Tingting Zhao

Real-Time Discrimination and Versatile Profiling of Spontaneous Reactive Oxygen Species in Living Organisms with a Single Fluorescent Probe.

Fluorescent probes are powerful tools for the investigations of reactive oxygen species (ROS) in living organisms by visualization and imaging. However, the multiparallel assays of several ROS with multiple probes are often limited by the available number of spectrally nonoverlapping chromophores together with large invasive effects and discrepant biological locations. Meanwhile, the spontaneous ROS profilings in various living organs/tissues are also limited by the penetration capability of probes across different biological barriers and the stability in reactive in vivo environments. Here, we report a single fluorescent probe to achieve the effective discrimination and profiling of hydroxyl radicals (•OH) and hypochlorous acid (HClO) in living organisms. The probe is constructed by chemically grafting an additional five-membered heterocyclic ring and a lateral triethylene glycol chain to a fluorescein mother, which does not only turn off the fluorescence of fluorescein, but also create the dual reactive sites to ROS and the penetration capability in passing through various biological barriers. The reactions of probe with •OH and HClO simultaneously result in cyan and green emissions, respectively, providing the real-time discrimination and quantitative analysis of the two ROS in cellular mitochondria. Surprisingly, the accumulation of probes in the intestine and liver of a normal-state zebrafish and the transfer pathway from intestine-to-blood-to-organ/tissue-to-kidney-to-excretion clearly present the profiling of spontaneous •OH and HClO in these metabolic organs. In particular, the stress generation of •OH at the fresh wound of zebrafish is successfully visualized for the first time, in spite of its extremely short lifetime.

Dual-Colored Carbon Dot Ratiometric Fluorescent Test Paper Based on a Specific Spectral Energy Transfer for Semiquantitative Assay of Copper Ions

Classical pH test papers are widely used to measure the acid-base degree of media in a qualitative or semiquantitative manner. However, the extension of portable and inexpensive methods to a wide range of analytes so as to eliminate the tediousness of instrumental assays remains unsuccessful. Here, we report a novel kind of dual-colored carbon dot (CD) ratiometric fluorescent test paper for the semiquantitative assay of copper ions (Cu2+) by a dose-sensitive color evolution. The preparation of the test paper is based on the following two interesting findings: on the one hand, residual p-phenylenediamine at the surface of as-synthesized red CDs (r-CDs) efficiently binds Cu2+ ions to produce a strong visible absorption that overlaps the emission of blue CDs (b-CDs); on the other hand, the Cu2+ ions render the adsorption of small b-CDs onto the surface of larger r-CDs through their dual-coordinating interactions with the surface ligands of both r-CDs and b-CDs. These two mechanisms lead to a specific spectral energy transfer to quench the fluorescence of b-CDs with a sensitive detection limit of 8.82 nM Cu2+, whereas the red fluorescence of r-CDs is unaffected as a stable internal standard. Ratiometric fluorescent test papers have been prepared using a mixture of r-CDs and b-CDs (1:7) as ink by jetprinting on a piece of paper. With the addition of Cu2+ ions, the blue test paper produces a consecutive wide-colored evolution from blue to orange-red, with a dose-discerning ability as low as 25 nM.

Asymmetric geometry composites arranged between parallel aligned and interconnected graphene structures for highly efficient thermal rectification

A novel framework of binary asymmetric geometry composites was arranged between parallelly aligned and interconnected, microcosmic, graphene structures. The greater number of efficient, heat transfer channels in interconnected graphene networks (one end) than in the parallelly aligned structures (another end) resulted in both ends of the thermal conductivity saltation. Therefore, this resulted in the adjustment of the thermal rectification of graphene composites to control the direction of heat flow.

Upconversion color tuning in Ce3+-doped LiYF4:Yb3+/Ho3+@LiYF4 nanoparticles towards ratiometric fluorescence detection of chromium(III)

Ratiometric fluorescence sensor exhibits advantages of sensitive response, high anti-interference ability and naked eye visualization owing to multiple independent emission peaks utilized for results analysis. To achieve such multi-emission probe, the traditional methods have involved simple mixing of two emitters or tedious synthesis processes of hybrid material. However, these probes often have problems of inconstant emission strength ratio, low light-stability, and complicated synthetic process, which limit their applications in practical field. Herein, we report a single-structure Ce3+-doped LiYF4:Yb3+/Ho3+@LiYF4 upconversion nanoparticles (UCNPs), which features two emission peaks in the green (at 540nm) and red (at 640nm) region under the excitation of 980nm near infrared laser. Importantly, the red/green intensity ratio can be regulated by changing the doping level of Ce3+ to modulate output colors. Furthermore, a Cr3+-responsive rhodamine derivative (CRD) was modified on the devised UCNPs surface to fabricate the colorimetric probe by luminescent resonance energy transfer (LRET) process. Upon addition of Cr3+ into the probe solution, the absorption peak of CRD at 560nm is significantly enhanced, which greatly reduced the green emission, leading to an obvious color evolution from green to yellow to orange and to red with increasing the concentration of Cr3+. This method is successfully applied to practical detection of Cr3+ ion in industrial waste water. The work reported here demonstrates a useful way to construct color-based visual assays.

