RESUMO
Citrus Huanglongbing (HLB) is known as the cancer of citrus, where Candidatus Liberibacter asiaticus (CLas) is the most prevalent strain causing HLB. In this study, we report a novel electrochemiluminescence (ECL) biosensor for the highly sensitive detection of the CLas outer membrane protein (Omp) gene by coupling rolling circle amplification (RCA) with a CRISPR/Cas12a-responsive smart DNA hydrogel. In the presence of the target, a large number of amplicons are generated through RCA. The amplicons activate the trans-cleavage activity of CRISPR/Cas12a through hybridizing with crRNA, triggering the response of smart DNA hydrogel to release the encapsulated AuAg nanoclusters (AuAg NCs) on the electrode and therefore leading to a decreased ECL signal. The ECL intensity change (I0 - I) is positively correlated with the concentration of the target in the range 50 fM to 5 nM, with a limit of detection of 40 fM. The performance of the sensor has also been evaluated with 10 samples of live citrus leaves (five HLB negative and five HLB positive), and the result is in excellent agreement with the gold standard qPCR result. The sensing strategy has expanded the ECL versatility for detecting varying levels of dsDNA or ssDNA in plants with high sensitivity.
Assuntos
Proteínas da Membrana Bacteriana Externa , Citrus , Técnicas Eletroquímicas , Medições Luminescentes , Técnicas Eletroquímicas/métodos , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/química , Citrus/microbiologia , Citrus/química , Hidrogéis/química , Técnicas Biossensoriais/métodos , DNA/química , DNA/genética , Sistemas CRISPR-Cas/genética , Liberibacter/genética , Liberibacter/química , Técnicas de Amplificação de Ácido Nucleico , Doenças das Plantas/microbiologia , Ouro/química , Nanopartículas Metálicas/química , Limite de DetecçãoRESUMO
We report an electrochemiluminescence (ECL) sensor for Salmonella detection based on allosteric probe as a bio-recognition element and CRISPR/Cas12a as a signal amplification strategy. In the presence of Salmonella, the structure switching occurs on allosteric probes, resulting in their hybridization with primers to trigger isothermal amplification. Salmonella is then released to initiate the next reaction cycle accompanying by generating a large amount of dsDNA, which are subsequently recognized by CRISPR-gRNA for activating the trans-cleavage activity of Cas12a. Furthermore, the activated Cas12a can indiscriminately cut the ssDNA which is bound to the electrode, enabling the release of the ECL emitter porphyrinic Zr metal - organic framework (MOF, PCN-224) and exhibiting a decreased ECL signal accordingly. The linear range is 50 CFU·mL-1-5 × 106 CFU·mL-1 and the detection limit is calculated to be 37 CFU·mL-1. This method sensitively detects Salmonella in different types of real samples, indicating it is a promising strategy for Salmonella detection.
