Sensitive Fluorescence Response Research Articles

Real-time blood gas analysis using pH, PO2 and PCO2 multifunctional fluorescent capillary sensing system

Real-time blood gas analysis is of great significance in disease diagnosis and treatment. Here we have developed a pH, PO2 and PCO2 multifunctional fluorescent capillary sensing system. The pH, O2 and CO2 fluorescent indicators with same excitation wavelength are fixed into a single capillary tube. The sensing system possesses sensitive fluorescence response to pH, O2 and CO2, and the changes of pH, O2 and CO2 in buffer, in vitro, and in vivo can be detected simultaneously by measuring the fluorescence signals of sensor probe. The PO2, PCO2 and pH of rabbits in four disease models were assessed efficiently by the sensing system, exhibiting similar variation trend with the results by blood gas analyzer. Studies in living rabbit display the reasonable and favorable feasibility of capillary sensing system in real-time arterial blood gas analysis. Overall, the multifunctional fluorescent capillary sensing system exhibits significant potential in real-time arterial blood gas analysis and clinical application of disease diagnosis.

Highly selective and sensitive fluorescent probes for nitrofurazone and Hg2+ by two Zn (II)‐based coordination polymers

The self‐assembly of the π‐conjugated 1,4‐di(1H‐imidazol‐1‐yl)benzene (dib) and 4,4′‐di(1H‐imidazol‐1‐yl)‐1,1′‐biphenyl (dibp) ligands together with 4′‐(3,4‐ dicarboxylphenyloxy)‐4‐biphenylcarboxylic acid (H3L) reacts with metal Zn (II) salts to construct two new coordination polymers (CPs), namely [Zn (dib)(HL)(H2O)] (1) and [Zn (dibp)(HL)] (2). Fluorescence measurements reveal that 1 and 2 could display a highly sensitive fluorescence response toward Hg2+ and nitrofurazone (NFZ). Fluorescence investigations suggest that 1 and 2 are promising multi‐responsive sensing materials for detecting Hg2+ and NFZ through fluorescence quenching (turn‐off). The limits of detection toward Hg2+ ions are 0.221 μM and 0.124 μM, while the limits of detection toward NFZ are 0.757 μM and 0.960 for 1 and 2, respectively. Interestingly, these Hg2+ and NFZ selective sensing processes can even be completed by the reusable CPs detected by the naked eyes. Hirshfeld surfaces and fingerprint plots are extensively used to investigate intermolecular interactions, which play a crucial role in creating diverse supramolecular designs that can be compared.

Novel Schiff base embedded in nanostructured molecularly imprinted polymers as OFF–ON fluorescent sensor for highly selective detection of rutin residues in fruit juice

This study aimed to create a fluorescent novel Schiff base polymer (SBP) sensor for the detection of rutin (RT) flavonoid based on nanostructured molecularly imprinted polymer (SBM), precisely designed template molecules, and site-specific post-imprinting modifications. The fabricated SBM sensor was characterized in detail, and the prepared SBM exhibited stable and sensitive reproducible fluorescence response and highly selective recognition capability for detecting trace amounts of RT. Besides, the influential factors, such as pH and incubation time were performed in the optimal extraction conditions. The calibration curve yields a linear range for the detection of RT under optimal conditions. The linear fluorescence response of SBM to RT was obtained in the concentration range of 1–200 μg L− 1 (R2 = 0.9988) with a limit of detection (LOD) of 0.024 μg L−1. The SBM presented satisfying recoveries with a relative standard deviation of less than 3.0 % (n = 7) in spiked samples. The sensor shows broad prospects in the quality evaluation and grading of functional foods, as it can rapidly identify and quantify RT in red raspberry and green tea samples.

