Sensitive detection of RNA based on concatenated self-fuelled strand displacement amplification and hairpin-AgNCs

Signal Amplification-Based Biosensors and Application in RNA Tumor Markers

Tumor markers are important substances for assessing cancer development. In recent years, RNA tumor markers have attracted significant attention, and studies have shown that their abnormal expression of post-transcriptional regulatory genes is associated with tumor progression. Therefore, RNA tumor markers are considered as potential targets in clinical diagnosis and prognosis. Many studies show that biosensors have good application prospects in the field of medical diagnosis. The application of biosensors in RNA tumor markers is developing rapidly. These sensors have the advantages of high sensitivity, excellent selectivity, and convenience. However, the detection abundance of RNA tumor markers is low. In order to improve the detection sensitivity, researchers have developed a variety of signal amplification strategies to enhance the detection signal. In this review, after a brief introduction of the sensing principles and designs of different biosensing platforms, we will summarize the latest research progress of electrochemical, photoelectrochemical, and fluorescent biosensors based on signal amplification strategies for detecting RNA tumor markers. This review provides a high sensitivity and good selectivity sensing platform for early-stage cancer research. It provides a new idea for the development of accurate, sensitive, and convenient biological analysis in the future, which can be used for the early diagnosis and monitoring of cancer and contribute to the reduction in the mortality rate.

Rapid and effective detection of Macrobrachium rosenbergii nodavirus using a combination of nucleic acid sequence-based amplification test and immunochromatographic strip

Nucleic acid sequence-based amplification (NASBA) provides a fast and convenient approach for nucleic acid amplification under isothermal conditions, and its combination with an immunoassay-based lateral flow dipstick (LFD) could produce a higher detection efficiency for M. rosenbergii nodavirus isolated from China (MrNV-chin). In this study, two specific primers and a labelled probe of the capsid protein gene of MrNV-chin were constructed. The process of this assay mainly included a single-step amplification at a temperature of 41 ℃ for 90 min, and hybridization with an FITC-labeled probe for 5 min, with the hybridization been required for visual identification during LFD assay. The test results indicated that, the NASBA-LFD assay showed sensitivity for 1.0 fg M. rosenbergii total RNA with MrNV-chin infection, which was 10⁴ times that of the present RT-PCR approach for the detection of MrNV. In addition, no products were created for shrimps with infection of other kinds of either DNA or RNA virus, which indicated that the NASBA-LFD was specific for MrNV. Therefore, the combination of NASBA and LFD is a new alternative detection method for MrNV which is rapid, accurate, sensitive and specific without expensive equipment and specialised personnel. Early detection of this infectious disease among aquatic organisms will help implement efficient therapeutic strategy to prevent its spread, enhance animal health and limit loss of aquatic breeds in the event of an outbreak.

Duplex-specific nuclease and Exo-III enzyme-assisted signal amplification cooperating DNA-templated silver nanoclusters for label-free and sensitive miRNA detection

Development of novel miRNA detection strategies plays a crucial role in fundamental research and clinical diagnosis of various diseases, such as infantile pneumonia. We herein develop a rapid and sensitive DNA-templated AgNCs-based miRNA detection approach, pinning the hope on an improved detection sensitivity in an easy-to-operate way. In the method, a hairpin probe is designed to specifically bind with target miRNA, and to initiate the DSN enzyme and Exo-III-assisted dual signal recycles. The resultant guanine-rich DNA sequences after signal amplification turn on the fluorescence of the dark AgNCs by hybridizing with the DNA template of the dark AgNCs. The generated signals are correlated with the amounts of target miRNA in the sensing system. Through a series of experiments, the established approach exhibits a great dynamic range of more than seven orders of magnitude with a low limit of detection of 245 aM, holding great promises for miRNA-related researches and disease diagnosis.

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Construction of a fluorescence biosensor for ochratoxin A based on magnetic beads and exonuclease III-assisted DNA cycling signal amplification

Specific and sensitive detection of hazardous mycotoxins in agricultural crops is one of the most important goals of food safety. A fluorescence biosensor for sensitive detection of ochratoxin A (OTA) was constructed via magnetic beads and the exonuclease III (Exo III)-assisted trigger DNA circle amplification approach. Exo III-assisted trigger DNA circle amplification can be utilized as an effective strategy for the sensitive detection of OTA. The employment of streptavidin labeled magnetic beads offers a manner for the accumulation and separation of the hairpin signal probe sDNA-FAM in solution. After target specific recognition, the aptamers combined with OTA were released and the remaining block DNA (bDNA) probes captured the signal probes on magnetic bead modified fluorophores. Subsequently, the enzyme digestion reaction leads to the fluorophore free solution. Exo III-assisted DNA circle amplification contributed to the high sensitivity of the presented OTA fluorescence aptasensor. The experimental results demonstrate that the aptasensor is sensitive with the limit of detection as low as 0.28 ng mL^-1 for OTA, which was lower than that of the proposed aptasensors reported by the other literature on fluorescence methods. Additionally, the developed aptasensor with the diverse aptamer sequence shows promising potential applications in food monitoring.