Lanthanide Chelates Research Articles

Recent advances in photoluminescence detection of fingerprints.

Photoluminescence detection of latent fingerprints has over the last quarter century brought about a new level of fingerprint detection sensitivity. The current state of the art is briefly reviewed to set the stage for upcoming new fingerprint processing strategies. These are designed for suppression of background fluorescence from articles holding latent prints, an often serious problem. The suppression of the background involves time-resolved imaging, which is dealt with from the perspective of instrumentation as well as the design of fingerprint treatment strategies. These focus on lanthanide chelates, nanocrystals, and nanocomposites functionalized to label fingerprints.

Miniature Single-Particle Immunoassay for Prostate-specific Antigen in Serum Using Recombinant Fab Fragments

Quantitative, miniaturized nucleic acid assays and immunoassays can be developed with single microparticles, microfluorometric detection, and intrinsically fluorescent lanthanide chelates in a multiple assay format to decrease reagent consumption, cost, and assay time. We used recombinant Fab fragments to capture and detect free and total prostate-specific antigen (PSA) from serum in a submicroliter volume single-particle immunoassay. Genetically engineered thiol-Fab or thiolated monoclonal antibodies (mAbs) were covalently attached onto uniformly sized 60-microm maleimide-activated microparticles. Free and total PSA were detected with europium- or terbium-labeled Fab fragments on a single microparticle using a microfluorometer in a time-resolved mode. The detection limit of the free- and total-PSA assays (mean + 3 SD of zero calibrator) was 0.35 microg/L, with a total volume of 330 nL per particle. An excellent correlation was found in microparticle and microtiter-well assays for 21 serum samples: slopes for free and total PSA were 1.06+/-0.03 and 1.03+/-0.02, respectively (S(y|x) = 0.084 and 0.057 microg/L), with intercepts of 0.013+/-0.018 and 0.013+/-0.017 microg/L (R>0.99). Furthermore, the particle-immobilized Fab fragment had a PSA binding capacity 1.5-fold higher than the intact mAb capacity on a single microparticle. Capacity, kinetics, and sensitivity of the Fab fragment and intact mAb assays in the microparticle and microtiter well formats are discussed. With site-specific (cysteine tail) covalent attachment of Fab fragments on a microparticle, subattomole amounts of PSA can be detected quantitatively.

Review of Fingerprint Detection with Lasers, Second Edition

Abstract This revised and expanded edition of Dr. Menzel's 1980 book is lcome book for latent print examiners, forensic scientists, and scientists interested in the fascinating field of latent print visualization. It updates his previous book by including new and advanced optical imaging techniques that have emerged in the last 20 years. These include CCD cameras, near-infrared imagers, ultraviolet imagers, and acousto-optical tunable filters. It also treats new developments in latent print visualization that have occurred during this time such as the use of DFO, ninhydrin analogues, rare-earth chelates, 1,2-indanediones, multi-metal deposition method, and DMAC. Each chapter is well referenced.

Streptavidin-Polyvinylamine Conjugates Labeled with a Europium Chelate: Applications in Immunoassay, Immunohistochemistry, and Microarrays

The favorable properties of lanthanide chelates compared with conventional fluorescent probes have attracted considerable interest. A Eu(3+) chelator, 4,7-bis(chlorosulfophenyl)-1, 10-phenanthroline-2,9-dicarboxylic acid (BCPDA), has been synthesized previously. We here describe immunoassay, immunohistochemistry, and microarray applications of a new streptavidin-based universal polyvinylamine (PVA) detection reagent that is multiply labeled with the europium chelate of BCPDA. Solid-phase time-resolved immunofluorometric assays for biotinylated mouse IgG and prostate-specific antigen (PSA) were developed using the new conjugate as a detection reagent. The new conjugate was also used for the immunohistochemical localization of PSA expression in paraffin-embedded prostatic tissues. A model microarray with spotted biotinylated antibody as target was also performed. Approximately 50-100 BCPDA moieties were covalently bound to PVA, which was then linked to streptavidin via biotin interaction. The macromolecular complex successfully recognized and bound biotinylated detection reagents, e.g., antibodies. The new reagent enabled measurement of solid phase-immobilized biotinylated mouse IgG with a detection limit of approximately 1 pg/assay and demonstrated excellent linearity. In an ELISA-type sandwich PSA assay that included two PSA monoclonal antibodies using the new conjugate as detection reagent, we detected 0.001 microg/L PSA ( approximately 100 fg or approximately 3 amol/assay). Serum samples analyzed for PSA by this method and a commercial assay gave highly correlated results. The new reagent enabled excellent immunohistochemical localization of PSA expression in prostate tissues. Using the new reagent in a model microarray experiment with biotinylated mouse IgG as target, we demonstrated excellent spatial resolution of 5- to 10-nL microspots. The new detection reagent may find important applications in biotechnology.