A simple yet effective H2S‐activated fluorogenic probe for precise imaging of hepatitis and arthritis in situ

AbstractHepatitis and arthritis are prevalent inflammatory diseases, and the utilization of fluorogenic probes incorporating hydrogen sulfide (H2S) as a crucial mediator of inflammation presents significant opportunities for early detection. However, the poor in vivo biodistribution and limited targeted efficacy of molecule probes for inflammation imaging severely impede their ability to differentiate the extent of inflammation and provide real‐time monitoring of inflammatory levels. Therefore, we developed a highly efficient H2S‐activated near‐infrared (NIR) fluorogenic probe (hCy‐DNP) for real‐time tracking and capturing fluctuations in H2S levels within inflammatory lesions. hCy‐DNP demonstrates an exceptionally sensitive fluorescence response to H2S expression, enabling specific differentiation between various levels of lipopolysaccharide (LPS) ‐stimulated early hepatitis models in situ, while also facilitating visual monitoring for diagnosis and efficacy evaluation of arthritis. Therefore, hCy‐DNP offers an innovative tool for exploring early diagnosis and evaluating treatment effectiveness across diverse inflammatory diseases.

Luminescent carbon dots-rooted polysaccharide crosslinked hydrogel adsorbent for sensitive determination and efficient removal of Cu2+

In this study, a novel luminescent carbon dot-rooted polysaccharide hydrogel (CDs@CCP hydrogel) was prepared by crosslinking cellulose, chitosan (CS), and polyvinyl alcohol (PVA) for simultaneous fluorescent sensing and adsorption of Cu2+. The crosslinking of these low-cost, polysaccharide polymers greatly enhance the mechanical strength of the composite hydrogel while making the polysaccharide-based adsorbent easy to reuse. This composite hydrogel exhibited an excellent adsorption capacity (124.7 mg∙g−1) for residual Cu2+ in water, as well as a sensitive and selective fluorescence response towards Cu2+ with a good linear relationship (R2 > 0.97) and a low detection limit (LOD) of 0.02 μM. The adsorption isotherms, adsorption kinetics, and thermodynamics studies were also conducted to investigate the adsorption mechanism. This composite hydrogel offers an efficient tool for simultaneous monitoring and treatment of Cu2+ from wastewater.

Modulation of Heterotypic and Homotypic Interactions to Visualize the Evolution of Organic Aggregates in a Fluorescence Turn-on Manner.

The abnormal evolution of membrane-less organelles into amyloid fibrils is a causative factor in many neurodegenerative diseases. Fundamental research on evolving organic aggregates is thus instructive for understanding the root causes of these diseases. In-situ monitoring of evolving molecular aggregates with built-in fluorescence properties is a reliable approach to reflect their subtle structural variation. To increase the sensitivity of real-time monitoring, we presented organic aggregates assembled by TPAN-2MeO, which is a triphenyl acrylonitrile derivative. TPAN-2MeO showed a morphological evolution with distinct turn-on emission. Upon rapid nanoaggregation, it formed non-emissive spherical aggregates in the kinetically metastable state. Experimental and simulation results revealed that the weak homotypic interactions between the TPAN-2MeO molecules liberated their molecular motion for efficient non-radiative decay, and the strong heterotypic interactions between TPAN-2MeO and water stabilized the molecular geometry favorable for the non-fluorescent state. After ultrasonication, the decreased heterotypic interactions and increased homotypic interactions acted synergistically to allow access to the emissive thermodynamic equilibrium state with a decent photoluminescence quantum yield (PLQY). The spherical aggregates were eventually transformed into micrometer-sized blocklike particles. Under mechanical stirring, the co-assembly of TPAN-2MeO and Pluronic F-127 formed uniform fluorescent platelets, inducing a significant enhancement in PLQY. These results decipher the stimuli-triggered structural variation of organic aggregates with concurrent sensitive fluorescence response and pave the way for a deep understanding of the evolutionary events of biogenic aggregates.

2-Aminopurine-based quencher-free DNA tweezers with fluorescence properties well tuned by surrounding bases.

