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Funding Information: Open access funding provided by FCT|FCCN (b-on). This work was financed by national funds from Fundação para a Ciência e a Tecnologia (FCT), I.P., in the scope of the projects LA/P/0037/2020, UIDP/50025/2020, and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication–i3N and by FEDER funds through the COMPETE 2020 Program and National Funds through Portuguese Foundation for Science and Technology under projects POCI-01–0145-FEDER-007688, UID/CTM/50025 and by ERC AdG grant from the project DIGISMART (ERC-AdG-2017, GA 787410). J.C. would like to acknowledge FCT/MCTES for his present research contract with reference CEECIND/00880/2018. R.C. acknowledges funding from i3N-FCT I.P. through the PhD Grant UI/BD/151295/2021. S. S. and T. P. also acknowledge the funding from National Foundation for Science and Technology, through the PhD Grants SFRH/BD/149751/2019 and 2020.08606.BD, respectively. Publisher Copyright: © 2022, The Author(s). Laser-induced graphene (LIG) is as a promising material for flexible microsupercapacitors (MSCs) due to its simple and cost-effective processing. However, LIG-MSC research and production has been centered on non-sustainable polymeric substrates, such as polyimide. In this work, it is presented a cost-effective, reproducible, and robust approach for the preparation of LIG structures via a one-step laser direct writing on chromatography paper. The developed strategy relies on soaking the paper in a 0.1 M sodium tetraborate solution (borax) prior to the laser processing. Borax acts as a fire-retardant agent, thus allowing the laser processing of sensitive substrates that other way would be easily destroyed under the high-energy beam. LIG on paper exhibiting low sheet resistance (30 Ω sq−1) and improved electrode/electrolyte interface was obtained by the proposed method. When used as microsupercapacitor electrodes, this laser-induced graphene resulted in specific capacitances of 4.6 mF cm−2 (0.015 mA cm−2). Furthermore, the devices exhibit excellent cycling stability (> 10,000 cycles at 0.5 mA cm−2) and good mechanical properties. By connecting the devices in series and parallel, it was also possible to control the voltage and energy delivered by the system. Thus, paper-based LIG-MSC can be used as energy storage devices for flexible, low-cost, and portable electronics. Additionally, due to their flexible design and architecture, they can be easily adapted to other circuits and applications with different power requirements. Graphical Abstract: [Figure not available: see fulltext.] publishersversion published

Diabetes is a heterogeneous and multifactorial disease. However, glycemia and glycated hemoglobin have been the focus of diabetes diagnosis and management for the last decades. As diabetes management goes far beyond glucose control, it has become clear that assessment of other biochemical parameters gives a much wider view of the metabolic state of each individual, enabling a precision medicine approach.In this review, we summarize and discuss indexes that have been used in epidemiological studies and in the clinical practice.Indexes of insulin secretion, sensitivity/resistance and metabolism have been developed and validated over the years to account also with insulin, C-peptide, triglycerides or even anthropometric measures. Nevertheless, each one has their own objective and consequently, advantages and disadvantages for specific cases. Thus, we discuss how new technologies, namely new sensors but also new softwares/applications, can improve the diagnosis and management of diabetes, both for healthcare professionals but also for caretakers and, importantly, to promote the empowerment of people living with diabetes.In long-term, the solution for a better diabetes management would be a platform that allows to integrate all sorts of relevant information for the person with diabetes and for the healthcare practitioners, namely glucose, insulin and C-peptide or, in case of need, other parameters/indexes at home, sometimes more than once a day. This solution would allow a better and simpler disease management, more adequate therapeutics thereby improving patients' quality of life and reducing associated costs.

