Terbium-based coordination polymer nanoparticles for detection of ciprofloxacin in tablets and biological fluids

Tb3+ assisted dithioerythritol stabilized copper nanocluster with AIE behavior for ratiometric fluorescent determination of fluoroquinolones

BACKGROUND

Fluoroquinolones (FQs) are widely used in livestock and poultry industry because of their satisfactory effects in preventing and treating bacterial infection. However, due to irrational use and poor biodegradability, FQs can easily remain in food animals and further enter the human body through the food chain. Therefore, accurate and sensitive detection of FQs residues in animal-origin food is significant. The traditional methods commonly used for FQs detection have some limitations. Ratiometric fluorescence detection technology has the advantages of fast, sensitive, self-correcting, and easy visualization. However, the reports on the use of ratiometric fluorescence probes for FQs detection are limited.

RESULTS

In this work, a novel probe was proposed for ratiometric fluorescent analysis of FQs. In this probe, the fluorescence of dithioerythritol stabilized copper nanoclusters (DTE-Cu NCs) was significantly enhanced due to the Tb3+ triggered aggregation-induced emission effect. FQs bound Tb3+ in Tb3+/DTE-Cu NCs through carboxyl and carbonyl groups, so that Tb3+ was effectively sensitized to emit green fluorescence. However, the red fluorescence of DTE-Cu NCs was not interfered. The fluorescence of the probe transformed from red to green with the increase of FQs concentration. Using norfloxacin (NOR), difloxacin (DIF), and enrofloxacin (ENR) as FQs simulants, this probe showed a sensitive linear response ranged from 0.025 to 22.5 μM, with the limits of detection of 9.6 nM, 9.3 nM, and 7.7 nM. The application potential for FQs detection was verified via a standard addition assay of egg samples with the recovery rate of 90.4 %-114.7 %.

SIGNIFICANT

The fluorescence probe based on Tb3+/DTE-Cu NCs is expected to realize the ratiometric fluorescence sensitive detection of FQs. The establishment of this simple, effective, and rapid detection platform opens up a new way for the detection of FQs residues in animal-origin foods, and also provides a new idea for the design of rapid detection platforms for other hazard factors.

Fluorescent responsive membrane based on terbium coordination polymer and carbon dots with AIE effect for rapid and visual detection of fluoroquinolone

In this study, based on aggregation-induced emission (AIE) effect and antenna effect, a novel portable fluorescent responsive membrane was constructed with red carbon dots (R-CDs) as reference signal and terbium coordination polymer (Tb-AMP CPs) as response signal for visual, instrument-free, and sensitive detection of fluoroquinolones (FQs). Specifically, the fluorescent responsive membrane (R-T membrane) was prepared by physically depositing R-CDs with AIE property and Tb-AMP CPs on the surface of polyvinylidene fluoride filter membranes at ambient temperature. In the presence of FQs, Tb3+ in the Tb-AMP CPs of the prepared membrane coordinated with the β-diketone structure of FQs, which turned on the yellow-green fluorescence through the "antenna effect". As the concentration of FQs increased, the R-T membrane achieved a fluorescent color transition from bright pink to yellow-green. Its visual detection sensitivity for three FQs, including ciprofloxacin, difloxacin, and enrofloxacin, was 0.01 μM, and the detection limits were 7.4 nM, 7.8 nM, and 9.2 nM, respectively, by analyzing the color parameter green. In the residue analysis of FQs in real samples, the constructed membrane also exhibited remarkable anti-interference and reliability, which is of great significance for ensuring the safety of animal-derived food.

A ternary nucleotide-lanthanide coordination nanoprobe for ratiometric fluorescence detection of ciprofloxacin

