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Electrosynthesis of biocompatible polycatecholamine films
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Resumo(s)
The combined role of catechol and amine groups in determining the adhesive properties of biomimetic adhesives and promoting favorable interactions for protein immobilization in bio-inspired polymers is a current topic of discussion with great potential to advance the development of biosensing technologies. This doctoral work explores the electrochemical synthesis of polycatecholamines and polycatechol providing fast, efficient, and reproducible coating of carbon and gold electrodes while delivering fine-tuning of the physicochemical properties of the deposited nanometric-thin films. Surface characterization is extensively employed by electrochemical techniques, ellipsometry, quartz crystal microbalance, contact angle goniometry, atomic force microscopy, reflectance infrared spectroscopy, and X-ray photoelectron spectroscopy.
Electrosynthesized polydopamine shows superior electroactivity and electron transfer properties regarding its chemically synthesized counterpart, which is attributed to a more organized polymeric structure comprising non-cyclized dopamine monomeric units and less incorporation of the indoline- and indole-type cyclized species.
During electropolymerization of catecholamines, the amine group accelerates deposition resulting in compact polydopamine and polynorepinephrine films. The presence of carboxyl groups inhibit deposition leading to slow growth and originating very thin and porous films of poly(3,4-dihydroxyphenylalanine) and poly(caffeic acid). Polycatechol and polynorepinephrine display the most regular growths and superior electroactivities.
A one-step potentiostatic method is proposed to co-immobilize fungal laccase and polydopamine on cheap and disposable graphite electrodes, as demonstrated by the very reproducible and highly catalytic responses, at pH 4.6, of several phenolic compounds (caffeic, rosmarinic and gallic acid), allowing the quantification of the phenol content of a chestnut shell extract from agro-industrial wastes. A bacterial laccase was successfully immobilized on graphite/polynorepinephrine modified electrodes, obtaining enhanced catalytic responses with respect to polydopamine modified electrodes, shifting the optimal working pH to neutral values.
A successful one-step modification strategy with ethanolamine allowed the synthesis of ready-to-use polydopamine-based immunosensing platforms that prevent non-specific adsorption without the need for additional chemical coupling reactions or blocking steps throughout the affinity assay. The use of polyDOPA did not improve the detection of anti-human immunoglobulin G with respect to polydopamine films, whereas polynorepinephrine, and especially polycatechol, greatly improved the optical sensitivity of the immunologic affinity assay.
Descrição
Palavras-chave
Catechol chemistry Polycatecholamine thin films Electropolymerization Electrochemical enzymatic biosensors Optical immunosensors Química do grupo catecol Filmes finos de policatecolaminas Eletropolimerização Biossensores enzimáticos eletroquímicos Imunossensores óticos