Portable single-step ethanolamine-functionalized boron-doped diamond immunosensor for dual detection of CEA and CYFRA 21-1.

A single-step ethanolamine-functionalized boron-doped diamond (BDD) immunosensor for the dual detection of carcinoembryonic antigen (CEA) and cytokeratin fragment 21-1 (CYFRA 21-1). Unlike conventional multi-step carbodiimide-based coupling strategies, the ethanolamine (ETA) modification provides a simplified amine-terminated surface for efficient antibody immobilization. Comprehensive characterization confirmed successful layer-by-layer assembly: scanning electron microscopy (SEM) revealed surface morphological evolution, while X-ray photoelectron spectroscopy (XPS), Contact angle measurements and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) verified amine group integration and biomarker attachment. The platform showed concentration-dependent current responses across the range of 0.001-400 ng/mL and achieved statistically calculated limits of detection of 0.085 pg/mL for CEA and 0.043 pg/mL for CYFRA 21-1. The sensor exhibited good selectivity, reproducibility, stability, and reliable performance in spiked human serum samples with minimal matrix interference. In addition, an Arduino-based portable readout closely matched bench-top measurements, supporting the potential of the platform for point-of-care lung cancer screening.