3rd generation lab-made biosensors based on carbon nanomaterials produced in water-phase

The use of dehydrogenase enzymes in electrocatalysis and electroanalysis has led to the development of effective biofuel cells and biosensors with useful features and competitive performances. One of the most fascinating features of some dehydrogenases is their ability to directly communicate with specific transducing surfaces, allowing direct electron transfer (DET) from specific enzymatic sites, with no use for redox mediators. Herein, the Fructose Dehydrogenase (FDH) ability to give DET has been studied towards different 0D, 1D, and 2D carbonaceous NMs (C-NMs) prepared in water-phase avoiding the use of solvents. Different nanostructures, i.e., carbon black (CB) from industrial waste, carbon nanofibers (NF) from eucalyptus scraps, mesoporous carbon (MS), and graphene nanoplates (GF) have been successfully nano-dispersed in water using liquid-phase exfoliation (LPE), using sodium cholate as bio-stabilizing agent. The water-dispersed C-NMs have been employed as electrode modifiers of lab-made electrodes fabricated by a stencil-printing approach enabling the production of electrodes in series in an inexpensive, simple, rapid, and reproducible way by using office-grade substrates (i.e., polymeric sheets) and instruments (i.e., cruft-cutting plotter). Initially, the C-NMs features were carefully studied electrochemically and in parallel, their ability to give DET with FDH has been investigated. All the materials resulted able to give DET, the more performing were CB and MS, for this reason, they were selected to construct biosensors for fructose (FRU) determination. CB and MS dose-response curves have been investigated in presence of increasing amounts of FRU, ranging from 1 μM to 50 mM, via chronoamperometry (+0.25 V) highlighting similar performances (CB-FDH: LOD = 0.35 μM; MS-FDH: LOD = 0.17 μM). Both biosensors exhibited good reproducibility (RSD ≤ 4%, n = 3) and repeatability (RSD ≤ 4%, n = 10). Finally, MS-FDH and CB-FDH biosensors were challenged for the selective FRU determination in honey, food beverage and urine samples achieving good recoveries (CB: 116%-95%, RSD < 9%, n= 3; MS: 105%-96%, RSD < 8%, n= 3); biosensor selectivity was successfully proved against several potential interfering species. This work opens new gates for the development of 3rd generation biosensors based on carbon materials (including from renewable sources) produced without the use of solvents for challenging analytical applications. Further, here was demonstrated how lab-made sensors can be performing more than commercial ones, offering captivating opportunities for the fabrication of tailored devices using within everyone's reach technologies.