Ciprofloxacin (CIP) is a widely used broad-spectrum antibiotic and has been associated with various side effects, making its accurate detection crucial for patient safety, drug quality compliance, and environmental and food safety. This study presents the development of a ternary nucleotide-lanthanide coordination nanoprobe, GMP-Tb-BDC (GMP: guanosine 5'-monophosphate, BDC: 2-amino-1,4-benzenedicarboxylic acid), for the sensitive and ratiometric detection of CIP. The GMP-Tb-BDC nanoprobe was constructed by incorporating the blue-emissive ligand BDC into the Tb/GMP coordination polymers. Upon the addition of CIP, the fluorescence of terbium ion (Tb3+ ) was significantly enhanced due to the coordination and fluorescence sensitization properties of CIP, while the emission of the BDC ligand remained unchanged. The nanoprobe demonstrated good linearity in the concentration range of 0-10 μM CIP. By leveraging mobile phone software to analyze the color signals, rapid on-site analysis of CIP was achieved. Furthermore, the nanoprobe exhibited accurate analysis of CIP in actual drug and milk samples. This study showcases the potential of the GMP-Tb-BDC nanoprobe for practical applications in CIP detection.

Terbium-based dual-ligand metal organic framework by diffusion method for selective and sensitive detection of danofloxacin in aqueous medium

A water-dispersible Tb(III)-based metal organic framework (TBP) was produced by diffusion technique using benzene-1,3,5-tricarboxylic acid (BTC) and pyridine as easily accessible ligands at low cost. The as-synthesized TBP with a crystalline structure and rod-shaped morphology has exhibited thermal stability up to 465 °C. Elemental analysis confirmed the presence of carbon, oxygen, nitrogen, and terbium in the synthesized MOF. TBP was used as a fluorescent probe for detection of danofloxacin (DANO) in an aqueous medium with significant enhancement of fluorescence intensity as compared to various fluoroquinolone antibiotics (levofloxacin (LEVO), ofloxacin (OFLO), norfloxacin (NOR), and ciprofloxacin (CIPRO)) with a low detection limit of 0.45 ng/mL (1.25 nm). The developed method has successfully detected DANO rapidly (i.e., response time = 1 min) with remarkable recovery (97.66-101.96%) and a relative standard deviation (RSD) of less than 2.2%. Additionally, TBP showcased good reusability up to three cycles without any significant performance decline. The in-depth mechanistic studies of the density functional theory (DFT) calculations and mode of action revealed that hydrogen bonding interactions and photo-induced electron transfer (PET) are the major factors for the turn-on enhancement behavior of TBP towards DANO. Thus, the present work provides the quick and precise identification of DANO using a new fluorescent MOF (TBP) synthesized via a unique and facile diffusion technique.

Gelatinous lanthanide coordination polymer with aggregation-enhanced antenna effect for ratiometric detection of endogenous alkaline phosphatase

Aggregation-induced emission (AIE) and antenna effect (AE) are two significant behaviors that have attracted increasing attention. However, it is challenging to achieve the synergistic effect of AIE and AE in luminescent materials for more extensive applications. Here, four gelatinous Ln³⁺ coordination polymers (Ln-CPs) are synthesized by self-assembly of ciprofloxacin (CIP), adenosine monophosphate (AMP), and Ln³⁺ ions in aqueous medium. Encouragingly, a remarkable increase in the characteristic fluorescence of Ln³⁺ and a significant decrease in CIP are observed along with increasing concentration of Ln-CPs, which is attributed to the large aggregates formed by self-assembly that strictly constrain the intramolecular motions of antenna ligands, thereby achieving the aggregation-enhanced AE. More meaningfully, Eu-CP not only shows a rice-like morphology at high aggregation state, but also provides an opportunity for the selective detection of alkaline phosphatase (ALP). A new flower-like polymer is formed upon incubating Eu-CP with ALP, accompanied by the fluorescence quenching of Eu³⁺ and recovery of CIP, a ratiometric determination of ALP in the range of 0.1-6.0 U·L^-1 is thus achieved. Additionally, ALP assay in human serum and bioimaging in living cells have been successfully performed. This research opens a new horizon for the fabrication of Ln³⁺-based luminescent materials with promising applications.

