A highly sensitive VEGF photoelectrochemical biosensor fabricated by assembly of aptamer bridged DNA networks.

We developed a novel "signal-off" photoelectrochemical (PEC) aptasensor based on an aptamer bridged DNA network structure for the sensitive detection of vascular endothelial growth factor (VEGF), using g-CN as photoactive material. The DNA network provides an excellent platform for the immobilization of methylene blue (MB), which can facilitate the electron transport through the DNA helix structure and suppress the recombination of electron-hole pairs generated by g-CN. In the presence of the target VEGF, the DNA network can be destroyed adequately by the recognition between VEGF and the aptamer, resulting in the release of MB. Therefore, the originally enhanced electron transfer process could be inhibited, leading to a remarkable decrease of the photocurrent. A good linear relationship between the PEC signal and the logarithm of VEGF concentration over the range of 100fM to 10nM with a detection limit of 30 fM can be obtained. Our concept can be easily extended to develop aptasensors for the sensitive detection of different targets by triggering the release of the payloads from their corresponding aptamer bridged DNA networks.