| Multiplexing and miniaturization are becoming pervasive themes in bioanalysis. Drug discovery, drug screening and diagnostics commonly involve carrying out assays on large numbers of molecules and screening for particular target molecules, such as antigens, antibodies, nucleotides and peptides, in test samples. Promising tools for this purpose are the'multiplex technologies', which allow multiple discrete assays to be carried out simultaneously in the same micro-volume sample. The push to measure ever-increasing numbers of species from smaller and smaller sample volumes has led to innovative devices for sample manipulation and ingenious approaches to simultaneous measurement capabilities, and in these approaches, one of the outstanding is suspendant chips. This thesis mainly discusses the construction of quantum dots (QDs) based encoding suspendant microarrays. The main results are as follow:Carboxyl modified 100μm polystyrene (PS) beads were prepared by sulfonation grafting. The surface area and pore volume are greatly improved, and the corresponding carboxyl content is about 2.1 mmol/g. Carboxyl grafted polystyrene beads were precisely encoded by the various ratios of two types QDs whose emission wavelength are 576 nm and 628 nm respectively. The leakage of QDs was greatly decreased and the barcode stability improved greatly by the deposited silica particles on the surface of PS. The anti-photo bleaching of silica-coated beads was systemically studied, which is 7 times longer than the uncoated ones.Then the different encoded beads were covalently immobilized with different human IgG probes and the probe density could reach to 2.0 mmol/g. These probe-linked encoded beads were used to detect the target DNA sequences in complex DNA solution by hybridization. The results show that the QDs and target signals can be obviously identified from single-bead-level spectrum. This strategy can be used to detect DNA targets effectively with a detection limit of 0.2μg/mL in complex solution. DNA probe hybridization experiments indicate that it is feasible to use this kind of beads for multiplex analysis.By Layer-by-Layer assembly technology, well-covered, high-density and stability Au nanoparticles coated PS (Au@PS) was prepared. First, citrate-stabilized and negative charged 20 nm Au nanoparticles were synthesized, then different charged PS were prepared by grafting, and the deposition and assembly of Au nanoparticles on the charged PS core were studied. The coverage degree and shell thickness can be controlled by the assembly time and Au colloids quantity.A novel immunoassay method based on Au@PS was studied. Human IgG was immobilized at the concentration of 16μg/g. The fluorescence imagining experiments indicated the FITC signal could be detected even when the target antibody concentration was as low as 0.01μg/mL on single-bead level spectra and the linear range was 0.05～15μg/mL. The assay results were compared with the ELISA and showed a relatively good reliability.The optical encoding property of QDs based Au@PS beads was also studied. The experiment results showed that the QDs loaded into the porous Au@PS beads reached 1.0182×10-4 mmol/g, which is 7 times more than before the Au coating; the leakage of the doped QDs was remarkably reduced and the anti-photo bleaching ability of the QDs encoded Au@PS beads was also improved; comparing the spectra of free QDs and the doped QDs, it indicated that the doped QDs kept the initial optical property. Mult-color QDs encoding experiments showed that the coded spectra of Au@PS beads had little over-lap; the encoding signals were easy distinguishable on single bead level.The micro-channel based probe-array was fabricated using the QDs-encoded Au@PS beads and its application in immunoassay was studied. The experiments indicated that the assay approach has theμ-volume sample, simple and convenient properties; the encoding could be well identified.Accordingly, several fabrications and applications of QDs encoding PS based bioassay technology were studied in this dissertation. It mainly includes the surface grafting, probe immobilization, QDs fluorescent encoding and fabrication of bioassay systems. The results expand the application fields of the bead-based assay system in chemistry and biology, and establish the bedrock of micro-analysis technologies for future.
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