A smartphone-integrated light-up lanthanide fluorescent probe for the visual and ratiometric detection of total phosphorus in human urine and environmental water samples

Phosphate (Pi) plays an essential role in aquatic ecosystems as well as in physiological processes. Here, a dual-emission probe for the sensitive, specific and visual analysis of Pi is fabricated by coordinating Eu³⁺ with luminol and 2,6-pyridinedicarboxylic acid (DPA). Pi can significantly enhance the characteristic fluorescence of Eu³⁺ at 615 nm by promoting energy transfer from DPA to Eu³⁺ and reducing the quenching effect of water molecule, luminol with inherent emission at 423 nm further enhances the Eu³⁺ fluorescence. Accordingly, ratiometric detection of Pi can be achieved with the fluorescence ratio F₆₁₅/F₄₂₃ as a function of Pi concentration. Linearity between F₆₁₅/F₄₂₃ and Pi concentration in the range of 0.1-25 μM is shown, and the limit of detection (LOD, 3σ/K) for Pi is 0.027 µM. In addition, a continuous change in the fluorescence color of the probe from blue to red is observed with increasing Pi concentration under a UV lamp, and a smartphone-based visual method is used for the convenient and effective semi-quantitative determination of Pi. The dual-emission probe has been successfully applied to ratiometric and visual analysis of Pi in human urine and environmental water samples, and adequate results are obtained.

Ratiometric rapid distinction of two structurally similar fluoroquinolone antibiotics by a Tb/Eu hydrogel

Norfloxacin and ofloxacin are two frequently prescribed second-generation fluoroquinolone antibiotics with an identical 4-quinolone chromophore and hence, are difficult to distinguish by conventional methods (UV or fluorescence). We have designed a Tb3+/Eu3+/cholate cocktail that enabled us to differentiate these two drugs and rapidly measure their concentrations when present together. Additionally, a Tb3+-cholate gel-based paper sensor was developed to detect and quantify them in a single drug containing system with a limit of detection (LOD) well below 100 nM.

A novel terbium (III) and aptamer-based probe for label-free detection of three fluoroquinolones in honey and water samples

Fluoroquinolones, a family of synthetic broad-spectrum antibiotics, are widely used in clinical medicine, farm animals and aquaculture. Residues of fluoroquinolones in samples have attracted much attention because of growing food safety and public health concerns. Here, a novel Tb³⁺ ion-enrofloxacin aptamer coordination probe was prepared to develop a sensitive and rapid label-free fluorescence assay for specific detection three fluoroquinolones. In presence of the target, Tb³⁺ ion- enrofloxacin aptamer probe specifically bound with enrofloxacin, norfloxacin and ciprofloxacin, leading to a sharp increase in fluorescence emission of the probe. Under the optimized conditions, fluorescence increased linearly in the 1.0-100.0 ng/mL range for the three fluoroquinolones, with 0.053 ng/mL limit of detection for ciprofloxacin, 0.020 ng/mL limit of detection for norfloxacin and 0.061 ng/mL limit of detection for enrofloxacin. Satisfactory recovery (80.10-102.48%) in spiked honey and water samples were obtained for the three fluoroquinolones with relative standard deviations between 0.21% and 5.44% (n = 3).

Ratiometric fluorescence detection of ciprofloxacin using the terbium-based coordination polymers

Herein, a facile self-assembly through adenosine monophosphate (AMP) and luminol with Tb³⁺ was employed to construct a dual-ligand coordinated AMP-Tb-luminol coordination polymers (CPs), which emitted the typical fluorescence of luminol. Based on the sensitization effect of ciprofloxacin (CIP) on the luminescence of Tb³⁺, a ratiometric sensor was fabricated using the fluorescence of luminol as an inert reference. The fluorescent intensity ratios of Tb³⁺ to that of luminol enhanced linearly with the CIP concentration in the range from 5 nM to 2.5 μM with a lower limit of detection of 2 nM. In addition, the proposed ratiometric fluorescent sensor exhibited high selectivity for CIP, which could also be used to detect CIP in human blood serum (HBS) with satisfactory results. To our knowledge, this is the first demonstration of using dual-ligand coordination lanthanide (Ln)-based CPs for ratio-metric CIP assay, and this straightforward strategy may open up a new platform for designing the ratio-metric sensors based on the Ln CPs.

In situ ligand-induced Ln-MOFs based on a chromophore moiety: white light emission and turn-on detection of trace antibiotics

Series novel 3D Ln-MOFs containing both carboxyphenyl and pyridinyl moieties have been constructed. Tb-MOF fluorescence turn-on sensor of levofloxacin solution with highly sensitive and excellent selective was achieved through d-PET approach.

