José Manuel Cornejo-Bravo

Effects of sucrose oleate and sucrose laureate on in vivo human stratum corneum permeability

AbstractPurpose. The purpose of this work was to 1) investigate the effect of sucrose esters (sucrose oleate and sucrose laureate in water or in Transcutol®, TC) on the stratum corneum (SC) barrier properties in vivo and 2) examine the impact of these surfactant-like molecules on the in vivo percutaneous penetration of a model penetrant 4-hydroxybenzonitrile (4-HB). Methods. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and transepidermal water loss measurements were used to evaluate the sucrose oleate- and sucrose laureate-induced biophysical changes in SC barrier function in vivo. In addition, the effect of the enhancers on 4-HB penetration was monitored in vivo using ATR-FTIR spectroscopy in conjunction with tape-stripping of the treated site. Results. Treatment of the skin with 2% sucrose laureate or sucrose oleate in TC significantly increased the extent of 4-HB penetration relative to the control. Furthermore, when skin treated with these formulations was examined spectroscopically, the C-H asymmetric and symmetric stretching bands of the lipid methylene groups were characterized by 1) decreased absorbances and 2) frequency shifts to higher wavenumbers. These effects on the SC lipids and 4-HB penetration were more pronounced for sucrose laureate when combined with TC. Conclusions. A combination of sucrose esters (oleate or laureate) and TC is able to temporally alter the stratum corneum barrier properties, thereby promoting 4-HB penetration. These molecules are worthy of further investigation as potential candidates for inclusion in transdermal formulations as penetration enhancers.

In vitro evaluation of the bioadhesive properties of hydrophobic polybasic gels containing N,N-dimethylaminoethyl methacrylate-co-methyl methacrylate.

The bioadhesive properties of the hydrophobic, basic polyelectrolyte hydrogel disks containing crosslinked N,N-dimethylaminoethyl methacrylate-co-methyl methacrylate 30/70mol% were evaluated in vitro using gastric (pH 1.2), sublingual (pH 6.5), vaginal (pH 4.0) and intestinal (pH 7.5) pigs mucosas. Adhesive strength was measured using a modified Du Noüy tensiometer by measuring the force of detachment between a gel disk and the respective mucosa. The effect of crosslinker content in the gel was evaluated. It was found an increase in the adhesive strength with the increase of crosslinker content in the pH range of 4.0-7.5. For the evaluation at pH 1.2 (gastric mucosa) the opposite behavior was observed. The results indicate that initial bioadhesive contact may be the result of surface energy effects and/or electrostatic interactions of oppositely charged groups between mucin and the gel. In some cases, mucus dehydration may also be involved. When the gel is swollen, chain interpenetration also plays a roll in the bioadhesive interaction. The gels presented bioadhesive forces in gastric and vaginal mucosas (acidic medium), similar to the adhesive forces of well-known bioadhesives such as hydroxymethylcellulose and sodium alginate to the intestinal mucosa. The results indicate that hydrophobic polybasic gels present bioadhesive properties that make them suitable for site specific, pH controlled drug delivery.

Water vapour sorption behaviour of copolymers of N,N-diethylaminoethyl methacrylate and methyl methacrylate

Copolymers of N, N-diethylaminoethyl methacrylate (DEA) and methyl methacrylate (MMA) were synthesized in ethanolic solution and characterized in terms of reactivity ratios, densities and water vapour sorption. For the reaction conditions studied the copolymerization is essentially random. Polymer densities, determined by centrifugation in a density gradient, range from 1.10 for pDEA to 1.13 for p(DEA/MMA) 52/48 mol%. Flory-Huggins chi parameters were determined by isopiestic water vapour sorption, and were found to depend on both the comonomer ratio and the water content. An exceptionally strong dependence of chi on water content (or equivalently, polymer volume fraction) suggests that Flory-Huggins theory is not the proper theory to apply, especially for the polymers with the highest MMA content. Analysis of the data in terms of the Zimm-Lundberg cluster theory reveals that as the polymer becomes more hydrophobic and glassy with increased MMA, the sorption becomes more nonuniform in the polymer.

