Chip based assays such as DNA or protein microarrays, where each sample is identified by its x, y coordinate on the substrate, currently possess the highest sample density (samples/area) of any format. It seems possible that particle based assays could provide far higher sample densities than a planar monolayer format (there are 1000,000,000 ten micron particles/mL). But in order to approach the sample density of the current chips, some sort of identifying label or barcode is needed that is capable of individually distinguishing at least as many samples as current chips. Parallel is currently developing a new type of optical encoding material which will be shown to be statistically capable of resolving over 10,000,000,000 samples at 1% color increments in a six color system. A facile, accurate and rapid solution phase synthesis method will be used to prepare beads containing Dy3+, Er3+, Eu3+, Ho3+, Sm3+, and Tm3+ emitters which are all incorporated simultaneously into a single YVO4 host matrix material which can be excited with a single UV excitation source. The optical code is generated from the ratios of the peak intensities of the six colors. Unlike the broader emission peaks emanating from organic dyes or quantum dots, these rare earth based materials emit into narrow, non-overlapping peaks which can be integrated very precisely to generate a unique optical barcode based on the relative ratios of the various emitters. In order to detect this barcode in the presence of organic dyes or reporters emitting the same color as the barcode, Parallel will collaborate with Blueshift Biotechnologies to employ their very rapid scanning technology to time resolve the organic (excited state lifetime approximately 1ns) and inorganic (0.1ms lifetime) emission. The project proposes to develop a new system to label and identify small particles. If the particles can be reliably identified, they can be used to simultaneously keep track of thousands of miniscule assays.
