Herein, a universal fluorescent biosensor was developed for detecting Mycobacterium Tuberculosis (MTB) specific insertion sequence IS6110 gene fragment based on Förster resonance energy transfer (FRET) strategy. CdTe quantum dots (QDs), with excellent luminous performance, were used to label single-stranded DNA (ssDNA) as fluorescence donor (QDs-DNA), in which the ssDNA was complementary to the IS6110 gene fragment. A new type of two-dimensional metal-organic framework (Cu-TCPP) was served as an acceptor. The Cu-TCPP exhibited a higher affinity towards ssDNA than double-stranded DNA (dsDNA). In the absence of targets, the fluorescence of QDs-DNA was quenched – due to the π-π stacking interactions between Cu-TCPP and ssDNA. Otherwise, QDs-DNA hybridized with the target to form a double helix and the fluorescence maintained in a target-concentration dependent manner. Excess QDs-DNA would be quenched and produced negligible background signal. The fluorescent sensor possessed a linear range from 0.05 nM to 1.0 nM with a low detection limit of 35 pM. Furthermore, we successfully applied this biosensing system to detect clinical sputum samples. This method displayed high sensitivity, specificity and great potentials in the early diagnosis of Tuberculosis.
Background Tuberculosis (TB) nucleic acid diagnosis urgently requires rapid, amplification-free methods to overcome limitations of quantitative real-time polymerase chain reaction (qPCR), including instrument dependency, prolonged time, and contamination risks from nucleic acid amplification. Results Here, an amplification-free electrochemiluminescence (ECL) biosensor based on peptide-templated gold nanoclusters and the clustered regularly interspaced short palindromic repeats-Cas12a system (CRISPR-Cas12a) has been constructed for the detection of Mycobacterium tuberculosis (MTB)-specific IS6110 sequences. Peptide-templated gold nanoclusters with low background and high ECL response can be used as sensitive signal probes. When CRISPR-Cas12a recognizes the target IS6110 DNA, it exhibits non-specific cleavage activity, repeatedly cleaving ferrocene-labelled DNA. This results in the restoration of ECL signals quenched by ferrocene, thereby achieving signal amplification. There is a linear relationship between the signal and the target concentration range from 10 CFU/mL to 10 4 CFU/mL, with a detection limit of 7 CFU/mL (S/N = 3). Clinical validation ( n = 40) showed strong agreement with qPCR ( κ = 0.90). Significance Critically, this amplification-free strategy eliminates the need for temperature cycling equipment, reduces detection time to 1 h, and completely avoids the risk of amplicon contamination, providing an ideal solution for rapid screening of highly infectious diseases such as TB.
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