Synthesis and evaluation of fluorescent resins with europium-β-diketonate complex for orthodontic use

No effective technique exists for removing adhesive remnants following bracket debonding. We propose that fluorescence imaging using europium ions (Eu3+) offers an effective solution for minimizing iatrogenic enamel damage. This study aimed to assess the impact of different mixing ratios of monomer mixtures on the photoluminescence and flexural properties of a newly developed fluorescent adhesive. Four monomer blends with varying urethane dimethacrylate (UDMA) to triethylene glycol dimethacrylate (TEGDMA) ratios were prepared and polymerized. The blends contained 0.1 wt% of tris(1,3-diphenyl-1,3-propanedionato)(1,10-phenanthroline) Eu(III), [Eu(DBM)3Phen], as the phosphor. Optical measurements and flexural tests were conducted for each resin specimen. The emission spectra exhibited narrow bands corresponding to the 4f-4f transitions of the Eu3+ ions. The photoluminescence properties remained unaffected by the mixing ratio, whereas the mechanical properties tended to improve with higher UDMA content. We conclude that the Eu(DBM)3Phen-containing resin shows promise as a fluorescent orthodontic adhesive that contributes to preserving enamel health.

Novel Formulations Containing Fluorescent Sensors to Improve the Resolution of 3D Prints

Three-dimensional printing in SLA (stereolithography) and DLP (digital light processing) technologies has recently been experiencing a period of extremely rapid development. This is due to the fact that researchers recognise the many advantages of 3D printing, such as the high resolution and speed of the modelling and printing processes. However, there is still a search for new resin formulations dedicated to specific 3D printers allowing for high-resolution prints. Therefore, in the following paper, the effects of dyes such as BODIPY, europium complex, and Coumarin 1 added to light-cured compositions polymerised according to the radical mechanism on the photopolymerisation process speed, polymerisation shrinkage, and the final properties of the printouts were investigated. The kinetics of the photopolymerisation of light-cured materials using real-time FT-IR methods, as well as printouts that tangibly demonstrate the potential application of 3D printing technology in Industry 4.0, were examined. These studies showed that the addition of dyes has an effect on obtaining fluorescent prints with good resolution.

Lysosome-targeting luminescent lanthanide complexes: From molecular design to bioimaging

Lysosomes are essential acidic cytoplasmic membrane-bound organelles in human cells that play a critical role in many cellular events. A comprehensive understanding of lysosome-specific imaging can ultimately help us to...

Luminescent lanthanide(III) complexes of DTPA-bis(amido-phenyl-terpyridine) for bioimaging and phototherapeutic applications

We report here a series of coordinatively-saturated and thermodynamically stable luminescent [Ln(dtntp)(H₂O)] [Ln(III) = Eu (1), Tb (2), Gd (3), Sm (4) and Dy (5)] complexes using an aminophenyl-terpyridine appended-DTPA (dtntp) chelating ligand as cell imaging and photocytotoxic agents. The N,N″-bisamide derivative of H₅DTPA named as dtntp is based on 4'-(4-aminophenyl)-2,2':6',2″-terpyridine conjugated to diethylenetriamine-N,N',N″-pentaacetic acid. The structure, physicochemical properties, detailed photophysical aspects, interaction with DNA and serum proteins, and photocytotoxicity were studied. The intrinsic luminescence of Eu(III) and Tb(III) complexes due to f → f transitions used to evaluate their cellular uptake and distribution in cancer cells. The solid-state structure of [Eu(dtntp)(DMF)] (1·DMF) shows a discrete mononuclear molecule with nine-coordinated {EuN₃O₆} distorted tricapped-trigonal prism (TTP) coordination geometry around the Eu(III). The {EuN₃O₆} core results from three nitrogen atoms and three carboxylate oxygen atoms, and two carbonyl oxygen atoms of the amide groups of dtntp ligand. The ninth coordination site is occupied by an oxygen atom of DMF as a solvent from crystallization. The designed probes have two aromatic pendant phenyl-terpyridine (Ph-tpy) moieties as photo-sensitizing antennae to impart the desirable optical properties for cellular imaging and photocytotoxicity. The photostability, coordinative saturation, and energetically rightly poised triplet states of dtntp ligand allow the efficient energy transfer (ET) from Ph-tpy to the emissive excited states of the Eu(III)/Tb(III), makes them luminescent cellular imaging probes. The Ln(III) complexes show significant binding tendency to DNA (K ~ 10⁴ M^-1), and serum proteins (BSA and HSA) (K ~ 10⁵ M^-1). The luminescent Eu(III) (1) and Tb(III) (2) complexes were utilized for cellular internalization and cytotoxicity studies due to their optimal photophysical properties. The cellular uptake studies using fluorescence imaging displayed intracellular (cytosolic and nuclear) localization in cancer cells. The complexes 1 and 2 displayed significant photocytotoxicity in HeLa cells. These results offer a modular design strategy with further scope to utilize appended N,N,N-donor tpy moiety for developing light-responsive luminescent Ln(III) bioprobes for theranostic applications.

