Development of Nucleoside Diphosphate-Bearing Fragile Histidine Triad-Imaging Fluorescence Probes with Well-Tuned Hydrophobicity for Intracellular Delivery

pH-triggered hydrophility-adjustable fluorescent probes for simultaneously imaging lipid droplets and lysosomes and the application in fatty liver detection

To study the collaboration between lipid droplets (LDs) and lysosomes, and the lipid change in nonalcoholic fatty liver disease (NAFLD), herein two pH-triggered hydrophility-adjustable fluorescent probes (LD-Lyso and LD-Lyso 1) are designed. The mechanism is based on cyclization and ring-opening with thorough consideration of pH and hydrophilic differences between LDs and lysosomes. Both of the two probes exist in ring-opening form and emit red fluorescence in acidic environment, while they exist in cyclized form and the emission is blueshifted in alkaline environment due to reduced conjugate planes. Moreover, LD-Lyso exhibits near infrared fluorescence at 740 nm under ring-opening form, which facilitates further cell, tissue, and in vivo imaging. The cell imaging results show that LD-Lyso can simultaneously target LDs and lysosomes by two different colors. Impressively, LD-Lyso cannot only detect NAFLD tissues from the normal tissue, but also distinguish different degrees of NAFLD tissues and mice, which provides a very promising tool for timely diagnosis of early NAFLD.

Dual-emissive europium doped UiO-66-based ratiometric light-up biosensor for highly sensitive detection of histidinemia biomarker

BACKGROUND

Lanthanide metal-organic frameworks (Ln-MOFs) are a kind of emerging crystalline porous materials with high fluorescence and easy-to-tunable properties, making them ideal for sensing applications. However, current Ln-MOFs based fluorescent probes are primarily single-emissive or fluorescence-quenched, which greatly limited the detection performances such as sensitivity, accuracy and repeatability, thereby hindering their applications in efficient target monitoring and related disease diagnosis. To address these issues, the reasonable design of Ln-MOFs equipped with dual fluorescence emissions and light-up mode is urgently needed for a high-performance biosensor.

RESULTS

A dual-emissive europium doped UiO-66 (Eu@UiO-66-NH2-PMA)-based ratiometric fluorescent biosensing platform was constructed for highly sensitive and selective detection of the histidinemia biomarker-histidine (His). Eu@UiO-66-NH2-PMA (pyromellitic acid abbreviated as PMA) was synthesized utilizing a post-synthetic modification method via coordination interactions between the free -COOH of UiO-66-NH2-PMA and Eu3+, which exhibited characteristic peaks of broad ligand emission and sharp Eu3+ emissions simultaneously. Considering that Cu2+ had the excellent fluorescence quenching ability toward Eu3+ and superior affinity with His, it was deliberately introduced into the Eu@UiO-66-NH2-PMA, acting as active sites for target His responsiveness. The Eu@UiO-66-NH2-PMA/Cu2+/His ternary competition system demonstrated a low detection limit of 74 nM, excellent selectivity and good anti-interference capability that allowed for sensitive analysis of His levels in milk and human serum samples.

SIGNIFICANCE

Attributing to the superior luminescent properties, good stability and self-calibration capability of Eu@UiO-66-NH2-PMA, the developed ratiometric light-up sensing platform enabled sensitive, selective and credible analysis of His in complex practical samples, which might provide an available tool for food nutrition guideline and diagnostic applications of His related diseases.

A Mitochondria-Targeted Fluorescent Probe for Monitoring NADPH Overproduction during Influenza Virus Infection

Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is an important cofactor in the progress of antioxidant synthesis and biosynthesis, and an abnormal NADPH level has been observed in many viral infection processes. However, efficient tools to monitor NADPH in living cells after viral infection have not been reported. In this work, we present a fluorescent probe, NAFP4, that could detect NADPH ex vivo with a low detection limit of 3.66 nM and image mitochondrial NADPH level changes in living cells. The probe exhibits excellent cell permeability, rapid reactivity, and high selectivity with minimal cytotoxicity. Using NAFP4, we reveal that the NADPH is overproduced in the host cells infected by influenza virus, which was caused by an elevated level of G6PDH during the virus infection. Moreover, there was positive association between the G6PDH level and virus replication. With the proposed probe NAFP4, our study highlights that the virus infection would influence the host metabolism in NADPH production and also suggests that G6PDH is expected to be a promising target for antiviral therapy.