Fluorinated Iron Metal-Organic Frameworks for Activatable 19F Magnetic Resonance Imaging and Synergistic Therapy of Tumors.

Due to their appealing physiochemical properties, metal-organic frameworks (MOFs) have been widely employed in biomedical fields. In this study, we utilize ferric ions and fluorine-containing organic ligands as both structural and functional units to develop a stimulus-responsive nanoagent, 19FIMOF-TA nanoparticles, for activatable 19F magnetic resonance imaging (MRI) and synergistic therapy of tumors. This nanoagent could respond to excess GSH in a tumor microenvironment, discharging fluorinated organic ligands and reduced ferrous ions. The release of these fluorine-containing small molecules results in boosting of the 19F MRI signals, which could be further enhanced by the photothermal effect of this nanoagent to achieve a responsive cascaded amplification of 19F MRI signals for tumor visualization. Meanwhile, ferroptosis promoted by the ferrous ions leads to significant tumor cell death, which is synergistically aggravated by the photothermal effect. The encouraging results illustrate the promising potential of our nanoagent for effective tumor imaging and combinative cancer therapy.

Glycan Metabolic Fluorine Labeling for In Vivo Visualization of Tumor Cells and In Situ Assessment of Glycosylation Variations.

The abnormality in the glycosylation of surface proteins is critical for the growth and metastasis of tumors and their capacity for immunosuppression and drug resistance. This anomaly offers an entry point for real-time analysis on glycosylation fluctuations. In this study, we report a strategy, glycan metabolic fluorine labeling (MEFLA), for selectively tagging glycans of tumor cells. As a proof of concept, we synthesized two fluorinated unnatural monosaccharides with distinctive 19 F chemical shifts (Ac4 ManNTfe and Ac4 GalNTfa). These two probes could undergo selective uptake by tumor cells and subsequent incorporation into surface glycans. This approach enables efficient and specific 19 F labeling of tumor cells, which permits in vivo tracking of tumor cells and in situ assessment of glycosylation changes by 19 F MRI. The efficiency and specificity of our probes for labeling tumor cells were verified in vitro with A549 cells. The feasibility of our method was further validated with in vivo experiments on A549 tumor-bearing mice. Moreover, the capacity of our approach for assessing glycosylation changes of tumor cells was illustrated both in vitro and in vivo. Our studies provide a promising means for visualizing tumor cells in vivo and assessing their glycosylation variations in situ through targeted multiplexed 19 F MRI.

Macrophage Reprogramming via Targeted ROS Scavenging and COX-2 Downregulation for Alleviating Inflammation.

Inflammation-related diseases affect large populations of people in the world and cause substantial healthcare burdens, which results in significant costs in time, material, and labor. Preventing or relieving uncontrolled inflammation is critical for the treatment of these diseases. Herein, we report a new strategy for alleviating inflammation by macrophage reprogramming via targeted reactive oxygen species (ROS) scavenging and cyclooxygenase-2 (COX-2) downregulation. As a proof of concept, we synthesize a multifunctional compound named MCI containing a mannose-based macrophage targeting moiety, an indomethacin (IMC)-based segment for inhibiting COX-2, and a caffeic acid (CAF)-based section for ROS clearance. As revealed by a series of in vitro experiments, MCI could significantly attenuate the expression of COX-2 and the level of ROS, leading to M1 to M2 macrophage reprogramming, as evidenced by the reduction and the elevation in the levels of pro-inflammatory M1 markers and anti-inflammatory M2 markers, respectively. Furthermore, in vivo experiments show MCI's promising therapeutic effects on rheumatoid arthritis (RA). Our work illustrates the success of targeted macrophage reprogramming for inflammation alleviation, which sheds light on the development of new anti-inflammatory drugs.

Metabolic fluorine labeling and hotspot imaging of dynamic gut microbiota in mice.

Real-time localization and microbial activity information of indigenous gut microbiota over an extended period of time remains a challenge with existing visualizing methods. Here, we report a metabolic fluorine labeling (MEFLA)-based strategy for monitoring the dynamic gut microbiota via 19F magnetic resonance imaging (19F MRI). In situ labeling of different microbiota subgroups is achieved by using a panel of peptidoglycan-targeting MEFLA probes containing 19F atoms of different chemical shifts, and subsequent real-time in vivo imaging is accomplished by multiplexed hotspot 19F MRI with high sensitivity and unlimited penetration. Using this method, we realize extended visualization (>24 hours) of native gut microbes located at different intestinal sections and semiquantitative analysis of their metabolic dynamics modulated by various conditions, such as the host death and different ß-lactam antibiotics. Our strategy holds great potential for noninvasive and real-time assessing of the metabolic activities and locations of the highly dynamic gut microbiota.

