Simultaneous chiral separation using a combinatorial molecular imprinting phase

Molecular imprinting chiral stationary phase against Cbz-L-Serine (Cbz-L-Ser) and Cbz-L-Alaine (Cbz-L-Ala) were prepared utilizing acrylamide + 2-vinylpyridine as combined basic functional monomers. Cross-selectivity was used to obtain simultaneous chiral separations of Cbz-DL-Ser and Cbz-DL-Ala by connecting two columns packed with Cbz-L-Ser and Cbz-L-Ala imprinted chiral stationary phase, respectively.

High performance cocktail functional monomer for making molecule imprinting polymer

In order to make a molecule imprinting polymer (MIP) with highly chiral selectivity against N-t-Boc-L-Trp, a new kind of "cocktail" functional monomer: acrylamide+2-vinylpyridine was investigated. The MIP showed impressive chiral selectivity (alpha=3.23). With the increasing of water content in the mobile phase, ionic and hydrophobic interaction were found to be responsible for the chiral recognition process instead of the hydrogen bond. Tailing and peak asymmetry problems were overcome by using linear gradient elution. Physical properties such as thermal stability and pore structure for the MIP were also investigated.

New cocktail functional monomers in making molecule imprinting polymer with high chiral selectivity

in order td produce molecule imprinting polymer (MIP) with high chiral selectivity against N-c-protected amino acid, new cocktail functional monomers acrylamide (AM) + 2-vinylpyridine (2-VP) and AM + methacrylic acid (MAA) were investigated. AM + 2-VP was found to be more efficient in improving the selectivity and resolution of the molecule imprinting polymer.

Rapid protein identification using monolithic enzymatic microreactor and LC-ESI-MS/MS

A monolithic enzymatic microreactor was prepared in a fused-silica capillary by in situ polymerization of acrylamide, glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) in the presence of a binary porogenic mixture of dodecanol and cyclohexanol, followed by ammonia solution treatment, glutaraldehyde activation and trypsin modification. The choice of acrylamide as co-monomer was found useful to improve the efficiency of trypsin modification, thus, to increase the enzyme activity. The optimized microreactor offered very low back pressure, enabling the fast digestion of proteins flowing through the reactor. The performance of the monolithic microreactor was demonstrated with the digestion of cytochrome c at high flow rate. The digests were then characterized by CE and HPLC-MS/MS with the sequence coverage of 57.7%. The digestion efficiency was found over 230 times as high as that of the conventional method. in addition, for the first time, protein digestion carried out in a mixture of water and ACN was compared with the conventional aqueous reaction using MS/MS detection, and the former solution was found more compatible and more efficient for protein digestion.

Artificial receptors for the extraction of nucleoside metabolite 7-methylguanosine from aqueous media made by molecular imprinting

A series of imprinted polymers targeting nucleoside metabolites, prepared using a template analogue approach, are presented. These were prepared following selection of the optimum functional monomer by solution association studies using 1H-NMR titrations whereby methacrylic acid was shown to be the strongest receptor with and affinity constant of 621 ± 51 L mol-1 vs. 110 ± 16 L mol-1 for acrylamide. The best performing polymers were prepared using methanol as porogenic co-solvent and although average binding site affinities were marginally reduced, 2.3×104 L mol-1 vs. 2.7×104 L mol-1 measured for a polymer prepared in acetonitrile, these polymers contained the highest number of binding sites, 5.27 μmol g-1¬¬ vs. 1.64 μmol g-1, while they also exhibited enhanced selectivity for methylated guanosine derivatives. When applied as sorbents in the extraction of nucleoside derivative cancer biomarkers from synthetic urine samples, significant sample clean-up and recoveries of up to 90% for 7-methylguanosine were achieved.

