Ratiometric Luminescence Probe Research Articles

A novel iridium(III) complex-based ratiometric luminescence probe for monitoring hydrogen sulfide in living cells and zebrafish

Hydrogen sulfide exhibits crucial functions in many biological and physiological processes. The abnormal levels of H2S have been revealed to be associated with numerous human diseases. The majority of existing fluorescent probes toward H2S may still need to be improved in terms of single output signal, water solubility, biotoxicity and photostability. The construction of a ratiometric fluorescent probe based on metal complex is one effective strategy for avoiding the mentioned problems for precisely detecting H2S. Herein, we report an iridium(III) complex-based ratiometric luminescence probe (Ir-PNBD), which is designed by coupling the 7-nitro-2,1,3-benzoxadiazoles (NBD) to one of the bipyridine ligands of Ir (III) complex luminophore through a piperazition moiety. Ir-PNBD owns high selectivity and sensitivity toward H2S, and an excellent ability to target mitochondria. Moreover, Ir-PNBD was further successfully utilized to visualize exogenous and endogenous H2S in HeLa cells and zebrafish. Our work offers new opportunities to gain deeper insights into the construction of transition metal complex-based ratiometric luminescent probes and expands their applications in biomedical imaging and disease diagnosis.

Ratiometric luminescence detection of H2O2 in food samples using a terbium coordination polymer sensitized with 3-carboxyphenylboronic acid

A ratiometric luminescent probe was fabricated using adenosine monophosphate (AMP) as a bridging ligand and 3-carboxyphenylboronic acid (3-CPBA) as the sensitizer and functional ligand that allowed the probe to recognize hydrogen peroxide (H2O2). The probe was labeled AMP-Tb/3-CPBA. Adding H2O2 caused the nonluminescent 3-CPBA to be converted into 3-hydroxybenzoic acid, which strongly luminesces at 401 nm. This meant that adding H2O2 decreased the AMP-Tb/3-CPBA luminescence intensity at 544 nm and caused luminescence at 401 nm. The 401 and 544 nm luminescence intensity ratio (I401/I544) was strongly associated with the H2O2 concentration between 0.1 and 60.0 μM, and the detection limit was 0.23 μM. Dual emission reverse-change ratio luminescence sensing using the probe allowed environmental effects to be excluded and the assay to be very selective. We believe that the results pave the way for the development of new functionalized lanthanide coordination polymers for use in luminescence assays.

Ratiometric fluorescent sensing of pyrophosphate with sp³-functionalized single-walled carbon nanotubes

Inorganic pyrophosphate is a key molecule in many biological processes from DNA synthesis to cell metabolism. Here we introduce sp3-functionalized (6,5) single-walled carbon nanotubes (SWNTs) with red-shifted defect emission as near-infrared luminescent probes for the optical detection and quantification of inorganic pyrophosphate. The sensing scheme is based on the immobilization of Cu2+ ions on the SWNT surface promoted by coordination to covalently attached aryl alkyne groups and a triazole complex. The presence of Cu2+ ions on the SWNT surface causes fluorescence quenching via photoinduced electron transfer, which is reversed by copper-complexing analytes such as pyrophosphate. The differences in the fluorescence response of sp3-defect to pristine nanotube emission enables reproducible ratiometric measurements in a wide concentration window. Biocompatible, phospholipid-polyethylene glycol-coated SWNTs with such sp3 defects are employed for the detection of pyrophosphate in cell lysate and for monitoring the progress of DNA synthesis in a polymerase chain reaction. This robust ratiometric and near-infrared luminescent probe for pyrophosphate may serve as a starting point for the rational design of nanotube-based biosensors.

A dual-emission ratiometric luminescence probe based on Zr-MOFs for the efficient detection of Cu2+ in aqueous solutions

A novel dual-emission ratio luminescent probe (Eu(DPA)3@UIO-66-NH2) for the detection of Cu[Formula: see text] in an aqueous solution was successfully prepared by linking the Zr-MOFs material UIO-66-NH2 with the lanthanide complex Na3[Eu(DPA)3] through the interaction between functional groups. The synthesized Eu(DPA)3@UIO-66-NH2 inherits the advantages of MOFs and lanthanide complexes, and it not only has excellent luminescence performance but also shows good dispersion and structural stability in aqueous solution. The characteristics of dual-emission light can achieve specific ratiometric luminescence detection of Cu[Formula: see text]. In addition, the probe exhibited high sensitivity for the detection of Cu[Formula: see text]with a detection limit as low as 0.89 [Formula: see text]M. It can provide an efficient and stable platform for the convenient and rapid detection of Cu[Formula: see text] in aqueous solutions and has the potential for development applications.

