Synergistic MIP-aptamer dual-recognition on silver-decorated sulfur-doped graphene quantum dots (S-GQDs@Ag) nanohybrids for ultra-sensitive impedimetric carcinoembryonic antigen detection

The clinical utility of Carcinoembryonic Antigen (CEA) as a cornerstone biomarker for oncological monitoring is frequently hindered by the limitations of traditional immunoassays, including high costs, specialized storage requirements, and complex procedural workflows. To address these challenges, we report the development of a high-performance electrochemical paper-PVC hybrid sensor utilizing a novel dual-recognition nanohybrid interface. The impedance-based sensing platform was engineered by integrating molecularly imprinted polymers (MIPs) and specific aptamers (Apt) onto a signal-amplifying scaffold of silver-decorated sulfur-doped graphene quantum dots (S-GQDs@Ag). This S-GQDs@Ag nanohybrid provides an exceptional surface-to-volume ratio and superior conductivity, facilitating rapid electron transfer and enhancing sensitivity. The dual-recognition framework was constructed via sol-gel polymerization, where aptamers were co-embedded within the MIP matrix to create biomimetic cavities with synergistic spatial and chemical affinity for CEA. Comprehensive physicochemical characterization via ultraviolet–visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) confirmed the homogeneous decoration of S-GQDs on silver nanoparticles and their successful encapsulation within the polymeric architecture. Under optimized conditions, the S-GQDs@Ag@MIP-Apt sensor demonstrated an exceptionally wide linear dynamic range of 0.0001 to 250 ng mL⁻¹ with corresponding sensitivities of 694.780 (Ω mL) ng⁻¹ and an ultralow limit of detection (LOD) of 0.035 pg mL⁻¹. The sensor exhibited high selectivity against common interferents, excellent reproducibility, and prolonged environmental stability, maintaining its performance in complex human serum matrices. The MIP-Apt sensor demonstrates high accuracy for CEA determination in serum, yielding satisfactory recoveries between 89.3% and 116.3%. Statistical analysis indicates no significant difference between the sensor's performance and standard clinical assays (t_observed = 0.9926, where t_critical = 2.2009, P = 0.05). Furthermore, the fabricated MIP-Apt sensor demonstrates excellent long-term stability, retaining 89% of its initial signal after 84 days. It also exhibits high reproducibility, with a 4.91 % RSD across ten separate devices). By reconciling the structural durability of MIPs with the high-affinity recognition of aptamers, this modular paper-PVC platform offers a robust, cost-effective, and scalable solution for decentralized, early-stage point-of-care (POC) cancer screening in resource-limited settings.