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Implant placement is an important repair method in dentistry and orthopedics. Increasing efforts have focused on optimizing the biocompatibility and osseointegration properties of titanium (Ti) and Ti-based alloys. In this work, Ti-based alloys were modified by the layer-by-layer (LbL) technique, which is a simple and versatile method for surface modification. The morphology and chemical structure of LbL films of poly(sodium 4-styrenesulfonate) (PSS) and Ti dioxide (TiO more...

Biomedical applications with emphasis on the design of smart materials, specifically magnetic nanoparticles (MNPs) are considered to have technological benefits because they can be manipulated using magnetic fields. Magnetic NPs have been widely used in hyperthermia, target drug delivery system, imaging, and extraction of biomolecules, postulating them also as an important tool in cancer treatment. Morphological structures of magnetic materials have drawn tremendous attention from diverse scientific fields due to their unique surface chemistry, nontoxicity, biocompatibility, and particularly their inducible magnetic moment. This review features recent research accomplishments made in the biomedical field using magnetic nanoparticles. The first part gives a comprehensive overview of magnetic nanoparticles in the treatment of chronic diseases and drug targeting. The second part includes the role of magnetic nanoparticles in electrochemical, optical-based immunoassays. The review also outlines the current challenges and future research perspectives for fostering advanced and high-performance magnetic nanoparticles in technological applications. more...

Immunoassays are important for the diagnosis of many diseases. Efficient methods for the immobilization of the biorecognition elements is a relevant subject because the antibody loading is directly related to the detection range and sensitivity. Here different self-assembled films were explored to take advantage of polar oxygenated groups from graphene oxide (GO) structure. Surface plasmon resonance (SPR) sensors were modified with different GO self-assembled films and compared to the well-established thiol-functionalization with 11-MUA (11- mercaptoundecanoic acid). Self-assembled cysteamine/GO functionalized sensor (Cys-GOSA) provided the highest protein loading (7.66 × 10−12 mol cm−2 against 1.29 × 10−11 mol cm−2 for the traditional thiol-functionalization). The Langmuir-Blodgett (LB) films of GO were composed of aggregates and empty spaces, which hindered the antibody anchoring (around 6.38 × 10−12 to 3.45 × 10−12 mol cm−2). The SPR response of the Cys-GOSA-modified sensor to the 4.0 ng mL−1 PSA was 125% higher than the thiol-functionalized sensor at the same concentration. This result indicates a simple and promising surface modification strategy for many important applications, not limited to SPR sensors, but for all immunoreaction-based assays as enzyme-linked immunosorbent assay (ELISA), electrochemical (e.g. amperometric and impedimetric) and quartz crystal microbalance (QCM) based sensors. more...

The conjugation of nanoparticles with antibodies has been successfully applied in sandwich immunoassays for detecting cancer biomarkers. However, two antibodies are necessary to perform such experiment, being one of them functionalized with a signal label for optical or electrochemical assay. This approach is time and cost consuming compared to direct label-free immunoassays. In this study, we propose the synthesis of gold nanoparticles conjugated to anti-PSA antibody to produce a label-free impedimetric immunosensors based on nanostructured Layer-by-Layer (LbL) films. Prostate-specific antigen (PSA) detection was performed by electrochemical impedance spectroscopy demonstrating a detection mechanism governed by Langmuir-Freundlich adsorption model. This strategy provided a significant sensitivity using 10-fold less antibody than conventional immunosensors, i.e. decreasing costs using a simple approach, with a limit of detection of 0.17 ng mL−1 and an analytical range of 0.1–20 ng mL−1 indicating that our sensor is potentially useful for clinical applications. more...

In recent years microfluidics and lab-on-a-chip havecome to the forefront in diagnostics and detection [...]

Monitoring health conditions with low-cost, portable devices is a target for diseases such as diabetes, which is now performed by detecting the glucose level in blood samples. Since commercial biosensors suffer with limited enzyme stability and shelf-life problems, novel materials have been exploited, including metal oxides and sulfide nanostructures. These materials are suitable for detection with electrochemical methods owing to their high surface area-to-volume ratio, selectivity, sensitivity, and fast response properties. In this chapter, we discuss some of these nanostructures to detect glucose through nonenzymatic reactions, which are advantageous to increase robustness and shelf-life of biosensors. Furthermore, the work on metal oxides and sulfide-based biosensors is being extended with the design of hierarchical nanostructures to enable high sensitivity, rapid response, and detection of multicomponent elements following the electronic tongue concept. The challenges and prospects for glucose biosensing are also highlighted. more...