Bio-orthogonal Metabolic Fluorine Labeling Enables Deep-Tissue Visualization of Tumor Cells In Vivo by 19F Magnetic Resonance Imaging.

The high resolution, deep penetration, and negligible biological background of 19F magnetic resonance imaging (MRI) makes it a potential means for imaging various biological targets in vivo. However, the limited targeting strategies of current 19F MRI probes significantly restrict their applications for in vivo tracking of low-abundance targets and specific biological processes, which greatly stimulates the investigations on new targeting methods for 19F MRI. Herein, we report a strategy, termed as bio-orthogonal metabolic fluorine labeling, for selective cellular 19F labeling, which permits in vivo imaging of tumor cells with high specificity. This strategy exploits the display of azido groups on the cell surface via selective uptake and metabolic engineering of tetra-acetylated N-azidoacetylmannosamine (Ac4ManAz) by cancer cells and subsequent rapid and specific bio-orthogonal ligation between azido and cyclootynyl groups to incorporate 19F-containing moieties on the surface of cancer cells. We validated the feasibility of this method on the cellular level with A549 and HepG2 cells and further illustrated the application of this method for in vivo deep-tissue visualization of cancer cells with A549 tumor-bearing BALB/c mice using hot spot 19F MRI. Our strategy expands the arsenal for targeted 19F MRI and provides a promising method for imaging biological targets in living subjects with high tissue penetration and low biological background.

19 F Barcoding Enables Multiplex Detection of Biomarkers Associated with Organ Injury and Cancer.

Simultaneous detection of multiple biomarkers in complex environments is critical for the in-depth exploration of different biological processes, which is challenging for many current analytical methods due to various limitations. Herein, we report a strategy of 19 F barcoding which takes the advantages of 19 F's high magnetic resonance (MR) sensitivity, prompt signal response to environmental changes, negligible biological background, quantitative signal output, and multiplex capacity. A set of 19 F-barcoded sensors responding to different biomarkers involved in organ injury and cancer are designed, synthesized, and characterized. With these sensors, we accomplish concurrent assessment of different biomarkers in the samples collected from the mice with drug-induced liver/kidney injury or tumor, illustrating the feasibility of this approach for multiplexed detection of different biomarkers in complex environments during various biological processes.

An Activatable 19 F MRI Molecular Probe for Sensing and Imaging of Norepinephrine.

Norepinephrine (NE), acting as both a neurotransmitter and hormone, plays a significant role in regulating the action of the brain and body. Many studies have demonstrated a strong correlation between mental disorders and aberrant NE levels. Therefore, it is of urgent demand to develop in vivo analytical methods of NE for diagnostic assessment and mechanistic investigations of mental diseases. Herein, we report a 19 F MRI probe (NRFP) for sensing and imaging NE, which is constructed by conjugating a gadolinium chelate to a fluorine-containing moiety through a NE-responsive aromatic thiocarbonate linkage. The capacity and specificity of NRFP for detecting NE is validated with in vitro detecting/imaging experiments. Furthermore, the feasibility of NRFP for visualizing NE in animals is illustrated by ex vivo and in vivo imaging experiments, demonstrating the promising potential of NRFP for selective detection and specific imaging of NE in deep tissues of living subjects.

Protective Effect and Mechanism of Soybean Insoluble Dietary Fiber on the Color Stability of Malvidin-3-O-glucoside.

Anthocyanins have great health benefits, especially malvidin. Vitis amurensis Rupr are rich in malvidin, and malvidin-3-O-glucoside (Mv3G) monomer is the most abundant. However, natural anthocyanins are unstable, which limits their wide application in the food field. Soybean insoluble dietary fiber (SIDF) has high stability, and it can be used as an inert substrate to construct a stable system, which may improve the stability of anthocyanins. The optimal condition to construct a stable system of SIDF and Mv3G at pH 3.0 was determined by an orthogonal experiment. The results indicated that SIDF effectively improved the stability of Mv3G under different pH values (1.0~7.0), high temperature (100 °C for 100 min), and sunlight (20 ± 2 °C for 30 d) conditions. The absorption peak intensity of the UV-VIS spectrum of SIDF-Mv3G was enhanced, which indicated that there was interaction between SIDF and Mv3G. Fourier transform infrared spectroscopy analyses revealed that the -OH stretching vibration peak of SIDF-Mv3G was changed, which indicated that the interaction between SIDF and Mv3G was due to hydrogen bonding. X-ray diffraction analysis showed that the crystalline morphology of SIDF was opened, which was combined with Mv3G, and SIDF made Mv3G change to a more stable state. Scanning electron microscope analysis showed that SIDF and Mv3G were closely combined to form an inclusion complex. Overall, this study provides valuable information for enhancing the color stability of anthocyanins, which will further expand the application of anthocyanins in the food field.