Fluorescence study of some terbium–oligopeptide complexes in methanolic solution

This study concerned the use of lanthanide chelates to detect glycyl-leucyl-phenylalanine (GLF) and its homologues. Spectroscopic analysis of peptides without or with terbium complexation revealed the formation of (LF) 3(Tb) 2, (GF) 3(Tb) 2, (GLF) 3(Tb) 2 and (FL) 4Tb, (FG) 4Tb complexes with high stability constants in methanolic solutions (p K d>13). Lanthanide chelate emission displayed a large Stokes shift (>270 nm), which allowed Tb chelates of GLF and its derivatives to be used for detection purposes. However, this preliminary study indicated some important limitations associated with lanthanide chelation, such as high methanolic content.

Editorial.

LuminescenceVolume 15, Issue 6 p. 329-329 Editorial Editorial Larry Kricka, Larry Kricka Hospital of the University of PennsylvaniaSearch for more papers by this author Larry Kricka, Larry Kricka Hospital of the University of PennsylvaniaSearch for more papers by this author First published: 05 December 2000 https://doi.org/10.1002/1522-7243(200011/12)15:6<329::AID-BIO638>3.0.CO;2-6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume15, Issue6Special Issue: Special Issue: Lanthanide Chelates and their Applications in Time-resolved FluorometryNovember/December 2000Pages 329-329 RelatedInformation

Time-resolved fluorescence imaging for quantitative histochemistry using lanthanide chelates in nanoparticles and conjugated to monoclonal antibodies.

Tissue and cell examinations have a potential to produce extremely valuable information about antigen quantities in samples. Using currently available methods, a truly quantitative analysis is nearly impossible. We have previously shown that immunohistochemical (IHC) detection of prostate-specific antigen and human glandular kallikrein from prostatic tissue, together with time-resolved fluorescence imaging (TRFI), is a suitable method for obtaining quantitative data from biological samples and that the signal response is linear. In this paper we show that Eu-chelate containing particles in the nanometer range are suitable labels for quantitative IHC. Even single nanoparticle molecules can be detected by TRFI and the signals measured can be readily quantitated. The signal intensity correlates very well with the amount of bound label, and the use of nanoparticles could markedly improve the sensitivity of quantitative IHC methods. TRFI provides a powerful tool for providing quantitative data about antigens or transcripts in tissue sections or cultured cells. It is also of major importance in standardization and optimization of protocols for fixation and tissue preparation, including antigen retrieval methods.

Lanthanide Chelates as Bilayer Alignment Tools in NMR Studies of Membrane-Associated Peptides

Theequimolar complex, consisting of the lipid-like, amphiphilic chelating agent 1,11-bis[distearylamino]-diethylenetriamine pentaacetic acid (DTPA-18) and Tm3+, is shown by deuterium (2H) NMR to be useful in aligning bicelle-like model membranes, consisting of dimyristoylphosphatidylcholine (DMPC) and dihexanoylphosphatidylcholine (DHPC). As shown previously (1996, R. S. Prosser et al., J. Am. Chem. Soc. 118, 269–270), in the absence of chelate, the lanthanide ions bind loosely with the lipid phosphate groups and confer the membrane with a sufficient positive magnetic anisotropy to result in parallel alignment (i.e., average bilayer normal along the field). Apparently, DTPA-18 sequesters the lanthanide ions and inserts into the phospholipid bilayer in such a manner that bilayer morphology is preserved over a wide temperature range (35–70°C). The inherent paramagnetic shifts and line broadening effects are illustrated by 2H NMR spectra of the membrane binding peptide, Leu-enkephalin (Lenk-d2, Tyr-(Gly-d2)-Gly-Phe-Leu-OH), in the presence of varying concentrations of Tm3+, and upon addition of DTPA-18. Two conclusions could be drawn from this study: (1) The addition of Tm3+ to the bicelle system is consistent with a conformational change in the surface associated peptide, and this effect is shown to be reversed by addition of the chelate, and (2) The paramagnetic shifts are shown to be significantly reduced by addition of chelate.