Lab-on-a-Disc (LoaD) biosensors are increasingly a promising solution for many biosensing applications. In the search for a perfect match between point-of-care (PoC) microfluidic devices and biosensors, the LoaD platform has the potential to be reliable, sensitive, low-cost, and easy-to-use. The present global pandemic draws attention to the importance of rapid sample-to-answer PoC devices for minimising manual intervention and sample manipulation, thus increasing the safety of the health professional while minimising the chances of sample contamination. A biosensor is defined by its ability to measure an analyte by converting a biological binding event to tangible analytical data. With evolving manufacturing processes for both LoaDs and biosensors, it is becoming more feasible to embed biosensors within the platform and/or to pair the microfluidic cartridges with low-cost detection systems. This review considers the basics of the centrifugal microfluidics and describes recent developments in common biosensing methods and novel technologies for fluidic control and automation. Finally, an overview of current devices on the market is provided. This review will guide scientists who want to initiate research in LoaD PoC devices as well as providing valuable reference material to researchers active in the field. more...

The wide use of pesticides in agriculture makes necessary the development of cost-effective, easy, and rapid methods aiming for environmental and health protection. We propose the fabrication and investigation of layer-by-layer (LbL) films composed of reduced graphene oxide stabilized in polyelectrolytes in the presence and absence of gold nanoparticles (AuNPs) toward methyl parathion (MP) detection. In addition to the film assembly and sensing application, we performed a systematic investigation of the influence of MP distribution on the limit of detection and linear range of the sensor. Indium tin oxide (ITO) electrodes modified with the LbL films were applied by differential pulse voltammetry achieving an LOD and a linear range of 0.226 ppm and 0.25–40 ppm in the absence of AuNPs, while in the their presence, a wider linear range was achieved (0.5–60 ppm, with LOD of 0.770 ppm). Real sample analysis indicated potential application in water, ground, and vegetables, with recovery varying from 92% to 113%. more...

Made available in DSpace on 2018-12-11T17:36:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The production of large-area interfaces and the use of scalable methods to build up designed nanostructures generating advanced functional properties are of high interest for many materials science applications. Nevertheless, large-area coverage remains a major problem even for pristine graphene, and here we present a hybrid, composite graphene-like material soluble in water that can be exploited in many areas such as energy storage, electrodes fabrication, selective membranes and biosensing. Graphene oxide (GO) was produced by the traditional Hummers’ method being further reduced in the presence of poly(styrene sulfonate) sodium salt (PSS), thus creating stable reduced graphene oxide (rGO) nanoplatelets wrapped by PSS (GPSS). Molecular dynamics simulations were carried out to further clarify the interactions between PSS molecules and rGO nanoplatelets, with calculations supported by Fourier transform infrared spectroscopy analysis. The intermolecular forces between rGO nanoplatelets and PSS lead to the formation of a hybrid material (GPSS) stabilized by van der Waals forces, allowing the fabrication of high-quality layer-by-layer (LbL) films with poly(allylamine hydrochloride) (PAH). Raman and electrical characterizations corroborated the successful modifications in the electronic structures from GO to GPSS after the chemical treatment, resulting in (PAH/GPSS) LbL films four orders of magnitude more conductive than (PAH/GO). POSMAT – Programa de Pós-Graduação em Ciência e Tecnologia de Materiais UNESP – Univ Estadual Paulista Universidade Federal de São Carlos – DFQM Faculdade de Engenharia de Sorocaba – FACENS Applied Physics Department State University of Campinas UNESP – Univ Estadual Paulista Centro Universitário Central Paulista – UNICEP Instituto de Física de São Carlos – USP POSMAT – Programa de Pós-Graduação em Ciência e Tecnologia de Materiais UNESP – Univ Estadual Paulista UNESP – Univ Estadual Paulista FAPESP: 2010/13033-6 FAPESP: 2012/01484-9 FAPESP: 2015/14703-9 FAPESP: 2016/00023-9 FAPESP: 2016/12340-9 more...

