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The arsenic contamination of aquatic food has emerged as a serious concern in recent years due to its hazardous effect on human health. Herein, the multifunctional Fe 3 O 4 @NaGdF 4: Yb: Er (Fe@UCNPs) with fluorescent and magnetic dual properties were fabricated and subsequently applied to construct a platform for detecting the arsenic (As(III)). A luminescence resonance energy transfer (LRET) biosensor was developed with the aptamer-modified magnetized upconversion nanoparticles (Fe@UCNPs) as the donor and tetramethylrhodamine (TAMRA) as the acceptor. Most importantly, Fe@UCNPs revealed highly integrated magnetic and fluorescence properties, thus, allowing the enrichment of targets in the fresh solution by magnetic separation, and avoiding the interference from the detection environment, along with enabling the signal accumulation and amplification. Moreover, the sensor was successfully used for the sensing analysis of As(III) in real samples (fish and shrimp), demonstrating that the biosensor to be a sensitive and specific quantitative platform for arsenic monitoring. [Display omitted] • A novel aptasensor based on the LRET between multifunctional UCNPs and TAMRA has been developed. • The proposed sensor was successfully used for the sensing analysis of As3+ in real samples. • The biosensor achieved accurate separation and detection without the environmental disturbances. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Preparation of surface-modified PLNPs (ZnGa 2 O 4 : Mn2+) with good luminescent property. • Design of luminescence resonance energy transfer DEHSPI-PLNPs sensing system for sensitive detection of CN−. • Successful application for bioimaging in living cells. Abstract Cyanide anion is an inhibitor of the enzyme cytochrome c oxidase in the fourth complex of the electron transport chain, and usually found in the membrane of the mitochondria of eukaryotic cells, thus exploration of novel analytical methodology for sensitive and accurate detection of cyanide ion in cells is vital and urgent. Herein, we successfully prepared and surface-modified ZnGa 2 O 4 :Mn2+ PLNPs with excellent afterglow properties, small size and preferable dispersibility. Furthermore, we report a rational design and fabrication of a functional PL nanoprobe based on luminescence resonance energy transfer (LRET), which for the first time demonstrates detection of cyanide ion without external illumination. The nanoprobe is composed of two main moieties: PLNPs with excellent afterglow properties as energy donor; and DEHSPI, a chromophore with tunable light absorption, as both energy acceptor and CN− recognition element. PL can be effectively quenched by the chromophores assembled on the surface of PLNPs through a LRET process and subsequently recovered upon the addition of CN−. Importantly, the persistent afterglow nature highlights the merits of employing PLNPs as energy donor to eliminate the background noise under in situ excitation. Moreover, the nanoprobe exhibits excellent analytical properties and low cytotoxicity for bio-imaging of CN− in living cells. [ABSTRACT FROM AUTHOR]

Melioidosis caused by Burkholderia pseudomallei (Bp) infection has high mortality in tropical and subtropical regions. A rapid and sensitive method for its detection is urgently needed. Herein, a ratiometric fluorescent sensor with dual recognition sites of target was designed for sensitive detection of Bp DNA. The sensor was constructed with a TAMRA-labeled DNA as probe, which could adsorb on polymer dots (Pdots) at acidic pH to produce TAMRA fluorescence at the excitation wavelength of Pdots via fluorescence resonance energy transfer (FRET). In the presence of target DNA, the trans-cleavage activity of CRISPR/Cas12a was activated with the dual recognition sites, which digested the probe DNA to weaken the FRET. With the fluorescence ratio of Pdots to TAMRA as the detection signal, a ratiometric fluorescent biosensing was thus achieved. This method with dual CRISPR/Cas12a trans-cleavage assisted signal enhancement showed a detectable range of target DNA from 1.0 pM to 10 nM, and could be successfully used to detect Bp DNA extract with a detection time of 40 min. The excellent performance such as high sensitivity, good specificity, acceptable accuracy and short analytical time along with convenient operation demonstrated its potential in clinic diagnosis of melioidosis. • A dual CRISPR/Cas12a trans-cleavage assisted signal enhancement strategy is proposed for biosensing of biomarker. • The proposed biosensing method based on ratiometric fluorescence has been used for detection of Burkholderia pseudomallei. • The proposed method shows a wide detection range with LOD of 1 pM and a detection time of 40 min with simple operation. • This proposed strategy possesses excellent performance and good extendability for target DNA analysis. [ABSTRACT FROM AUTHOR]