Tunneling of redox enzymes to design nano-probes for monitoring NAD(+) dependent bio-catalytic activity

Ratiometric fluorescence sensing of formaldehyde in food samples based on bifunctional MOF

A new fluorescence strategy was described for ratiometric sensing of formaldehyde (FA) with bifunctional MOF, which acted as a fluorescence reporter as well as biomimetic peroxidase. With the assistance of H₂O₂, NH₂-MIL-101 (Fe) catalyzes the oxidation of non-luminescent substrate o-phenylenediamine (OPD) to produce fluorescent product (oxOPD) with the maximum emission at 570 nm. Besides, intrinsic fluorescence of MOF (λem = 445 nm) was quenched by oxOPD through inner filter effect (IFE). However, FA and OPD reacted to generate Schiff bases, which competitively consumed OPD inhibiting the generation of oxOPD. Under the excitation wavelength of 375 nm, a ratiometric strategy was designed to detect FA with the fluorescence intensity ratio at 445 nm and 570 nm (F₄₄₅/F₅₇₀) as readout signal. This strategy exhibited a wide linear range (0.1-50 μM) and low detection limit of 0.03 μM. This method was confirmed for FA detection in food samples. In addition to establishing a new method to detect FA, this work will open new applications of MOF in food safety.

Application of Silicon Quantum Dots in the Detection of Formaldehyde in Water and Organic Phases

Background:

Formaldehyde is widely acknowledged as a carcinogen, but as an important organic reagent, it has also been widely employed in the fields of chemical synthesis, industrial production and biomedicine. It is therefore of great practical significance for the detection of formaldehyde in food, clothing, daily necessities, construction materials and environments.

Methods:

The two silicon QDs, that are, DAMO-Si-QDs (with N-[3-(Trimethoxysilyl) propyl] ethylenediamine as silicon source) and APTMS-Si-QDs (with (3-Aminopropyl) trimethoxysilane as silicon source) as the fluorescence probe to detect formaldehyde in both water and organic phases.

Results:

Silicon QDs prepared by different silicon sources exhibit an obvious difference in their tolerances to the environment and the responses to formaldehyde. However, APTMS-Si-QDs show better selectivity in both water and organic phases. In Tris-HCl solution (20.00mmol•L-1, pH=5), the formaldehyde concentration maintains an excellent linear relationship with the fluorescence intensity of APTMS-Si-QDs in the range of 3.125×10-7-3.125×10-5 mol•L-1, with correlation coefficient R2= 0.9998. In methanol, the formaldehyde concentration maintains an excellent linear relationship with the fluorescence intensity of APTMS-Si-QDs in the range of 1.563×10-7-3.125×10-5 mol•L-1, with correlation coefficient R2= 0.9992.

Conclusion:

It is found that DAMO-Si-QDs show poor response to the presence of formaldehyde, while APTMS-Si-QDs got a strong, sensitive and selective response to that in both aqueous and organic phases. In the Tris-HCl buffer (20 mmol•L-1, pH=5), the linear range for formaldehyde detection reaches 3.125×10-7-3.125×10-5 mol•L-1, and for the detection in the organic phase, the linear range reaches 1.563×10-7-3.125×10-5 mol•L-1, in methanol solution. The paper provides a sensitive, selective and simple means for formaldehyde detection in both aqueous and organic phase

Novel fluorescent organic nanoparticles as a label-free biosensor for dopamine in serum

Fluorescent organic nanoparticles composed of an organic dye and a triblock copolymer have been constructed and utilized as a fluorescent biosensor for dopamine.

Gold nanoparticle synthesis coupled to fluorescence turn-on for sensitive detection of formaldehyde using formaldehyde dehydrogenase

Ultrasensitive detection of formaldehyde by coupling enzyme activity with GNP synthesis.