Reversible structural changes in DNA nanomachines have great potential in the field of bioanalysis. Here, we demonstrate an assembly strategy for quencher-free and tunable DNA tweezers based on 2-aminopurine (2-AP), avoiding the tedious fluorescence labelling step. The conformational state of the tweezers could be controlled by specific oligonucleotides (fuel or anti-fuel). Taking advantage of the local environmental sensitivity of 2-AP, the structural changes of the tweezers were easily tracked, and multiple cyclic switching of the tweezers between the open and closed states was achieved. In addition, the influence of oligonucleotide structure on the fluorescence properties of 2-AP was deeply explored. We figured out that the fluorescence of 2-AP was highly quenched by the base-stacking of natural bases in DNA oligonucleotides. Moreover, by comprehensively regulating the type of bases surrounding the inserted 2-AP site, a sensitive fluorescence response towards dynamic change can be obtained. This principle of quencher-free nanodevices based on 2-AP provides a convenient method for monitoring the structural changes of DNA nanomachines.

A ratiometric fluorescent probe revealing the abnormality of acetylated tau by visualizing polarity in Alzheimer's disease.

Abnormal neuronal polarity leads to early deficits in Alzheimer's disease (AD) by affecting the function of axons. Precise and rapid evaluation of polarity changes is very important for the early prevention and diagnosis of AD. However, due to the limitations of existing detection methods, the mechanism related to how neuronal polarity changes in AD is unclear. Herein, we reported a ratiometric fluorescent probe characterized by neutral molecule to disclose the polarity changes in nerve cells and the brain of APP/PS1 mice. Cy7-K showed a sensitive and selective ratiometric fluorescence response to polarity. Remarkably, unlike conventional intramolecular charge transfer fluorescent probes, the fluorescence quantum yield of Cy7-K in highly polar solvents is higher than that in low polar solvents due to the transition of neutral quinones to aromatic zwitterions. Using the ratiometric fluorescence imaging, we found that beta-amyloid protein (Aβ) inhibits the expression of histone deacetylase 6, thereby increasing the amount of acetylated Tau protein (AC-Tau) and ultimately enhancing cell polarity. There was a high correlation between polarity and AC-Tau. Furthermore, Cy7-K penetrated the blood-brain barrier to image the polarity of different brain regions and confirmed that APP/PS1 mice had higher polarity than Wild-type mice. The probe Cy7-K will be a promising tool for assessing the progression of AD development by monitoring polarity.

High-purity C3N quantum dots for enhancing fluorescence detection of metal ions.

A new type of two-dimensional layered material, namely C3N, has been fabricated by polymerization and recommended to have great potential in various applications such as the development of electronic devices or photo-detectors, due to its enhanced conductivity, electronegativity, and unique optical properties. Actually, most of the present research on C3N is limited in the scope of theoretical calculation, while experimental research is blocked by inefficient synthesis with low purity and homogeneity. Here, we report an optimized efficient synthesis method of high-purity C3N QDs in aqueous solution by polymerization of DAP with combined centrifugation and filtration of products, with the synthesis yield up to 33.1 ± 3.1%. Subsequently, the C3N QDs have been used as novel metal ion probes exhibiting a sensitive fluorescent response to various metal ions including monovalent alkaline metals (Li+, Na+, and K+), divalent alkaline-earth metals (Mg2+, Ca2+, and Sr2+), and multivalent transition metals (Cu2+, Co2+, Ni2+, and Au3+, Fe3+, Cr3+) due to the high electronegativity of the C3N surface. Particularly, the fluorescent quenching response of Al3+, Ga3+, In3+, and Sc3+ ions is significantly different from the fluorescent enhanced response of most other carbon-based QDs, which is promising for enriching the detection methods of these metal ions and beneficial to improve the accuracy of ion recognition.