The appearance and quick spread of the new severe acute respiratory syndrome coronavirus disease, COVID-19, brought major societal challenges. Importantly, suitable medical diagnosis procedures and smooth clinical management of the disease are an emergent need, which must be anchored on novel diagnostic methods and devices. Novel molecular diagnostic tools relying on nucleic acid amplification testing have emerged globally and are the current gold standard in COVID-19 diagnosis. However, the need for widespread testing methodologies for fast, effective testing in multiple epidemiological scenarios remains a crucial step in the fight against the COVID-19 pandemic. Biosensors have previously shown the potential for cost-effective and accessible diagnostics, finding applications in settings where conventional, laboratorial techniques may not be readily employed. Paper- and cellulose-based biosensors can be particularly relevant in pandemic times, for the renewability, possibility of mass production with sustainable methodologies, and safe environmental disposal. In this review, paper-based devices and platforms targeting SARS-CoV-2 are showcased and discussed, as a means to achieve quick and low-cost PoC diagnosis, including detection methodologies for viral genomic material, viral antigen detection, and serological antibody testing. Devices targeting inflammatory markers relevant for COVID-19 are also discussed, as fast, reliable bedside diagnostic tools for patient treatment and follow-up., The authors acknowledge funding through projects Eco2Covid (POCI-01-02B7-FEDER-068174) and TecniCov (POCI-01-02B7-FEDER-069745), co-funded by FEDER through COMPETE2020 and Lisboa2020. T.P., A.R.C. and A.C.M. acknowledge funding to National Foundation for Science and Technology, I.P., FCT, through their PhD grants, references DFA/BD/8606/2020, SFRH/BD/130107/2017 and SFRH/BD/115173/2016, respectively, info:eu-repo/semantics/publishedVersion

The plasmonic properties of gold nanoparticles (AuNPs) are a promising tool to develop sensing alternatives to traditional, enzyme-catalyzed reactions. The need for sensing alternatives, especially in underdeveloped areas of the world, has given rise to the application of nonenzymatic sensing approaches paired with cellulosic substrates to biochemical analysis. Herein, we present three individual, low-step, wet-chemistry, colorimetric assays for three target biomarkers, namely, glucose, uric acid, and free cholesterol, relevant in diabetes control and their translation into paper-based assays and microfluidic platforms for multiplexed analysis. For glucose determination, an in situ AuNPs synthesis approach was applied into the developed μPAD, giving semiquantitative measures in the physiologically relevant range. For uric acid and cholesterol determination, modified AuNPs were used to functionalize paper with a gold-on-paper approach with the optical properties changing based on different aggregation degrees and hydrophobic properties of particles dependent on analyte concentration. These paper-based assays show sensitivity ranges and limits of detection compatible for target analyte level determination and detection limits comparable to those of similar enzymatic, colorimetric systems, relying only on plasmonic transduction without the need for enzymatic activity or other chromogenic substrates. The resulting paper-based assays were integrated into a single 3D, multiplex paper-based device using paper microfluidics, showing the capability for performing different colorimetric assays with distinct requirements in terms of sample flow and sample uptake in test zones using a combination of both horizontal and vertical flows inside the same device. The presented device allows for multiparametric, colorimetric measures of different metabolite levels from a single complex sample matrix drop using digital color analysis, showing the potential for development of low-cost, low-complexity tools for diagnostics toward the point-of-care.

The demand for smart, wearable devices has been dictating our daily life with the evolution of integrated miniaturized electronics. With technological innovations, comes the impactful human footprint left on the planet’s ecosystems. Therefore, it is necessary to explore renewable materials and sustainable methodologies for industrial processes. Here, an eco-friendly approach to producing flexible electrodes based on a single-step direct laser writing is reported. A 1.06 µm wavelength fiber laser was used for the first time to produce porous three-dimensional laser-induced graphene (LIG) on an agglomerated cork substrates. The obtained material exhibits the typical Raman spectra, along with an exceptionally low sheet resistance between 7.5 and 10 ohm sq−1. LIG on cork high electrical conductivity and the friendliness of the used production method, makes it an interesting material for future technological applications. To show its applicability, the production of planar micro-supercapacitors was demonstrated, as a proof of concept. Electrochemical performance studies demonstrate that LIG interdigitated electrodes, using PVA-H2SO4 electrolyte, achieve an area capacitance of 1.35 mF cm−2 (103.63 mF cm−3) at 5 mV s−1 and 1.43 mF cm−2 (109.62 mF cm−3) at 0.1 mA cm−2. In addition, devices tested under bending conditions exhibit a capacitance of 2.20 mF cm−2 (169.22 mF cm−3) at 0.1 mA cm−2. Here, showing that these electrodes can be implemented in energy storage devices, also successfully demonstrating LIG promising application on innovative, green, and self-sustaining platforms.

