Sensitive "capillary ELISA" via vapor-phase surface modification

Sensitive ELISA for C-reactive protein (CRP) was performed in a capillary tube based on simple vapor-phase surface chemistry. Amine surfaces were produced in capillary tubes in two different methods using 3-aminopropyltriethoxysilane (APTES) in liquid and vapor phases. Those amine surfaces were tethered with gold nanoparticles (AuNPs) to be characterized by field emission scanning electron microscopy (FE-SEM) resulting in more dense and dispersed AuNP populations from the vapor-phase surface. Feasibility of a miniaturized home-made optical detector for "capillary ELISA" was performed by infusing into capillary tubes the colored solutions that had just gone through ELISA on a 96-well plate. The compatibility of the two results obtained from ELISAs on a well-plate and in capillary tubes, confirmed dependability of the miniaturized detector. Finally "capillary ELISA" was performed on the home-made detector using anti-CRP immobilized capillary tubes that had been prepared via vapor-phase surface treatment, resulting in detectability of 1.0 ng/mL of CRP, which turned out to be around 10 times higher in sensitivity than that of the well-plate ELISA.