NUS CHEMICAL & BIOMOLECULAR Engineering


	YANG, Kun-Lin
	Assistant Professor
	PhD (EnvE. Eng.) Georgia Tech, 2002 MSc (Chem. Eng.) Natn’l Taiwan, 1996 BSc (Chem. Eng.) Natn’l Taiwan, 1994
	Contact information Blk E5, 4 Engineering Drive 4, #03-07, Singapore 117576 Tel: (65) 6516 6614 Fax: (65) 6779 1936 Email: cheyk@nus.edu.sg
	PostDoc (Chem. Eng.) UW-Madison, 2005

RESEARCH

My research will impact the areas of advanced materials, molecular engineering, surface and colloid chemistry, nanobiotechnology, chemical and biological sensing, and molecular modeling. The plan described below is organized into three project areas: (1) Metal ion-based chemical sensing microarrays for real-time odor detection. (2) Real-time electrochemical analysis of single living cells using field effect transistor biosensors. (3) Use of liquid crystals as a label-free analytical tool for detecting hybridization of DNA.

Metal Ion-Based Chemical Sensing Microarrays for Real-Time Odor Detection

The focus of this project is the development of principles for chemical sensing relevant to environmental and defense applications based on mechanisms underlying our olfactory system. My past research has led to the rational design of supported films of liquid crystals for the detection of P- and S- containing compounds, which are ubiquitous in chemical warfare agents and in environmental pollutants. The development of these principles is noteworthy because they have been shown to permit reporting of parts-per-billion levels of organophosphonates and can be broadly used as real-time sensors or passive monitors of chemical exposure.

Real-Time Electrochemical Analysis of a Single Living Cell Using Field Effect Transistor Biosensors

The function of a cell depends critically on the interactions among various proteins along specific signaling pathways, which are typically regulated by many factors including calcium ions and kinase activity. Measurements of calcium concentration and kinase activity in a single living cell will yield a better understanding of cell proliferation, gene expression, and cell apoptosis. I propose to nanofabricate and molecularly engineer field effect transistor (FET) biosensors to monitor calcium ions and kinase activity in a single living cell. The challenge in performing real-time electrochemical analysis in a single living cell using FET biosensors is several-fold. First, the sensing devices must be small enough to not greatly perturb the cell. Because the FET is fabricated via lithography, its size can be tailored to match the cell size (~ 1 mm). Second, the sensor must be robust enough to survive intracellular environments. The proposed covalent modification of the FET through direct Si‑C bond formation offers long-term robustness and stability.

Third, biofouling caused by nonspecific adsorption of protein should be considered. This problem will be addressed by decorating the surface of the biosensor with poly(ethylene glycol) (PEG) monolayers. I plan to use the FET biosensor and combine it with patch clamp to monitor the fluctuation of calcium ions, activities of calcium transporters, and kinase activities in growing cancer cells or stem cells.

Use of Liquid Crystals as a Label-Free Analytical Tool for Detecting Hybridization of DNA

The detection of DNA hybridization has both scientific and technological importance in gene therapy, diagnosis of hereditary diseases and detection of pathogens. Currently available detection methods, however, are mainly fluorescence-based techniques that require labeling the DNA. Here I propose a simpler, faster, and label-free alternative for detecting hybridization of DNA by taking advantage of DNA probes with a stem-and-loop structure and liquid crystals (LCs) that are sensitive to the molecular details of the interface. The detection principles are based upon two recent studies. First, it has been shown that stem-loop DNA probes only bind to perfect-match DNA targets and subsequently undergo conformational changes from stem-loop to rigid double helix structures. Second, the orientation of LC is sensitive to amphiphiles adsorbed at the aqueous-LC interface. A binding event involving the amphiphiles can trigger an orientational transition in the LC phase and permit amplification of the binding event into an optical signal visible with the naked eye.

SELECTED PUBLICATIONS

Yang, K.-L., Cadwell, K., Abbott, N. L. “A Mechanistic Study of Anchoring Behavior of Liquid Crystals Supporting on Metal Salts and Their Orientational Responses to Dimethyl Methyl Phosphonates” Journal of Physical Chemistry B, (accepted), 2004.

Yang, K.-L., Cadwell, K., Abbott, N. L. “Use of Self-Assembled Monolayers, Metal Ions and Smectic Liquid Crystals to Detect Organophophonates” Sensors and Actuators B, (in press), 2004.

Y.-Y. Luk, Yang, K.-L., Cadwell, K., Abbott, N. L. “Deciphering the Interactions between Liquid Crystals and Chemically Functional Surfaces: Role of Hydrogen Bonding on Orientations of Liquid Crystals” Surface Science, 570, 43-56, 2004.

Yang, K.-L., Cadwell, K., Abbott, N. L. “Contact Printing of Metal Ions onto Carboxylate-Terminated Self-Assembled Monolayers” Advanced Materials, 15, 1819-1823, 2003.

He, J., Ritalahti, K. M., Yang, K.-L., Koenigsberg, S. S., and Löffler, F. E., “Detoxification of Vinyl Chloride to Ethene Coupled to Growth of an Anaerobic Bacterium” Nature, 424, 62-65, 2003.

Yang, K.-L., Yiacoumi, S., and Tsouris, C., “Proton Adsorption inside Charged Platinum Nanochannels” Nano Letters, 12, 1433-1437, 2002.

Yang, K.-L., Yiacoumi, S., and Tsouris, C., “Monte Carlo Simulations of Electrical Double-Layer Formation in Nanopores” Journal of Chemical Physics, 117, 8499-8507, 2002.

Yang, K.-L., Yiacoumi, S., and Tsouris, C., “Electrosorption Capacity of Nanostructured Carbon Aerogel by Cyclic Voltammetry” Journal of Electroanalytical Chemistry, 540, 159-167, 2002.

Yang, K.-L., Yiacoumi, S., and Tsouris, C., “Canonical Monte Carlo Simulations of Fluctuating-Charge Molecular Water between Charged Surfaces” Journal of Chemical Physics, 117, 337-345, 2002.