Engineering the bio-nano interface for enhanced biosensing applications

Thesis

Disease diagnostics can take many forms, from clinical diagnostics to surveillance tests. The use of diagnostic tests is critical for initiating appropriate treatment regimens and implementing non-pharmaceutical interventions to manage disease outbreaks. Traditional biochemical diagnostic tests require specialist equipment and reagents, and trained personnel to perform the tests. Centralised laboratories are therefore required to perform and report the results of diagnostic tests. However, there is a growing shift towards decentralised healthcare systems, where diagnostic tests can be performed at the point-of-need. The point-of-need can vary between use cases, and may include a non-traditional healthcare setting, such as a patient’s home. Lateral flow immunoassays (LFIAs) are paper-based diagnostic tests that are suitable and appropriate for use at the point-of-need. LFIAs were widely employed during the Covid‑19 pandemic to diagnose and monitor disease transmission. However, LFIAs have been widely used commercially since the 1980s, where they were developed to detect pregnancy from urine samples. Whilst LFIAs offer several advantages over traditional laboratory-based diagnostic tests, several shortcomings remain. The work presented in this thesis aims to address some of the shortcomings of LFIAs through the development of platform technologies that can be readily translated to detect emerging threats.

Stability to elevated temperature and humidity is addressed through the implementation of affibody-based affinity agents, using industry-standard LFIA manufacturing processes to reduce barriers to translation.

Analytical sensitivity is improved through the use of coupled nanoparticle networks, increasing the number of nanoparticles immobilised in the test region. This approach makes use of traditional LFIA formats and operating steps, enabling integration into existing LFIA architectures.

The robustness of developed LFIAs is modulated through engineering of the interface between nanoparticles and biological samples, reducing the variability in LFIA performance observed between patient samples.

The time-to-develop LFIA is addressed, focusing on the appropriate selection of affinity agent pairs. A high-throughput platform is developed, aiming to aid the selection of affinity agents in a format more closely resembling the final LFIA format.

Overall, this work aims to address some of the performance barriers associated with existing LFIAs, enabling appropriate implementation of LFIAs for the early detection of disease at the point‑of-need.

Authors: Sadler, CJ

• DOI: 10.5287/ora-b78kjnepk
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: proteins; immunoassays; lateral flow immunoassays; rapid diagnostic test; nanoparticles
• Subjects: Proteins; Metal nanoparticles; Immunoassay; Point-of-care testing