Development of a novel cell-based biosensor for the detection of cytotoxic effects using astrocyte cell lines

Abstract

Mammalian cell-based biosensors are important tools for drug screening, environmental, clinical, and healthcare applications. Electrochemical impedance spectroscopy (EIS) is a popular transduction mechanism used with mammalian cell-based sensors for the analysis of events occurring close to the surface of the electrodes. However, EIS is a complex electrochemical technique which, in combination with cell-based sensors, faces multiple design and fabrication challenges.

This work investigates the use of electrochemical impedance spectroscopy (EIS) with contactless electrodes to monitor the bulk capacitance of astrocyte type I clone (C8-D1A) cells. The C8-D1A cell line is used as a glia-based model to assess its neurological response to toxins. Our contactless sensors are 'passivated' electrodes with a thick insulating layer of borosilicate glass to which the cells adhere and proliferate. After reaching 80% of confluence, the cells are treated with staurosporine and hydrogen peroxide, potent apoptosis-inducing compounds, and monitored for a further 24 hours.

A computational model is developed using COMSOL to evaluate the sensitivity of an impedance-based biosensor for detecting changes in cell proliferation and death. The simulations performed show that the biosensor should be able to penetrate the insulating layer, polarise the cells, and provide unique impedance measurements corresponding to changes in cell viability. The results suggest the proposed biosensor has the potential to be a powerful tool for monitoring the health of cells in applications such as toxicology studies.

An improved contactless cell-based biosensor is designed and developed, using multiple types of electrodes. Coplanar parallel plate electrodes proved capable of differentiating volumetric capacitance and buffer conductivity of sample arrays. This work suggests that large capacitive changes, for example, buffer volume and conductivity, are easily measured with the device. However, small capacitive changes are difficult to detect. Using microelectrodes enables a more sensitive approach to detect cell proliferation and death. Nevertheless, the sensitivity of the device to the small capacitive changes that would result from such activity of the cells remains a significant challenge. Further work is suggested to further enhance the system's sensitivity.

The overall achievement of the thesis is to present, using the scientific method, the process of design iteration necessary to build a new kind of biosensor, and to underline the challenges of designing a contactless cell-based sensor for toxicity assays. In particular, the major challenge appears to concern the interplay between the relation on the thickness of the insulating layer and the conductivity of the media. Future work will focus on generating more advanced computational models that consider the effect of the electrolytes on the sensitivity of the system.

Date of Award	20 Jun 2023
Original language	English
Awarding Institution	University of Bristol
Sponsors	CONACyT
Supervisor	Alan R Champneys (Supervisor), Janice Kiely (Supervisor), Richard Luxton (Supervisor) & Anja G Teschemacher (Supervisor)