I am interested in the biophysics and mechanisms of mechanobiology, i.e., the role of mechanical force in the evolution of structure and function in human pluripotent stem cell derived cardiomyocytes (hPSC-CMs) including related topics of cell adhesion, downstream signaling and mechanoresponse. My lab has developed technologies to enhance maturity in hiPSC-CMs and make quantitative measurements of cell responses to drugs or in the presence of disease mutations. My research interests span from custom microtechnologies for small-scale mechanical measurements to questions of how mechanics mediate biological signaling. Normal force sensing, remodeling and load bearing by cells are essential for basic life processes. My training and experience as an engineer have provided me with the skills and knowledge to perform quantitative mechanobiology research. When I started my laboratory, there was a dearth of portable force measurement techniques, which limited the integration of biophysical assays with direct analysis of neural networks (e.g., patch clamp electrophysiology) or simultaneous imaging of cellular processes (e.g., cardiomyocyte cytoskeleton dynamics). We have now bridged these technology gaps and enabled new bioengineering strategies to address complex mechanobiology problems in novel ways across large scales of force and anatomical size. Notably, we have integrated live cell mechanical and functional analyses (Ribeiro 2015 and Ribeiro 2017) to show a critical role for tension in developing more physiological hiPSC-CMs. Collectively, these studies have laid the foundation for ongoing work to combine tools for the study of mechanobiology of the cytoskeleton and cell adhesions under different mechanical states. I have enjoyed active collaborations for over a decade with leading cardiac stem cell and myopathy researchers to study a range of mutations, including the labs of Dan Bernstein, Euan Ashley, Sean Wu, Sean Palecek, Jim Spudich, Bruce Conklin, Deepak Srivastava, Helen Blau, and Joe Wu. These collaborative activities have advanced knowledge and propagated methods across our labs, facilitated the open exchange of materials and information and have resulted in several joint publications.
The development of custom micro and nano-scale sensors and actuators is essential for our exploration of mechanobiology, sensor networks or micro-scale material characterization. Transduction methods are selected based on the applications but we design tools leveraging piezoresistivity, piezoelectricity, comb-drive structures, electrochemistry, etc. Piezoresitivity in silicon cantilever structures has been explored in great detail in our lab. From this, our lab developed PiezoD, an open source software tool for modeling the performance and optimizing the design of piezoresistive and piezoelectric sensors and actuators.
We integrate tools and methods to probe the mechanosignaling across and within cells using: extracellular matrix micropatterning to drive different states of cytoskeleton strain energy; traction force microscopy (TFM) to measure cell-generated traction forces; Förster resonance energy transfer tension biosensors to measure molecular tension in structural proteins; and microfabricated tools to apply controlled stretch or forces to multi-cellular structures.
Many diseases of the heart muscle (cardiomyopathies) are directly tied to malfunction of heart muscle cells (cardiomyocytes, CMs). Cardiomyocyte morphology, particularly the length-to-width ratio, is used as a metric of cardiac pathology and remodeling. We are building devices to evaluate how CMs respond to mechanical stimuli such as cell shape and substrate stiffness. These mechanical stimuli cause changes in the intracellular structure of CMs and thus alter their ability to generate contractile forces. We selectively micropattern extracellular matrix proteins on hydrogel platforms to restrict cell size and arrangement while monitoring cellular morphology and traction forces using fiducial markers within the gels.
The sense of touch is the least understood of all our senses, yet is crucial our everyday lives. Imagine trying to walk around the room without being able to feel when you have made contact with the floor. To quantitatively characterize the sense of touch, we build micron-scale technology for mechanical stimulation, including cantilevers with integrated piezoresistive strain gauges and microfluidic traps, to study the nematode C. elegans as a model system. With our collaborators, we integrate our custom instrumentation with patch clamp electrophysiology and fluorescent calcium sensors to measure activation of touch neurons.