Measurement of Donnan potentials in gels by in situ microelectrode voltammetry

This work describes the electrochemical methodology for the determination of the Donnan potential from diffusion-limited steady-state voltammograms of acrylamide gels. The technique is based upon the measurement of gel–sol systems that have reached Donnan equilibrium and contain Cd2+ as a probe ion. Au-amalgam microelectrodes are used to measure the Cd concentration in the gel phase relative to the solution phase, thus permitting comparison of the Cd voltammograms obtained in both phases. This approach yields two independent measures of the Donnan potential resulting from (i) the potential shift relative to the reference electrode, and (ii) the enhancement of the Cd2+ wave. Two suites of acrylamide gels containing 0.2% and 0.5% Na-acrylate were studied as a function of ionic strength by varying [NaNO3] and maintaining a constant concentration of the electroactive probe ion, [Cd2+] = 1 · 10 5 mol/L in the equilibrating solutions. Independent model predictions of the Donnan potential as a function of ionic strength that consider the effects of differential swelling on the charge density, the influence of a mixed electrolyte on the potential developed in the gel at the limit of low ionic strength and the effects of incomplete dissociation of the carboxylic functional groups were in agreement with the Donnan potentials independently measured by the twofold steady-state voltammetric approach.

Velocidade da corrosão do aço em argamassas cimentícias modificadas com polímeros

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Química

Novel biosensing device for point-of-care applications with plastic antibodies grown on Au-Screen Printed Electrodes

A gold screen printed electrode (Au-SPE) was modified by merging Molecular Imprinting and Self-Assembly Monolayer techniques for fast screening cardiac biomarkers in point-of-care (POC). For this purpose, Myoglobin (Myo) was selected as target analyte and its plastic antibody imprinted over a glutaraldehyde (Glu)/cysteamine (Cys) layer on the gold-surface. The imprinting effect was produced by growing a reticulated polymer of acrylamide (AAM) and N,N′-methylenebisacrylamide (NNMBA) around the Myo template, covalently attached to the biosensing surface. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies were carried out in all chemical modification steps to confirm the surface changes in the Au-SPE. The analytical features of the resulting biosensor were studied by different electrochemical techniques, including EIS, square wave voltammetry (SWV) and potentiometry. The limits of detection ranged from 0.13 to 8 μg/mL. Only potentiometry assays showed limits of detection including the cut-off Myo levels. Quantitative information was also produced for Myo concentrations ≥0.2 μg/mL. The linear response of the biosensing device showed an anionic slope of ~70 mV per decade molar concentration up to 0.3 μg/mL. The interference of coexisting species was tested and good selectivity was observed. The biosensor was successfully applied to biological fluids.

Surface Imprinting Approach on Screen Printed Electrodes Coated with Carboxylated PVC for Myoglobin detection with Electrochemical Transduction

A novel surface molecularly-imprinted (MI) material to detect myoglobin (Myo) using gold screen printed electrodes (SPE) was developed. The sensitive detection was carry out by introducing a carboxylic polyvinyl chloride (PVC-COOH) layer on gold SPE surface. Myo was attached to the surface of gold SPE/PVC-COOH and the vacant spaces around it were filled by polymerizing acrylamide and N,N-methylenebisacrylamide (cross-linker). This polymerization was initiated by ammonium persulphate. After removing the template, the obtained material was able to rebind Myo and discriminate it among other interfering species. Various characterization techniques including electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirmed the surface modification. This sensor seemed a promising tool for screening Myo in point-of-care.

Artificial antibodies for troponin T by its imprinting on the surface of multiwalled carbon nanotubes: Its use as sensory surfaces

A novel artificial antibody for troponin T (TnT) was synthesized by molecular imprint (MI) on the surface of multiwalled carbon nanotubes (MWCNT). This was done by attaching TnT to the MWCNT surface, and filling the vacant spaces by polymerizing under mild conditions acrylamide (monomer) in N,N′-methylenebisacrylamide (cross-linker) and ammonium persulphate (initiator). After removing the template, the obtained biomaterial was able to rebind TnT and discriminate it among other interfering species. Stereochemical recognition of TnT was confirmed by the non-rebinding ability displayed by non-imprinted (NI) materials, obtained by imprinting without a template. SEM and FTIR analysis confirmed the surface modification of the MWCNT. The ability of this biomaterial to rebind TnT was confirmed by including it as electroactive compound in a PVC/plasticizer mixture coating a wire of silver, gold or titanium. Anionic slopes of 50 mV decade−1 were obtained for the gold wire coated with MI-based membranes dipped in HEPES buffer of pH 7. The limit of detection was 0.16 μg mL−1. Neither the NI-MWCNT nor the MWCNT showed the ability to recognize the template. Good selectivity was observed against creatinine, sucrose, fructose, myoglobin, sodium glutamate, thiamine and urea. The sensor was tested successfully on serum samples. It is expected that this work opens new horizons on the design of new artificial antibodies for complex protein structures.