An imine-linked covalent organic framework for renewable and sensitive determination of antibiotic

Lanthanide-functionalized porous organic materials have been the promising candidates in the chemical and biological sensing. Considering the superior thermal and solvent stability of covalent organic frameworks (COFs), the development of lanthanide ions-functionalized COFs based sensing platform is meaningful, while remains to be a challenge. In this work, a new imine-linked COF which provides suitable coordination sites for Tb³⁺ was constructed via the Schiff base reaction between P-phenylenediamine (Pda) and 2,6-Diformylpyridine (Dfp). Benefiting from its high signal-to-noise, the COF@Tb shows excellent ability to determinate ciprofloxacin (CIP) with a detection limit of 3.01 nM. The measurement can maintain good stability in the presence of potential interference or in actual sample. Being washed with ethanol after each measurement, COF@Tb can be recycled for five times. This work provides a novel alternative strategy for efficient construction of lanthanide-grafted COFs and may promote the development of porous organic materials based chemical sensing.

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

pH-Regulated H4TCPE@Eu/AMP ICP Sensor Array and Its Fingerprinting on Test Papers: Toward Point-of-Use Systematic Analysis of Environmental Antibiotics

In this work, 1,1,2,2-tetra(4-carboxylphenyl)ethylene (H₄TCPE) was selected as the guest and incorporated into a Eu/AMP ICP host to establish a "lab-on-an-AIE@Ln/ICP" sensor array for identifying and sensing environmental antibiotics simultaneously. First, on the basis of a theoretical study of the antenna effect and reductive photoinduced charge transfer between the as-prepared H₄TCPE@Eu/AMP ICPs and antibiotics, respectively, the response from the sensitized time-resolved fluorescence of the host and the unique aggregation-induced emission (AIE) of the guest were selected as the main sensing elements for the sensor array. With the regulation of pH, the diverse fluorescence responses for antibiotics with either structural differences (flumequine, oxytetracycline, and sulfadiazine) or structural similarities (oxytetracycline, tetracycline, and doxycycline) were recorded and processed by principal component analysis; systematic analysis of environmental antibiotics was therefore realized. Encouraged by the superior anti-aggregation-caused quenching effect of H₄TCPE@Eu/AMP ICPs on the test strip, the distinct fluorescence color changes of the "lab-on-an-AIE@Ln/ICP" sensor array were further explored with the aid of smartphones. The fingerprinting pattern of the sensor array on test paper eventually holds great potential for the point-of-use systematic analysis of environmental antibiotics even in complicated real samples.

Difunctional covalent organic framework hybrid material for synergistic adsorption and selective removal of fluoroquinolone antibiotics

Due to the low efficiency of traditional sewage treatment methods, the effective removal of zwitterionic fluoroquinolone (FQs) antibiotics is of vital significant for environment protection. In this work, a SO₃H-anchored covalent organic framework (TpPa-SO₃H) was deliberately designed by linking phenolic trialdehyde with triamine through Schiff reaction, then low-content Tb³⁺ ions were loaded onto covalent organic framework according to wet-chemistry immersion dispersion method which benefitting for efficient FQs antibiotics uptaking. Tb@TpPa-SO₃H functionalized with regularly distributed sulfonic acid groups and terbium ions which could provide difunctional binding sites. Tb³⁺ sites could capture carboxylic acid group of FQs molecules according to the complexes coordination effect and sulfonic acid sites play a significant role in the adsorption of FQs molecules through electrostatic interaction with amine group. Tb@TpPa-SO₃H with dual complementary function sites exhibited ultra-fast adsorption kinetics (< 2 min, average over 99% removing rate) and high adsorption capacities of 989, 956, and 998 mg g^-1 for Norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), respectively. Furthermore, Tb@TpPa-SO₃H showed excellent selectivity for the adsorption of FQs in tanglesome system. This work not only explored synergistic adsorption in ion-functionalized 2D covalent organic framework with dual binding sites, but also delineated a promising strategy for the elimination of organic pollutants in environmental remediation.

Simple fluorescence optosensing probe for spermine based on ciprofloxacin-Tb3+ complexation

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2-180 μM with a low limit of detection of 0.17 μM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results.