FRET Luminescent Probe for the Ratiometric Imaging of Peroxynitrite in Rat Brain Models of Epilepsy-Based on Organic Dye-Conjugated Iridium(III) Complex.

Epilepsy is a chronic neurological disorder characterized by recurrent seizures globally, imposing a substantial burden on patients and their families. The pathological role of peroxynitrite (ONOO-), which can trigger oxidative stress, inflammation, and neuronal hyperexcitability, is critical in epilepsy. However, the development of reliable, in situ, and real-time optical imaging tools to detect ONOO- in the brain encounters some challenges related to the depth of tissue penetration, background interference, optical bleaching, and spectral overlapping. To address these limitations, we present Ir-CBM, a new one-photon and two-photon excitable and long-lived ratiometric luminescent probe designed specifically for precise detection of ONOO- in epilepsy-based on the Förster resonance energy transfer mechanism by combining an iridium(III) complex with an organic fluorophore. Ir-CBM possesses the advantages of rapid response, one-/two-photon excitation, and ratiometric luminescent imaging for monitoring the cellular levels of ONOO- and evaluating the effects of different therapeutic drugs on ONOO- in the brain of an epilepsy model rat. The development and utilization of Ir-CBM offer valuable insights into the design of ratiometric luminescent probes. Furthermore, Ir-CBM serves as a rapid imaging and screening tool for antiepileptic drugs, thereby accelerating the exploration of novel antiepileptic drug screening and improving preventive and therapeutic strategies in epilepsy research.

A ratiometric luminescence probe based on lanthanide metal–organic framework@polyethyleneimine for sensitive and selective detection of Cu2+ and Fe3+

The development of probes for the detection of multiple heavy metal ions holds the nonnegligible practical significance for ensuring public and environment safety. In this work, a ratiometric luminescence probe was proposed for the detection Cu2+ and Fe3+ based lanthanide metal–organic framework@polyethyleneimine (Ln-MOF@PEI). The formation of the complexes between PEI and Cu2+ enhances the quenching efficiency of MOF through a combination of inner filter effect and energy transfer, surpassing the observed quenching efficiency with Fe3+. The emission intensity ratio between Tb3+ and the ligands exhibits a decreasing trend with increasing Cu2+ concentration, while it rises with increasing Fe3+ concentration. It allows for the discrimination between Cu2+ and Fe3+ based on their distinct quenching mechanisms. The assay performance of Ln-MOF@PEI probes was evaluated comprehensively. The limit of detection for Cu2+ and Fe3+ reaches at 9.7 nM and 37.4 nM, respectively. The probe demonstrates acceptable selectivity by effectively avoiding interference from common cations and anions. The detection range covers a wide concentration range from nanomoles to millimoles. Overall, the luminescence probe is expected to meet the requirements of accurate quantification for Cu2+ and Fe3+ in the various application scenarios.

Ratiometric lysosome-targeting luminescent probe based on a coumarin-ruthenium(II) complex for formaldehyde detection and imaging in living cells and mouse brain tissues.

Ratiometric luminescence probes have attracted widespread attention because of their self-calibration capability. However, some defects, such as small emission shift, severe spectral overlap and poor water solubility, limit their application in the field of biological imaging. In this study, a unique luminescence probe, Ru-COU, has been developed by combining tris(bipyridine)ruthenium(II) complex with coumarin derivative through a formaldehyde-responsive linker. The probe exhibited a large emission shift (Δλ>100nm) and good water solubility, achieving ratiometric emission responses at 505nm and 610nm toward formaldehyde under acidic conditions. Besides, ratiometric luminescence imaging of formaldehyde in living cells and Alzheimer disease mouse's brain slices demonstrates the potential value of Ru-COU for the diagnosis and treatment of formaldehyde related diseases.

