Based on the findings that the azo functional group has excellent properties as the hypoxia-sensor moiety, we developed hypoxia-sensitive near-infrared fluorescent probes in which a large ...fluorescence increase is triggered by the cleavage of an azo bond. The probes were used for fluorescence imaging of hypoxic cells and real-time monitoring of ischemia in the liver and kidney of live mice.
To investigate the initial immune response to biodegradable silk fibroin (SF) hydrogels in vivo, a Förster/fluorescence resonance energy transfer (FRET)-based sensor was developed to detect matrix ...metalloproteinase (MMP) activity (FRET-MMPS) and immobilized to SF hydrogel. FRET-MMPS immobilized to SF hydrogel in vitro displayed intra-molecular FRET more than inter-molecular FRET, and MMP activity was detected through a decrease in FRET signal intensity. Then, the SF hydrogel modified with FRET-MMPS was implanted into mice subcutaneously, and it was observed that the FRET signal intensity decreased significantly soon (< 3 h) after implantation. Although the intensity exhibited a sharp decrease toward 24 h post-implantation, histological evaluation proved that bulk-level hydrogel degradation, such as breakdown, was mainly caused by macrophages and foreign body giant cells on a timescale of weeks. These results indicated that, immediately upon implantation, active MMPs reached the SF hydrogel and began cleaving SF networks, which might result in the loosening of the networks and then enabled immune cells, such as macrophages, to start the bulk-level hydrogel degradation. The sensor clarified the initial immune response to SF hydrogels and will provide clues for designing the biodegradation behaviors of scaffolds for regenerative medicine.
Silk fibroin (SF) materials are degraded gradually by the immune response. Immune cells, such as macrophages, break down implanted SF materials on a timescale of weeks or months, but the initial (< 24 h) immune response to SF materials remains unclear. In this study, SF hydrogels modified with Förster/fluorescence resonance energy transfer (FRET)-based matrix metalloproteinase (MMP) sensors were implanted in mice and within 3 h post-implantation, the SF hydrogels were degraded by MMPs. Although this molecular-level biodegradation was not correlated with the hydrogel breakdown, the MMPs were likely to loosen the SF networks to enable immune cells to infiltrate and degrade the hydrogel. This is the first study to unveil the initial stage of immune response to biomaterials.
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To date, few effective fluorescent biosensors based on RNA aptamers have been developed because the intrinsic instability of RNA in the presence of nucleases precludes the application of RNA aptamers ...for the analysis of biological fluids. In this study, we developed a simple, sensitive, selective turn-on fluorescent aptasensor for theophylline detection in serum, utilizing ligand-induced self-assembling RNA aptamers and two different interaction stages of the aptamer fragments with graphene oxide (GO). A single strand of the theophylline RNA aptamer (33-mer) was split at the end loop region into two shorter fragments, one of which was labeled with a fluorophore (FAM). In the absence of theophylline, the adsorption of the two individual fragments on GO brought the fluorophore in close proximity to the GO surface, resulting in highly efficient quenching of fluorescence. The system showed very low background fluorescence. Conversely, the fragments self-assembled into an RNA aptamer/theophylline complex and were dissociated from GO. The quenched fluorescence was significantly recovered, and theophylline could be detected at a wide range of concentrations from 1 to 100μM, with a detection limit of 0.155μM and good selectivity in serum. Moreover, because of the shorter RNA fragments and the effective protection ability of GO from nuclease cleavage, the RNA sequences remained stable during the experiments. This design may serve as an example for the application of RNA aptasensors in the clinical setting.
•This design yielded an RNA aptasensor through two stages of RNA fragments with GO.•This system offers a convenient protocol for theophylline detection in serum.•In this system, GO acted as a quencher and protected the absorbed RNA fragments.
Lysosomes are membrane-bound organelles responsible for the transport and degradation of intracellular and extracellular cargo. The intracellular motion of lysosomes is both diffusive and active, ...mediated by motor proteins moving lysosomes along microtubules. We sought to determine how lysosome diameter influences lysosome transport. We used osmotic swelling to double the diameter of lysosomes, creating a population of enlarged lysosomes. This allowed us to directly examine the intracellular transport of the same organelle as a function of diameter. Lysosome transport was measured using live cell fluorescence microscopy and single particle tracking. We find, as expected, the diffusive component of intracellular transport is decreased proportional to the increased lysosome diameter. Active transport of the enlarged lysosomes is not affected by the increased lysosome diameter.
