Research Areas
In nature, DNA exists primarily in a highly condensed state. DNA packaging in the cell is typically protein mediated using, for example, histones (in eukaryotic nuclei) or protamines (in sperm cells). The scale of this compaction is immense. For a typcial human chromosome consisting of a single DNA approx. 5 cm in length, every cell thus has almost 2 meters of DNA compacted within its roughly 10 µm size. We work to address fundamental biophysical questions of DNA condensation by integrating x-ray scattering and osmotic stress experiments to investigate how cations mediate DNA-DNA intermolecular forces while extending from in vitro to in vivopackaging, such as mammalian sperm cells. Our long-term goal is to identify the biochemistry that underlies DNA packaging and mispackaging and understand the interrelationship to DNA damage, disease, and reproductive health.
Gene delivery polymers must be designed to perform numerous functions. In particular, the materials must bind and condense nucleic acids (NA) to protect it from extra- and intracellular nucleases and to facilitate cellular internalization. Yet, such materials must release their NA cargo to allow transcription. Numerous relatively efficient gene delivery materials are being investigated, but the mechanisms by which they perform the necessary functions are unknown. Design of more efficient materials requires understanding of polymer-NA interactions, the formation of polymer/NA complexes (polyplexes), and how their structures relate to intracellular trafficking and gene delivery efficiency.
In order to reach target cells, gene complexes must traverse the extracellular matrix (ECM), a crowded, interacting environment of biomacromolecules. Before accessing cells, a particle or a virus must also navigate through even messier milieus such as mucus or bacterial biofilms before successful delivery is possible. In these cases, one often finds that not only charged and uncharged polysaccharides and fibrous proteins of the ECM but even foreign DNA and bacteria can be entrapped in these gels. One can easily imagine the difficulties in interpreting diffusion data through systems which could have many specific and nonspecific interactions such as electrostatics, chemical binding, immobile barriers, and binding sites. For in vivo applicability, both transport properties and efficient delivery of intact gene complexes to the target tissue are crucial. Our group is involved in the study of fundamental questions using fluorescent techniques including fluorescence correlation spectroscopy (FCS) to gain insight into the transport and interactions of gene therapy contructs in complex biological systems.