Synthesis of water-soluble europium-containing nanoprobes via polymerization-induced self-assembly and their cellular imaging applications

Lanthanide nanoprobes have attracted extensive attention for applications in cellular imaging and biological sensing. Herein, water-dispersible europium (III)-based (Eu(III)-based) nanoprobes were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of hydrophobic monomers (Eu(III)-containing monomer and methyl methacrylate (MMA)) using hydrophilic macro-chain transfer agent poly(PEGMA)-CTA. The resulted poly(PMEu) nanoprobes showed spherical in shape in good monodispersity with average diameters of around 210 nm. The poly(PMEu) nanoprobles excellent aqueous dispersity, high aqueous stability and good luminescence properties with quantum yields of 37.21% and fluorescence lifetime of 312.4 μs. Moreover, the poly(PMEu) nanoprobes exhibited good cellular biocompatibility with cell viabilities of 88.2% and high fluorescence intensity for in vitro cellular imaging. The present approach provides a facile strategy for fabrication of luminescent Eu(III)-based nanoprobes with great potential applications for biological imaging.

Green facile synthesis to develop nanoscale coordination polymers as lysosome-targetable luminescent bioprobes

Three new coordination polymers (CPs), namely [{M(HL)(L)(H2O)}(ClO4)(H2O)]∞ (M = Zn for CP 1, Mn for CP 2, Cu for CP 3) were synthesized to explore their efficacy as lysosome-targetable luminescent bioprobes. The synthesized CPs were characterized by techniques including single-crystal X-ray analysis, FTIR spectroscopy and elemental analysis. Single-crystal analysis revealed the formation of iso-structural CPs displaying distorted adamantoid topology developed by bridging ligands and H-bonds connections and metals at the nodes. A green hand-grinding technique with a mortar and pestle resulted in nanoscale coordination polymers (NCPs) suitable for cell permeability and was further confirmed by SEM and DLS analyses. Two of these hand-ground nanoscale coordination polymers NCP 1 and NCP 2 showed excellent green luminescence and were explored as potential and selective long-time biotrackers towards lysosome using the human lung carcinoma cell line (A549). Strikingly, the developed bioprobe displayed excellent bio-availability, photostability and excellent selectivity towards lysosomes sustained by various in vitro cell imaging experiments. Moreover, the long-term probing ability of these NCPs turned out to be better than the commercially available lysosome tracker i.e. LysoTracker Red, indicating their potential real-life application in bio-imaging. To the best ofour knowledge, this is the first example of nonexpensive and less toxic essential transition metal-based nanoscale coordination polymers that can behave as effective lysosome-targetable luminescent bioprobes.

A visible-light-excitable mitochondria-targeted europium complex probe for hypochlorous acid and its application to time-gated luminescence bioimaging

Development of fluorescent/luminescent probes for rapid, selective and sensitive detection of reactive oxygen species (ROS) is of great significance for understanding the roles of ROS in pathophysiological processes. In the present research, a visible-light-excitable Eu³⁺ complex-based probe, Eu(L)₃(DPBT), is designed and synthesized for the time-gated luminescence (TGL) determination of hypochlorous acid (HClO) in vitro and in vivo. The proposed probe exhibits a rapid, selective and sensitive TGL response to HClO, and excellent localization of mitochondria in living cells with low cytotoxicity. These features allow the probe to be used for the TGL sensing and imaging of HClO formation in mimic inflammatory cells at a subcellular level, as well as in endotoxin-induced liver injury and rheumatoid arthritis in live mice. In addition, by immobilizing the probe in the PEG hydrogel, the smart sensor films with rapid response to HClO were prepared, and successfully used for the real-time monitoring of HClO generation in mouse wounds, in order to distinguish the infected wounds from acute ones. Overall, this study provides a useful tool for the clinical monitoring and treatment of wound diseases.

