New trends in immunoassays.

This article takes a special focus on signal amplification technologies in immunoassays and new generations of lateral-flow assays. Novel signal amplification technologies based either on new classes of biofunctional nanocrystals consisting of releasable fluorophores or on aggregation-induced emission (AIE) can improve the sensitivity and the limits of detection in immunoassays. A bio-barcode assay also allows signal amplification by utilizing antibody-coated magnetic beads to concentrate the analytes and antibody-coated gold nanoparticle probes to carry with a large number of oligonucleotides.

Biofunctional organic nanocrystals for quantitative detection of pathogen deoxyribonucleic acid.

Advances in nanotechnology have had significant impacts in the field of biodiagnostics. In this study, we describe the novel application of dissolvable, organic and biofunctional nanocrystals for the quantitative detection of a PCR product. Fluorescein diacetate (FDA), a fluorogenic precursor of fluorescein, was milled in a solution of a polymeric surfactant to create a stable, nanosized colloid with an interface for coupling streptavidin molecules.

A highly sensitive fluorescent immunoassay based on avidin-labeled nanocrystals.

Nanocrystals of the fluorogenic precursor fluorescein diacetate (FDA) were applied as labels in order to improve on the assay sensitivity achieved in our previous studies. Each FDA nanocrystal can be converted into approximately 2.6x10(6) fluorescein molecules, which is useful for improving immunoassay sensitivity and limits of detection.

Nanoparticle labels in immunosensing using optical detection methods.

Efforts to improve the performance of immunoassays and immunosensors by incorporating different kinds of nanostructures have gained considerable momentum over the last decade. Apart from liposomes, which will not be discussed here, most groups focus on artificial, particulate marker systems, both organic and inorganic. The underlying detection procedures may be based either on electro-magnetical or optical techniques.

Silole nanocrystals as novel biolabels.

A novel class of biofunctional silole nanocrystals with the potential to create highly sensitive immunoassay was firstly demonstrated. Biolabels were constructed by encapsulating nanocrystalline hexaphenylsilole [Ph2Si(CPh)4HPS] within ultrathin polyelectrolyte layers via the layer-by-layer (LbL) technique that provided an "interface" for the attachment of antibodies. A high ratio of fluorescent dyes to biomolecules (F/P ratio; 2.

Nanocrystal biolabels with releasable fluorophores for immunoassays.

A novel signal amplification technology based on a new class of biofunctional fluorescent nanocrystals holds promise to improve the sensitivity and the limits of detection of immunoassays. A two-step approach without layer-by-layer techniques is described to encapsulate the fluorogenic precursor fluorescein diacetate (FDA) nanocrystals (107-nm average size) followed by conjugation of the antibody. Distearoylphosphatidylethanolamine (DSPE) modified with amino(poly(ethylene glycol)) (PEG(2000)Amine) is coated on the surface of the FDA nanocrystals to provide a interface for the antibody coupling.

Nanoencapsulated microcrystalline particles for superamplified biochemical assays.

We report on the preparation and utilization of a novel class of particulate labels based on nanoencapsulated organic microcrystals with the potential to create highly amplified biochemical assays. Labels were constructed by encapsulating microcrystalline fluorescein diacetate (FDA; average size of 500 nm) within ultrathin polyelectrolyte layers of poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) via the layer-by-layer technique. Subsequently, the polyelectrolyte coating was used as an "interface" for the attachment of anti-mouse antibodies through adsorption.