The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol

[EN] Poly(2-amino-4-tert-butylphenol), poly(2A-4TBP), was synthesized from monomer aqueous solution using either electrochemical or chemical oxidation procedures. Several spectroscopic characterization techniques were employed to gain information on the chemical structure and redox behavior of the obtained materials. It was found that the chemical polymerization product could be described as an oligomer mixture containing up to 16 monomer units. In parallel to other polymers derived from o-aminophenol, phenoxazine rings constitute also the basic structure of poly(2A-4TBP). In addition, the occurrence of N-N couplings, which are favored by the presence of the voluminous tert-butyl substituent, seems also relevant. No significant structural differences were found between the chemically or electrochemically synthesized materials. © 2016 Published by Elsevier Ltd.Financial support from the Spanish Ministerio de Economía y Competitividad and FEDER funds (MAT2013-42007-P) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged. M. Abidi thanks the Ministry of Higher Education and Scientific Research of Tunisia for funding her stay at the University of Alicante.Abidi, M.; López-Bernabeu, S.; Huerta, F.; Montilla-Jiménez, F.; Besbes-Hentati, S.; Morallón, E. (2016). The chemical and electrochemical oxidative polymerization of 2-amino-4-tert-butylphenol. Electrochimica Acta. 212:958-965. https://doi.org/10.1016/j.electacta.2016.07.060S95896521

Electrochemical Micro-sensors for Probing Bacterial Metabolic Behavior with Scanning Electrochemical Microscopy

Dental plaque is one of the well-characterized biofilms in the human body. Oral bacterial species play vital roles in maintaining healthy bacterial homeostasis as well as causing oral infections. Many of the oral diseases are caused by opportunistic pathogens, and therefore, the bacterial metabolic activities become important in dictating their survival and pathogenesis. Chemical changes related to the bacterial metabolic activity are limited to their local environment, which extends only up to a few hundred micrometers away from their biofilm surface. To study those chemical changes, a highly precise analytical technique which can reach to the bacterial local environment is required. Scanning electrochemical microscopy (SECM) is an ideal tool to study bacterial local chemical changes because of its noninvasive nature and its ability to reach into the bacterial local environment without disturbing the bacterial metabolism or their local environment. To use SECM for bacterial metabolic studies, SECM probes with ultra-micro electrodes (UME) which can quantify metabolites or metabolic byproducts with high selectivity and sensitivity are required. Streptococcus mutans (S. mutans) is the main contributing species for dental caries formation, one of the most prevalent chronic diseases among human across the globe. They catabolize sugars (sucrose, glucose) producing lactic acid, which decreases the pH of their local environment. For probing the metabolic behavior of this bacteria, highly selective, ultra-micro enzymatic glucose and lactate sensors have been developed. Glucose oxidase and lactate oxidase enzymes were covalently immobilized on to 25 µm Platinum (Pt) UMEs modified with a new enzyme immobilization matrix. New immobilizing matrix was made up of functionalized carbon nanotubes and ionic liquid composite. At 37 oC, in artificial saliva solutions, the developed glucose sensor shows a sensitivity of 94.44 (±18.55) µA.mM-1.cm-2 (0.1mM -1.0 mM) with a linear range, up to 4.0 mM and the lactate sensor shows a sensitivity of 139.8 (±10.43) µA.mM-1.cm-2 (10 µM to 0.25 mM) with a linear range up to 1.0 mM. These new sensors have fast response times (~2.0 S) which make them ideal to use in SECM probes for real-time metabolite quantification. S. mutans’s glucose uptake behavior provides information on their metabolic rate and the effect of their metabolism on other oral bacterial species. To quantify glucose consumption of S. mutans bacteria, a new SECM probe with a glucose microsensor was fabricated by selectively modifying one of the 25 µm Pt UME of a dual-tip SECM probe into the glucose sensor. It was observed that S. mutans glucose consumption decreased the local glucose concentration by 81 %. In a mixed diet condition, where both glucose and sucrose were available, bacterial glucose consumption decreased by 73 %, showing that, the bacteria preferentially uptake sucrose over glucose. The glucose concentration profile extended up to about 600 µm - 800 µm from the biofilm surface, creating a nutrient competitive environment for other species. Oral bacterial metabolic activity results in multiple chemical changes in their local environment. To study the bacterial metabolic activity related local chemical changes in bacterial environment, multifunctional SECM probes were designed. S. mutans consume carbohydrates producing lactic acid, increasing their local lactate concentration and decreasing the local pH. To quantify their glucose consumption and corresponding local pH change, a new Pt-glucose-pH SECM probe was designed. For this, a SECM probe consists of three 25 µm Pt UMEs were fabricated. One UME was modified into a glucose sensor, and the second UME was modified into a pH sensor by depositing iridium oxide (IrOx). Third Pt UME was used to obtain the probe approach curve. Similarly, for simultaneous quantification of local lactate concentration and corresponding pH, new Pt-lactate-pH probe was fabricated by combing the lactate microsensor, and IrOx deposited pH sensor. S. gordonii bacteria increase local peroxide concentration upon glucose catabolism. To quantify their glucose consumption and corresponding peroxide production, glucose-peroxide-Pt SECM probe was fabricated by combining the glucose sensor with a platinized-Pt peroxide sensor. These newly designed multifunctional SECM probes were successfully used for simultaneous quantification of multiple analytes in the bacterial local environment

