Detection of VEGF165 Using an Aptamer Affinity Probe in Microchip Capillary Electrophoresis

Aptamers, like antibodies, have high molecular recognition specificity and selectivity. Coupled with microfluidic devices, apatamers and target-aptamer complexes can be rapidly separated while only a small sample volume is required. Trace protein detection using aptamer probes on a microchip platform was demonstrated using vascular endothelial growth factor 165 (VEGF165) and a selective aptamer probe as a model system. The fluorescently labeled aptamer was separated from the VEGF165-aptamer complex in 10 s. The equilibrium dissociation constant of the complex was determined to be 8.0 nM using frontal analysis on the microchip. Two calibration curves were constructed with a detection limit of 1.0 nM VEGF165 using pinched and gated injections. The blood plasma effects on the microchip electrophoretic separation and VEGF165-aptamer complex formation were investigated using rat blood plasma. Results demonstrate the power of microchip capillary electrophoresis in terms of assay speed, low reagent consumption and high separation efficiency. However, they also indicate the necessity of further improvements in the detection limit and/or the pretreatment of the plasma sample when measured by microchip CE.