Recent Advances in Luminescence Imaging of Biological Systems Using Lanthanide(III) Luminescent Complexes

The use of luminescence in biological systems allows one to diagnose diseases and understand cellular processes. Molecular systems, particularly lanthanide(III) complexes, have emerged as an attractive system for application in cellular luminescence imaging due to their long emission lifetimes, high brightness, possibility of controlling the spectroscopic properties at the molecular level, and tailoring of the ligand structure that adds sensing and therapeutic capabilities. This review aims to provide a background in luminescence imaging and lanthanide spectroscopy and discuss selected examples from the recent literature on lanthanide(III) luminescent complexes in cellular luminescence imaging, published in the period 2016-2020. Finally, the challenges and future directions that are pointing for the development of compounds that are capable of executing multiple functions and the use of light in regions where tissues and cells have low absorption will be discussed.

A luminescent pH-sensitive lysosome targeting Eu(iii) probe

A pH-responsive, water soluble luminescent Eu(iii) probe is designed to target lysosomes via intrinsic f–f emission from the Eu(iii) centre.

Surface-Engineered Design of Efficient Luminescent Europium(III) Complex-Based Hydroxyapatite Nanocrystals for Rapid HeLa Cancer Cell Imaging

We synthesized hydroxyapatite nanocrystals under the existence of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (EuTH) complex to form inorganic/organic hybrid nanocrystal (EHA). Then, the folic acid derivative (folate N-hydroxysuccinimidyl ester (FA-NHS)) as the targeting ligand for the HeLa cancer cells was immobilized on the EHA by the mediation of both 3-aminopropyltriethoxysilane and methyltriethoxysilane molecules. Here, we investigated the photofunctions based on the interfacial interactions between the FA-NHS and EHA nanohybrids for preparing the novel bioimaging nanomaterials. As a result, the photofunctions could be changed by the FA-NHS molecular occupancy on the EHA. When the molecular occupancy ratio to the EHA surfaces is at around 3-5%, the intense luminescence from the f-f transition of the Eu³⁺ ions as well as the charge transfer between the EuTH-FA-NHS was observed to exhibit higher quantum efficiency. Moreover, effective dispersibility in phosphate-buffered saline was confirmed with immobilizing the positively charged FA-NHS. The cytotoxicity against the HeLa cells was also evaluated to verify whether the nanohybrids can be the candidate for cell imaging. The affinity and noncytotoxicity between the FA-NHS-immobilized EHA nanohybrids and cells were monitored for 3 days. Red luminescence from the cells could be observed, and the labels with following the cellular shapes were achieved by an additional culture time of 1 h after injecting the FA-NHS-immobilized EHA nanohybrids to the spheres, indicating the rapid bioimaging process. Therefore, this is the first successful report to describe the synthesis of inorganic-organic nanohybrid systems for controlling the EuTH-FA-NHS interactions. The photofunction of the interfacial interactions was successfully designed to provide "efficient luminescent ability" as well as "rapid targeting to the cancer cells" in one particle.

Luminescent europium(iii) and terbium(iii) complexes of β-diketonate and substituted terpyridine ligands: synthesis, crystal structures and elucidation of energy transfer pathways

A series of coordinatively saturated Ln^III complexes: [Ln(R-TPY)(TTA)₃] (1–6) were designed and structurally characterized and plausible energy transfer (ET) pathways determined using a theoretical method.

Europium Complexes: Luminescence Boost by a Single Efficient Antenna Ligand

We advance the concept that a single efficient antenna ligand substituted in or added to an otherwise weakly luminescent europium complex is enough to significantly boost its luminescence. Our results, on the basis of photophysical measurements on 5 novel europium complexes and 15 known ones, point in the direction that ligand dissimilarity and ligand diversity are all concepts that clearly play a fundamental role in the luminescence of europium complexes. We show that it is important that a symmetry breaker ligand exists in the complex to enhance ligand dissimilarity and ligand diversity, all mainly affecting the nonradiative decay rate by reducing it. Because the presence of at least one antenna ligand is also obviously necessary, the optimal and the most cost-effective situation can be achieved by adding a single coordination symmetry breaker that is also an efficient antenna, such as 1-(2-thenoyl)-3,3,3-trifluoroacetone or 4,4,4-trifluoro-1-phenyl-1,3-butanedione. In such cases the quantum efficiency, η, is decidedly boosted, as can be verified by going from complex [EuCl₂(TPPO)₄]Cl·3H₂O with η = 0% to the novel complex [EuCl₂(BTFA)(TPPO)₃], where TPPO stands for triphenylphosphine oxide, with η = 62%.