Ce-based metal-organic frameworks and DNAzyme-assisted recycling as dual signal amplifiers for sensitive electrochemical detection of lipopolysaccharide

• AuNPs/Ce-MOFs acted as catalysts to realize enzyme-free signal amplification.
• Zn2+dependent DNAzyme were used, which overcame the shortage of protein enzyme.
• LPS contents were converted into DNA signal report.

In this work, a sensitive electrochemical aptasensor was designed for lipopolysaccharide (LPS) detection based on Ce-based metal-organic frameworks (Ce-MOFs) and Zn2+ dependent DNAzyme-assisted recycling as dual signal amplifiers. Herein, Ce-MOFs were decorated with gold nanoparticles (AuNPs) to obtain AuNPs/Ce-MOFs, and the resultant AuNPs/Ce-MOFs not only acted as nanocarriers to capture -SH terminated hairpin probes 2 (HP2) for acquiring HP2/AuNPs/Ce-MOFs signal probes, but also as catalysts to catalyze the oxidation of ascorbic acid (AA). In the presence of target LPS, report DNA was released from the prepared duplex DNA and then hybridized with hairpin probes 1 (HP1, which were immobilized on the electrode). With the help of Zn2+, report DNA could act as Zn2+ dependent DNAzyme to cleave HP1 circularly. Then a large amount of capture probes were produced on the electrode to combine with HP2/AuNPs/Ce-MOFs signal probes. When the detection solution contained electrochemical substrate of AA, AuNPs/Ce-MOFs could oxide AA to obtain enhanced signal. Under the optimized conditions, this proposed aptasensor for LPS exhibited a low detection limit of 3.3 fg/mL with a wide linear range from 10 fg/mL to 100 ng/mL.