Chlorophyll Fluorescence Imaging Uncovers Photosynthetic Fingerprint of Citrus Huanglongbing

Huanglongbing (HLB) is one of the most destructive diseases of citrus, which has posed a serious threat to the global citrus production. This research was aimed to explore the use of chlorophyll fluorescence imaging combined with feature selection to characterize and detect the HLB disease. Chlorophyll fluorescence images of citrus leaf samples were measured by an in-house chlorophyll fluorescence imaging system. The commonly used chlorophyll fluorescence parameters provided the first screening of HLB disease. To further explore the photosynthetic fingerprint of HLB infected leaves, three feature selection methods combined with the supervised classifiers were employed to identify the unique fluorescence signature of HLB and perform the three-class classification (i.e., healthy, HLB infected, and nutrient deficient leaves). Unlike the commonly used fluorescence parameters, this novel data-driven approach by using the combination of the mean fluorescence parameters and image features gave the best classification performance with the accuracy of 97%, and presented a better interpretation for the spatial heterogeneity of photochemical and non-photochemical components in HLB infected citrus leaves. These results imply the potential of the proposed approach for the citrus HLB disease diagnosis, and also provide a valuable insight for the photosynthetic response to the HLB disease

Bright Near-infrared Anti-Stokes Fluorescence of ICG under Low Power CW Laser Excitation and its Applications in Bioimaging

AbstractAnti-Stokes fluorescence was observed in ICG, a molecule approved by the FDA for clinical use. The wavelengths of its fluorescence are mainly located in the near-infrared band of 800 nm~900 nm, with a high quantum yield up to 8%. In order to know its generation mechanism, based on multi-photon absorption (MPA) theory, thermally activated delayed fluorescence (TADF) theory and hot band absorption theory, its power dependence, temperature dependence of absorption spectra and fluorescence spectra, and fluorescence lifetime were measured. Its generation mechanism was finally determined to be hot band absorption process. Since ICG showed bright anti-Stokes fluorescence in near-infrared region, which offers substantially longer penetration depth in biological tissues than visible light, excellent photostability and biosafety, we applied it to in vivo imaging and compared it with upconversion nanoparticles (UCNPs). The result is that ICG exhibited much stronger fluorescence than UCNPs, providing more anatomical information of samples. This contributes to a better choice for anti-Stokes fluorescence bioimaging.</jats:p

Protein enhanced NIR-IIb emission of indocyanine green for functional bioimaging

AbstractFluorescence imaging performed in the 1500-1700 nm spectral range (labeled as near-infrared IIb, NIR-IIb) promises high imaging contrast and spatial resolution for its little photon scattering effect and minimum auto-fluorescence. Though inorganic and organic probes have been developed for NIR-IIb bioimaging, most are in preclinical stage, hampering further clinical application. Herein, we showed that indocyanine green (ICG), an US Food and Drug Administration (FDA)-approved agent, exhibited remarkable amount of NIR-IIb emission when dissolved into different protein solutions, including human serum albumin, rat bile, and fetal bovine serum. We performed fluorescence imaging in NIR-IIb window to visualize structures of lymph system, extrahepatic biliary tract and cerebrovascular. Results demonstrated that proteins promoted NIR-IIb emission of ICG in vivo and that NIR-IIb imaging with ICG preserved higher signal-to-background ratio (SBR) and spatial resolution compared with the conventional near-infrared II (NIR-II) fluorescence imaging. Our findings confirm that NIR-IIb fluorescence imaging can be successfully performed using the clinically approved agent ICG. Further clinical application in NIR-IIb region would hopefully be carried out with appropriate ICG-protein solutions.</jats:p

A simple strategy for the efficient design of mitochondria-targeting NIR-II phototheranostics

The pursuit of phototheranostic agents with near-infrared II emission, high photothermal conversion efficiency and the robust generation of reactive oxygen species (ROS) in the aggregated state is always in high demand but remains a big challenge.</jats:p

Lipid droplets imaging with three-photon microscopy

Lipid droplets (LDs) participate in many physiological processes, the abnormality of which will cause chronic diseases and pathologies such as diabetes and obesity. It is crucial to monitor the distribution of LDs at high spatial resolution and large depth. Herein, we carried three-photon imaging of LDs in fat liver. Owing to the large three-photon absorption cross-section of the luminogen named NAP-CF3 (1:67 x 10(-79) cm(6) s(2)), three-photon fluorescence fat liver imaging reached the largest depth of 80 mu m. Fat liver diagnosis was successfully carried out with excellent performance, providing great potential for LDs-associated pathologies research

The effects of the miR-21/SMAD7/TGF-β pathway on Th17 cell differentiation in COPD