Glutathione (GSH) plays key roles in biological systems and serves many cellular functions. Since biothiols all incorporate thiol, carboxylic and amino groups, discriminative detection of GSH over ...cysteine (Cys) and homocysteine (Hcy) is still challenging. We herein report a dual-mode nanosensor with both colorimetric and fluorometric readout based on carbon quantum dots and gold nanoparticles for discriminative detection of GSH over Cys/Hcy. The proposed sensing system consists of AuNPs and fluorescent carbon quantum dots (CQDs), where CQDs function as fluorometric reporter, and AuNPs serve a dual function as colorimetric reporter and fluorescence quencher. The mechanism of the nanosensor is based on two distance-dependent phenomenons, color change of AuNPs and FRET. Through controlling the surface properties of as-prepared nanoparticles, the addition of CQDs into AuNPs colloid solution might induce the aggregation of AuNPs and CQDs, leading to AuNPs color changing from red to blue and CQDs fluorescence quench. However, the presence of GSH can protect AuNPs from being aggregated and enlarge the inter-particle distance, which subsequently produces color change and fluorescent signal recovery. The nanosensor described in this report reflects on its simplicity and flexibility, where no further surface functionalization is required for the as-prepared nanoparticles, leading to less laborious and more cost-effective synthesis. The proposed dual-mode nanosensor demonstrated highly selectivity toward GSH, and allows the detection of GSH as low as 50nM. More importantly, the nanosensor could not only function in aqueous solution for GSH detection with high sensitivity but also exhibit sensitive responses toward GSH in complicated biological environments, demonstrating its potential in bioanalysis and biodection, which might be significant in disease diagnosis in the future.
●A dual-mode nanosensor for discriminative GSH detection with high sensitivity.●The nanosensor consists of AuNPs and fluorescent CQDs.●Color change of AuNPs and FRET form the basis of the nanosensor.●The label-free nanosensor is simple and flexible.●The nanosensor could function in complicated biological fluids.
G-quadruplex DNA for construction of biosensors Yang, Hualin; Zhou, Yu; Liu, Juewen
TrAC, Trends in analytical chemistry (Regular ed.),
November 2020, 2020-11-00, Volume:
132
Journal Article
Peer reviewed
DNA-based biosensors have been widely used for its stable chemical properties, cost-effectiveness, and easy modification. G-quadruplex (G4) DNA has attracted growing interest since it can be used for ...both target recognition and signal transduction. Much of G4 DNA's relevance in biosensors is related to its ability to bind specific metal ions, dyes and porphyrins, and these properties are first reviewed. Then, the role of G4 for molecular recognition is discussed including the sensing of metal ions, proteins and enzymes. Subsequently, G-quadruplex for signaling transduction is reviewed. In this part, G4 binds some substrate to enhance fluorescence, and binds hemin to show peroxidase-like activity. Finally, some sensors used G4 DNA for both target recognition and signaling. This review mainly contains specific examples of biosensors published in the last five years. Finally, some challenges in the field are discussed and a few future research opportunities are proposed.
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•Metal binding, porphyrin binding and dye binding properties of G-quadruplex DNA reviewed.•G-quadruplex for target recognition and signal transduction in biosensors reviewed.•Recent examples of G-quadruplex based biosensors in the last five years described.
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•Up-to-date advances of the biomarker-activable probes based on smart AIEgens are reviewed.•The probes’ structural features, photophysical properties and biological applications have ...been introduced.•Future research/development opportunities and challenges have been presented.
Fluorophores with aggregation-induced emission (AIE) are characterized by many advantageous features for biomedical applications, including excellent photostability and enhanced fluorescent emission in aqueous milieu with minimal aggregation caused quenching (ACQ) effect. The abnormal levels of biomarkers are closely correlated with various diseases. Hence developing new strategies for detection and imaging of disease biomarkers fluorescently and optoacoustically is of high significance for early diagnosis of diseases. Probes (contrast agents) play essential roles in fluorescent and optoacoustic imaging. They have been extensively explored and applied in recent years, which induce the emergence of a variety of new probes in particular the biomarker-activatable probes based on smart AIEgens for fluorescence and optoacoustic imaging. In this review, we aim to summarize the latest development and progress as well as biomedical applications of the biomarker-activatable probes based on smart AIEgens. We focus on their design strategies and highlight the prospects and challenges in fluorescent and optoacoustic imaging.
