Bacterial infections are and likely always will be a serious and costly complication to treatment in a healthcare environment. However consistent rises in the number of both healthcare associated and antibiotic resistant infections over the last of decades has the potential to turn a serious problem into a catastrophe. Control of infections in hospital wards has improved over the last five years but data from the European Centre for Disease Prevention and Control suggests a stale mate. While the numerical rise in drug resistant organisms has slowed, the severity of drug resistance appears to be on the increase with the prolific emergence of multiple drug resistant isolates. On the front lines of the threat that these organisms represent are some of the most susceptible. In hospitals those who are already sick are more vulnerable, those with co-morbidities, those with surgical or other wounds, the very old and the very young. Children especially show high susceptibility as they are often incapable of communicating clinical complications in the way an adult might. This coupled with higher commonality of specific aetiologies in children such as scalds, open wounds that are prone to infection without proper treatment, creates population in need. Antibiotics are often thought to be part of the problem in drug resistance, indeed to an extent they are. However their real downfall may be improper use. In order to improve treatment outcomes and simultaneously decrease antimicrobial resistance a combination of rapid diagnosis and prophylaxis can be utilised to decrease selection of resistance. As such, this study focuses on the development of a novel vesicle based sensor system for the detection of bacterial infections in burn wounds. Additionally an organometallic antimicrobial system has been developed with the potential for surface attachment. Work with the vesicle based biosensor demonstrates high sensitivity to both Staphylococcus aureus and Pseudomonas aeruginosa. The toxins involved in activation of the sensor have been determined in both cases and an in-depth study into the activity of the staphylococcal agents of lysis (Phenol Soluble Modulins and delta haemolysin), shows a high degree of plasticity and tunability in the sensors function. Work with the zinc based antimicrobial reveals a highly complex system which demonstrates possible functions as a not only an antimicrobial but as a sensor system in its own right.

This thesis describes a detailed study of advanced fibre optic sensors and their applications for label-free biochemical detection. The major contributions presented in this thesis are summarised below. A self-assembly based in-situ layer-by-layer (i-LbL) or multilayer deposition technique has been developed to deposit the 2D material nanosheets on cylindrical fibre devices. This deposition technique is based on the chemical bonding associated with the physical adsorption, securing high-quality 2D materials coating on specific fibre cylindrical surface with strong adhesion as well as a prospective thickness control. Then a " Photonic-nano-bio configuration", which is bioprobes immobilised 2D-(nano)material deposited fibre grating, was built. 2D material overlay provides a remarkable analytical platform for bio-affinity binding interface due to its exceptional optical and biochemical properties. EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) and NHS (NHydroxysuccinimide) were used to immobilise bioprobes. This kind of configuration is considered to have many advantages such as: enhanced RI sensitivity, enrich immobilisation sites, improved binding efficiency, selective detection. Followed by this configuration, several label-free biosensors were developed. For example, graphene oxide coated dual-peak long period grating (GO-dLPG) based immunosensor has been implemented for ultrasensitive detection of antibody/antigen interaction. The GO-LPG based biosensor has been developed for label-free haemoglobin detection. Apart from biosensors, the black phosphorus (BP) integrated tilted fibre grating (TFG) has been proposed, for the first time, as BP-fibre optic chemical sensor for heavy metal (Pb2+ ions) detection, demonstrating ultrahigh sensitivity, lower limit of detection and wider concentration range. Ultrafast laser micromachining technology has been employed to fabricate long period grating (LPG) and microstructures on optical fibre. The ultrafast laser micromachined polymer optical fibre Bragg grating (POFBG) has been developed for humidity sensing, showing the significant improvement with the reduced response time.