AbstractChronic obstructive pulmonary disease (COPD) is a complex disease with multiple etiologies, while smoking is the most established one. The present study investigated the modulation of T-helper 17 (Th17) cell differentiation by the miR-21/Smad7/TGF-β pathway, and their roles in COPD. Lung tissues were obtained from lung cancer patients with or without COPD who underwent lobotomy and the levels of miR-21, TGF-β/Smad signaling molecules, RORγT, and other Th17-related cytokines were detected. Mouse COPD models were built by exposing both wild-type (WT) and miR-21−/− mice to cigarette smoke (CS) and cigarette smoke extract (CSE) intraperitoneal injection. Isolated primary CD4+ T cells were treated with either CS extract, miR-21 mimics or inhibitors, followed by measuring Th17 cells markers and the expression of TGF-β/Smad signaling molecules and RORγT. Increased levels of miR-21, Smad7, phosphorylated (p)-Smad2, p-Smad3, TGF-β, and Th17-related cytokines was detected in the lungs of COPD patients. Lung function in modeled WT mice, but not miR-21−/− ones, deteriorated and the number of inflammatory cells in the lung tissues increased compared to the control WT-mice. Moreover, primary CD4+ lymphocytes tend to differentiate into Th17 cells after the treatment with CSE or miR-21 mimics, and the expression of RORγT and the TGF-β/Smad signaling were all increased, however miR-21 inhibitors worked reversely. Our findings demonstrated that Th17 cells increased under COPD pathogenesis and was partially modulated by the miR-21/Smad7/TGF-β pathway.</jats:p

Characterization and Detection of Leaf Photosynthetic Response to Citrus Huanglongbing from Cool to Hot Seasons in Two Orchards

HighlightsAn abnormal accumulation of sucrose and glucose was found in HLB-infected leaves, and it presented a similar pattern in different orchards from cool to hot seasons.A decreasing value of the actual quantum yield of PSII (FPSII) in HLB-infected leaves was mainly related to an increase of non-regulated energy quenching (FNO) due to the irreversible damage of PSII.Chlorophyll fluorescence imaging combined with a random forest was able to identify HLB at the asymptomatic stage.Abstract Citrus Huanglongbing (HLB) poses a serious threat to citrus production. This research aimed to explore chlorophyll fluorescence imaging for characterizing the photosynthetic response to HLB-infected citrus leaves in different orchards and seasons. Chlorophyll fluorescence images of citrus leaves were acquired with an in-house chlorophyll fluorescence imaging system. It was found that sucrose and glucose accumulated earlier than starch in HLB-infected leaves, and a similar carbohydrate metabolic pattern was observed in HLB-infected leaves grown in different orchards from cool to hot seasons. The pathogen damaged the thylakoid structure of chloroplasts with a higher value of Fo. It decreased photosynthetic activity of the host by reducing the number of active photosynthetic centers and the maximum quantum yield of PSII (Fv/Fm) with lower values of Fv/Fo and Fv/Fm. Additionally, the pathogen modified the allocation of excitation energy in citrus leaves by reducing the actual quantum yield of PSII (FPSII) due to an increase of non-regulated energy quenching (FNO), which indicated irreversible PSII damage before symptom development. Moreover, photosynthetic signatures combined with the random forest method were able to identify HLB in the asymptomatic stage with an overall accuracy of 91.8%. These results demonstrated the potential of chlorophyll fluorescence imaging for evaluating the photosynthetic response to HLB as well as disease diagnosis. Keywords: Carbohydrate metabolism, Chlorophyll fluorescence imaging, Citrus Huanglongbing, Photosynthetic efficiency, Random forest model.</jats:p

Quantum dots assisted in vivo two-photon microscopy with NIR-II emission

With the advantages of high resolution and deep penetration depth, two-photon excited NIR-II (900–1880 nm) fluorescence (2PF) microscopic bioimaging is promising. However, due to the lack of imaging systems and suitable probes, few such works, to our best knowledge, were demonstrated utilizing NIR-II excitation and NIR-II fluorescence simultaneously. Herein, we used aqueously dispersible PbS/CdS quantum dots with bright NIR-II fluorescence as the contrast agents. Under the excitation of a 1550 nm femtosecond (fs) laser, they emitted bright 2PF in the NIR-II region. Moreover, a 2PF lifetime imaging microscopic (2PFLIM) system was implemented, and in vivo 2PFLIM images of mouse brain blood vessels were obtained for the first time to our best knowledge. To improve imaging speed, an in vivo two-photon fluorescence microscopy (2PFM) system based on an InGaAs camera was implemented, and in vivo 2PFM images of QDs-stained mouse brain blood vessels were obtained.</jats:p