Time-resolved high-performance liquid chromatography fluorescence detector using a nanosecond pulsed light source for detecting lanthanide-chelated compounds

We have constructed a time-resolved fluorescence detection (TRFD) system for the analysis of amino compounds with high-performance liquid chromatography (HPLC) using lanthanide ion chelates. In order to carry out time-resolved measurements, we have employed a nanosecond pulsed xenon-arc lamp as an excitation light source. Amino compounds derivatized by isothiocyanobenzyl-EDTA (IEDTA) with the lanthanide chelate are mixed with an enhancer solution in a post-column manner and detected by TRFD. Taking advantage of a property of the long fluorescence lifetime of the lanthanide chelates, high selectivity against background fluorescence was achieved. In order to demonstrate the usefulness of TRFD, fundamental performance tests were carried out. Details of the system are also described.

Time-resolved fluorescence imaging (TRFI) for direct immunofluorescence of PSA and alpha-1-antichymotrypsin in prostatic tissue sections.

We have developed a direct immunofluorescence technique utilising chelates of the lanthanide ions europium and terbium conjugated to monoclonal IgGs (Mabs) against prostate-specific antigen (PSA) and alpha-1-antichymotrypsin (ACT) for the detection and quantification on the same tissue section. Strong signals without disturbance from tissue autofluorescence were demonstrated in paraffin sections of ten benign and six malignant prostate tissue specimens. The signal intensity increased linearly with the amount of labelled Mab until epitope saturation began. The highest concentrations of bound IgG in tissue sections were 27.3 fmol/pixel for ACT and 7.2 for PSA. Time-resolved fluorescence imaging (TRFI) offers an attractive method for histochemical studies based on specific and quantitative detection of fluorescent lanthanide chelates.

Electrochemiluminescent labels for applications in fully aqueous solutions at oxide-covered aluminium electrodes

Oxide-covered aluminium electrodes as well as other tunnel emission electrodes allow various label molecules having very different redox and optical properties to be excited cathodically. Low detection limits are obtained and the linear calibration concentration range of the labels spans 5 or 6 orders of magnitude. The lowest detection limits are obtained with Tb(III) chelates which can be detected down to picomolar levels in aqueous solution using time-resolved measurement techniques. Luminophores, such as, 9-fluorenylmethyl chloroformate, derivatives of fluorescein and its analogues, aromatic lanthanide(III) chelates, various coumarins and porphyrins can be used as labels emitting in different spectral regions. The extraordinary analytical power of the tunnel emission electrodes lies in the possibility of simultaneously exciting several different labels emitting either in the UV, visible or NIR range and luminescence lifetimes varying from the ns to the ms range. Therefore, wavelength or time discrimination or their combination can be exploited in separation of the electrochemiluminescence signals from different labels.

Computational approaches to the study of some lanthanide (III)-polyazamacrocyclic chelates for magnetic resonance imaging

A set of parameters consistent with the CHARMM force field has been determined for molecular dynamics simulations of several DOTA– and DOTP–Ln(III) chelates. Bonding and van der Waals parameters were derived from the available experimental data and analogy to similar ones in the existing force field. Net atomic charges were derived from ab initio calculations at the Hartree–Fock level to reproduce molecular electrostatic potentials (ESPs), with an effective core potential (ECP) basis set for the metal ion and the 6-31G* basis set for the ligand atoms. The charges are consistent with the TIP3P water model. Preliminary molecular dynamics simulations of the lanthanide chelates in aqueous solution were performed using the Nose–Hoover thermostat at 300 K. The new parameters correctly predicted the molecular structures and stability of the chelates major and minor isomers. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 237–248, 1999

