Watching lanthanide nanoparticles one at a time: characterization of their photoluminescence dynamics at the single nanoparticle level.

Lanthanide nanoparticles (LnNPs) feature sharp emission lines together with millisecond emission lifetimes which make them promising luminescent probes for biosensing and bioimaging. Although LnNPs are attracting much interest, their photoluminescence properties at the single nanoparticle level remain largely unexplored. Here, we employ fluorescence correlation spectroscopy (FCS) and photoluminescence burst analysis to investigate the photodynamics of Sm- and Eu-based LnNPs with single nanoparticle sensitivity and microsecond resolution.

Upconversion Luminescence with Bis-pyclen Yb(III) Chelates: Crown vs. Linear Polyether Linkers in Discrete Heteropolynuclear Architectures.

Ligands combining two lateral bis-pyridyl-phosphonated-pyclens were synthesized, using a flexible linear pegylated linker (L2) or a bulkier K22 crown-ether (L3). A functionalized pyridyl-phosphonated-pyclen (L1) was also prepared as a mononuclear analogue. Coordination behavior of lanthanide cations was studied via NMR titration with Lu for L1, and UV/Vis and luminescence spectroscopy with Yb for L2/L3.

Unearthing the Real-Time Excited State Dynamics from Antenna to Rare Earth Ions Using Ultrafast Transient Absorption.

The conventional energy transfer pathway in organic lanthanide complexes is purported to be from the excited singlet state of the chromophore to the triplet state and subsequently directly to the emitting state of the trivalent lanthanide ion. In this work, we found that the energy transfer occurs from the triplet state to the nearest energy level, instead of directly to the emitting state of the lanthanide ion. The triplet decay rate for different lanthanide ions follows an energy gap law from the triplet level to the receiving level of the lanthanide ion.

Structure-Activity Optimization of Luminescent Tb-doped LaF Nanoparticles.

A series of Tb-doped LaF nanoparticles (NPs) was prepared by systematically varying the Tb doping rate from 0 to 100%. The elemental composition was confirmed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis, and the size, morphology, and crystal structure were determined in the solid state by transmission electron microscopy and X-ray diffractometry, while the size and ζ-potential of the NPs in solution were studied by dynamic light scattering, Taylor dispersion analysis, and laser Doppler electrophoresis. While the crystal structure appears to be hexagonal for a doping rate of up to 70%, an admixture of hexagonal and orthorhombic phases is observed for 80 and 90% Tb contents with a pure orthorhombic phase being obtained for TbF.

Upconverting photons at the molecular scale with lanthanide complexes.

In this perspective, we summarise the major milestones to date in the field of molecular upconversion (UC) with lanthanide based coordination complexes. This begins from the leap firstly from solid-state to nanoparticular regimes, and further down the scale to the molecular domain. We explain the mechanistic intricacies of each differing way of generating upconverted photons, critiquing them and outlining our views on the benefits and limitations of each process, also offering our perspective and opinion on where these new molecular UC edifices will take us.

Exploitation of Luminescent Lanthanide Nanoparticles for a Sensitivity-Enhanced ELISA Detection Method.

A new detection method based on the photoluminescence properties of dye-sensitized lanthanide nanoparticles (Ln NPs) was developed for enzyme-linked immunosorbent assays (ELISAs). In this method, the horseradish peroxidase (HRP) enzyme catalyzes the oxidation of phenol derivatives in the presence of hydrogen peroxide, providing dimers that are able to interact with the Ln NP surface and to efficiently photosensitize the Ln ions. Due to the very long emission lifetime of Ln, the time-gated detection of Ln NP luminescence allows the elimination of background noise due to the biological environment.

Subcutaneous Administration of a Zwitterionic Chitosan-Based Hydrogel for Controlled Spatiotemporal Release of Monoclonal Antibodies.

Subcutaneous (SC) administration of monoclonal antibodies (mAbs) is a proven strategy for improving therapeutic outcomes and patient compliance. The current FDA-/EMA-approved enzymatic approach, utilizing recombinant human hyaluronidase (rHuPH20) to enhance mAbs SC delivery, involves degrading the extracellular matrix's hyaluronate to increase tissue permeability. However, this method lacks tunable release properties, requiring individual optimization for each mAb.

