Investigating Mechanotransduction Behaviors of Natural and Engineered Molecular Sensors for Patient-tailored Treatment Paradigms and Regenerative Rehabilitation

Living organisms respond to environmental cues by emitting signals. Mechanosensory physiology has been crucial for survival since the emergence of the first microorganisms 3.7 billion years ago. The ubiquitous and perpetual nature of mechanotransduction phenomena in all life forms underscores the importance of studying the fundamental mechanical responses that sustain and age us. In this thesis, we zoom in to the cellular scale to study calcium, the ion commonly regulated after mechanical loading in neural and muscle cells, and understand how their ion channels activate at different strain levels. We utilized neural cell-embedded cerebral organoids to gain insights into the effects of traumatic brain injury on the human brain. Additionally, we employed 3D stem cell-infused collagen scaffolds to analyze the differences in calcium signaling between young and aged muscle progenitor cells (MPCs) for regenerative rehabilitation purposes. Our findings revealed that fluorescent calcium signals and genetic pathways are triggered depending on the strain and strain rates of impact. Identifying genetic pathways after stimulation can help target gene products that have dire consequences in the cells to prevent activation or progression of disease, particularly in traumatic brain injury (TBI). Similarly, we can better understand the underlying mechanisms at play and develop potential interventions to improve cellular function in agerelated disease. We obtained immediate cellular feedback via confocal microscopy and more detailed feedback via RNA sequencing from the mechanical insults imposed on the tested cellular systems. 

Furthermore, it is crucial to develop tools to measure these cellular forces at a molecular scale. To this end, we constructed programmable and highly tunable architectures for molecular scale measurement using DNA structures composed of single-stranded tiles (SSTs). We designed a micron scale DNA sensor to measure wall shear stress. One notable advantage of DNA-based probes is their ability to incorporate a broad range of functional customizations, such as fluorophores, biotin, and tags for protein conjugation. We leveraged this flexibility to nanopattern polymers onto DNA origami, creating extruded surfaces for novel biosensing. We fluorescently tagged the DNA nanosensor to output an optical signal indicating physical interactions between the probe and its environment. We also excluded the tag to visualize the predicted formation in atomic force microscopy.