Human serum albumins

Sulfuric acid (95–98%, H₂SO₄), nitric acid (63%, HNO₃), N-Hydroxysuccinimide (NHS), (C₄H₅NO₃), bovine serum albumins (≥ 98%, BSA), human serum albumins (≥ 98%, HSA), potassium hexacyanoferrate (II) (≥ 99%, K₄[Fe(CN)₆]), potassium hexacyanoferrate (III) (≥ 99%, K₃[Fe(CN)₆]), EDA (≥ 99%, C₂H₈N₂), blood plasma (BP) and saliva from human were purchased from Sigma Aldrich (St. Louis, MO, USA). Dulbecco’s phosphate buffer solution (PBS, pH 7.4) without calcium and magnesium chloride and EDC were bought from Thermo Fisher Scientific (Waltham, Massachusetts, USA). Flexible GCF (99.8%) with a thickness of 0.35 mm was purchased from Goodfellow Cambridge (Huntingdon, UK). Recombinant monoclonal SARS-CoV-2 SPike S1 antibody (anti-SARS-CoV-2) from Rabbit monoclonal antibody (MAb), SARS-CoV-2 SP, and SARS-CoV SP were purchased from Sino Biological (UK). Ultrapure water was prepared by a Milli-Q® IX water purification system (Sigma Aldrich). N₂ of high purity (> 99.99%) was provided by SIAD, Bergamo, Italy).

Bovine serum albumins (≥98%, BSA), human serum albumins (≥98%, HSA), potassium hexacyanoferrate (II) (≥99%, K₄[Fe(CN)₆]) and potassium hexacyanoferrate (III) (≥99%, K₃[Fe(CN)₆]), were purchased from Sigma Aldrich (St. Louis, MO, USA). Dulbecco's phosphate-buffer saline (PBS), pH 7.4, without calcium and magnesium chloride, was purchased from Thermo Fisher Scientific (Waltham, Massachusetts, USA). Artificial human saliva for research purposes was purchased from LCTech (Germany). Flexible CC (Sigracet 39 BB, SGL Carbon) was purchased from Fuel Cell store (Germany). Thiol functionalized SARS-CoV-2 spike S1 aptamer (apta-SARS-CoV-2 (seq.name CFA0688T-GQ5-100, 5′- ThiolC6 – aptamer-3′), SARS-CoV-2 SP, and SARS-CoV SP were purchased from Cambio Ltd. (UK). Ultrapure water (resistivity 18 MΩ) was prepared by a Milli-Q® IX water purification system (Sigma Aldrich). Pure nitrogen (N₂, >99.99%) was supplied from SIAD (Bergamo, Italy).