Self-templated formation of aptamer-functionalized copper oxide nanorods with intrinsic peroxidase catalytic activity for protein and tumor cell detection

We have synthesized aptamer-functionalized copper nanoparticles (Apt-Cu NPs) using simple ascorbate-mediated reduction of Cu(II) ions in Apt-T_n templates comprising an aptamer (Apt) sequence with a poly(dT) motif at both the 3′- and 5′-termini. The as-prepared Apt-Cu NPs underwent rapid oxidation to Apt-T_n-CuO/Cu₂O NPs. The CuO/Cu₂O NPs tended to have rod-like shapes when the Apt-T_n templates had long poly(dT) units (n > 30). Interestingly, the as-formed Apt-T_n-CuO/Cu₂O NPs exhibited intrinsic peroxidase-like activity for the H₂O₂-mediated oxidation of Amplex Red (AR) to fluorescent resorufin. The catalytic activity of thrombin binding aptamer-templated CuO/Cu₂O NPs (TBA-T_n-CuO/Cu₂O NPs) was significantly suppressed after the specific binding of thrombin to the aptamer units on the particles' surfaces. The H₂O₂/AR-TBA-T_n-CuO/Cu₂O NP probe provided a limit of detection (LOD) of thrombin in serum samples of 0.5 nM. Using Mucin1 binding aptamer-templated CuO/Cu₂O NPs (Apt_MUC1-T₃₀-CuO/Cu₂O NPs), we applied this sensing platform to the detection of Mucin1-overexpressing tumor cells (LOD: ca. 100 cells). This study suggests that the Apt-T_n can be used as a universal template for preparation of enzyme-like CuO/Cu₂O NPs for detection of proteins and labeling of tumor cells when using appropriate aptamers.