Nanomaterial-based electrochemical sensing strategies for cell lines oxidative stress evaluation and for bio-compounds detection in food

In this work, different electrochemical sensors based on nanomaterials aimed to assess cell oxidative stress and bioactive compounds in food are proposed. The realization of these sensors represents the first step, in the development of an integrated lab-on-chip microfluidic platform able to study the antioxidant protection action of food components towards oxidative stressors, to be applied in cell cultures. Carbon Black (CB) - Prussian Blue (PB) based electrodes for H2O2 sensing in Parkinson’s disease in vitro model were developed together with a transition metal dichalcogenides (TMDs) based hybrid sensor for class-selective evaluation of polyphenols. Among, different analytical strategies, electrochemical sensors are very appealing for their simplicity, speed, sensitivity, miniaturization, and cost-effectiveness. Indeed, nanostructured sensors allow improving the sensitivity and selectivity providing larger surface area and faster electron transfers in comparison with their bulk counterparts. Direct sensing of H2O2 in classical metal electrodes such as platinum or gold is possible, however, it suffers from poor selectivity due to the high overpotentials needed. The selection of a proper nanomaterial and catalyst can overcome this drawback. Thus, because of the nanomaterial feature of the CB and the catalytic activity of the PB, towards the H2O2 reduction, good analytical performances (linear range 0.2 and 1000 μM, LOD 0.01 μM) have been obtained allowing selective H2O2 detection, at very low potentials (-0.05 V) in neuroblastoma SH-SY5Y cell line. For the evaluation of the bioactive compounds in food, a new hybrid nanomaterial based on CB and molybdenum disulfide (MoS2) has been employed. In this case, the CB was hybridized with the MoS2, that is a transition metal dichalcogenide (TMD). The TMDs possess a layered structure, that could be easily processed to form a 2D 'graphene-like' nano-structure, using liquid phase exfoliation in appropriate solvents. However, TMDs properties have not yet been widely and deeply studied for (bio)sensing purposes. In the proposed sensor, the CB-MoS2 combination exhibited an improved electroanalytical (improved charge-transfer ability low charge-transfer resistance high electrical conductivity and enhanced electrocatalysis) and analytical (high sensitivity, and low fouling) performances, in comparison with sensors realized with the individual nanomaterials (CB and MoS2 alone). Moreover, an exceptional ability to assess o-diphenols and catechins has been proved, and the electrode fouling, a typical drawback with these compounds in electrochemical analysis, was negligible. These features have been successfully exploited for the determination of polyphenols in olive oil and chocolate samples. In both applications, the nanomaterial ability to support the analysis of bio-compounds in biological and food samples have been demonstrated. Furthermore, the basis for the realization of an integrated device, able to evaluate the antioxidant protection action of food components towards oxidative stressors, have been laid.