**A Non-Enzyme and Non-Label Sensitive Fluorescent Aptasensor Based on Simulation-Assisted and Target-Triggered Hairpin Probe Self-Assembly for Ochratoxin a Detection**

### **Mengyao Qian <sup>1</sup> , Wenxiao Hu <sup>2</sup> , Luhui Wang <sup>2</sup> , Yue Wang <sup>1</sup> and Yafei Dong 2,3,\***


Received: 10 May 2020; Accepted: 4 June 2020; Published: 6 June 2020

**Abstract:** The monitoring and control of mycotoxins has caused widespread concern due to their adverse effects on human health. In this research, a simple, sensitive and non-label fluorescent aptasensor has been reported for mycotoxin ochratoxin A (OTA) detection based on high selectivity of aptamers and amplification of non-enzyme hybridization chain reaction (HCR). After the introduction of OTA, the aptamer portion of hairpin probe H1 will combine with OTA to form OTA-aptamer complexes. Subsequently, the remainder of the opened H1 will act as an initiator for the HCR between the two hairpin probes, causing H1 and H2 to be sequentially opened and assembled into continuous DNA duplexes embedded with numerous G-quadruplexes, leading to a significant enhancement in fluorescence signal after binding with N-methyl-mesoporphyrin IX (NMM). The proposed sensing strategy can detect OTA with concentration as low as 4.9 pM. Besides, satisfactory results have also been obtained in the tests of actual samples. More importantly, the thermodynamic properties of nucleic acid chains in the monitoring platform were analyzed and the reaction processes and conditions were simulated before carrying out biological experiments, which theoretically proved the feasibility and simplified subsequent experimental operations. Therefore, the proposed method possess a certain application value in terms of monitoring mycotoxins in food samples and improving the quality control of food security.

**Keywords:** ochratoxin A; fluorescence; G-quadruplex; biosensor; computation; simulation

**Key Contribution:** A fast, sensitive and non-label fluorescence aptasensor for ochratoxin A detection based on computer simulation, G-quadruplex formation and signal amplification of hybrid chain reaction is reported.
