The present invention concerns a luminescent particle comprising a nanoparticle of formula

A.sub.1xLn.sub.xVO.sub.4(1y)(PO.sub.4).sub.y (I)

in which A is selected from yttrium (Y), gadolinium (Gd), lanthanum (La), and mixtures thereof; Ln is selected from europium (Eu), dysprosium (Dy), samarium (Sm), neodymium (Nd), erbium (Er), ytterbium (Yb), and mixtures thereof; 0<x<1; and 0<y<1; characterized in that the nanoparticle on its surface has tetraalkylammonium cations in an amount such that said nanoparticle has a zeta potential, , of less than or equal to 28 mV in an aqueous medium with a pH5, more particularly with a pH5.5, and with an ionic conductivity >100 S.cm.sup.1.

It also concerns a method for preparing such luminescent particles, a colloidal suspension of these particles, and the use thereof as a diagnostic agent, and also a diagnostic kit comprising such luminescent particles.

The invention relates to complexing agents of formula (I) ##STR00001##
in which A.sub.1, A.sub.2, A.sub.3 and R.sub.1 are as defined in the description. The invention also relates to lanthanide complexes obtained from said complexing agents. The invention can be used for marking biological molecules.

The invention generally relates to materials and methods for creating and/or utilizing upconverting luminescence. More particularly, the invention relates to novel compositions (e.g., nanoparticles) and related methods of preparation and use that enable upconverting luminescence with an efficient excitation optimized at about 800 nm. A unique class of cascade sensitized tri-doped UCNPs with a biocompatiable 800 nm excitable property are disclosed herein, for example, tri-doped -NaYF.sub.4:Nd, Yb, Er (Tm)/NaYF.sub.4UCNPs, which employ Nd.sup.3+ as 800 nm photon sensitizer and Yb.sup.3+ as bridging ions, having strong green or blue upconversion emissions without photobleaching.

This invention relates to a rare earth nanomaterial labeled biomolecule, its labeling method and a dissolution-enhanced time-resolved fluoroimmunoassay based on the rare earth nanomaterial. The rare earth nanomaterial serves as a label having stable properties, large specific surface area, strong modifiability, low-cost and thousands of lanthanide ions contained in each nanocrystal, the labeling ratio of rare earth ions can be greatly improved. Furthermore, the rare earth nanomaterial can be less affected by exogenous rare earth ions, unaffected by anticoagulants, and has broader applicability; after the immune complex was formed by labeling the biomolecules with the nanomaterial containing rare earth, an enhancer solution was added to allow the rare earth nanomaterial to dissolve into the rare earth ions, which can in turn form new signaling molecules with the chelates in the enhancer solution to induce intramolecular and intermolecular energy transfer, thereby significantly increasing fluorescence intensity by about a million times to greatly enhance the detection sensitivity by using time-resolved fluorescence assay.

The present invention provides assays and assay systems for use in spatially encoded biological assays. The invention provides an assay system comprising an assay capable of high levels of multiplexing where reagents are provided to a biological sample in defined spatial patterns; instrumentation capable of controlled delivery of reagents according to the spatial patterns; and a decoding scheme providing a readout that is digital in nature.

To provide a method and kit for measurement of a target substance with high detection sensitivity, provided is a method of measuring at least any one of the presence or absence, and a concentration, of a target substance in a sample liquid, the method including the steps of: (a) preparing a first particle that specifically binds to the target substance and contains a rare earth complex, and a second particle that has a larger average particle diameter than that of the first particle and specifically binds to the target substance; (b) mixing the sample liquid, the first particle, and the second particle to provide a mixed liquid; and (c) determining at least any one of the presence or absence, and the concentration, of the target substance from polarization anisotropy of the mixed liquid obtained in the step (b).

The present invention relates to a method for quantitating an analyte having a wide range concentration in a single assay without having to dilute the sample and repeating the assay. The key feature of the invention is having two cycles of events including sample binding to probe, binding reactions, and detection. After the first cycle of binding and detecting, the probe is dipped into the same sample vessel to bind additional analyte in the sample vessel at a condition that is more favorable to binding than the condition in the first cycle.

The present invention provides assays and assay systems for use in spatially encoded biological assays. The invention provides an assay system comprising an assay capable of high levels of multiplexing where reagents are provided to a biological sample in defined spatial patterns; instrumentation capable of controlled delivery of reagents according to the spatial patterns; and a decoding scheme providing a readout that is digital in nature.

The present invention provides assays and assay systems for use in spatially encoded biological assays. The invention provides an assay system comprising an assay capable of high levels of multiplexing where reagents are provided to a biological sample in defined spatial patterns; instrumentation capable of controlled delivery of reagents according to the spatial patterns; and a decoding scheme providing a readout that is digital in nature.

The invention generally relates to materials and methods for creating and/or utilizing upconverting luminescence. More particularly, the invention relates to novel compositions (e.g., nanoparticles) and related methods of preparation and use that enable upconverting luminescence with an efficient excitation optimized at about 800 nm. A unique class of cascade sensitized tri-doped UCNPs with a biocompatiable 800 nm excitable property are disclosed herein, for example, tri-doped -NaYF.sub.4:Nd, Yb, Er (Tm)/NaYF.sub.4UCNPs, which employ Nd.sup.3+ as 800 nm photon sensitizer and Yb.sup.3+ as bridging ions, having strong green or blue upconversion emissions without photobleaching.