An activatable nanoprobe for imaging breast cancer metastases through near infrared‐I (NIR‐I)/NIR‐II fluorescence imaging and multispectral optoacoustic tomography (MSOT) imaging was designed. With a dihydroxanthene moiety serving as the electron donor, quinolinium as the electron acceptor and nitrobenzyloxydiphenylamino as the recognition element, the probe can specifically respond to nitroreductase and transform into an activated D‐π‐A structure with a NIR emission band extending beyond 900 nm. The activated nanoprobe exhibits NIR emission enhanced by aggregation‐induced emission (AIE) and produces strong optoacoustic signal. The nanoprobe was used to detect and image metastases from the orthotopic breast tumors to lymph nodes and then to lung in two breast cancer mouse models. Moreover, the nanoprobe can monitor the treatment efficacy during chemotherapeutic course through fluorescence and MSOT imaging.

Intracellular viscosity is an essential microenvironmental parameter and HS is a critical gaseous signaling molecule, which are both related to various physiological processes. It is reported that the change of viscosity and an imbalance of HS production in the mitochondria are both associated with overexpression of amyloid betapeptide (Aβ), which is thought to play a central role in the pathogenesis of Alzheimer's disease (AD). However, to our best knowledge, no fluorescent probe is found for dual detection of mitochondrial viscosity and HS. Herein, a dual-response fluorescent probe (Mito-VS) is designed and synthesized to monitor the level of viscosity and HS, respectively. Mito-VS itself is nonfluorescent due to a free intramolecular rotation between dimethylaniline and pyridine. After the increase of viscosity, the rotation is prohibited and an intense red fluorescence is released. Upon the addition of HS, the probe can react with HS to form compound 3 and a strong green fluorescence can be observed. Moreover, the probe possesses a good mitochondrion-targeting ability and is applied for imaging the change of viscosity on the red channel and visualizing the variation of exogenous and endogenous HS concentration on the green channel in mitochondria. Most importantly, the probe is capable of studying the cross-talk influence of viscosity and HS in mitochondria, which is very beneficial for knowing the pathogenesis of AD.

Glutathione (GSH), cysteine (Cys), and homocysteine (Hcy) are small-molecular biothiols that play key roles in various biological systems. Among these biothiols, GSH is the most abundant intracellular thiol. Until now, a small number of the near-infrared (NIR) fluorescent probes have been designed for the detection of GSH. Unfortunately, most of these NIR probes are based on cyanine dyes, which generally suffer low fluorescence quantum yield (Φ < 0.25), which are not suitable for bioimaging. In addition, some probes are difficult to effectively distinguish GSH from Cys and Hcy. In this work, an NIR fluorescent probe with high fluorescence quantum yield is developed by introducing a rigid coplanar structure such as rhodamine dyes, and the NIR probe (CyR) with spirolactam structure is first synthesized and used to recognize GSH. The characteristics of this NIR probe are as follows: (1) probe CyR exhibits high fluorescence quantum yield (Φ = 0.43) after the addition of GSH and high sensitivity toward GSH with 75-fold fluorescence enhancement. (2) The probe is highly selective, which will not interfere with the other biological thiols (Cys, Hcy) and amino acids. (3) A possible reaction mechanism of the NIR probe CyR and GSH (Cys, Hcy) can be proposed and proved by H NMR,C NMR, and MS (mass spectra). (4) The NIR probe displays selective detection of GSH in biological samples such as living cells and tissues.

Alkaline phosphatase (ALP) is an essential enzyme and widely distributes in a variety of tissues. To date, various nanomaterial and small-molecule fluorescent probes for ALP have been constructed successfully, but the emission wavelengths of these probes are in the ultraviolet or visible range, which is not beneficial for bioimaging. Herein, a hemicyanine-based near-infrared (NIR) fluorescent probe named CyP is first synthesized and used to detect ALP activity. The characteristics of probe CyP are as follows: (1) The probe possesses a facile structure, which can be obtained by easy synthetic steps. (2) The fluorescence emission of the sensing system is at 738 nm belonging to NIR region, which is suitable for bioimaging in vivo. (3) The probe exhibits high sensitivity to ALP with 10-fold fluorescence enhancement and low detection limit (0.003 U/mL) can match the level of ALP in vivo. (4) The fluorescent change of the probe is attributed to the fact that ALP-catalyzed cleavage of the phosphate group in CyP induces the transformation of CyP (fluorescence off) into CyOH (fluorescence on), which is proved by HPLC, P NMR, MS, and DFT calculation. (5) The NIR fluorescent probe is applied for the detection of endogenous ALP activity in various biological samples such as cell, tissue, and living animal with satisfactory results.