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Agradecemos a compreensão. on 2017-03-22T14:32:46Z (GMT) / Submitted by JOAO PEDRO CORREA DE CAMARGO null (joaoquimica1991@hotmail.com) on 2017-03-22T15:13:54Z No. of bitstreams: 1 Autoarquivamento da dissertação corrigido .pdf: 2162415 bytes, checksum: 64ada6268776f57730601f9cd0ffc35b (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-24T16:41:36Z (GMT) No. of bitstreams: 1 camargo_jpc_me_bot.pdf: 2162415 bytes, checksum: 64ada6268776f57730601f9cd0ffc35b (MD5) / Made available in DSpace on 2017-03-24T16:41:36Z (GMT). No. of bitstreams: 1 camargo_jpc_me_bot.pdf: 2162415 bytes, checksum: 64ada6268776f57730601f9cd0ffc35b (MD5) Previous issue date: 2017-02-09 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Um novo biossensor foi desenvolvido baseado na simples eletrocodeposição do óxido de grafeno reduzido (rGO), polipirrol (PPy) e da enzima acetilcolinesterase (AChE) na superfície do eletrodo de platina (Pt). No intervalo de potencial -0,2 a +0,5 V vs. Ag/AgCl/KCl (3,0 mol L-1), utilizando voltametria de pulso diferencial (DPV), observou-se um processo em +0,1 V e este corresponde a dimerização dos produtos de oxidação eletroquímica da tiolcolina, formando ditio-bis-colina. O biossensor desenvolvido foi avaliado utilizando DPV na análise do pesticida carbaril, o qual inibe a ação da enzima AChE. Os melhores resultados obtidos foram com as seguintes condições otimizadas: 75 mV amplitude de pulso, incremento de potencial de 4 mV, e uma solução tampão fosfato (PBS) 0,2 mol L-1 pH 6,0. Usando tais parâmetros observou-se uma resposta linear para o carbaril no intervalo de 0,1 a 0,5 mol L-1, com um limite de detecção de 11,6 nmolL-1 (2,3 µg/kg), que é um limite adequado para determinar carbaril nas culturas em que este pesticida é aplicado considerando o limite máximo de resíduo permitido pelas legislações brasileiras. O biossensor proposto, Pt/rGO/PPy/AChE, foi aplicado com sucesso na determinação de carbaril em amostras de tomate e repolho. / A new biosensor was developed by a simple electrocodeposition of reduced graphene oxide (rGO), polypyrrole (PPy) and the enzyme acetylcholinesterase (AChE) on surface of platinum (Pt) electrode. In potential range of -0.2 to +0.5 V vs. Ag/AgCl/KCl (3.0 mol L-1), using differential pulse voltammetry (DPV), it was observed a process in + 0.1 V and this corresponds to the dimerization of electrochemical oxidation products of thiocholine, resulting in ditio-bis-choline. The biosensor developed was evaluated using DPV in the analysis of carbaryl, which inhibits the AChE enzyme action. The best results achieved were with the followings optimized conditions: 75 mV pulse amplitude, step potential of 4 mV, and a phosphate buffer solution (PBS) 0.2 mol L-1 and pH 6.0. Using these parameters was observed a linear response to carbaryl in a range of 0.1 to 0.5 µmol L-1, with a detection limit of 11.6 nmol L-1 (2.3 µg/kg), which is an appropriate limit for determination of carbaryl in the cultures which these pesticide is applied, considering the maximum reside limit allowed by Brazilian legislation. The biosensor proposed, Pt/rGO/PPy/AChE, was applied successfully in the determination of carbaryl in samples of cabbage and tomato. / FAPESP: 2015/02136-2

