Dye-sensitized lanthanide-doped upconversion nanoprobe for enhanced sensitive detection of Fe3+ in human serum and tap water

Iron ion (Fe3+) detection is crucial for human health since it plays a crucial role in many physiological activities. In this work, a novel Schiff-base functionalized cyanine derivative (CyPy) was synthesized, which was successfully assembled on the surface of upconversion nanoparticles (UCNPs) through an amphiphilic polymer encapsulation method. In the as-designed nanoprobe, CyPy, a recognizer of Fe3+, is served as energy donor and β-NaYF4:Yb,Er upconversion nanoparticles are adopted as energy acceptor. As a result, a 93-fold enhancement of upconversion luminescence is achieved. The efficient energy transfer from CyPy to β-NaYF4:Yb,Er endows the nanoprobe a high sensitivity for Fe3+ in water with a low detection limit of 0.21 μM. Moreover, the nanoprobe has been successfully applied for Fe3+ determination in human serum and tap water samples with recovery ranges of 95 %-105 % and 97 %-106 %, respectively. Moreover, their relative standard deviations are all below 3.72 %. This work provides a sensitive and efficient methodology for Fe3+ detection in clinical and environmental testing.

Rational Design and Biological Application of Hybrid Fluorophores

Fluorophores are considered powerful tools for not only enabling the visualization of cell structures, substructures, and biological processes, but also making for the quantitative and qualitative measurement of various analytes in living systems. However, most fluorophores do not meet the diverse requirements for biological applications in terms of their photophysical and biological properties. Hybridization is an important strategy in molecular engineering that provides fluorophores with complementarity and multifunctionality. This review summarizes the basic strategies of hybridization with four classes of fluorophores, including xanthene, cyanine, coumarin, and BODIPY with a focus on their structure-property relationship (SPR) and biological applications. This review aims to provide rational hybrid ideas for expanding the reservoir of knowledge regarding fluorophores and promoting the development of newly produced fluorophores for applications in the field of life sciences.

A SYBR Green I-based aptasensor for the label-free, fluorometric, and anti-interference detection of MeHg. Anal Bioanal Chem 2024;416:299-311. [PMID: 37932512 DOI: 10.1007/s00216-023-05018-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Methylmercury (MeHg+) is a common form of organic mercury that is substantially more toxic than inorganic mercury and is more likely to accumulate in organisms through biological enrichment. Therefore, developing a method to enable the specific and rapid detection of MeHg+ in seafood is important and remains challenging to accomplish. Herein, a rapid, label-free fluorescence detection method for MeHg+ determination was developed based on SYBR Green I. The detection system implemented "add and measure" detection mode can be completed in 10 min. Under optimal assay conditions, the detection platform showed a linear relationship with the concentration of MeHg+ within 1-50 nM (Y = 8.573x + 42.89, R2 = 0.9928), with a detection limit of 0.3218 nM. The results obtained for competitive substances, such as inorganic mercury ions and anions, show a high specificity of the method. In addition, this method successfully detected MeHg+ in seawater and marine products, with an accompanying spike recovery rate of 96.45-105.1%.

Optical Imaging Opportunities to Inspect the Nature of Cytosolic Iron Pools

The chemical nature of intracellular labile iron pools (LIPs) is described. By virtue of the kinetic lability of these pools, it is suggested that the isolation of such species by chromatography methods will not be possible, but rather mass spectrometric techniques should be adopted. Iron-sensitive fluorescent probes, which have been developed for the detection and quantification of LIP, are described, including those specifically designed to monitor cytosolic, mitochondrial, and lysosomal LIPs. The potential of near-infrared (NIR) probes for in vivo monitoring of LIP is discussed.

A Novel Triphenylamine-Based Flavonoid Fluorescent Probe with High Selectivity for Uranyl in Acid and High Water Systems

