Quantitative Biomarker Profiling using QPLEX

All quantification methods were detailed in our previous study^{21 (link)}. Briefly, the QPLEX^TM kit utilized Quantamatrix’s multiplex diagnostics platform (QMAP; Quantamatrix Inc., Seoul, Republic of Korea)²⁹ . First, human plasma samples (singular) were diluted in diluent buffer and incubated with the coded beads and biotin-conjugated detection antibodies (angiotensin-converting enzyme, ACE, DY929, R&D Systems, Minneapolis, USA; galectin-3 binding protein, LGALS3BP, DY2226, R&D Systems; periostin, POSTN, DY3548B, R&D Systems; Aβ1−40, 014-26923, Wako, Japan). The immunocomplexes were washed twice with washing buffer at a Biotek-510 magnetic wash station (Biotek, VT, USA). Diluted R-phycoerythrin-conjugated streptavidin was added to each well. After three washes, the immunocomplexes were resuspended in 100 μl of washing buffer by tapping and automatically analyzed using the QMAP^TM system. The intra/interassay coefficients of variation and limits of detection were as follows: ACE, intra: 4.9%, inter: 5.1%, 0.22 ng/ml; LGALS3BP, intra: 1.1%, inter: 5.7%, 0.04 ng/ml; POSTN, intra: 9.0%, inter: 6.0%, 0.034 ng/ml; and Aβ1−40, intra: 5.3%, inter: 3.9%, 0.50 pM.