Orientador: Lauro Tatsuo Kubota / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-04T04:12:52Z (GMT). No. of bitstreams: 1 Martins_LucileneDornellesMello_D.pdf: 8841041 bytes, checksum: f4618b120bf384d76c695743eb6ce4cc (MD5) Previous issue date: 2005 / Doutorado / Quimica Analitica / Doutor em Quimica

Designing a biosensor capable of continuously monitoring blood glucose concentration in people with diabetes has been a major challenge for over three decades. In this work we attempt to develop a novel microspike based minimally invasive biosensor for this purpose. Also, as a part of an ongoing study, we attempt to improve the current design of coil-type implantable biosensors. Microspikes, which are able to painlessly penetrate the skin layer, were fabricated using lithographic techniques and sputtered with gold to serve as an electrode. The biosensor design is based on thiomalic acid self-assembled monolayer (SAM) on which glucose oxidase was immobilised by a simple coupling technique together with a tetrathiafulvalene mediator entrapped in an epoxy-polyurethane permselective membrane. Functional testing revealed that such modified sensors are capable of detecting glucose concentration within the clinically relevant range. This was followed by studying the microspike based biosensors incorporated into the microfluidics platform mimicking the sensor behaviour in interstitial fluid. Data from these experiments revealed that the sensor response is mainly dependent on enzyme kinetics rather than membrane permeability to glucose. In contrast, an attempt to address the reproducibility issues of coil-type biosensors is presented. The hypothesis for this study was that a crosslinked hydrogel would have a sufficiently uniform porosity and hydrophilicity to address the variability in sensor sensitivity. The hydrogel was prepared by crosslinking di-hydroxyethyl methacrylate, hydroxyethyl methacrylate and N-vinyl pyrrolidone with 2.5 mol% ethylene glycol dimethacrylate using the water soluble initiators – ammonium persulphate and sodium metabisulfite under a nitrogen atmosphere. The hydrogel was applied to the sensor by dip coating during polymerisation. Electrochemical measurements revealed that the response characteristics of sensors coated with this membrane are highly consistent. Scanning Electrochemical Microscopy (SECM) was used to spatially resolve glucose diffusion through the membrane by measuring the consequent hydrogen peroxide release and compared with an epoxy- polyurethane membrane.

Surface enhanced Raman spectroscopy (SERS) has great potential for design of next generation point-of-care (POC) diagnostic devices. However, its practical application in medical diagnosis is limited due to high cost of SERS substrates. The goal for this thesis was to develop affordable SERS substrates, and demonstrate their efficacy in the detection and assay of a Raman probe and diabetes biomarkers, using 514nm and 1064nm Raman spectrometers. Rapid and less energy intensive methods were optimised for manufacturing three categories of SERS substrates: 1) chemically roughened silver (Ag) metal, 2) Ag and gold (Au) nanoparticles (NPs) prepared using microemulsions, and 3) Ag and Au NPs’ coated insoluble electrospun membranes. Immersion of Ag metal for 30 seconds in ammonia (NH4OH), followed by 10 seconds in nitric acid (HNO3) produced optimum roughened Ag metal SERS substrates. For synthesis of gold (Au) and Ag NPs, microemulsion compositions were varied, and the use of sodium borohydrate (NaBH4) produced the desired larger sizes and anisotropic shapes of the NPs. Nanostructured planar SERS structures based on insoluble electrospun membranes, were prepared by covalently binding Au or Ag NPs, on electrospun poly acrylic acid-ethylene glycol (PAA-EG) fibres. Ag metal SERS substrates provided the best SERS enhancement for the Raman probe molecule, 4-methylbenzenethiol (MBT), with a detection limit of 1aM, using 514nm Raman spectrometer. The Ag metal SERS substrates were then used to demonstrate proof-of-concept for the use of SERS for assay of diabetes biomarkers. The higher laser intensity of 106nm Raman caused burning of the dry NPs’ incorporated SERS substrates; but the thermally conductivity of solid Ag in Ag metal SERS substrate allowed SERS detection of 1nM MBT. To conclude, chemically roughened Ag metal SERS substrates proved cost effective and robust for quantitative SERS detection of MBT and diabetes biomarkers both with 514nm and 1064nm Raman spectrometers.

