Welcome to Dr. Xiao Li's Webpage
Chemistry Department
Texas A & M University-Commerce

Research Interests

Revolutionary advances in analytical chemistry coupled with compelling problems in biology have led to the emergence of the interdisciplinary field of bioanalytical chemistry. The goal of this field is to understand both qualitatively and quantitatively chemical composition, structure and interactions in biological systems down to the single molecule or even atomic levels. Research at this scale has great potential for breakthroughs in both fundamental science and technology.

I am interested in conducting creative research in the field of bioanalytical chemistry at the single-cell and single-molecule level. Two major bioanalytical areas are emphasized in my research plan. The first area examines the activity, composition and distribution of chemicals in a living cell and the structure and function of a single biomolecule using surface enhanced Raman spectroscopy (SERS). The second area uses scanning electrochemical microscopy (SECM) to detect and image the activity of a cell and its response to external stimuli.

It is well established that neurons release multiple transmitters and possible co-transmitters upon stimuli. One of the goals of this project is to detect, identify and follow the release processes of different species simultaneously upon stimuli. By monitoring the different concentration growth rates, the kinetic information during both phasic and tonic neuron firing of different moieties and the relationship between these processes can be obtained.

With high spatial resolution (1 mm for laser focusing) and by incubating Au nanoparticles into the cell, SERS opens up an exciting opportunity to explore the storage distribution within the cell. More important, single-molecule SERS can characterize the time-dependent behavior of a neurotransmitter within the cell, which generates information about the dynamic interaction between the molecule and its surroundings, such as the acidic proteins within the dense core vesicles and the proteins in the plasma membrane.

With its good specificity to certain drugs which is electrochemical active, an ultramicro electrode (UME) can be used to study the cell activity and its drug response. SECM provides information concerning the mass transport processes across the plasma membrane and interactions between drug and cell components during the cytotoxicity processes. This is of great importance to the understanding of the inhibition mechanism and the structure functionality relationship of the drug. With the aid of theoretical modeling, kinetic information concerning the cross membrane transport can be obtained.

Furthermore, with continuous progress in UME fabrication, the electrode tip is becoming smaller and the shape of the tip is more controllable. Under precise spatial control, an electrode tip with a sharp conical shape can be pushed into a single cell. Thus, electrochemical information can be obtained concerning the different components and reactions within and outside of the cell membrane. It will greatly increase the capability of electrochemical methods in biological systems to probe the composition, distribution and reaction of electrochemically active species within a cell.