Label- and- enzyme free electrochemical DNA biosensor for ultrasensitive detection of breast cancer prognostic marker ESR1.

Breast cancer is a complex heterogeneous disease that continues to impose a substantial global burden on women's health. Analysis of ESR1 gene expression using non-invasive liquid biopsy has significant prognostic value, serving as an indicator of poor prognosis and overall survival (OS) in patients with ER+/HER-2- (Estrogen Receptor+/Human Epidermal Growth Factor Receptor-2-) breast cancer. This underscores the need for a reliable detection method for disease monitoring. However, existing detection approaches struggle to simultaneously provide simplicity, rapid analysis, high accuracy, and cost-effectiveness, highlighting the need for DNA biosensors. UV laser induced graphene (UV-LIG) electrodes were produced by laser scribing of polyimide sheets subjected to UV-ozone treatment, providing a hydrophilic, activated surface that enhances cationic PLL adsorption. The successful fabrication of the UV-LIG-based DNA biosensor was confirmed by SEM, TEM, and XPS analyses. Under optimized conditions, chronoamperometric measurements exhibited a well-defined linear relationship between current density response and the logarithm of ESR1 target concentration over a range of 10 aM to 1 nM, with a detection limit of 2.5 aM and a quantification limit of 8.3 aM, without requiring any labeling procedures. The biosensor also demonstrated satisfactory performance in serum-based analysis, confirming its robustness against matrix interferences. Furthermore, it exhibited excellent selectivity for discriminating single-nucleotide mismatches.