Dr. Liu Research
Synthesis, characterization and biomedical and sensing applications of water-soluble conjugated glycopolymers, glycodendrimers, glyconanopaticles, conjugated polyelectrolytes, small redox-active carbohydrate conjugates, and functional carbon nanotube arrays.
Carbohydrates play important roles in key recognition events with a variety of receptor proteins such as hormones, enzymes, toxins, lectins, antibodies, viruses, and bacteria. They are also involved in numerous biological processes such as cell growth, recognition and differentiation, cancer metastasis, inflammation, bacterial and viral infection. These specific interactions occur through glycoproteins, glycolipids, and polysaccharide displays found on cell surfaces and proteins with carbohydrate-binding domains called lectins through cooperative multiple interactions since it is known that individual carbohydrate-protein interactions are generally weak. We are developing new approaches to study carbohydrate-protein interactions for biosensing applications for bacteria, toxins, virus, and cancer cells.
Chemical and Biological Sensors
We develop advanced technology in chemical and biological sensors for medical diagnostics. Our goal is to develop highly sensitive, low-cost and fast-response sensors for proteins, hormones, nucleic acids, bacteria, cells, toxins, viruses and other biological compounds such as glucose and cholesterol.
1) Fluorescent conjugated glycopolymers, which combine fluorescent scaffolding and carbohydrate reporting functions into one package, provide very useful means to study carbohydrate-protein interactions for biosensing applications because of their intrinsic fluorescence and their high sensitivity to minor external stimuli due to amplification by a cooperative system response. We have developed prepolymerization and postpolymerization functionalization approaches to quickly attach different carbohydrates to fluorescent conjugated polymers through thioether bridges for well-defined conjugated glycopolymers such as fluorene-based conjugated glycopolymers, glycopolythiophenes and glycopoly(p-phenylene)s. We are preparing different highly water-soluble well-defined fluorescent conjugated glycopolymers bearing a variety of carbohydrates for biosensing applications.
2) One of current research efforts in our laboratory is focused on developing techniques involving chemical and biological nanosensors at the single cell level. One strategy is to design and synthesize functional conjugated polymers to modify carbon nanotube electrodes via strong pi-pi stacking interaction between the polymers and the nanotubes. Artificial and biological receptors such as enzyme, antibody and single strand DNA will be incorporated into the synthetic functional conjugated polymers. Electrochemistry is employed to detect chemical or biological recognition.
We are developing advanced technology to enhance solubility and quantum yield of conjugated polymers in different solvents including water. We are particularly interested in water-soluble polymers with highly branched dendrimers for drug delivery to reduce the toxicity of drugs, increase their absorption, and improve their release profile. One advantage of polymers is that the linkage can be designed to control where and when the drug is released.
Three-dimensional Network Nanomaterials
We design and synthesize novel functional conjugated polymers to solubilize and functionalize single-walled carbon nanotubes (SWNTs) while keeping almost all intrinsic properties of SWNTs. We are exploring technologies to assemble and cross-link SWNTs or nanoparticles into highly regular three-dimensional networks for many potential applications such as chemical and biological sensors, and electronics.
Skills for Job Hunting
Students in our group will work in a stimulating environment because of the interdisciplinary nature of the research. You will learn to design experiments to test scientific hypotheses using analytical methodologies such as HPLC, UV-vis spectrophotometry, fluorescence spectroscopy, and electrochemistry. You will develop skills in organic and polymer synthesis and characterization by using GC-MS, LC-MS, NMR, and gel permeation chromatography.