pH-induced changes in the fabrication of multilayers of poly(acrylic acid) and chitosan: fabrication, properties, and tests as a drug storage and delivery system

Multilayers of poly(acrylic acid), PAA, and chitosan, CHI, have been built by the layer-by-layer (LbL) method from aqueous solutions at different pH values and analyzed by the dissipative quartz crystal microbalance (D-QCM) and ellipsometry. The results showed that under all of the assembly conditions considered the growth of the films is nonlinear. The thickness of the PAA layers increases as the pH of the assembling solutions decreases, whereas the adsorption of CHI is almost unaffected by the pH conditions. The comparison of the thickness obtained by D-QCM and by ellipsometry has allowed us to calculate the water content of the films, showing that the multilayers are highly hydrated, with an average water content higher than 20%. The analysis of D-QCM data has provided high-frequency values of the complex shear modulus that are in the megapascal range and shows a transition from mainly viscous to mainly elastic behavior for the added PAA layers, depending on the pH. The monomer surface density in each layer (obtained from the combination of ellipsometry and differential refractive index measurements) indicated that the monomer density depends on the assembly conditions. It was found that the adsorption kinetics is a bimodal process, with characteristic times that depend on the number and nature of the layers. Finally, the possibility of using of these multilayers as a drug storage and delivery system has been evaluated.     

Classification and determination of total protein in milk powder using near infrared reflectance spectrometry and the successive projections algorithm for variable selection

This paper proposes a methodology for the classification and determination of total protein in milk powder using near infrared reflectance spectrometry (NIRS) and variable selection. Two brands of milk powder were acquired from three Brazilian cities (Natal-RN, Salvador-BA and Rio de Janeiro-RJ). The protein content of 38 samples was determined by the Kjeldahl method and NIRS analysis. Principal component regression (PCR) and partial least squares (PLS) multivariate calibrations were used to predict the total protein. Soft independent modeling of class analogy (SIMCA) was also used for full-spectrum classification, resulting in almost 100% classification accuracy, regardless of the significance level adopted for the F-test. Using this strategy, it was feasible to classify powder milk rapidly and nondestructively without the need for various analytical determinations. Concerning the multivariate calibration models, the results show that PCR, PLS and MLR-SPA models are good for predicting total protein in powder milk; the respective root mean square errors of prediction (RMSEP) were 0.28 (PCR), 0.25 (PLS), 0.11 wt% (MLR-SPA) with an average sample protein content of 8.1 wt%. The results obtained in this investigation suggest that the proposed methodology is a promising alternative for the determination of total protein in milk powder.     

Capillary electrophoresis time-of-flight mass spectrometry for a confident elucidation of a glycopeptide map of recombinant human erythropoietin

Capillary electrophoresis coupled to orthogonal accelerated time-of-flight mass spectrometry (CE/TOFMS) was used for the analysis of O- and N-glycopeptides of recombinant human erythropoietin (rhEPO). O(126) and N(83) with a tetraantennary complex type glycan (N(83)-4Ant) were selected as glycopeptide models to develop an optimum CE/TOFMS methodology capable of detecting and characterizing the wide variety of glycopeptides present in the glycoprotein digest. Glycopeptide adsorption in the inner surface of the fused-silica capillary was prevented after using a capillary conditioning of 1 M HAc between runs. On the other hand, different acidic conditions in the sheath liquid (SL) and in the background electrolyte (BGE) were tested with the aim of studying their influence in glycopeptide fragmentation. Finally, the fragmentor voltage value of the TOF-MS instrument was optimized to avoid the involuntary fragmentation of the native glycopeptides. Hence, the established method may be regarded as an excellent starting point to obtain reliable glycopeptide maps of complex glycoproteins such as rhEPO by CE/TOFMS.     

Direct monitoring of drug degradation by easy ambient sonic-spray ionization mass spectrometry: the case of enalapril

Using enalapril maleate as a test case, the ability of ambient mass spectrometry, namely, via easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS), to perform direct monitoring of drug degradation has been tested. Two manufacturing processes were investigated (direct compression and wet granulation), and the formation of degradation products was measured via both EASI‐MS and high‐performance liquid chromatography with ultraviolet detection for a total period of 18 months. Both techniques provide comparable results, which indicate that direct analysis by ambient mass spectrometric techniques presents a viable alternative for drug degradation monitoring with superior simplicity, throughput, and reliability (no sample manipulation), and comparable quantitative results. In terms of qualitative monitoring, the full mass spectra with intact species provided by EASI‐MS allow for comprehensive monitoring of known and unknown (or unexpected) degradation products. Copyright © 2011 John Wiley & Sons, Ltd.     

Catalyst-free synthesis of benzodiazepines and benzimidazoles using glycerol as recyclable solvent

We described herein the use of glycerol as solvent in the catalyst-free synthesis of benzodiazepines and benzimidazoles. This simple and efficient method furnishes the corresponding 1-H-1,5-benzodiazepines and 1,2-disubstituted benzimidazoles in good yields by the condensation of o-phenylenediamine with several ketones and aldehydes, respectively. In addition, glycerol can be easily re-utilized for further condensation reactions up to four times without lost of activity.     

Studies on the adsorption of cell impurities from plasmid-containing lysates to phenyl boronic acid chromatographic beads

Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins.     

Rapid detection of <Emphasis Type="Italic">Aspergillus flavus</Emphasis> in rice using biofunctionalized carbon nanotube field effect transistors

Popularity of new psychoactive substances, known as legal highs or herbal highs, is continuously growing. These products are typically sold via internet and in so-called head shops. The aim of this study was to identify active ingredients of herbal highs and to compare their chemical composition. Twenty-nine various products seized by the police in one of the “head shops” were analysed. Herbal mixtures (0.2 g) were prepared by ultrasonic-assisted extraction with 2.0 ml of ethanol for 2 h. The extracts were analysed by gas chromatography coupled to mass spectrometry (GC/MS). The main active compounds of the herbal mixtures were synthetic cannabinoids: JWH-018, JWH-073 and cannabicyclohexanol (CP-47,497-C8-homolog). Their content differed between the products; some contained only one cannabinoid whereas the others contained two or more. Cluster analysis and principal component analysis revealed that chemical composition of many products was very similar. The similarity was connected with their flavour and not the common name. This statement was true for the synthetic cannabinoids, other potential agonists of cannabinoid receptors (amides of fatty acids) and ingredients of natural origin and confirms that herbal highs are a threat to human health because the purchaser has no information on their real composition.     

Synthesis of (Z)-organylthioenynes using KF/Al2O3/solvent as recyclable system

PEG-400 and glycerol were successfully used as recyclable solvents for the synthesis of several organylthioenynes in good to excellent yields and high selectivity using solid supported catalyst (KF/Al₂O₃). This easy, general and improved method furnishes the corresponding alkenyl sulfides preferentially with Z configuration. The catalytic system and the glycerol or PEG-400 can be reused up to three times without previous treatment with comparable activity.