A Living Transistor Chip to Measure Cellular Activity in a Bacteria Population at Single-Cell Sensitivity in Real Time
Abstract
Coupling to the machinery of a microorganism is a profoundly attractive avenue for making tractable electronic circuitry by leveraging its ability to adapt in response to environmental change. Gating a transistor in water by cell membrane potential of the microbe is an ideal electronic device element as the biochemistry of the cell is unperturbed because there is no electron exchange. However, driving a transistor (i.e., gating) with microorganisms has not been possible due to their thick cell walls. To our knowledge, we have made the first living electrochemical field-effect transistor (LeFET) coupled to the photosynthesis of microalgae and single virus infection that demonstrates single-cell sensitivity. The LeFET quantitatively measures the modulation of cell membrane potential in real time and was based on the first single-electron eFET made from a special architecture of nanoparticle arrays. The devices were individually fabricated by local dispensing of adhesive to hermetically seal them for operating in liquid. The goal of the proposed STIR program is to take the next step in microfabricating a living hybrid chip with an array of LeFET devices that interfaces with a colony of microbes where each device is gated by a single cell in the population. The key innovation is the special architecture of the device channelÑthe nanoparticle necklace network (N3). One-dimensional (1D) necklaces of 10 nm gold (Au) particles are made by directed self-assembly The necklaces are deposited by centrifuge to form a self-limited monolayer to form a 2D network. The N3 exhibits a robust single-electron effect (i.e., Coulomb blockade) at room temperature (RT) using large particles (~ 10 nm diameter). Usually, to obtain a Coulomb blockade at RT, the particles are < 3 nm, which have significant quantum noise due to their sensitivity to size caused by thermal expansion. The first goal will be to demonstrate a living hybrid chip composed of ~ 20 LeFETs integrated on an ~1 cm2 chip. The second goal will be to study a microbe-based phenomenon that has great biological significance to underscore the measurability of the cellular response and its heterogeneity in a cell population using persister and nonpersister states of Escherichia coli. The study for both goals will probe a defined cellular signaling pathway to cause cell membrane potential modulation for gating. Persister cells observed in all bacteria studied have a special dormancy where antibiotic efflux activity, such as a resistance-nodulation-division (RND) pump is enhanced to evade toxins, such as antibiotics. It is a phenotypic change that is not genetic or heritable, so the cell can be reversibly switched back to a nonpersister state to subsequently propagate infection. Because an RND is driven by proton motive force, its operation will lead to modulation in cell membrane potential to cause measurable gating. Our research strategy will be to choose a chemical stimulant (such as antibiotics) that also provides a macroscopic fluorescence signal as a benchmark to validate the LeFET and quantify the switching from persister to nonpersister state in realtime. The overarching goal of such a chip is to develop an adaptable hybrid system where the evolutionary response of a microorganism colony in response to external stimuli can be quantitatively captured to develop complex functionality. For example, the evolutionary response could be coupled to machine learning algorithms to develop intelligent sensing algorithms for a complex environment; or a network of chips could be developed with bioengineered microbes targeting human behavior signatures to help make complex decisions. The chip would be a tool for fundamental electromicrobiology research on a cell population (not possible today) and a screening tool for rapid determination of antibiotics for sepsis treatment personalized to a patient.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 25, 2021
- Source ID
- W911NF2110224
Entities
People
- Ravi F Saraf
Organizations
- Army Contracting Command
- United States Army
- University of Nebraska–Lincoln