Abstract: The present document describes a dual-affinity probe comprising an inorganic surface binding peptide and a target-specific capture element, which may bind to various targets, such as pathogens. This document further describes uses of the dual-affinity probe, e.g., to determine the presence of and/or quantity of a target in a sample. In particular embodiments, the dual-affinity probe is specific for SARS-CoV-2 (Spike or Nucleocapsid) protein and may be used to determine whether a subject is infected with SARS-CoV-2.