Functionalizable poly-terthiophene/Cu2O heterojunction constructed in situ for sensitive photoelectrochemical detection of long non-coding RNA markers†

Abstract

A photoelectrochemical (PEC) sensor based on the poly-2,2,5,2-terthiophene (pTTh)/Cu₂O heterojunction was constructed and applied for the detection of long non-coding RNA (lncRNA) TROJAN, a biomarker of triple-negative breast cancer. Cu₂O and pTTh were electrodeposited in situ and sequentially onto an indium tin oxide substrate. The bandgap of the resultant type II heterojunction was measured spectroscopically and the morphology was found to effectively separate photogenerated holes from electrons. A photocurrent density as high as 250 μA cm⁻² was attained, which is about three times higher than those of only pTTh or Cu₂O. Owing to the close contact between pTTh and Cu₂O, this PEC sensor is highly stable. Oligonucleotide probes for lncRNA can be cross-linked to carboxyl moieties of mercaptopropionic acid molecules adsorbed on pTTh/Cu₂O. The desirable band structure and the high density of probe molecules collectively yielded a linear range of 0.1–10 000 pM. Our PEC sensor has been demonstrated to be amenable for detection of lncRNA markers with excellent analytical performance.