Screening and evaluation of aptamers against somatostatin, and sandwich-like monitoring of somatostatin based on atomic force microscopy

•The selected aptamers against somatostatin (SST) were evaluated with their structures and functions, such as affinity or interaction.•Two aptamers with the similar sequence indicated much difference affinity and interaction against SST.•Two aptamer-based AFM aptasensors enable the sensing of SST.•The SST concentration could be monitored to use an interactive force as an index and Hill model.•The SST number can be estimated via a statistical analysis.

A sensing system was constructed to monitor the target peptide via two aptamer-based sensors pinching. First, aptamers against somatostatin (SST) were selected via the systematic evolution of ligands by exponential enrichment, and four aptamers were selected from a single-stranded DNA library. Their specificities to SST were evaluated via surface plasmon resonance and atomic force microscopy (AFM). Next, two aptamers with higher specificities to SST were used as aptamer-based sensors; one aptamer was modified with a chip, and the other was modified with a probe. Based on AFM system, the probe was surveyed on the chip in SST solutions, simultaneously measuring an interactive force. The label-free SST could be detected, and then the change in its concentration could be monitored at levels that ranged from 2 to 2000 nM. The interactive force of a single pair was approximately 45 pN, and the molecule number was associated with the interactive force. Therefore, we could firstly select the aptamers against somatostatin, and the sandwich-like monitoring system can be used to promote peptide sensor or monitoring system using an aptamer-based sensor.