Traditional drug screening technologies rely heavily on animal testing, which is not only expensive and time-consuming, but also raises many ethical issues. Also, most drug candidates fail during the different phases of drug testing. Therefore, developing a low-cost, rapid, and animal-free system to allow mass-screening of a drugs’ specificity and efficacy is the promising way to increase testing efficiency for novel drugs.

Since more than half of currently approved drugs target cell membranes, studying drug interactions with cell membranes is one of the key factors in understanding drug cytotoxicity and efficacy. The recently developed membrane-on-a-chip system, involving cell-derived supported lipid bilayers (SLBs) integrated with bioelectronic devices, is able to rapidly sense drug responses from cell membrane. This system eliminates the complexities and challenges of traditional testing systems, such as sterile cell-culture environments or physiological monitoring of animals. Also, quantification of drug responses with this system can be easily achieved by membrane quality analysis (i.e. electrochemical impedance spectroscopy (EIS)). Therefore, the membrane-on-a-chip system is a promising technology to advance next-generation drug discovery. Colleagues from our group previously demonstrated the detection of drug response with overexpressed transmembrane proteins with this systems and quantified the response with a model circuit. The key progress of this dissertation is sensing bioevents associated with naturally-expressed transmembrane proteins.

This dissertation also discusses on multiple aspects of the membrane-on-a-chip system, such as strategies for device design and fabrication, electrochemical characteristics of SLBs, noise reduction for accurate measurements, and applications for biomedical research and drug screening. First, the two issues (1. gold-ring marks; 2. delamination of sacrificial layer induced by bubble formation) caused by photolithography during microfabrication are optimised and discussed for achieving high productivity and stable performance of these organic devices. Then, the experimental data was combined with numerical simulations to explore the relationship between changes in SLB quality and impedance output, delving into a deeper understanding of the impedance profiles of devices with and without SLBs, as well as extracted parameters such as membrane resistance (R_m). This approach was employed to investigate the relationship between microelectrode area and sensor sensitivity with changes in SLB state, towards rational device design. We highlight the trend of electrode size (polymer volume) required for sensing bilayer presence as well as the dependence of electrode sensitivity on SLB capacitance and resistance. Lastly, I illustrate how the flexible approach of including electrode and transistor measurements to amalgamate characteristic impedance spectra of transistors overcoming the problem of low-frequency noise and errors seen with traditional EIS.

With a deeper understanding of the membrane-on-a-chip system, we further apply this technology to: detect SARS-CoV-2 viral entry and screen antibody efficacy to inhibit viral invasion, which is discussed in chapter 4; Study drug-induced blockage of voltage-gated calcium (CaV) ion channels on SLBs derived from neuroblastoma and primary cortical cells, which is discussed in chapter 5. In chapter 4, I demonstrate characteristic electrochemical impedance spectra of the early and late pathways of SARS-CoV-2 entry on SLBs derived from two cell lines: human lung epithelial Calu-3 cells and human embryonic kidney cells which overexpress the ACE2 receptor (HEK293-ACE2), respectively. The sensitivity of virus detection is further assessed by testing a range of viral particle concentrations; the detectable concentration reaching as low as ~10² virus pseudo particles (VPPs) per ml. We successfully apply this platform not only as a sensitive viral particle detector, but also as a drug-screening platform for screening antibodies that specifically target either ACE2 proteins on the host membrane or SARS-CoV-2 Spike proteins.

For the neuronal membrane application demonstrated in chapter 5, I first performed differentiation on SH-SY5Y neuroblastoma cells, and then form native SLBs from the SH-SY5Y cells before and after differentiation on microelectrode arrays. An upregulated dose response of blocking of naturally expressed CaV ion-channels after SH-SY5Y differentiation was successfully detected via EIS. Further, the same setup was adapted to the native SLBs derived from rat primary cortical cells for the first time. The response of CaV ion-channel blocking on rat cortical neuron SLBs is comparable to the response from SH-SY5Y SLBs with and without differentiation.

This dissertation demonstrates that this membrane-on-a-chip system is a rapid, ultra-sensitive, cell-free, and high-throughput platform to sense biological events, including specific interactions with endogenously expressed levels of membrane proteins. This could be an important contribution to the development of next-generation diagnostics and antibody/drug screening technologies for healthcare and biomedical research.