Developing a fluorescent probe for UO₂²⁺, which is resistant to interference from other ions such as Cu²⁺ and can be applied in acidic and high-water systems, has been a major challenge. In this study, a "turn-off" fluorescent probe for triamine-modified flavonoid derivatives, 2-triphenylamine-3-hydroxy-4H-chromen-4-one (abbreviated to HTPAF), was synthesized. In the solvent system of dimethyl sulfoxide:H₂O (abbreviated to DMSO:H₂O) (v/v = 5:95 pH = 4.5), the HTPAF solution was excited with 364 nm light and showed a strong fluorescence emission peak at 474 nm with a Stokes shift of 110 nm. After the addition of UO₂²⁺, the fluorescence at 474 nm was quenched. More importantly, there was no interference in the presence of metal ions (Pb²⁺, Cd²⁺, Cr³⁺, Fe³⁺, Co²⁺, Th⁴⁺, La³⁺, etc.), especially Cu²⁺ and Al³⁺. It is worth noting that the theoretical model for the binding of UO₂²⁺ to HTPAF was derived by more detailed density functional theory (DFT) calculations in this study, while the coordination mode was further verified using HRMS, FT-IR and ¹HNMR, demonstrating a coordination ratio of 1:2. In addition, the corresponding photo-induced electron transfer (PET) fluorescence quenching mechanism was also proposed.

Engineering BODIPY-based near-infrared nanoparticles with large Stokes shifts and aggregation-induced emission characteristics for organelle specific bioimaging

Lipid droplets (LDs) and lysosomes, as two important subcellular organelles, play specific and indispensable roles in various cellular processes. The development of efficient LD- and lysosome-specific fluorescent bio-probes is of great importance. However, current commercial lipid droplet- (LD) and lysosome-specific fluorescent specific bio-probes often suffer from the aggregation-caused quenching (ACQ) effect, short absorption and emission wavelengths, poor photostability and low specificity. Herein, a typical ACQ luminogen BODIPY was directly conjugated to strong electron donating triarylamine units at its α-positions, giving near-infrared (NIR) fluorescent materials TPAB and 2TPAB with aggregation-induced emission (AIE). Both TPAB and 2TPAB nanoparticles were obtained by self-assembly, and showed NIR emissions, large Stokes shifts, good photostability and two-photon absorption. These nanoparticles presented remarkable bioimaging performances and were shown to specifically localize in LDs or lysosomes, respectively, depending on the number of triarylamine units attached. They have been successfully used to detect endogenous LD overproduction, and monitor abnormal activities of LDs/lysosomes, as well as real-time track the lipophagy process in cells. Their far NIR emission and two-photon excitation further supported their promising bioimaging application for lipid droplet tracking in liver tissue and live zebrafish larvae. Our work here enriches BODIPY based NIR AIE dyes and provides organelle specific bio-probes which are superior to currently used commercial ones.

Reaction-based highly selective and sensitive monomer/polymer probes with Schiff base groups for the detection of Hg2+ and Fe3+ ions

It is urgent and important to detect heavy metals in environments. In this work, novel reaction-based fluorescent probes were obtained by Schiff base reaction. The probes with Schiff base moiety (-C=N-) undergo irreversible hydrolysis in the presence of Hg²⁺ and Fe³⁺. They exhibit perfect high selectivity and sensitivity to Hg²⁺and Fe³⁺ ions. Upon the addition of Hg²⁺and Fe³⁺, fluorescence intensity of the probes increased notably. And the color of the probe changes from brown to bright green under UV light, which can realize "naked eye" detection. In addition, Schiff base group was introduced into polyurethane chain through condensation polymerization reaction. As expected, the fluorescent polyurethane probe (P2) maintained the detection performance of its original small molecules (BSD). Even more P2 showed a more sensitive detection effect than BSD, and the detection limits of P2 for Hg²⁺ and Fe³⁺ reach 0.19 μM and 0.21 μM, respectively. It indicates that Reaction-based probes could be a useful tool for the detection of Hg²⁺ and Fe³⁺.

Recent Progress in Small-Molecule Fluorescent Probes for Detecting Mercury Ions

Mercury is a highly toxic and non-essential element that is found in every corner of the globe. The small amount of mercury produced by various pathways eventually enters freshwater and marine ecosystems, circulating through the food chain (especially fish) and causing various environmental problems in aspects including plants, animals, and human. There are several traditional quantitative methods developed for mercury ions (II) analysis in water samples. However, due to the complexity of the detection process, high cost and strong technical expertise, it is difficult to detect mercury ions in real-time. Therefore, in recent years, a large number of researchers have developed small-molecule fluorescent probes for Hg ions detection. Fluorimetry has the advantages of convenient detection, short response time, high sensitivity and good selectivity. This review summarized the small-molecule fluorescent probes for mercuric ion detection developed in recent years according to the chemical structural classification, compared their performances and elaborated the mechanism. We hope that the review will help the researches for the designs of metal ions fluorescent probes and their applications with certain reference value.