Anthraquinone-based Schiff base fluorescent probe for the sequential sensing of Al3+ and pyrophosphate in a near-perfect aqueous solution and bioimaging

A new anthraquinone derivative fluorescent probe (DPHA) was designed and synthesized for sequentially detecting aluminum ions and pyrophosphate (PPi) in a near-perfect aqueous medium with 0.4 % DMSO as a co-solvent. The DPHA probe displayed “turn-on” fluorescence sensing of Al3+ at 575 nm, overcoming the interference of the other common cations through an apparent color variation from purple to light pink. Anthraquinone-derived conjugated skeleton and Schiff base-mediated multiple binding sites were responsible for the sensitive fluorescence response and selective recognition, respectively, thus producing a chelation-enhanced fluorescence effect. Furthermore, Job's plot analysis and high-resolution mass spectrometry (HRMS) studies supported the formation of a 1:1 ligand/metal complex for Al3+. The plausible binding mechanism was recognized by both experimentally and theoretically. The succeeding addition of PPi regenerated the original spectrum of DPHA and thus the strong affinity of Al3+ to PPi. The in-situ formed DPHA-Al3+ complex for selective identification of PPi by electrostatic interaction by drawing out Al3+ and releasing the DPHA probe. Except for specific recognition of Al3+ and PPi with corresponding low detection limits of 42.2 nM and 65.2 nM (S/N = 3). Owing to its good biocompatibility, DPHA also applied as a visual probe for monitoring Al3+ ions and PPi in living cells and zebrafish, demonstrating its outstanding potential in biological work.

Magnetically driven nanorobots based on peptides nanodots with tunable photoluminescence for rapid scavenging reactive α-dicarbonyl species and effective blocking of advanced glycation end products.

The present work constructed magnetically driven nanorobots by conjugating the photoluminescent β-alanine-histidine (β-AH) nanodots to superparamagnetic nanoparticles (SPNPs) for simultaneously sensitive determination and fast trapping RDS in food processing, achieving efficient regulation of advanced glycation end products (AGEs) risk. Bio-derivative β-AH nanodots with orderly self-assembly nanostructure and tunable photoluminescent properties served as both biorecognition elements to effectively bind and scavenge the reactive α-dicarbonyl species (RDS), as well as the indicator with sensitive fluorescence response in the food matrix. The magnetically driven nanorobots with excellent biosafety of endogenous dipeptides displayed a high binding capacity of 80.12mgg-1 with ultrafast equilibrium time. Furthermore, the magnetically driven nanorobots achieved rapid removal of the RDS with the manipulation of the external magnetic field, which enabled intercepting AGEs generation without byproducts residual as well as ease-of-operation. This work provided a promising strategy with biosafety and versatility for both accurate determination and efficient removal of hazards.

A large Stokes shift and emission shift ratiometric mitochondria-targeted fluorescent probe for sensing HClO with an ESIPT-ICT integrated platform

Hypochlorous acid (HClO) is regarded as a significant oxidative stress marker and plays key factor in various pathological and physiological processes. However, the overexpression of HClO is relation to variety of diseases due to cellular damage and oxidative stress. Studies have described that the HClO level in mitochondria is crucial to maintain the normal function of mitochondrial. Herein, we presented a simple mitochondria-targeted fluorescent probe (BA-MR), which consists of the benzothiazole dye as the fluorescent signaling unit, the methyl thioether as the HClO recognition group, and the imine pyridinium salt moiety as the mitochondria targeting group. The free probe BA-MR possessed a super large Stokes shift (260 nm) and displayed a red fluorescent at 600 nm. Upon addition of HClO, the methyl thioether of BA-MR was oxidezed exclusively into a sulfoxide group, thereby leading to the generation of compound BAO-MR with a prominent blueshift of emission at 450 nm. As expected,the probe displayed highly sensitive and selective fluorescence response to HClO with fast response (120 s) and a low detection limit (86 nM). Importantly, the newly-synthesized probe was displayed to have low cytotoxicity, and could be successfully used to imaging HClO in mitochondria, which demonstrated the probe BA-MR can act as an effective tool for researching HClO-related physiological and pathological processes.

