety slightly favoured complexation. In relation to solid state complexation, 1: 1 EB: CD systems were prepared by kneading, and by heating a drug-CD mixture at 90 degrees C. They were analysed using X ray diffraction analysis by comparison with their respective physical mixtures. A complex with a characteristic diffraction pattern similar to that of the channel structure of beta-CD was formed with Me-beta-CD in 1: 1 melted and 1: 2 EB: CD kneaded systems. Complexation with HP-beta-CD was not clearly evidenced because only a slight reduction of drug crystallinity was detected. Finally, the loading of EB in two beta-CD polymers cross-linked with epichlorohydrin yielded 7.3 and 7.7 mg of EB/g polymer respectively.

The mechanisms of sorption and release of solutes from polymeric materials synthesised by cross-linking ß-cyclodextrin (ß-CD) with epichlorohydrin have been investigated. Gemfibrozil (pKa 4.7) was chosen as model solute. The polymers were obtained by suspension (P1) and block polymerisation (P2). Both P1 and P2 had similar ß-CD contents (65 and 64%) and their swelling capacities were 5.0 and 5.8 cm3/g, respectively. The sorption of gemfibrozil kinetic data in water and in aqueous solutions at pH 2.8 and 7.0 were fitted to a hyperbolic equation and they were studied by applying the Weber and Morris and the Elovich equations. P2 presented faster rates and higher sorption capacities in water and at pH 2.8. The mechanisms of sorption were pH-dependent. In water, the sorption rate was determined by the diffusion of gemfibrozil in the polymer network and fitted the Weber and Morris equation. At pH 2.8 a better adjustment to the Elovich equation suggested a significant influence of the inclusion in the ß-CD cavities. The release kinetics at pH 7.0 was controlled by drug solubilisation and presented maximum release values of 90 (P1) and 95% (P2), with a suitable regeneration of the loaded polymer. In water, the release was slower, fitted a hyperbole and the mechanism was controlled by drug solubility and also by the polymeric geometry. Finally, release assays were carried out from discs of loaded polymer in a medium that simulated the gastrointestinal tract.