Novel Chelate-Induced Magnetic Alignment of Biological Membranes

A phospholipid chelate complexed with ytterbium (DMPE-DTPA:Yb 3+) is shown to be readily incorporated into a model membrane system, which may then be aligned in a magnetic field such that the average bilayer normal lies along the field. This so-called positively ordered smectic phase, whose lipids consist of less than 1% DMPE-DTPA:Yb 3+, is ideally suited to structural studies of membrane proteins by solid-state NMR, low-angle diffraction, and spectroscopic techniques that require oriented samples. The chelate, 1,2-dimyristoyl- sn-glycero-3-phosphoethanolamine diethylenetriaminepentaacetic acid, which strongly binds the lanthanide ions and serves to orient the membrane in a magnetic field, prevents direct lanthanide-protein interactions and significantly reduces paramagnetic shifts and line broadening. Similar low-spin lanthanide chelates may have applications in field-ordered solution NMR studies of water-soluble proteins and in the design of new magnetically aligned liquid crystalline phases.

Primary cathodic steps of electrogenerated chemiluminescence of lanthanide(III) chelates at oxide-covered aluminum electrodes in aqueous solution

The primary processes occurring at cathodically polarized oxide-covered aluminum electrode are discussed in detail. It is pointed out that more energetic cathodic processes can be induced in aqueous media at thin insulating film-coated electrodes than at any semiconductor or active metal electrode. It is proposed that tunnel emission of hot electrons with energies well above the level of the conduction band edge of water occur, and the thermalization and solvation of the emitted electrons can result in generation of hydrated electrons. The cathodically pulse-polarized oxide-covered aluminum also generates a strong oxidant (or oxidants) at the oxide/electrolyte interface, and it is proposed that this species is the hydroxyl radical which is generated either by cathodic high field-induced ejection of self-trapped holes as oxygen dianions (i.e. oxide radical ions) into the electrolyte solution, or by the action of anion vacancies and/or F +-centers as the primary oxidants capable of oxidizing hydroxide ions or the hydroxyl groups of the hydroxylated surface on the oxide film. These radicals, hydrated electrons/hydroxyl radicals, can act as mediating reductants/oxidants in reduction/oxidation of solutes. The formation of the primary species is monitored by electrochemiluminophores which cannot be cathodically excited at active metal electrodes in fully aqueous solutions, but which can be chemically excited in aqueous media in the simultaneous presence of highly reducing and highly oxidizing radicals.

Endoscopic fluorescence imaging of tissue selective lanthanide chelates

Endoscopic probes have been incorporated into a fluorescent imaging system for the remote quantitation of tissue selective markers. Resolution at the level of 114 line pairs/mm allows visualization of regions that are approximately 6 mm wide. Tissue selective markers, based on polyazamacrocyclic chelates of terbium increase contrast and can be quantified in tissues at the sub-picomole level. Minimally invasive in vivo fluorescence imaging is demonstrated. The potential for application of the system to disease diagnosis and bone graft morphology quantitation is discussed.

Endoscopic fluorescence imaging of tissue selective lanthanide chelates

Endoscopic probes have been incorporated into a fluorescent imaging system for the remote quantitation of tissue selective markers. Resolution at the level of 114 line pairs/mm allows visualization of regions that are approximately 6 mm wide. Tissue selective markers, based on polyazamacrocyclic chelates of terbium increase contrast and can be quantified in tissues at the sub-picomole level. Minimally invasive in vivo fluorescence imaging is demonstrated. The potential for application of the system to disease diagnosis and bone graft morphology quantitation is discussed.

Temporally and Spectrally Resolved Imaging Microscopy of Lanthanide Chelates

The combination of temporal and spectral resolution in fluorescence microscopy based on long-lived luminescent labels offers a dramatic increase in contrast and probe selectivity due to the suppression of scattered light and short-lived autofluorescence. We describe various configurations of a fluorescence microscope integrating spectral and microsecond temporal resolution with conventional digital imaging based on CCD cameras. The high-power, broad spectral distribution and microsecond time resolution provided by microsecond xenon flashlamps offers increased luminosity with recently developed fluorophores with lifetimes in the submicrosecond to microsecond range. On the detection side, a gated microchannel plate intensifier provides the required time resolution and amplification of the signal. Spectral resolution is achieved with a dual grating stigmatic spectrograph and has been applied to the analysis of luminescent markers of cytochemical specimens in situ and of very small volume elements in microchambers. The additional introduction of polarization optics enables the determination of emission polarization; this parameter reflects molecular orientation and rotational mobility and, consequently, the nature of the microenvironment. The dual spectral and temporal resolution modes of acquisition complemented by a posteriori image analysis gated on the spatial, spectral, and temporal dimensions lead to a very flexible and versatile tool. We have used a newly developed lanthanide chelate, Eu-DTPA-cs124, to demonstrate these capabilities. Such compounds are good labels for time-resolved imaging microscopy and for the estimation of molecular proximity in the microscope by fluorescence (luminescence) resonance energy transfer and of molecular rotation via fluorescence depolarization. We describe the spectral distribution, polarization states, and excited-state lifetimes of the lanthanide chelate crystals imaged in the microscope.

