Indium tin oxide synthesized by a low cost route as SEGFET pH sensor

Polycrystalline ITO films with good optoelectronics characteristics and homogeneous surface has been obtained upon annealing at 550 °C in N2 atmosphere using a low-cost chemical vapor deposition (CVD) system. The films were evaluated as pH sensors in separative extended gate field-effect transistor (SEGFET) apparatus, exhibiting a sensitivity of 53 mV/pH, close to the expected Nernstian theoretical value for ion sensitive materials. The use of CVD process to synthesize ITO, as described here, may represent an alternative for fabrication of SEGFET pH sensors at low cost to be used in disposable biosensors since H+ ions are the product of several oxireductase enzymes.CNPqCAPESFAPEMIGFAPES

Immobilization of enzymes in (sub) microstructured platforms for application in biosensors

Esta tese descreve a preparação, caracterização e desenvolvimento de biossensores baseados na imobilização de enzimas em filmes nanoestruturados. Os filmes foram obtidos pela técnica de automontagem do inglês Layer-by-Layer (LbL) ou pela técnica de Langmuir-Blodgett (LB). A tese se divide em três partes: a primeira parte teve como objetivo o estudo e a aplicação de filmes finos nanoestruturados, contendo enzima tirosinase (Tyr), em biossensores para detecção de moléculas antioxidantes (polifenóis), visando sua aplicação na indústria de alimentos, em especial a de vinhos tintos. Foi utilizada a técnica LB para a imobilização da enzima Tyr sobre substratos sólidos (ITO ou Pt) sem que a enzima perdesse sua atividade. A enzima foi incorporada a filmes LB mistos de ácido araquídico (AA) e bisftalocianina de lutécio (LuPc2) pela injeção na subfase aquosa. A LuPc2 foi usada como mediadora de transferência de cargas. Foi possível a detecção do composto fenólico representativo pirrogalol. Estudos de voltametría cíclica demonstraram que o biossensor possui uma boa reprodutibilidade com desvio padrão de ca. 2% (n = 4), limite dinâmico de até 400 \'mü\'M (potencial aplicado de 0,4 V; R2: 0,993), sensibilidade de 1,54 \'mü\'A.\'mü\'M POT.-1/\'CM POT.2\' e limite de detecção (critério 3\'sigma\'0/m) de 4,87 x \'10 POT.-2\' \'mü\'M (n = 10). A segunda parte do trabalho descreve o desenvolvimento de sensores eletroquímicos baseados em filmes automontados LbL de hidrocloreto de polialilamina (PAH) e LuPc2. A motivação para o estudo foi a troca do material biológico (Tyr) pela LuPc2, a qual possui poder catalítico e relativa seletividade, capaz de mimetizar algumas proteínas. A LuPc2 foi utilizada como enzima artificial na quantificação de catecol e pirogalol como representantes de compostos fenólicos. Em medidas de voltametria, o sensor automontado de PAH/LuPc2 apresentou boa linearidade (R2 = 0,992) na faixa de até 500 \'mü\'M, com uma sensibilidade de 90 nA/\'mü\'M e limite de detecção de 8 \'mü\'M. Nas medidas cronoamperométricas, os sensores apresentaram uma ampla faixa linear (R2 = 0,994; tempo de resposta de 60 s) de até 900 \'mü\'M e limite de detecção (LD) de 37,5 x \'10 POT.