Bipyridine- and Copper-Functionalized N-doped Carbon Dots for Fluorescence Turn Off-On Detection of Ciprofloxacin

Herein, a fluorescence turn off-on nanosensor has been successfully developed using functionalized N-doped carbon dots (N-CDs) as the label-free sensing probe for the ultrasensitive detection of Cu²⁺ ions first and then ciprofloxacin (CIP), one of the most commonly used antibiotics for disease control, in the presence of bipyridine. The homogeneous and narrowly distributed N-CDs with a mean size of 5.7 nm and a high quantum yield of 84% are fabricated via the hydrothermal method in the presence of citric acid and ethylenediamine as the carbon and nitrogen sources, respectively. The Cu²⁺ ions serve as both analyte and fluorescence quenchers in the sensing platform of N-CDs, and a good linear response to Cu²⁺ in the range of 0.01-0.35 μM with a limit of detection (LOD) of 0.076 nM is observed. Then, 0.35 μM Cu²⁺ is used as the fluorescence quencher of N-CDs to build up the fluorescence turn off-on sensing probe for the detection of CIP using bipyridine (bipy) as the linker for CIP and Cu²⁺ ions. The addition of CIP to the bipy-Cu@N-CD composites triggers the formation of CIP-bipy-Cu conjugate as well as the release of N-CDs, resulting in the recovery of fluorescence intensity after 6 min of incubation. The sensing probe exhibits a two-phase linear response to CIP in the concentration range of 0.05-1 and 1-50 μM with a LOD of 0.4 nM. In addition, the bipy-Cu@N-CD probe shows high sensitivity toward CIP over the 19 other interferences. Good recovery of 96-110% is also observed when 0.1-0.9 μM CIP is spiked into the real samples. Results obtained in this study clearly demonstrate a newly developed sensing platform with rapid detection of metal ions and antibiotics, which can open an avenue to develop highly efficient and robust sensing probes for the detection of metal ions, organic metabolites, and biomarkers in biological applications.

Europium-Pyridinedicarboxylate-Adenine Light-Up Fluorescence Nanoprobes for Selective Detection of Phosphate in Biological Fluids

Phosphate (Pi) plays important roles in various physiological processes. Its quantification in biological fluids is highly crucial for timely warning of Pi accumulation. Herein, an europium (Eu)-based coordination polymer nanoprobe (Eu/DPA/Ade) is prepared by coordinating 2,6-pyridinedicarboxylic acid (2,6-DPA) and adenine (Ade) with Eu³⁺. Eu/DPA/Ade exhibits light-up fluorescence response to Pi. The strong coordinating interaction between Eu³⁺ and O atoms in the Pi group not only shortens the Eu³⁺-ligand distance to improve the energy transfer from 2,6-DPA to Eu³⁺ but also attenuates the fluorescence quenching from water molecules in the coordinating sphere of Eu³⁺. Eu/DPA/Ade produces red emission at λ_em 618 nm via the "antenna effect". The coligand Ade further promotes the fluorescent emission. The selective recognition of Pi within 10-60 μM is achieved with a detection limit of 4.65 μM. In addition, a certain level of Pi (100-170 μM) causes an exponential increment on the fluorescence of Eu/DPA/Ade and makes it feasible for visual estimation of Pi under irradiation by an ultraviolet lamp at 254 nm. The quantitative detection and visual estimation of Pi in human urine and saliva have been demonstrated.

Quinolone Complexes with Lanthanide Ions: An Insight into their Analytical Applications and Biological Activity

Quinolones comprise a series of synthetic bactericidal agents with a broad spectrum of activity and good bioavailability. An important feature of these molecules is their capacity to bind metal ions in complexes with relevant biological and analytical applications. Interestingly, lanthanide ions possess extremely attractive properties that result from the behavior of the internal 4f electrons, behavior which is not lost upon ionization, nor after coordination. Subsequently, a more detailed discussion about metal complexes of quinolones with lanthanide ions in terms of chemical and biological properties is made. These complexes present a series of characteristics, such as narrow and highly structured emission bands; large gaps between absorption and emission wavelengths (Stokes shifts); and long excited-state lifetimes, which render them suitable for highly sensitive and selective analytical methods of quantitation. Moreover, quinolones have been widely prescribed in both human and animal treatments, which has led to an increase in their impact on the environment, and therefore to a growing interest in the development of new methods for their quantitative determination. Therefore, analytical applications for the quantitative determination of quinolones, lanthanide and miscellaneous ions and nucleic acids, along with other applications, are reviewed here.