Distinct architectures of layer-by-layer (LbL) films made of carbon nanotubes and gold nanoparticles were investigated to serve as the matrix to immobilize cholesterol oxidase, with which cholesterol could be detected using amperometry. The gold nanoparticles were synthesized by metal reduction stabilized in poly(allylamine hydrochloride) (PAH) providing a stable AuNPs-PAH suspension, while multi-walled carbon nanotubes (CNTs) were functionalized with carboxylic groups to obtain an aqueous suspension. The LbL films were deposited on ITO, with a cushion film of PAH and poly(vinyl sulfonic acid) (PVS). Owing to the synergy between CNTs and AuNPs, the electrode ITO/(PAH/PVS)₂ (AuNPs-PAH/CNTs)10 was selected for immobilization of cholesterol oxidase (ChOx). This sensor could detect cholesterol with a limit of detection of 14.8 μmol L-1 and sensitivity of 36.47 (μA cm-2)·(mmol L-1)-1. It was also able to determine cholesterol in egg yolk with a recovery of 97.7%. more...

Made available in DSpace on 2021-06-25T17:10:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) INEO Carbofuran (CBF) is a pesticide currently prohibited in many countries. It can cause serious damages in the nervous system and has been associated with cancer. However, CBF residues are still found in food samples around the world. Here, we develop an electrochemical non-enzymatic sensor for rapid and low-cost detection of CBF. Commercial indium fin oxide (ITO) electrodes were modified with a two-step Layer-by-Layer (LbL) approach: i) an LbL film of poly(diallyldimethyl ammonium) (PDDA) and graphene oxide (GO), which is further electrochemically reduced to produce (PDDA/ERGO)-modified ITO electrodes; and ii) an LbL film of magnetite nanoparticles (MNP) and poly(styrene sulfonate) (PSS) to form the ITO/(PDDA/ERGO)(5)/(MNP/PSS)(5), with 5 representing the number of bilayers. The growth mechanism and morphology of the modified electrode were characterized by combining microscopy and optical spectroscopy. The ITO/(PDD/ERGO)(5)/(MNP/PSS)(5) was applied in the electrochemical detection of CBF by differential pulse voltammetry (DPV) in standard solutions, reaching a sensitivity of 0.2543 (mu A cm(-2)) (mu mol L-1) and LOD of 0.407 mu mol L-1, and then in real samples of tap water and soil. Univ Fed Sao Carlos, CCTS, Rod Joao Leme Santos,KM 110, BR-18052780 Sorocaba, SP, Brazil Univ Estadual Paulista, Presidente Prudente, SP, Brazil Univ Estadual Paulista, Presidente Prudente, SP, Brazil FAPESP: 2013/14262-7 FAPESP: 2014/15093-7 FAPESP: 2016/19387-0 FAPESP: 2016/09634-0 FAPESP: 2017/19630-5 more...

Made available in DSpace on 2019-10-06T16:17:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Antigen-antibody interaction is crucial in autoimmune disease pathogenesis, as multiple sclerosis and neuromyelitis optica. Given that, autoantibodies are essential biomolecules, of which the myelin oligodendrocyte glycoprotein (MOG) can figure as a target. Here we combined Molecular Dynamics (MD), Steered Molecular Dynamics (SMD), and Atomic Force Microscope (AFM) to detail MOG recognition by its specific antibody. The complex model consisted of the MOG external domain interacting with an experimental anti-MOG antibody from the Protein Data Bank (1PKQ). Computational data demonstrated thirteen MOG residues with a robust contribution to the antigen-antibody interaction. Comprising five of the thirteen anchor residues (ASP 102 , HIS 103 , SER 104 , TYR 105 , and GLN 106 ), the well-known MOG 92–106 peptide in complex with the anti-MOG was analysed by AFM and SMD. These analyses evidenced similar force values of 780 pN and 765 pN for computational and experimental MOG 92–106 and anti-MOG detachment, respectively. MOG 92–106 was responsible for 75% of the total force measured between MOG external domain and anti-MOG, holding the interaction with the antibody. The antigen-antibody binding was confirmed by Surface Plasmon Resonance (SPR) measurements. Combined approaches presented here can conveniently be adjusted to detail novel molecules in diseases research. This can optimize pre-clinical steps, guiding experiments, reducing costs, and animal model usage. Nanoneurobiophysics Research Group Department of Physics Chemistry and Mathematics Federal University of São Carlos Institute of Tropical Medicine of São Paulo University of São Paulo Department of Neurology Psychology and Psychiatry UNESP - São Paulo State University Science and Technology Centre for Sustainability Federal University of São Carlos Rheabiotech Laboratory Research and Development Institute of Chemistry Federal University of Uberlândia Department of Chemistry Federal University of São Carlos Department of Neurology Psychology and Psychiatry UNESP - São Paulo State University FAPESP: 2012/50839-4 FAPESP: 2013/09746-5 FAPESP: 2014/12082-4 FAPESP: 2014/15093-7 FAPESP: 2014/21530-0 FAPESP: 2014/26369-3 FAPESP: 2015/05283-6 FAPESP: 2015/06847-0 FAPESP: 2016/19387-0 CNPq: 305069/2016-0 CNPq: 459768/2014-0 more...

