Label-Free Optical Detection of Protein Antibody–Antigen Interaction on Au Capped Porous Anodic Alumina Layer Chip

Abstract

The interaction of protein antibody and antigen will lead to change in the mass, electrical charge, or optical properties of the immobilized protein layer, which can be detected by microgrativimetric, potentiometric, amperometric or optical transducers. For this reason, we developed a new localized surface plasmon resonance (LSPR) coupled with interferometry based label-free optical biosensor in connection with a Au capped porous anodic alumina (PAA) layer chip. We could observe the formations of the self-assembled monolayer (SAM)/protein A/C-reactive protein (CRP) antibody/CRP antigen on the Au capped PAA layer chip surface by means of LSPR and interferometric characteristics. In the presence of CRP antigen, the change of the relative reflected intensity (RRI) in the interferometric pattern and a significant bathochromic shift were observed. The fabrication of uniformed Au capped oxide nanostructure is the primary advantage of our chip. It is known that biomolecular interaction which contributed to the change in the refractive index depends on the absorbance intensity change and wavelength shift. Using our Au capped PAA layer chip, one can measure both the information in one single event using a single optical fiber, which is the great additional advantage over SPR.