A DNA tetrahedral nanomaterial-based dual-signal ratiometric electrochemical aptasensor for the detection of ochratoxin A in corn kernel samples.

Ochratoxin A (OTA) is a highly toxic food contaminant and is harmful to human beings. Herein, a ratiometric electrochemical aptasensor based on a DNA tetrahedral nanomaterial (NTH) was developed in combination with the signal tag of a zirconium metal-organic framework (UiO-66) for the detection of OTA. In the sensor, UiO-66 and a [Fe(CN)6]3-/4- electrolyte solution were used as the signal probe and the internal reference probe, respectively. In the presence of OTA, the OTA aptamer was released from the electrode due to the specific binding of OTA. Thus, signal probe P1 labeled-UiO-66 was captured on the electrode surface by hybridization with DNA NTH. Since signal probe P1 labeled-UiO-66 was close to the electrode, it leads to an increased signal current of UiO-66 at +0.9 V. As the conductivity of the modified electrode decreased, the current signal of [Fe(CN)6]3-/4- at +0.2 V also decreased. The proposed ratiometric electrochemical aptasensor could effectively eliminate external environmental influences and could avoid electrochemical background signals. The aptasensor demonstrated high specificity for OTA, and achieved a good linear range of 1 pg mL-1-100 ng mL-1 with a detection limit of 330 fg mL-1. The developed electrochemical aptamer biosensor effectively detected OTA in corn kernel samples, verifying its practical application for the determination of OTA in actual samples.

Amino-functionalized perylenediimide derivative with dual fluorescence emission for the detection of ascorbic acid in vivo and in vitro.

The rapid, sensitive, and selective detection of ascorbic acid (AA) is of significance in medical assays and diagnostics. In this work, a new aminoperylenediimide (APDI) derived ratiometric fluorescent probe based on the specific redox reaction of cobalt oxyhydroxide (CoOOH) and AA was constructed. APDI exhibited dual fluorescence emission peaks at 549 and 596 nm with an excitation wavelength of 494 nm. In the presence of CoOOH, the dual fluorescence could be quenched. The dominant fluorescence quenching mechanism was caused by the inner filter effect. Using the red emission as a reference, the fluorescence intensity ratio (F549 /F596 ) was linearly correlated with the concentration of AA over a range of 0.05 to 1 µM. The limit of detection for AA was found to be 17 nM. Importantly, the probe was successfully used to detect AA in living cells. Therefore, this high sensitivity and selectivity strategy could directly survey the AA levels in real samples.

Homogeneous electrochemical ratiometric biosensor for MircoRNA detection based on UiO-66-NH2 signal probe and waste-free entropy-driven DNA machine.

The construction of efficient methods for highly sensitive and rapid detection of disease markers is essential for the early diagnosis of serious diseases. In this paper, taking advantage of the UiO-66-NH2 signal molecule in combination with a waste-free entropy-driven DNA machine, a novel homogeneous electrochemical ratiometric platform is developed to detect MircoRNA (miRNA). Metal-organic framework materials (UiO-66-NH2 MOF) and ferrocene were utilized as electrochemical signal tags and reference probes, respectively. The target-initiated waste-free three-dimensional (3D) entropy-driven DNA nanomachine is activated in the presence of miRNA, resulting in DNA-labeled-UiO-66-NH2 falling off from the electrode, leading to a decrease in the signal of UiO-66-NH2 at 0.83V. Our strategy can mitigate false positive responses induced by the DNA probes immobilized on electrodes in traditional distance-dependent signal adjustment ratiometric strategies. The proposed ratiometric platform demonstrates superior sensitivity (a detection limit of 9.8 fM), simplified operation, high selectivity, and high repeatability. The ratiometric biosensor is also applied to detect miRNA content in spiked serum samples.