A turn-on fluorescence probe Eu3+ functionalized Ga-MOF integrated with logic gate operation for detecting ppm-level ciprofloxacin (CIP) in urine

The threatening of antibiotic drugs for human and environment is being paid more and more attention. Ciprofloxacin (CIP), a strong quinolone antibiotic drug widely used in therapeutic treatments, is the most frequently detected in surface waters among the fluoroquinolones, which represents animal and human health risks. A novel highly fluorescent Ga-based hybrid (Eu³⁺@1) has been synthesized based on metal-organic framework (MOF) by encapsulating lanthanide cations Eu³⁺ in its channels. The as-synthesized compound possesses excellent water and pH-independent stability. It displays week red luminescence of Eu³⁺ in itself and can sense the CIP concentration as turn-on fluorescent probe in the human urine. With addition of CIP, the evident luminescence enhancement is clearly observed from the Eu³⁺@1. Linear correlation between the fluorescence intensity and the concentration of CIP is investigated, proving the excellent performance of Eu³⁺@1 in the detection of CIP with linear range (0.01-0.2 mg/mL) and low detection limit (2.4 ppm or 2.4 μg/mL). The response time is also very quick, less than 3 min. Based on these findings, we introduce AND logic gate strategy to the probe. The input of the logic gates (0, 1), (0, 1, 1), (1, 1, 1) cause the different outputs of CIP determination "LOW" (<25 ppm),"NORMAL" (25-76 ppm), "HIGH" (>76 ppm), respectively. The novel strategy can be applied for a real-time CIP concentration evaluation by intelligent discrimination.

Determination of norfloxacin in urine and pharmaceutical samples using terbium doped zinc sulphide nanomaterials-sensitized fluorescence method

Highly crystalline polyethylene glycol (PEG) coated Tb³⁺ doped ZnS nanoparticles have been synthesized and successfully used for norfloxacin sensing. The crystallographic and morphological analyses of PEG coated Tb³⁺ doped ZnS nanoparticles were performed by X-ray diffraction and Transmission electron microscopy, respectively. The confirmation of Tb³⁺ doping in ZnS host matrix was done by emission spectroscopy and energy dispersive X-ray spectroscopy. Further, the interaction of norfloxacin with PEG coated Tb³⁺ doped ZnS nanomaterials was confirmed by optical analysis: spectrophotometrically and spectrofluorimetrically. Norfloxacin sensing was measured by luminescence intensity which increased with increase in concentration of norfloxacin in range from 2.0 × 10^-9-8.0 × 10^-7 mol L^-1, with its correlation coefficient 0.9991. The detection limit of proposed method was 0.05 × 10^-9 mol L^-1. The developed luminescence method was successfully applied for the determination of norfloxacin using PEG coated Tb³⁺ doped ZnS nanoparticles in urine and pharmaceutical samples.

CdSe/ZnS quantum dots coated with carboxy-PEG and modified with the terbium(III) complex of guanosine 5'-monophosphate as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of acid phosphatase activity

A ratiometric fluorometric method is described for the determination of arsenate via its inhibitory effect on the activity of the enzyme acid phosphatase. A nanoprobe was designed that consists of CdSe/ZnS quantum dots (QDs) coated with the terbium(III) complex of guanosine monophosphate (Tb-GMP). The nanoprobe was synthesized from carboxylated QDs, Tb(III) and GMP via binding of Tb(III) by both the carboxy and the phosphate groups. The nanoprobe, under single-wavelength excitation (at 280 nm), displays dual (red and green) emission, with peaks at around 652 nm from the QDs, and at 547 nm from the Tb-GMP coordination polymers. It is shown to be a viable nanoprobe for fluorometric determination of As(V) detection through it inhibitory action on the activity of acid phosphatase (ACP). The enzyme destroys the Tb-GMP structure via hydrolysis of GMP, and hence the fluorescence of the Tb-GMP complex is quenched. In contrast, the fluorescence of the CdSe/ZnS QDs remains inert to ACP. It therefore can serve as an internal reference signal. In the presence of arsenate (an analog of phosphate), the activity of ACP is inhibited due to competitive binding. Thus, hydrolysis of GMP is prevented. These findings were used to design a ratiometric fluorometric method for the quantification of As(V). The ratio of fluorescences at 547 and 652 nm increases linearly in the 0.5 to 200 ppb As(V) concentation range, and the limit of detection is 0.39 ppb. Under a UV lamp, the probe shows distinguishable color from green to red on increasing the concentration of As(V). Graphical abstract Schematic illustration of CdSe/ZnS quantum dot coated with carboxy-PEG and modified with the terbium(III)-GMP complex as a fluorescent nanoprobe for ratiometric determination of arsenate via its inhibition of ACP activity.