Synthesis and Photophysical Properties of Lanthanide Pyridinylphosphonic Tacn and Pyclen Derivatives: From Mononuclear Complexes to Supramolecular Heteronuclear Assemblies.

Synthetic methodologies were developed to achieve the preparation of ligands and consisting of tacn- and pyclen-based chelators decorated with pyridinylphosphonic pendant arms combined with ethylpicolinamide or acetate coordinating functions, respectively. Phosphonate functions have been selected for their high affinity toward Ln ions compared to their carboxylated counterparts and for their steric hindrance that favors the formation of less-hydrated complexes. Thanks to regiospecific -functionalization of the macrocyclic backbones, the two ligands were isolated with good yields and implicated in a comprehensive photophysical study for the complexation of Eu, Tb, and Yb.

Effect of Magnetic Anisotropy on the H NMR Paramagnetic Shifts and Relaxation Rates of Small Dysprosium(III) Complexes.

We present a detailed analysis of the H NMR chemical shifts and transverse relaxation rates of three small Dy(III) complexes having different symmetries (, or ). The complexes show sizeable emission in the visible region due to F → H transitions ( = 15/2 to 11/2). Additionally, NIR emission is observed at ca.

Structural Variations in Carboxylated Bispidine Ligands: Influence of Positional Isomerism and Rigidity on the Conformation, Stability, Inertness and Relaxivity of their Mn Complexes.

Mn complexes of 2,4-pyridyl-disubstituted bispidine ligands have emerged as more biocompatible alternatives to Gd -based MRI probes. They display relaxivities comparable to that of commercial contrast agents and high kinetic inertness, unprecedented for Mn complexes. The chemical structure, in particular the substituents on the two macrocyclic nitrogens N3 and N7, are decisive for the conformation of the Mn complexes, and this will in turn determine their thermodynamic, kinetic and relaxation properties.

Bioconjugation studies of an EGF-R targeting ligand on dendronized iron oxide nanoparticles to target head and neck cancer cells.

A major challenge in nanomedicine is designing nanoplatforms (NPFs) to selectively target abnormal cells to ensure early diagnosis and targeted therapy. Among developed NPFs, iron oxide nanoparticles (IONPs) are good MRI contrast agents and can be used for therapy by hyperthermia and as radio-sensitizing agents. Active targeting is a promising method for selective IONPs accumulation in cancer tissues and is generally performed by using targeting ligands (TL).

Intracellular accumulation and immunological response of NIR-II polymeric nanoparticles.

Polymeric nanoparticles (NPs) are extremely promising for theranostic applications. However, their interest depends largely on their interactions with immune system, including the capacity to activate inflammation after their capture by macrophages. In the present study, we generated monodisperse poly(ethyl methacrylate) (PEMA) NPs loaded with hydrophobic photoluminescent gold nanoclusters (Au NCs) emitting in the NIR-II optical windows and studied their interaction in vitro with J774.

Dye-sensitized lanthanide containing nanoparticles for luminescence based applications.

Due to their exceptional luminescent properties, lanthanide (Ln) complexes represent a unique palette of probes in the spectroscopic toolkit. Their extremely weak brightness due to forbidden Ln electronic transitions can be overcome by indirect dye-sensitization from the antenna effect brought by organic ligands. Despite the improvement brought by the antenna effect, (bio)analytical applications with discrete Ln complexes as luminescent markers still suffers from low sensitivity as they are limited by the complex brightness.

Mn Complexes with a Bispidine-Phosphonate Ligand: High Kinetic Inertness for Imaging Applications.

Bispidine (3,7-diazabicyclo[3.3.1]nonane) provides a rigid and preorganized scaffold that is particularly interesting for the stable and inert complexation of metal ions, especially for their application in medical imaging.

Upconversion in a d-f [RuYb] Supramolecular Assembly.

We have prepared a hetero-tetrametallic assembly consisting of three ytterbium ions coordinated to a central [Ru(bpm)] (bpm = 2,2'-bipyrimidine) motif. Irradiation into the absorption band of the peripheral ytterbium ions at 980 nm engenders emission of the MLCT state of the central [Ru(bpm)] core at 636 nm, which represents the first example of f → d molecular upconversion (UC). Time-resolved measurements reveal a slow rise of the UC emission, which was modeled with a mathematical treatment of the observed kinetics according to a cooperative photosensitization mechanism using a virtual Yb centered doubly excited state followed by energy transfer to the Ru centered MLCT state.