This study presents results obtained from interviews took by a team of researchers from a chosen group of public servants in four Brazilian state governments (Sergipe, Goiás, Rio Grande do Sul and Santa Catarina) during the year of 2013. Our aim was to question such policy makers about intergovernmental relations developed by them in their everyday public duties. It was investigated their own positions on institutional issues, successful and critical points, as well as their views on agreements and negotiations among federative entities. In sum, our interests lied on elements to realize and contrast dynamics, obstacles and consensus present on intergovernmental relations in Brazilian federalism.

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2016 Submitted by Biblioteca da Faculdade de Medicina da Universidade de Lisboa (repositorio@medicina.ulisboa.pt) on 2017-07-20T14:37:23Z No. of bitstreams: 1 TomasPSilva.pdf: 2615488 bytes, checksum: e7d6455b03fc219a4086e52e61ca164d (MD5) Made available in DSpace on 2017-11-03T11:39:27Z (GMT). No. of bitstreams: 1 TomasPSilva.pdf: 2615488 bytes, checksum: e7d6455b03fc219a4086e52e61ca164d (MD5) Previous issue date: 2016

Este trabalho estuda a economia política do desenvolvimento regional no Rio Grande do Sul a partir da Constituição de 1988, para responder à seguinte pergunta: nas atuais condições estruturais, quais as possibilidades de retomarmos o desenvolvimento regional equilibrado, com suporte do Estado e maior dinâmica endógena? Com o objetivo de construir uma análise teórica comprometida com a ação, partimos da seguinte hipótese: a heterogeneidade estrutural da economia gaúcha, parcialmente inserida no atual padrão internacional de acumulação, corresponde a uma heterogeneidade político-institucional na qual diferentes circuitos de poder, que não se comunicam no interior do Estado, dispersam os escassos recursos sem uma estratégia de desenvolvimento integradora do território, o que vem reproduzindo as desigualdades regionais internas. Chamamos essa combinação de heterogeneidade estrutural e institucional de “heterogeneidade estruturante” da economia política estadual. O marco teórico escolhido é baseado no “possibilismo” de Hirschman, em sua análise sobre a indução pública da habilidade para o investimento, que tratamos analogamente nos termos institucionais de Peter Evans, avaliando as capacidades estatais a partir do weberianismo da burocracia e do enraizamento do Estado. Analisando os condicionantes sistêmicos e as dinâmicas internas da economia política estadual, concluímos que o planejamento regional para a redução de desigualdades não obtém resultados expressivos por encontrar-se aprisionado no circuito orçamentário do Estado, onde uma burocracia fraca e pouco prestigiada é suplantada pelas decisões políticas, apesar dos esforços crescentes de reflexão e aprofundamento democrático nesse circuito. Por outro lado, argumentamos que as ações desenvolvimentistas existentes são do tipo passivo e subordinado ao circuito do grande capital, resumindo-se à atração de investimentos multinacionais em que o desequilíbrio territorial tem pouca ou nenhuma influência nas decisões de alocação. Por fim, a maior capacidade estatal encontra-se no circuito tecnocrático, cujo envolvimento com os objetivos estratégicos e vontades sociais é quase nulo, caracterizando uma espécie de despotismo-racional. This work offers an approach to the political economy of regional development in the Rio Grande do Sul state after the 1988 Constitution. It seeks to answer the following question: in the structural conditions observed, is it possible to return to a balanced regional development, with state support and increased endogenous dynamics? In order to build a theoretical analysis committed to policy planning and action, we start from the following hypothesis: the structural heterogeneity of the regional economy of Rio Grande do Sul, partially inserted in the current international pattern of accumulation, corresponds to a political-institutional heterogeneity in which different power circuits work independently to scatter the scarce resources without an integrated development strategy for the territory. We named this combination of structural and institutional heterogeneity as the “structuring heterogeneity” of the political economy of the subnational state. The chosen theoretical framework is based on Hirschman’s "possibilism" and his analysis of the public induced ability for investment. We argued that Peter Evans’ approach for the Embedded Autonomy is a contemporary analogous formulation, using it to assess the developmentalism capacities through the bureaucratic level in a “weberian” scale and social embeddedness of the state. Analyzing the systemic constraints and the internal dynamics of the political economy of Rio Grande do Sul, we conclude that, in fact, the regional planning for the reduction of inequalities do not get significant results because it is trapped in the budgetary circuit, where a weak bureaucracy, with no prestige, is surpassed by political decisions, despite the increasing planning efforts and democratic deepening in the last few years. On the other hand, we argue that the developmental actions are passive and subordinated to the big capital circuit, where the main policies focus on the attraction of multinational investments and have little consideration for the regional imbalances entailed. Finally, the largest state capacity is within the technocratic circuit, which it not involved with the strategic objectives and social needs, a behavior we called rational-despotism.

