Single-step, label-free quantification of antibody in human serum for clinical applications based on localized surface plasmon resonance.

The amount of antibody in blood is an important measure of health status for making critical decisions in clinical practice. Here, we demonstrated a single-step, label-free, molecular diagnostic method based on localized surface plasmon resonance (LSPR) using standard 96-well microtiter plates. We improved the LSPR biosensor so that it can measure antibodies to blood group antigens in human serum with a single-step operation. First, we employed the ampholytic polymeric surface modification technique to present an efficient molecular scaffold on the sensor surface. Second, we selected the combination of an appropriate reference molecule against the antigen and a blocking agent to significantly reduce the variability of signal due to nonspecific responses of the unknown in the sample. Finally, we overcame the analytical difficulty arising from serum and achieved a single-step "wash-free" measurement of the amount of target antibody in human serum. FROM THE CLINICAL EDITOR: In this paper, a novel, single-step, label-free, molecular diagnostic method is discussed for antibody detection based on localized surface plasmon resonance using standard 96-well microtiter plates.