Desenvolvimento de um biossensor para Ácido Glutâmico

A presente dissertação tem com objetivo o desenvolvimento de um biossensor com base nos polímeros de impressão molecular para a deteção de uma molécula alvo, o ácido glutâmico que é convertido em glutamina pela glutamina sintetase, recorrendo à potenciometria. Nas células neoplásicas a glutamina não é sintetizada podendo-se considerar que o ácido glutâmico é um potencial agente anti-cancro. A técnica de impressão molécular utilizada foi a polimerização em bulk, combinando a acrilamida e a bis acrilamida com o ácido glutâmico. Para se verificar se a resposta potenciométrica obtida era de facto da molécula alvo foram preparados em paralelo com os sensores, materiais de controlo, ou seja, moléculas sem impressão molécular (NIP). Para se controlar a constituíção química dos vários sensores nomeadamente, do NIP e do polímero de impressão molecular (MIP) antes e após a remoção bem como a molécula foram realizados estudos de Espetroscopia de Infravermelhos de Transformada de Fourier (FTIR), Scanning electron microscope (SEM) e Espetroscopia de Raios X por dispersão em energia (EDS). Os materiais desenvolvidos foram aplicados em várias membranas que diferiam umas das outras, sendo seletivas ao ião. A avaliação das características gerais das membranas baseou-se na análise das curvas de calibração, conseguidas em meios com pHs diferentes, comparando os vários elétrodos. O pH 5 foi o que apresentou melhor resultado, associado a uma membrana que continha um aditivo, o p-tetra-octilphenol, e com o sensor com percentagem de 3%. Posto isto, testou-se em material biológico, urina, com as melhores características quer em termos de sensibilidade (18,32mV/década) quer em termos de linearidade (1,6x10-6 a 1,48x10-3 mol/L). Verificou-se ainda que aplicando iões interferentes na solução, estes não interferem nesta, podendo ser aplicados na amostra sem que haja alteração na resposta potenciométrica. O elétrodo é capaz de distinguir o ácido glutâmico dos restantes iões presentes na solução.

Variabilité Génétique des Populations Ouest-Africaines

Notre patrimoine génétique dévoile, de plus en plus, les passerelles démogénétiques d’une susceptibilité plus accrue de certains individus à des maladies infectieuses complexes. En vue d’une caractérisation de la variabilité génétique des populations ouest-africaines, nous avons analysé 659 chromosomes X au locus dys44 qui comprend, 35 SNPs et un microsatellite distribués sur 2853 pb en amont et 5034 pb en aval de l’exon 44 du gène de la dystrophine en Xp21.3. Les génotypes obtenus, par ASO dynamique et électrophorèse sur gel d’acrylamide, ont servi à la détermination des haplotypes. Des paramètres comme la diversité haplotypique (G) et l'indice de fixation (Fst) ont été calculés. Des analyses en composantes principales ainsi que multidimensionnelles ont été réalisées. Sur 68 haplotypes détectés, 26 sont nouveaux, et cette région, avec une diversité haplotypique moyenne (Gmoy) de 0,91 ± 0,03, se révèle beaucoup plus hétérogène que le reste du continent (Gmoy = 0,85 ± 0,04). Toutefois, malgré l’existence de disparités sous régionales dans la distribution des variants du marqueur dys44, l’AMOVA montre d’une manière générale, une faible érosion de l’éloignement génétique entre les populations subsahariennes (Fst = 1,5% ; p<10-5). Certains variants tel que l’haplotype eurasien B006 paraissent indiquer des flux transsahariens de gènes entre les populations nord-africaines et celles subsahariennes, comme l’exemplifie le pool génétique de l’une des populations ubiquitaires de la famille linguistique Nigéro-congolaise : Les Fulani. Nos résultats vont aussi dans le sens d’un héritage phylétique commun entre les Biaka, les Afro-américains et les populations de la sous-famille de langues Volta-Congo.

