Sol-gel technology in enzymatic electrochemical biosensors for clinical analysis

Electrogeneration of non-electroactive and non-conducting materials: a counterintuitive concept for the functionalization and nanostructuration of electrode surfaces

“…Thanks to their synthesis at room temperature and under mild conditions, sol-gel oxides are good hosts for the encapsulation and stabilization of biochemicals such as enzymes, antibodies, living cells and bacteria [248]. Sol-gel bioencapsulation, by keeping the biological activity of the immobilized biorecognition elements [201][202][203], leads to bioceramic materials that are attractive for the development of biosensors [249][250][251]. For bioelectrochemical applications, the bioceramic materials needs to be in contact with a conductive surface, which is usually achieved by dispersing biocomposite particles into conductive matrices or by coating bioceramic films formed by evaporation on electrodes [40,43,252], which is however not appropriate for uniform deposition on surfaces with complex morphologies.…”

“…The method is compatible with the co-immobilization of several biomolecules (e.g., DSDH and diaphorase [259] or glucose dehydrogenase and diaphorase [260]) and has been used so far for the entrapment of various other enzymes such as lipase [253], laccase [261], polyol dehydrogenases [262], or membrane-bounded (S)-mandelate dehydrogenase [163]. The biopolymer chitosan has been also used as stabilizer [261,263] and the coencapsulation of gold nanoparticles contributed to further enhancement of the bioelectrode response [260,261,264], thanks to the preservation of encapsulated enzymes in silicate composite films with additives (polymers, smart nanomaterials) as well as their contribution to ensure porosity for reactants [251,265]. Finally, one has to mention alternative electrodeposition methods, such as the generation of free standing silica-based biocomposite films by electrochemically induced ion transfer at liquid/liquid interfaces [266] or with the help of an electrode/organic-phase/aqueous-electrolyte three-phase junction [267].…”

“…In addition to biocompatibility, another interest of silica-based sol-gel materials for bioelectrochemistry purposes is the ease of chemical modification, either by physical entrapment of various electroactive and/or catalytic reagents and additives or via covalent grafting thanks to a rich organosilane chemistry, which has been largely exploited in the field of electrochemical biosensors [251,269].…”

Theory of artificial-neural-network-based simultaneous optical sensing of two analytes using sculptured thin films

“…8,9 Several different characteristics of biosensors that can be improved are selectivity, reproducibility, stability, sensitivity, linearity, response time, precision, accuracy, working lifetime, throughput, cost, and portability. 2,10,11 Point-of-care testing is considered to be the crowning achievement in medical testing. 12,13 The blood-glucose test for diabetic patients exemplifies this best.…”