Thiol-capped CdTe quantum dots with two-photon excitation for imaging high autofluorescence background living cells

Highly Retentive, Anti-Interference, and Covert Individual Marking Taggant with Exceptional Skin Penetration

The development of high-performance individual marking taggants is of great significance. However, the interaction between taggant and skin is not fully understood, and a standard for marking taggants has yet to be realized. To achieve a highly retentive, anti-interference, and covert individual marking fluorescent taggant, Mn²⁺ -doped NaYF₄ :Yb/Er upconversion nanoparticles (UCNPs), are surface-functionalized with polyethyleneimine (PEI) to remarkably enhance the interaction between the amino groups and skin, and thus to facilitate the surface adhesion and chemical penetration of the taggant. Electrostatic interaction between PEI₆₀₀ -UCNPs and skin as well as remarkable penetration inside the epidermis is responsible for excellent taggant retention capability, even while faced with robust washing, vigorous wiping, and rubbing for more than 100 cycles. Good anti-interference capability and reliable marking performance in real cases are ensured by an intrinsic upconversion characteristic with a distinct red luminescent emission under 980 nm excitation. The present methodology is expected to shed light on the design of high-performance individual marking taggants from the perspective of the underlying interaction between taggant and skin, and to help advance the use of fluorescent taggants for practical application, such as special character tracking.

Quantum dots: bright and versatile in vitro and in vivo fluorescence imaging biosensors

Colourful cells and tissues: semiconductor quantum dots and their versatile applications in multiplexed bioimaging research.

One-step synthesis of water-dispersible silicon nanoparticles and their use in fluorescence lifetime imaging of living cells

Fluorescence intensity (upper panel) and lifetime (bottom panel) images of KB cells stained with FITC (B), Si NPs (C) and unstained control (A).

Quantum dots in bioanalysis: a review of applications across various platforms for fluorescence spectroscopy and imaging

Semiconductor quantum dots (QDs) are brightly luminescent nanoparticles that have found numerous applications in bioanalysis and bioimaging. In this review, we highlight recent developments in these areas in the context of specific methods for fluorescence spectroscopy and imaging. Following a primer on the structure, properties, and biofunctionalization of QDs, we describe select examples of how QDs have been used in combination with steady-state or time-resolved spectroscopic techniques to develop a variety of assays, bioprobes, and biosensors that function via changes in QD photoluminescence intensity, polarization, or lifetime. Some special attention is paid to the use of Förster resonance energy transfer-type methods in bioanalysis, including those based on bioluminescence and chemiluminescence. Direct chemiluminescence, electrochemiluminescence, and charge transfer quenching are similarly discussed. We further describe the combination of QDs and flow cytometry, including traditional cellular analyses and spectrally encoded barcode-based assay technologies, before turning our attention to enhanced fluorescence techniques based on photonic crystals or plasmon coupling. Finally, we survey the use of QDs across different platforms for biological fluorescence imaging, including epifluorescence, confocal, and two-photon excitation microscopy; single particle tracking and fluorescence correlation spectroscopy; super-resolution imaging; near-field scanning optical microscopy; and fluorescence lifetime imaging microscopy. In each of the above-mentioned platforms, QDs provide the brightness needed for highly sensitive detection, the photostability needed for tracking dynamic processes, or the multiplexing capacity needed to elucidate complex systems. There is a clear synergy between advances in QD materials and spectroscopy and imaging techniques, as both must be applied in concert to achieve their full potential.

Luminescent nanoparticles and their use for in vitro and in vivo diagnostics

Fluorescence spectroscopy has been shown to be a useful tool for a broad variety of biological and medical applications. Many of the analytical methods, as used for tumor marker and gene mutation detection, recognition of pathogens or monitoring of cell-related processes, are based on the labeling of the investigating object with luminescent nanoparticles. Owing to their size, which is comparable to that of biomolecules, and to their extraordinary optical properties, luminescent nanoparticles could well improve the sensitivity and flexibility of current detection techniques. This article provides a general overview of the synthesis, properties and application of luminescent semiconductor, metal and inorganic nanoparticles for in vitro and in vivo diagnostics, also reflecting the aspect of biocompatibility.