Aptasensor designed via the stochastic tunneling-basin hopping method for biosensing of vascular endothelial growth factor.

The Systematic Evolution Ligands by Exponential Enrichment (SELEX) is common used for selection of high affinity single-stranded DNA (ssDNA) aptamer with target protein. However, we do not know what the most stable configuration of the selected aptamer bound with target protein is. Therefore, a systematic search process using the stochastic tunneling-basin hopping (STUN-BH) method is proposed to find the most stable configuration of the ssDNA aptamer specific for vascular endothelial growth factor (VEGF) capture (AptVEGF; 5'-TGTGGGGGTGGACGGGCCGGGTAGA-3'). After the most stable configuration was obtained by the STUN-BH method, molecular dynamics (MD) simulation was carried out to investigate the thermal stability of AptVEGF/VEGF at 300 K in both vacuum and water. All molecular simulations were conducted with the large-scale atomic/molecular massively parallel simulator (LAMMPS), and the AMBER99SB force field was used to describe the atomic interactions for the current AptVEGF/VEGF system. The three most stable AptVEGF/VEGF configurations obtained by the STUN-BH method indicated that AptVEGF residues exhibit greater affinity for VEGF surface loop fragments as compared with surface alpha helix and beta sheet fragments. Results indicated that after the first AptVEGF (AptVEGF I) occupies most of the VEGF loop fragment, the second AptVEGF (AptVEGF II) is adsorbed by the rest of the VEGF loop fragment and the VEGF Chain B beta sheet fragment, resulting in a 24.8% reduction in binding strength as compared to that of AptVEGF I. Furthermore, when AptVEGF I and AptVEGF II chains were stably adsorbed by VEGF, the third AptVEGF (AptVEGF III) chain can only partially attach to VEGF, as confirmed by real AptVEGF-VEGF binding experiments. Lastly, we demonstrated that the aptasensor constructed according to MD simulation is highly sensitive for VEGF with a linear detection range of 10 pg/mL-10 ng/mL.