Three graduate students will present their research Wednesday, March 4 at the next Beckman Graduate Student Seminar: Joanne Fil, neuroscience; Ahyoung Kim, materials science and engineering; and Dinesh Kumar, chemical and biomolecular engineering. The event begins at noon in Room 1005 Beckman Institute. Lunch will be served.

“Nutrition and Brain Development Using a Pig Model”

Joanne Fil, neuroscience

Global health organizations recommend breast milk as the ideal source of nutrients for babies. However, breastfeeding may not be possible for all women due to specific medical situations, lifestyles, or comfort levels. For individuals that either cannot or choose not to breastfeed, infant formula serves as a convenient and healthy alternative. Nutritional technologies being incorporated into infant formulas are continually improving to more closely mimic the essential components that are in breast milk. Polar lipids are structural components of neural tissue that may play important roles in supporting brain development in the infant. Therefore, we were interested in investigating the longitudinal effects of dietary polar lipid ingestion on cognitive and structural brain development in the biomedical pig model

During the first four weeks of life, pigs received an unsupplemented, but nutritionally adequate, control diet; the same diet supplemented with polar lipids to match breastmilk concentrations; or they were sow-reared (to be used as a reference group). After 4 weeks of age, all pigs were placed on the same nutritionally adequate diet until 24 weeks of age (i.e., sexual maturity). At 4 weeks of age, pigs were subjected to the eye blink conditioning behavioral task to observe the influence of supplementation on associative memory. They also performed the novel object recognition task at 4 and 8 weeks of age to test recognition memory. Additionally, pigs underwent longitudinal MRI scans to see the influence of polar lipid supplementation on brain development. Preliminary results indicate that pigs without a supplemented diet had larger relative volumes in the left and right caudate and right putamen-globus pallidus compared with pigs receiving supplemental polar lipids diet. This suggests that synaptic pruning may be occurring faster in pigs provided early-life dietary polar lipids, indicating faster brain maturation, but further analyses need to be performed before making conclusions.

Biography

Joanne Fil is a fourth-year Ph.D. student in the Neuroscience Program. She is part of the Piglet Nutrition and Cognition Lab under Ryan Dilger, an associate professor of animal sciences. The lab focuses on utilizing the pig as an animal model to research the role of nutritional supplementation on neurodevelopment. Fil’s specific area of focus is utilizing magnetic resonance imaging techniques to observe brain development in the pig from birth to sexual maturity to see how comparable pig brain development is to human brain development.

“Using Atomic 'Stencil' to Make Patchy Nanoparticles”

Ahyoung Kim, materials science and engineering

Kim will present the group’s most recent experiment — computation collaboration on a new strategy of atomic stencil to make gold nanoparticles decorated with polymer patches. This strategy utilizes two concepts that are otherwise remotely connected — adatom adsorption and ligand island formation — to mask selectively certain surface sites of gold nanoparticles, thereby allowing subsequent polymer patch adsorption to only the unmasked areas. They experimentally demonstrate this method in a diversity of anisotropic gold NPs (triangular prisms, octahedra, cubes, etc.) with polymer patches of precise patterns and sizes. By controlling the ligand to NP concentration ratio, they realize highly uniform patchy NPs, from tip-patches to facet-patches, from symmetric to patch arrangements of breaking symmetry. As a demonstration of their application, it is further shown that the as-prepared patchy NPs can construct varying structures, from self-limited small clusters (dimers, trimers) to large scale open lattices that are otherwise challenging to achieve for NPs of uniform surface chemistry. The group foresees its method can provide hybrid NPs with site-specifically programmed chemistries and interactions for applications in catalytic, delivery and reconfigurable materials, and their directed assembly into exotic functional structures.

Biography

Ahyoung Kim was born and grew up in Seoul. She majored in energy engineering and minored in nanochemistry at Ulsan National Institute of Science and Technology in Korea, where she graduated second in her class. She joined Qian Chen’s group at the University of Illinois in 2016 for her Ph.D. study, and she’s been developing a universal strategy for patchy nanoparticles synthesis and assembly. She is also a PPG-MRL research assistant fellow this year.

“Shape Dynamics of Vesicles in Flow Using a Stokes Trap”

Dinesh Kumar, chemical and biomolecular engineering

Vesicles are membrane-bound soft containers that are ubiquitous in biological systems and drug delivery applications. Lipid vesicles are used in a reductionist model system to study the mechanical properties of biological cells. Here, we study the non-equilibrium dynamics of vesicles in precisely defined steady and time-dependent extensional flow. In particular, we use a Stokes trap to control the position and time-dependent strain and strain rate schedules applied to single vesicles in flow. In this way, we directly observe non-equilibrium vesicle shapes as a function of membrane floppiness (reduced volume), viscosity contrast, and flow-strength using fluorescence microscopy. Vesicles are found to deform through a wide range of interesting shapes in flow, including asymmetric and symmetric dumbbells, in addition to pearling, wrinkling, and buckling instabilities depending on membrane properties. We further study the non-equilibrium stretching and relaxation dynamics in extensional flow. We identify two distinct relaxation processes for vesicles stretched to high deformation, revealing two well separated time scales: a short time scale corresponding to bending relaxation and a long-time scale dictated by the membrane tension. Overall, our results provide new insights into the flow-driven shape-instabilities for vesicles using new experimental methods based on the Stokes trap.

Biography

Dinesh Kumar is a graduate student pursuing a Ph.D. in chemical and biomolecular engineering. His research in Professor Charles Schroeder's lab uses precise microfluidic flow control techniques to probe the mechanics and dynamics of lipid vesicles under flow. Dinesh obtained his B.S. in mechanical engineering in 2014 from the Indian Institute of Technology Kharagpur, and his M.S. in chemical engineering from the University of Toronto in 2016.