Development of a skin-like sensor for monitoring an inflammatory biomarker for wound care application

Globally, wound management poses a massive challenge with a great impact on social-economic and healthcare systems. In a post-Covid era, at-home diagnostic and monitoring devices gained a crucial role in our lives, boosting the development of novel skin patch sensors targeted for health monitoring. In this context, one of the most important requirements concerns the creation of flexible and conformable conductive platforms that can be employed as skin-like sensors. Thus, the main goal of this dissertation consists in the development of a flexible electrochemical biosensing device for the detection of an inflammation biomarker, interleukin-6 (IL-6). The 3-electrode gold pattern was standardized by e-beam evaporation on a 6 μm polyimide membrane, a transparent and biocompatible polymeric material. Subsequently, protein-printed sensors were electrochemically fabricated on the gold-modified electrodes for IL-6 detection. This biorecognition is accomplished with molecularly-imprinted polymers (MIPs) that were synthesized on the electrode surface by electropolymerization of a mixture of two monomers, pyrrole and carboxylated pyrrole. Along this process, several electropolymerization parameters were optimized like the potential range and number of cycles, as well as the pH conditions of the medium and the removal of the imprinted protein, to create the cavities responsible for the rebinding event. Electrochemical sensing features were then investigated to demonstrate the imprinting effect and the optimized biosensor exhibited a linear electrochemical response in the 0.5 ng/mL to 500 ng/mL concentration range. Moreover, chemical, and morphological characterizations, such as XPS, SEM and FTIR confirmed the surface modifications on the gold surface. The final biosensing device demonstrated great potential in terms of sensitivity, stability, and reproducibility, making it a simpler and more cost-effective portable solution for the remote monitoring of chronic wounds. Finally, the incorporation of the sensing component directly on biocompatible flexible polymers enables new monitoring and treatment tools that can be more accurate, less invasive, and more comfortable for the patient.Globalmente, a monitorização de feridas representa um enorme desafio com grande impacto nos sistemas socio-económicos e de saúde. Numa era pós-Covid, os dispositivos de diagnóstico e monitorização a partir de casa adquiriram um papel crucial nas nossas vidas, impulsionando o desenvolvimento de novos sensores flexíveis para a pele para monitorização da saúde. Nesse contexto, um dos requisitos mais importantes diz respeito à criação de plataformas condutoras flexíveis e conformáveis que possam ser utilizadas como sensores para pele. Assim, o principal objetivo desta dissertação consiste no desenvolvimento de um dispositivo biossensor eletroquímico flexível para a deteção de um biomarcador de inflamação, interleucina-6 (IL-6). O padrão de 3 elétrodos de ouro foi padronizado por evaporação por feixe eletrónico numa membrana de poliimida com 6 μm de espessura, um material polimérico transparente e biocompatível. Posteriormente, os biossensores foram fabricados eletroquimicamente nos elétrodos modificados com ouro para deteção de IL-6. Este bioreconhecimento é realizado através de polímeros de impressão molecular (MIPs) que foram sintetizados na superfície do elétrodo por eletropolimerização de uma mistura de dois monómeros, pirrol e pirrol carboxilado. Ao longo deste processo, vários parâmetros de eletropolimerização foram otimizados tais como a gama de potencial aplicado e o número de ciclos, as condições de pH do meio e a remoção da proteína impressa, a fim de criar as cavidades responsáveis pelo evento de religação. As características de deteção eletroquímica foram então investigadas para demonstrar o efeito de impressão e o biossensor otimizado exibiu uma resposta eletroquímica linear na gama de concentrações de 0.5 ng/mL a 500 ng/mL. Além disso, caracterizações químicas e morfológicas, tais como XPS, SEM e FTIR confirmaram as modificações químicas na superfície do eléctrodo. O dispositivo biossensor final demonstrou potencial em termos de sensibilidade, estabilidade e reprodutibilidade, tornando-se uma solução portátil, simples e económica para a monitorização remota de feridas crónicas. Por fim, a incorporação do componente sensor diretamente em polímeros flexíveis biocompatíveis permite novas ferramentas de monitorização e tratamento que podem ser mais precisas, menos invasivas e mais confortáveis para o paciente

A Fully 3D-printed Integrated Electrochemical Sensor System

This thesis investigates the design, fabrication, and characterization of a 3D printed electrochemical sensor as well as compact potentiostat circuits on Printed Circuit Board (PCB) for portable electrochemical sensing applications. Conductive 3D printing technologies are investigated as well as the advances in sensors and electronics applications. An optimized Directly Ink Writing (DIW) technique is adapted to a novel 3D-PCB fabrication platform using silver nanoparticle ink for electronics applications. An electrochemical device called potentiostat is designed based on an open source system. Its prototype is 3D printed on FR4 substrate. Using the same 3D platform, a lactate sensor which is composed of a 3-electrode is printed on the flexible substrate. Together, the 3D printed system demonstrates the electrochemistry test including cyclic voltammetry (CV) and amperometry. Results of this research demonstrate that 3D-PCB technology can significantly accelerate the fabrication process of conventional electronic, and merge its capability into electrochemical applications

Electropolymerization

In recent years, great focus has been placed upon polymer thin films. These polymer thin films are important in many technological applications, ranging from coatings and adhesives to organic electronic devices, including sensors and detectors. Electrochemical polymerization is preferable, especially if the polymeric product is intended for use as polymer thin films, because electrogeneration allows fine control over the film thickness, an important parameter for fabrication of devices. Moreover, it was demonstrated that it is possible to modify the material properties by parameter control of the electrodeposition process. Electrochemistry is an excellent tool, not only for synthesis, but also for characterization and application of various types of materials. This book provides a timely overview of a current state of knowledge regarding the use of electropolymerization for new materials preparation, including conducting polymers and various possibilities of applications