A ratiometric luminescence probe for selective detection of Ag+ based on thiolactic acid-capped gold nanoclusters with near-infrared emission and employing bovine serum albumin as a signal amplifier.

When thiolactic acid-capped gold nanoclusters (AuNCs@TLA) with strong near-infrared (NIR, 800nm) emission were applied to detect metal ions, only Ag+ induced the generation of two new emission peaks at 610 and 670nm in sequence and quenching the original NIR emission. The new peak at 670nm generated after the 800-nm emission disappeared utterly. The ratiometric and turn-on responses showed different linear concentration ranges (0.10-4.0μmol·L-1 and 10-50μmol·L-1) toward Ag+, and the limit of detection (LOD) was 40nmol·L-1. Especially, the probe exhibited extremely high selectivity and strong anti-interference from other metal ions. Mechanism studies showed that the novel responses were attributed to the anti-galvanic reaction of AuNCs to Ag+ and formation ofbimetallic nanoclusters. Thetwo new emission peaks were due to the composition change and size growth of the metal core. Besides, bovine serum albumin (BSA) has been employed as a signal amplifier based on the assembly-induced emission enhancement properties of AuNCs, which improved the LOD to 10nmol·L-1. Moreover, the ratiometric method is feasible for Ag+ detection in diluted serum with high recovery rates, showing large application potential in the biological system. The present study supplies a novel ratiometric probe forAg+ with a two-stage response and provides a novel signal amplifier of BSA, which will facilitate and promote the application of NIR-emitted metal nanoclusters in biological system.

Tuning the Thermometric Features in 1D Luminescent EuIII and TbIII Coordination Polymers through Different Bridge Phosphine Oxide Ligands.

TbIII and EuIII systems have been investigated as ratiometric luminescent temperature probes in luminescent coordination polymers due to TbIII → EuIII energy transfer (ET). To help understand how ion-ion separation, chain conformation as well as excitation channel impact their thermometric properties, herein, [Eu(tfaa)3(μ-L)Tb(tfaa)3]n one-dimensional (1D) coordination polymers (tfaa- = trifluoroacetylacetonate, and L = [(diphenylphosphoryl)R](diphenyl)phosphine oxide, R = ethyl - dppeo - or butyl - dppbo) were synthesized. The short μ-dppeo bridge ligand leads to a more linear 1D polymeric chain, while the longer μ-dppbo bridge leads to tighter packed chains. As the temperature rises from 80 K, upon direct TbIII excitation at 488 nm, the TbIII emission intensity decreases, while the EuIII emission intensity increases after 160 and 200 K when L = dppeo or dppbo, respectively. The temperature-dependent emission intensities, due to TbIII → EuIII ET, enable the development of ratiometric luminescent temperature probes featuring maximum relative thermal sensitivity up to 3.8% K-1 (250 K, L = dppbo, excitation at 488 nm). On the other hand, the same system displays maximum thermal sensitivity up to 3.5% K-1 (323 K) upon ligand excitation at 300 nm. Thus, by changing the excitation channel and bridge ligand that leads to modification of the polymer conformations, the maximum relative thermal sensitivity can be tuned.

Composite Eu-MOF@CQDs “off & on” ratiometric luminescent probe for highly sensitive chiral detection of l-lysine and 2-methoxybenzaldehyde

The high amount of l-lysine can increase the potential risk of cardiovascular disease. Additionally, 2-methoxy benzaldehyde (2-MB) has high toxicity and can easily pollute the environment. In this work, carbon quantum dots (CQDs) can be encapsulated into Eu-BTB (H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), forming the multi-emission composite material Eu-BTB@CQDs. It has two emissions peaks (617 nm for Eu and 470 nm for CQDs). Eu-BTB@CQDs can be applied as bi-functional ratiometric “off & on” luminescent sensor for l-lysine and 2-MB with high sensitivity and selectivity, the low limit of detection (LOD) for l-lysine is 3.68 µmol/L and for 2-MB is 0.54 µmol/L, respectively. Additionally, Eu-BTB@CQDs can quantitatively discriminate l-lysine in the mixed d- and l-lysine water solutions (five different concentrations ratio of l/d-lysine has been set) makes the chiral detection of l-lysine are more meaningful. On the other hand, Eu-BTB@CQDs also can detect 2-MB over 4-methoxybenzaldehyde (4-MB) with high selectivity. Further the detection of 2-MB and l-lysine in the lake water real samples with the reasonable recovery rate. Finally, the detection mechanisms for l-lysine and 2-MB were also investigated and discussed in detail.

