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Fluorescent gold nanoclusters (AuNCs) are emerging as novel imaging contrast agents. These molecules offer excellent prospects for non-invasive tumor diagnosis strategies because of their ultra-small size, tunable emissions from the visible to the near-infrared range, excellent biocompatibility, and suitable pharmacokinetic properties. In this tutorial review, we introduce the physiological features of the tumor microenvironment, followed by a description of AuNC pharmacokinetics. Next, we outline the strategies used to deliver AuNCs specifically to tumor tissues for in vivo tumor imaging. Finally, examples are presented to highlight the application potential of AuNCs for in vivo tumor imaging. [ABSTRACT FROM AUTHOR]

Protein-stabilized gold nanoclusters (protein-Au NCs) have been an attractive frontier of nanoparticle research. Due to their unique fluorescence properties, high stability, environmentally friendly synthetic routes and nontoxicity, protein-Au NCs could find applications in highly sensitive and selective detection of metal ions, inorganic ions and biomolecules in food, soil, water and biological samples. The past few years have witnessed the development of many successful strategies for the preparation of numerous protein-Au NC-based sensing systems. In this review, we focus on a number of sensing systems based on protein-Au NCs for the detection of various analytes of interest with a special emphasis on their corresponding sensing mechanisms. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is an important signaling molecule in biology. Both NO excess and insufficiency have been implicated in numerous physiological and pathological conditions. In order to study the diverse biological roles of NO in cells and tissues, many techniques have been developed for assaying NO. Recently, new generations of fluorescent probes have become indispensible tools for the study of NO biology because of their sensitivity, selectivity, spatiotemporal resolution, and experimental feasibility. Rational application of these probes in the study requires the understanding of the molecular mechanism that the probes are involved in. In this review, we will present an arsenal of fluorescent probes used to detect NO in living cells and animal tissues. We will also discuss the molecular mechanisms, actualities and prospects of fluorescent probes in detecting NO in cell biology. [ABSTRACT FROM AUTHOR]

Bifunctional Ag2S QDs@CS-RBS nanospheres with ultralow toxicity for biomedical use were fabricated. These are capable of releasing NO under irradiation of visible light and emitting in near-infrared (NIR) region fluorescence excited by NIR laser under physiological environment. Glutathiose (GSH)-capped Ag2S QDs were synthesized and encapsulated by chitosan (CS) to form NIR fluorescent Ag2S QDs@CS nanospheres. A type of iron/sulfur/-nitrosyl cluster, Roussin's black salt anion Fe4S3(NO)7− (RBS) was conjugated with the Ag2S QDs@CS to obtain Ag2S QDs@CS-RBS nanospheres. A variety of characterization methods were employed to analyze the nanospheres. In vitro cell imaging and in vivo mice imaging experiments demonstrated that the Ag2S QDs@CS-RBS nanospheres could emit readily observable NIR fluorescence and deliver NO in living cells and small animals. The NIR imaging of the Ag2S QDs@CS nanospheres would not interfere with the light-triggered NO release from them, as the excitation lasers needed for these two functions are in different wavelength regions. This work provides new perspectives for the application of multifunctional nano-structured materials in diagnostics and bioimaging. [ABSTRACT FROM AUTHOR]

A new CuFL (2-{2-chloro-6-hydroxy-5-[(2-methyl-quinolin-8-ylamino)-methyl]-3-oxo-3H-xanthen-9-yl}-benzoic acid)–CS (chitosan) NS diazeniumdiolates system consisting of NO donors and highly-sensitive NO probes is reported. FL–CS NS diazeniumdiolates were synthesized by incorporating the fluorescent molecule FL with chitosan (CS) and reacting the resultant FL–CS complex with pressurized NO and dimethyl sulfate (DMS). Then the FL–CS NS diazeniumdiolates were reacted with copper chloride (CuCl2) to generate non-fluorescent CuFL–CS NS diazeniumdiolates. The CuFL–CS NS diazeniumdiolates have a spherical outline with a dimension of ca. 250 nm. They have high selectivity for NO over other related substances. The results of in vitro and in vivo experiments indicate that the CuFL–CS NS diazeniumdiolates can release NO under physiological conditions and meanwhile detect the released NO based on the considerable fluorescence increase of the otherwise non-fluorescent system caused by the NO. The good fluorescence stability of the NO–FL–CS NS provides prospects for the CuFL–CS NS diazeniumdiolates in biomedical applications. [ABSTRACT FROM AUTHOR]