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Coordination geometry-induced optical imaging of <scp>l</scp> -cysteine in cancer cells using imidazopyridine-based copper( <scp>ii</scp> ) complexes
摘要： Overexpression of cysteine cathepsins proteases has been documented in a wide variety of cancers, and enhances the L-cysteine concentration in tumor cells. We report the synthesis and characterization of copper(II) complexes [Cu(L1)2(H2O)](SO3CF3)2, 1, L1 = 3-phenyl-1-(pyridin-2-yl)imidazo[1,5-a]pyridine, [Cu(L2)2(SO3CF3)]SO3CF3, 2, L2 = 3-(4-methoxyphenyl)-1-pyridin-2-yl-imidazo[1,5-a]pyridine, [Cu(L3)2(H2O)](SO3CF3)2, 3, L3 = 3-(3,4-dimethoxy-phenyl)-1-pyridin-2-yl-imidazo[1,5-a]pyridine and [Cu(L4)2(H2O)](SO3CF3)2, 4, L4 = dimethyl-[4-(1-pyridin-2-yl-imidazo[1,5-a]pyridin-3-yl)phenyl]amine as 'turn-on' optical imaging probes for L-cysteine in cancer cells. The molecular structure of complexes adopted distorted trigonal pyramidal geometry (τ, 0.68–0.87). Cu–Npy bonds (1.964–1.989 ?) were shorter than Cu–Nimi bonds (2.024–2.074 ?) for all complexes. Geometrical distortion was strongly revealed in EPR spectra, showing gk (2.26–2.28) and Ak values (139–163 × 10?4 cm?1) at 70 K. The d–d transitions appeared around 680–741 and 882–932 nm in HEPES, which supported the existence of five-coordinate geometry in solution. The Cu(II)/Cu(I) redox potential of 1 (0.221 V vs. NHE) was almost identical to that of 2 and 3 but lower than that of 4 (0.525 V vs. NHE) in HEPES buffer. The complexes were almost non-emissive in nature, but became emissive by the interaction of L-cysteine in 100% HEPES at pH 7.34 via reduction of Cu(II) to Cu(I). Among the probes, probe 2 showed selective and efficient turn-on fluorescence behavior towards L-cysteine over natural amino acids with a limit of detection of 9.9 × 10?8 M and binding constant of 2.3 × 105 M?1. The selectivity of 2 may have originated from a nearly perfect trigonal plane adopted around a copper(II) center (～120.70°), which required minimum structural change during the reduction of Cu(II) to Cu(I) while imaging Cys. The other complexes, with their distorted trigonal planes, required more reorganizational energy, which resulted in poor selectivity. Probe 2 was employed for optical imaging of L-cysteine in HeLa cells and macrophages. It exhibited brighter fluorescent images by visualizing Cys at pH 7.34 and 37 °C. It showed relatively less toxicity for these cell lines as ascertained by the MTT assay.
关键词： optical imaging,cancer cells,turn-on fluorescence,imidazopyridine,L-cysteine,Copper(II) complexes
更新于2025-11-21 11:08:12
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Highly Luminescent Nitrogen-Doped Carbon Dots as “Turn-On” Fluorescence Probe for Selective Detection of Melamine
摘要： In our work, a new and simple method for selective detection of melamine is established by developing a "turn-on" fluorescence probe based on nitrogen-doped carbon dots (N-CQDs). The N-CQDs have been facilely prepared by one-step simple hydrothermal reaction and it is highly luminescent that with 51% fluorescent quantum yield. In this sensor, the fluorescent intensity of N-CQDs was found to be efficient quenched by Fe3+, upon addition of melamine the fluorescent intensity of N-CQDs-Fe3+ could gradually recover, which may because of the competitive combination of Fe3+ and melamine leading to the departure of Fe3+ from the N-CQDs' surface. Under optimum conditions, the fluorescence intensity has a good liner relationship with melamine in the range of 2.0 to 290 μM. The probe displayed good sensitivity toward melamine with a lower detection limit of 0.67 μM. In addition, this fluorescence probe has been used for the analysis of milk samples, demonstrating the fluorescence probe has potential application in the detection of melamine.
