Ru(bpy)32+-Conjugated Magnetic Nanoparticle as Fluorescent-Electrochemiluminescent Biological Label.

A ratiometric fluorescence nanosensor based on CdTe QDs for APE1 detection in breast cancer cell lysates.

Apurinic/apyrimidinic endonuclease 1 (APE1) is a critical DNA repair enzyme and an emerging biomarker for cancer diagnosis. Herein, we developed a ratiometric fluorescence nanosensor using dual-emission CdTe quantum dots (R-QDs) for sensitive detection of APE1, a DNA repair enzyme and cancer biomarker. The R-QDs consist of two CdTe QDs (530 nm and 620 nm) mixed at a 1 : 3 ratio, initially showing red fluorescence. A hairpin probe (HP1) containing an AP site was labeled with biotin for magnetic bead binding and a thiol for AgNP attachment. When APE1 cleaves the probe, the AgNP fragment is released, magnetically separated, and acid-treated to release Ag+ ions. These ions quench the R-QDs, causing a ratiometric fluorescence change. The sensor responds linearly to APE1 from 0-0.2 U mL-1, with a detection limit of 0.0141 U mL-1, and shows high selectivity against other enzymes. It successfully detected APE1 in breast cancer cell lysates (MCF-7, MDA-MB-231, A549), with good linearity (R2 = 0.99) and recovery rates of 94.5-107.2% (RSD < 5.2%). This method offers a reliable platform for APE1 detection in complex biological samples, aiding cancer diagnosis and treatment monitoring.

Fluorescent Probe with Dual Energy Transfer Process for Selective Fe3+ Detection and Cellular Imaging

Traditional fluorescent probes often exhibit compromised response and specificity due to poor adaptability to varying polar environments. Herein, we present the development of a robust Fe3+-specific small-molecule sensor by linking a tetraphenylsilole derivative and rhodamine 6G hydrazide via a Schiff-base π bridge to form a fluorescent donor–acceptor system. The dispersed silole moiety serves as dark donor, while the aggregated state of silole converts into emissive donor. Upon selective binding with Fe3+, the molecules are found to undergo fluorescence resonance energy transfer (FRET) and dark resonance energy transfer (DRET) to rhodamine moiety in a polarity-dependent manner. Hence, fluorescence quantitation of Fe3+ in both high-organic (>70%) and water-rich solutions (>70%) is successfully achieved with detection limits of 0.083 μM and 0.28 μM, respectively. Further, ratiometric intracellular imaging of Fe3+ is demonstrated using the probe. This sensing strategy can offer a promising avenue for the development of polarity-adaptive fluorescent probes targeting other metal ions in complex biological and environmental matrices.

A ratiometric fluorescent probe based on benzothiazole with a large Stokes shift for fluoride ion sensing in living cells, animals and plants.

The sensitive and selective detection of fluoride ions (F-) is of great significance in both environmental and biological systems. A novel near-infrared ratiometric fluorescent probe, PC-SZ-TBS, was designed and synthesized by rationally linking dicyanoisophorone with 2-(2-hydroxyphenyl)benzothiazole. The probe operates via F--triggered cleavage of the silicon-oxygen bond, resulting in a distinct fluorescence color change from yellow to bright red, along with significant fluorescence enhancement at 700 nm. Spectroscopic studies revealed that PC-SZ-TBS exhibits a low detection limit of 2.22 × 10-6 mol L-1 toward F-, maintains excellent stability over a pH range of 4-10, and displays high selectivity with minimal interference from competing species. Biocompatibility assays demonstrated that PC-SZ-TBS possesses low cytotoxicity and robust cell permeability in 4T1 cells, as well as favorable imaging capabilities in living organisms including zebrafish and Arabidopsis thaliana, enabling effective visualization of F- in biological tissues. Furthermore, PC-SZ-TBS was successfully applied to determine F- in real samples such as tap water, lake water, Chinese baijiu, and various fruits. Integrated with a smartphone-based RGB analysis platform, a strong linear correlation between the R/G ratio and F- concentration (R2 = 0.9978) was established, allowing for real-time, portable semi-quantitative detection of F-. This work provides a reliable and versatile tool for the visual monitoring of fluoride ions in both environmental and biological contexts.

A dual-quenching electrochemiluminescence immunosensor based on ABEI@Fe3O4@PDA-PdPt and Cu2−xS nanoflowers for sensitive detection of galectin-3

Dual-mode fluorescence and UV-vis aptasensor for hepatocellular carcinoma detection using magnetic separation

Photographic Physi-Luminescence Assay Based on a Persistent Luminescence Nanoprobe.

Chemi- or bioluminescence assays have broad applications in biomedical analysis, yet they still suffer from a flash effect or difficulty in maintaining time synchronization during high-throughput assays. Persistent luminescence (PersL) nanoprobes are able to emit photons for a rather long time without any chemical reactions and have promising applications in developing a physi-luminescence assay. Herein, SiO2/Zn2SiO4:Mn,Yb,Ge nanoparticles (MYG, Zn/Si/Mn/Yb/Ge molar ratio, 2/15/0.003/0.060/0.100) were synthesized with PersL properties at 525 nm. Mesoporous silica nanoparticles were used as a nanotemplate to control the size and morphology, which allowed for gram-scale production (1.1277 g). Ge was found to be an efficient codopant to realize the enhanced PersL of MYG. A hydrophobic azo dye, Sudan III, was loaded onto the MYG surface to form a quenched MYG-S nanoprobe. Under 254 nm UV illumination, Sudan III was oxidized by H2O2, and PersL was recovered. The "OFF-ON" PersL property of MYG-S was applied to develop a physi-luminescence assay method for H2O2, glucose, and glucose oxidase in serum. As the PersL of the samples in a 96-well plate was activated by simultaneous UV illumination rather than by adding chemicals, high-throughput photographic luminescence analysis was realized with accuracy and repeatability. Our research indicates the promising applications of PersL nanoprobes in developing a physi-luminescence assay.