Nucleic acid-based aptasensors for cancer diagnostics - An insight into immobilisation strategies

Whilst antibodies remain the most popular and trusted choice for molecular recognition, they may still pose challenges for biosensing applications due to their high cost, low reproducibility and large size. One long championed alternative to antibodies are nucleic acid aptamers. Nucleic acid aptamers are single-stranded DNA or RNA sequences that can bind to a target with high affinity and specificity. Nucleic acid aptamers, due to their varied advantages, have been gaining significant importance in both diagnostic and theranostic applications. Among various diseases, early diagnosis of cancer is one of the biggest concerns for patients and healthcare professionals worldwide. For the case of cancer, it is crucial to be able to deliver treatment whilst monitoring therapy response in real time. This is required in order to prevent over- or under-dosing the patients whilst treatment occurs. One of the most commonly used techniques for cancer diagnosis is to detect biomarkers (cancer-related proteins, small molecules and cancer cells) found in body fluids specific for a particular cancer type. In this chapter, we present a discussion on the use of aptamer-based biosensors (termed as “aptasensors”) for cancer diagnosis. The development of aptamer-based biosensor devices is an interdisciplinary field and relies on very distinct aspects such as characterisation of bio-recognition probes with their respective analytes, immobilisation onto electrode surfaces, development of anti-fouling surface chemistries, sensor design and fabrication and microfluidics. Special attention is given to different types of surface chemistry used for the development of simple, sensitive and cost-effective aptasensors. Utilisation of aptamers is an encouraging tool for the development of point-of-care (PoC) biosensors for the detection of different types of cancer. In the view of unparalleled merits of aptamers, recent achievements and future perspectives of the applications of aptamers are also discussed.