Immobilization of Aptamers on Substrates

Aptamers are a new generation of receptors, composed of single-stranded DNA (ssDNA) or RNA that are selected in vitro by the Systematic Evolution of Ligands by EXponential Enrichment (SELEX). Selected aptamers are usually in the region of 35-100 nucleotides in length and have the ability to recognize different classes of targets (such as protein, toxin, drug, or cell) with high specificity and affinity. Despite having functions similar to that of antibodies, aptamers have several advantages in terms of selection and production, costs, stability, shelf life, modification, and oriented immobilization. Furthermore, unlike antibodies, aptamers can be reversibly denatured, which facilitates capture and release of target compounds in reusable applications. Notably, based on their nucleic acid composition, aptamers have the inherent ability to bind to their complementary sequence in addition to their cognate target, which can be exploited for immobilization or signaling strategies. Because of all these features, various applications using aptamers as biorecognition elements in biosensor design or in homogeneous assays have been reported in the literature. This chapter describes different aptamer immobilization chemistries used in the production of aptasensors, providing key examples of the most applied technologies. In addition, some recent diagnostic applications in relation to the immobilization method are reviewed. As the number of literature contributions on aptasensors is constantly expanding, this chapter highlights developments in aptasensors over a period between 2010 and mid-2017.