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Glycol chitosan (GC), a water-soluble chitosan derivative with hydrophilic ethylene glycol branches, has both hydrophobic segments for the encapsulation of various drugs and reactive functional groups for facile chemical modifications. Over the past two decades, a variety of molecules have been physically encapsulated within or chemically conjugated with GC and its derivatives to construct a wide range of functional biomaterials. This review summarizes the recent advances of GC-based materials in cell surface labeling, multimodal tumor imaging, and encapsulation and delivery of drugs (including chemotherapeutics, photosensitizers, nucleic acids, and antimicrobial agents) for combating cancers and microbial infections. Besides, different strategies for GC modifications are also highlighted with the aim to shed light on how to endow GC and its derivatives with desirable properties for therapeutic purposes. In addition, we discuss both the promises and challenges of the GC-derived biomaterials. [ABSTRACT FROM AUTHOR]

• A green fluorescent probe for low-cost, efficient, precise, and universal live/dead cell imaging is developed. • An accurate quantification method for live/dead cells is proposed. • Real-time dynamic visualization of in vivo drug toxicity/efficacy is realized. Rapid and quantitative discrimination between live and dead cells is highly desirable yet remains a challenging task. Here, we report the use of the ultrabright green-emitting organosilica nanodots (OSiNDs, photoluminescence quantum yield: ˜100%) for fast (1 min in vitro and 5 min in vivo), wash-free, and universal labeling of the dead bacterial, fungal, and mammalian cells, which meets the demand of the green fluorescent probes that can specifically image the dead cells. The photostability of OSiNDs surpasses that of the commercial dyes, such as propidium iodide (PI) and SYTOX Green nucleic acid stain (SYTOX), making OSiNDs more suitable for long-term and stable monitoring of the cell viability. With the assistance of a commercial red fluorescent dye SYTO 60, we develop an in situ method for rapid and accurate quantification of live/dead cells. Motivated by the unique optical advantages and high sensitivity of OSiNDs to the cell viability, the OSiNDs are employed to observe the in vivo cellular changes induced by doxorubicin using zebrafish as a model, demonstrating their great potential for evaluating the toxicity/efficacy of the therapeutic agents in real time. Owing to the excellent biocompatibility and low cost, the OSiNDs can be a universal probe for efficient and accurate differentiation and quantification of the live and dead cells, which may find wide applications in the biomedical field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrabright S-doped carbon dots (SCDs) are prepared for five important applications. • The SCDs can realize bacterial Gram-type identification and fungal cell imaging. • The SCDs can realize endoplasmic reticulum (ER) imaging and ER stress monitoring. • A Cu/SCD nanocomposite is prepared by mixing SCDs and Cu2+ for glutathione detection. • The Cu/SCD nanocomposite can realize normal/cancer cell discrimination. Developing a single system capable of realizing bacterial Gram-type identification, fungal cell imaging, endoplasmic reticulum (ER) imaging, glutathione (GSH) detection, and normal/cancer cell discrimination with excellent performance is a huge challenge. Herein, ultrabright green-emitting endoplasmic reticulum-targeting sulfur-doped carbon dots (SCDs) with a quantum yield of ∼ 78 % were synthesized via the hydrothermal treatment of rose bengal (RB) and dl -cysteine (Cys). The obtained SCDs possessed excellent fluorescence stability, unique excitation-independent emission property, and satisfactory biocompatibility. We demonstrated that the SCDs could be used for fast (15 min) identification of Gram-positive bacteria due to their S-containing groups (e.g., sulfate and sulfydryl groups) and high-quality fungal cell imaging. We also demonstrated that the SCDs could realize selective and long-term ER imaging in normal/cancer cells, and achieve the monitoring of the cell behaviors during ER stress caused by starvation or various ER stress inducers in live cells. Further, by mixing SCDs and Cu2+, we prepared Cu/SCD nanocomposites (Cu/SCDs), in which the fluorescence of SCDs was quenched by Cu2+ and could recover upon the addition of GSH, realizing GSH detection with a limit of detection of 0.681 μM. Subsequently, based on the much higher GSH level of cancer cells than that of normal cells, Cu/SCDs were successfully applied for distinguishing normal cells from cancer ones. Overall, this work fabricates ultrabright and multifaceted SCDs for precise and high-quality cell imaging and GSH detection, confirming the great potential of SCDs for versatile biomedical applications. [ABSTRACT FROM AUTHOR]

