Research Projects
 

Nanobiotechnology: Hybrid Materials from Nanoparticles and Biomolecules
Funding: National Institutes of Health (R21), State of Minnesota Partnership for Biotechnology

Scheme for encapsulating nanostructures within crosslinked, amphiphilic block copolymer shells. Surfactants are first assembled around nanoparticles by adding water, and then chemical crosslinking fixes the surfactant shell around the nanostructure.


   
 

     
 

      

Transmission electron micrographs of different encapsulated nanostructures. Top: Gold nanoparticles. Middle: Magnetic, iron oxide nanoparticles. Bottom: Carbon nanotubes.
 

Nanometer-sized objects--such as nanoparticles, nanotubes, nanorods and other nanoshapes--are of great scientific and technological interest because the physical characteristics of these objects can be rationally tailored by manipulating their shape, size and composition. Nanostructures can have unique optical, electrical, thermal and mechanical properties that make them useful tools for biotechnology. Metal, semiconductor and magnetic nanoparticles, for example, have been developed as tags for molecule, organelle and cell labeling, as vehicles for drug delivery and as supports for biomolecule and cell separations. Materials scientists continue to add even more exotic materials (such multicomponent nanowires, nanorings, and nanopods) to the nanotoolbox. However, methods for attaching biological molecules to these materials have not developed as quickly as the materials themselves.

Research in the Taton Group focuses on finding general chemistries that can connect nano-objects to biological molecules. Some of the nanomaterials that have been developed have poor or no surface chemistry, and methods for attaching molecules to nanosurfaces would allow more of these nanostructured materials to be applied to problems in human health. One strategy we have developed for stabilizing and attaching biomolecules to colloidal nanostructures involves wrapping the particles in amphiphilic, crosslinked polymer shells. We have shown this strategy succeeds for metal, semiconductor and magnetic nanoparticles, as well as for carbon nanotubes. Currently, we are attaching these objects to biomolecules of relevance to human health, with the hope that these nano-bioconjugates can be used for in vivo imaging and therapeutics.

This research effort is extremely interdisciplinary, and involves work in organic and polymer synthesis, bioconjugate chemistry, and nanomaterials synthesis and characterization. We also collaborate extensively with other research groups in the Academic Health Center (including the Medical and Pharmacy Schools) and at Mayo Clinic in Rochester, MN to carry out this research.


 

Nanofabricated Bioconjugates as Masks, Mimics, and Barcodes for Cell Biology
Funding: National Institutes of Health (R01)

Scheme for patterned colloids that mimic the organization of porteins at cell-cell interfaces. The objects are fabricated by lithography on silicon wafers, released into free suspension, and then chemically functionalized by proteins that recognize specific partners on cells. Using T cells as a target, these objects are being developed for a variety of diagnostic and therapeutic applications.

 

Cells frequently use patterns of biomolecules to enhance binding and communication with other cells, but because the patterns and messages change with time, it has been difficult to interpret exactly what these patterns mean. We use nanofabrication techniques (mainly at the University of Minnesota's Nanofabrication Center) to manufacture artificial objects that mimic the patterns of biomolecules found on cell surfaces, and then test the responses of other cells that come into contact with these objects. One system we are particularly interested in applying these objects is T-cell activation. Research has shown that the T cells in the human immune system respond to patterns of antigen presented by other cells. We have made micron-scale, protein-functionalized objects that mimic these patterns, and are currently testing their ability to activate T cells against particular antigens. It is our hope that these objects might eventually be used as vaccines, immunizing patients against pathogenic antigens bound to inert nanofabricated objects. We are also investigating the use of these objects as masks and tags for T cells, tailoring the surface of the cells by attaching artificial patterns to the cells' surfaces. Taken altogether, this project integrates nanofabrication, polymer coatings, bioconjugate chemistry and cell biology to improve T cell biotechnology and immunotherapy. The project involves collaboration with investigators at the University of Minnesota's Center for Immunology.

 

Complementary Nanostructure in Nanorod and Nanotube Composites
Funding: U.S. Army (BAA), U.S. Air Force (SBIR)

Scheme for organizing orientable materials with carbon nanotubes. Bulk materials with a tendency to self-organize, such as liquid crystals, commonly form randomly oriented microdomains. In the presence of nanotube templates, however, the materials spontaneously align over larger areas.

 

The physical properties of bulk materials can be significantly affected by mixing in small amounts of solid particles; for example, composite materials made from polymers and reinforcing carbon fibers are strong enough to replace the steel used in airplane fuselages and automobile bodies, with only a fraction of the weight. We are attempting to extend this principle to mesophasic materials, such as liquid crystals and block copolymers, using individual nanostructures as a way of not only filling the material but also directing the organization of the mesophase. We have shown that one-dimensional nanostructures, such as nanotubes and nanorods, can be used as directional templates to modulate the physical properties of liquid crystalline and polymer materials. In the end, our hope is to take materials that already have some tendency towards structural order--such as Kevlar, the liquid crystalline fiber that bullet-proof vests are made from--and make them better.

We are also more generally interested in the physical effects of adding carbon nanotube fillers to commodity polymers. Single-walled carbon nanotubes in particular are expected to create conductive pathways through insulating plastics, to mechanically reinforce soft materials, and to generate controllable optical anisotropy based on nanotube orientation in the bulk. We are currently exploring the properties and potential applications of nanotube composites. Our work on nanotube composites involves polymer synthesis, electron and optical microscope characterization, and collaboration with scientists in the Chemical Engineering and Materials Science departments.