Mitochondria-Targetable Ratiometric Time-Gated Luminescence Probe Activated by Selenocysteine for the Visual Monitoring of Liver Injuries.

Liver injury can result from various risk factors including diabetes, virus, alcohol, drugs, and other toxins, which is mainly responsible for global mortality and morbidity. Selenocysteine (Sec), as the main undertaker of selenium function in the life system, features prominently in a series of hepatic injuries and has close association with the pathological progression of liver injuries. Here, we report a mitochondria-targetable lanthanide complex-based probe, Mito-NPTTA-Tb3+/Eu3+, that can be used for accurately determining Sec in live cells and laboratory animals via the ratiometric time-gated luminescence (TGL) technique. This probe is composed of 2,2':6',2″-terpyridine-Tb3+/Eu3+ mixed complexes as the luminophore, 2,4-dinitrophenyl (DNP) as the responsive moiety and a lipophilic triphenylphosphonium cation (PPh3+) as the mitochondria-targeting moiety. Upon reaction with Sec, accompanied by the cleavage of DNP from the probe molecule, the I540/I690 ratio of the probe increased by 55 times, which enabled Sec to be detected with the ratiometric TGL method. After being incubated with living cells, the probe molecules were selectively accumulated in mitochondria to allow the mitochondrial Sec to be successfully imaged under the ratiometric TGL mode. Importantly, using this probe coupled with the ratiometric TGL imaging technique, the fluctuations of liver Sec in various liver injuries of model mice induced by diabetes, drug, toxin, and alcohol were precisely monitored, revealing that Sec plays an important antioxidant role during the oxidative stress process in liver injury, and the Sec levels have a close interrelationship with the degree of liver injury. All the results suggest that the new probe Mito-NPTTA-Tb3+/Eu3+ could be a potential tool for the accurate diagnosis of liver injury.

Tough, Self-Healing, and UV Light-Switchable Luminescent Hydrogels with Reversible Stimuli-Responsive Properties for Cu2+

Stimuli-responsive luminescent hydrogels (LHs) are of great potential for applications in advanced luminescent sensors; however, structural optimizations and challenges in implementation still remain in their practical applications. Herein, we reported a promising and cooperative strategy to prepare smart LH actuators. Lanthanide(III)-based complexes (LnCs) and sulfur quantum dots (S-QDs) in this contribution are constructed in a cooperative manner; that is, (1) a noncovalent hydrogen bonding model between polyethylene glycol (PEG) in S-QDs and polyurethane (PU) endows LHs with interwoven double networks and improved the mechanical properties and (2) LnCs and S-QDs are two excellent emitting centers with different luminescent excitation properties, leading to the modulating emission colors of LHs by varying the UV irradiation between 254 and 365 nm. Meanwhile, the resultant LHs containing 3.26 wt % of PU possess good mechanical performance and self-healing capability. As a proof of application in stimuli response, our LHs can be served as a ratiometric luminescence probe to electively detect Cu2+ via exponentially correlating the emission intensity ratio of LnCs and S-QDs to the Cu2+ concentration. Remarkably, the obtained LHs also show reversible luminescence “On/Off” switch upon alternate exposure to Cu2+/glutathione (GSH) under 254 nm, while no obvious luminescent variation is observed under 365 nm.

Interfacial self-assembly of terbium complex modified graphitic carbon nitride-silica ternary nanocomposites as an improved ratiometric luminescent probe

Interfacial self-assembly of terbium complex modified graphitic carbon nitride-silica ternary nanocomposites as an improved ratiometric luminescent probe

Single-center LnIII ratiometric luminescent temperature probes based on singlet → singlet and singlet → triplet sensitizations

A new strategy for the development of ratiometric luminescent temperature probes using a single lanthanide ion based on two different excitation channels arising from spin-allowed singlet → singlet and direct spin forbidden singlet → triplet transitions.

