Min-Kyu Han

Energy Transfer-Based Multiplexed Assay of Proteases by Using Gold Nanoparticle and Quantum Dot Conjugates on a Surface

Rapid and sensitive assay of proteases and their inhibition in a high-throughput manner is of great significance in the diagnostic and pharmaceutical fields. We developed a multiplexed assay system of proteases and their inhibition by measuring the energy transfer between quantum dots (QDs) and gold nanoparticles (AuNPs) on a glass slide. In this system, while the photoluminescence (PL) of donor QDs immobilized on a surface was quenched due to the presence of AuNPs (energy acceptor) in close proximity, the protease activity caused modulation in the efficiency of the energy transfer between the acceptor and donor, thus enabling the protease assay. In comparison to the QD-dye system, the conjugate of the QD-AuNP gave rise to higher energy transfer efficiency, resulting in quantitative assay of proteases with more sensitivity. When matrix metalloproteinase, caspase, and thrombin were tested, a multiplexed assay was successfully achieved since the AuNP could be used as a common energy acceptor in conjunction with QDs having different colors. Our system is anticipated to find applications in the diagnosis of protease-related diseases and screening of potential drugs with high sensitivity in a high-throughput way.

Global physiological understanding and metabolic engineering of microorganisms based on omics studies

Through metabolic engineering, scientists seek to modify the metabolic pathways of living organisms to facilitate optimized, efficient production of target biomolecules. During the past decade, we have seen notable improvements in biotechnology, many of which have been based on metabolically engineered microorganisms. Recent developments in the fields of functional genomics, transcriptomics, proteomics, and metabolomics have changed metabolic engineering strategies from the local pathway level to the whole system level. This article focuses on recent advances in the field of metabolic engineering, which have been powered by the combined approaches of the various “omics” that allow us to understand the microbial metabolism at a global scale and to develop more effectively redesigned metabolic pathways for the enhanced production of target bioproducts.

Protein profiling in human sera for identification of potential lung cancer biomarkers using antibody microarray.

To identify potential biomarkers of lung cancer (LC), profiling of proteins in sera obtained from healthy and LC patients was determined using an antibody microarray. Based on our previous study on mRNA expression profiles between patients with LC and healthy persons, 19 proteins of interest were selected as targets for fabrication of an antibody microarray. Antibody to each protein and five nonspecific control antibodies were spotted onto a hydrogel‐coated glass slide and used for profiling of proteins in sera of LC patients in a two‐color fluorescence assay. Forty‐eight human sera samples were analyzed, and expression profiling of proteins were represented by the internally normalized ratio method. Six proteins were distinctly down‐regulated in sera of LC patients; this observation was validated by Wilcoxon test, false discovery rate, and Western blotting. Blind test of other 32 human sera using the antibody microarray followed by hierarchical clustering analysis revealed an approximate sensitivity of 88%, specificity of 80%, and an accuracy of 84%, respectively, in classifying the sera, which supports the potential of the six identified proteins as biomarkers for the prognosis of lung cancer.