As a direct, label-free method, Surface Plasmon Resonance (SPR) detection significantly reduces the needs for liquid handling and reagent storage compared to common enzyme-linked immunosorbent assays (ELISAs), thus enabling comprehensive multiplexing of bioassays on microfluidic sample-to-answer systems. This paper describes a highly integrated centrifugal Lab-on-a-Disc (LoaD) platform for automating the full process chain extending between plasma extraction and subsequent aliquoting to five parallelized reaction channels for quantitative SPR detection by an inexpensive smartphone camera. The entire, multi-step / multi-reagent operation completes within less than 1 h. While the emphasis of this work is on the fluidic automation and parallelization by previously introduced, very robust event-triggered valving and buoyancy-driven centripetal pumping schemes, we successfully implement an immunoglobulin G (IgG) assay; by specific functionalization of the detection surfaces, the same disc layout can readily be customised for immunoassays panels from whole blood. more...

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm(-2))/(mmol L(-1)) and a detection limit of 0.33 mmol L(-1). more...

We present for the first time an integrated wirelessly powered Arduino processor and Bluetooth interface that are co-rotated with the cartridge to allow large-scale process integration on a centrifugal microfluidic platform. This highly modular, electronically controlled “Lab-on-a-Disc” system (eLoaD) can independently actuate up to 128 normally-closed valves by an array of microheaters during rotation for comprehensive, highly parallelized sample-to-answer automation. Additionally, we implement real-time optical (colour intensity) measurement for closed-loop control of liquid handling, sample preparation and detection. more...

In this paper we present a wirelessly powered array of 128 centrifugo-pneumatic valves that can be thermally actuated on demand during spinning. The valves can either be triggered by a predefined protocol, wireless signal transmission via Bluetooth, or in response to a sensor monitoring a parameter like the temperature, or homogeneity of the dispersion. Upon activation of a resistive heater, a low-melting membrane (Parafilm™) is removed to vent an entrapped gas pocket, thus letting the incoming liquid wet an intermediate dissolvable film and thereby open the valve. The proposed system allows up to 12 heaters to be activated in parallel, with a response time below 3 s, potentially resulting in 128 actuated valves in under 30 s. We demonstrate, with three examples of common and standard procedures, how the proposed technology could become a powerful tool for implementing diagnostic assays on Lab-on-a-Disc. First, we implement wireless actuation of 64 valves during rotation in a freely programmable sequence, or upon user input in real time. Then, we show a closed-loop centrifugal flow control sequence for which the state of mixing of reagents, evaluated from stroboscopically recorded images, triggers the opening of the valves. In our last experiment, valving and closed-loop control are used to facilitate centrifugal processing of whole blood. more...

