Development of vertical flow immunoassay device for C-reactive protein in microgravity
Successful mid-term and long-term space expeditions need on-board diagnostics to monitor health conditions of crew members. Although point-of-care (POC) diagnostic devices are the best option, they need to be modified to operate in microgravity. An all-capillary force vertical flow immunoassay (VFI) was developed to run the assay against gravity, evaluate the multiplexing capabilities, and detect the biomarker C-reactive protein (CRP) from peripheral blood obtained by a wide range of plasma separation kits. The parameters analyzed to optimize the efficiency of the VFI include assay buffer pad, sample volume, assay time, gold nanoparticles (GNPs) stability, and multiplexing capability. The device can measure a volume range of 2 to 10 μL of plasma and can produce a detectable signal in 2.5 minutes. Immobilized detection antibodies were stable on the conjugate pad for a minimum of 1 week. Assay buffer pad material with higher hydrophobicity and smaller pore size had shorter assay time and more intense signal. Finally, the detection of IgM and CRP in a multiplex assay showed no cross-reaction between biomarkers. In conclusion, short assay time, low sample amount, multiplex capabilities, and a powerless set up of the VFI making it an optimal candidate for a POC device for long- and mid-term space missions.