A Smartphone-Based Sensing for Portable and Sensitive Visual Detection of Hg (II) via Nitrogen Doped Carbon Quantum Dots Modified Paper Strip.

The development of portable and cost-effective sensing system for Hg2+ quantitation is highly demanded for environmental monitoring. Herein, an on-site, rapid and portable smartphone readout device based Hg2+ sensing system integrating nitrogen-doped carbon quantum dots (NCDs) modified paper strip was proposed, and the physicochemical properties of NCDs were characterized by high resolution TEM, FTIR, UV-vis absorption spectrum and fluorescence spectral analysis. The modified paper strip was prepared via "ink-jet" printing technology and exhibits sensitive fluorescence response to Hg2+ with fluorescence color of bright blue (at the excitation/emission wavelength of 365/440nm). This portable smartphone-based sensing platform is highly selective and sensitive to Hg2+ with the limit of detection (LOD) of 10.6nM and the concentration range of 0-130nM. In addition, the recoveries of tap water and local lake water were in the range of 89.4% to 109%. The cost-effective sensing system based on smartphone shows a great potential for trace amounts of Hg2+ monitoring in environmental water samples.

The Synergistic Mechanisms of AIE, ESIPT and ICT in the α-cyanostilbene-based Derivative: A Red-fluorescence Probe With a Large Stokes' Shift for Copper (II) Ion Determination and Reversible Response to Amine/acid Vapor.

Herein, α-cyanostilbene-based luminogen with an electron donor-π-electron acceptor (D-π-A) architecture was formylated into the salicylaldehyde-analogue luminogen, followed by the Schiff base reaction with phenylamine, a red-emitting luminogen was elaborately designed and successfully synthesized in a high yield of 89%. Its well-defined structure was confirmed by FT-IR, MALDI-TOF-MS, HR-MS and 1H/13C NMR technologies. Based on the synergistic mechanisms of aggregation-induced emission (AIE), excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT), it enjoyed a red-fluorescence emission at 627 nm in THF/water mixtures (fw = 95%) and was used as a probe. Moreover, the TLC-based test strips loaded with the probe not only exhibited the reversible fluorescence response to amine/acid vapor but also showed sensitive and selective fluorescence response towards Cu2+. Furthermore, the fluorescence titration experiment between the probe and Cu2+ in THF/water mixtures (fw = 95%, pH = 7.4) revealed that the detection limit was 1.18 × 10-7 M and the binding constant was 1.59 × 105. Job's plot experiment and HR-MS analysis revealed the 2:1 binding stoichiometry of the probe with Cu2+. The method enabled real-time assessment for Cu2+ in real water samples. This study could offer insightful opinions on the development of long-wavelength emissive luminogens based on α-cyanostilbene.

In Situ Fluorescence Imaging Reveals Contribution of Cerebral Hydroxyl Radicals in Hyperhomocysteinemia-Induced Alzheimer-like Dementia.

Elevated plasma level of homocysteine, also termed as hyperhomocysteinemia, is acknowledged as a significant and independent risk factor of Alzheimer's disease. However, the mechanistic insight has not been thoroughly elucidated yet. In this work, 3,5-dihydroxybenzyloxy was explored as the unique reaction trigger and integrated into the naphthalimide fluorophore via a carbamate linker to afford a new probe for •OH imaging. •OH treatment induced aromatic hydroxylation and subsequent elimination reaction to release the caged fluorophore, accompanied with a highly specific and sensitive turn-on fluorescence response. Cell imaging results revealed that excess homocysteine triggered overwhelming •OH production, which was mediated by N-methyl-d-aspartate receptor and NADPH oxidase, and the resultant •OH stress further initiated neuronal ferroptosis, also confirmed by western blot analyses. Additionally, hyperhomocysteinemic mouse models were established, and Alzheimer-like dementia of the mice was observed from behavioral tests. Most importantly, with this probe, cerebral •OH fluctuation was in situ visualized in live mice, which positively correlated with the severity of Alzheimer-like dementia induced by hyperhomocysteinemia. These results reveal that cerebral •OH stress may be the critical nexus linking hyperhomocysteinemia and Alzheimer's disease. This work provides a robust fluorescence probe for in situ visualizing the cerebral •OH fluctuations and illuminating critical insights into •OH contributions in brain disorders.