New stimuli-responsive block random copolymers and their aggregation

Les polymères sensibles à des stimuli ont été largement étudiés ces dernières années notamment en vue d’applications biomédicales. Ceux-ci ont la capacité de changer leurs propriétés de solubilité face à des variations de pH ou de température. Le but de cette thèse concerne la synthèse et l’étude de nouveaux diblocs composés de deux copolymères aléatoires. Les polymères ont été obtenus par polymérisation radicalaire contrôlée du type RAFT (reversible addition-fragmentation chain-transfer). Les polymères à bloc sont formés de monomères de méthacrylates et/ou d’acrylamides dont les polymères sont reconnus comme thermosensibles et sensible au pH. Premièrement, les copolymères à bloc aléatoires du type AnBm-b-ApBq ont été synthétisés à partir de N-n-propylacrylamide (nPA) et de N-ethylacrylamide (EA), respectivement A et B, par polymérisation RAFT. La cinétique de copolymérisation des poly(nPAx-co-EA1-x)-block-poly(nPAy-co-EA1-y) et leur composition ont été étudiées afin de caractériser et évaluer les propriétés physico-chimiques des copolymères à bloc aléatoires avec un faible indice de polydispersité . Leurs caractères thermosensibles ont été étudiés en solution aqueuse par spectroscopie UV-Vis, turbidimétrie et analyse de la diffusion dynamique de la lumière (DLS). Les points de trouble (CP) observés des blocs individuels et des copolymères formés démontrent des phases de transitions bien définies lors de la chauffe. Un grand nombre de macromolécules naturels démontrent des réponses aux stimuli externes tels que le pH et la température. Aussi, un troisième monomère, 2-diethylaminoethyl methacrylate (DEAEMA), a été ajouté à la synthèse pour former des copolymères à bloc , sous la forme AnBm-b-ApCq , et qui offre une double réponse (pH et température), modulable en solution. Ce type de polymère, aux multiples stimuli, de la forme poly(nPAx-co-DEAEMA1-x)-block-poly(nPAy-co-EA1-y), a lui aussi été synthétisé par polymérisation RAFT. Les résultats indiquent des copolymères à bloc aléatoires aux propriétés physico-chimiques différentes des premiers diblocs, notamment leur solubilité face aux variations de pH et de température. Enfin, le changement d’hydrophobie des copolymères a été étudié en faisant varier la longueur des séquences des blocs. Il est reconnu que la longueur relative des blocs affecte les mécanismes d’agrégation d’un copolymère amphiphile. Ainsi avec différents stimuli de pH et/ou de température, les expériences effectuées sur des copolymères à blocaléatoires de différentes longueurs montrent des comportements d’agrégation intéressants, évoluant sous différentes formes micellaires, d’agrégats et de vésicules.

Développement de nouveaux polymères amphiphiles comme floculants versatiles pour le traitement de l’eau issue de l’industrie pétrolière