2D europium coordination polymer as a regenerable fluorescence probe for efficiently detecting fipronil

Recently, considerable attention has been paid to European eggs that were found to contain the poisonous insecticide fipronil. Excessive consumption of fipronil can harm the human body, in particular, the liver, thyroid, nervous system and kidneys. As a consequence, there is an urgent need to develop a method to detect fipronil. In this work, a lanthanide coordination polymer [Eu(SIP)(H2O)4]n (1) (NaH2SIP = 5-sulfoisophthalic acid monosodium salt) was synthesized and characterized by single-crystal X-ray crystallography, elemental analysis, infrared spectrum and powder X-ray diffractions. The X-ray studies show that 1 is a two-dimensional layered structure, which is constructed of fused {[Eu(H2O)4]3(SIP)3} pseudo-hexagonal grids. The luminescence properties of 1 exhibit effective recognition for fipronil in methanol solution. Furthermore, a wide linear range (10-6-10-4 M), a low detection limit of 0.8 μM, high selectivity and excellent recyclability, reveal that 1 can potentially act as a luminescence-based sensor for quantitative and highly sensitive detection of fipronil. To the best of our knowledge, it is the first time that a metal-organic coordination polymer, as a fluorescent-based probe, has been used for the detection of fipronil. Moreover, fluorescent-based test papers of 1 have also been prepared, which can be regarded as a simple and practical method for detecting fipronil.

Nucleobases, nucleosides, and nucleotides: versatile biomolecules for generating functional nanomaterials

The incorporation of biomolecules into nanomaterials generates functional nanosystems with novel and advanced properties, presenting great potential for applications in various fields. Nucleobases, nucleosides and nucleotides, as building blocks of nucleic acids and biological coenzymes, constitute necessary components of the foundation of life. In recent years, as versatile biomolecules for the construction or regulation of functional nanomaterials, they have stimulated interest in researchers, due to their unique properties such as structural diversity, multiplex binding sites, self-assembly ability, stability, biocompatibility, and chirality. In this review, strategies for the synthesis of nanomaterials and the regulation of their morphologies and functions using nucleobases, nucleosides, and nucleotides as building blocks, templates or modulators are summarized alongside selected applications. The diverse applications range from sensing, bioimaging, and drug delivery to mimicking light-harvesting antenna, the construction of logic gates, and beyond. Furthermore, some perspectives and challenges in this emerging field are proposed. This review is directed toward the broader scientific community interested in biomolecule-based functional nanomaterials.

Terbium (III) coordination polymer-copper (II) compound as fluorescent probe for time-resolved fluorescence 'turn-on' detection of hydrogen sulfide

With recognition of the biological importance of hydrogen sulfide (H₂ S), we present a simple and effective fluorescent probe for H₂ S using a Tb³⁺ coordination polymer-Cu²⁺ compound (DPA/Tb/G-Cu²⁺ ). Dipicolinic acid (DPA) and guanosine (G) can coordinate with Tb³⁺ to form a macromolecular coordination polymer (DPA/Tb/G). DPA/Tb/G specifically binds to Cu²⁺ in the presence of coexisting cations, and obvious fluorescence quenching is observed. The quenched fluorescence can be exclusively recovered upon the addition of sulfide, which is measured in the mode of time-resolved fluorescence. The fluorescence intensities of the DPA/Tb/G-Cu²⁺ compound enhance linearly with increasing sulfide concentrations from 1 to 30 μM. The detection limit for sulfide in aqueous solution is estimated to be 0.3 μM (at 3σ). The DPA/Tb/G-Cu²⁺ compound was successfully applied to sense H₂ S in human serum samples and exhibited a satisfactory result. It displays some desirable properties, such as fast detection procedure, high selectivity and excellent sensitivity. This method is very promising to be utilized for practical detection of H₂ S in biological and environmental samples.