Tuberculosis has re-emerged as a global health problem due to co-infection with HIV and the emergence of drug resistant strains of Mycobacterium tuberculosis. There is a need for a reliable and fast serodiagnostic assay to reduce the time required for test results from weeks to hours, in order to better control the spread of the disease. Previous studies have shown that TB patients contain antibodies against M. tuberculosis mycolic acids. In standard immunoassays such as ELISA, an unacceptable number of false positive and negative test results were obtained. This study aimed at assessing the potential of detecting anti-mycolic acids antibodies in TB patient sera on a biosensor as surrogate marker for TB infection. Mycolic acid liposomes were immobilized reproducibly on a non-derivatized biosensor cuvette and blocked with saponin. A high dilution of serum in PBS/ AE was used to calibrate the signal of the two cells, followed by binding of patient sera inhibited with either mycolic acid, cholesterol or placebo phosphatidylcholine liposomes at a lesser dilution. The inhibition was done to confirm the specificity of the binding response. There was no inhibition of binding when a sputum negative control serum (HIV-TB-) was pre-incubated with either cholesterol or mycolic acids on the biosensor coated with mycolic acid liposomes. The antibodies that are specific to mycolic acid were demonstrated in all TB positive patients on mycolic acids coated cuvette cell surfaces after pre-incubation of serum with mycolic acids. The patient sera that were false positive and false negative on ELISA tested negative and positive respectively on the biosensor. Only sera from two patients, both HIV positive, tested false positive on both ELISA and biosensor. The biosensor was able to detect anti-mycolic acids antibodies of even low affinity. In ELISA, these antibodies were washed away. No inhibition of antibody binding on cholesterol-coated cuvettes was found after pre-incubation of serum with mycolic acids or cholesterol liposomes. The cholesterol surface became unstable during pre-incubation of serum with mycolic acids. Mycolic acid appeared to be a stronger antigen than cholesterol. The anti-mycolic acids antibodies were specific and sensitive for diagnosis of TB on the biosensor. More sera should be analyzed on the biosensor to make a statistically accountable statement on whether the improved sensitivity and specificity is adequate for a simple, rapid, sensitive and accurate biosensor-based serodiagnostic assay. / Dissertation (MSc(Biochemistry))--University of Pretoria, 2006. / Biochemistry / unrestricted

Low temperature-processed, porous sol-gel glasses represent a new class of materials for the immobilisation of biomolecules. If used to entrap biological recognition elements, these transparent and chemically inert glasses offer a new approach in the development of optical biosensors.

Ph.D. (Computer Science) / The introduction of new portable sensors that monitor physiological systems in the human body has allowed quality of life and medical diagnostic applications to be taken directly to the user, without the constraints of physical space or inconvenience. The potential of these sensors in the domain of authentication and identi cation is becoming more feasible each day and current research in these biometric systems show a great deal of promise. Novel biometric systems are being introduced that use biological signals (also known as biosignals) in the human body captured by these sensors (such as brain waves or heart rate) as the core unique attribute. The study builds on the proliferation of these sensors and proposes an interoperable model called CoBI, which allows individual or multi-factor authentication and identi cation to take place. The model provides a platform for any viable biosignal that can be used for the purposes of identi cation and authentication, by providing pluggable sensor and signal processing components. These components can then convert biosignals into a common format, a feature vector consisting of estimated autoregressive (AR) coe cients. Once they are in a common format they can then be merged together to form a consolidated feature vector using feature fusion. This consolidated feature vector can then be persisted during enrolment or passed further for matching using classi cation techniques, such as K-Nearest Neighbour. The results, from the comprehensive benchmark performed (called BAMBI) on an implemented version of the model (called CaNViS), have shown that biological signals that contain cardiac and neurological components (ie. from an electrocardiogram (ECG) and electroencephalogram (EEG), respectively) can be captured, processed, consolidated and classi ed using the CoBI model successfully. By utilising the correct AR model order during feature estimation for the cardiac and neurological components, along with the appropriate classi er for matching, the biometric system yields nominal results for authentication and identi cation in access control environments.

