Sarah E. Baker

Blood Clot Initiation by Mesocellular Foams : Dependence on Nanopore Size and Enzyme Immobilization

Porous silica materials are attractive for hemorrhage control because of their blood clot promoting surface chemistry, the wide variety of surface topologies and porous structures that can be created, and the potential ability to achieve high loading of therapeutic proteins within the silica support. We show that silica cell-window size variation in the nanometers to tens of nanometers range greatly affects the rate at which blood clots are formed in human plasma, indicating that window sizes in this size range directly impact the accessibility and diffusion of clotting-promoting proteins to and from the interior surfaces and pore volume of mesocellular foams (MCFs). These studies point toward a critical window size at which the clotting speed is minimized and serve as a model for the design of more effective wound-dressing materials. We demonstrate that the clotting times of plasma exposed to MCF materials are dramatically reduced by immobilizing thrombin in the pores of the MCF, validating the utility of enzyme-immobilized mesoporous silicas in biomedical applications.

Stabilizing Fe Nanoparticles in the SmCo5 Matrix

We report a new strategy for stabilizing Fe nanoparticles (NPs) in the preparation of SmCo5-Fe nanocomposites. We coat the presynthesized Fe NPs with SiO2 and assemble the Fe/SiO2 NPs with Sm-Co-OH to form a mixture. After reductive annealing at 850 °C in the presence of Ca, we obtain SmCo5-Fe/SiO2 composites. Following aqueous NaOH washing and compaction, we produced exchange-coupled SmCo5-Fe nanocomposites with Fe NPs controlled at 12 nm. Our work demonstrates a successful strategy of stabilizing high moment magnetic NPs in a hard magnetic matrix to produce a nanocomposite with tunable magnetic properties.

Predicting the results of chemical vapor deposition growth of suspended carbon nanotubes.

The successful growth of suspended carbon nanotubes is normally based on purely empirical results. Here we demonstrate the ability to predict the successful suspension of nanotubes across a range of trench widths by combining experimental growth data with a theoretical description of nanotube mechanics at the growth temperature. We show that rare thermal oscillations much larger than the rms amplitude combined with the large nanotube-substrate adhesion energy together are responsible for unsuccessful nanotube suspensions. We derive an upper limit on the number of deleterious nanotube-substrate interactions that can be tolerated before successful growth becomes impossible, and we are able to accurately explain literature reports of suspended nanotube growth. The methodology developed here should enable improved growth yields of suspended nanotubes, and it provides a framework in which to analyze the role of nanotube-substrate interactions during nanotube growth by chemical vapor deposition.

Covalently-linked Adducts of Single-walled Nanotubes with Biomolecules: Synthesis, Hybridization, and Biologically-Directed Surface Assembly

Covalently-linked adducts of single-walled carbon nanotubes (SWNTs) with biomolecules have been fabricated. Results are presented here for DNA-SWNT and for biotin-SWNT adducts. DNA-SWNT adducts are shown to be biochemically accessible and to exhibit high selectivity, favoring hybridization with complementary vs. non-complementary DNA sequences. Biotin-SWNT adducts were also prepared and used to direct the assembly of nanotubes onto a biotinylated glass surface.