Carbon-Based Nanomaterials for (Bio)Sensors Development

Carbon-based nanomaterials have been increasingly used in sensors and biosensors design due to their advantageous intrinsic properties, which include, but are not limited to, high electrical and thermal conductivity, chemical stability, optical properties, large specific surface, biocompatibility, and easy functionalization. The most commonly applied carbonaceous nanomaterials are carbon nanotubes (single- or multi-walled nanotubes) and graphene, but promising data have been also reported for (bio)sensors based on carbon quantum dots and nanocomposites, among others. The incorporation of carbon-based nanomaterials, independent of the detection scheme and developed platform type (optical, chemical, and biological, etc.), has a major beneficial effect on the (bio)sensor sensitivity, specificity, and overall performance. As a consequence, carbon-based nanomaterials have been promoting a revolution in the field of (bio)sensors with the development of increasingly sensitive devices. This Special Issue presents original research data and review articles that focus on (experimental or theoretical) advances, challenges, and outlooks concerning the preparation, characterization, and application of carbon-based nanomaterials for (bio)sensor development

Heavy and precious metal toxicity evaluation using a horseradish peroxidase immobilised biosensor

>Magister Scientiae - MScEnvironmental pollution is always the hottest topic in public conversation and one of the most concerned aspects of human health. The thin film sputtered microelectrode devices have been developed to improve the quality of human health, by offering better monitoring capabilities. This thesis is divided into three parts and the studies were performed on chemical sensor technology currently available and under development using modified methods. In the first part of this thesis: (i) the studies are related to synthesis, characterization and polymerisation of polyaniline (PANI) and polyaniline-co-poly(2,2´-dithiodianline) (PANI-co-PDTDA). Polyaniline (PANI) and the copolymer of aniline with dithiodianiline, an aniline derivative containing S-S-links were of interest in polymer synthesis. Electrochemical synthesis was carried out in 1 M HCl and different concentrations of H2SO4 (1, 2.5, and 5 M) solutions for PANI and PANI-co-PDTDA respectively. The PANI and PANI-co-PDTDA were grown electrochemically on the surface of a glassy carbon electrode (GCE) by repetitive cyclic voltammetric scanning. Cyclic voltammetry (CV) was used to evaluate the differences between the electrochemical characteristics associated with growth of the copolymer and homopolymer, polyaniline (PANI). The surface concentration of PANI was estimated to be 2.64 × 10-1 mol.cm-2 while the film thickness was estimated to be 7.09 × 10-10cm and 1.49 × 10-9cm for scan rate and aquare root scan rate. In contrast, PANI-co-PDTDA concentrations (1, 2, 5 and 5 M H2SO4 solutions) gained a surface concentration (G) falling in the range 6.1 x 10-2 - 7.9 x 102 mol.cm-2 and a film thickness in the range 8.16 x 10 -9- 2.05x10-8cm. The second section of this thesis focused on the development of two sensors, Pt/PANI/HRP and Pt/PANI-co-PDTDA/HRP biosensors. The biosensor described in this chapter focus on the use of horseradish peroxidise (HRP) with hydrogen peroxide as substrate, was constructed with the aim of further investigation of inhibition by heavy metals (Cd2+, Pb2+ and Hg2+). To achieve this, the enzyme HRP as the catalytic bio-element, was immobilised on the surface of a platinum electrode with PANI as a mediator. Immobilisation of HRP in conducting polymer matrices of PANI and PANI-co-PDTDA were achieved by electrochemical polymerisation. The use of amperometric detection allowed for the coupling of the biosensor with a portable potentiostat system (PalmSens). Differential pulse voltammetry (DPV) as technique was used as a detection method for inhibition determination. Selection of suitable pH values for biosensor performance was evaluated and the system showed optimal performance at pH 6.8 and 7.2 for Pt/PANI/HRP and Pt/PANIco- PDTDA/HRP biosensors, respectively. The biosensors developed in this work showed detection limits (LODs) of 0.32 mM and 0.0483 mM for PANI/HRP and PANI-co- PDTDA/HRP, respectively. For the Pt/PANI/HRP biosensor, the apparent Michaelis-Menten constant (Km app) value and maximum current (Imax) were evaluated from Lineweaver-Burk plots at various H2O2 concentrations. The values were found to be 0.6 mM and 1.7 μA for the Pt/PANI/HRP biosensor, while for the Pt/PANI-co-PDTDA/HRP biosensor the results were 0.7 mM and 0.27 μA, respectively. The third section investigated the adsorptive cathodic differential pulse stripping voltammetric (AdDPSV) determination of platinum group metals (PGMs), using an ex situ bismuth coated screen printed carbon electrode (SPCE/Bi) as the working electrode and ammonium buffer solution (pH = 9.2) as the supporting electrolyte. The cathodic stripping differential pulse method was used for investigating the electrochemical behaviour and the quantitative analysis of platinum group metals (Pt, Pd and Rh) at the SPCE/Bi surface in the presence of dimethylgloxime (DMG) as a complexing agent. In order to determine the metals at improved detection limits ensuring repeatability and sensitivity, a complete optimization study of voltammetric parameters was performed. The proposed method was successfully applied to the determination of the real samples (sediments & water) collected in the platinum mining area in the North-West and Limpopo Provinces, South Africa. The results were compared with those obtained by the glassy carbon bismuth film (GC/BiF) voltammetric and ICP-AES spectrometry techniques. Well-shaped voltammograms with clear peak potentials were obtained in the analysis of the real samples, offering excellent perspectives on the use of the constructed modified electrodes. The calibration curves for all PGMs investigated were linear with the limit of detection (LOD) at approximately 0.008, 0.006, and 0.005 μg.L-1 for Pd, Pt and Rh, respectively