In situ microemulsion-gel obtained from bioadhesive hydroxypropyl methylcellulose films for transdermal administration of zidovudine.

This study aims to develop in situ microemulsion-gel (ME-Gel) obtained from hydroxypropyl methylcellulose (HPMC) films for transdermal administration of Zidovudine (AZT). Firstly, HPMC films containing propylene glycol (PG) and eucalyptus oil (EO) were obtained and characterized. Later, a pseudo-ternary phase diagram composed of water, EO, tween 80 and PG was obtained and one microemulsion (ME) with a similar proportion of the film components was obtained. ME was transformed in ME-Gel by the incorporation of HPMC. Finally, HPMC films were hydrated with Tween 80 solution to yield in situ ME-Gel and its effect on AZT skin permeation was compared with HPMC film hydrated with water (F5hyd). The results showed that the ME and ME-Gel presented a droplet size of 16.79 and 122.13 µm, respectively, polydispersity index (PDI) < 0.39 and pH between 5.10 and 5.40. The incorporation of HPMC resulted in viscosity about 2 times higher than the use of ME. The presence of AZT did not alter the formulation properties. The in situ ME-Gel promoted a two-fold increase in the permeated amount of AZT compared to F5hyd. The results suggest that it was possible to obtain an ME-Gel in situ from HPMC films and that its effect on transdermal permeation of AZT was significant.

In vitro digestibility of gellan gels loaded with jabuticaba extract: Effect of matrix-bioactive interaction.

Jabuticaba is a native Brazilian fruit rich in phenolic compounds as anthocyanins, showing several benefits for human health but a high sensibility to physicochemical digestion conditions. Gellan is a biopolymer that could be used as a material to protect and carry bioactive compounds, since this polysaccharide is resistant to gastric pH conditions. In this context, gellan gels containing jabuticaba extract were produced using two different ionic strength values (adding calcium ions), which resulted in varied structures. These gels were subjected to two different in vitro digestion processes, modifying the type of mechanical forces applied to simulate stomach and intestine movement conditions. Anthocyanins release (by pH differential method), mechanical properties, confocal and light microscopy of gels were evaluated during in vitro digestibility. Results showed that jabuticaba extract exerted effect on gels mechanical-structural properties, since an increase of stress at rupture (hardness) and a decrease of strain at rupture (deformability) were observed only in gels without calcium addition. Although all gellan gels have improved anthocyanins retention during simulated gastrointestinal digestion process, gels without calcium were more efficient. Our results demonstrated that gellan gels could act as good carriers for anthocyanins, but their efficiency is dependent on the matrix composition, demonstrating that specific studies should be accomplished to determine which changes may occur in the matrix after bioactive addition. Furthermore, our results showed that the type of mechanical forces applied during in vitro digestion is an important variable, since the use of compression (a more similar-to-in vivo system) rather than shear forces increased the release of anthocyanins.

Arabinoxylan-Based Particles: In Vitro Antioxidant Capacity and Cytotoxicity on a Human Colon Cell Line.

Background and objectives: Arabinoxylans (AX) can gel and exhibit antioxidant capacity. Previous studies have demonstrated the potential application of AX microspheres as colon-targeted drug carriers. However, the cytotoxicity of AX gels has not been investigated so far. Therefore, the aim of the present study was to prepare AX-based particles (AXM) by coaxial electrospraying method and to investigate their antioxidant potential and cytotoxicity on human colon cells. Materials and Methods: The gelation of AX was studied by monitoring the storage (G') and loss (G'') moduli. The morphology of AXM was evaluated using optical and scanning electron microscopy (SEM). The in vitro antioxidant activity of AX before and after gelation was measured using the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. In addition, the effect of AX and AXM on the proliferation of human colon cells (CCD 841 CoN) was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results: The final G' and G'' values for AX gels were 293 and 0.31 Pa, respectively. AXM presented spherical shape and rough surface with a three-dimensional and porous network. The swelling ratio and mesh size of AXM were 35 g water/g AX and 27 nm, respectively. Gelation decreased the antioxidant activity of AX by 61-64 %. AX and AXM did not affect proliferation or show any toxic effect on the normal human colon cell line CCD 841 CoN. Conclusion: The results indicate that AXM could be promising biocompatible materials with antioxidant activity.

