Biosensors based on self-assembled monolayers (SAMs) of oligonucleotide aptamers have been developed in recent years as an alternative approach to antibody-based biosensors and are able to selectively target analytes with high specificity and reusability. Aptamers are in most cases composed of random sequences of nucleotides obtained to bind a specific analyte via the systematic evolution of ligands by exponential enrichment (SELEX). Because of several advantages over proteins such as longer shelf life, low batch to batch variation etc. aptasensors have the potential to overcome the shortcomings of biosensors based on enzymes or antibodies. For the application in biosensors, rational truncation of an aptamer has been shown to reduce the steric hindrance for the charge transfer involved in electrochemical sensing and increases the space for the analyte to bind. Hence truncated, shorter sequences are preferred for the design of electrochemical biosensing devices. For example, truncated C9t single-stranded DNA (ss-DNA) aptamer was employed in a recently developed biosensor to detect the spike glycoprotein (S protein) of the SARS-CoV-2 Omicron variant. For fabrication of a gold based aptasensor, the aptamers which act as receptors are typically chemisorbed to the interface by Au-S bonds. Factors such as the stability of the receptors, their accessibility for the analyte, and the number of receptors per unit area are important for the sensor performance and the efficiency in detecting small analyte concentrations.