Orientador: David Mendez Soares / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T18:01:06Z (GMT). No. of bitstreams: 1 Casagrande_PaulaSimoes_M.pdf: 7069712 bytes, checksum: cba42a97bc9e94ebc92b3ea0cc517e17 (MD5) Previous issue date: 2016 / Resumo: Neste trabalho foram desenvolvidos e caracterizados transistores de efeito de campo sensíveis a íons (Ion Sensitive Field Effect Transistor ¿ ISFET) com dois óxidos de porta distintos, óxido de silício (SiO2) e óxido de titânio sobre óxido de silício (TiO2/SiO2). Estes sensores foram fabricados utilizando tecnologia de micro fabricação de silício. A caracterização elétrica destes dispositivos foi realizada para MOSFETs de caracterização analisando-se as curvas de diodo, curvas de capacitância, a tensão de limiar e a transcondutância dos dispositivos fabricados. Para as amostras de SiO2 os valores típicos obtidos foram 6,4±0,1 pF para a capacitância máxima, 1,3±0,1 V para a tensão de limiar e 3,5±0,1 µS para a transcondutância, e para as amostras de TiO2/SiO2 foram 64±1 pF, -2,0±0,1 V e 10,5±0,1 µS, respectivamente. Os ISFETs foram testados em meios líquidos utilizando-se soluções tampão. Os ISFETs de SiO2 apresentaram pouca sensibilidade à variação de pH e os ISFETs de TiO2/SiO2 apresentaram baixa sensibilidade para pH baixo e maior sensibilidade para pH alto. Foi desenvolvido um sistema para medidas eletroquímicas utilizando os sensores em solução / Abstract: In this work were developed and characterized Ion Sensitive Field Effect Transistors (ISFET), with two different gate oxides: silicon oxide (SiO2) and titanium oxide on silicon dioxide (TiO2/SiO2). These sensors were manufactured using silicon micro fabrication technology. The electrical characterization of these devices has been done on MOSFETs, analyzing the diode curves, the capacitance curves, the threshold voltage and the transconductance of the manufactured devices. For the SiO2 sample typical values were 6.4 ± 0.1 pF for maximum capacitance, 1.3 ± 0.1 V for threshold voltage and 3.5 ± 0.1 uS for maximum transconductance and for the TiO2/SiO2 samples were 64 ± 1 pF, -2.0 ± 0.1 V and 10.5 ± 0.1 ?S, respectively. The ISFETs were tested in liquid using buffer solutions. The ISFETs with SiO2 showed small sensitivity to pH variation, and the ones of with TiO2/SiO2 showed low sensitivity to low pH and higher sensitivity to high pH. A system was developed for electrochemical measurements using the sensors in solution / Mestrado / Física / Mestra em Física / 132989/2014-0 / CNPQ

