Porphyrin-based covalent organic framework as bioplatfrom for detection of vascular endothelial growth factor 165 through fluorescence resonance energy transfer.

A fluorescent aptasensor based on porphyrin-based covalent organic framework (p-COF) and carbon dots (CDs) was constructed for detecting vascular endothelial growth factor 165 (VEGF) and for imaging of the breast cancer cell line Michigan cancer foundation-7 (MCF-7). CDs synthesized with strong photoluminescence at λ∼380 nm were used as donors to label the VEGF-targeted aptamers (Apt/CDs). Additionally, the p-COF nanostructure comprised rich functional groups of CN on the surface and π-stacking planar nanostructure, resulting in the CDs adsorption via weakly π-π stacking, hydrogen bond and the Van der Waals force. Thereby, the fluorescence resonance energy transfer (FRET) occurred due to the close distance between the p-COF network and CDs, leading to the quenching of the fluorescence feature of CDs and p-COF. In the presence of VEGF, the G-quadruplex was formed via the specific binding between VEGF and aptamer. It impelled that the release of partial VEGF-Apt/CDs complex, affording the fluorescence recovery of the sensing system to some extent. Consequently, the proposed Apt/CDs/p-COF fluorescence biosensor offered excellent analytical performances for the VEGF detection, displaying a detection limit of 20.9 fg mL within a wide linear range of the VEGF concentration of 1.0 pg mL-100 ng mL. The developed fluorescence biosensor was also used to determine VEGF-overexpressed in MCF-7 cancer cells. Thereby, the present work can greatly widen the application of COFs in the development of aptasensors and cancer diagnosis.