Date of Award

8-1-2017

Degree Name

Master of Science

Department

Mechanical Engineering

First Advisor

Chowdhury, Farhan

Abstract

It is now well accepted that mechanical environment partly defines the cellular behavior. The understanding of cell interactions with mechanical microenvironment is the most crucial step to control cell functions in disease and development. Living cells utilize cell surface receptors to interact with the ligands present in mechanical environments. Over the last few decades, several dominant techniques such as AFM, optical tweezers, magnetic tweezers, biomembranes force probes etc. have been extensively used to characterize the ligand-receptor interactions at the molecular level. These studies provided a plethora of information regarding molecular force loading and unloading features. However, these rupture forces have been shown to be strongly dependent on the rate of force application. Yet, it remains poorly understood what is the rate at which cells apply forces via ligand-receptor interactions that consequently defines rupture force relevant to living cells. Our goal is to create a bulk sensor that can detect the rate of cellular force application during early stages of cell adhesion and spreading. We hypothesize that using a quartz crystal microbalance (QCM), an ultra-sensitive piezoelectric device, can provide us with changes to the resonant frequency of the device due to the cellular probing (force application) of the QCM surface, and from the frequency shift we can isolate a mass change on the surface, calculate the coupling coefficient of the cells with their interaction with the substrate. A self-assembled monolayer (SAM) will be functionalized on top of the quartz crystal bonded with gold, the top component of which is the cyclo-RGD that interacts with the αv β3 integrins on cell membrane, henceforth we’ll study the ligand-receptor interaction. The loading rate was quantified through the experiment for variable cell numbers and loading rate and peak force generated on the surface due to ligand-receptor interaction was calculated. The loading rate found was the mean of all cells applying force cumulatively on the surface.

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