Imaging endogenous HClO in atherosclerosis using a novel fast-response fluorescence probe

A novel probe S-ClO was developed, which could selectively sense HClO as well as monitor HClO-induced arterial vessel inflammation.

Selective and reversible recognition of Hg2+ ions by Tetrathia[22]porphyrin(2.1.2.1)

Interestingly, neutral tetrathia[22]porphyrin(2.1.2.1) (TTP) acts as an efficient chemosensor for the detection of Hg²⁺ ions at ppb concentration. Consequent to binding the molecular plane of TTP bends and it has been supported by the DFT calculations. A rise in levelling off tail is observed in the electronic absorption spectrum in the presence of Hg²⁺ ions, which is suggestive of metal induced macrocyclic self-assembly and is further substantiated by the SEM, TEM and particle size measurement studies.

Unveiling the Photophysical Properties of Boron Heptaaryldipyrromethene Derivatives

Increased interest has been devoted to the discovery of multifunctional materials with desirable properties, as continuous performance enhancement of various devices mainly depends on high-performance materials. Now, density functional theory has become a powerful tool to design new materials and rationalize experimental observations. In this work, we explored the photophysical properties origin of chiral boron heptaaryldipyrromethene (heptaaryl-BODIPY), which has charming optoelectronic properties. At the same time, we designed the other five compounds on the basis of heptaaryl-BODIPY. The simulated electronic absorption and emission spectra of heptaaryl-BODIPY are in agreement with experimental ones, allowing us to reliably assign its electronic transition property. The designed compound 6 shows remarkably large first hyperpolarizability value up to 82.78×10^-30  esu. For this kind of compounds, their NLO response values associate with not only position but also electronic nature of substituent groups. Moreover, electron reorganization energies of compounds 1-4 are comparable to tris(8-hydroxyquinolinato)aluminium(III) which is a typical electron transport material. Intriguingly, the studied compounds are the excellent fluorescent probe materials from the standpoint of large Stokes shift and high emission efficiency. Our work enables an opportunity for understanding the relationship between microelectronic structure and macroscopic performance of BODIPY derivatives.

A BODIPY derivative for colorimetric fluorescence sensing of Hg2+, Pb2+ and Cu2+ ions and its application in logic gates

A BODIPY-based colorimetric and fluorescent chemosensor 1 anchored with dipyridylamino (DPA) receptor has been designed, synthesized and characterized. It exhibited a simultaneous sensitive recognition for Cu²⁺, Hg²⁺ and Pb²⁺ ions. With the addition of these three kinds of metal ions into 1 in CH₃CN, its initial absorption maximum displayed obvious blue shifts, and the color changes of the solution could be clearly observed by naked eyes. Besides, the fluorescence intensity was significantly enhanced accompanied with the appearance of new emission peaks at 587 nm for Pb²⁺ and Hg²⁺ ions and 545 nm for Cu²⁺ ions. These results were attributed to the π-deconjugation between N-pyridyl and the BODIPY group due to the binding of metal ions with the BODIPY and DPA groups. Based on the sensing behaviors of 1, three logic gates (OR, INHIBT and combinational logic gate) were constructed correspondingly.

Synthesis of a BODIPY disulfonate near-infrared fluorescence-enhanced probe with high selectivity to endogenous glutathione and two-photon fluorescent turn-on through thiol-induced SNAr substitution

A BODIPY disulfonate BODIPY-diONs with two-photon fluorescent turn-on effect was developed as fluorescence probe for selective detection of glutathione over cysteine and homocysteine. BODIPY-diONs is weakly fluorescent due to the 2,4-dinitrobenzenesulfonyl quencher group. When GSH was added, a S_NAr substitution reaction was triggered. The red emission of the BODIPY fluorophore at 675 nm was switched on, with a 27-fold emission enhancement in fluorescence intensity. The color of the solution changed from blue to green together with fluorescence appeared within 5 s. The absorbance and emission maxima of the probe BODIPY-diONs were achieved at 650 nm and 675 nm, respectively (quantum yield: 0.11). Interestingly, under the sapphire pulsed laser's 800 nm irradiation, in presence of GSH, the two-photon excited fluorescence (TPEF) of probe BODIPY-diONs was turned on, affording an OFF-ON response signal and a strong emission band at 682 nm. Furthermore, for detection of GSH, the chemodosimeter BODIPY-diONs exhibits high sensitivity and excellent anti-interference with low detection limit of 0.17 μM, and it works effectively within a wide pH range. Furthermore, the imaging studies proved that the probe BODIPY-diONs is suitable for the detection of GSH in complete physiological media.

