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The University of Southampton

Research project: Roach: Encoded Suspension Microparticle Arrays

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This project aims to use encoded microparticles to allow biological assays (for example immunoassays or DNA hybridisaiton) to be multiplexed i.e. multiple different assays carried out in parallel in a single reaction vessel. This is enormously valuable for selectivity assays.

The microparticle supports are microfabricated from an epoxy polymer, SU8 and include a pattern of ridges that is able to act as a diffraction grating. If a particle is then illuminated, the resultant diffraction pattern can be used to determine the type of particle.

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Surface modification of SU8 and synthesis. For the microparticles to be useful in biological assays, it is very important to develop methods for syntheising ligands such as DNA, peptides or other drug like molecules on the surface of the microparticles. We have demonstrated the preparation of peptides or nucleic acids linked to the surface of the SU8 microparticles using appropriate linkers and developed a range of methods for attaching proteins or pre-synthesied oligonucleotides to the particle surface.

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Multiplexed Assays. We have attached four antibodies specific for different antigens to 4 types of encoded SU8 microparticles. These have been used for immunoassays, to estimate the efficiency of code identification and the sensitivity for an analyte (5.35 fmol or 3.2 × 109 molecules). We have also used the encoding to demonstrate selectivity against a single base mismatch in a DNA hybridization assay.

Broder, G. R., R. T. Ranasinghe, J. K. She, S. Banu, S. W. Birtwell, G. Cavalli, G. S. Galitonov, D. Holmes, H. F. Martins, K. F. Macdonald, C. Neylon, N. Zheludev, P. L. Roach and H. Morgan (2008). "Diffractive Micro
Bar Codes for Encoding of Biomolecules in Multiplexed Assays." Anal Chem 80(6): 1902-1909.
Holmes, D., J. K. She, P. L. Roach and H. Morgan (2007). "Bead-based immunoassays using a micro-chip flow cytometer." Lab Chip 7(8): 1048-56.
Cavalli, G., S. Banu, R. T. Ranasinghe, G. R. Broder, H. F. Martins, C. Neylon, H. Morgan, M. Bradley and P. L. Roach (2007). "Multistep synthesis on SU-8: combining microfabrication and solid-phase chemistry on a single material." J Comb Chem 9(3): 462-72.

Related research groups

Chemical Biology, Diagnostics and Therapeutics
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