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Soft matter engineering for cellular bioelectronic interfaces


Type

Thesis

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Authors

Denduluri, Akhila Jyothy 

Abstract

In nature, interactions between living systems and charged entities occur across multiple scales (cells, tissues, organ systems). These interfaces between electrical and living systems, known as bioelectronics, can be leveraged to monitor and modulate biological functions. In partic- ular, investigation of electronic and ionic charge interactions at the individual cell level exposes singular behaviours otherwise obscured by an ensemble average. However, a key limitation is the availability of effective approaches that enable such investigations in a micro-environment mechanically and biologically conducive to individual cells. In this thesis, micron-scale soft-matter (droplets and microgels) were leveraged to develop two such cellular-bioelectronic interfaces. One such interface to leverage cellular charge generating behaviour was developed by in- tegrating commercial flow-cytometric cell-sorting with single-cell double-emulsions(DEs). This platform, known as photosynthetic-organism directed DE-FACS (podDE-FACS), enables rapid in- vestigation of cyanobacteria, microbes with electrogenic capabilities widely used as the biological source of anodic electrons in the development of renewable power-generation devices, known as biophotovoltaics (BPV). However, the efficiency of such devices is too low to translate into practical applications. With an aim to enhance BPV photocurrents through increased electron availability, podDE-FACS was developed to systematically identify rare, highly electrogenic cyanobacteria using Resazurin, a redox-sensitive fluorescent-marker. The platform was used for the isolation, recovery and growth of a previously-unknown highly-reducing cyanobacterial strain. Shifting the focus from charge generation to charge provision, a second soft-matter interface was developed to create a 3D cell-hosting electro-active platform. The fundamental challenge in interfacing cells with electrical set ups, such as electrodes, is the mechanical and dimensional mismatch between biotic-abiotic components. Recent advances in charge providing conducting biomaterials has seen chemical and structural innovation in reducing mechanical mismatch, however, the spatial and dimensional mismatch is yet to be addressed. A novel, bottom-up fabrication approach which enables co-assembly of cells with conducting hydrogel microparti- cles (HMPs) an organic conjugated polymer, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene-sulfonate). This new class of truly three-dimensional, electrically active cell-laden gels are not only micro-porous and injectable, but provide the basis for a 3D conducting cell-gel electrode that closely mimics native tissue micro-architecture.

Description

Date

2022-03-31

Advisors

Knowles, Tuomas

Keywords

microfluidics, cyanobacteria, droplets, PEDOT:PSS, biophotovoltaics, Double emulsions, DE FACS, bioengineering, 3D tissue scaffolds, bioelectronics, biophysics

Qualification

Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Sponsorship
Gates Cambridge scholarship