Ga-Lai Law

Octadentate Cages of Tb(III) 2-Hydroxyisophthalamides: A New Standard for Luminescent Lanthanide Labels

The synthesis, structure, and photophysical properties of several Tb(III) complexes with octadentate, macrotricyclic ligands that feature a bicapped topology and 2-hydroxyisophthalamide (IAM) chelating units are reported. These Tb(III) complexes exhibit highly efficient emission (Φ(total) ≥ 50%), large extinction coefficients (ε(max) ≥ 20,000 M(-1) cm(-1)), and long luminescence lifetimes (τ(H(2)O) ≥ 2.45 ms) at dilute concentrations in standard biological buffers. The structure of the methyl-protected ligand was determined by single-crystal X-ray diffraction and confirms the macrotricyclic structure of the parent ligand; the amide groups of the methyl-protected cage compound generate an anion binding cavity that complexes a chloride anion. Once the ligand is deprotected, a conformational change generates a similar cavity, formed by the phenolate and ortho amide oxygen groups that strongly bind lanthanide ions. The Tb(III) complexes thus formed display long-term stability, with little if any change in their spectral properties (including lifetime, quantum yield, and emission spectrum) over time or in different chemical environments. Procedures to prepare functionalized derivatives with terminal amine, carboxylate, and N-hydroxysuccinimide groups suitable for derivatization and protein bioconjugation have also been developed. These bifunctional ligands have been covalently attached to a number of different proteins, and the terbium complexes exceptional photophysical properties are retained. These compounds establish a new aqueous stability and quantum yield standard for long-lifetime lanthanide reporters.

Emissive Terbium Probe for Multiphoton in Vitro Cell Imaging

A polymeric terbium complex that can be excited by near-infrared excitation at 800 nm via multiphoton absorption processes has been synthesized. This complex has been demonstrated to show strong, observable, three-photon-induced f-f emission in cell imaging. In vitro studies carried out in three carcinoma cell lines (A549, HONE1, and HeLa) have been performed and shown to have low cytotoxicity. This complex is therefore a potential candidate for future infrared excitation imaging dyes.

White OLED with a single-component europium complex.

A new direction for white organic light-emitting devices is shown, fabricated from a novel europium complex; this single component contains a double emission center of bluish-green and red, combined to a give a pure white emission (CIE x = 0.34 and y = 0.35).

A single sensitizer for the excitation of visible and NIR lanthanide emitters in water with high quantum yields.

The versatile octadentate TIAM ligand forms lanthanide (Sm, Eu, Tb, Dy, Ho) complexes with high quantum yields in water. This ligand is an efficient sensitizer, and also shields the metal center from solvent quenching, as shown by an X-ray diffraction study of the Ho complex.

Functionalized europium nanorods for in vitro imaging.

Emissive europium hydroxide nanorods (ENR) (20 nm x 500 nm) functionalized by a surface coating of chromophore-containing organically modified silicate (ORMOSIL) layer, have been synthesized and characterized by high-resolution transmission electron microscopy (TEM). Low-temperature photophysical characterization of the functionalized nanorods (FENR) demonstrated a strong red 5D0 luminescence both in solid and in suspended solutions. Potentials of this nanorod material for live cell imaging have also been explored. Both the bare and functionalized nanorods are able to enter living human cells with no discernible cytotoxicity. Chromophore-to-Eu3+ energy-transfer in the functionalized nanorods enables staining of the cytoplasm of living human cells. This is confirmed by costaining with fluorescent dextran. The red chromophore-sensitized luminescence from the internalized nanorods in live human lung carcinoma cells (A549) can be observed by confocal microscopy 2 h after loading and reaches maximal emission after 24 h.

