Fluorescence intensity and lifetime imaging of lipofuscin-like autofluorescence for label-free predicting clinical drug response in cancer.

Conventional techniques for in vitro cancer drug screening require labor-intensive formalin fixation, paraffin embedding, and dye staining of tumor tissues at fixed endpoints. This way of assessment discards the valuable pharmacodynamic information in live cells over time. Here, we found endogenous lipofuscin-like autofluorescence acutely accumulated in the cell death process. Its unique red autofluorescence could report the apoptosis without labeling and continuously monitor the treatment responses in 3D tumor-culture models. Lifetime imaging of lipofuscin-like red autofluorescence could further distinguish necrosis from apoptosis of cells. Moreover, this endogenous fluorescent marker could visualize the apoptosis in live zebrafish embryos during development. Overall, this study validates that lipofuscin-like autofluorophore is a generic cell death marker. Its characteristic autofluorescence could label-free predict the efficacy of anti-cancer drugs in organoids or animal models.

Accelerating precision anti-cancer therapy by time-lapse and label-free 3D tumor slice culture platform.

The feasibility of personalized medicine for cancer treatment is largely hampered by costly, labor-intensive and time-consuming models for drug discovery. Herein, establishing new pre-clinical models to tackle these issues for personalized medicine is urgently demanded. Methods: We established a three-dimensional tumor slice culture (3D-TSC) platform incorporating label-free techniques for time-course experiments to predict anti-cancer drug efficacy and validated the 3D-TSC model by multiphoton fluorescence microscopy, RNA sequence analysis, histochemical and histological analysis. Results: Using time-lapse imaging of the apoptotic reporter sensor C3 (C3), we performed cell-based high-throughput drug screening and shortlisted high-efficacy drugs to screen murine and human 3D-TSCs, which validate effective candidates within 7 days of surgery. Histological and RNA sequence analyses demonstrated that 3D-TSCs accurately preserved immune components of the original tumor, which enables the successful achievement of immune checkpoint blockade assays with antibodies against PD-1 and/or PD-L1. Label-free multiphoton fluorescence imaging revealed that 3D-TSCs exhibit lipofuscin autofluorescence features in the time-course monitoring of drug response and efficacy. Conclusion: This technology accelerates precision anti-cancer therapy by providing a cheap, fast, and easy platform for anti-cancer drug discovery.

Transition metal dichalcogenide quantum dots: synthesis, photoluminescence and biological applications.

The unique electronic, physical and chemical properties of nanostructured transition metal dichalcogenide (TMD) materials have received great attention, specifically, with the decrease of size to several nanometers, particles named TMD quantum dots (QDs). The inherent properties of TMD QDs make them promising for a variety of applications, including catalytic, luminescence and biomedical. In this review, we first briefly introduce the controlled synthesis of TMD QDs using mechanical exfoliation, ion intercalation-assisted liquid exfoliation, free radical and electrochemical shear and hydrothermal/solvothermal reaction. We then summarize recent progress on chemical and biological applications of TMD QDs in detail.

Black Phosphorus Quantum Dots as the Ratiometric Fluorescence Probe for Trace Mercury Ion Detection Based on Inner Filter Effect.

In this work, a novel ratiometric fluorescence sensor has been constructed for the selective and sensitive detection of Hg2+, which is based on the inner filter effect (IFE) of tetraphenylporphyrin tetrasulfonic acid (TPPS) toward black phosphorus quantum dots (BP QDs). Highly fluorescent BP QDs were successfully synthesized from bulk BP by sonication-assisted solvothermal method via a top-down route. In the presence of Hg2+, the IFE originating from spectral overlap between the excitation of BP QDs and the absorption of TPPS is inhibited and the fluorescence of BP QDs is restored. At the same time, the red fluorescence of TPPS is quenched due to its coordination with Mn2+. These phenomena result from the rapid coordination between Mn2+ and TPPS in the presence of Hg2+, which leads to the dramatic decrease of the absorption of TPPS. On the basis of these findings, we design a ratiometric fluorescence sensor for the detection of Hg2+. The as-constructed sensor reveals a good linear response to Hg2+ ranging from 1 to 60 nM with a detection limit of 0.39 nM. Furthermore, the sensing assay is applicable to detecting Hg2+ in real samples.

Highly Fluorescent Polyimide Covalent Organic Nanosheets as Sensing Probes for the Detection of 2,4,6-Trinitrophenol.

A new fluorescent polyimide covalent organic framework (PI-COF) has been successfully synthesized through solvothermal route using tetra(4-aminophenyl) porphyrin and perylenetracarboxylic dianhydride, which possesses porous crystalline and excellent thermal stability (>500 °C). Furthermore, few-layered PI covalent organic nanosheets (PI-CONs) can be easily obtained from the fluorescent PI-COF through a facile liquid phase exfoliation approach, which were confirmed by atomic force microscopy and transmission electron microscopy analysis. It is interesting that the fluorescent intensity of PI-CONs is obviously enhanced relative to that of PI-COF. The PI-CONs have been successfully utilized as an efficient fluorescent probe for the highly sensitive and selective detection of 2,4,6-trinitrophenol (TNP). The mechanism might be attributed to the combination of electron transfer and inner filter effect based on DFT calculations and spectral overlap data. The system exhibits a good linear response toward TNP over the range from 0.5 to 10 µM with a detection limit of 0.25 µM.

One-Step Synthesis of Water-Soluble MoS2 Quantum Dots via a Hydrothermal Method as a Fluorescent Probe for Hyaluronidase Detection.

In this work, a bottom-up strategy is developed to synthesize water-soluble molybdenum disulfide quantum dots (MoS2 QDs) through a simple, one-step hydrothermal method using ammonium tetrathiomolybdate [(NH4)2MoS4] as the precursor and hydrazine hydrate as the reducing agent. The as-synthesized MoS2 QDs are few-layered with a narrow size distribution, and the average diameter is about 2.8 nm. The resultant QDs show excitation-dependent blue fluorescence due to the polydispersity of the QDs. Moreover, the fluorescence can be quenched by hyaluronic acid (HA)-functionalized gold nanoparticles through a photoinduced electron-transfer mechanism. Hyaluronidase (HAase), an endoglucosidase, can cleave HA into proangiogenic fragments and lead to the aggregation of gold nanoparticles. As a result, the electron transfer is blocked and fluorescence is recovered. On the basis of this principle, a novel fluorescence sensor for HAase is developed with a linear range from 1 to 50 U/mL and a detection limit of 0.7 U/mL.

A facile and one-step ethanol-thermal synthesis of MoS2 quantum dots for two-photon fluorescence imaging.

Two-photon fluorescent (TPF) molybdenum disulfide quantum dots (MoS2 QDs) were synthesized through a facile and one-step solvothermal approach. The MoS2 QDs exhibit small size and high stability. Because of their low toxicity and TPF ability, the MoS2 QDs are successfully applied in two-photon fluorescence bio-imaging.