O presente trabalho trata da utilização dos métodos contemporâneos que combinam as Ciências Política e Econômica para o estudo dos regimes de propriedade dos hidrocarbonetos na América Latina. O ponto de partida é uma discussão ontológica e epistemológica sobre a produção teórica da chamada Nova Economia Política Internacional e suas raízes. O que torna os hidrocarbonetos tão importantes do ponto de vista estratégico é o fato de, com o carvão mineral, constituírem o conjunto dominante de fontes primárias de energia no mundo contemporâneo, inclusive para a geração elétrica. Além do alcance global como commodity comercializável, os combustíveis fósseis representam um estoque de riqueza finito e geograficamente concentrado, impactando as relações econômicas domésticas e internacionais dos Estados envolvidos. A pergunta central é: por que os governos optam por políticas energéticas “orientadas para a estratégia” ou “orientadas para o mercado”? Políticas orientadas ao mercado têm o objetivo de promover a competitividade, minimizando suas falhas para alcançar a eficiência sob iniciativa privada. Já as políticas orientadas para estratégia são caracterizadas pelo controle efetivo da atividade do setor por parte do Estado, a fim de consolidar um planejamento mais amplo que pode incluir política industrial, geração de empregos, manutenção de preços, aumento da receita pública, política exterior, etc. O objeto de análise é, portanto, o regime de propriedade adotado e o processo através do qual ele se consolida. A hipótese é de que a política final é resultado de uma interação simultânea entre interesses domésticos e internacionais, definidos pelo efeito-renda da variação dos preços, nível de pressão por redistribuição e características das instituições de agregação de preferências no primeiro caso; e vulnerabilidade diante da oferta e sensibilidade à variações de preço no mercado internacional no segundo. Assim, exclui-se, por hipótese, as explicações baseadas em preferências puramente ideológicas e político-partidárias, para testar o capacidade explicativa do interesse político-econômico racionalizável a partir de premissas simples. A pressão por redistribuição é instrumentalizada por uma combinação entre desigualdade (medida pelo índice de Gini) e imobilidade do recurso (constante e alta). As instituições são instrumentalizadas enquanto divisão formal de poderes (pontos de veto) e divisão de propósitos (pontos de veto efetivos), segundo trabalho de Haggard e McCubbins (2001). Vulnerabilidade e sensibilidade derivam da intensidade energética, medida como consumo/PIB e comércio líquido com o exterior. O método é lógico-dedutivo, partindo de uma revisão crítica das metodologias da área e fazendo uma síntese própria, para finalmente contrastar as previsões com os casos observados. Combina elementos da modelagem cientificista, associada ao mainstream da Ciência Política e Economia, com idiossincrasias regionais e setoriais, resultando em um modelo específico, a fim de delinear a fronteira entre a capacidade de generalização e o estudo histórico. Na verificação dos cinco casos – Brasil, Bolívia, Venezuela, México e Argentina – as previsões do modelo lógico-dedutivo se confirmaram. Concluímos que a contribuição é importante para a sistematização da análise e a escolha de casos para estudo em profundidade. This work posits a contemporary method that combines Political Science and Economics to analyze the hydrocarbons property regimes in Latin America. The starting point is an ontological and epistemological debate on the theoretical production of the so-called New International Political Economy and its classical foundations. What makes the hydrocarbon industry so important, from the strategic point of view, is the fact that it constitutes the dominant primary energy source in the modern world, including for the electricity supply. Besides its worldwide range as a tradable commodity, the fossil fuel represents a finite stock of wealth that is geographically concentrated, causing impact on the domestic and international economic relations of the States involved. The central question is: why does the government choose between strategicoriented and market-oriented policies alike? Market-oriented policies aim to promote competition, minimize failures and guarantee efficiency under private initiative. Oppositely, strategic-oriented policies are defined as the effective control of the production by the State, which aims at wider planning strategies such as industrial policies, employment generation, price stability, revenue increase, foreign policy, etc. The study subject, then, is the property regime adopted and the process through which it comes about. The hypothesis is that the final policy is an outcome of a simultaneous interaction between domestic and international interests. These are defined by the income-effect of the price variation, level of the pressure for redistribution and the characteristics of the institutions whereby preferences aggregate, on the one hand; and the vulnerability of supply and sensibility to price stability in the international markets, on the other. That said, it is also excluded, by hypothesis, the explanation based on ideological grounds, so to test the explaining power of the rationalizable political-economic interests. The pressure for redistribution is instrumentalized as a combination of inequality (measured as the Gini Coefficient) and asset immobility (which is constantly high in our case). The institutional environment is classified by its formal power sharing (veto points) and division of purposes (effective veto points), according to Haggard and McCubbins (2001). Vulnerability and sensibility are associated with energy intensity, measured as consumption over GDP, and net trade. The method is logical-deductive, deriving from a critical review of the current alternative methods and building our own synthesis. After that, we test the predictions against real observations. In that sense, it combines the so-called scientific approach to social sciences, usually associated with the orthodox literature, with ad hoc adjustments that intend to respect regional and sector idiosyncrasies. The result is an asset-specific framework that contributes to draw the frontier between generalization and historical-sociology in a pragmatic way, respecting the importance of both approaches and its combination. In the five cases studied - Brazil, Bolivia, Venezuela, Mexico and Argentina - the model predictions were confirmed. We conclude that this was an important contribution for the selection of emblematic cases to study in depth.

