PANI/MXene quantum dot-based nanohybrids as a host matrix for the detection of guanosine

The sensitive and selective detection of nucleoside biomarkers is crucial for the early diagnosis and monitoring of various physiological and pathological conditions. In this work, polyaniline (PANI)/MXene quantum dot (MQD) nanohybrids were developed as an electrochemical sensing platform for the detection of the biomarker guanosine. MQDs synthesized via a top-down approach exhibited a quasi-spherical morphology with an average size of ∼3.19 nm, with characteristic optical absorption features. Structural and compositional analyses using XRD, FTIR, and XPS indicate the formation of the PANI/MQD/CFP composite. Electrochemical studies reveal that the PANI/MQD/CFP-modified electrode exhibits enhanced charge-transfer kinetics, evidenced by a significant reduction in charge-transfer resistance (739.6 to 209.4 Ω) and a lower oxidation potential for guanosine (0.99 V) compared to control electrodes. The sensing mechanism follows an adsorption-controlled, proton-coupled two-electron oxidation process. The sensor demonstrates a linear detection range of 0.18-40 µM and a limit of detection of 6.07 nM. The improved performance is attributed to the synergistic effect of the high surface reactivity offered by the MXene Quantum Dots (MQDs) and the efficient charge transport facilitated by the PANI network. The sensor also exhibits good reproducibility, stability, and applicability in pharmaceutical sample analysis, indicating its potential for practical electrochemical sensing applications.