Diffractive Micro Bar Codes for Encoding of Biomolecules in Multiplexed Assays

Abstract

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.

Multiplexed suspension array platform for high-throughput protein assays

“…SU8 has very good structural properties (Abgrall et al 2007), and features can be quickly and easily defined in a single step photolithography process using standard microfabrication equipment. The residual epoxide groups left on the SU8 surface after polymerization can easily be modified for the attachment (Broder et al 2008) and solid phase synthesis (Cavalli et al 2007;Qvortrup et al 2011) of a wide range of molecules, and biological assay demonstrations on SU8 (Broder et al 2008) show that it is a highly suitable material for suspension array applications. We describe a high capacity encoding method for SU8 microparticles, together with a microfluidic platform for particle alignment during imaging, and custom image analysis software for robust, high throughput readout of assay response and particle codes.…”

Holographically encoded microparticles for bead-based assays

“…We have previously used SU8 to manufacture micronmetresized bars (i.e. beads) encoded with diffraction gratings and demonstrated multiplexed assays [19]. The particles have also been used in conventional multistep solid-state synthesis of oligonucleotides and peptides [20].…”

Development of a versatile biotinylated material based on SU-8

“…24,25 Recently, a swelling-deswelling method for the facile surface modication of 2D and 3D patterns of SU-8 has been described, demonstrating the oligonucleotide attachment.…”