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Desenvolvimento de um bioelétrodo enzimático à base de papel para aplicações analíticas e energéticas
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Resumo(s)
A criação de Biocélulas de Combustível (BFCs) emerge como uma solução promissora para a
produção de energia em microescala dependendo de catalisadores biológicos e mais
sustentáveis quando comparados por exemplo com as tradicionais células de combustível que
usam catalisadores caros e com custos ambientais associados. As BFCs são uma forma
interessante de gerar microenergia, podendo ser vantajosamente utilizadas em biossensores
autoalimentados energeticamente ou para alimentar dispositivos eletrónicos de pequena
escala. O principal desafio da presente tese é o aprimoramento dos dispositivos para L-lactato,
uma biomolécula presente nos fluidos biológicos capaz de fornecer energia para BFCs assim
como fornecer informação fisionómica. Especificamente, este trabalho visa o desenvolvimento
de bioelétrodos enzimáticos baseados em lactato oxidase mais sustentáveis e simples para
potencial aplicação de biossensores autoalimentados para L-lactato. Para o efeito, um substrato
semelhante a papel com ouro impresso foi usado como elétrodo sendo modificado com
nanotubos de carbono e a enzima. O uso de um agente ligante foi estudado de forma a
aumentar a eficiência eletroanalítica, estabilidade e tempo de vida útil do bioelétrodo. Os
bioelétrodos com e sem o agente ligante foram testados e comparados por voltametria cíclica
e cronoampermetria na ausência e presença do analito L-lactato e ausência de oxigénio para se
também avaliar a transferência direta de eletrões. Verificou-se que o agente ligante melhorou
significativamente o desempenho eletroanalítico do bioelétrodo para L-lactato através da
geração de uma maior corrente anódica (1,6x superior) quando comparado com o biolétrodo
sem agente ligante, assim como uma sensibilidade para o L-lactato (2,3x superior) e um terço
do limite de deteção. A estabilidade foi também avaliada após duas semanas de
armazenamento. O biossensor com agente ligante manteve a sua atividade e funcionalidade,
enquanto o sistema sem agente de ligação não mostrou atividade. Em conclusão, os resultados
demonstram que o agente ligante melhora o desempenho eletroanalítico na determinação de
L-lactato e estabilidade sendo recomendável a sua inclusão no fabrico do bioelétrodo. Os
bioelétrodos desenvolvidos são assim simples e sustentáveis com potencialidade para serem
usados em BFCs e biossensores autoalimentados.
The creation of Biofuel Cells (BFCs) emerges as a promising solution for microscale energy production, relying on biological and more sustainable catalysts when compared, for example, to traditional fuel cells that use expensive catalysts with associated environmental costs. BFCs are an interesting way to generate micro-energy and can be advantageously used in selfpowered biosensors or to power small-scale electronic devices. The main challenge of the present thesis is the improvement of devices for L-lactate, a biomolecule found in biological fluids capable of providing energy for BFCs as well as providing physiognomic information. Specifically, this work aims at the development of more sustainable and simpler enzymatic bioelectrodes based on lactate oxidase for the potential application in self-powered biosensors for L-lactate. To this effect, a paper-like substrate with printed gold was used as the electrode, being modified with carbon nanotubes and the enzyme. The use of a binding agent was studied, to increase the electroanalytical efficiency, stability, and useful lifetime of the bioelectrode. The bioelectrodes with and without the binding agent were tested and compared by cyclic voltammetry and chronoamperometry in the absence and presence of the analyte L-lactate and absence of oxygen to also evaluate the direct electron transfer. It was found that the binding agent significantly improved the electroanalytical performance of the bioelectrode for L-lactate through the generation of a higher anodic current (1.6x higher) when compared to the bioelectrode without the binding agent, as well as a higher sensitivity for L-lactate (2.3x higher) and one-third of the limit of detection. The stability was also evaluated after two weeks of storage. The biosensor with the binding agent maintained its activity and functionality, while the system without the binding agent showed no activity. In conclusion, the results demonstrate that the binding agent improves the electroanalytical performance in the determination of L-lactate and stability, and its inclusion in the manufacture of the bioelectrode is recommended. The developed bioelectrodes are thus simple and sustainable, with the potential to be used in BFCs and self-powered biosensors.
The creation of Biofuel Cells (BFCs) emerges as a promising solution for microscale energy production, relying on biological and more sustainable catalysts when compared, for example, to traditional fuel cells that use expensive catalysts with associated environmental costs. BFCs are an interesting way to generate micro-energy and can be advantageously used in selfpowered biosensors or to power small-scale electronic devices. The main challenge of the present thesis is the improvement of devices for L-lactate, a biomolecule found in biological fluids capable of providing energy for BFCs as well as providing physiognomic information. Specifically, this work aims at the development of more sustainable and simpler enzymatic bioelectrodes based on lactate oxidase for the potential application in self-powered biosensors for L-lactate. To this effect, a paper-like substrate with printed gold was used as the electrode, being modified with carbon nanotubes and the enzyme. The use of a binding agent was studied, to increase the electroanalytical efficiency, stability, and useful lifetime of the bioelectrode. The bioelectrodes with and without the binding agent were tested and compared by cyclic voltammetry and chronoamperometry in the absence and presence of the analyte L-lactate and absence of oxygen to also evaluate the direct electron transfer. It was found that the binding agent significantly improved the electroanalytical performance of the bioelectrode for L-lactate through the generation of a higher anodic current (1.6x higher) when compared to the bioelectrode without the binding agent, as well as a higher sensitivity for L-lactate (2.3x higher) and one-third of the limit of detection. The stability was also evaluated after two weeks of storage. The biosensor with the binding agent maintained its activity and functionality, while the system without the binding agent showed no activity. In conclusion, the results demonstrate that the binding agent improves the electroanalytical performance in the determination of L-lactate and stability, and its inclusion in the manufacture of the bioelectrode is recommended. The developed bioelectrodes are thus simple and sustainable, with the potential to be used in BFCs and self-powered biosensors.
Descrição
Este estudo recebeu apoio dos projetos NATURIST 2022.07089.PTDC (doi: 10.54499/2022.07089.PTDC) e PaperSenseMIP PTDC/QUI-QAN/3899/2021
(doi: 10.54499/PTDC/QUI-QAN/3899/2021) da Fundação para a Ciência e Tecnologia (FCT), Ministério da Ciência, Tecnologia e Ensino Superior (MCTES) através de fundos nacionais.
Palavras-chave
Biocélulas de combustível Biossensores Bioelétrodos Enzimas L-lactato elétrodos de papel Biocélulas de combustível Biossensores Bioelétrodos Enzimas L-lactato Elétrodos de papel