Estágio realizado na ColepCCL e orientado pelo Eng.ª Paula Martins Tese de mestrado integrado. Enegnharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2008

Laser-induced graphene (LIG) has gained preponderance in recent years, as a very attractive material for the fabrication and patterning of graphitic structures and electrodes, for multiple applications in electronics. Typically, polymeric substrates, such as polyimide, have been used as precursor materials, but other organic, more sustainable, and accessible precursor materials have emerged as viable alternatives, including cellulose substrates. However, these substrates have lacked the conductive and chemical properties achieved by conventional LIG precursor substrates and have not been translated into fully flexible, wearable scenarios. In this work, we expand the conductive properties of paper-based LIG, by boosting the graphitization potential of paper, through the introduction of external aromatic moieties and meticulous control of laser fluence. Colored wax printing over the paper substrates introduces aromatic chemical structures, allowing for the synthesis of LIG chemical structures with sheet resistances as low as 5 Ω·sq–1, translating to an apparent conductivity as high as 28.2 S·cm–1. Regarding chemical properties, ID/IG ratios of 0.28 showcase low defect densities of LIG chemical structures and improve on previous reports on paper-based LIG, where sheet resistance has been limited to values around 30 Ω·sq–1, with more defect dense and less crystalline chemical structures. With these improved properties, a simple transfer methodology was developed, based on a water-induced peel-off process that efficiently separates patterned LIG structures from the native paper substrates to conformable, flexible substrates, harnessing the multifunctional capabilities of LIG toward multiple applications in wearable electronics. Proof-of concept electrodes for electrochemical sensors, strain sensors, and in-plane microsupercapacitors were patterned, transferred, and characterized, using paper as a high-value LIG precursor for multiples scenarios in wearable technologies, for improved sustainability and accessibility of such applications., This work is funded by National Funds through FCT I.P., under the scope of the project UIDB/50025/2020-2023. The authors acknowledge the ERC AdG project DIGISMART ref 787410, EC project SYNERGY H2020-WIDESPREAF-2020-5, CSA, proposal number 952169, EC project EMERGE, No. 101008701, and project BEST - ALT20-03-0247-FEDER-113469 | LISBOA-01-0247-FEDER-113469. T.P. and R.C. acknowledge funding from FCT I.P. through the Ph.D. Grants DFA/BD/8606/2020 and UI/BD/151295/2021. The authors also want to thank Jonas Deuermeier for the help with XPS measurements and analysis., info:eu-repo/semantics/publishedVersion

