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Yanggu, South Korea

Kim M.I.,KAIST | Yu B.J.,MD Science Inc. | Woo M.-A.,KAIST | Cho D.,LabGenomics Co. | And 4 more authors.
Analytical Chemistry | Year: 2010

We describe a novel multiplex "amino acid array" for simultaneously quantifying different amino acids based on the rapid growth of amino acid auxotrophic E. coli. First, we constructed genetically engineered amino acid auxotrophs of E. coli containing a bioluminescence reporter gene, yielding concomitant luminescence as a response to cell growth, and then immobilized the reporter cells within individual agarose of respective wells in a 96-well plate serving as a mimic of a biochip. Using the amino acid array, we were able to determine quantitatively the concentrations of 16 amino acids in biological fluid by simply measuring bioluminescent signals from the immobilized cells within 4 h without pre- and post-treatment. The clinical utility of this method was verified by quantifying different amino acids in dried blood spot specimens from clinical samples for the diagnosis of metabolic diseases of newborn babies. This method serves as a convenient route to the rapid and simultaneous analysis of multiple amino acids from complex biological fluids and represents a new analytical paradigm that can replace conventional, yet laborious methods currently in use. © 2010 American Chemical Society. Source

Woo M.-A.,KAIST | Kim M.I.,KAIST | Yu B.J.,MD Science Inc. | Cho D.,LabGenomics Co. | And 5 more authors.
Analytical Chemistry | Year: 2011

A cell-based quantitative assay system for Hcy has been developed by utilizing two Escherichia coli auxotrophs that grow in the presence of methionine (Met) and either homocysteine (Hcy) or Met, respectively. A bioluminescent reporter gene, which produces luminescence as cells grow, was inserted into the auxotrophs, so that cell growth can be readily determined. When the relative luminescence unit (RLU) values from the two auxotrophs immobilized within agarose gels arrayed on a well plate were measured, the amount of Hcy was quantitatively determined on the basis of differences between two RLU values corresponding to cell growth of two auxotrophs with excellent levels of precision and reproducibility. Finally, the diagnostic utility of this assay system was verified by its employment in reliably determining different stages of hyperhomocysteinemia in human plasma samples providing CVs of within and between assays that are less than 2.9% and 7.1%, respectively, and recovery rates of within and between assays that are in the range of 99.1-103.5% and 97.5-105.5%, respectively. In contrast to existing conventional methods, the new system developed in this effort is simple, rapid, and cost-effective. As a result, it has great potential to serve as a viable alternative for Hcy quantification in the diagnosis of hyperhomocysteinemia. © 2011 American Chemical Society. Source

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