-8\' M (sensibilidade de 20 nA/\'mü\'M) para o catecol. Por fim, estudou-se a fabricação de filmes LbL baseados em dendrímero poli(propileno imina) (PPID) e metaloftalocianina tetrasulfonada de níquel (NiTsPc) em sensores baseados em transistores de efeito de campo (FET). Neste caso, os filmes foram utilizados como membranas sensíveis na aplicação de sensores de pH e \'H IND.2\'O IND.2\'. Também se demonstra a importância de se utilizar estruturas dendríticas nesse tipo de filme, comparando estes filmes com aqueles contendo um polieletrólito fraco linear (PAH). Foi dada ênfase à fabricação dos filmes pela técnica LbL e sua aplicação em sensores do tipo FET de porta estendida e separada (SEGFET). Filmes LbL baseados em enzimas artificiais se mostram bastante promissores em aplicações reais por serem relativamente baratos e simples, possibilitando o uso de variados tipos de materiais. A utilização desses filmes em dispositivos baseados em estruturas SEGFET possibilita a miniaturização dos sensores bem como sua produção unindo técnicas convencionais de fabricação microeletrônica.This thesis describes the preparation, characterization and development of biosensors based on nanostructured films containing immobilized enzymes and metallophthalocyanines. The films were obtained using the Layer-by-Layer (LbL) or Langmuir-Blodgett (LB) techniques. In the first part of the thesis we describe the development of nanostructured thin films containing the enzyme tyrosinase (Tyr) and their use as biosensors for detection of antioxidants molecules (polyphenols), which find applications in the food industry, specialy red wines. The enzyme was incorporated into the mixed LB films of arachidic acid (AA) and lutetium bisphthalocyanine (LuPc2) by injection into the aqueous subphase followed by transference to ITO or Pt electrodes. The representative phenolic compound molecule to be detected was pyrogallol. Cyclic voltammetry studies shown that the biosensor response is highly reproducible with a standard deviation of ca. 2% (n = 4), dynamic range up to 400 \'mü\'M (applied potential of 0.4 V; R2: 0.993), sensitivity of 1.54 \'mü\'A/\'mü\'M.\'CM POT.2\' and detection limit (3 \'sigma\'0/m criteria) of 4.87 x \'10 POT.-2\' \'mü\'M (n = 10). The second part of this thesis focus on the development of electrochemical sensors based on LbL films of poly(allylamine hydrochloride) (PAH) and LuPc2. The purpose of the study was to change the biological material (Tyr) by LuPc2. LuPc2 was used as an artificial enzyme in the quantification of catechol and pyrogallol as representative of phenolic compounds. In voltammetric measurements, the LbL PAH/LuPc2 sensors presented good linearity (R2 = 0.992) in the range up to 500 \'mü\'M with a sensitivity of 90 nA/\'mü\'M and detection limit of 8 \'mü\'M. As revealed by chronoamperometry measurements, the sensors exhibited a wide linear range (R2 = 0.994; response time of 60 s) up to 900 M and detection limit of 37.5 × \'10 POT.-8\' \'mü\'M (sensibility of 20 nA/\'mü\'M) for catechol. Finally, we investigated the fabrication of LbL films based on poly(propylene imine) dendrimer (PPID) and nickel tetrasulfonated phthalocyanine (NiTsPc) as active elements in devices based on field effect transistors (FET). The films were used as sensitive membranes applied as pH and \'H IND.2\'O IND.2\' sensors. It was shown the importance on the LbL technique and its application in FET-based sensors such as the separated and extended gate FET (SEGFET). LBL films based on artificial enzymes exhibit great promise in real applications due to their low cost and simplicity. The use of these films in devices based on SEGFET structures allows miniaturization of the sensors and their production combining conventional microelectronics fabrication and nanotechnological tools