The development of accurate, reliable, inexpensive and fully recyclable analytical platforms is of utmost relevance to several fields from medical diagnosis to environmental screening. Surface-enhanced Raman spectroscopy (SERS) is a compelling detection method with high specificity and sensitivity. In this work, a microwave-assisted synthesis method was used for fast and uniform in situ growth of gold nanoparticles (AuNPs) onto nanocellulose (NC) membranes, through a seedmediated process. The as-prepared membranes were fully optimized and its application as SERS platforms was demonstrated. A direct comparison with other cellulose-based substrates showed the superior characteristics of NC such as high mechanical strength, high surface area and lower porous content. An Enhancement Factor (EF) up to 106 was obtained using rhodamine 6G (R6G) 10-6 M as probe molecule and a remarkable shelf life of at least 7 months was achieved, with no special storage required. Preliminary results on the detection of label-free spike protein present in SARSCoV-2 virus are shown, through direct measurements on the optimized SERS membrane. We believe that this work evidences the effectiveness of in situ seed-mediated microwave-assisted synthesis as a fabrication method, the high stability of AuNPs and the superior characteristics of NC substrates to be used as SERS platforms., This work is funded by National Funds through FCT I.P., under the scope of the project UIDB/50025/2020-2023. The authors acknowledge the ERC AdG project DIGISMART ref. 787410 and EC project SYNERGY H2020-WIDESPREAD-2020-5, CSA, proposal n° 952169. Also, the authors thank funding co-financed by the Operational Programme for Competitiveness and Internationalisation (COMPETE 2020) and Lisbon Regional Operational Programme (Lisboa 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF) under the projects ECO2COVID ref. 68174 and TecniCOV ref. 69745. A. C. Marques acknowledges funding from FCT I.P., through the PhD Grant SFRH/BD/115173/2016. The authors acknowledge Professor Pedro Costa from KAUST for the TEM imaging., info:eu-repo/semantics/publishedVersion

Since the discovery of laser-induced graphene (LIG), significant advances have been made to obtain green LIG (gLIG) from abundant, eco-friendly, natural, and organic renewable bio-based carbon sources. Recently, some sustainable and cost-effective electronic devices have been designed with gLIG, resulting in diverse solutions to the environmental impact caused by electronic waste (e-waste). However, there are still several challenges that must be addressed regarding the widespread market implementation of gLIG-based products, from synthesis to practical applications. In this review, we focus on sustainable precursor sources, their conversion mechanisms, physical and chemical properties and applications, along with the challenges related to its implementation, showing the future opportunities and perspectives related to this promising new material. Various systems based on gLIG for energy storage, electrocatalysis, water treatment, and sensors have been reported in the literature. Additionally, gLIG has been proposed for ink formulation or incorporation into polymer matrices, to further expand its use to non-carbon-based substrates or applications for which pristine LIG cannot be directly used. In this way, it is possible to apply gLIG on diverse substrates, aiming at emerging wearable and edible electronics. Thus, this review will bring an overview of gLIG developments, in accordance with the European Green Deal, the United Nations Sustainable Development Goals and the new era of internet-of-things, which demands cost-effective electronic components based on the principles of energy efficiency and sustainable production methods.

