DNA aptamer-based approaches for detection of multiple prostate cancer biomarkers

Prostate cancer (PCa) is the most common malignancy in men worldwide. The need for its early diagnosis with a high sensitivity and accuracy to preclude worsening of PCa has led to increasing work on the detection of multiple biomarkers for PCa. One approach relies on the use of DNA aptamers raised against a range of PCa biomarkers. DNA aptamers, which bind with high affinity and specificity to target markers, are promising synthetic biorecognition molecules that can be used for the development of multiplexed biosensors. DNA aptamers have a number of advantages over antibodies, in particular with regards to their lower cost, easy manipulation and potential for controlled chemical attachment to electrodes. We report on the development of novel techniques to detect different biomarkers for PCa using aptamers. In this study various detection methods are being investigated, namely electrochemical impedance spectroscopy, amperometry and localized surface plasmon resonance techniques (LSPR). Novel surface modification strategies are also being developed, e.g. impedimetric detection of prostate specific antigen (PSA) with aptamers together with a thiol-terminated sulfo-betaine, which may allow detection of PSA levels down to 1 ng/mL. The sulfo-betaine derivative also prevents any significant non-specific binding of control proteins such as human serum albumin. Additionally, in order to increase the sensitivity of our PSA aptasensor, a novel approach is being developed where a PSA-binding peptide conjugated with gold nanoparticles is used in conjunction with a DNA aptamer to perform a sandwich assay using the LSPR technique. As part of the search for enhanced PCa diagnosis, the detection of the biomarker α-methylacyl-CoA racemase (AMACR; P504S) is also being investigated using DNA aptamers. AMACR levels are consistently increased in early PCa, and antibody staining of biopsy samples is currently used for diagnosis. The best aptamer sequence for an on-surface detection of the AMACR protein has been identified using surface plasmon resonance (SPR) and impedance spectroscopy techniques.
The studies undertaken demonstrate the potential use of DNA aptamers for the development of a range of multiplexed detection platforms for early and accurate PCa diagnosis.