Drought soil legacy alters drivers of plant diversity-productivity relationships in oldfield systems.

Ecosystem functions are threatened by both recurrent droughts and declines in biodiversity at a global scale, but the drought dependency of diversity-productivity relationships remains poorly understood. Here, we use a two-phase mesocosm experiment with simulated drought and model oldfield communities (360 experimental mesocosms/plant communities) to examine drought-induced changes in soil microbial communities along a plant species richness gradient and to assess interactions between past drought (soil legacies) and subsequent drought on plant diversity-productivity relationships. We show that (i) drought decreases bacterial and fungal richness and modifies relationships between plant species richness and microbial groups; (ii) drought soil legacy increases net biodiversity effects, but responses of net biodiversity effects to plant species richness are unaffected; and (iii) linkages between plant species richness and complementarity/selection effects vary depending on past and subsequent drought. These results provide mechanistic insight into biodiversity-productivity relationships in a changing environment, with implications for the stability of ecosystem function under climate change.

Effect of Soybean Protein Isolate-7s on Delphinidin-3-O-Glucoside from Purple Corn Stability and Their Interactional Characterization.

Anthocyanins are abundant in purple corn and beneficial to human health. Soybean protein isolate-7s (SPI-7s) could enhance the stability of anthocyanins. The stable system of soybean protein isolate-7s and delphinidin-3-O-glucoside complex (SPI-7s-D3G) was optimized using the Box-Behnken design at pH 2.8 and pH 6.8. Under the condition of pH 2.8, SPI-7s effectively improved the sunlight-thermal stabilities of delphinidin-3-O-glucoside (D3G). The thermal degradation of D3G conformed to the first order kinetics within 100 min, the negative enthalpy value and positive entropy value indicated that interaction was caused by electrostatic interaction, and the negative Gibbs free energy value reflected a spontaneous interaction between SPI-7s and D3G. The interaction of SPI-7s-D3G was evaluated by ultraviolet visible spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy. The results showed that the maximum absorption peak was redshifted with increasing the α-helix content and decreasing the ß-sheet contents, and D3G quenched the intrinsic fluorescence of SPI-7s by static quenching. There was one binding site in the SPI-7s and D3G stable system. The secondary structure of SPI-7s had changed and the complex was more stable. The stabilized SPI-7s-D3G will have broad application prospects in functional foods.

Highly spatial variation of soil microbial respiration and temperature sensitivity in a subtropical forest.

Quantifying the spatial variation and drivers of microbe-driven soil carbon (C) decomposition (also called soil microbial respiration, MR) and its temperature sensitivity (Q10) is crucial for reducing the uncertainty in modelling the terrestrial C cycle under global warming. To this end, most previous studies sampled soils from multiple sites at regional scales and incubated them at the same temperature level in the laboratory. However, this unified incubation temperature is too warm to the cold sites, and too cold to the warm sites, thus causing a large bias in the MR and Q10 estimations. Here, we conducted fine scale intensive sampling (194 soil samples) and measurements within a 4-ha subtropical forest plot to examine the underlying mechanisms driving the spatial pattern of MR and Q10. Our results showed that both MR and Q10 varied spatially within subtropical forests. The fine scale variation of MR was dominated by soil nitrogen concentration and slope position, and Q10 was dominated by soil fungi abundance. Overall, the 35 investigated biotic and abiotic factors explained 38% of the spatial variation of MR and 9% of the spatial variation of Q10 in the subtropical forest. This suggests that the fine scale variation of soil C dynamics is much more complex than that at the regional scale reported in previous studies, which should be considered in the assessments of terrestrial soil C cycles.

Activatable Multiplexed 19F Magnetic Resonance Imaging Visualizes Reactive Oxygen and Nitrogen Species in Drug-Induced Acute Kidney Injury.