Mucoadhesive In Situ Gelling Liquid Crystalline Precursor System to Improve the Vaginal Administration of Drugs.

The vaginal mucosa is a very promising route for drug administration due to its high permeability and the possibility to bypass first pass metabolism; however, current vaginal dosage forms present low retention times due to their dilution in vaginal fluids, which hampers the efficacy of many pharmacological treatments. In order to overcome these problems, this study proposes to develop a mucoadhesive in situ gelling liquid crystalline precursor system composed of 30% of oleic acid and cholesterol (7:1), 40% of ethoxylated and propoxylated cetyl alcohol, and 30% of a dispersion of 16% Poloxamer 407. The effect of the dilution with simulated vaginal fluid (SVF) on this system was evaluated by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS), rheological studies, texture profile analysis (TPA), mucoadhesion study, in vitro drug release test using hypericin (HYP) as drug model, and cytotoxicity assay. PLM and SAXS confirmed the formation of an isotropic system. After the addition of three different concentrations of SVF (30, 50, and 100%), the resultant formulations presented anisotropy and characteristics of viscous lamellar phases. Rheology shows that formulations with SVF behaved as a non-Newtonian fluid with suitable shear thinning for vaginal application. TPA and mucoadhesion assays indicated the formation of long-range ordered systems as the amount of SVF increases which may assist in the fixation of the formulation on the vaginal mucosa. The formulations were able to control about 75% of the released HYP demonstrating a sustained release profile. Finally, all formulations acted as safe vaginal drug delivery systems.

Environmental Topology and Water Availability Modulates the Catalytic Activity of ß-Galactosidase Entrapped in a Nanosporous Silicate Matrix.

In the present work we studied the catalytic activity of E. coli ß-Gal confined in a nanoporous silicate matrix (Eß-Gal) at different times after the beginning of the sol-gel polymerization process. Enzyme kinetic experiments with two substrates (ONPG and PNPG) that differed in the rate-limiting steps of the reaction mechanism for their ß-Gal-catalyzed hydrolysis, measurements of transverse relaxation times (T2) of water protons through 1H-NMR, and scanning electron microscopy analysis of the gel nanostructure, were performed. In conjunction, results provided evidence that water availability is crucial for the modulation observed in the catalytic activity of ß-Gal as long as water participate in the rate limiting step of the reaction (only with ONPG). In this case, a biphasic rate vs. substrate concentration was obtained exhibiting one phase with catalytic rate constant (kcA), similar to that observed in solution, and another phase with a higher and aging-dependent catalytic rate constant (kcB). More structured water populations (lower T2) correlates with higher catalytic rate constants (kcB). The T2-kcB negative correlation observed along the aging of gels within the 15-days period assayed reinforces the coupling between water structure and the hydrolysis catalysis inside gels.

Protein/arabinoxylans gels: effect of mass ratio on the rheological, microstructural and diffusional characteristics.

Wheat bran arabinoxylan (WBAX) gels entrapping standard model proteins at different mass ratios were formed. The entrapment of protein affected the gel elasticity and viscosity values, which decreased from 177 to 138 Pa. The presence of protein did not modify the covalent cross-links content of the gel. The distribution of protein through the network was investigated by confocal laser scanning microscopy. In mixed gels, protein aggregates forming clusters were detected at protein/polysaccharide ratios higher than 0.25. These clusters were not homogeneously distributed, suggesting that WBAX and protein are located in two different phases. The apparent diffusion coefficient (Dm) of proteins during release from mixed gels was investigated for mass ratios of 0.06 and 0.12. For insulin, Dm increased significantly from 2.64 × 10-7 to 3.20 × 10-7 cm2/s as the mass ratio augmented from 0.06 to 0.12. No significant difference was found for Dm values of ovalbumin and bovine serum albumin released from the mixed gels. The results indicate that homogeneous protein/WBAX gels can be formed at low mass ratios, allowing the estimation of Dm by using an analytical solution of the second Fick's law.

