Leuckart Reaction-Assisted Amine-Functionalized Reduced Graphene Oxide as an Electrochemical Immunosensing Platform...

The rapid and sensitive detection of cancer biomarkers is paramount for early oncological diagnostics and therapeutic monitoring. However, traditional graphene functionalization methods often involve a hazardous, multistep process that compromises material integrity. Addressing this critical bottleneck, we present an efficient, one-pot Leuckart reaction strategy to synthesize amine-functionalized reduced graphene oxide as a transformative electrochemical immunosensing screen-printed electrode (SPEs) platform. By availing highly functionalized graphene oxide (GO) from expanded graphite via the modified Tour's method, we achieved an exceptional nitrogen content of 7.6%, enabling a densely populated reactive amine interface for bioconjugation. This nanomaterial exhibits superior electrochemical properties, dramatically reducing the charge-transfer resistance (R_ct) to 3.58 ± 0.55 kΩ, validated through rigorous electrochemical impedance spectroscopy (EIS) testing modeled with a modified Randles circuit. To translate this material into a practical diagnostic tool, we employed a scalable airbrush-spray deposition technique onto a commercial gold screen-printed electrodes. This approach circumvents the inconsistencies of traditional drop-casting, laying the ground for robust covalent immobilization of anti-CEA antibodies via EDC-NHS chemistry. Thus, the resulting label-free immunosensor was meticulously evaluated using electrochemical techniques for detecting carcinoembryonic antigen (CEA), a vital biomarker for colorectal and lung carcinomas. Analytical performance revealed an outstanding sensitivity of 108.42 μA · decade^-1 · cm^-2 with an LOD of 0.00375 ng mL^-1 and an LOQ of 0.00598 ng mL^-1 operating within the broad linear dynamic range from 0.051 to 51.2 ng mL^-1, covering both healthy and pathophysiological states. Moreover, its storage stability demonstrates the statistically significant current response for the period of ~20 days and retains 62.5% of its activity after 50 days. Additionally, the platform demonstrates a scalable and clinically translatable paradigm for next-generation point-of-care (POC) oncological diagnostics and paves the way for varied antigen-based assay upgrades by improving healthcare outcomes globally.