Quick and early detection of abnormalities in the body's metabolism is of paramount importance to monitor, control, and prevent the associated diseases and pathologies. Biosensors technology is rapidly advancing, from the first electronic biosensor reported by Clark and Lyons in 1962 for blood glucose monitoring to today’s devices that can detect multiple metabolites in bodily fluids continuously and simultaneously within seconds. This rapid growth in point-of-care devices promises for the development of novel devices with different form factors and the ability to detect a wide range of biomarkers. These advancements mainly stem from the development of electronic materials that have properties better aligning with the biotic interface compared to the traditional metal electrodes. A promising class of electronic materials for biosensors is conjugated polymers. Conjugated polymers are carbon-based, organic semiconducting materials made of long chains comprising conjugated repeat units. The fundamental property that makes these materials so attractive is, however, not their electronic conductivity, but their ionic conductivity. As living organisms use ionic fluxes to relay signals, materials that can conduct ionic currents are believed to facilitate the communication between the electronics and living systems. This communication happens at various levels: organs, complex tissues, cells, cell membrane, proteins, and small biomolecules. Besides, the inherently soft nature of these materials facilitates mechanical conformity with soft biological systems. The field of organic bioelectronics has experienced tremendous growth over the past two decades, thanks to the design of new conjugated polymers customized for the biotic interface. While hole conducting (p-type) polymers have been widely investigated, electron conducting (n-type) counterparts are relatively new. This dissertation aims to explore the capabilities of n-type conjugated polymers for bioelectronics applications. Chapter 1 overviews the key properties of conjugated polymers and the resulting electronic devices that leverage these properties for specific applications in bioelectronics. Chapter 2 presents microfabricated metabolite (lactate and glucose) sensors based on an n-type polymer in combination with enzymes, and how this communication can enable energy production from bodily fluids. Finally, Chapter 3 reports the development of engineering and design strategies to enhance the performances of n-type polymers in bioelectronics.

Low-noise operational amplifiers are an important tool in the life sciences. Biosensor measurements typically rely on low-noise transimpedance amplifiers to record biological signals. Two different techniques were used to leverage the advantages of low-noise circuitry for bioelectronics. A CMOS-integrated system for measuring redox-active substrates using electrochemical read-out at very low noise levels is presented. The system incorporates 112 amplifier channels capable of current sensing with noise levels below 1 fArms in a 3.5-Hz bandwidth. The amplifier is externally connected to a gold microelectrode with a radius of 15 µm. The amplifier enables measurement of redox-couples such as potassium ferrocyanide/ferricyanide with concentrations down to 10 nM at current levels of only 300 fA. The electrochemical noise that sets the limits of detection is also measured and analyzed based on redox mass transfer equation and electrochemical impedance spectroscopy. Secondly, CMOS-integrated low noise junction field-effect transistors (JFETs) were developed in a standard 0.18-µm CMOS process. These JFETs reduce input referred flicker noise power by more than a factor of 10 when compared with equally sized n-channel MOS devices by eliminating oxide interfaces in contact with the channel. We show that this improvement in device performance translates into a factor-of-10 reduction in the input-referred noise of integrated CMOS operational amplifiers when JFET devices are used at the input.

Miniaturization, integration and intelligence are the developing trends for sensor,especially for biosensors. The development of microelectronics technology is a powerful engine to full this objective. It is well known that the microelectronic fabrication process in proven technology for fabrication of integrated circuits. Advances in the field of micro-electronics and micro-mechanical devices combined with medical science have led to the development of numerous analytical devices in monitoring of a wide range of analytes. The unique properties of nanoscale materials offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bio-electronic devices exhibiting novel functions. Biosensor development has the potential to meet the need for rapid, sensitive, and specic detection of pathogenic bacteria from natural sources. This work focuses on development of one such electrochemical biosensor platform and discusses dierent aspects related to the design of biosensor and biodetection systems. A new transducer for bio sensor applications based on 3-dimensional, comb structured interdigitated electrode arrays was chosen mainly for two reasons. Firstly, this geometry allows the monitoring of both resistivity and dielectric constant of solution, thus making interdigitated electrodes more versatile tools than other kind of transducers. Second, they present short electric eld penetration depths, which make them more sensitive to changes occurring close to their surface (20 - 100 nm above the surface). This fact enables the monitoring of local changes in the vicinity of interest. Binding of analyte molecules to the chemically modied transducer surface induces important changes in the conductivity between the electrodes. Interdigitated electrodes have been employed to detect the presence of Anti-Transglutaminase (TG) antibodies, that are established biomarkers for Celiac disease which is due to gluten allergy. The biosensor was optimized for specific and sensitive detection of this biomarker. The sensor showed a sensitivity down to picomolar(pM) concentration of the biomarker. Gold nanoparticles were further used for signal enhancement so as to bring the sensor performance closer to Enzyme linked immunosorbant assay (ELISA).