Towards the development of multisensor for drugs of abuse based on molecular imprinted polymers

The synthetic receptors for cocaine, deoxyephedrine, methadone and morphine were computationally designed and produced using molecular imprinting. The structure and energy of the molecular complexes were analysed by computational techniques. The possible structures of the binding sites in the synthetic receptors have been compared with those of corresponding natural receptors. The composition of imprinted polymers was optimised to allow adequate performance under the same experimental conditions. All selected molecular imprinting polymers (MIPs) demonstrated stronger affinity in comparison with corresponding blank polymers resulting in imprinted factors (I) equal to 1.2 (cocaine), 2.5 (deoxyephedrine), 3.5 (methadone) and 3 (morphine) which suggested that the specific binding site for each molecule was successfully created. The polymers studied possessed good selectivity and affinity towards their templates and could be recommended for the integration with sensor devices. From a practical point of view, especially for multisensor requirements, the synthetic receptors based on imprinted polymers could be superior to natural receptors due to their stability, robustness and compatibility with automation processes required for sensor fabrication.     

Characterisation of fresh and aged terpenic resins by micro-FTIR and GC-MS analyses of varnishes in XVI-XVII centuries paintings

Resinous materials, generally added to drying oils, were often employed as final protective films in paintings, both in tempera and oil techniques. Most of the resins used in fine arts come from exudates of plants. Natural resins are mainly composed by terpenoids. Among these resins, dammar, rosin, mastic, elemi gum, Venice turpentine were frequently employed in easel paintings. The aim of this work is the identification of natural resins in samples collected from works of art. In this paper we propose to use micro-FTIR spectrometry as a preliminary and non destructive technique to detect the presence of resinous materials in microsamples collected from paintings, followed by GC-MS analyses to obtain a precise identification of the resin. To reach this aim commercial resins, employed as standard, were analysed previously by micro-FTIR spectrometry and then analysed by GC-MS chromatography, searching characteristic chemical compounds used as "markers" of resins. The results obtained on standards allowed us to successfully analyse samples collected from two works of art: the "Portrait of a Young Gentleman", by Lorenzo Lotto (XVI century), and the "Madonna with the Infant Jesus and Saints": by Carlo Maratta (XVII secolo).     

Synthesis and screening of a molecularly imprinted polymer library targeted for penicillin G

A library of molecularly imprinted polymers (MIPs) was synthesized by radical bulk polymerization using the beta-lactam antibiotic penicillin G as the template. Diversity of the library was obtained by combining various functionalized monomers and cross-linkers and by varying the stoichiometry and the concentration of the components in the prepolymerization mixtures. The library was screened for selectivity to penicillin G by a radioligand binding assay and was compared to a corresponding control library. The best MIP candidate, showing the highest selectivity for penicillin G, was prepared from methacrylic acid and trimethylolpropane trimethacrylate as the functionalized monomer and cross-linker, respectively. Cross-reactivity studies with other beta-lactam antibiotics showed a low cross-reactivity of penicillin V (15%), ampicillin (16%), and amoxicillin (19%). Nafcillin and oxacillin showed less cross-reactivity (<1%). Cross-reaction with a cephalosporin antibiotic (cephapirin) and structurally nonrelated antibiotics (chloramphenicol, tetracycline, dapsone, and erythromycin) was less than 0.01%.     

Express detection of nonylphenol in water samples by fluorescence polarization immunoassay

The development of express method for detection of endocrine-disrupting chemicals (EDC) such as alkylphenols is required for ecological monitoring. Several attempts have been made to produce antibodies against 4-nonylphenol (NP) in recent years. This work describes the production of new antibodies against NP and also summarizes the characterization of antibodies obtained earlier. Three approaches used to produce alkylphenol-specific antibodies are compared; these are based on: 1. omega-(4-hydroxyphenyl)nonanoic or omega-(4-hydroxyphenyl)heptanoic acid NP derivatives designed to mimic the linear NP isomer; 2. 4-aminophenol, which potentially mimics various substituted phenolic compounds with different side-chain structures at position 4 of the benzene ring; and 3. a mixture of branched NP isomers, conjugated to the carrier protein via a benzene ring by the Mannich reaction, and expected to be the closest mimic of NP structure by preserving its natural alkyl moiety.Fluorescence polarization immunoassays based on different combinations of antibody and labeled antigen for screening detection of NP were developed and structural aspects of assay sensitivity and specificity were investigated. The assays based on the antisera raised against omega-(4-hydroxyphenyl)nonanoic acid and NP conjugate via Mannich reaction are capable of express detection of NP with detection limit of 7 microg mL(-1 )and assay dynamic range of 18-300 microg mL(-1).     

