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CAMP Professor Igor Sokolov: From Biophysics to Nanotechnology

CAMP Professor Igor Sokolov and his group, in the Department of Physics at Clarkson University, are studying a variety of phenomena related to biophysics and nanotechnology. Most of Professor Sokolov's research involves novel use of Scanning Probe Microscopy (SPM), which is also known as Atomic Force (AFM) and Scanning Tunneling (STM) microscopy. The following are brief descriptions of Professor Sokolov's research topics.

Mechanics of Human Epithelial Cells

Professor Sokolov, together with Professor Woodworth of Clarkson University's Department of Biology, is studying the mechanical properties of human epithelial cells (those found in skin and other tissue that lines the surfaces in our body). The decrease in elasticity of epithelial tissues with ageing contributes to many human diseases. This change was previously explained by the increase in crosslinking of extracellular matrix proteins that normally provide elasticity. In their work, Professor Sokolov and his group show that individual human epithelial cells also become significantly more rigid during ageing in vitro. Using Atomic Force Microscopy (AFM), they found that each cell has at least three areas of different rigidity: the area over the nucleus, the cytoplasm, and the cell edge. The Young's modulus for each area is consistently 2-4 times higher in old cells than in young cells. Furthermore, they developed a novel method for direct visualization of the cytoskeleton of ageing cells using the AFM. Using that method they can demonstrate that increased rigidity is associated with a higher density of the cytoskeleton fibers in both cytoplasmic and edge areas.

Going beyond merely cosmetic concerns, these insights may inspire new directions in treating age-related diseases, such as hardening of the arteries, joint stiffness, cataracts, Alzheimer's disease, and dementia.

Figure 3. One can clearly see the strong dependence on pH. Studying these forces for various ionic strengths, position of the pad, etc., one can obtain a force profile of the surface on a nanometer scale. This information is important to study, predict, and optimize various processes involving surface interactions.

Enhancing Bioremediation: Study of Nanoscale Force Interaction between NAPL and Bacteria

Professor Sokolov and Ph.D. student Venkatesh Subba-Rao, together with Professors Stefan Grimberg and Anja Mueller are studying the problem of optimization of bioremediation of oil contamination.. Spills of organic solvents in the environment may result in the formation of nonaqueous-phase liquids (NAPL) in the subsurface. Coal tars or chlorinated solvents are two NAPLs common at industrial sites in the USA and around the world, contaminating large amounts of groundwater and ecosystems. Most of these NAPLs contain known or suspected carcinogens, which may accumulate in the food chain. Bioremediation is thought to be one of the most promising technologies for NAPL remediation. However up to now, its performance is still rather unpredictable. While significant progress has been made in identifying organisms responsible for contaminant degradation even at high contaminant concentrations, little is known about key factors that influence NAPL remediation. The group's research goal is to understand the role of the bacterial surface properties in bioremediation. Furthermore they are trying to identify polymers that induce interfacial property changes and determine their net significance towards enhancing bioavailability. The research focuses on coal tars and creosote as model NAPLs. By functionalizing an AFM tip with NAPL, they will be able to quantify the heterogeneity of NAPL/bacteria interactions as well as to identify specific polysaccharides at the cell membrane that dominate interfacial property changes. Their initial results have shown non trivial interactions between NAPL and a bacterial surface. Professor Sokolov's previous work includes a study of the heterogeneity of electrical charge on the surface of Shewanella putrefaciens, bacteria used for bioremediation of heavy metals in water.

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