Les polymères hydrosolubles sont utilisés dans diverses industries pour permettre la floculation, soit une séparation solide-liquide de particules présentes en suspension colloïdale. Afin de réduire les impacts environnementaux de l’exploitation des sables bitumineux en Alberta, l’industrie est à la recherche de nouveaux moyens et procédés pour traiter les résidus miniers permettant de séparer les matières solides et de récupérer l’eau. L’objectif des travaux présentés est d’améliorer la floculation, la densification et la déshydratation de ces résidus miniers aqueux par de nouveaux polymères synthétiques. Des homopolymères d’acrylamide de différentes masses molaires ont été synthétisés pour étudier l’influence de la masse molaire sur l’efficacité de floculation. Le taux initial de sédimentation (TIS) est le paramètre qui fut utilisé afin de comparer l’efficacité de floculation des différents polymères. Il a été possible de confirmer l’importance de la masse molaire sur l’efficacité de floculation et de déterminer une masse molaire minimale d’environ 6 MDa pour des polyacrylamides, afin d’obtenir l’efficacité de floculation maximale de suspensions colloïdales principalement composées de kaolin. Afin d’étudier l’effet des charges sur l’efficacité de floculation, des polymères anioniques et cationiques ont été synthétisés. Une série de copolymères d’acrylamide et d’acide acrylique ont été synthétisés comme polymères anioniques et deux séries de copolymères ont été synthétisés comme polymères cationiques, soit des copolymères d’acrylamide et de chlorure de diallyldiméthylammonium et des copolymères de 4-vinyl pyridine et de 1-méthyl-4-vinyl pyridinium. Il a été démontré que les charges anioniques des polymères avaient peu d’influence sur l’efficacité de floculation et que leur comportement en présence de sels était différent de ce que prévoyait la littérature. Il a aussi été démontré que les charges cationiques des polymères n’améliorent pas l’efficacité de floculation. Par la suite, des séries de copolymères amphiphiles, avec des monomères d’acrylamide, de N-alkylacrylamides et d’acrylonitrile, ont été synthétisés, pour étudier l’effet du caractère amphiphile sur la déshydratation des résidus miniers. Le pourcentage de déshydratation nette est le paramètre qui fut utilisé afin de comparer l’efficacité de déshydratation des différents polymères. Il a été possible de développer des copolymères amphiphiles qui améliorent l’efficacité de déshydratation par rapport à des homopolymères d’acrylamide. Il ne fut pas possible de déterminer une tendance entre la balance hydrophile/hydrophobe des copolymères amphiphiles et l’efficacité de déshydratation.

A new metal ion doped panchromatic photopolymer for holographic applications

This thesis has discussed the development of a new metal ion doped panchromatic photopolymer for various holographic applications. High-quality panchromatic holographic recording material with high diffraction efficiency, high photosensitivity and high spatial resolution is one of the key factors for the successful recording of true colour holograms. The capability of the developed material for multicolour holography can be investigated.In the present work, multiplexing studies were carried out using He-Ne laser (632.8 nm). Multiplexing can be done using low wavelength lasers like Ar+ ion (488 nm) and frequency doubled Nd: YAG (532 nm) lasers, so as to increase the storage capacity. The photopolymer film studied had a thickness of only 130 Cm. Films with high thickness (~500 Cm) is highly essential for competitive holographic memories . Hence films with high thickness can be fabricated and efforts can be made to record more holograms or gratings in the material.In the present study, attempts were made to record data page in silver doped MBPVA/AA photopolymer film. Image of a checkerboard pattern was recorded in the film, which could be reconstructed with good image fidelity. Efforts can be made to determine the bit error rate (BER) which provides a quantitative measure of the image quality of the reconstructed image . Multiple holographic data pages can also be recorded in the material making use of different multiplexing techniques.Holographic optical elements (HOEs) are widely used in optical sensors, optical information processing, fibre optics, optical scanners and solar concentrators . The suitability of the developed film for recording holographic optical elements like lenses, beam splitters and filters can be studied.The suitability of a reflection hologram recorded in acrylamide based photopolymer for visual indication of environmental humidity is reported . Studies can be done to optimize the film composition for recording of reflection holograms.An improvement in the spatial resolution of PVA/acrylamide based photopolymer by using a low molecular-weight poly (vinyl alcohol) binder was recently reported . Effect of the molecular weight of the binder matrix on the holographic properties of the developed photopolymer system can be investigated.Incorporation of nanoparticles into photopolymer system is reported to enhance the resolution and improve the dimensional stability of the system . Hence efforts can be made to incorporate silver nanoparticles into the photopolymer and its influence on the holographic properties can be studied.This thesis was a small venture towards the realization of a big goal, a competent holographic recording material with excellent properties for practical holographic applications. As a result of the present research, we could successfully develop an efficient panchromatic photopolymer system and could demonstrate its suitability for recording transmission holograms and holographic data page. The developed photopolymer system is expected to have significant applications in the fields of true-color display holography, wavelength multiplexing holographic storage, and holographic optical elements. Highly concentrated and determined effort has yet to be put forth for this expectation to become a reality.