Bead injection for surface enhanced Raman spectroscopy: automated on-line monitoring of substrate generation and application in quantitative analysis

The technique of bead injection has been adapted for surface enhanced Raman scattering (SERS) to substantially improve precision, long term stability and sensitivity of SERS detection in analytical chemistry. For this purpose a fully automated flow system comprising a dedicated flow-cell has been developed and tested. With the developed flow-cell, which contains two inlet and two outlet channels, it is possible to retain, perfuse and discharge minute amounts of polymer beads while monitoring all steps by Raman spectroscopy. First, beads carrying cation exchanger moieties were retained in the flow-cell and subsequently perfused with a silver nitrate and a hydroxylamine solution using one inlet of the flow cell. By this sequence homogeneous SERS active silver layers were formed on the beads. The uniformity of the achieved silver layer was studied by secondary electron microscopy. For measurement, the analyte was then introduced from the second inlet channel such that the interaction between the activated SERS beads and analyte occurred in close proximity and within the focus of the laser excitation beam. Due to the complete computer control of all experimental steps, including bead entrapment, SERS layer generation, sample introduction and final bead removal, highly reproducible conditions for SERS were achieved. The method was developed using 9-aminoacridine as a test molecule. Quantitative studies were carried out for 9-aminoacridine and acridine showing linear calibrations from 1-100 nmol l(-1) and 50-1,000 nmol l(-1), respectively, using a sample volume of 200 microl each. Typical relative standard deviations were 4.7% for 9-aminoacrine and 5.8% for acridine.     

Synthesis of new polycyclic systems containing the pyrimido[2,1-a]phthalazine skeleton

The synthesis of new polyheterocycles containing the pyrimido[2,1-a]phthalazine system 5, 6 and 7 , obtained by condensation of phthalic anhydride with the appropriate hydrazides 2, 3 and 4 , respectively, are reported. It was also synthesized the 14H-[1]Benzothieno[3′,2′:4,5]pyrimido[2,1-a][1,2,4]triazolo[4,3-c]phthalazin-14-one (16).     

A study of the interaction of dodecyl sulfobetaine with cationic and anionic surfactant in mixed micelles and monolayers at the air/water interface

The miscibility and interactions between components in mixed adsorbed films and micelles containing zwitterionic (dodecyl sulfobetaine--DSB) and cationic (dodecyltrimethylammonium bromide) or anionic (sodium dodecyl sulfonate) surfactant, respectively, have been investigated. The molecular interactions have been quantified by the values of the excess free energy of adsorption (DeltaGS,Exc) and micelle formation (DeltaGM,Exc). The obtained results indicate nonideal behavior of the investigated mixtures since the values of DeltaGS,Exc and DeltaGM,Exc) are negative. Moreover, it has been found that DSB interact more strongly with anionic surfactant as compared to cationic surfactant owing to different structure of mixed monolayers and micelles.     

Determination of moxifloxacin in tablets and human urine by square-wave adsorptive voltammetry

This work presents an electroanalytical methodology developed for square-wave voltammetry based in the electrochemical reduction in hanging mercury drop electrode (HMDE), which is simple, fast, reliable and sensitive for determination of moxifloxacin (MOXI) in tablets and spiked urine human samples. The support electrolyte that provided a more defined and intense peak current for MOXI determination was the phosphate buffer 0.04 mol l^{− 1} pH 8.0. In the best-optimized conditions the drug presented an only peak of reduction at − 1.38 V vs. Ag/AgCl, using an E_acc. of − 0.30 V. An LOD of 0.44 and 3.20 ng ml^{− 1} and an LOQ of 1.46 and 10.60 ng ml^{− 1} were found for the pure standard of moxifloxacin and in the presence of matrix, respectively. A good recovery was obtained for assay spiked urine samples and a good quantification of MOXI was achieved in a commercial formulation. The methodology proposed was more sensitive than the spectrofluorimetric and spectrophotometric method with precision and accuracy equivalent.     

Synthesis of N,N'-Diacyl-1,2-di-(4-pyridyl)ethylenedianiines

Reaction of N-(4-pyridylmethyl)benzamide N-oxides with acetic anhydride yielded dimerization compounds. This dimerization occurs at the atom attached to the pyridine ring. These compounds so obtained were evaluated for analgesic and antiinflammatory activity.