In vivo levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are critical to many physiological and pathological processes. Because of the distinct differences in their biological generation and effects, simultaneously visualizing both of them could help deepen our insights into the mechanistic details of these processes. However, real-time and deep-tissue imaging and differentiation of ROS- and RNS-related molecular events in living subjects still remain a challenge. Here, we report the development of two activatable 19F magnetic resonance imaging (MRI) molecular probes with different 19F chemical shifts and specific responsive behaviors for simultaneous in vivo detection and deep-tissue imaging of O2•- and ONOO-. These probes are capable of real-time visualization and differentiation of O2•- and ONOO- in living mice with drug-induced acute kidney injury by interference-free multiplexed hot-spot 19F MRI, illustrating the potential of this technique for background-free real-time imaging of diverse biological processes, accurate diagnosis of various diseases in deep tissues, and rapid toxicity evaluation of assorted drugs.

Deep-tissue real-time imaging of drug-induced liver injury with peroxynitrite-responsive 19F MRI nanoprobes.

Peroxynitrite is an important biomarker for assessing drug-induced liver injury (DILI), which is critical for the development and use of drugs. Herein, we report the development of peroxynitrite-responsive self-assembled 19F MRI nanoprobes, which enable the sensitive imaging of peroxynitrite in L02 cells subjected to oxidative stress and living mice with DILI.

Identification of Stabilization of Malvid Anthocyanins and Antioxidant Stress Activation via the AMPK/SIRT1 Signaling Pathway.

Vitis amurensis Rupr. "Beibinghong" is abundant in anthocyanins, including malvidin (Mv), malvidin-3-glucoside (Mv3G), and malvidin-3,5-diglucoside (Mv35 G). Anthocyanins offer nutritional and pharmacological effects, but their stability is poor. Interaction of malvid anthocyanins with caffeic acid through ultrahigh pressure technology produces stable anthocyanin derivatives. This study aims to identify the structure of stable mallow-like anthocyanins and to determine the effect of these stable anthocyanins on human umbilical vein endothelial cells (HUVECs) with H2O2-induced oxidative damage and the signaling pathway involved. The products of malvid anthocyanins and caffeic acid bonding were identified and analyzed using ultra-high performance liquid chromatography-quadrupole-Orbitrap mass spectrometry (UPLC-Q-Orbitrap MS/MS). The bonding products were malvidin-3-O-guaiacol (Mv3C), malvidin-3-O-(6″-O-caffeoyl)-glucoside (Mv3CG), and malvidin-3-O-(6″-O-caffeoyl)-5-diglucoside (Mv3C5G). An oxidative stress injury model in HUVECs was established using H2O2 and treated with Mv, Mv3G, Mv35 G, Mv3C, Mv3CG, and Mv3C5G at different concentrations (10, 50, and 100 µmol/L). Results showed that the above compound concentrations can significantly increase cell proliferation rate and reduce intracellular reactive oxygen species at 100 µmol/L. The effects of the most active products Mv and Mv3C on the AMP-activated protein (AMPK)/silencing information regulator-1 (SIRT1) pathway were analyzed. Results showed that Mv and Mv3C significantly increased SOD activity in the cells and significantly upregulated the expression of SIRT1 mRNA, SIRT1, and p-AMPK protein. However, they did not significantly change the expression of AMPK protein. After the silent intervention of siRNA in SIRT1 gene expression, the upregulation of SIRT1 and p-AMPK protein by Mv and Mv3C was significantly inhibited. These results indicate that stabilization malvid anthocyanins exerts an antioxidant activity via the AMPK/SIRT1 signaling pathway.

A DNA-functionalized biomass nanoprobe for the targeted photodynamic therapy of tumor and ratiometric fluorescence imaging-based visual cancer cell identification/antitumor drug screening.

Survivin is widely expressed in tumor tissue, in which the in situ ratiometric fluorescence imaging of intracellular survivin mRNA can provide accurate information for the diagnosis and treatment of cancers, as well as the screening of antitumor drugs. However, the development of a nanoprobe that can be used simultaneously in the diagnosis and treatment of tumors and the screening of antitumor drugs remains a challenge. In an effort to address these requirements, a multifunctional biomass nanoprobe was developed for the photodynamic therapy (PDT) of tumors as well as cancer cell identification and antitumor drug screening based on the ratiometric fluorescence imaging of intracellular survivin mRNA. This nanoprobe was assembled from near-infrared (NIR) biomass quantum dots (BQDs), single-stranded DNA and NIR dye (dylight680) labeled single-stranded DNA. The BQDs contain a large number of chlorophyll molecules, meaning that they can produce a large amount of singlet oxygen under NIR light irradiation, thus realizing the PDT of a tumor. However, the specific binding of the nanoprobe to intracellular survivin mRNA causes the release of dylight680 and reduces the fluorescence resonance energy transfer (FRET) efficiency between the BQDs and dylight680 in the probe, thereby achieving the ratiometric fluorescence imaging of survivin mRNA. Therefore, the prepared nanoprobe can not only be used in the diagnosis of cancers, but also in the targeted PDT of tumors.

