Preparation of TiO2 nanosheet-carbon nanotube composite as immobilization platform for both primary and secondary antibodies in electrochemical immunoassay

- TiO2 nanosheet-carbon nanotube composite was synthesized by hydrothermal method.
- The composite exhibits improved properties compared to the individuals.
- The composite is designed as electrode scaffold for immobilizing primary antibody.
- Secondary antibody and horseradish peroxidase are immobilized on the composite as a label.
- The tracing label exhibits great amplification effect for immunosensing.

TiO2 nanosheets (TNSs) were synthesized and deposited on multi-wall carbon nanotubes (MWCNTs) to form a nano-composite through a hydrothermal method, followed by the characterization with various spectroscopic and microscopic techniques. The TNS-MWCNT composite was then applied as not only an electrode scaffold to immobilize primary antibody, but also as a carrier to load secondary antibody and horseradish peroxidase (HRP). In both cases, bis(sulfosuccinimidyl) suberate sodium salt acted as an amino cross-linker to covalently bind the biomolecules on TNS-MWCNT composite through their surface primary amino groups. After the sandwich-type immunoreaction, HPR was quantitatively captured on the electrode surface via the binding between secondary antibody and antigen, and electrochemical response of the immunosensor was then amplified by a H2O2 mediated HRP catalytic reaction. Using α-Fetoprotein as a model analyte, a linear range between 0.005 and 320 ng mL−1 with a detection limit of 2.0 pg mL−1 was achieved by differential pulse voltammetry. The improved immunosensor performance could be attributed to the biocompatibility and high specific surface area of TNS, and excellent electrical conductivity of MWCNTs, which accelerated the electron transfer at the electrode surface.

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