A long lifetime ratiometrically luminescent tetracycline nanoprobe based on Ir(III) complex-doped and Eu3+-functionalized silicon nanoparticles.

Different from fluorescent dyes-doped or carbon materials-based ratiometric tetracycline nanoprobes, herein, a new Ir(III) complex-doped and europium(III) ion (Eu3+)-functionalized silicon nanoparticles (Ir(III)@SiNPs-Eu3+) with long luminescent lifetimes was firstly fabricated for selective detection of tetracycline (TC) in complex systems through time-resolved emission spectra (TRES) measurement. In the presence of TC, the red phosphorescence of Eu3+ is greatly enhanced by adsorption energy transfer emission (AETE) of TC, while the strong green luminescence of Ir(III)@SiNPs is quenched by the inner filtration effect (IFE) of TC. Based on these striking emission changes, Ir(III)@SiNPs-Eu3+ can sensitively detect TC in the linear range of 0.01-20 µM with a detection limit of 4.9 × 10-3 µM. Benefitting from the long lifetime of Ir(III)@SiNPs-Eu3+, the nanoprobe demonstrates excellent TC detection performance through TRES in high background system of 5 % human serum. Furthermore, the formed Ir(III)@SiNPs-Eu3+/TC complex can be used to sensitively recognize Hg2+ via a ratiometric luminescence mode. Notably, the cytotoxicity of Ir(III)@SiNPs-Eu3+ is very low and thus the sensitive monitoring the detection of Ir(III)@SiNPs-Eu3+ to TC and Hg2+ also works well in porcine renal cells, demonstrating high application potential in real samples.

A luminescent microRNA nanoprobe based on the target-triggered release of an iridium(III)-solvent complex from mesoporous silica nanoparticles.

A luminescent microRNA nanoprobe based on the target-triggered Ir(III)-solvent complex release has been fabricated. The complex is initially embedded into mesoporous silica nanoparticles (MSNs), and then is capped by single-stranded (ss) DNA. In the presence of the target microRNA, the ssDNA hybridize with the microRNA forming a rigid DNA/RNA heteroduplexes and leaving the surface of MSN. Thus, the capped Ir(III) solvent complex is released and re-coordinated with histidine (His) to form a new luminescent complex. The luminescence intensity of the nascent complex (with excitation/emission maxima at 340/570 nm) is positively correlated with the concentrations of the target microRNA in the range from 0.05 to 2 nM, and the detection limit of microRNA is estimated as 0.2 pM (S/N = 3). The ability of this nanoprobe to detect microRNA in cell extract further demonstrates its potential in practical application. Graphical abstractSchematic of a luminescent microRNA nanoprobe based on the target-triggered release of an Ir(III)-solvent complex from mesoporous silica nanoparticles.

γ-Aminobutyric acid-modified graphene oxide as a highly selective and low-toxic fluorescent nanoprobe for relay recognition of copper(II) and cysteine.

A sensitive and selective graphene oxide (GO)-based fluorescent nanoprobe has been developed for the relay recognition of Cu2+ and cysteine (Cys) by covalently grafting γ-aminobutyric acid (GABA) onto GO. The fluorescence of the probe (with excitation/emission maxima at 360/445 nm) is selectively quenched by Cu2+ via static fluorescence quenching. Fluorescence drops linearly as the concentration of Cu2+ is increased from 50 nM to 1.0 µM, and the detection limit for Cu2+ is calculated as 15 nM. By virtue of the strong interaction between Cys and Cu2+, the GO-GABA/Cu2+ complex can further sensitively recognize Cys in a "switch-on" mode. The linear range for Cys detection is from 50 nM to 1.0 µM, and the detection limit is 38 nM. The probe has low cytotoxicity, and it works well inside living cells, which is verified by the successful application in imaging of LLC-PK1 cells. Graphical abstract Gamma-Aminobutyric Acid (GABA) modified graphene oxide (GO) is a highly selective nanoprobe for the fluorometric relay recognition of Cu2+ and Cys.

A label-free and enzyme-free fluorescent aptasensor for sensitive detection of acetamiprid based on AT-rich dsDNA-templated copper nanoparticles.

A label-free and enzyme-free aptasensor for sensitive assay of acetamiprid has been established using AT-rich double-stranded (ds) DNA-templated copper nanoparticles (CuNPs) as fluorescent probe. In this work, two hairpin DNA, HP1 and HP2, were elaborately designed with AT-rich DNA sequences in their loops. The aptamer of acetamiprid was located at the 3'-terminal of HP1, which was caged in the stem of HP1. Upon the addition of acetamiprid, the aptamer could combine with acetamiprid to form a target/aptamer complex, and thus its free 5'-terminal was released. Subsequently, the protruded 3'-terminal of HP2 could hybridize with the free 5'-terminal of HP1 to form a stable AT-rich dsDNA. When it interacted with Cu2+ and ascorbic acid (AA), the AT-rich dsDNA/CuNPs were generated with strong fluorescence, offering a "switch-on" detection of acetamiprid. The developed strategy could high selectively detect acetamiprid at the concentration as low as 2.37 nM. Moreover, the possibility of this strategy for the food sample analysis was also investigated. The obtained results demonstrate that the developed strategy has a promising application potential for acetamiprid assay in food safety fields.