Multicolorful ratiometric-fluorescent test paper for determination of fluoride ions in environmental water

Here, a ratiometric fluorescent test paper for the visual and on-site determination of environmental fluoride ions was fabricated by inkjet-printing of the as-prepared “ink” onto a filter paper. The “ink” was prepared by mixing the fluoride-sensitive organic probe (C-TIPS) with red CdTe quantum dots (QDs) in an optimal proportion. The designed fluorescent fluoride probe shows a turn-on effect in the presence of fluoride ions. With the aid of thee red fluorescence of CdTe QDs, the test paper exhibited a distinguishable fluorescence color change from red to purple to blue under a UV lamp. The as-prepared ratiometric-fluorescent test paper displayed a superior sensitivity and visual effectiveness to quantify fluoride ions, with a detection limit of 0.285 μM which is lower than the World Health Organization (WHO) defined limit (79 μM). Moreover, the test paper is highly applicable for the detection of fluoride ions in natural waters in a very simple, cost efficient and on-site way.

A ratiometric fluorescent paper sensor for consecutive color change-based visual determination of blood glucose in serum

Fluorescent paper sensors are widely used in the assays of environment, food and medicine; however, their applications usually have been limited due to the narrow color-change range and insensitivity of the color variation to dosage of target analytes. In this paper, we report a ratiometric fluorescent probe-based paper sensor regulated by the optimum proportion of gold nanoclusters stabilized by bovine serum albumin and fluorescent graphene oxide to achieve the maximum consecutive color change for visual determination of glucose in human serum. The oxidation of hydrogen peroxide produced by glucose quenches the red fluorescence emission of gold nanoclusters and unveils a consecutive color change from pink to blue with the corresponding dosage of glucose. This colorimetric paper sensor printed with the probe ink exhibits a dosage-sensitive allochromatic capability for the blood glucose concentration of 4–10 mM in human serum (normal concentration: 4.4–6.6 mM). The method reported here can open a window in predicting diseases related to abnormal glucose levels.

Carbonized Waste Cotton/Stearic Acid Composites for Photo-Thermal Conversion and Heat Storage

Photo-thermal conversion is an effective method to utilise solar energy. The generated heat can be converted into electrical energy through the thermoelectric Seebeck effect. However, the key challenge in enhancing solar-thermal-electric conversion is to achieve efficient photo-thermal conversion and temperature difference control. Herein, new composite materials are prepared using abundant and cheap raw materials to simultaneously realise photo-thermal conversion, heat storage, and heat supply for a thermoelectric device. The composites consist of carbonised waste cotton and stearic acid (SA), where carbonised waste cotton can achieve efficient full spectrum photo-thermal conversion and SA can store the generated heat to maintain a stable temperature for a thermoelectric device. The best content of SA is found to be 85 wt-% in the composites due to uniform dispersion and ideal combination. The 3D netlike structure of carbonised waste cotton provides increased heat transfer paths and also prevents leakage of SA during phase change. The maximum phase change enthalpy is 203.6 J g−1 for the composite with 85 wt-% SA, which is almost the same as pure SA, assuring high density heat storage. A light-thermal-electric conversion device is further constructed based on as-prepared composites and a thermoelectric system. The generated electricity can light up a light-emitting diode with strong intensity.

Dynamic mapping of spontaneously produced H2S in the entire cell space and in live animals using a rationally designed molecular switch

Hydrogen sulfide (H2S) is a key signaling molecule in the cytoprotection, vascular mediation and neurotransmission of living organisms. In-depth understanding of its production, trafficking, and transformation in cells is very important in the way H2S mediates cellular signal transductions and organism functions; it also motivates the development of H2S probes and imaging technologies. A fundamental challenge, however, is how to engineer probes with sensitivity and cellular penetrability that allow detection of spontaneous production of H2S in the entire cell space and live animals. Here, we report a rationally designed molecular switch capable of accessing all intracellular compartments, including the nucleus, lysosomes and mitochondria, for H2S detection. Our probe comprised three functional domains (H2S sensing, fluorescence, and biomembrane penetration), could enter almost all cell types readily, and exhibit a rapid and ultrasensitive response to H2S (≤120-fold fluorescence enhancement) for the dynamic mapping of spontaneously produced H2S as well as its distribution in the whole cell. In particular, the probe traversed blood/tissue/cell barriers to achieve mapping of endogenous H2S in metabolic organs of a live Danio rerio (zebrafish). These results open-up exciting opportunities to investigate H2S physiology and H2S-related diseases.

Ratiometric Fluorescent Biosensor for Visual Discrimination of Cancer Cells with Different Telomerase Expression Levels

Telomerase is inactive in normal somatic cells but highly activated in tumor cells to maintain their indefinite proliferation and immortal phenotype. As a specific marker for the generation and progress of almost all tumors, the detection of telomerase activity by classical PCR techniques has served in the biological research of tumors. However, the detection of in situ telomerase activity in cell extracts to evaluate the malignancy, progress, and metastasis of tumors remains a daunting challenge. Here, a precisely designed FRET-based ratiometric fluorescent oligonucleotide probe has achieved high-fidelity detection of telomerase activity for accurate discrimination of different cancer cells toward advanced diagnosis of tumors. Our method is superior to other methods in its capabilities to quantify telomerase activity in cell extracts and visualize various tumor cell extracts with different telomerase expression levels by the naked eye for clinical diagnosis. In particular, the ratiometric fluorescent probe used in the assay could exclude other experimental factors influence, and further avoid false positive signal generation. The method reported here could provide a reliable, accurate, and convenient way in medical diagnostics and therapeutic response assessment.