Fabrication And Applications Of Multicolor QD-encoded Fluorescent Microspheres In Biomedical Field

Semiconductor nanoparticles (QuantumQDs) are a specific kind of nanocrystal newly developed in recent years. QDs provide robust and stable signal intensity, narrow emission spectra, and the broad emission wavelength which can be turned continuously by changing the size and component of the QD particles. Those ideal properties of QDs have been shown in multicolor imaging for bio-sample and vivo tissue. Research has shown that QDs can be linked with biomolecules such as peptides , antibodies , and nucleic acids for use as fluorescent probes. QD-biomolecules in different conjugation protocols have been greatly exploited in a variety of fluoroimmunoassay, cell imaging, and DNA sequencing techniques. Furthermore, the nanoparticles can be utilized more widely after combined with appropriate material. Provided with both outstanding properties, QDs-micrisphere can be used in bio-labeling, detection and so on.For ultrasensitive high-throughput detection, the development of QD-tagged microspheres as a remarkable biomolecular probes can provide a more significant means to surmount the limitations and increase the advantages of QDs in biomedical applications. The basic concept is to develop smart microspheres that have not only conjugated biomolecules on the surface but also built-in codes for rapid target identification inside the microspheres. In this work, fabrication and applications of multicolor QD-encoded fluorescent microspheres in biomedical were studied.Multicolor quantum QD-encoded microspheres have been prepared via the layer-by-layer assembly approach. Polystyrene microspheres were used as templates for the deposition of different sized CdTe QDs/polyelectrolyte multilayers via electrostatic interactions. Antigen have been bound on the outermost layer of the fluorescent microspheres. The immunoreaction between fluorescent microspheres/antigen and corresponding antibody was confirmed by the change of the fluorescent spectra. This approach allowed detection of CND antigen and GPV antigen as actual samples based on the change of fluorescent intensity. The detection ranges of CND antigen and GPV antigen are 20-100 ng/mL and 1-100 ng/mL respectively.Furthermore, we have succeeded to detect rabbit IgG in the multiplexed fluoroimmunoassays. Multicolor quantum QD-encoded microspheres have been prepared via the layer-by-layer assembly approach. Then biofunctional fluorescent microspheres were readily achieved through the well-established binding affinity of avidin and biotin. Sandwich immunoassay was adopted to prove the bioactivity of biofunctional QD-encoded fluorescent microspheres. The effects of ionic strength and pH on this microspheres immunoassay system were studied. This approach allowed detection of rabbit IgG in the range of 1-80 ng/mL.