Electrospinning as a powerful technique for biomedical applications: a critically selected survey

Abstract Nowadays, electrospinning has become one of the most versatile, easy, and cost-effective techniques to engineer advanced materials used for many applications, especially in the biomedical and environmental areas. Like the numerous patents around the world, the increasing number of papers witnesses the huge potential of this simple process, and many companies have been emerged during the last years to exploit its innumerable applications. This article presents a critically selected overview of polymers that can be used to produce nanofibers, along with the biomedical applications of the resulting electrospun scaffolds. We have focused on about seven natural and synthetic polymers, but many more can be found in the literature, either as their pristine state or as composites with ceramics, metals, and other polymers. The description of some strategies for nanofiber production, and the characterization used to evaluate their optimization, has been discussed. Finally, several polymers have been recognized as highlights for future work.

A facile synthesis route for carboxyaryl-methacrylates: a way to obtain aromatic polyelectrolytes

This paper describes a flexible synthetic route for the preparation of the following methacrylic acid derivative monomers with aromatic spacers, including salicylic acid derivatives, in high yields: 2-methacryloyloxybenzoic acid (2-MBA), methyl-2-methacryloyloxybenzoate (M2-MB), 3-methacryloyloxybenzoic acid (3-MBA), methyl-3-methacryloyloxybenzoate (M3-MB), 4-methacryloyloxybenzoic acid (4-MBA), methyl-4-methacryloyloxybenzoate (M4-MB), 4-methacryloyloxy phenyl acetic acid (4-MPAA), methyl-4-methacryloyloxyphenylacetate (M4-MPA) and methyl-4-methacryloyloxyphenylpropionate (M4-MPP). The preparation of the respective aromatic polymers from these monomers by solution free-radical polymerization and their characterization are also described. The position of the substituent in the aromatic spacer ring plays a very important role in the properties of the polymers prepared. While for methyl-ester substitution the glass transition temperature increases from ortho to para isomers, in the case of carboxylic acid substitution this value decreases from ortho to para isomers. The four polymers prepared with free acid groups are hydrophobic polyelectrolytes, as shown by their behavior in aqueous NaCl solutions at different pH values, making them potential candidates for new pH sensitive materials.

Kinetics of drug release from hydrophobic polybasic gels : effect of buffer acidity

Abstract The present work studies the variability of drug release rates from hydrophobic polybasic gels, due to the presence of acidic buffer species. Release kinetics of the model drug caffeine from crosslinked poly(methyl methacrylate-co-N,N-dimethylaminoethyl methacrylate) hydrogels were measured as a function of buffer concentration, buffer acidity (pK), and solution pH, with total ionic strength held constant. Results show that the release rate of caffeine is determined by the concentration of buffering species in the nonionized, conjugate acid form, and not by the pH itself. These results correlate well with the buffer effects on swelling rate that have been demonstrated elsewhere [8]. Since it is difficult to control the concentration and composition of weak acids in the stomach fluid, precise pH-modulated gastric controlled release from hydrophobic polybasic gels may be difficult to achieve. These gels may be more suitable in cases where pH-triggered release is desired, but precise rate control is not warranted.

Genotype and phenotype of NAT2 and the occurrence of adverse drug reactions in Mexican individuals to an isoniazid-based prophylactic chemotherapy for tuberculosis