Transdermal delivery of butamben using elastic and conventional liposomes.

Gel formulations containing the local anesthetic butamben (BTB) encapsulated in either conventional (BTBLUV) or elastic (BTBLUV-EL) liposomes were prepared and characterized, and then evaluated in terms of their skin permeability. Parameters measured included vesicle size and surface charge, BTB fluorescence anisotropy, encapsulation efficiency, partition coefficient and liposomal membrane organization. Encapsulation efficiencies and membrane/water partition coefficients were determined using a phase separation. The partition coefficients of the elastic and conventional formulations were 2025 ± 234 and 1136 ± 241, respectively. The sizes of the elastic and conventional liposomes did not change significantly (p > 0.05) following incorporation of the anesthetic. As expected, the elastic liposomes presented order parameters that were lower than those of the conventional liposomes, as determined by electron paramagnetic resonance with a 5-stearic acid nitroxide probe incorporated into the bilayer. After 8 h, the fluxes into the receiving solution (µg/cm(2)/h) were 6.95 ± 1.60 (10% BTB), 23.17 ± 6.09 (10% BTBLUV) and 29.93 ± 6.54 (10% BTBLUV-EL). The corresponding time lags (h) were 1.90 ± 0.48, 1.23 ± 0.28 and 1.57 ± 0.38, respectively. The permeability coefficients (10(-3 )cm/h) were 1.02 ± 0.23, 2.96 ± 0.77 and 4.14 ± 0.9, for 10% BTB, 10% BTBLUV and 10% BTBLUV-EL, respectively. The results demonstrate that anesthetic access through the skin can be considerably enhanced using liposomal gel formulations, compared to plain gel formulations.

Accelerated identification of proteins by mass spectrometry by employing covalent pre-gel staining with Uniblue A.

BACKGROUND: The identification of proteins by mass spectrometry is a standard method in biopharmaceutical quality control and biochemical research. Prior to identification by mass spectrometry, proteins are usually pre-separated by electrophoresis. However, current protein staining and de-staining protocols are tedious and time consuming, and therefore prolong the sample preparation time for mass spectrometry. METHODOLOGY AND PRINCIPAL FINDINGS: We developed a 1-minute covalent pre-gel staining protocol for proteins, which does not require de-staining before the mass spectrometry analysis. We investigated the electrophoretic properties of derivatized proteins and peptides and studied their behavior in mass spectrometry. Further, we elucidated the preferred reaction of proteins with Uniblue A and demonstrate the integration of the peptide derivatization into typical informatics tools. CONCLUSIONS AND SIGNIFICANCE: The Uniblue A staining method drastically speeds up the sample preparation for the mass spectrometry based identification of proteins. The application of this chemo-proteomic strategy will be advantageous for routine quality control of proteins and for time-critical tasks in protein analysis.

Surface changes induced by osmotic shrinkage on large unilamellar vesicles.

Osmotic shrinkage changes the surface properties of dipalmitoylphosphatidylcholine large unilamellar vesicles depending on the phase state of the bilayer. In the gel state, shrinkage produces an increase in the adsorption of hydrophobic dyes, such as Merocyanine 540 (MC540) monomers, toluidine and anilinonaphthalene sulfonic acid (TNS, ANS). In the fluid state, shrinkage does not affect the bilayer surface when gradients between the inner and the outer compartments below 0.2-0.25 M NaCl (higher concentration outside) are applied. Larger differences in concentrations produce an increase in packing as inferred from the desorption of the MC monomers. Kinetic experiments show that the surface changes correlate with the volume decrease produced by the water extrusion from the vesicle interior. It is interpreted that the decrease of water content compels the vesicles to a state in which defects at the membrane surface are likely to occur when the bilayer is in the gel state.