Speaker: Anwesha Sarkar, Postdoctoral Research Associate with the Department of Physics & Astronomy at Iowa State University
Title: Single Molecule Force Measurements on Live Cells with Atomic Force Microscopy (AFM) and Force Activatable Biosensors
Abstract: Measurement of interaction forces and binding kinetics of ligand-receptor interactions on live cells at single molecular level is extremely crucial for gaining novel biological insights, evaluating potential therapeutic agents for cancer and other diseases as well as for developing new gene and drug delivery approaches. Atomic Force Microscopy (AFM) is a unique tool to investigate protein-protein interactions including receptor-ligand binding. In this talk, I will discuss developing a biophysical method to isolate and measure specific interactions between Discoidin domain receptors (DDRs) which are overexpressed in cancer, fibrosis and other diseases and collagen (ligands of DDRs) in live cells at the single molecule level using atomic force microscopy (AFM). Another commonly over-expressed receptor in diseases which can be targeted in drug delivery by ligand-conjugated nanoparticles is the folate receptor alpha (FRα). In this regard, I will talk about measuring the binding dynamics of this receptor with self-assembled nanoparticles decorated with a folic acid (FA) ligand using AFM and proving that multivalent micelleplexes bind to FRα with a higher binding probability and binding force than monovalent FA. Although various methods have been developed to visualize and quantify Integrin-transmitted cellular forces at the cell-matrix interface, a method with high performance and low technical barrier is still in demand. I will discuss developing a force-activatable coating (FAC), tunable in the tension range of 10-60 pN which can be simply coated on regular cell culture apparatus’ surfaces by physical adsorption, and turn these surfaces to force reporting platforms that enable cellular force mapping directly by fluorescence imaging with high sensitivity and resolution (0.4 µm). I will discuss how tandem tension sensor (TTS), a force activable biosensor developed by us, verifies the rigidity-dependence of integrin molecular tensions in live cells. I will also talk about using another force activatable biosensor, tension gauge tether (TGT), to report a unique mode of cell migration driven by self-generated integrin ligand gradient on ligand labile surfaces.
Bio: Dr. Anwesha Sarkar received her undergraduate degree (B.Sc.) in Physics from St. Xavier’s College, Kolkata, India in 2008, her Master of Science (M.Sc.) from Indian Institute of Technology (IIT) Madras, India in 2010 and a Master of Philosophy (M.Phil.) degree from Institute of Physics (IoP) Bhubaneswar, India in 2011. She received her Ph.D. in Physics from Wayne State University, Michigan in 2015. She is currently a Postdoctoral fellow at the Department of Physics and Astronomy, Iowa State University. Her main research interest is in the studies of interaction forces and binding kinetics of ligand-receptor systems on live cells using Atomic Force Microscopy. She is also interested in employing force activatable tension sensors to map integrin molecular tensions with high resolution and specificity on live cells.
Seminar Host: Ashfaq Khokhar