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Abstract(s)
Com uma população em constante crescimento, surge uma procura energética cada vez maior. A maior parte dessa energia provém cada vez mais de fontes renováveis, e as células de biocombustível podem bem fazer parte desta solução. Assim, o principal objetivo deste trabalho foi o desenvolvimento de uma célula a biocombustível baseada em papel, que pode servir como biossensor autossuficiente para medir os níveis de lactato em amostras. A célula de biocombustível foi composta por um bio ânodo baseado na imobilização da enzima lactato oxidase em elétrodos de papel nano estruturados modificados com um mediador redox,
enquanto o bio cátodo foi composto pela enzima bilirrubina oxidase ligada ao elétrodo de papel nano estruturado. O design da célula de biocombustível envolveu uma abordagem mais sustentável e economicamente viável, uma vez que foi baseada em elétrodos de papel. Experimentalmente, o primeiro passo consistiu na fabricação dos elétrodos de papel, comparando, através de voltametria cíclica (CV), diferentes materiais e estratégias na impressão em tela dos elétrodos, bem como diferentes nano materiais de carbono na nano estruturação dos elétrodos, para determinar qual seria o mais adequado na montagem do biossensor. A partir desses resultados, foi determinado que os bio elétrodos de papel (PMW) seriam construídos com conectores de ouro impressos em tela e nanotubos de carbono de paredes múltiplas
(MWCNT) aplicados por gotejamento. Posteriormente, foi realizada a caracterização individual tanto do bio ânodo de lactato oxidase (LOx) (PMW-NQ/LOx) quanto do bio cátodo de BOx (bilirrubina oxidase) (PMW/BOx) como biossensores na determinação dos respetivos substratos enzimáticos, nomeadamente, L-lactato e oxigénio. O bio elétrodo PMW/BOx apresentou uma sensibilidade de 7x10-6 A/mM e um limite de deteção (LOD) de 0,007 mM para oxigênio, enquanto o bio elétrodo PMW-NQ/LOx apresentou uma sensibilidade de 2x10-6 A/mM e um LOD de 0,024 mM para L-lactato. Finalmente, a célula a biocombustível foi montada usando o bio ânodo PMW-NQ/LOx e o bio cátodo PMW/BOx e caracterizada através da determinação da
corrente (curvas de polarização) e da potência gerada (curvas de potência) em concentrações crescentes de L-lactato na presença de oxigénio (solução saturada com ar). O potencial de circuito aberto (OCP) máximo alcançado correspondeu a 0,62 V (5 mM). Foi possível obter uma correlação entre a potência gerada e as concentrações de L-lactato. A curva de calibração determinou um intervalo linear até 3 mM, uma sensibilidade de 3x10-7 A/mM e um LOD de 0,94 mM. A célula de biocombustível de L-lactato/O2 baseada em papel pode, assim, ser usada como um biossensor autossuficiente na deteção de L-lactato, caracterizando-se como uma ferramenta analítica simples e sustentável.
