Developing low-cost, versatile, gold nanocrystal-based bioassays

by Jones, Benjamin J.; Xia, John Q.; Tian, Z. Ryan

Gold nanocrystals' surface plasmon resonance, with the peak position (λmax) sensitive to their sizes and shapes, makes a conc. of the nanocrystals easily recognizable under visible light without using any major instrumentation, which is ideal for rapid biosensing in, esp., point-of-care type field applications. For developing user-friendly and low-cost bioassays, it is important to synthesize low-cost, uniformly sized and shaped, hydrophilic, monodispersed gold nanocrystals with, for instance, surface-immobilized streptavidin that can bind in high affinity and specificity to biotinylated antibodies. Reported here is a simple, facile, generalized soln. route to synthesizing such types of gold nanocrystals, each with a narrow size-distribution in between 5nm and 100nm, which has been successfully scaled up for mass-prodn. of practically marketable bioassay toolkits. The synthesis involves only three reactants, including a gold precursor, a reducing agent, and a capping agent, and the as-prepd. nanocrystals have successfully served as seeds for further growing larger gold crystals. These gold nanocrystals have been characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis spectroscopy, biosensing, etc.