Abstract

Analysis of peripheral blood as a source of, tumour-shed, cancer biomarkers has been fostered with the concept of liquid biopsy. Circulating aberrant amounts of non-coding microRNA (miRNA, 18-25 nucleotides) have been shown to be clinically associated with cancer. Data from clinical studies and meta-analysis demonstrated that altered expression of microRNAs in plasma to be associated with prostate cancer (PCa) aggressiveness, distant metastasis, biochemical recurrence and prognosis. The high chemical stability of miRNAs in body fluids makes them powerful biomarkers present at levels suitable for testing in patient samples.
The idea of using light to develop biosensors is recent and these sensors have the advantage that the analytical signal is only triggered by light, so the signal and background can be clearly distinguished by turning on/off the light source.1 The use of a photosensitiser instead of an enzyme has several advantages: higher S/N ratio; on-off control of sensing by light switching; chemical and thermal stability and lower price.
In INFORM a sandwich assay is used to detect miRNAs that are clinically relevant in PCa. The capture strand is immobilized on a screen-printed gold electrode and the detection strand is labeled with a photosensitiser, which produces singlet oxygen, 1O2, upon excitation with light. The 1O2 produce is quantified using chronoamperometry and it is proportional to the concentration of miRNA in solution. The various strategies adopted and the results achieved for individual and simultaneous detection of three (3) miRNAs will be discussed.2,3
(1)    Trashin et al. Nat. Commun. 2017, 8 (1), 1–10
(2)    Campos et al. Submitted.
(3)    Shanmugam et al., In Preparation. 2021.