Plataforma Portátil de Detecção de MicroRNA Salivar Associado ao Câncer de Mama Utilizando Leitura Eletroquímica via Smartphone

Abstract

This work reports the development of a portable electrochemical biosensor for the selective detection of salivary miR-200a, a key microRNA biomarker associated with breast cancer progression and epithelial–mesenchymal transition. The sensing platform was constructed using a screen-printed carbon electrode (SPCE) modified with an electropolymerized poly-PABA film, which provides a stable and functional interface enriched with carboxyl and amine groups for efficient probe immobilization while limiting nonspecific adsorption. A specific miR-200a oligonucleotide probe was immobilized onto the poly-PABA layer, and hybridization events were monitored through indirect electrochemical detection using ninhydrin as an electroactive indicator. The biosensor exhibited excellent analytical performance, including a wide linear response range, low limit of detection, good reproducibility, and operational stability for up to 30 days under refrigerated storage. Surface characterization by atomic force microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy confirmed successful electrode functionalization and pronounced morphological changes following specific probe–target hybridization. High selectivity was demonstrated, as the complementary miR-200a target produced a significantly higher electrochemical response compared to non-complementary miRNA sequences and viral RNA (HCV), confirming minimal interference in complex 155 SERVIÇOPÚBLICOFEDERAL UNIVERSIDADEFEDERALDEUBERLÂNDIA INSTITUTO DEBIOTECNOLOGIA PROGRAMADEPÓS-GRADUAÇÃOEMGENÉTICAE BIOQUÍMICA biological matrices. Clinical validation using human saliva samples enabled clear discrimination between healthy individuals, patients with benign breast disease, breast cancer, and triple-negative breast cancer. Receiver operating characteristic (ROC) analysis yielded areas under the curve of 1.0 across all comparisons, indicating outstanding diagnostic accuracy. The integration of smartphone assisted electrochemical readout further enhances the portability and accessibility of the platform. Overall, this biosensor represents a promising non-invasive, low cost, and point-of-care diagnostic approach for breast cancer screening and molecular stratification.