Terminal deoxynucleotidyl transferase-induced DNAzyme nanowire sensor for colorimetric detection of lipopolysaccharides

摘要

Highlights•A label-free amplification colorimetric sensor for the detection of LPS was reported.•The autonomous assembly of HCR nanowire amplifies signal dozens of times.•TDT induced HRP-mimicking DNAzyme provides the colorimetric readout signals.•The proposed method is cost- effective, sensitive and applicable in biological samples.•The LOD is 100pg/mL，and the semi-LOD was 20ng/mL by the naked eye.AbstractA new colorimetric DNAzyme nanowire sensor has been developed for the sensitive and selective quantification of lipopolysaccharides (LPS). The sensor was a label-free and isotheral reaction system based on a LPS-binding aptamer and autonomously assembled DNAzyme nanowire. In the sensing system, an aptamer-initiator (AI) was designed to recognize the LPS and initiated the hybridization chain reaction (HCR) of two DNA hairpins (H1and H2). All the H2containing sticky ends formed terminal deoxynucleotidyl transferase (TdT) −induced G-quadruplexes. In the presence of LPS, on end of AI, and LPS-aptamer, formed the LPS/aptamer complex with the remaining LPS, the other end of AI, the initiator then started the alternate-opening of H1and H2through HCR. Furthermore, TdT-induced hemin/G-quadruplex DNAzymes along DNA nanowires were self-assembled after HCR process. As a result, the solution in light yellow was observed via the addition of H2O2/TMB. After optimization, the time to detect the signal was approximately 40min, and the reaction temperature was in a broad range from 4°C to 37°C. The detection platform showed excellent sensitivity and selectivity for LPS fromE. coliO111:B4 in a series of samples. In less than 2h, a colorimetric response was achieved and the concentrations of LPS detected could be as low as 100pg/mL. The semi-quantitative observation limit was 20ng/mL with the naked eye. A drinking water sample was tested, which further demonstrated the feasibility of the proposed method applied for biological samples.