Background: Sox2 is important for the establishment and maintenance of pluripotency. Results: This study shows that cyclin-dependent kinase (Cdk)-mediated phosphorylation of Sox2 is important for establishing pluripotency during reprogramming but is dispensable for maintaining the pluripotency of mouse ESCs. Conclusion: Cdk-mediated Sox2 phosphorylation regulates pluripotency establishment. Significance: Our findings can explain why inactivating cell cycle inhibitors can promote reprogramming.

The precise location of tumor and completeness of surgical resection are critical to successful tumor surgery; thus, the method capable of preoperatively locating a tumor site and intraoperatively determining tumor margins would be highly ideal. Herein, an activatable nanocomposite probe was developed for preoperatively locating orthotopic hepatic tumor via multispectral optoacoustic tomography imaging and for intraoperative navigation via near-IR-1 (NIR-I) and NIR-II fluorescence imaging. The molecular probe comprises an electronic donor, an acceptor, and a recognition moiety and forms the nanocomposite probe with bovine serum albumin. The probe specifically responds to nitroreductase overexpressed in tumor cells, which transforms the aromatic nitro group into an electron-donating amino group and thus activates the probe. The activated probe with the aggregation-induced emission feature generates strong NIR-I/NIR-II fluorescence and optoacoustic signals for dual-mode imaging. Owing to the in situ response toward nitroreductase in tumor cells in the hepatic region, the probe is found capable of detecting early stage orthotopic liver tumors. Furthermore, with the nanocomposite probe, we can obtain the 3D MSOT images to accurately locate orthotopic liver tumors preoperatively and the NIR-I/NIR-II fluorescence images to provide intraoperative guidance for tumor resection surgery.

The ability to detect cancer early in an accurate and rapid fashion is of critical importance for cancer diagnosis and accurate resection in surgery. γ-Glutamyltranspeptidase (GGT) is overexpressed in several human cancers, while maintaining a low expression in normal microenvironments, and thus is recognized as an important cancer biomarker. To date, rational design of a zero cross-talk ratiometric near-infrared (NIR) GGT fluorescent probe for efficient cancer diagnosis in various biological samples is still a big challenge. In this work, a zero cross-talk ratiometric NIR GGT fluorescent probe named Cy-GSH is developed. Cy-GSH shows high sensitivity to GGT, which is desired for early cancer diagnosis. Upon additional GGT, a large emission shift from 805 to 640 nm is observed, which is suitable for visualizing deeply located cancer in vivo. In addition, successful monitoring of GGT activity in blood, cells, tissues, and in vivo makes Cy-GSH possess great potential for the clinical cancer early diagnosis. Furthermore, accurately visualizing tumors and metastases in mouse models illuminates that the probe may be a convenient tool for fluorescence-guided cancer surgery. To our knowledge, this is the first report to describe the strategy of a zero cross-talk ratiometric NIR GGT fluorescent probe for early cancer diagnosis and fluorescence-guided surgery.

Nitric oxide (NO) is a vital gaseous signal molecule and plays an important role in diverse physiological and pathological processes including regulation of vascular functions. Endoplasmic reticulum (ER) stress is caused by the accumulation of misfolded or unfolded protein in the ER. Besides, ER stress induced by NO can be involved in the pathogenesis of various vascular diseases. Unfortunately, to the best of our knowledge, no ER-targeting probe for NO is reported to study the relationship between ER stress and the level of NO in a biological system. Herein, an ER-targeted fluorescent probe named ER-Nap-NO for imaging of NO is designed and synthesized. ER-Nap-NO consists of three main parts: naphthalimide (two-photon fluorophore), o-phenylenediamino (NO recognition group), and methyl sulfonamide (ER-targetable group). The probe itself is nonfluorescent because a photoinduced electron transfer (PET) process exists. After the addition of NO, the PET process is inhibited and thus strong fluorescence is released. Moreover, the response mechanism is confirmed by 1H NMR and mass spectra and DFT calculation in detail. In addition, from the experimental results, we can conclude that the probe displays several obvious advantages including high sensitivity, selectivity, and ER-targetable ability. Based on these excellent properties, the probe is used for the two-photon imaging of exogenous and endogenous NO in ER of living cells. Most importantly, the ER-targetable probe has potential capability as a tool for investigating the level of NO during tunicamycin-induced ER stress in cells and tissues, which is beneficial for revealing the role of NO in ER-associated vascular diseases.