Esta tese descreve a esfoliação e modificação do grafeno oxidado (GO) na obtenção de grafeno em sua forma reduzida (RGO) para aplicações biomédicas, que envolve sensoriamento e biossensoriamento, além de aplicação em fototerapia. Nas aplicações em sensores, inicialmente o RGO juntamente com o surfactante aniônico Dihexadecilfosfato (DHP), foi utilizado na fabricação de filmes por drop casting em eletrodo de carbono vítreo (CGE), na detecção do hormônio Estradiol. O eletrodo modificado (RGO-DHP/CGE) foi caracterizado por voltametria cíclica e impedância de espectroscopia eletroquímica. Os resultados mostraram uma corrente de pico de oxidação irreversível em 0,6 V. Sob as condições experimentais ideais, usando a voltametria linear, o limite de detecção para este hormônio foi de 7,7 × 10-8 mol L-1. Foram fabricados também dispositivos de efeito de campo (FET) de RGO via porta líquida em eletrodos interdigitados, para a detecção de Cistatina-C, um marcador de doença renal crônica. Os filmes foram fabricados utilizando a técnica de automontagem de interação eletrostática, nos quais, como polieletrólito de carga positiva foi utilizado o RGO modificado via ligação covalente de APTES, e como polieletrólito de carga negativa, o RGO dopado com nitrogênio, através da redução via micro-ondas. Estes dispositivos apresentaram uma sensibilidade de (1,94 ± 0,29) ΔIDS(%)ngmL-1. O LD foi de 0,39 ngmL-1 e a região linear entre 5 ngmL-1 100 ngmL-1, quando utilizados em urina sintética. Avaliamos também o uso de RGO em sistemas de fototerapia, utilizando GO reduzido com NH4OH na presença de L-Glutamina (RGO-Glu), onde observamos um aumento de temperatura localizado quando o material é irradiado por um laser (808 nm). Este sistema apresentou uma boa estabilidade e baixa agregação em dispersão aquosa e em meio de cultura, devido à formação de uma corona proteica. O RGO-Glu mostrou-se mais eficiente para o aquecimento que o RGO sem a modificação, na absorção do laser em 808 nm, com valores de eficiência de conversão de energia de 63% e 50% respectivamente. Estudos utilizando célula HeLa mostram que a internalização do RGO-Glu foi mais eficiente do que o RGO sem a modificação. Estes estudos mostram a versatilidade do grafeno quimicamente esfoliado em aplicações biomédicas quando convenientemente modificado, que pode ser utilizado em diagnóstico e em terapia. / This thesis describes the exfoliation and modification of graphene oxide (GO) to obtain reduced graphene oxide (RGO), for biomedical applications, namely: (bio)sensing for diagnostics and as active material in phototherapy. For (bio)sensing applications, RGO was used in combination with the anionic surfactant Dihexadecylphosphate (DHP) in the fabrication of drop-cast thin films onto carbon glass electrode (CGE), to be used in the detection of the hormone Estradiol. The modified electrode (RGO-DHP/CGE) was characterized by cyclic voltammetry and electrochemical spectroscopy impedance (EIS). The results showed an irreversible oxidation peak current at 0.6 V. Under ideal experimental conditions, and using linear voltammetry, the detection limit obtained for this sensor was 7.7 × 10-8 mol L-1. In the second part of the study, RGO was used in the fabrication of field effect transistors (FETs) via liquid gate, and the devices were applied in the detection of Cystatin-C, a biomarker for chronic renal disease. The films were made using the electrostatic layer-by-layer technique, in which APTES-modified RGO was used as positive polyelectrolyte, whereas nitrogen-doped RGO was used as the negative species. These devices exhibited a sensitivity of (1,94 ± 0,29) ΔIDS(%)ngmL-1, whereas LD was 0,39 ng.mL-1 and the linear region of detection was between 5 ng.mL-1 100 ngmL-1 when used in synthetic urine. The studies on the use of RGO in phototherapy were carried out using NH4OH -reduced GO in the presence of L-Glutamine (RGO-Glu) for subsequent cell internalization and irradiation under an 808 nm lase line to promote hiperthermia. This system showed good stability and low aggregation in aqueous dispersions and culture medium, due to the formation of a protein corona. RGO-Glu was more efficient than the RGO without the modification in the absorption of the laser at 808 nm, resulting in an efficiency of heat generation (energy conversion efficiency) of 63% and 50% respectively. Cytotoxicity studies using HeLa cell lines revealed that the internalization of RGO-Glu was more efficient than RGO without modification. These studies show the versatility of chemically exfoliated graphene oxides for biomedical applications, including diagnosis and therapy.

Multi electrode array (MEA) systems have evolved from custom-made experimental tools, exploited for neural research, into commercially available systems that are used throughout non-invasive electrophysiological study. MEA systems are used in conjunction with cells and tissues from a number of differing organisms (e.g. mice, monkeys, chickens, plants). The development of MEA systems has been incremental over the past 30 years due to constantly changing specific bioscientific requirements in research. As the application of MEA systems continues to diversify contemporary commercial systems are requiring increased levels of sophistication and greater throughput capabilities.

