CRP and COVID-19: This detection system consists of four working graphene electrodes, an Ag/AgCl reference electrode, and a graphene counter electrode, patterned on polyimide substrate via CO2 laser engraving and functionalized with proper receptors, enabling simultaneous quantification of different biomarkers regarding COVID-19 (e.g., nucleocapsid protein, anti-spike protein IgG and IgM, and C-reactive protein) through sandwich- and indirect-based immunosensing strategies, either with patient serum or saliva sample.