Design a Cu2+ Fluorescent Probe Derived from Pyrene

A Cu2+ probe based on pyrene derivatives was introduced. Compared to other metal ions, it exhibited a highly selective and sensitive fluorescence response to Cu2+.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk.

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH2-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH2-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH2-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH2-UIO-66 (Zr). The introduction of NH2-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH2-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 μg mL-1, with a detection limit of 0.012 μg mL-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH2-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

Eu3+ Coordinated Hyperbranched Polysiloxane with Multicolor Emission and Long Fluorescence Lifetime†

Comprehensive SummaryHyperbranched polysiloxanes have attracted increasing interest due to their unique fluorescence properties. However, the relatively short emission wavelength and low fluorescence lifetime are still the main obstacles to their broader application. In this study, we first synthesized a β‐diketone contained hyperbranched polysiloxane with excitation‐dependent multicolor emission. Further through the coordination of HBPSi‐NMDEA with Eu3+ ion, a hybrid luminescent material was prepared. It exhibited not only aggregation‐induced red emission at 613 nm, but also a long fluorescence lifetime of 681.45 μs. Particularly, it showed highly sensitive reversible fluorescence response to temperature variation, thus displaying the potential to be used in fluorescence temperature detection.

Bis-Schiff base cellulosic nanocrystals for Hg (II) removal from aqueous solution with high adsorptive capacity and sensitive fluorescent response

Mercury pollution in aqueous solutions is a severe problem in environmental protection and the contaminated water may cause serious risks to human health. Based on the constant development of adsorptive materials, adsorption technique is widely applied as an efficient and convenient approach to eliminate mercury species from waters. In this work, we report a one-pot procedure to prepare a bis-Schiff base cellulosic adsorbent to integrate the advantages of large adsorptive capacity and excellent fluorescent recognition towards mercury ions. The adsorption experiments demonstrate that sulfydryl-contained cellulosic nanocrystals exhibit specific affinity with mercury species and the adsorption capacity reaches as high as 624.8 mg/g at room temperature. Besides, the introduction of rhodamine moiety endows the material a 19 times enhancement of selective “off-on” fluorescent sensing while exposed to mercury. Additionally, the bifunctional adsorbent material shows high sensitivity towards mercury ions in aqueous solution with detection limits of as low as 8.29 × 10−8 M for fluorescence and 5.9 × 10−9 M for UV–vis spectrum, respectively. The fitting results of the adsorption models indicate a monolayer adsorption during the uptake of mercury ions and the removal process follows the pseudo-second order kinetics. Moreover, density functional theory studies are employed to further understand the adsorptive and responsive mechanisms.

A triphenylamine-based fluorescence probe for detection of hypochlorite in mitochondria

The level of HClO/ClO− in mitochondria is essential to keep the normal function of mitochondria. Therefore, it is meaningful to accurately and quickly monitor ClO− in mitochondria. In this work, a new triphenylamine-based fluorescence probe PDTPA was designed and synthesized, in which pyridinium salt and dicyano-vinyl group were introduced as mitochondria targeting site and reaction site for ClO−. The probe showed high sensitivity and fast fluorescence response (<10 s) in the detection of ClO−. Moreover, the probe PDTPA had good linearity in a wide concentration range of ClO− and its detection limit was calculated as 10.5 μM. Confocal fluorescence images demonstrated that the probe could target mitochondria and track the fluctuations of endogenous/exogenous ClO− levels in the mitochondria of living cells.