From Lab to Clinical Application: Establishing a "Gold" Touchstone for Lung Cancer Biomarker-CEA to Advance Diagnostic.

Colloidal gold immunochromatography has emerged as a pivotal platform for point-of-care diagnostics, yet challenges persist in stabilizing nanoparticle-antibody interactions and ensuring batch-to-batch reproducibility. To address these limitations, we engineered a nanogold-affinity peptide probe for the rapid detection of the lung cancer biomarker carcinoembryonic antigen (CEA), leveraging phage-display-derived peptides as biorecognition elements. The probe was synthesized by conjugating CEA-specific affinity peptides to polyethylene glycol (PEG)-functionalized gold nanoparticles (AuNPs) via covalent amide bonding, ensuring precise orientation and enhanced colloidal stability. Systematic optimization of reaction parameters, including the PEGylation time, peptide-to-nanoparticle ratios, and centrifugation conditions, yielded a robust preparation protocol. The resulting immunochromatographic test strip demonstrated a detection limit of 2.5 ng/mL for CEA, surpassing the clinical threshold of 5 ng/mL, and exhibited 91.7% accuracy in clinical serum samples. Notably, the substitution of antibodies with synthetic affinity peptides reduced costs by approximately 8-fold while maintaining high specificity and resistance to nonspecific binding. This work not only advances the integration of biomolecular engineering and nanotechnology for diagnostic applications but also establishes a scalable framework for developing stable, low-cost biosensors targeting macromolecular biomarkers.