A simple paper-based ratiometric luminescent sensor for tetracyclines using copper nanocluster-europium hybrid nanoprobes

Tetracyclines (TCs), as one of the broad-spectrum antibiotics, are widely used to treat bacterial infections. The residues of TCs in animal-origin foods and drinking water have raised safety concerns and affected the public health. Thus, there is a high demand to develop a simple and rapid method for the detection of TCs. In this work, we developed a ratiometric luminescence probe for the sensitive and visualized detection of TCs. Specifically, tannic acid-stabilized copper nanoclusters (TA-CuNCs) with blue emission at 433 nm were synthesized. The luminescence of TA-CuNCs attenuated partially by the europium ions (Eu3+) due to the aggregation-induced quenching. When TCs were added to the TA-CuNCs-Eu3+ system, the luminescence of TA-CuNCs at 433 nm can be further quenched by the inner-filter effect, and the characteristic luminescence of Eu3+ at 617 nm emerged due to the formation of Eu3+-TCs complex. The ratio of the luminescence at 617 nm–433 nm increased linearly to the concentration of TCs. Additionally, we demonstrated the detection of oxytetracycline in real samples such as tap and lake water, milk, pharmaceutical industry wastewater, honey and soil extract with high recovery rate (97.25%–103.44%). Furthermore, a portable paper device is fabricated by the luminescent probe to conduct the on-site analysis of TCs.

Using Native Chemical Ligation for Site-Specific Synthesis of Hetero-bis-lanthanide Peptide Conjugates: Application to Ratiometric Visible or Near-Infrared Detection of Zn2.

The interest in ratiometric luminescent probes that detect and quantify a specific analyte is growing. Owing to their special luminescence properties, lanthanide(III) cations offer attractive opportunities for the design of dual-color ratiometric probes. Here, the design principle of hetero-bis-lanthanide peptide conjugates by using native chemical ligation is described for perfect control of the localization of each lanthanide cation within the molecule. Two zinc-responsive probes, r-LZF1Tb|Cs124|Eu and r-LZF1Eu|Cs124|Tb are described on the basis of a zinc finger peptide and two DOTA (DOTA=1,4,7,10-tetraaza-cyclododecane-1,4,7,10-tetraacetic acid) complexes of terbium and europium. Both display dual-color ratiometric emission in response to the presence of Zn2+ . By using a screening approach, anthracene was identified for the sensitization of the luminescence of two near-infrared-emitting lanthanides, Yb3+ and Nd3+ . Thus, two novel zinc-responsive hetero-bis-lanthanide probes, r-LZF3Yb|Anthra|Nd and r-LZF3Nd|Anthra|Yb were assembled, the former offering a neat ratiometric response to Zn2+ with emission in the near-infrared around 1000 nm, which is unprecedented.

Precise Monitoring of Drug-Induced Kidney Injury Using an Endoplasmic Reticulum-Targetable Ratiometric Time-Gated Luminescence Probe for Superoxide Anions.

Drug-induced acute kidney injury (AKI), caused by renal drug metabolism, has been considered to be a major barrier in drug development and clinical treatment. Among various drugs, anticancer drugs, cisplatin, and aminoglycoside antibiotic gentamicin, are known to be able to induce excessive or unfolded accumulation of proteins in the endoplasmic reticulum (ER) of cells, leading to ER stress. Meanwhile, reactive oxygen species (ROS) are formed, and superoxide anion (O2•-), the first produced ROS, is a key species to induce the AKI. Due to the lack of appropriate tools, the early diagnosis of AKI induced by cisplatin, gentamicin, or other drugs is still a crucial challenge. Herein, we report a lanthanide complex-based ER-targetable luminescence probe for O2•-, ER-(4'-trifluoromethanesulfonyloxy-2,2':6',2''-terpyridine-6,6''-diyl)bis(methylenenitrilo)tetrakis (aceticacid) (NFTTA)-Eu3+/Tb3+, for the sensitive monitoring of drug-induced AKI via mapping the generation of O2•- in live cells and laboratory animals. Using this probe coupled with the ratiometric time-gated luminescence (RTGL) imaging technique, the changes of O2•- level in the ER of live cells induced by different stimuli were precisely monitored. More importantly, the substantial increases in O2•- levels were observed in the cisplatin- and gentamicin-induced kidney injury of mice. In addition, the protective effects of l-carnitine (LC) and epigallocatechin-3-gallate (EGCG) against cisplatin- and gentamicin-induced nephrotoxicity were visualized and elucidated for the first time. The results demonstrated the potential of ER-NFTTA-Eu3+/Tb3+ for examining and monitoring O2•- in drug-induced AKI and for providing a diagnosis and treatment of nephrotoxicity diseases.

