Aptamer-based homogeneous protein detection using cucurbit[7]uril functionalized electrode

• A novel electrochemical strategy for protein detection has been established.
• The detection strategy relies on a homogeneous aptamer-binding assay format.
• Supramolecular principle is introduced into the procedure to improve sensitivity.
• The method displays excellent performance for the detection of osteopontin.

A new strategy for homogeneous protein detection is developed based on a cucurbit[7]uril (CB[7]) functionalized electrode. The analytical procedure consists of the binding of target protein to its aptamer in the test solution, followed by an exonuclease-catalyzed digestion of methylene blue (MB) tag labeled DNA oligonucleotides. Since CB[7] molecules immobilized on the electrode may efficiently capture the released MB-labeled nucleotides, the MB tags are concentrated to the electrode surface and subsequently yield highly sensitive electrochemical signal, which is related to the concentration of the target protein. The method combines the host–guest properties of CB[7] with the immobilization-free homogeneous assay, providing a powerful tool for protein detection. Taking the detection of osteopontin as an example, the proposed method can have a linear response to the target protein in a range from 50 to 500 ng mL−1 with a detection limit of 10.7 ng mL−1. It can also show high specificity and good reproducibility, and can be used directly for the assay of osteopontin in serum samples.

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