A NIR facile, cell-compatible fluorescent sensor for glutathione based on Michael addition induced cascade spirolactam opening and its application in hepatocellular carcinoma

A NIR fluorescence probe with NIR emission wavelength at 746 nm and high quantum yield of 0.36 was designed and synthesized to selectively detect GSH over Hcy and Cys in living systems.

Bodipy-based chemosensors for highly sensitive and selective detection of Hg2+ ions

Small molecular chemo-sensors with strong fluorescence were designed and synthesized. Then, corresponding macromolecular sensors were synthesized by introducing the as-prepared small molecular sensors. The macromolecular chemo-sensors not only retained their sensing ability, but also enhanced the sensing ability dramatically.

A NIR rhodamine fluorescent chemodosimeter specific for glutathione: Knoevenagel condensation, detection of intracellular glutathione and living cell imaging

A new near-infrared probe for detecting glutathione based on conjugate addition and intramolecular amino induced spirolactam opening named RhAN was designed and synthesized. Its emission intensity enhance more than 90-fold upon addition of GSH. In addition, it also has high sensitivity with low detection limit of 0.1 μM.

A novel pyridyl triphenylamine-BODIPY aldoxime: Naked-eye visible and fluorometric chemodosimeter for hypochlorite

An aldoxime containing fluorescent probe based on vinylpydine-appended triphenylamine-BODIPY has been designed and used for hypochlorite detection. OX-PPA-BODIPY was developed by introducing an aldoxime group into the 2-position of BODIPY, which can be used for the detection of hypochlorite with a sharp color change from pink to green. The attachment of 4-vinylpyridine moiety to triphenylamine-BODIPY constructs a fluorogen with desirable conjugated system. The probe, which displays extremely weak fluorescence owing to the CN isomerization mechanism at 2-position of BODIPY, responds to HClO/ClO^- through a dramatic enhancement of its fluorescence intensity. This new probe, a naked-eye visible and fluorometric chemodosimeter, exhibits high selectivity and sensitivity toward hypochlorite over other reactive oxygen species (ROS) and anions. The detection is accompanied by a 20-fold increase in fluorescent intensity (Φ_F from 0.02 to 0.43). The detection limit of the probe for hypochlorite is 7.37×10^-7M. Moreover, OX-PPA-BODIPY can be used to detect hypochlorite in real water samples.

Synthetically simple, click-generated quinoline-based Fe3+ sensors

Simple quinoline-based fluorescent probes for Fe³⁺ have been efficiently synthesized through 'click' reaction. Both probes gave intense fluorescence compared to 8-hydroquinoline in various organic solvents due to the inhibition of the excited state intramolecular photon transfer process, while showing dramatically quenched and red-shifted fluorescence in an aqueous solution, which can be attributed to the hydrogen bond-induced intermolecular excited state proton transfer process. In the presence of Fe³⁺ or in an acidic condition (pH less than 4.0), both probes showed similar quenching of the emission and over 100 nm red-shifts of their emission maxima. The binding mode between the probes and Fe³⁺ has been found to be 1:1 based on Job's plot. A highly sensitive and selective response in their absorption and emission towards Fe³⁺ over many other metal ions, including Cr³⁺ and Cu²⁺, was observed and may be the result of the ground state metal to ligand charge transfer effect from Fe³⁺ to quinoline ligands.

A novel (3,6-di-tert-butylcarbazol-9-yl) triphenylamine–BODIPY–tricyanofuran conjugated dye: synthesis and rapid naked-eye detection of hypochlorite

A colorimetric and ratiometric probe, BCPA–BODIPY–TCF, for hypochlorite (ClO⁻) based on a D–π–A structure was synthesized through the Knoevenagel reaction.

A smart two-photon fluorescent platform based on desulfurization–cyclization: a phthalimide–rhodamine chemodosimeter for Hg2+ NIR emission at 746 nm and through-bond energy transfer

In this work, a smart two-photon fluorescent platform based on desulfurization–cyclization was developed, in the construction of TBET-based fluorescent chemodosimeter CyRSN towards Hg²⁺ in near-infrared region at 746 nm.

Near-infrared BODIPY-based two-photon ClO− probe based on thiosemicarbazide desulfurization reaction: naked-eye detection and mitochondrial imaging

Near-infrared two-photon ClO⁻ fluorescent probe based on the desulfurization reaction of the thiosemicarbazide group.