A label-free immunosensor by controlled fabrication of monoclonal antibodies and gold nanoparticles inside the mesopores

A label-free immunosensor for the detection of α-fetoprotein (AFP) is proposed based on controlled fabrication of monoclonal antibodies of AFP (anti-AFP) and gold nanoparticles (GNPs) inside the pores of mesoporous silica (MPS). The silanol groups on the internal pore walls were grafted by aminopropyltriethoxyl silane, whereas the silanol groups on the external surface of MPS were blocked by trimethylchlorosilane (TMCS). Thus, anti-AFP and GNPs could be confined inside the mesopores of TMCS–MPS by the covalent linking with the amino groups. The prepared anti-AFP/GNPs/TMCS–MPS particles were used to modify glassy carbon electrode (GCE) to construct a label-free immunosensor. After incubating the sample AFP with the anti-AFP/GNPs/TMCS–MPS/GCE, the immunoconjugates were formed on the surface of GCE and the spatial block increased. Thus, the peak current decreased with increasing concentrations of AFP. GNPs inside the mesopores could promote the electron transportation through the pore channel. Under the optimal experimental conditions, the fabricated immunosensor could detect AFP in a linear range from 1.0 to 90 ng ml−1 with a detection limit of 0.2 ng ml−1 (3σ). It provided a novel alternative method for the label-free determination of other antigens.