关键词： selective detection,turn-on fluorescence probe,melamine,carbon quantum dot
更新于2025-09-23 15:23:52
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Cancer Selective Turn-on Fluorescence Imaging Using a Biopolymeric Nanocarrier
摘要： Most nanoparticle-based bioresearch for clinical applications is unable to overcome the clinical barriers of efficacy (e.g., sensitivity and selectivity), safety for human use, and mass-production processes. Here, we proposed a promising concept of using a biocompatible nanocarrier that delivers natural fluorescent precursors into cancerous cells. The nanocarrier is a biopolymeric nanoparticle that can be easily loaded with fluorescent precursors to form a fluorescent moiety via a biosynthesis pathway. Once delivered into cancerous cells, the nanocarriers are selectively turned on and distinctively fluoresce upon excitation. We, therefore, demonstrated the efficacy of the selective turn-on fluorescence of the nanocarriers in in vitro co-culture models and in vivo tumor-bearing models.
关键词： Hyaluronic Acid,Cancer Diagnosis,Biocompatible Nanocarrier,Turn-on Fluorescence,5-Aminolevulinic Acid
更新于2025-09-23 15:22:29
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Discovery and Characterization of a Naturally Occurring, Turn-On Yellow Fluorescent Protein Sensor for Chloride
摘要： Fluorescent proteins have been extensively engineered and applied as optical indicators for chloride in a variety of biological contexts. Surprisingly, given the biodiversity of ?uorescent proteins, a naturally occurring chloride sensor has not been reported to date. Here, we present the identi?cation and spectroscopic characterization of the yellow ?uorescent protein from the jelly?sh Phialidium sp. (phiYFP), a rare example of a naturally occurring, excitation ratiometric, and turn-on ?uorescent protein sensor for chloride. Our results show that chloride binding tunes the pKa of the chromophore Y66 and shifts the equilibrium from the ?uorescent phenolate form to the weakly ?uorescent phenol form. The latter likely undergoes excited-state proton transfer to generate a turn-on ?uorescence response that is pH-dependent. Moreover, anion selectivity and mutagenesis in the chloride binding pocket provide additional evidence for the proposed chloride sensing mechanism. Given these properties, we anticipate that phiYFP, with further engineering, could be a new tool for imaging cellular chloride dynamics.
关键词： phiYFP,mutagenesis,chloride sensor,anion selectivity,turn-on fluorescence,pH-dependent,excitation ratiometric,fluorescent proteins
更新于2025-09-23 15:21:21
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A system composed of vanadium(IV) disulfide quantum dots and molybdenum(IV) disulfide nanosheets for use in an aptamer-based fluorometric tetracycline assay
摘要： A system composed of vanadium(IV) disulfide quantum dots (VS2 QDs) and molybdenum(IV) disulfide (MoS2) nanosheets for use in an aptamer-based fluorometric tetracycline assay was developed. The tetracycline (TET) aptamer was first immobilzed on the VS2 QDs with a typical size of 3 nm. The blue fluorescence of the VS2 QDs (labeled with aptamer) with emission maxima at 448 nm (under excitation at 360 nm) was subsequently quenched by MoS2 nanosheets. If TET is recognized by the aptamer, the VS2 QDs drift away from the basal plane of the MoS2 nanosheets. This generated “turn-on” fluorescence of the VS2 QDs. AVS2 QD/MoS2 nanosheet-based fluorometric TET aptasensor was thus constructed. Selective and sensitive TET bioanalysis was realized in a linear range of 1 to 250 ng mL?1. The detection limit was 0.06 ng mL?1. Its applicability of determination of TET in milk samples has been demonstrated.
关键词： MoS2,Aptamer,VS2 quantum dots,Fluorometric assay,Antibiotic,Turn-on fluorescence
更新于2025-09-11 14:15:04