Disulfide-tethered solid supports for synthesis of photoluminescent oligonucleotide conjugates: hydrolytic stability and labeling on the support.

Several new disulfide-tethered solid supports (S1-S5) were synthesized, and their resistance against ammonolysis was tested. Among these supports, only the one bearing an N-[15-[(4, 4'-dimethoxytrityl)oxy]-12,13-dithiapentadecanoyl] linker (S4b) tolerated ammonolysis and exhibited properties compatible with the oligonucleotide synthesis by phosphoramidite strategy. The applicability of this disulfide linker structure in postsynthetic oligonucleotide labeling on the support was demonstrated by introduction of two photoluminescent lanthanide chelates or two dansyl groups to the N4-(6-aminohexyl) amino-modified cytosine residues at the 5' end of the oligonucleotide sequence. Subsequent release of the resulting conjugates as their 3'-phosphates was achieved by reductive cleavage of the disulfide bond and precipitation of the conjugate from the solution with ethanol. The fluorescently tagged oligomer obtained showed hybridization properties similar to those of oligonucleotides labeled in solution.

Imaging and Quantitation of a Tissue-Selective Lanthanide Chelate Using an Endoscopic Fluorometer

Tissue spectroscopy and endoscopy are combined with a tissue site-selective fluorescent probe molecule to demonstrate in vitro, spatial, remote, quantitative imaging of the rat small intestine. The probe molecule employed, Tb-3,6,9-tris(methylene phosphonic acid n-butyl ester)-3,6,9,15-tetraaza-bicyclo[9.3.1]pentadeca-1(15),11,13-triene (Tb-PCTMB), is shown to bind with the small intestine and provide improved image contrast. High sensitivity is possible due to the absorption-emission Stokes's shift exhibited by the Tb-PTCMB complex. Excitation is centered near 270 nm and multifeatured emission is observed at 490, 550, 590, and 625 nm. Sprague-Dawley rats were dosed with the Tb-PTCMB complex, which shows biodistribution, leading to preferential binding to the inner surface of the small intestine. It is shown that the fluorescent image, taken at 550 nm, can be used to quantify the amount of Tb-PCTMB present in an excised tissue sample. The 3σ detection limits are found to be in the femtomole range. An optical mass balance for Tb-PCTMB-dosed small intestine is performed and along with radiotracer biodistribution, demonstrates that approximately 40% of the marker probe resides in the endothelial tissue of the small intestine inner lumen. This result is of particular interest since most adult colon cancers develop in this region. These results demonstrate the ability to perform spatial, quantitative, in vitro, endoscopic imaging of a complex biological sample using a probe marker. © 1998 Society of Photo-Optical Instrumentation Engineers.

Hot electron-induced electrogenerated chemiluminescence of rare earth(III) chelates at oxide-covered aluminum electrodes

Aromatic Gd(III) and Y(III) chelates produce ligand-centered emissions during cathodic pulse polarization of oxide-covered aluminum electrodes, while the corresponding Tb(III) chelates produce metal-centered5D4 →7Fj emissions. It was observed that a redox-inert paramagnetic heavy lanthanoid ion, Gd(III), seems to enhance strongly intersystem crossing in the excited ligand and direct the deexcitation toward a triplet-state emission, while a lighter diamagnetic Y(III) ion directs the photophysical processes toward a singlet-state emission of the ligand. The luminescence lifetime of Y(III) chelates was too short to be measured with our apparatus, but the luminescence lifetime of Gd(III) chelates was between 20 and 70 μs. The mechanisms of the ECL processes are discussed in detail.