Bifunctional up-converting lanthanide nanoparticles for selective in vitro imaging and inhibition of cyclin D as anti-cancer agents

Inhibition of the CDK4/cyclin D complex through the substrate recruitment site on the cyclin positive regulatory subunit is recognised as being a promising anti-cancer target. Specific peptide sequences can be used to selectively disrupt this target, but the development of peptides as anti-tumor agents in vitro/in vivo presents several obstacles. Poor cell internalization, low sensitivity towards enzymatic degradation in vivo, and ineffectiveness in monitoring via indirect screening are all issues which must be overcome. Herein, we describe the surface functionalization of lanthanide nanoparticles with cyclin D-specific peptides to prepare novel nanomaterials (UCNPs-P1) which can target the CDK4/cyclin D complex. The nanomaterials prepared (UCNPs-P1) are cell permeable and they display parallel emission spectra in vitro and in an aqueous biological environment. They can also be used in low dose concentrations under harmless NIR excitation and emission via upconversion. Uniquely, in addition to acting as a bioimaging probe, UCNPs-P1 also exhibits promising cytotoxicity towards cancer cells. In light of the aforementioned properties, the prepared functionalized nanomaterials (UCNPs-P1) offer the first real dual acting system for cyclin D imaging and simultaneous inhibition of cancer cell division.

Impressive Europium Red Emission Induced by Two-Photon Excitation for Biological Applications

Three triazine-based europium(III) complexes were synthesized that demonstrated strong two-photon induced europium emission with a high two-photon absorption cross-section. The modified triazine ligand of complex 3 initiated over 100% enhancement of the two-photon absorption cross-section (σ(2): 320 GM) when compared with complex 1 (σ(2): 128 GM) in a solution of DMSO. Europium complex 3 is also stable in vitro, and power-dependence curves were obtained in vitro to confirm the two-photon-induced f-f emission in HeLa cells.

Nonlinear optical activity in dipolar organic–lanthanide complexes

A series of fifteen dipolar polymeric lanthanide complexes of trans-cinnamic acid, [Ln(C9H7O2)3]n, which crystallize in the non-centrosymmetric space groups R3c and P21, have been synthesized and the crystal structures of 14 of these have been determined. From the crystallographic data, two different coordination scenarios for these complexes have been found: Type I, CN = 9, Ln = La, Ce, Nd, Sm, Eu, Gd and Tb, and Type II, CN = 7, Ln = Y, Dy, Ho, Er, Tm, Yb and Lu. The linear and nonlinear photophysical properties of these complexes have been studied using various laser excitation wavelengths. The low temperature photoluminescence spectrum shows a distortion from the C3 site symmetry of the Eu3+ complex. Strong second harmonic generation (SHG) has been observed for both Types I and II in the solid state. The normalized SHG intensities of the members of the entire series of lanthanide complexes have been compared and the solution state hyperpolarizabilities have also been measured for the study of the effects of 4f-electrons on nonlinear photophysical properties. These SHG parameters show maximum values near the center of the lanthanide series, as opposed to previously reported fairly linear or independent variations.

Evidence for the optical signalling of changes in bicarbonate concentration within the mitochondrial region of living cells

Image and spectral intensity from bicarbonate-selective europium(III) probes localised in the mitochondria of cells is modulated reversibly by variation of external pCO(2), and is suppressed by addition of the carbonic anhydrase inhibitor, acetazolomide.

Synthesis, Crystal Structures, and Luminescence of Organic-Lanthanide Complexes with Nicotinate and Isonicotinate Ligands

Six lanthanide coordination compounds with two isomeric carboxylic acids, nicotinic acid (HL(1)) and isonicotinic acid (HL(2)), [(L(1))3Ln(H2O)2]2 (Ln = Eu, 1; Gd, 2; Tb, 3) and [( L(2))2Ln(H2O)4][NO3] (Ln = Eu, 4; Gd, 5; Tb, 6), have been synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1-3 are dimeric whereas 4-6 are polymeric, all with 8-coordination of Ln(3+). The distinction between these lanthanide complexes is readily accomplished from the 10 K high resolution electronic emission spectra. Spectral interpretation is given for the Eu(3+) complexes 1, 4, whereas the spectra of 3 and 6 are more complex. The relationships between spectroscopic and crystallographic site symmetries are discussed. The calculated second rank crystal field strengths of Eu(3+) in 1 and 4 are intermediate in magnitude.