A fluorescence imaging-supported aptasensor for sensitive monitoring of cadmium pollutant in diverse samples: A critical role of metal organic frameworks.

Water pollution, as the remarkable environmental remediation issue, is a today worldwide concern. Cadmium ion (Cd2+) as a hazardous water pollutant is seriously detrimental to human health, food safety, and ecological areas. Hence, we successfully designed a simple detection array for monitoring of ultra-low levels of Cd2+ ion by combining the advantages of aptamer as a high sensitive and selective sensing probe and zeolitic imidazolate framework-8 (ZIF-8) as a superior fluorescence quenching inducer. To have a portable and on-site detection assay, the aptamer biosensing array (aptasensor) was designed by using a paper-supported substrate. The basis of the designed paper-supported aptasensor was the specific complexation of Cd2+ with the aptamer strand, adsorption of fluorescein-labeled complementary (FAM-CP) strand on the ZIF-8 surface, and fluorescence quenching of FAM molecule after the leakage of the injected target solution on the sample zone of the paper substrate to the detection part. A linear relationship was obtained between the Mean Gray Value index, as a criterion for the fluorescence quenching, and the Cd2+ concentration in the range of 0.1-120 pM with a detection limit of 0.076 pM. The aptasensor could detect Cd2+ in the diverse real sample, including tap water, milk, coffee, and human blood serum.

Metal organic frameworks as advanced functional materials for aptasensor design.

BACKGROUND: Advancement in coordination chemistry has achieved an impressive development of metal organic frameworks (MOFs) as the supramolecular hybrid materials, comprising harmonized metal nodes with organic ligands. Scope and approach: MOFs offer the unique properties of easy synthesis, nanoscale structure, adjustable size and morphology, high porosity, large surface area, supreme chemical tunability and stability, and biocompatibility. The features provide an exceptional opportunity for the widely usage of MOFs in the different scientific fields, e.g. biomedicine, electrocatalysis, food safety, energy storage, environmental surveillance, and biosensing platforms. The synergistic incorporation of the aptamer advantages and the superiorities of MOFs attains the novel MOF-based aptasensors. The excellent selectivity and sensitivity of the MOF-based aptasensors nominate them as efficient lab-on-chip tools for cost-effective, label-free, portable, and real-time monitoring of diverse targets. KEY FINDINGS AND CONCLUSIONS: Here, we review the achievements in the sensor design by cooperation of MOF motifs and aptamers with the conspicuous potential of determining the targets. Finally, some results are expressed that provide a valuable viewpoint for developing the novel MOF-based test strips in the future.

A simple and ultrasensitive metal-organic framework-based aptasensor for fluorescence detection of ethanolamine.

In this research, a facile fluorescence aptasensor was designed for the ultrasensitive determination of ethanolamine (ETA) as an aliphatic amino alcohol molecule with harmful side effects for human health. Zeolitic imidazolate framework-8 (ZIF-8) as an efficient metal-organic framework was applied to quench the fluorescence emission of the FAM-labeled ETA aptamer. The presence of ETA could recover the fluorescence response under the optimal experimental conditions. ETA could be sensitively detected by the designed aptasensor in the linear concentration range of 0.1 nM-20 µM with the detection limit of 14.38 pM. The designed aptasensor was utilized to determine ETA in milk and serum samples with the detection limits of 17.86 and 15.21 pM, respectively. The aptasensor with the remarkable features of high sensitivity, simplicity and feasibility holds the supreme potential to construct a low-cost portable sensing method for food safety control, human diagnostics, and environmental monitoring with coupling to the microfluidic paper-based devices.