CAREER: Genetic Diagnostics at Surfaces - Designing a Biological Polyelectrolyte System

Columbia University, New York NY

Investigators

Abstract

The proposed research is a fundamental investigation of biological polyelectrolyte brushes and their interaction with polyelectrolytes in solution. In addition, the research aims to build an important bridge between biotechnology and the field of polymer science, which is increasingly contributing vital insights to biological systems. A huge past research effort has investigated synthetic polymer brushes, consisting of arrays of polymers tethered by one end to a surface. When these polymers are charged (polyelectrolyte brushes) many basic questions remain unanswered: theory has predicted a complex diagram of states but relatively little experiment exists. The research proposed here advances fundamental understanding of polyelectrolyte brushes by focusing on brushes of the single most important charged biological polymer, DNA. Experimental investigations of DNA brushes placed in contact with free DNA solutions will be carried out, with emphasis on measuring equilibrium and kinetic aspects of the penetration of the free DNA into the brush and its attachment ("hybridization") to complementary regions of the tethered DNA. Theory will be simultaneously developed to approach a comprehensive, molecular-based understanding of the mechanisms involved. If successful, this work will: (i) advance basic understanding of polyelectrolyte brushes, (ii) reveal to what extent theoretical frameworks developed for synthetic polyelectrolyte brushes may be carried over to this biopolymer system, (iii) establish how equilibrium and kinetics of the hybridization process reflect internal organization of the brush, and (iv) result in a systematic understanding of the mechanisms involved in the functioning of modern medical and biological technologies such as DNA microarrays. The primary experimental tool will be confocal fluorescence microscopy, with modulated ellipsometry, X-ray photoelectron spectroscopy, and X-ray reflectivity serving as key secondary characterization tools. %%% DNA brushes are at the heart of a biotechnology of enormous importance: the processing of genetic information for disease studies and medical diagnosis by use of DNA chips and microarrays. Since these methods work on the principle of hybridization between surface-tethered and free nucleic acids, the planned research provides the fundamental guidance needed to reduce the current empiricism in their use and optimization. The research program also closely integrates with multiple educational initiatives, including: (1) stimulating intellectual growth by providing research opportunities for students from high school through graduate levels, (2) forging links with the broader educational community through development of a series of experimental units for high school science courses that demonstrate scientific and engineering principles using common "supermarket" materials, and (3) developing new pedagogical structure for the core undergraduate laboratory that will teach students to learn through research-type, objective-driven projects. Successful accomplishment of the research and educational goals of the proposed plan is supported through strategic partnerships, which include George Washington High School, an urban school in the Manhattan School District, and industrial and institutional research collaborations.