Detection of prostate cancer biomarker using molecularly imprinted polymers

Successful treatment of prostate cancer (PCa) depends on early diagnosis and screening, which currently relies on the measurement of serum prostate specific antigen (PSA) levels. The overarching aim of the project was to generate molecularly imprinted polymers for PCa biomarkers, with subsequent integration with a sensing platform to allow for rapid, point of care detection and monitoring. The initial work involved the use of simple PSA epitopes for epitope imprinting using conventional imprinting techniques. A four amino acid sequence from the Cterminus of PSA was imprinted with MAA, Aam and Urea monomers to obtain bulk imprinted polymers. Apparent Kd of 102 μM, 154 μM, 194 μM was obtained for MAA, AAm, Urea based bulk mini-MIPs respectively. Epitope imprinting was further developed using a surface imprinting approach, via electropolymersiation of dopamine to detect an epitopic sequence from pro-PSA. An improvement in Kd from bulk-imprinted polymers, with an apparent Kd of 2.9 μM was obtained with the surface electrochemical MIP sensor. However, both epitope imprinting technique lacked sensitivity to measure clinical relevant concentrations of PSA (nM range). As a consequence, a more sophisticated technique called hybrid imprinting was developed to build an electrochemical MIP sensor. Hybrid MIP imprinting utilised an aptamer with established affinity towards PSA to trap the aptamer-PSA complex into a surface grown electropolymer (polydopamine). The resulting aptamer lined polymer pockets exhibited high selectivity and affinity towards PSA (apparent Kd 0.3 nM). The apta-MIP sensor was also able to discriminate from a homologous protein (human Kallikrein 2) and was resilient to fouling from serum proteins. The apta-MIP sensor was further translated to a MOSFET device whereby successful detection of PSA at clinically relevant concentration was obtained in human plasma. Although good sensitivity and selectivity was obtained with the hybrid-MIP sensors, further research is required to understand the binding mechanism of the template to the MIP

MODIFIKASI SPCE (SCREEN PRINTED CARBON ELECTRODE) DENGAN PEDOT-PSS (POLY (3,4-ETHYLENEDIOXYTHIOPHENE) POLY (STYRENE SULFONIC ACID)) UNTUK PENENTUAN FENOL

Pada penelitian ini, modifikasi Screen Printed Carbon Electrode (SPCE) secara fisik dilakukan dengan menggunakan poly (3,4-ethylenedioxythiophene) -poly (styrene sulfonic acid) (PEDOT-PSS) untuk meningkatkan sensitivitas penentuan fenol secara voltametri. Pengukuran fenol dilakukan dengan metode differential pulse voltammetry (DPV) pada kisaran potensial -0,5 sampai 1 Volt, durasi 180 detik, potensial deposisi -0,5 Volt, dan kecepatan penyapuan 100 mV/s pada pH 6-9, rentang konsentrasi fenol 0-100 mikro M, serta konsentrasi PEDOT-PSS sebesar 0-100%. Berdasarkan hasil penelitian, peningkatan konsentrasi PEDOT-PSS berpengaruh terhadap respon arus. Kondisi optimum dicapai pada pH 8 dengan konsentrasi PEDOT-PSS 50%, sensitivitas sebesar 0.009 mikro A/mikro M dengan batas deteksi 0.1595 mikro M

