Electrochemical detection of microRNAs for cancer diagnosis

Abstract

Cancer continues to grow globally, exerting serious financial and emotional strain on individuals, families, associations and health systems. Early detection is crucial in order to control the spread of the disease and improve chances of survival. Despite the significant intellectual and financial efforts worldwide, there are currently no blood based biomarkers that are suitable for the non-invasive early detection of cancer. MicroRNAs/miRNAs are a family of non-protein-coding small RNAs which regulate the expression of nearly one third of all human genes. Over the past decade, significant evidence has emerged showing that miRNAs and modulation of their levels in human body are involved in the pathogenesis of cancer at its early stages.
The main consideration when selecting methods of detection for miRNAs is the requirement for high-sensitivity and selectivity due to their low concentrations in blood. This thesis investigates a new method of electrochemical detection which is distinctive due to its sensitivity together with its simple, rapid and reliable design. The first experimental study investigates the role of artificial oligonucleotide probes for selective recognition of miRNAs. Upon using Peptide Nucleic Acid (PNA) probes, highly-sensitive and direct electrochemical detection of a pancreatic cancer-specific miRNA has been achieved with no additional labelling steps. The second study examines the adoption of magnetic beads for separation of target miRNAs from complex solutions (e.g. blood). This strategy addresses the major problem of nonspecific interactions that arises upon direct subjection of sensor surfaces to complex solutions. The final study concentrates on the use of redox active self-assembled monolayers (SAMs) on electrode surface for direct capacitive-based detection of miRNAs. Such methodology eliminates the need for pre-doping of the measurement’s solution or labelling of target and is highly desirable characteristic for a point-of-care device to be used for the analysis of clinical samples.
Together, this thesis aims to serve as a potential guidance for overcoming the shortcomings of the current miRNA sensing, add value to the development of oligonucleotide-based biosensors for detection of circulating miRNA and hopefully enable the early detection of cancer state.

Date of Award	22 Jul 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Pedro Estrela (Supervisor), Christopher Frost (Supervisor) & Mark Lindsay (Supervisor)