In this project the PI will introduce a new quantitative technique that permits systematic studies of several fundamental areas in biological physics, including phagocytosis, the actin cytoskeleton and its coupling to membrane, and mechanotransduction. The approach, called the PhagoSensor Technique, uses mechanically characterized, deformable particles as the phagocytotic target. During phagocytosis, the soft particle experiences spatially and time-dependent deformations which reflect the transient forces exerted by the advancing cell extensions (pseudopodia) around the particle. High resolution imaging of the particle deformations combined with simultaneous imaging of the pseudopodia will provide unprecedented data regarding cell dynamics and mechanics during phagocytosis. The cell-generated force field that deforms the particle will be extracted via image processing and application of elastic shell theory. This work addresses three aspects of phagocytosis. First, the robustness and reproducibility of the mechanical signature of phagocytosis will be characterized. Second, the measured force dynamics will be correlated with the most prominent model of phagocytosis, which claims that there are three phases with at least two different and independent sources of contractile force. Last, the mechanosensitivity of macrophage cells by varying the elastic moduli of the PhagoSensors used during experimentation will be investigated. The fascinating and dramatic aspects of the biophysical studies, such as the visually stimulating process of one cell eating another or the holographic optical tweezers will be used to: (1) captivate 4-5th graders once a month in a hands-on after school Science Club; (2) to inspire undergraduates in universities like Florida International University (FIU) to pursue a career in quantitative biophysics; and (3) to extensively train undergraduates at Georgia Tech in a challenging interdisciplinary environment.