Surface Functionalized Mesoporous Silica Nanoparticles for Enhanced Removal of Heavy Metals: A Review

Human health and environmental sustainability are strongly influenced by the contamination of water resources with hazardous heavy metal ions due to the accumulation in human body via food chains. Thereby, researchers’ attention has been paid on effective methods for heavy metal ion scavenging to prevent them releasing to environment. Notably, Mesoporous Silica Nanoparticles (MSNPs) with high surface area, massive surface area to volume ratio, large pore volume and uniform pore distribution play a crucial role in addressing this challenge. Additionally, researchers focus on novel surface functionalization methods of MSNPs with suitable organic and inorganic moieties to amplify the adsorption efficiency of heavy metals. MSNPs possess easily functionalizable surface which facilitates the modifications and enhanced removal of heavy metals. The review article summarizes the different moieties used for functionalization of MSNPs such as amino, thio, carboxyl, phenyl, cyano groups, different types of polymers, inorganic functional groups. Further, a comparison has been made between functional and unmodified MSNPs to elaborate how these modifications have enhanced the removal performance of heavy metals in water. Further, this review provides an overview on different synthesis routes and structure directing agent used in synthesis of MSNPs. Moreover, pH effect on adsorption andreusability of modified NPs, while illustrating the mechanism of adsorption on to modified MSNPs surface has also been elaborated. Maximum adsorption capacity of each functional moiety has been taken into consideration with the aim of supporting future advancements. Keywords: Adsorption, Mesoporous silica nanoparticles, Heavy metals, Functionalization, Maximum adsorption capacit

Plastic Antibodies for the detection of Bacterial Proteins and Microorganisms

El diagnosi de moltes malalties és de vital importància per proporcionar el tractament adequat i per tant per controlar les necessitats de salut públiques. Els mètodes estàndard que es fan servir per confirmar la presència de microorganismes consisteixen típicament en l’ús de mètodes de cultiu específics per multiplicar, separar, identificar i comptar les bactèries. La durada d’aquests processos depèn del microorganisme en concret, però en molts casos un resultat confirmatori pot tardar entre uns pocs dies o inclús vàries setmanes. Un dels principals objectius en aquesta àrea és la detecció ràpida de microorganismes, d’una forma acurada i barata. Els polímers d’impremta molecular (PIMs) ofereixen una alternativa robusta i econòmica als anticossos naturals, però encara es requereix el seu desenvolupament pel reconeixement de molècules de gran mida. En aquesta tesi presentem diferents polímers d’impremta molecular amb l’objectiu de desenvolupar una nova aproximació per detectar proteïnes de la superfície de bactèries i microorganismes, aproximació basada en anticossos artificials utilitzats en la construcció de dispositius portàtils i econòmics. Aquests objectius generals s’assoleixen implementant una sèrie d’objectius específics: i. desenvolupament d’un camí simple per la construcció d’anticossos artificials utilitzant processos d’impremta molecular, ii. aplicació d’impedimetria, voltametria d’ona quadrada i potenciometria com a tècniques de detecció conjuntament amb una capa sensora formada per polímers d’impremta molecular, iii. ús d’elèctrodes comercials i de fabricació casolana per la detecció electroquímica en la cerca de dispositius portables i d’un sol ús, iv. impressió molecular i detecció de proteïnes de superfície de bactèries i/o microorganismes.La diagnosis de muchas enfermedades es de vital importancia para proporcionar el tratamiento adecuado y por lo tanto para el control de las necesidades de salud públicas. Los métodos estándar utilizados en la confirmación de la presencia de microorganismos consisten típicamente en el uso de métodos de cultivo específicos para multiplicar, separar, identificar y contar las bacterias. La durada de estos procesos depende del microorganismo en concreto, pero en muchos casos se necesitan entre pocos días o incluso varias semanas para tener una confirmación del resultado. Uno de los principales objetivos en esta área es la detección rápida de microorganismos, de una forma fiable y barata. Los polímeros de impronta molecular (PIMs) ofrecen una alternativa robusta y económica a los anticuerpos naturales, pero aún se requiere su desarrollo para el reconocimiento de moléculas de elevado tamaño. En esta tesis presentamos diferentes polímeros de impronta molecular con el objetivo de desarrollar una nueva aplicación para detectar proteínas de la superficie de bacterias y microorganismos, aproximación basada en anticuerpos artificiales utilizados en la construcción de dispositivos portátiles y económicos. Estos objetivos generales se consiguen implementando una serie de objetivos específicos: i. desarrollo de un camino simple para la construcción de anticuerpos artificiales utilizando procesos de impronta molecular, ii. aplicación de impedimetría, voltamperometría de onda cuadrada y potenciometría como técnicas de detección conjuntamente con una capa sensora formada por polímeros de impronta molecular, iii. uso de electrodos comerciales y de fabricación casera para la detección electroquímica en la búsqueda de dispositivos portátiles y de un solo uso, iv. impresión molecular y detección de proteínas de superficie de bacterias y/o microorganismos.The diagnosis of most illnesses is of vital importance for providing the appropriate cure and hence controlling public health concerns. The standard methods that are used to confirm the presence of microorganisms typically consist of specific enrichment media to multiply, separate, identify and count bacterial cells. The duration of the process depends on the microorganism, but in most cases a confirmatory result can take from a few days to even weeks. One of the major objectives in this area is to detect microorganisms quickly, accurately and cheaply. Molecularly imprinted polymers (MIPs) offer in principle a robust, cost-efficient alternative to natural antibodies, but it is still a challenge to develop such materials for large molecule recognition. In this thesis we present a variety of molecular imprinting approaches with an aim to develop a new approach for detecting bacterial surface proteins and microorganisms based on artificial antibodies for the construction of label-free and cost-effective portable devices. These general objectives are achieved by implementing a series of specific objectives: i. development of an easy pathway to make artificial antibodies by molecular imprinting process, ii. application of impedimetry, square wave voltammetry and potentiometry as detection techniques using molecularly imprinting polymers as the sensing layer, iii. use of homemade and commercially available screen-printed electrodes for the electrochemical detection of targets in the search for disposable and portable devices iv. electrochemical imprinting and detection of bacterial surface proteins and/or microorganisms

