This research developed a magnetic relaxation switching (MRS) biosensor based on hydrogel sol-gel transition and the CRISPR/Cas12a system (MRS-CRISPR) to detect Salmonella. Herein, the alkaline phosphatase (ALP) labeled with streptavidin was captured by the biotin-modified DNA on magnetic nanoparticles (MNPs) surface, which generated an acidic environment via enzymatic reaction to release Ca²⁺ and induced the transformation of alginate sol to hydrogels. In contrast, Salmonella activated the trans-cleavage activity of the CRISPR/Cas12a system, interrupting the capture of ALP and the subsequent sol-gel transition. Then, transverse relaxation time (T₂), which was regulated by the hydrogelation process was measured for Salmonella detection. The MRS-CRISPR biosensor enables sensitive detection of Salmonella with a detection limit of 158 CFU/mL. It directly alters the state of water molecules, overcoming the disadvantages of traditional MRS sensors that rely on MNPs to produce T₂ signals indirectly. This method offers innovative insights for the application of the MRS technology in food safety analysis.

中文翻译：

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基于 CRISPR/Cas12a 的直接横向弛豫时间生物传感器，通过水凝胶溶胶-凝胶转变进行沙门氏菌检测


本研究开发了一种基于水凝胶溶胶-凝胶转变的磁弛豫开关 （MRS） 生物传感器和 CRISPR/Cas12a 系统 （MRS-CRISPR） 来检测沙门氏菌。在此，用链霉亲和素标记的碱性磷酸酶 （ALP） 被磁性纳米颗粒 （MNP） 表面的生物素修饰的 DNA 捕获，通过酶促反应产生酸性环境，释放 Ca²⁺，并诱导海藻酸盐溶胶转化为水凝胶。相反，沙门氏菌激活了 CRISPR/Cas12a 系统的反式切割活性，中断了 ALP 的捕获和随后的溶胶-凝胶转换。然后，测量受水凝胶化过程调节的横向弛豫时间 （T₂） 用于沙门氏菌检测。MRS-CRISPR 生物传感器能够灵敏地检测沙门氏菌，检测限为 158 CFU/mL。它直接改变了水分子的状态，克服了传统 MRS 传感器依赖 MNP 间接产生 T₂ 信号的缺点。该方法为 MRS 技术在食品安全分析中的应用提供了创新的见解。