Food-borne illnesses caused by pathogenic bacteria are prominent issues in food safety. Rapid and sensitive detection of pathogenic bacteria is significantly essential for food safety. In this work, an aptamer biosensor (aptasensor) based on aldehyde magnetic beads (Mbs), rolling circle amplification (RCA) and DNA hydrogel was developed for visualized, simple and rapid detection of Escherichia coli O157:H7 (E. coli O157:H7). Firstly, the Mbs@double-stranded DNA (dsDNA) complexes were prepared. In the presence of target, the aptamer combined with E. coli O157:H7, releasing E. coli aptamer-initiator (EA-I). The supernatant collected by magnetic separation and those released primers were hybridized with circular sequence to form padlock probe. Then, RCA reaction was initiated by adding T4 DNA ligase, phi29 DNA polymerase, and deoxynucleotides (dNTPs), while RCA cannot be triggered in the absence of target. Two circular sequences were designed to contain partially complementary bases. After RCA, two long single-stranded DNA (ssDNA) products were generated using those two circular sequences. They hybridized with each other and formed the naked-eye visible DNA hydrogel. The method showed high sensitivity and specificity with a detection limit of 4 × 10³ CFU/mL for E. coli O157:H7 within 1 h, and the detection time could be finished within 30 min. The aptasensor offers many advantages such as high specificity, easy operation, efficient amplification, rapid and visualized readout, which has potential applications in food safety detection

由病原菌引起的食源性疾病是食品安全中的突出问题。快速，灵敏地检测病原细菌对于食品安全至关重要。在这项工作中，开发了一种基于醛磁珠（Mbs），滚环扩增（RCA）和DNA水凝胶的适体生物传感器（aptasensor），用于可视化，简单而快速地检测大肠杆菌O157：H7（E. coli O157：H7 ）。首先，制备了Mbs @双链DNA（dsDNA）复合物。在靶标存在下，适体与大肠杆菌O157：H7结合，释放出大肠杆菌适体引发剂（EA-1）。通过磁分离收集的上清液和释放的引物与环状序列杂交以形成挂锁探针。然后，通过添加T4 DNA连接酶，phi29 DNA聚合酶和脱氧核苷酸（dNTPs）引发RCA反应，而在没有靶标的情况下无法触发RCA。设计两个环状序列以包含部分互补的碱基。在RCA之后，使用这两个环状序列生成了两个长的单链DNA（ssDNA）产物。他们彼此杂交，形成了肉眼可见的DNA水凝胶。该方法显示出高灵敏度和特异性，对大肠杆菌的检出限为4×10 ³ CFU / mLO157：H7在1小时内完成，检测时间可以在30分钟内完成。适体传感器具有许多优点，例如高特异性，易于操作，有效扩增，快速且可视化的读数，在食品安全检测中具有潜在的应用