Shivani Shukla, Bioengineering (BENG) PhD Program, UC San Diego
Co-mentors: Zeinab Jahed and Lingyan Shi

Electrical signaling governs muscle contraction, brain function, and insulin secretion. While clinical EEG/ECG
techniques signify aberrant electrical activity during disease, it is unclear how single cell action potentials (APs)
are affected by disease or drugs. Gold standard electrophysiology tools such as patch clamp and extracellular
microelectrode arrays are insufficient tools for recording APs from many cells for hours, weeks, or months. The
goal of my project is to develop a higher throughput and tunable platform for obtaining electrophysiological
signals from single adherent cells with millisecond resolution. In this seminar, I will present our newly developed
platform which contains arrays of nanopillar (NP) electrodes made using maskless photolithography and a two-
step dry and wet etching technique. We optimized various surface functionalization techniques to improve
adhesion of diverse cell types on our platforms. We demonstrate electrical recording from electrogenic 2D cardiac
monolayers, 3D printed cardiomyocytes, neuron-like PC12 adherent cells, and bacterial biofilms, demonstrating
multi-scale, multi-kingdom electrophysiological capabilities using a single device. We observed intracellular
action potentials for several days in 2D monolayers and 3D-printed cardiomyocytes with altered waveforms,
indicating differences in cytoarchitecture for drug screening. 3D cultures grown on paired-electrode platforms
showed simultaneous APs and extracellular spiking within a 10 um distance, suggesting the possibility of
extrapolating APs from in vivo extracellular signals. In differentiated PC12 cells, intracellular APs were recorded
over several days for the first time, and morphologies of neurites atop nanopillars were characterized using
fluorescence microscopy and electron microscopy. Our platform was redesigned to house bacterial biofilms,
which show membrane potential oscillations in response to high potassium flow. Biofilm electrophysiology
directly influences antibiotic resistance and gut microbiome heterogeneity. The versatility of our nanopillar
electrode arrays to record electrical signals from cells with a range sizes from 2 um - 30 um in diameter offers a
powerful tool for understanding how single cell electrical activity affects function and disease.

The video of this presentation is available here.