Synergistic Effects of Hydrophobicity and Negative Charge on the Nanopore Surface for the Dual-Amplified Iontronic Detection of MicroRNA.

Tailoring the surface charge has emerged as a promising method for developing target-responsive iontronic sensors. However, the single anionic effect cannot satisfy the needs of highly sensitive iontronic sensing for the detection of low-abundance microRNAs (miRNAs). Here, the synergistic interplay between hydrophobicity and negative charge on the nanopore surface was proposed for the dual-amplified iontronic detection of miRNA-34a. When miRNA-34a was introduced, the chain hybridization reaction (CHR) was initiated on the outer surface of anodic aluminum oxide (AAO) nanopores, exposing a G-rich tail, which promotes the growth of negatively charged guanine nanowire (G-wire) with the assistance of magnesium ions and free fragments. The surface charge density of AAO was increased by ∼260% after CHR-cascaded G-wire amplification. Furthermore, the application of hydrophobic modifications leads to a notable reduction in the effective diameter of the nanopores, which also increases the current intensity. This iontronic sensor achieved ultrasensitive detection of miRNA-34a from 0.1 fM to 10 pM with a low detection limit of 0.03 fM. Moreover, it exhibited excellent selectivity and practicability for detecting miRNA-34a in both serum samples of patients with liver cancer and cancer cells. This iontronic sensing system has potential applications in the field of biomedical research and helps in the diagnosis of diseases.