Study of singlet excited state absorption spectrum of lutetium bisphthalocyanine using the femtosecond Z-scan technique

In this study we investigate the singlet excited state absorption of lutetium bisphthalocyanine (LuPc2) over a wide spectral range. It was observed distinct nonlinear absorption behaviors; saturable (SA) and reverse saturable absorption (RSA). The RSA effect was observed below 640 and above 680 nm, while SA occurs around the Q-band region, located around 660 nm. To describe the main singlet-singlet transitions, we employed the rate equation model considering the simplified three-energy level diagram. Our results reveal a ratio between excited and ground state absorption smaller than 0.05 at the Q-band region, and of approximately 4 for the other regions. (C) 2012 Elsevier B.V. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)FAPESP (Fundacao de Amparo a Pesquisa do estado de Sao Paulo)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)MCINNMCINN [AGL 2009-12660/ALI

Antithrombogenic properties of bioconjugate streptokinase-polyglycerol dendrimers

Dendrimers are monodisperse, spherical and hyperbranched synthetic macromolecules with a large number of surface groups that have the potential to act as carriers for drug immobilization by covalent binding or charge transfer complexation. In this work, a bioconjugate of streptokinase and a polyglycerol dendrimer (PGLD) generation 5 was used to obtain fibrinolytic surfaces. The PGLD dendrimer was synthesized by the ring opening polymerization of deprotonated glycidol using polyglycerol as core functionality in a step-growth processes denominated divergent synthesis. The PGLD dendritic structure was confirmed by gel permeation chromatography (GPC), nuclear magnetic resonance (1H-NMR, 13C-NMR) and matrix assisted laser desorption/ionization (MALDI-TOF) techniques. The synthesized dendrimer presented low dispersion in molecular weights (Mw/Mn = 1.05) and a degree of branching of 0.82 which characterize the polymer dendritic structure. The blood compatibility of the bioconjugate PGLD-Sk was evaluated by in vitro assays such as platelet adhesion and thrombus formation. Uncoated polystyrene –microtitre plates (ELISA) was used as reference. The epifluorescence microscopy results indicate that PGLD-Sk coating showed an improved antithrombogenic character relative to the uncoated ELISA plates.Fil: Ramos Fernandes, Edson Giuliani. Universidade Federal de Itajubá; BrasilFil: de Queiroz, Alvaro Antonio Alencar. Universidade Federal de Itajubá; BrasilFil: Abraham, Gustavo Abel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: San Román, Julio. Instituto en Ciencia y Tecnología de Polímeros; Españ

Immobilization of Lutetium Bisphthalocyanine in Nanostructured Biomimetic Sensors Using the LbL Technique for Phenol Detection

Producción CientíficaThis study describes the development of amperometric sensors based on poly(allylamine hydrochloride) (PAH) and lutetium bisphthalocyanine (LuPc2) films assembled using the Layer-by-Layer (LbL) technique. The films have been used as modified electrodes for catechol quantification. Electrochemical measurements have been employed to investigate the catalytic properties of the LuPc2 immobilized in the LbL films. By chronoamperometry, the sensors present excellent sensitivity (20 nA μM−1) in a wide linear range (R2 = 0.994) up to 900 μM and limit of detection (s/n = 3) of 37.5 × 10−8 M for catechol. The sensors have good reproducibility and can be used at least for ten times. The work potential is +0.3 V vs. saturated calomel electrode (SCE). In voltammetry measurements, the calibration curve shows a good linearity (R2 = 0.992) in the range of catechol up to 500 μM with a sensitivity of 90 nA μM−1 and LD of 8 μM.2022-07-62022-07-0

Nanostructured polyaniline thin films as urea-sensing membranes in field-effect devices

We report the development of a urea biosensor based on a separative field-effect structure containing polyaniline in nanostructured form. Urea is normally produced by the nitrogen metabolism in the body, but its excess is indicative of kidney malfunction. Layer-by-layer (LbL) films of polyaniline in nanostructured form (N-PANI) and poly(vinylsulfonic acid) (PVS) were fabricated in a simple and low-cost way and used as pH-sensitive membranes. Urease was further immobilized on N-PANI by a reticulation process using glutaraldehyde (GA) as a crosslinking agent. The PVS/N-PANI-urease membrane was previously studied as a pH sensor using a junction field-effect transistor (JFET) input operational amplifier as a read-out circuit and showed a Nernstian behaviour (∼59 mV/pH) in the 6-8 pH range with a small voltage drift. The analytical curve of the biosensor showed a wide dynamic range of urea detection (0.05-10.0 mM), which covers the usual urea concentration in human blood, indicating that the proposed biosensor can be used in clinical analyses.CNPqCAPESFAPES

Impedance sensing of DNA hybridization onto nanostructured phthalocyanine-modified electrodes