Graphene-family nanomaterials (GFNs) have attracted a great deal of attention both in academia and in industry for a range of applications relevant for homeland security. In this thesis, an array of graphene-based hybrid materials and aerogels are synthesized for use as novel thermo-electrochemical energy harvesters and for ascorbic acid biosensing devices. The graphene-family nanomaterials include graphene oxide-GO, thermally reduced GO-rGOth, nitrogenated functionalized graphene-NFG, graphene aerogel-GA, nitrogen-doped graphene aerogel-NGA, multi-walled carbon nanotube aerogel-MWCNT, single-walled carbon nanotube aerogel-SWCNT, graphene and nanotube combined ‘hybrid’ aerogels-Gr:(SW/MW)CNT of various ratios, along with multilayered nanostructured architectures such as gold (AuNP) and silver nanoparticles (AgNP) decorated NFG coated with a thin layer of polyaniline (PANi). Precursor aerogel materials were also analyzed to demonstrate the effect of mesoporous architectures and the interplay of various components in augmenting physical-chemical properties. These precursors were combined through multiple deposition schemes including electrodeposition, hydrothermal synthesis, and freeze drying techniques. This project was developed in an effort to enhance electrochemical properties through modification of the morphology, surface and structural properties, making them more suitable for thermal energy harvesting and bio-sensing applications. Hydrothermal synthesis created chemical bridged interfaces, interconnectedness, and improved electrical conductivity besides increasing the surface area of mesoporous aerogels created by freeze-drying. This causes an increase in the number density of electrochemically active sites. The surface morphology, lattice vibrations, and electrochemical activity of the materials were investigated using electron microscopy, micro-Raman Spectroscopy, and electrochemical microscopy techniques [namely cyclic voltammetry (CV), alternating current electrochemical impedance spectroscopy (acEIS), amperometric techniques, and scanning electrochemical microscopy (SECM)]. For thermoelectric and thermoelectrochemical power measurements, a custom-designed set up was made for creating a temperature gradient across two legs of a thermocell and experiments were performed in various device configurations (a) symmetric and asymmetric, (b) single thermocells, and (c) multiple (“in-tandem”) thermocells. Interestingly, we observed changes in conducting behavior from Ohmic to semiconducting and polarity shifts from positive to negative or vice versa on introduction of the redox electrolyte solution. The parametric correlations (thermopower and resistivity or conductivity) are established and the results are discussed in terms of the polarity switching behavior observed for some of the aerogels combinations.

The concepts of electroneutrality coupling and electron-hopping, which are useful for the incorporation of functional components and transportation of electrons, were applied in this project. Discrete layered structures were fabricated by sequential electropolymerization to modulate the performances of formate biosensors. Different types of layers, with or without enzyme, were successfully grown on the electrode surface. The presence of the enzyme (formate dehydrogenase), co-factor (B-nicotinamide adenine dinucleotide) and an electron mediator in the polypyrrole film was verified by scanning electron microscopy, chronopotentiometry, cyclic voltammetry and amperometric measurements. Monolayer, bilayer and trilayer formate biosensors were successfully fabricated for different analytical purposes. The utilisation of the biosensing membrane for the reliable batch and FIA determination of formate based on a amperometric mode of detection are explored. Electron mediators such as ferrocyanide, Prussian Blue, ferrocene and ferrocene carboxylic acid were incorporated into the polypyrrole film to lower the required applied potential for amperometric sensing and to maintain the conductivity and stability of the polypyrrole backbone. The application of artificial neural networks (ANN) to overcome the problem of reusability and reproducibilty in a nonlinear and complicated dynamic system is also considered. The resulting system was trained with a new neural network based software package, Turbo Neuron, for prediction of the concentration of formate, based on the entire collected data, which contain the history of the detection experiments. The proposed integrated ANN conducting polymer biosensor enables the determination of formate concentration, both online and in real time / Doctor of Philosophy (PhD)

This thesis outlines a study of the physical changes that hybridisation imposes on single-stranded DNA (ssDNA) immobilised by one end to a substrate, and of how such physical changes can be exploited to detect specific sequences of DNA in a target solution. The system studied was composed of a mixed monolayer of 20mer ssDNA with C6 alkanethiolate modifications on their 3??? ends and short-chain hydroxyterminated alkanethiolates, on a gold substrate. It was prepared using the self-assembly properties of alkanethiols on gold. Atomic force microscopy images showed that the end-immobilised ssDNA is flexible enough to lie over the diluent hydroxy-terminated self-assembled monolayer (SAM). Hybridisation was shown to cause the DNA to become more rigid and stand up off the substrate due to an increase in persistence length. Such physical changes of the DNA upon hybridisation were significant enough to be exploited in the development of a DNA recognition interface. The recognition interface was designed with the view of keeping it both simple to make and simple to use, and was coupled with electrochemical transduction. A label-free recognition interface was developed that relied on the oxidation of the sulfur head group of the alkanethiolate SAM to detect hybridisation (firstly air oxidation and then electrochemical oxidation). It produced a positive signal upon hybridisation with complementary target DNA. Improvements in the reliability and robustness of the recognition interface were made using a labelled approach. The labelled version employed electroactive molecules as labels on the 5??? ends of the probe DNA strands. Two labels were investigated ??? anthraquinone and ferrocene. The flexibility of the ssDNA ensured that the redox labels were able to directly access the underlying gold electrode. Hybridisation was expected to remove the labels from the electrode due to an increase in the DNA???s persistence length, and thus perturb the electrochemical signal. The use of ferrocene as a label provided a ???proof-of-concept??? for the system. The labelled recognition interface provides a foundation for the future development of a simple, reliable, and selective DNA hybridisation biosensor.