A highly zinc-selective ratiometric fluorescent probe based on AIE luminogen functionalized coordination polymer nanoparticles

A highly zinc-selective ratiometric fluorescent probe was developed based on the cation exchange process of Tb-HDBB-CPNs with Zn²⁺.

Detection of Ciprofloxacin in Urine through Sensitized Lanthanide Luminescence

Ciprofloxacin, a fluoroquinolone antibiotic, is widely used for the treatment of bacterial infection in humans due to its broad antibacterial spectrum. An excessive use or overdose of ciprofloxacin on the other hand can cause several adverse effects not only to humans but also to microorganisms. Unabsorbed ciprofloxacin in the body is mostly excreted through urine and finally goes to the environment, providing a drug resistance pressure on bacteria. Hence a simple and efficient detection method of ciprofloxacin is necessary, which, for example, can be used to analyze ciprofloxacin content in urine. Although ciprofloxacin itself shows inherent fluorescence, direct fluorescent detection of ciprofloxacin in raw urine sample is difficult due to autofluorescence of urine by other components. Herein we report that a Tb(III) complex of DO3A (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) can be efficiently sensitized by ciprofloxacin to emit luminescence separately from the urine autofluorescence wavelength region. Tb-DO3A shows excellent sensitivity with a detection limit of three parts per billion in aqueous buffer solution. Further, Tb-DO3A is used to detect ciprofloxacin with high sensitivity and selectivity in a raw urine sample without any purification or separation procedures in the concentrations ranging from 1 µg·mL⁻¹ to 50 µg·mL⁻¹. The direct measurement of ciprofloxacin excreted in urine may be used to control overdose of the drug.

Artificial tongue based on metal-biomolecule coordination polymer nanoparticles

We construct an array-based recognition system (the so-called artificial tongue) through the self-assembly of nucleotides, dyes and lanthanide ions. Metal ions are selected as model analytes for verifying its discrimination ability. The work provides valuable insights into the application and development of biomolecule-based materials.

A turn on fluorescent sensor based on lanthanide coordination polymer nanoparticles for the detection of mercury(ii) in biological fluids

Im-quenched fluorescence of Eu/IPA CPNPs can be recovered upon the addition of Hg²⁺ through the formation of a Hg/Im complex.

Turn-on fluorescence detection of ciprofloxacin in tablets based on lanthanide coordination polymer nanoparticles

Metal–organic coordination polymers (MOCPs) have emerged as a new family of functional nanomaterials.

Surfactant-mediated morphology and fluorescent properties of amino acids-based lanthanide coordination polymers

The morphologies and fluorescent properties of Phe/Tb CPs can be mediated by surfactants with different characteristics.

Dynamic self-assembly of coordination polymers in aqueous solution

The construction of supramolecular polymers has been intensively pursued because the nanostructures formed through weak non-covalent interactions can be triggered by external stimuli leading to smart materials and sensors. Self-assemblies of coordination polymers consisting of metal ions and organic ligands in aqueous solution also provide particular contributions in this area. The main motivation for developing those coordination polymers originates from the value-added combination between metal ions and ligands. This review highlights the recent progress of the dynamic self-assembly of coordination polymers that result from the sophisticated molecular design, towards fabricating stimuli-responsive systems and bio-related materials. Dynamic structural changes and switchable physical properties triggered by various stimuli are summarized. Finally, the outlook for aqueous nanostructures originated from the dynamic self-assembly of coordination polymers is also presented.

Functionalized lanthanide coordination polymer nanoparticles for selective sensing of hydrogen peroxide in biological fluids

The fluorescence of Phe/Tb CPNPs functionalized with CPBA (Phe/Tb-CPBA CPNPs) was selectively quenched upon the addition of H₂O₂.