Limiting similarity shapes the functional and phylogenetic structure of root neighborhoods in a subtropical forest.

Environmental filtering and limiting similarity mechanisms can simultaneously structure community assemblages. However, how they shape the functional and phylogenetic structure of root neighborhoods remains unclear, hindering the understanding of belowground community assembly processes and diversity maintenance. In a 50-ha plot in a subtropical forest, China, we randomly sampled > 2700 root clusters from 625 soil samples. Focusing on 10 root functional traits measured on 76 woody species, we examined the functional and phylogenetic structure of root neighborhoods and linked their distributions with environmental cues. Functional overdispersion was pervasive among individual root traits (50% of the traits) and accentuated when different traits were combined. Functional clustering (20% of the traits) seemed to be associated with a soil nutrient gradient with thick roots dominating fertile areas whereas thin roots dominated infertile soils. Nevertheless, such traits also were sorted along other environmental cues, showing multidimensional adaptive trait syndromes. Species relatedness also was an important factor defining root neighborhoods, resulting in significant phylogenetic overdispersion. These results suggest that limiting similarity may drive niche differentiation of coexisting species to reduce competition, and that alternative root strategies could be crucial in promoting root neighborhood resource use and species coexistence.

Fluorinated Gadolinium Chelate-Grafted Nanoconjugates for Contrast-Enhanced T1-Weighted 1H and pH-Activatable 19F Dual-Modal MRI.

Magnetic resonance imaging (MRI) is one of the most popular imaging techniques, which offers an ionization-free noninvasive means for imaging deep tissues with high resolution. Conventional 1H MRI is well versed in providing detailed anatomical information but suffers from low contrast for tracking biomarkers because of the abundance of water in living bodies. 19F MRI with negligible endogenous background interference enables highly sensitive detection of biomolecular targets and has drawn extensive attention from the biomedical research community recently. However, this imaging technique only acquires the "hot spot" signals of exogenous 19F nucleus-containing imaging probes. 1H/19F MRI dual-modal imaging is expected to compensate for the limitations of either single-modal imaging and accomplish synergistic morphological and physiological imaging. Herein, we report a highly biocompatible nanoconjugate composed of pH-responsive 19F nucleus-bearing Gd3+ chelates, which enables significant contrast enhancement for T1-weighted 1H MRI and permits pH-responsive activation of 19F signals for 19F MRI, providing both clear anatomical details of living bodies and the biorelevant molecular information with low background interference. This nanoconjugate facilitates sensitive and accurate detection of tumors with contrast-enhanced T1-weighted 1H and pH-activatable 19F dual-modal imaging on a single MRI scanner.

Near-Infrared Dual-Emission Ratiometric Fluorescence Imaging Nanoprobe for Real-Time Tracing the Generation of Endogenous Peroxynitrite in Single Living Cells and In Vivo.

Peroxynitrite (ONOO-) is a highly reactive nitrogen species with potent oxidant and nitrating properties. Its excessive generation can cause DNA and protein damage, thereby contributing to cell injury, and it is closely related to the development of many diseases. Thus, there is an urgent need for a reliable method to determine changes in the steady-state levels of ONOO- in vivo. Ratiometric imaging, due to its built-in self-calibration system, can reduce artifacts and enable reliable in vivo imaging. In this study, we designed and prepared near-infrared (NIR) biomass quantum dots (NI-BQDs) and covalently coupled them with the NIR dye Cyanine7 (Cy7) to construct an NIR dual-emission nanoprobe (NI-BQD-Cy7) for real-time tracing the generation of endogenous ONOO- in single living cells and in vivo by ratiometric fluorescence imaging. NI-BQD-Cy7 exhibited high detection sensitivity and selectivity for ONOO- in the mitochondria. Additionally, it can produce dual NIR fluorescence emission, thus allowing in situ ratiometric fluorescence imaging to real-time trace the generation and concentration changes of ONOO- in vivo. The application of the proposed NIR dual-emission nanoprobe can provide accurate information for the study of the biological function of ONOO- in single living cells and in vivo, and it is very useful to explain the mechanism of cell damage caused by ONOO-.