Organic light-emitting diodes (OLEDs) employing purely organic functional materials indicate a low-cost manufacturing route towards the next-generation display and solid-state lighting owing to the ...avoidance of noble heavy metal complex phosphorescent emitters. In recent years, several mechanisms have been proposed to design high performance purely organic emitters. This new generation of purely organic emitters shed light on the realization of both low-cost and high performances. The main idea of this paper is to review how to use purely organic semiconductors to realize high-efficiency OLEDs. This guides us to pay special attention to two aspects: 1) how to break the efficiency bottleneck resulting from exciton spin-statistics, which is critical to determine internal quantum efficiency; 2) how to enhance out-coupling efficiency by molecular designs, which eventually influences on external quantum efficiency. Several significant material design strategies are thus introduced, and the relevant mechanisms are classified as triplet-triplet annihilation, thermally activated delayed fluorescence, hot excitons, room temperature phosphorescence, and luminescent radicals. Then, device strategies by employing organic heterojunctions as the main luminescent center towards high-performance fluorescent OLEDs were introduced. Finally, we outline the progress of enhancing out-coupling efficiency by tuning the dipole orientation of emitters and the operational stability of OLEDs excluding noble heavy metal complex phosphorescent emitters.
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•Concurrent green synthesis of N-CDs and ZnO@N-C hybrid by a hydrothermal method.•N-CDs used as a multicolour fluorescent probe for cell imaging without passivation.•ZnO@N-C utilized ...for the degradation of MB with a high rate constant of 0.0456min−1.•This green synthesized material could offer eco-friendly environmental applications.•Moreover, new avenue to synthesize metal oxide grafted carbon sheets was provided.
The hybrid composite of ZnO nanoparticles decorated nitrogen-doped graphitic carbon sheets (ZnO@N-C) alongside nitrogen-doped carbon dots (N-CDs) were synthesized by the direct hydrothermal method of peach fruit juice and ZnO nanoparticles (ZnO NPs). The synthesized ZnO@N-C hybrid composite and N-CDs were thoroughly characterized by various physicochemical techniques including powder X-ray diffraction (PXRD), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and fluorescence spectroscopy. The ZnO NPs were dispersed in the graphitic carbon structure with an average size of 25±5nm. The chemical composition of C, O, N, and Zn within the ZnO@N-C hybrid composite exhibits enough graphitization. Methylene blue (MB)-degradation was estimated utilizing the ZnO@N-C hybrid composite, a maximum degradation efficiency of >95% was achieved in a neutral aqueous medium within 60min under UV-light irradiation. This maximum efficiency allows estimating the contribution of the heterogeneous and homogeneity of ZnO@N-C hybrid composite which is responsible for the MB-degradation. Moreover, the economic natural biosource or bio-waste was employed for the synthesis of ZnO@N-C hybrid composite and displays an excellent photocatalytic degradation under UV-light irradiation which is an alternate for other carbon-based metal oxides. In addition, the resulting N-CDs were utilized as a fluorescence probe for cellular imaging, owing to their tremendous properties such as bright fluorescence with high quantum yield, excellent water solubility, and good biocompatibility. The N-CDs displays a multicolour fluorescence based on their changing of excitation wavelength and these multicolour fluorescence emissions offered a multicolour cellular imaging which could be applicable for real biological system in the near future.
•A magnetic aptamer-complementary DNA complex was formed.•FAM-labeled aptamer was used as the probe.•The functionalized magnetic nanoparticles were applied as the separation carrier.•A method for ...detection of three organophosphorus pesticides in samples was presented.
There has been increasing recent concern about the agricultural use of organophosphorus pesticides. A rapid and sensitive fluorescence assay for the detection of three organophosphorus pesticides has therefore been developed using 6-carboxy-fluorescein labeling aptamer as the probe and functionalized magnetic nanoparticles as the separation carrier. The aptamer hybridized with complementary DNA conjugated on the surface of the magnetic nanoparticles to form a magnetic aptamer-complementary DNA complex. Upon introducing the target organophosphorus pesticide, the aptamer departed from the complementary DNA, resulting in the fluorescence signal. Under optimized conditions, the limits of detection (LODs, S/N = 3) for trichlorfon, glyphosate, and malathion were 72.20 ng L−1, 88.80 ng L−1, and 195.37 ng L−1, respectively. The method was applied for the detection of trichlorfon, glyphosate, and malathion in spiked lettuce and carrot samples. The recoveries were in the range of 79.4%–118.7%, which were in good agreement with those obtained by gas chromatography, and the relative standard deviations were also acceptable. The method therefore has high sensitivity, so provides a means for the detection of multiple organophosphorus pesticides.
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