Isoniazid (INH) is a drug extensively used as a prophylactic and therapeutic agent for human tuberculosis (TB). INH is metabolized by the enzymatic activity of N-acetyltransferase 2 (NAT2). Human NAT2, encoded by a highly polymorphic gene, is involved in the biotransformation of xenobiotics, including drugs and certain chemical carcinogens. Numerous studies have established the correlation between the acetylator phenotype and the NAT2 genotype in several populations; however, little is known regarding Latin-American populations and the pharmacogenetics of NAT2. Here, we report the molecular genotyping of the NAT2 gene, the acetylator phenotype, and the incidence of INH-related adverse reactions in a group of 25 Mexican individuals enrolled in a prophylactic protocol for TB. Using both the NAT2 genotyping and acetylation phenotyping approach, we found a ratio of 69.2 and 30.8% of slow and fast acetylators, respectively. Concordance of the NAT2 genotype and phenotype classification was 88% in the bimodal model. Regarding INH-related adverse reactions, only 2 individuals (8%) exhibited declared gastric intolerance. In our study group, we found an association between the NAT2 genotype and acetylator phenotype (OR=7.78, 95% CI, 0.87-87.98, Fishers exact test, p<0.05), but did not find any genotype or phenotype association with the incidence of INH-related adverse reactions (Fishers exact test, p>0.05).

Synthesis and polymerization of carboxyalkylmethacrylates: new hydrophobic polyelectrolytes

This paper describes the synthesis of the following methacrylic acid monomers with aliphatic spacers: methyl methacryloyloxyethanoate (MMOE), methyl 4-methacryloyloxybutanoate (M4MOB), methyl 6-methacryloyloxyhexanoate (M6MOH), methyl 10-methacryloyloxydecanoate (M10MOD), and methyl 11-methacryloyloxyundecanoate (M11MOU). The preparation of the respective linear polymers from these monomers, their characterization, and their conversion, via selective saponification, to five new hydrophobic polyelectrolytes are also described. With an increasing number of methylene spacers, the glass transition temperature of the polymers drops, as well as that of the polyelectrolytes, yielding polymeric materials with varied physical states. The developed hydrophobic polyelectrolytes show cloud points in aqueous NaCl solutions at different pH values, making them potential candidates for new pH-sensitive materials.

Oxidative folding and reductive activities of EhPDI, a protein disulfide isomerase from Entamoeba histolytica

PDI enzymes are oxidoreductases that catalyze oxidation, reduction and isomerization of disulfide bonds in polypeptide substrates. We have previously identified an E. histolytica PDI enzyme (EhPDI) that exhibits oxidase activity in vivo. However, little is known about the specific role of its redox-related structural features on the enzymatic activity. Here, we have studied the in vivo oxidative folding of EhPDI by mutagenic analysis and functional complementation assays as well as the in vitro oxidative folding and reductive activities by comparative kinetics using functional homologues in standard assays. We have found that the active-site cysteine residues of the functional domains (Trx-domains) are essential for catalysis of disulfide bond formation in polypeptides and proteins, such as the bacterial alkaline phosphatase. Furthermore, we have shown that the recombinant EhPDI enzyme has some typical properties of PDI enzymes: oxidase and reductase activities. These activities were comparable to those observed for other functional equivalents, such as bovine PDI or bacterial thioredoxin, under the same experimental conditions. These findings will be helpful for further studies intended to understand the physiological role of EhPDI.

Biocompatibility Evaluation of Electrospun Scaffolds of Poly (L-Lactide) with Pure and Grafted Hydroxyapatite

The objective of this work was to evaluate the biocompat- ibility of scaffolds of poly(L-lactide) with pure and grafted hydroxyap- atite, at various concentrations of reinforcement. The biocompatibility tests were carried out in vivo in Wistar rats by implanting the material into the subcutaneous and muscle tissues from 1 to 14 weeks and evaluating the surrounding tissue stained with hematoxylin-eosin. For in vitro assays, MTT and neutral red assay were used to evaluate any cytotoxicity in Mioblast Muscle C2C12 Cells (ATCC® CRL-1772™) and Bovine Coronary Artery Endothelial Cells (BCAEC); Escherichia coli and Staphylococcus aureus were used to evaluate bacterial adhe- sion. All variants of scaffolds provoked a mild inflammatory response, without showing necrosis. No evidence of cytotoxicity was presented in cell viability tests and good bacterial cell adhesion was visualized for all of the materials studied.