Diffractive micro bar codes for encoding of biomolecules in multiplexed assays

Microparticles incorporating micrometer-sized diffractive bar codes have been modified with oligonucleotides and immunoglobulin Gs to enable DNA hybridization and immunoassays. The bar codes are manufactured using photolithography of a chemically functional commercial epoxy photoresist (SU-8). When attached by suitable linkers, immobilized probe molecules exhibit high affinity for analytes and fast reaction kinetics, allowing detection of single nucleotide differences in DNA sequences and multiplexed immunoassays in <45 min. Analysis of raw data from assays carried out on the diffractive microparticles indicates that the reproducibility and sensitivity approach those of commercial encoding platforms. Micrometer-sized particles, imprinted with several superimposed diffraction gratings, can encode many million unique codes. The high encoding capacity of this technology along with the applicability of the manufactured bar codes to multiplexed assays will allow accurate measurement of a wide variety of molecular interactions, leading to new opportunities in diverse areas of biotechnology such as genomics, proteomics, high-throughput screening, and medical diagnostics

Microarrays made easy : biofunctionalized hydrogel channels for rapid protein microarray production

We present a simple, inexpensive, and sensitive technique for producing multiple copies of a hydrogel-based protein microarray. An agarose block containing 25 biofunctionalized channels is sliced perpendicularly to produce many identical biochips. Each microarray consists of 500 μm spots, which contain protein-coated microparticles physically trapped in porous SeaPrep agarose. Proteins diffuse readily through SeaPrep agarose, while the larger microparticles are immobilized in the hydrogel matrix. Without major assay optimization, the limit of detection is 12 pM for a sandwich assay detecting human IgG. These highly flexible, multiplexed arrays can be produced rapidly without any special instrumentation and are compatible with standard fluorescence-based read-out