Multifunctional MOF-based Electrochemiluminescent Nanocubes for an Ultrasensitive Biosensing Strategy of B. Pseudomallei Determination Coupled With 3D Magnetic Walking Nanomachine

Burkholderia pseudomallei (B. pseudomallei) can cause melioidosis that is usually fatal. A reliable and rapid detection method is greatly needed for disease surveillance and diagnosis. Herein, an ultrasensitive electrochemiluminescence (ECL) biosensor was constructed for accurate determination of B. pseudomallei coupled with multifunctional Au@Co-MOF@ABEI nanocubes and 3D magnetic walking nanomachine. The synthesized nanocubes could not only immobilize enormous ABEI but exhibit superior peroxidase-like activity to decompose H2O2 to produce plentiful reactive oxygen species (ROSs) that could further react with ABEI, so that the enhanced ECL signals were achieved. Meanwhile, the target-activated walking nanomachine was efficiently driven by Exonuclease III (Exo III) for further improving the sensitivity of the biosensor. As a result, the fabricated ECL biosensor could detect pathogenic gene down to 60.3 aM with a linear range from 100.0 aM to 100.0 pM. Moreover, the biosensing platform successfully achieved the determination of B. pseudomallei down to 9.0 CFU mL−1 in serum samples. This work exhibited an ultrasensitive and specific performance for B. pseudomallei detection, which would become a versatile tool in the early diagnosis and treatment of melioidosis.

Highly Sensitive and Selective Copper (II)-Catalyzed Dual-DNAzyme Colorimetric Biosensor Based on Exonuclease III-Mediated Cyclical Assembly

“Cu-DNAzyme” and “G4-DNAzyme” were used to develop a “turn-off” dual-DNAzyme colorimetric biosensor, which could be used to detect Cu2+ by employing exonuclease III-mediated cyclical assembly (EMCA). EMCA was based on the cleavage activity of Cu2+ to transfer the linkage sequences of the substrate strand and enzyme strand into the transition sequence. The horseradish peroxidase (HRP)-mimicking activity of the G4-DNAzyme was lost after binding with the complementary transition sequence and was hydrolyzed by Exo III. These results demonstrate that the proposed colorimetric biosensor was an effective method for ultradetection of trace metals in a high original signal background. Due to the high sensitivity of the biosensor, the limit of detection (LOD) of Cu2+ is 0.16 nM. This design offers a general purpose platform that could be applied for the detection of any metal ion target through adjustment of metal-dependent DNA-cleaving DNAzymes, which is of great significance for the rapid determination of food safety.

A Novel Colorimetric Nano Aptasensor for Ultrasensitive Detection of Aflatoxin B1 Based on the Exonuclease III-Assisted Signal Amplification Approach

The detection of aflatoxin B1 (AFB1) has recently garnered much attention on the issue of food safety. In this study, a novel and sensitive aptasensor towards AFB1 is proposed using an Exonuclease III (Exo III)-integrated signal amplification strategy. This reported sensing strategy is regulated by aptamer-functionalized nanobeads that can target AFB1; furthermore, complementary DNA (cDNA) strands can lock the immobilized aptamer strands, preventing the signal amplification function of Exo III in the absence of AFB1. The presence of AFB1 triggers the displacement of cDNA, which will then activate the Exo III-integrated signal amplification procedure, resulting in the generation of a guanine (G)-rich sequence to form a G-4/hemin DNAzyme, which can catalyze the substrate of ABTS to produce a green color. Using this method, a practical detection limit of 0.0032 ng/mL and a dynamic range of detection from 0.0032 to 50 ng/mL were obtained. Additionally, the practical application of the established sensing method for AFB1 in complex matrices was demonstrated through recovery experiments. The recovery rate and relative standard deviations (RSD) in three kinds of cereal samples ranged from 93.83% to 111.58%, and 0.82% to 7.20%, respectively, which were comparable with or better than previously reported methods.