Fig. 1
(A) Screen-printed carbon-based electrodes (SPCs) used in first clinical assessment study. (Left) The WE and CE are made of carbon paste and the RE is made of Au/AuCl, as well as the grey terminal contacts. The shaded blue area corresponds to an insulating dielectric layer (ESL ElectroScience Europe, UK, ESL 4917). Each SPC-based unit measures ~ 1 × 0.4″ (not shown to scale) with a WE having radius 4 mm. (Right) photograph of an actual SPC-based sensor. SPC-based sensors reported here were fabricated at the Universidad del Valle facilities, in Cali, Colombia. (B) (Left) Photograph of laser-induced graphene-based (LIGs) sensor used in the second clinical assessment study. All electrodes are made of LIG, with the RE covered with Au/AuCl, as well as the grey terminal contacts. A transparent polyethylene terephthalate (PET) overlay mask acts as the insulating dielectric layer. Each LIG sensor unit measures ~ 1 × 0.4″ (not shown to scale) with a WE having radius 4 mm. LIG-based sensors reported here were fabricated at the iÓMICAS Research Institute facilities of the Pontificia Universidad Javeriana, in Cali, Colombia. (Right) Scanning electron micrograph image of the LIG surface at 619 × and 4kx magnifications shows highly porous structure. (C) SPC/LIG functionalization for SARS-CoV-2 spike protein detection. From left: bare electrode, para-aminobenzoic acid electrodeposition (PABA) using cyclic voltammetry for SPC and pyrene butyric acid (PBA) drop-casting for LIG, covalent attachment of carboxylic group from surface PABA to SARS-CoV-2 spike protein monoclonal antibody (mAb), passivation of open carboxylic sites on PABA surface with BSA, and ligation of spike proteins from patient’s sample to antibodies.
