Ag NPs@MXene-mediated electrochemical-SERS dual-mode microfluidic array for multiplexed breast cancer-associated miRNAs detection.

Breast cancer-associated miRNAs are promising liquid-biopsy biomarkers, but their low serum abundance, short sequences and matrix interference hinder sensitive and multiplexed detection. Herein, we developed an Ag NPs@MXene-mediated electrochemical-surface-enhanced Raman scattering (EC-SERS) dual-mode microfluidic array for multiplexed miRNA detection. The platform integrates a multichannel chip, an Au NPs@Au capture interface and an Ag NPs@MXene signal unit loaded with methylene blue (MB) and detection probe P2. In the presence of target miRNAs, the signal unit is recruited to the electrode through a capture unit-miRNA-signal unit sandwich assembly, forming a Faraday-cage-type structure. Conductive MXene nanosheets promote electron transfer and enable abundant MB labels to contribute to electrochemical responses, while Ag NPs enhance the SERS signal of MB. The chip enabled parallel detection of miRNA-21, miRNA-155, miRNA-200c and miRNA-375 over 10-16-10-10 M, with EC and SERS LODs of 0.022-0.042 fM and 0.036-0.067 fM, respectively. Specificity, reproducibility, stability and serum recovery tests confirmed reliable performance. Clinical serum analysis distinguished breast cancer patients from healthy controls with an AUC of 1.000, supporting its potential for breast cancer liquid biopsy.