Immunosensors made with nanostructured films are promising for detecting cancer biomarkers, even at early stages of the disease, but this requires control of film architecture to preserve the biological activity of immobilized antibodies. In this study, we used electrochemical impedance spectroscopy (EIS) to detect Prostate Specific Antigen (PSA) with immunosensors produced with layer-by-layer (LbL) films containing anti-PSA antibodies in two distinct film architectures. The antibodies were either adsorbed from solutions in which they were free, or from solutions where they were incorporated into liposomes of dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation into DPPG liposomes was confirmed with surface plasmon resonance experiments, while the importance of electrostatic interactions on the electrical response was highlighted using the Finite Difference Time-Domain Method (FDTD). The sensitivity of both architectures was sufficient to detect the threshold value to diagnose prostate cancer (ca. 4 ng mL−1). In contrast to expectation, the sensor with the antibodies incorporated into DPPG liposomes had lower sensitivity, though the range of concentrations amenable to detection increased, according to the fitting of the EIS data using the Langmuir-Freundlich adsorption model. The performance of the two film architectures was compared qualitatively by plotting the data with a multidimensional projection technique, which constitutes a generic approach for optimizing immunosensors and other types of sensors. more...

The sustained use of cosmetics, hygiene products and medicines containing methylparaben (MeP) can be related to cases of cancer in women and children, which is why it is important to develop simple ways to monitor this compound. Gold electrodes were modified with Layer-by-Layer (LbL) films of magnetite nanoparticles (MNP) and polypyrrole (Ppy) for electrochemical determination of MeP. To investigate the synergistic effect between the MNP and Ppy, three different LbL architectures were tested: multilayers of Ppy with an conventional polycation poly(allylamine hydrochloride) – Au/(PAH/Ppy)3, MNP with a conventional polyanion poly(vinyl sulfonic acid) – Au/(MNP/PVS)3 and the hybrid composite film Au/(MNP/Ppy)3. The highest oxidation current and lowest oxidation potential were achieved by the Au/(MNP/Ppy)3 electrode in a range up to 131.4 μmol L−1 with a limit of detection of 9.95 × 10−8 mol L−1. The performance of the electrochemical sensor was statistically investigated by the Miller-Miller method demonstrating accuracy comparable to an analytical method (capillary electrophoresis). MeP was determined in urine, breast milk and cosmetic with recovery values varying from 84.0% to 113.3%. more...

Alternative energy sources are on a global demand, with fuel cells as promising devices from mobile to stationary applications. Nafion ® is at the heart of many of these appliances, being mostly used due to its high proton conduction and good chemical stability at ambient temperature in proton exchange membranes (PEM). Therefore, methanol permeation throughout Nafion ® films reduces drastically the performance of direct methanol fuel cells (DMFC). We present here the deposition of layer-by-layer (LbL) nanostructured thin films of poly(allylamine hydrochloride) (PAH) and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) onto commercial Nafion ® 212 membranes. It was observed a good adherence of the LbL films onto Nafion ® 212, with UV–vis results displaying a linear characteristic growth, indicative that the same amount of material was deposited at each deposition step during the layer-by-layer assembly. In addition, the LbL films also act as a good barrier to avoid methanol crossover, with an observed reduction in the methanol permeation from 5.5 × 10 −6 cm 2 s −1 to 3.2 × 10 −6 cm 2 s −1 , respectively to pristine Nafion ® 212 and a 5-bilayer PAH/PEDOT:PSS LbL film deposited on Nafion ® 212. The measured power density in a DMFC set-up was not significantly changed (∼12 mW cm −2 ) due to the LbL films, since the PAH/PEDOT:PSS nanostructure is impeding water and ion transport, consequently affecting the proton conduction throughout the membrane. more...