With an ever-growing population comes an ever-growing energy demand. Most of that energy now increasingly comes from renewable sources, and biofuel cells may well be part of this solution. Thus, the main goal of this work was the development of a paper-based biofuel cell, which can serve as a self-powered biosensor to measure lactate levels in samples. The biofuel cell was composed of a bioanode based on the immobilization of the enzyme lactate oxidase onto nanostructured paper-based electrodes modified with a redox mediator, while the biocathode was composed of the enzyme bilirubin oxidase tethered to the nanostructured paper-based electrode. The design of the biofuel cell involved a more environmentally sustainable and cost-effective approach since it was based on paper electrodes. Experimentally, the first step consisted of the fabrication of the paper-based electrodes, comparing, through cyclic voltammetry (CV), different materials and strategies in screen printing the electrodes, as well as different carbon nanomaterials in the nanostructuring of the electrodes, to determine which would be the most suitable for the biosensor assembly. From these results, it was determined that the paper-based bioelectrodes (PMW) would be constructed with screenprinted gold connectors and multi-walled carbon nanotubes (MWCNT) applied by dropcasting. Subsequently, individual characterization of both the LOx bioanode (PMW-NQ/LOx) and the BOx biocathode (PMW/BOx) was performed as biosensors in the determination of their respective enzymatic substrates, namely L-lactate and oxygen. The PMW/BOx bioelectrode showed a sensitivity of 7x10-6 A/mM and a limit of detection (LOD) of 0.007 mM for oxygen, while the PMW-NQ/LOx bioelectrode showed a sensitivity of 2x10-6 A/mM and a LOD of 0.024 mM for Llactate. Finally, the biofuel cell was assembled using the PMW-NQ/LOx bioanode and the PMW/BOx biocathode and characterized through the determination of the current (polarization curves) and the generated power (power curves) at increasing concentrations of L-lactate in the presence of oxygen (air-saturated solution). The maximum open-circuit potential (OCP) achieved corresponded to 0.62 V (5 mM). A correlation was obtained between the generated power and the L-lactate concentrations. The calibration curve determined a linear range up to 3 mM, a sensitivity of 3x10-7 A/mM, and a LOD of 0.94 mM. Thus, the paper-based L-lactate/O2 biofuel cell can be used as a self-powered biosensor in the detection of L-lactate, characterized as a simple and sustainable analytical tool.
With an ever-growing population comes an ever-growing energy demand. Most of that energy now increasingly comes from renewable sources, and biofuel cells may well be part of this solution. Thus, the main goal of this work was the development of a paper-based biofuel cell, which can serve as a self-powered biosensor to measure lactate levels in samples. The biofuel cell was composed of a bioanode based on the immobilization of the enzyme lactate oxidase onto nanostructured paper-based electrodes modified with a redox mediator, while the biocathode was composed of the enzyme bilirubin oxidase tethered to the nanostructured paper-based electrode. The design of the biofuel cell involved a more environmentally sustainable and cost-effective approach since it was based on paper electrodes. Experimentally, the first step consisted of the fabrication of the paper-based electrodes, comparing, through cyclic voltammetry (CV), different materials and strategies in screen printing the electrodes, as well as different carbon nanomaterials in the nanostructuring of the electrodes, to determine which would be the most suitable for the biosensor assembly. From these results, it was determined that the paper-based bioelectrodes (PMW) would be constructed with screenprinted gold connectors and multi-walled carbon nanotubes (MWCNT) applied by dropcasting. Subsequently, individual characterization of both the LOx bioanode (PMW-NQ/LOx) and the BOx biocathode (PMW/BOx) was performed as biosensors in the determination of their respective enzymatic substrates, namely L-lactate and oxygen. The PMW/BOx bioelectrode showed a sensitivity of 7x10-6 A/mM and a limit of detection (LOD) of 0.007 mM for oxygen, while the PMW-NQ/LOx bioelectrode showed a sensitivity of 2x10-6 A/mM and a LOD of 0.024 mM for Llactate. Finally, the biofuel cell was assembled using the PMW-NQ/LOx bioanode and the PMW/BOx biocathode and characterized through the determination of the current (polarization curves) and the generated power (power curves) at increasing concentrations of L-lactate in the presence of oxygen (air-saturated solution). The maximum open-circuit potential (OCP) achieved corresponded to 0.62 V (5 mM). A correlation was obtained between the generated power and the L-lactate concentrations. The calibration curve determined a linear range up to 3 mM, a sensitivity of 3x10-7 A/mM, and a LOD of 0.94 mM. Thus, the paper-based L-lactate/O2 biofuel cell can be used as a self-powered biosensor in the detection of L-lactate, characterized as a simple and sustainable analytical tool.
Description
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.
Keywords
Paper-based Biofuel Cell Biosensor Lactate Enzymes Carbon Nanotubes Papel Células de biocombustível Biossensor Lactato Enzimas Nanotubos de carbono