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Specific staining of cancer cells is momentous for cancer research. Nanoprobe with multivalent recognition is emerging as powerful tools for bioimaging, but the nonspecific cell uptake and complex functional modification procedures are still obstacles for specific detection and convenient synthesis. Carbon dots (CDs) with an intrinsic targeting ability, excellent optical properties and biocompatibility acquired from an efficient one-step fabrication procedure were urgently desired in specific cancer cells visualization. Herein, inspired by the interrelationships between interface and biomolecular mechanisms, we suggested that it was possible to construct CDs with the desired characteristics for folate receptor (FR) positive-expressed cancer cell imaging via rich hydroxyl groups Tris-assisted one-step hydrothermal treatment of folate acid (FA) and l -Arginine (L-Arg) precursors. The prepared small-sized F-CDs were equipped with abundant hydroxyl, pterin and negative charge surface, and possessed environmental friendliness, outstanding photostability and biocompatibility. Moreover, F-CDs had an intrinsic FR positive-expressed cancer cell targeting ability without any post-modification of the ligands. Rich hydroxyl groups play a vital role in endowing the optical properties and biological effects of F-CDs. F-CDs could be used as a promising candidate for FR-expressed cancer cell labeling and tracking. In addition, the caveolae-mediated endocytosis pathway of F-CDs was ascertained. More importantly, experimental results confirmed that the combination of physicochemical properties may provide an efficient strategy to overcome non-specific cell uptake interactions for cell labeling. Our strategy put forward a promising alternative to design fluorescent CDs for extensive chemical and biomedical applications. Tris-assisted one-step fabrication of functional F-CDs for specific folate receptor positive-expressed cancer cell imaging. [Display omitted] • F-CDs were fabricated via rich hydroxyl groups Tris to mediate hydrothermal process of FA and L-Arg. • Rich hydroxyl groups of Tris play a vital role in the optical properties and intrinsic targeting ability for FR positive-expressed cancer cell for labeling and tracking. • This study provides an efficient strategy to design fluorescent CDs for extensive applications. [ABSTRACT FROM AUTHOR]

The facile and noninjurious image of cells with high resolution and low toxicity is essential since imaging can offer rich and direct information and insights into metabolic activities, clinical diagnosis, drug delivery and cancer therapy. In this contribution, a smart imaging probe was employed as a contrast agent for dark-field cell imaging. Au core/Ag shell nanorods (Au@Ag NRs) that characterized by X-ray diffraction and X-ray photoelectron spectroscopy, formed Au@Ag@AgI NRs when exposed to iodine, which greatly enhanced the light scattering of nanorods. Herein, the silver shell acted as the response element for iodine as well as the protective agent for Au core. When conjugated with folate, the nanorods can be used to image human cervical cancer cells (HeLa cells) under a dark-field microscope. Nanorods were demonstrated with excellent tumor cellular uptake ability without obvious cytotoxicity, making them ideal candidates in biosensing and bioimaging applications. Nanorods were restructured with iodine to enhance the light scattering for cell imaging, making them ideal candidates in bioimaging applications. [Display omitted] • The light scattering of AuNRs has been greatly enhanced for cell imaging. • The iodine-induced restructuring of Au@Ag NRs is highly specific among inorganic ions and biological macromolecules. • Nanorods with strong light scattering can enter cells readily, making them potentially useful as contrast agents. • Silver coating acted as the response element for iodine as well as the protective agent for AuNRs to avoid exposure to iodine. [ABSTRACT FROM AUTHOR]

The fluorescent probe, GXY-ADP-2, with xanthene structure as the fluorescent core was designed and prepared for the selective detection of peroxynitrite (ONOO−). ONOO− can be produced endogenously and exogenously and is a strong oxidant with a short half-life. Oxidative modifications of biomolecules, that can be attributed to the formation of ONOO−, occur in the reactions of biomolecules with secondary ONOO−-derived radical oxidants. Therefore, it is very important to develop a specific fluorescent probe for detecting ONOO− to monitor oxidative stress state. The excitation wavelength and emission wavelength of the probe are 689 nm and 739 nm respectively. In the process of co-incubation with ONOO−, generate a new substance with two internal conjugated structures through a special reaction mechanism, one giving the fluorescence with the excitation wavelength of 347 nm and the emission wavelength of 484 nm with the detection limit of 0.12 μM, and the other that with the excitation wavelength of 433 nm and the emission wavelength of 583 nm with the detection limit of 0.077 μM. The linear dynamic range of the probe is 0–5 μM. Its response is not affected by the other reactive oxygen species, thus can sensitively detect ONOO−. In bioimaging experiments with HepG2 cells, the green and blue cell fluorescence signals (583 nm and 433 nm, respectively) were increased, while the red one (739 nm) was significantly reduced, under lipopolysaccharide (LPS) induced oxidative stress, proving that the probe could sensitively detect ONOO− in living cells. This work provides a new tool for the dynamic changes of ONOO− and oxidative stress processes in biological systems. [Display omitted] • A new fluorescent probe, GXY-ADP-2, was developed for detection of ONOO−. • GXY-ADP-2 exhibited high specificity and sensitivity to ONOO−. • GXY-ADP-2 is a ratiometric fluorescent probe with three-channel fluorescence signal changed. • GXY-ADP-2 can detect the dynamic change of ONOO− in living cells. [ABSTRACT FROM AUTHOR]

Development of noninvasive bioimaging fluorescent probes for detecting particular enzyme activity is greatly recommendable for preclinical diagnosis of cancer. Given that the elevated β-gal activity is positively correlated with several tumors, developing a fluorescent probe for the sensing of β-gal is therefore highly desirable for cancer diagnosis. Herein, a new enzyme-activatable near-infrared (NIR) turn-on fluorescent probe (DMC-βgal) was developed for accurately detecting β-gal activity characterized by excellent selectivity, high sensitivity (LOD = 0.298 U/L), and low toxicity. More importantly, DMC-βgal qualifies remarkable NIR excitation (725 nm) and emission wavelength (770 nm), an ideal tool for restrained photodamage and suppressed autofluorescence. The above excellent performance of DMC-β-gal allowed for the accurate monitoring of endogenous β-gal in living cells. Moreover, the probe was successfully applied to detect intracellular β-gal activity in different types of cancer cells, verifying that SKOV-3 cells had a higher level of β-gal activity than those of A549, HCT-116, MCF-7, and HepG2 cells. Furthermore, DMC-βgal could real-time visualize endogenously β-gal in tumor-bearing nude mice with low auto-fluorescence interference. All results fully demonstrated that DMC-βgal has potential value as a promising strategy for diagnosis of β-gal-related diseases. [Display omitted] • A new near-infrared excited and emitted β-galactosidase (β-gal) fluorescent probe DMC-βgal was synthesized. • The probe DMC-βgal is characterized by excellent selectivity and high sensitivity (LOD = 0.298 U/L). • The probe is applied to prove that the β-gal activity in SKOV-3 cells is higher than HepG2, A549, HCT-116, MCF-7 cells. • DMC-βgal can real-time visualize the β-gal activity in tumor-bearing nude mice with low photodamage and autofluorescence. [ABSTRACT FROM AUTHOR]