Exploration of novel materials in (bio)electrocatalysissensing in complex media and biocathodes for the co2 reduction

Resumen

Introduction Electron transfer processes involved in electrochemical reactions play an important role in a large number of biological and biochemical processes. Nowadays, the interest of the scientific community is focused on exploring and understanding the biological and chemical nature of bioelectrocatalytic phenomena that occur in living beings, in order to mimic them in the laboratory. The bioelectrocatalysis continues to pave the way for a large number of applications through the development of electrochemical biosensors, bioelectrosynthesis, energy storage, and energy conversion (bio)electrochemical sensors are devices that transform a chemical or physical information into an useful signal, through a transducer based on electrochemical processes, whose information is processed quickly and without the need for complex analysis. The improvement of sensitivity and selectivity of the electrochemical analytical devices is achieved through the use of catalysts or biocatalysts (bioreceptors), such as nanoparticulate metallic materials, carbon materials, phthalocyanines, enzymes, antibodies, redox proteins or deoxyribonucleic acid. However, there is still a huge interest in the development of electrochemical (bio)sensors that exhibit good performance, related to high sensitivity, specificity, durability, low cost and portability to perform electro-analytical measurements ex-situ and in-situ. For years, the use of biocatalysts has been strategically implemented on an industrial scale, in sectors such as fine chemistry or industrial chemistry for the production of chemical products and alternative fuels. Among the most used biocatalysts, enzymes and redox proteins are of great interest in electrochemistry due to their participation in the transfer of hydrides and/or electrons. On the other hand, the high selectivity of enzymes makes them relevant candidates to participate in different chemical transformation processes under mild reaction conditions, and all of this, together with considerable energy and economic savings. But undoubtedly, a great advance in the consolidation of the use of enzymes or biocatalysts in general on an industrial scale is largely due to the development of more efficient biomolecules immobilization methods on different materials. With reference to this, research in material science is being crucial for the search and breakthrough of new materials that enhance the stability and activity of the immobilized biocatalyst and, therefore, the performance of the bioreactor or electrochemical biosensor. In particular, carbon materials, for example, graphite, glassy carbon, graphene, carbon nanotubes, and nanoporous carbon materials are used and involved in many electrochemical applications thanks to their unique properties referred to their excellent thermal and electrical conductivity and mechanical resistance. Moreover, the possibility of modifying the textural, structural and superficial chemical properties of the carbonaceous material is of key significance, according to the performance of the bioreactor and the (bio)electrochemical sensor. Theoretical aspects The main investigations are summarized in the following three points: (I) This doctoral thesis pointed out, first of all, at the exploration of novel materials, design, and improvement of bioelectrocatalytic strategies, and fabrication of different electrochemical devices, mainly, with emphasis on the detection and determination of metabolites and/or biomarkers within complex human embryo cell culture media. (II) This doctoral thesis set out novel synthetic routes of carbon-based materials with higher control of pore size and pore size distribution. Such materials may offer a great opportunity to be used in fields such as sensing and biosensing, for its large surface areas, pore connectivity and ordered structure, biocompatibility, and mechanical and chemical stability. A paradigm in this doctoral thesis was the synthesis and the electrochemical characterization of macroporous carbons based materials obtained by the replication method. Furthermore, in this doctoral thesis, microporous materials which offered a bigger specificity regarding smaller molecules detection or specific adsorption/capture such as molecular hydrogen were also employed. (III) The doctoral thesis finally aimed at the search of bioelectrochemical processes regarding confined cytochrome c and formate dehydrogenase proteins into nanoporous carbon materials with well-developed mesoporosity. The immobilization of cytochrome c gave rise to the feasibility of electrochemical biosensor performance for the detection of hydrogen peroxide, although the use of confined cytochrome c as nanobioreactors for oxidative environmental remediation is still open. The second protein of study was related to the reduction of carbon dioxide, not only for the mitigation of the climate change but also for the carbon dioxide utilization towards the production of high added value chemicals and fuels. Conclusions The main conclusions of this thesis are the following: (I) The modification of screen-printed carbon electrode by drop casting of a composite made of carboxylated multi-walled carbon nanotubes and the biopolymer chitosan resulted to be the pavement for an effective immobilization of lactate oxidase required for the fabrication of a lactate electrochemical biosensor. The determination of lactate with high performance in real cell culture media coming from the activity of in vitro fertilization was successfully addressed. This doctoral thesis went far beyond the modification of the graphitic like working electrode, so the formulation ink of the screen-printed carbon platform was modified by the incorporation of cobalt phthalocyanine to prompt the electrocatalytic determination of the amino acid cysteine within human embryo cell culture media with excellent reproducibility and sensitivity. The depletion or production of such metabolites, i.e., lactate and cysteine, can be easily monitored ex-situ or in-situ by using the electrochemical (bio)sensors developed and optimised in this doctoral thesis. (II) A paradigm in this doctoral thesis was, in turn, the synthesis and the electrochemical characterization of macroporous carbons based materials obtained by the replication method. The macroporous carbon obtained from the replication method exhibited well ordered three-dimensional structure and adequate properties to be used as electrodes with applications in sensing of biomolecules. From the electrochemical study of two novel materials with intrinsic microporosity, two outstanding applications were discussed in this doctoral thesis. The first one referred to the carbonization of one polymer with intrinsic microporosity (PIM) giving rise to a material with a supercapacitive behaviour. Once the material was hydrated, it showed an activation/deactivation of the capacitance increase in a specific pH range. These properties made it a potential material to be presented as a capacitive pH sensor. The second one regarded the electrochemical characterization of the porous organic cage CC3 that allowed for capturing and storing molecular hydrogen with astonishing applications in energy storage. (III) The use of mesoporous carbon materials was pivotal for successful immobilization of cytochrome c and formate dehydrogenase from Candida Boidinii (cbFDH). Particularly, the confinement of both proteins was found to be dependent on the cavity and neck pore size, being necessary at least to match pore and protein dimensions. Proteins activity was retained after confinement into the mesoporous carbons. Beyond adsorption, this doctoral thesis targeted successfully the co-immobilization of the cbFDH and the redox mediator [Cp * Rh (bpy) Cl] Cl, the latter needed for the regeneration of the cofactor NADH, into a micro/mesoporous carbon-based material for the preparation of a biocathode pointing at the electrochemically conversion of carbon dioxide to formic acid. References 1. Akram, M. S.; Rehman, J. U.; Hall, E. A. H., Engineered proteins for bioelectrochemistry. In Annual Review of Analytical Chemistry, Annual Reviews Inc.: 2014; Vol. 7, pp 257-274. 2. 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