Laser irradiation to induce networks of graphene-based structures toward cost-effective, flexible device fabrication is a highly pursued area, with applications in various polymeric substrates. This work reports the application of this approach toward commonly available, eco-friendly, low-cost substrates, namely, chromatographic and office papers. Through an appropriate chemical treatment with sodium tetraborate as a fire-retardant agent, photothermal conversion to porous laser-induced graphene (LIG) on paper is achieved. Raman peaks are identified, with I2D/IG and ID/IG peak ratios of 0.616 ± 0.095 and 1.281 ± 0.173, showing the formation of multilayered graphenic material, exhibiting sheet resistances as low as 56.0 sq1. Coplanar, LIG-based, three-electrode systems (working, counter and reference electrodes) are produced and characterized, showing high current Faradaic oxidation and reduction peaks, translating in high electrochemical active area, doubling the geometric area. Good electron transfer kinetics performed exclusively with on-chip measurements are reached, with k0 values as high as 7.15 × 104 cm s1. Proof-of-concept, amperometric, enzymatic glucose biosensors are developed, exhibiting good analytical performance in physiologically relevant glucose levels, with results pointing to the applicability of paper-based LIG toward efficient, disposable electrochemical sensor development, increasing their sustainability and accessibility, while simplifying their production and reducing their cost., This work was funded by National Funds through FCT I.P. under the scope of the project UIDB/50025/2020-2023. The authors acknowledge the ERC AdG project DIGISMART ref. 787410 and EC project SYNERGY H2020-WIDESPREAF-2020-5, CSA, proposal number 952169. T. Pinheiro acknowledges funding from FCT I.P. through the Ph.D. Grant DFA/ BD/8606/2020. S. Silvestre acknowledges funding from FCT I.P. through the Ph.D. Grant SFRH/BD/149751/2019. A.C. Marques acknowledges funding from FCT I.P. through the Ph.D. Grant SFRH/BD/115173/2016, info:eu-repo/semantics/publishedVersion

Due to its properties, paper represents an alternative to perform point-of-care tests for colorimetric determination of glucose levels, providing simple, rapid, and inexpensive means of diagnosis. In this work, we report the development of a novel, rapid, disposable, inexpensive, enzyme-free, and colorimetric paper-based assay for glucose level determination. This sensing strategy is based on the synthesis of gold nanoparticles (AuNPs) by reduction of a gold salt precursor, in which glucose acts simultaneously as reducing and capping agent. This leads to a direct measurement of glucose without any enzymes or depending on the detection of intermediate products as in conventional enzymatic colorimetric methods. Firstly, we modelled the synthesis reaction of AuNPs to determine the optical, morphological, and kinetic properties and their manipulation for glucose sensing, by determining the influence of each of the reaction precursors towards the produced AuNPs, providing a guide for the manipulation of nucleation and growth. The adaptation of this synthesis into the developed paper platform was tested and calibrated using different standard solutions with physiological concentrations of glucose. The response of the colorimetric signals obtained with this paper-based platform showed a linear behavior until 20 mM, required for glycemic control in diabetes, using the Red &times, Value/Grey feature combination as a calibration metric, to describe the variations in color intensity and hue in the spot test zone. The colorimetric sensor revealed a detection limit of 0.65 mM, depending on calibration metric and sensitivity of 0.013 AU/mM for a linear sensitivity range from 1.25 to 20 mM, with high specificity for the determination of glucose in complex standards with other common reducing interferents and human serum.