Research and applications of biochip technologies

Biochip as a new research field has enjoyed its rapid development in the past 10 years. Using microfabrication technology, thousands or hundred thousands of biological molecules can be assembled on a centimeter square microchip. Those chip-based devices can be used to analyze mutations, antigens, cells, etc. Compared with the traditional analytical instruments, chip-based micro total analytical systems have many advantages, such as reduced size, lower consumption of both reagents and energy contamination-free, etc. Biochip technology is believed to revolutionize the future research in life sciences, disease diagnosis, drug discovery forensic sciences and outer space exploitation in the coming

Fe3O4/Au composite nano-particles and their optical properties

Fe3O4/Au composite particles with core/shell structure were prepared by reduction of Au3+ with hydroxylamine in the presence of an excess of Fe3O4 as seeds.The resultant col-loids,with an average diameter of less than 100 nm,were obtained;the remaining non-reacted Fe3O4 seeds can be removed by treatment with diluted HCl solution.The Fe3O4/Au colloids ex-hibit a characteristic peak of UV-visible spectra,which largely depend on the size of the particle and the suspension medium.The localized surface plasmon resonance peaks red shift and broaden with increased nanoparticle diameter or increased solvent ionic strength.The optical property is very important in the establishment of means for the detection of biomolecules.

Preparation and characterization of Fe_(3)O_(4)/Au composite particles

Using Fe3O4 nano-particles as seeds, a new type of Fe3O4/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au3+ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron micro-scope were used to analyze the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically responsive property and suspension stability of Fe3O4 seeds as well as reduction conditions of Au3+ to Au0 are the main factors which are crucial for obtaining a colloid of the Fe3O4/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak of Fe3O4/Au fluid. For particles with d(0.5)=168 nm, the lmax is 625 nm.

Preparation and application of streptavidin magnetic particles

Two kinds of streptavidin magnetic particles,namely streptavidin GoldMag particles and streptavidin amino terminal particles were prepared by the methods of physical adsorption and covalent interaction respectively.The streptavidin coated on magnetic particle surface,crucial to many applications,was greatly influenced by the choice of the different buffer.Compared with DynalbeadsM-270 streptavidin, the binding capacity for biotin of different streptavidin magnetic particles was determined by enzyme inhibition method,and the coupling capacity and activity of biotinylated oligonucleotide on their sur- face were also analyzed.The results indicated that the streptavidin GoldMag particle prepared by physical adsorption was stable in STE(NaCl-Tris-EDTA)buffer that was frequently used in nucleic acid hybridization and detection.The streptavidin amino terminal particles prepared by covalent interaction could be used both in STE buffer and PBS(phosphate buffered saline)buffer.The biotin binding ca- pacity for 1 mg of streptavidin GoldMag particles and streptavidin amino terminal particles was 4950 and 5115 pmol respectively.The capacity of biotinylated oligonucleotide(24 bp)coupled on 1 mg of GoldMag and amino terminal magnetic particles was 2839 and 2978 pmol separately.These data were about 6-7 times higher than those of DynabeadsM-270 streptavidin.The hybridization results with FITC-labeled complementary probe on magnetic particle surface demonstrated that the oligonucleotide coupled on streptavidin magnetic particles had high biological activity.