Ultra-sensitive capillary immunosensor combining porous-layer surface modification and biotin-streptavidin nano-complex signal amplification: Application for sensing of procalcitonin in serum.

We propose a promising capillary immunosensor by combining porous-layer surface modification of an open-tubular capillary and streptavidin-biotin-peroxidase nano-complex signal amplification of chemiluminescence read-out. The immunosensor, namely Porous Layer Open Tubular-Signal Amplification (PLOT-SA) sensor, is successfully applied for ultra-sensitive sensing of procalcitonin (PCT) in human serum samples. The results show the PLOT-SA sensor exhibits essential features for PCT determination, including a wide linear detection range of 0.1 pg/mL-100 ng/mL, an extremely low limit-of-quantitation of 0.01 pg/mL, excellent intra-day and inter-day stability and reproducibility with RSDs less than 4.5%. Our study provides a reliable and robust approach for developing capillary sensors that can be used in analysis of complex biologic samples.