Pyrenylpyridines: Sky-Blue Emitters for Organic Light-Emitting Diodes

A novel sky-blue-emitting tripyrenylpyridine derivative, 2,4,6-tri(1-pyrenyl)-pyridine (2,4,6-TPP), has been synthesized using a Suzuki coupling reaction and compared with three previously reported isomeric dipyrenylpyridine (DPP) analogues (2,4-di(1 pyrenyl)pyridine (2,4-DPP), 2,6-di(1-pyrenyl)pyridine (2,6-DPP), and 3,5-di(1-pyrenyl)-pyridine (3,5-DPP)). 0 revealed by single-crystal X-ray analysis and computational simulations, all compounds possess highly twisted conformations in the solid state with interpyrene torsional angles of 42.3 degrees-57.2 degrees. These solid-state conformations and packing variations of pyrenylpyridines could be correlated to observed variations in physical characteristics such as photo/thermal stability and spectral properties, but showed only marginal influence on electrochemical properties. The novel derivative, 2,4,6-TPP, exhibited the lowest degree of crystallinity as revealed by powder X-ray diffraction analysis and formed amorphous thin films as verified using grazing-incidence wide-angle X-ray scattering. This compound also showed high thermal/photo stability relative to its disubstituted analogues (DPPs). Thus, a nondoped organic light-emitting diode (OLED) prototype was fabricated using 2,4,6-TPP as the emissive layer, which displayed a sky-blue electroluminescence with Commission Internationale de L\u27Eclairage (CIE) coordinates of (0.18, 0.34). This OLED prototype achieved a maximum external quantum efficiency of 6.0 +/- 1.2% at 5 V. The relatively high efficiency for this simple-architecture device reflects a good balance of electron and hole transporting ability of 2,4,6-TPP along with efficient exciton formation in this material and indicates its promise as an emitting material for design of blue OLED devices

Is the biocompatibility of copper with polymerized natural coating dependent on the potential selected for the electropolymerization process?