Made available in DSpace on 2014-12-03T13:11:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-07-01Bitstream added on 2014-12-03T13:22:30Z : No. of bitstreams: 1 WOS000322171700003.pdf: 2384407 bytes, checksum: dfa25986b34c0796f1380f916148eb78 (MD5) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) rede nBioNet (Brazil) We report on optimized architectures containing layer-by-layer (LbL) films of natural rubber latex (NRL), carboxymethyl-chitosan (CMC) and magnetite (Fe3O4) nanoparticles (MNPs) deposited on flexible substrates, which could be easily bent by an external magnetic field. The mechanical response depended on the number of deposited layers and was explained semi-quantitatively with a fully atomistic model, where the LbL film was represented as superposing layers of hexagonal graphene-like atomic arrangements deposited on a stiffer substrate. The bending with no direct current or voltage being applied to a supramolecular structure containing biocompatible and antimicrobial materials represents a proof-of-principle experiment that is promising for tissue engineering applications in biomedicine. Fed Univ ABC, Ctr Nat & Human Sci, BR-09210170 Santo Andre, SP, Brazil Univ Estadual Campinas, UNICAMP, Gleb Wataghin Inst Phys, Dept Appl Phys, BR-13083970 Campinas, SP, Brazil Univ Sao Paulo, Sao Carlos Inst Phys, BR-13560970 Sao Carlos, SP, Brazil Sao Paulo State Univ, UNESP, Fac Sci & Technol, BR-19060900 Presidente Prudente, SP, Brazil UNICEP, Paulista Univ Ctr, BR-13563470 Sao Carlos, SP, Brazil Sao Paulo State Univ, UNESP, Dept Phys, IGCE, BR-13506900 Rio Claro, SP, Brazil Sao Paulo State Univ, UNESP, Fac Sci & Technol, BR-19060900 Presidente Prudente, SP, Brazil Sao Paulo State Univ, UNESP, Dept Phys, IGCE, BR-13506900 Rio Claro, SP, Brazil more...

Antibody immobilization on polymeric substrates is a key manufacturing step for microfluidic devices that implement sample-to-answer automation of immunoassays. In this work, a simple and versatile method to bio-functionalize poly(methylmethacrylate) (PMMA), a common material of such "Lab-on-a-Chip" systems, is proposed; using the Layer-by-Layer (LbL) technique, we assemble nanostructured thin films of poly(ethylene imine) (PEI) and graphene oxide (GO). The wettability of PMMA surfaces was significantly augmented by the surface treatment with (PEI/GO)5 film, with an 81% reduction of the contact angle, while the surface roughness increased by 600%, thus clearly enhancing wettability and antibody binding capacity. When applied to enzyme-linked immunosorbent assays (ELISAs), the limit of detection of PMMA surface was notably improved from 340pgmL-1 on commercial grade polystyrene (PS) and 230pgmL-1 on plain PMMA surfaces to 130pgmL-1 on (PEI/GO)5 treated PMMA. Furthermore, the accelerated antibody adsorption kinetics on the LbL films of GO allowed to substantially shorten incubation times, e.g. for anti-rat IgG adsorption from 2h down to 15min on conventional and treated surfaces, respectively. more...

Surface plasmon resonance (SPR) biosensing is based on the detection of small changes in the refractive index on a gold surface modified with molecular recognition materials, thus being mostly limited to detecting large molecules. In this paper, we report on a SPR biosensing platform suitable to detect small molecules by making use of the mediator-type enzyme microperoxidase-11 (MP11) in layer-by-layer films. By depositing a top layer of glucose oxidase or uricase, we were able to detect glucose or uric acid with limits of detection of 3.4 and 0.27 μmol l-1, respectively. Measurable SPR signals could be achieved because of the changes in polarizability of MP11, as it is oxidized upon interaction with the analyte. Confirmation of this hypothesis was obtained with finite difference time domain simulations, which also allowed us to discard the possible effects from film roughness changes observed in atomic force microscopy images. The main advantage of this mediator-type enzyme approach is in the simplicity of the experimental method that does not require an external potential, unlike similar approaches for SPR biosensing of small molecules. The detection limits reported here were achieved without optimizing the film architecture, and therefore the performance can in principle be further enhanced, while the proposed SPR platform may be extended to any system where hydrogen peroxide is generated in enzymatic reactions. more...