Given the significant impact of ions on environment pollution and human health, it is urgently needed to establish effective and convenient ion detection approaches, particularly in living cells. In this paper, we constructed multicolor N-doped-carbon dots (mPD-CDs) by facile one-step hydrothermal carbonization of m-phenylenediamine (mPD). mPD-CDs were successfully deployed for multicolor cellular imaging for animal cells, fungi, and bacteria in a wash-free way with high photostability and satisfactory biocompability. Moreover, mPD-CDs can be used as a fluorescent sensing probe for ultrasensitive detection of both iodide ion (I−) and typical heavy metals such as cadmium (Cd2+), copper (Cu2+), mercury (Hg2+), gadolinium (Gd3+), ferrous ion (Fe2+), Zinc (Zn2+), and ferric ion (Fe3+). This is the first report using CDs as optical sensing probe for the detection of Gd3+, and for detection of Fe3+ with fluorescence "turn on". More significantly, with these versatile and fascinating properties, we applied mPD-CDs for intracellular ion detection in living cells like Hep G2 and S. cerevisiae, and zebra fish. Altogether, mPD-CDs displayed great potential for multicolor cell imaging and the multiple ion detection in vitro and in vivo, presenting a promising strategy for in-situ ultrasensitive sensing of multiple metal ions in the environment and the biological systems. [ABSTRACT FROM AUTHOR]

Congo red (CR) is a hazardous pigment, posing increasing dangerous to the environment and human health. However, the in-situ detection of CR in living cells has not been reported, as far as we know. Here, negatively-charged green-emitting Ca, N, S-doped carbon dots (Mis-mPD-CDs) were fabricated from plant and m-phenylenediamine (mPD) by facile one-step hydrothermal carbonization. Mis-mPD-CDs were capable of rapidly detecting CR on the basis of their fluorescence quenching by CR due to the inner filter effect. This CR detection based on Mis-mPD-CDs displayed a linear range of 0.2–1.2 μM and a low limit of detection (58 nM), and was not interfered by metal ions, important biological molecules, and other dyes, showing high sensitivity and selectivity. More interestingly, Mis-mPD-CDs can rapidly enter and label animal cells (A549, 4T1, and HUVEC), fungi (S. cerevisiae , C. albicans , and T. reesei), and bacteria (E. coli and S. aureus) for long term with high stability and appealing biocompatibility. Based on these compelling characteristics, we applied Mis-mPD-CDs for sensing and imaging CR in living cells (A549, C. albicans , E. coli, and S. aureus) and zebra fish. On the other hand, the quantitative detection of CR by Mis-mPD-CDs was realized in real samples like fish tissues and industrial wastewater. This is the first report on applying CDs for rapid CR detection in living cells and in vivo. Mis-mPD-CDs provides a novel efficient platform for probing intracellular CR, expanding the applications of CDs as biosensors for toxic dyes. [Display omitted] • Mis-mPD-CDs were hydrothermally synthesized from plant and mPD. • Mis-mPD-CDs can rapidly detect Congo red (CR) with high sensitivity and selectivity. • Mis-mPD-CDs can rapidly image universal cells for long time with great stability and safety. • Mis-mPD-CDs were applied for sensing CR in living cells and zebra fish. • Mis-mPD-CDs were used for the quantitative assay of CR in fish tissues and wastewater. [ABSTRACT FROM AUTHOR]