With the intention of taking care of the environment and human health, the development of alternative eco-friendly methods to inhibit metal corrosion is intensively encouraged. In previous works we showed that some phytocompounds components of essential oils such as carvacrol (Carv) and thymol (TOH) are able to be electropolymerized on metals and they seem to be promissory for this purpose. The aim this paper is to investigate if the biocompatibility of copper covered by coatings formed by electropolymerization of Carv and TOH (polyCarv and polyTOH) is related with the potential selected for the electropolymerization process. Potentiostatic perturbations at different potentials, AFM images, ATR-FTIR spectroscopy and measurements of copper ions release provided suitable information to make a detailed analysis of different stages of the electropolymerization process that leads to polyCarv and polyTOH layers on copper surface. The change of the characteristics of the coatings over time was evaluated after several polymerization periods and current transients were interpreted by using nucleation and growth models. Results showed interesting changes in the polymerization process with the electrochemical perturbation, nature of the isomer, and time of the treatment. The treatment that provides the most protective, transparent and homogeneous layer, that strongly increased the biocompatibility of Cu could be selected: electropolymerization of Carv at 0.4 V. Results highlight the importance of the detailed study of the evolution of the electropolymerization processes to select the best ecofriendly condition due the high impact of potential perturbation and polarization time on the biocompatibility of the resulting polymeric layer-copper system.Facultad de IngenieríaInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Construção de um sensor eletroquímico molecularmente impresso para monitorização do cancro da mama

O Cancro da mama é uma doença cuja incidência tem vindo a aumentar de ano para ano e além disso é responsável por um grande número de mortes em todo mundo. De modo a combater esta doença têm sido propostos e utilizados biomarcadores tumorais que permitem o diagnóstico precoce, o acompanhamento do tratamento e/ou a orientação do tipo tratamento a adotar. Atualmente, os biomarcadores circulantes no sangue periférico recomendados pela Associação Americana de Oncologia Clinica (ASCO) para monitorizar os pacientes durante o tratamento são o cancer antigen 15-3 (CA 15-3), o cancer antigen 27.29 (CA 27.29) e o cancer embryobic antigen (CEA). Neste trabalho foi desenvolvido um sensor eletroquímico (voltamétrico) para monitorizar o cancro da mama através da análise do biomarcador CA 15-3. Inicialmente realizou-se o estudo da adsorção da proteína na superfície do elétrodo para compreender o comportamento do sensor para diferentes concentrações. De seguida, estudaram-se três polímeros (poliaminofenol, polifenol e polifenilenodiamina) e selecionou-se o poliaminofenol como o polímero a utilizar, pois possuía a melhor percentagem de alteração de sinal. Após a seleção do polímero, este foi depositado na superfície do elétrodo por eletropolimerização, formando um filme polimérico molecularmente impresso (MIP) à volta da proteína (molde). Posteriormente, foram analisados cinco solventes (água, mistura de dodecil sulfato de sódio e ácido acético, ácido oxálico, guanidina e proteinase K) e o ácido oxálico revelou ser mais eficaz na extração da proteína. Por último, procedeu-se à caraterização do sensor e analisou-se a resposta analítica para diferentes concentrações de CA 15-3 revelando diferenças claras entre o NIP (polímero não impresso) e o MIP.Breast cancer is a disease with an incidence that has been increasing over the years and is responsible for a high number of deaths worldwide. In order to control this disease several tumor biomarkers have been proposed and used to enable early diagnostics, patient follow-up and/or treatment guidance. Currently, the circulating biomarkers (in peripheral blood) that are recommended by American Society of Clinical Oncology (ASCO) for monitoring patients during treatment are cancer antigen 15-3 (CA 15-3), cancer antigen 27.29 (CA 27.29) and cancer embryonic antigen (CEA). In this project an electrochemical (voltammetric) sensor for monitoring breast cancer was developed through the analysis of CA 15-3. Firstly, a protein adsorption study on the working electrode surface was carried out to understand the behavior of the sensor toward several protein concentrations. Subsequently, 3 polymers were studied (polyaminophenol, polyphenol and poly (phenylenediamine)) and polyaminophenol was selected as the polymer with the best percentage of signal change. Then, the polymer was electropolymerized on the working electrode surface resulting in a molecularly imprinted polymer film (MIP) of the protein (template). Afterwards, five solvents to extract the protein after incubation were studied (water, mixture of sodium dodecyl sulfate and acetic acid, oxalic acid, proteinase K and guanidine) in order to understand which one would be the most effective. For this purpose oxalic acid was chosen. Finally, the developed sensor was characterized by evaluating the analytical response for different concentrations of CA 15-3, which revealed clear differences between the MIP and NIP (non-imprinted polymer)