Optimal Physicochemical Properties of Antibody-Nanoparticle Conjugates for Improved Tumor Targeting.

Tumor-targeted antibody (mAb)/fragment-conjugated nanoparticles (NPs) represent an innovative strategy for improving the local delivery of small molecules. However, the physicochemical properties of full mAb-NPs and fragment-NPs-that is, NP material, size, charge, as well as the targeting antibody moiety, and the linker conjugation strategies-remain to be optimized to achieve an efficient tumor targeting. A meta-analysis of 161 peer-reviewed studies is presented, which describes the use of tumor-targeted mAb-NPs and fragment-NPs from 2009 to 2021.

Evaluation of a Lateral Flow Immunoassay COVIDTECH SARS-CoV-2 IgM/IgG Antibody Rapid Test.

The new coronavirus severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for severe respiratory illness (i.e., COVID-19).

Cooperative Luminescence and Cooperative Sensitisation Upconversion of Lanthanide Complexes in Solution.

Upconversion materials have led to various breakthrough applications in solar energy conversion, imaging, and biomedicine. One key impediment is the facilitation of such processes at the molecular scale in solution where quenching effects are much more pronounced. In this work, molecular solution-state cooperative luminescence (CL) upconversion arising from a Yb excited state is explored and the mechanistic origin behind cooperative sensitisation (CS) upconversion in Yb/Tb systems is investigated.

From Mono- to Polynuclear Coordination Complexes with a 2,2'-Bipyrimidine-4,4'-dicarboxylate Ligand.

The coordination properties of the ligand 2,2'-bipyrimidine-4,4'-dicarboxylic acid (H) with lanthanide(III) ions (Ln = Eu, Tb, or Lu) were investigated. The syntheses of the H ligand and its salts, [K()(HO)] () and [(NH)Lu()] ( = Et, Hex, or en), are described. In the presence of LnCl salts (Ln = Lu, Eu, or Tb), the formation of [Ln()] and [Ln()(HO)] species was assessed by H nuclear magnetic resonance (NMR), spectrophotometry, and spectrofluorometric titrations in aqueous solution.

Optical spin-state polarization in a binuclear europium complex towards molecule-based coherent light-spin interfaces.

The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ion (REI)-based molecular systems, whose quantum properties could be tuned taking advantage of molecular engineering strategies, are one of the systems actively pursued for the implementation of QIP schemes. Herein, we demonstrate the efficient polarization of ground-state nuclear spins-a fundamental requirement for all-optical spin initialization and addressing-in a binuclear Eu(III) complex, featuring inhomogeneously broadened D →F optical transition.

Structural and Thermodynamics Studies on Polyaminophosphonate Ligands for Uranyl Decorporation.

The development of actinide decorporation agents with high complexation affinity, high tissue specificity, and low biological toxicity is of vital importance for the sustained and healthy development of nuclear energy. After accidental actinide intake, sequestration by chelation therapy to reduce acute damage is considered as the most effective method. In this work, a series of bis- and tetra-phosphonated pyridine ligands have been designed, synthesized, and characterized for uranyl (UO) decorporation.

Cyclam-Based Chelators Bearing Phosphonated Pyridine Pendants for Cu-PET Imaging: Synthesis, Physicochemical Studies, Radiolabeling, and Bioimaging.

Herein we present the preparation of two novel cyclam-based macrocycles ( and ), bearing phosphonate-appended pyridine side arms for the coordination of copper(II) ions in the context of Cu PET imaging. The two ligands have been prepared through conventional protection-alkylation sequences on cyclam, and their coordination properties have been thoroughly investigated. The corresponding copper complexes have been fully characterized in the solid state (X-ray diffraction analysis) and in solution (EPR and UV-vis spectroscopies).

Upconversion in molecular hetero-nonanuclear lanthanide complexes in solution.

Here we show that nonanuclear lanthanide complexes respresent a new class of solution state upconversion (UC) molecules. For a composition of one Tb per eight Yb the nonanuclear complexes display a very efficient UC phenomenon with Tb luminescence in the visible region upon 980 nm NIR excitation of Yb. An unprecedented value of 1.