DNA detection is still undergoing major innovations in pursuit of low-cost and simple approaches for decentralized applications. Label-free sensing of DNA hybridization via impedance measurements is a popular strategy to fulfil the goals of cost-efficiency and simplicity. Several materials are often reported for electrode modification to improve the sensitivity of impedance-based sensors. Herein we evaluate the electronic properties of copper phthalocyanine tetrasulfonate (CuPcTs) in Layer-by-Layer (LbL) films for impedimetric sensing of DNA hybridization using silanized Fluorine-doped Tin Oxide (FTO) electrodes. 1 to 5 bilayers were prepared by alternate immersion of the substrate in CuPcTs and poly(allylamine hydrochloride) (PAH). DNA probe immobilization was carried out electrostatically onto the last PAH layer, followed by hybridization with the target sequence leading to the formation of a partial double stranded (pds) structure onto the films. Impedance decreased after hybridization proportionally with the concentration of the target sequence at picomolar levels. Not only are these findings useful as a potential biosensing strategy, but also leave an open question about the electronic and synergistic properties of DNA interacting with different materials and surfaces. (C) 2016 Elsevier Ltd. All rights reserved.Marie Curie Actions FP7-PEOPLE-IRSESUCMCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Sao Paulo, Inst Fis Sao Carlos, Ave Trabalhador Sao Carlense 400, BR-13566970 Sao Carlos, SP, BrazilUniv Fed Sao Paulo, Inst Ciencia & Tecnol, Ave Cesare Mansueto Giulio Lattes 1201, BR-12247014 Sao Jose Dos Campos, BrazilUniv Oviedo, Fac Quim, Calle Juan Claveria 8, Oviedo 33006, SpainUniv Complutense Madrid, Fac Farm, Plaza Ramon y Cajal S-N, E-28040 Madrid, SpainInstituto de Ciência e Tecnologia, Universidade Federal de São Paulo, Avenida Cesare Mansueto Giulio Lattes 1201, 12247-014 São José dos Campos, BrazilMarie Curie Actions FP7-PEOPLE-IRSES: 612545UCM: BE43/11Web of Scienc

Magnetic, structural and surface properties of functionalized maghemite nanoparticles for copper and lead adsorption

In this study, magnetic nanocomposites were developed and used as adsorbents for lead and copper from aqueous media. Structural, surface, magnetic and textural properties of functionalized maghemite nanoparticles synthesized by alkaline co-precipitation were studied. The surfaces of the iron oxide nanoparticles (Nps) were modified with different chemical agents such as fatty and amino acids, silica (SiO2), mesoporous silica (SBA-15), hydroxyapatite, multiwall carbon nanotubes (MWCNTs) and ethylenediaminetetraacetic acid (EDTA), obtaining NPs with mean particle sizes ranging from 7 to 16 nm according to Rietveld refinement and TEM images analysis. The physicochemical surface properties of the functionalized materials were studied via zeta potential (zeta) and Fourier transform infrared (FTIR) spectroscopy. Mossbauer spectroscopy (MS) as a function of temperature and DC magnetometry were used to study the magnetic properties. The superparamagnetic relaxation was studied by MS. The resolved spectra at 20 K confirm the presence of nanomaghemite phase. Besides, the saturation magnetization varies from 12 to 62 emu g(-1). A nitrogen adsorption-desorption technique was used to determine the specific surface area and to study the porous structure. The functionalized gamma-Fe2O3 Nps exhibited a Brunauer-Emmett-Teller (BET) specific surface area ranging from 74 to 214 m(2) g(-1) and revealed remarkable uptake capacities to remove Cu(II) and Pb(II) species from aqueous solutions.National Council of Science, Technology and Technological Innovation (CONCYTEC/Cienciactiva-Peru)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)DAADMinisterio de Economia y Competitividad of Spanish GovernmentNatl Univ San Marcos, Fac Phys Sci, POB 14-0149, Lima 14, PeruTech Univ Carolo Wilhelmina Braunschweig, Inst Phys Kondensierten Mat, D-38110 Braunschweig, GermanyUniv Fed Sao Paulo, Inst Ciencia & Tecnol, Ave Cesare Mansueto Giulio Lattes 1201, BR-12247014 Sao Jose Dos Campos, SP, BrazilBrazilian Ctr Res Phys CBPF, BR-22290180 Rio De Janeiro, RJ, BrazilUniv Fed Rio Grande do Norte, Dept Fis Teor & Expt, BR-59078970 Natal, RN, BrazilUniv Rey Juan Carlos, Environm & Chem Engn Grp, C Tulipan S-N, Madrid, SpainInstituto de Ciência e Tecnologia, Universidade Federal de São Paulo, Av. Cesare Mansueto Giulio Lattes, 1201, São José dos Campos, BrazilCNPq: 305748/2015-7Ministerio de Economia y Competitividad of Spanish Government: CTM2015-69246-RWeb of Scienc