Heat shock protein 70 (HSP70) is an important health related biomarker, being implicated as an early stage cancer marker and as an indicator of cardiac health. It also has important implications in wildlife environmental monitoring, as its levels can be affected by food deprivation, elevated temperatures, and pollution. Therefore, the use of HSP70 as a biomarker is highly desirable, yet the current methods of quantifying HSP70 are time consuming, expensive, and require dedicated labs. In order to facilitate widespread use of the HSP70 biomarker, a quantification tool that can be used at the point-of-care is needed. This implies the development of a simple and inexpensive HSP70 biosensing technique that is highly sensitive and selective. Therefore, in this work a label-free HSP70 biosensor has been designed based on the optical properties of gold nanoparticles (NPs). Gold NPs exhibit a large absorbance peak in the visible spectrum due to localized surface plasmon resonance (LSPR). The peak position is dependent on the local refractive index, which can be employed as a biosensor by selectively capturing the target analyte to the NP surface. To design an LSPR HSP70 sensor, optical and fluidic simulations were developed to determine optimal NP geometries and microchannel dimensions. The results showed optimal response when using 100nmx5nm gold nanotriangles inside of a 100μmx100μm microchannel. Simulations of the sensor performance showed HSP70 detection from 0.92-4000ng/ml with a resolution of 1.1ng/ml, all of which satisfied the design requirements. An LSPR sensor was experimentally tested at the benchtop scale to prove the concept. Gold NPs were fabricated by electron beam lithography and enclosed in a polymer flow cell. For initial testing of the LSPR sensor, the NPs were functionalized with biotin for selective capture of streptavidin. Streptavidin was detected in real time over the range 55-500,000ng/ml. The use of bovine serum albumin (BSA) was shown to be necessary to block non-specific binding sites to ensure a streptavidin-specific response. The LSPR sensor was then demonstrated to detect salmon HSP70 at 4600ng/ml using its synthetic antibody. Overall, these results demonstrate that LSPR can be used to realize an HSP70 biosensor suitable for point-of-care applications.

The thickness shear mode acoustic wave (TSM) sensor, operated in a flow-through format, has been widely used in bioanalytical research. My research is mainly focused on the study of surface-attached biomolecules and cells using the TSM sensor, including lesions in DNA, conformational change of calmodulin, as well as the properties and attachment of rat aortic smooth muscle cells. Aldehydic apurinic or apyrimidinic sites (AP sites) that lack a nucleobase moiety are one of the most common forms of toxic lesions in DNA. In this work, synthesized oligodeoxyribonucleotides containing one, two, or three abasic sites were hybridized to complementary sequences immobilized on the gold electrode of the TSM device by affinity binding. The influence of AP sites on local base stacking energy and geometry caused a dramatic destabilization of the DNA duplex structure, which was detected by the TSM sensor. The signals detected by TSM correlated well with the thermostability of DNA duplexes in solution. The results indicate that both the number of sites and their localization in the double-stranded structure influence the stability of a 19 b.p. duplex. TSM was also used to detect the binding of ions or peptides to surface-attached calmodulin. The interaction between calmodulin and ions induced an increase in resonant frequency and a decrease in motional resistance. In addition, these signal changes were reversible upon washing with buffer. The response was interpreted as a decrease in surface coupling induced by exposure of hydrophobic domains on the protein, and an increase in the length of calmodulin by approximately 3 Å. In addition, the interaction of the protein with peptide together with calcium ions was detected successfully, despite the relatively low molecular mass of the 2-kDa peptide. In addition, the attachment of smooth muscle cells to various surfaces has been monitored by TSM. These surfaces include laminin, fibronectin and bare gold. The results of these experiments in terms of changes of frequency (fs) and resistance (Rm) were analyzed. The responses of the surface-bound cells to the introduction of various ions, depolarisation events and damage subsequent to exposure to hydrogen peroxide were also observed. Morphological changes in the cells, as confirmed by atomic force microscopy and scanning electron microscopy, are correlated with results from the TSM sensor.