Advanced NIR ratiometric probes for intravital biomedical imaging

Near-infrared fluorescence imaging technology (NIR-I region, 650–950 nm and NIR-II region, 1000–1700 nm), with deeper tissue penetration and less disturbance from auto-fluorescence than that in visible region (400−650 nm), is playing a more and more extensive role in the field of biomedical imaging. With the development of precise medicine, intelligent NIR fluorescent probes have been meticulously designed to provide more sensitive, specific and accurate feedback on detection. Especially, recently developed ratiometric fluorescence probes have been devoted to quantify physiological and pathological parameters with a combination of responsive fluorescence changes and self-calibration. Herein, we systemically introduced the construction strategies of NIR ratiometric fluorescence probes and their applications in biological imaging in vivo, such as molecular detection, pH and temperature measurement, drug delivery monitoring and treatment evaluation. We further summarized possible optimization on the design of ratiometric probes for quantitative analysis with NIR fluorescence, and prospected the broader optical applications of ratiometric probes in life science and clinical translation.

H2O2 and Engrailed 2 paracrine activity synergize to shape the zebrafish optic tectum

Although a physiological role for redox signaling is now clearly established, the processes sensitive to redox signaling remains to be identified. Ratiometric probes selective for H2O2 have revealed its complex spatiotemporal dynamics during neural development and adult regeneration and perturbations of H2O2 levels disturb cell plasticity and morphogenesis. Here we ask whether endogenous H2O2 could participate in the patterning of the embryo. We find that perturbations of endogenous H2O2 levels impact on the distribution of the Engrailed homeoprotein, a strong determinant of midbrain patterning. Engrailed 2 is secreted from cells with high H2O2 levels and taken up by cells with low H2O2 levels where it leads to increased H2O2 production, steering the directional spread of the Engrailed gradient. These results illustrate the interplay between protein signaling pathways and metabolic processes during morphogenetic events.

High-Throughput Image Analysis of Lipid-Droplet-Bound Mitochondria

ABSTRACTChanges to mitochondrial architecture are associated with various adaptive and pathogenic processes. However, quantification of changes to mitochondrial structures are limited by the yet unmet challenge of defining the borders of each individual mitochondrion within an image.. Here, we describe a novel method for segmenting Brown Adipose Tissue (BAT) images. We describe a granular approach to quantifying subcellular structures, particularly mitochondria in close proximity to lipid droplets, peri-droplet mitochondria. In addition, we lay out a novel machine-learning-based mitochondrial segmentation method that eliminates the bias of manual mitochondrial segmentation and improves object recognition compared to conventional thresholding analyses. By applying these methods, we discovered a significant difference between cytosolic and peridroplet BAT mitochondrial H2O2 production, and validated the machine learning algorithm in BAT via norepinephrine-induced mitochondrial fragmentation and comparing manual analyses to the automated analysis. This approach provides a higher-throughput analysis protocol to quantify ratiometric probes in subpopulations of mitochondria in adipocytes.

Designing enhanced and ratiometric probes for detecting OCl− based on substituents influencing the fluorescence of HBT and their application in strips and bioimaging

Based on strong electron-withdrawing effect of nitro group to powerfully influence the fluorescence of fluorophores, enhanced and ratiometric probes were synthesize to detect OCl− for portable test strips and cell imaging.

Controllable and robust dual-emissive quantum dot nanohybrids as inner filter-based ratiometric probes for visualizable melamine detection

A reliable ratiometric nanoprobe with two reversible fluorescent signal changes has been constructed for high-sensitivity visual melamine quantification.

FRET-based fluorescent ratiometric probes for the rapid detection of endogenous hydrogen sulphide in living cells

FRET strategy was adopted for designing ratiometric fluorescent H2S sensors using Coumarin-derived merocyanine fluorophore.