Two-Dimensional Metal-Organic Framework Nanosheets as a Dual Ratiometric and Turn-off Luminescent Probe.

Current research on metal-organic framework (MOF) luminescent sensing probes focuses on the design of three-dimensional bulk-sized MOFs that in return limits their up-close interactions with targeted guest molecules. In this work, we report a two-dimensional (2D) copper-based metal-organic framework, namely, AUBM-6, synthesized via solvothermal method from isonicotinic acid linker and copper(II) ion. The resulting 2D-layered MOF crystals were highly fluorescent in their exfoliated form and, therefore, explored for detecting several solvents, where a ratiometric selectivity was shown toward acetone. Metal ion sensing was also performed, by which fluorescent detection was observed to have the highest turn-off quenching efficiency toward Pd2+.

Mitochondria-Targetable Ratiometric Time-Gated Luminescence Probe for Carbon Monoxide Based on Lanthanide Complexes.

As a critical gasotransmitter, carbon monoxide (CO) has been demonstrated to be related with mitochondrial respiration, but the monitoring of CO in mitochondria remains a great challenge. In this work, a unique ratiometric time-gated luminescence (TGL) probe, Mito-NBTTA-Tb3+/Eu3+, that can specifically respond to mitochondrial CO has been developed. The probe was designed by incorporating a mitochondria-targeting moiety, triphenylphosphonium, into a CO-activatable terpyridine polyacid derivative, 4'-(4-nitrobenzyloxy-2,2':6',2''-terpyridine-6,6''-diyl) bis(methylenenitrilo) tetrakis(acetic acid), for coordinating to Eu3+ and Tb3+ ions to construct lanthanide complex-based probe for ratiometric TGL detection of CO. Upon reaction with CO, accompanied by the conversion of nitro group to amino group, a 1,6-rearrangement-elimination reaction occurs, which leads to the cleavage of 4-nitrobenzyl group from Mito-NBTTA-Tb3+/Eu3+, resulting in the significant increase of Tb3+ emission at 540 nm and moderate decrease of Eu3+ emission at 610 nm. After the reaction, the I540/ I610 ratio was found to be 48-fold enhanced. This feature allowed Mito-NBTTA-Tb3+/Eu3+ to be employed as a ratiometric TGL probe for CO detection with the I540/ I610 ratio as a signal. In addition, the probe showed outstanding mitochondria-localization characteristic, which enabled the probe to be successfully applied to imaging CO within mitochondria of living cells under TGL and ratiometric modes. The application of Mito-NBTTA-Tb3+/Eu3+ was demonstrated by the visualization and quantitative detection of exogenous and endogenous CO in living cells and mouse liver tissue slices, as well as in living Daphnia magna and mice. All of the results suggested the potential of Mito-NBTTA-Tb3+/Eu3+ for the quantitative monitoring of CO in vitro and in vivo.

Dye-Assembled Upconversion Nanocomposite for Luminescence Ratiometric in Vivo Bioimaging of Copper Ions.

Overdose of Cu2+ is associated with multiple diseases, such as Wilson disease, Parkinson disease, and Alzheimer disease. Therefore, detections of Cu2+ in vivo and in vitro are meaningful. Near-infrared fluorescent probes are commonly applied for the detection of Cu2+ in real time. With mono detection signal provided, these probes are not persuasive when applied to complicated biological environments, such as cells and animals. In this report, we conjugated the organic fluorescent probe CYDAC16 with the UCNPs (lanthanide-doped upconversion nanoparticles) to develop a ratiometric luminescent probe for Cu2+. The composite material UCNPs-CYDAC16 provides a ratiometric signal based on an upconversion luminescence 660 and 800 nm. With good sensitivity and selectivity for Cu2+, it works well in vivo and in vitro for the detection of Cu2+. We believe it is promising in further biological applications.