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Fluorescent lateral flow immunoassay (LFA), one tool in point of care testing (POCT) systems for breast cancer, has attracted attention because it is quick, simple, and convenient. However, samples and the constituent material exhibit autofluorescence in the visible region, which is a very large obstacle in the development of fluorescent LFAs. The autofluorescence of biological samples is scarcely found in the second near-infrared (NIR-II) range and samples scatter and absorb less NIR-II light than visible light. Here, we report an NIR-II QD-LFA platform using the NIR-II fluorescent Ag2Se quantum dots (QDs) with 1020 nm emission encapsulated into polystyrene beads as fluorescent probes. The NIR-II LFA platform was established to detect breast cancer tumour markers (CEA and CA153) within 15 min with a low limit of detection (CEA: 0.768 ng mL−1, CA153: 1.192 U mL−1), high recoveries (93.7% ~ 108.8%), and relative standard deviations (RSDs) of less than 10%. This study demonstrated the potential of NIR-II Ag2Se polystyrene beads as a fluorescent probe in LFA for rapid and accurate identification of biomarkers. They are suited for use in professional situations. [ABSTRACT FROM AUTHOR]

Fluorescence in the near infrared IIb window (NIR-IIb, 1500–1700 nm) shows higher signal-to-noise ratio, better space-time resolution, and deeper tissue penetration. However, materials with excellent fluorescence properties in the NIR-IIb region were rarely reported. Ag2Te quantum dots (QDs) could emit variable fluorescence in the NIR-II window due to their narrow band gap. Unfortunately, the fluorescence in the NIR-IIb region was not strong enough to image in vivo because the lattice defects on the surface of Ag2Te increased non-radiative transitions and decreased fluorescence performance. In this work, we coated a Ag2Te core with a Ag2Se shell to passivate the lattice defects and enhance its fluorescence efficiency. The fluorescence property of the as-prepared Ag2Te/Ag2Se core/shell QDs is more than 10 times stronger than that of Ag2Te. The brighter Ag2Te/Ag2Se QDs showed high-resolution in vivo imaging in the NIR-IIb region to distinguish thin blood vessels up to 66 μm. Overall, Ag2Te/Ag2Se QDs with excellent fluorescence in the NIR-IIb region were prepared and showed great potential for biomedical imaging. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is an important small-molecule neurotransmitter, which is closely related to the development of many neurological diseases and has received increasing attention in the diagnosis of neurological diseases. Currently, the assays of the detection of dopamine such as electrochemical and colorimetric methods have low sensitivity, poor selectivity and susceptibility to interference, which limit the accurate quantification of dopamine. Fluorescence anisotropy immunoassay is a traditional analytical method in which the quantification is based on the change in fluorescence anisotropy values observed when fluorescence molecules are bound to a certain volume and mass of the material. Since dopamine is a small molecule with small volume and mass, we took advantage of the good photostability of the second near-infrared window (NIR-II) quantum dots (QDs) and the low spontaneous interference of the substrate, and designed a biosensor dopamine fluorescence anisotropy probe streptavidin biosensor (DFAP-SAB) based on the NIR-II QDs combined with streptavidin signal amplification to achieve rapid and separation-free detection of dopamine in human serum. The detection signal has a good linearity between 50 nM and 3000 nM with a detection limit of 11.2 nM. The application of NIR-II QDs provides the possibility of biosensor applications for complex samples. The construction of the streptavidin signal amplification device provides a new idea for small molecule detection. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbX3 (X = I, Br, Cl) perovskite nanocrystals have emerged as a new class of optoelectronic material with tunable emission wavelengths, narrow full-width at half-maximum (FWHM) and high photoluminescence quantum yields (PLQYs) (≥50% in general). However, the instability caused by high delocalization of surface ions is still the major issue that obstructs their application. The type of surface ligands plays a key role in the stability of perovskite nanocrystals. In this work, stable cubic Br-rich CsPbBr3 quantum dots (QDs) with uniform particle sizes, high quantum yields and high crystallinity were obtained by a one-step hot-injection synthesis method. Oleylamine (OM) as one of the ligands in the classic synthesis method was replaced with (3-aminopropyl)triethoxysilane (APTES). The stability of the CsPbBr3 QDs was significantly improved under different testing conditions. [ABSTRACT FROM AUTHOR]