Made available in DSpace on 2018-12-11T17:29:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Empresa Brasileira de Pesquisa Agropecuária Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Reliable gas sensors operating at room temperature are in demand for monitoring the environment for hazardous pollutants, such as ammonia (NH3) gas that may become toxic to humans and animals above a threshold concentration. In this paper we report on the combination of three materials, namely polyaniline (PANI), graphene oxide (GO) and zinc oxide (ZnO), to produce hybrid layer-by-layer (LbL) films used for sensing NH3 with impedance spectroscopy measurements. The deposition of tetralayered PANI/GO/PANI/ZnO LbL films was confirmed with UV–vis. absorption and Raman spectroscopies, while atomic force microscopy (AFM) served to investigate film morphology. Exposure of these LbL films to NH3 caused film roughness to vary, in an effect that depended on the number of tetralayers. Because of synergy in the materials properties, the films with 3 tetralayers were found to be the most adequate for detecting NH3 in the range from 25 ppm to 500 ppm with a response time of 30 s. These figures of merit are adequate for monitoring working environments regarding gas exposure, and highlight the usefulness of the control of film architecture provided by the LbL technique. National Laboratory for Nanotechnology in Agribusiness (LNNA) Embrapa Instrumentation Center for Exact Sciences and Technology Department of Chemistry Federal University of São Carlos (UFSCar) São Carlos Institute of Physics (IFSC) University of São Paulo (USP), P.O. Box 369 CCTS Federal University of São Carlos (UFSCar) Institute of Physics Gleb Wataghin Unicamp Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP) CNPq: 141894/2013-0 FAPESP: 2012/15543-7 FAPESP: 2012/23880-3 FAPESP: 2013/14262-7 FAPESP: 2014/16789-5 CNPq: 502391/2014-6 more...

Made available in DSpace on 2018-12-11T16:42:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-11-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) We report an electrochemical glucose biosensor made with layer-by-layer (LbL) films of functionalized reduced graphene oxide (rGO) and glucose oxidase (GOx). The LbL assembly using positively and negatively charged rGO multilayers represents a simple approach to develop enzymatic biosensors. The electron transport properties of graphene were combined with the specificity provided by the enzyme. rGO was obtained and functionalized using chemical methods, being positively charged with poly(diallyldimethylammonium chloride) to form GPDDA, and negatively charged with poly(styrene sulfonate) to form GPSS. Stable aqueous dispersions of GPDDA and GPSS are easily obtained, enabling the growth of LbL films on various solid supports. The use of graphene in the immobilization of GOx promoted Direct Electron Transfer, which was evaluated by Cyclic Voltammetry. Amperometric measurements indicated a detection limit of 13.4 μmol·L‐1 and sensitivity of 2.47 μA·cm−2·mmol−1·L for glucose with the (GPDDA/GPSS)1/(GPDDA/GOx)2 architecture, whose thickness was 19.80 ± 0.28 nm, as determined by Surface Plasmon Resonance (SPR). The sensor may be useful for clinical analysis since glucose could be detected even in the presence of typical interfering agents and in real samples of a lactose-free milk and an electrolyte solution to prevent dehydration. São Paulo State University - UNESP, Sorocaba Federal University of São Carlos UFSCar Campus Sorocaba Federal University of São Paulo Unifesp Campus São José dos Campos University of Campinas - Unicamp, Campinas São Paulo State University - UNESP, Sorocaba FAPESP: 2014/15093-7 FAPESP: 2014/17519-1 more...

This minireview describes the main developments of electronic tongues (e-tongues) and taste sensors in recent years, with a summary of the principles of detection and materials used in the sensing units. E-tongues are sensor arrays capable of distinguishing very similar liquids employing the concept of global selectivity, where the difference in the electrical response of different materials serves as a fingerprint for the analysed sample. They have been widely used for the analysis of wines, fruit juices, coffee, milk and beverages, in addition to the detection of trace amounts of impurities or pollutants in waters. Among the various principles of detection, electrochemical measurements and impedance spectroscopy are the most prominent. With regard to the materials for the sensing units, in most cases use is made of ultrathin films produced in a layer-by-layer fashion to yield higher sensitivity with the advantage of control of the film molecular architecture. The concept of e-tongues has been extended to biosensing by using sensing units capable of molecular recognition, as in films with immobilized antigens or enzymes with specific recognition for clinical diagnosis. Because the identification of samples is basically a classification task, there has been a trend to use artificial intelligence and information visualization methods to enhance the performance of e-tongues. more...

Surface plasmon resonance (SPR) is an optical technique that exploits the generation of electromagnetic waves (plasmons). The propagation of the surface plasmons at the metal–dielectric interface is very sensitive to the variations in the refractive index of the surface allowing the monitoring of ultrathin films grown very close to the metal interface. Sensor development and studies about kinetics of interaction between biomolecules are the most investigated applications in the field. The main advantage over other currently used techniques is the possibility of label-free and real-time analysis with high sensitivity and specificity. In this chapter, we discuss briefly the theory of surface plasmon generation; the SPR-based sensor fundamentals and the main applications of the technique are also remarked on. more...