Carboxyl-functionalized graphene oxide composites as SPR biosensors with enhanced sensitivity for immunoaffinity detection

- Covalently linked biocompatible GO-COOH composites are utilized in SPR-based immunoaffinity biosensors.
- The affinity binding value of the Au/GO-COOH chip was up to ~5.15 times that of the Au/GO chip.
- The detection limit of the Au/GO-COOH chip is 0.01 pg/ml, with a correlation coefficient of 0.973 at linear range of 0.01-100 pg/ml.

This work demonstrates the excellent potential of carboxyl-functionalized graphene oxide (GO-COOH) composites to form biocompatible surfaces on sensing films for use in surface plasmon resonance (SPR)-based immunoaffinity biosensors. Carboxyl-functionalization of graphene carbon can modulate its visible spectrum, and can therefore be used to improve and control the plasmonic coupling mechanism. The binding properties of the molecules between a sensing film and a protein were elucidated at various flow rates of those molecules. The bio-specific binding interaction among the molecules was investigated by performing an antigen and antibody affinity immunoassay. The results thus obtained revealed that the overall affinity binding value, KA, of the Au/GO-COOH chip can be significantly enhanced by up to ∼5.15 times that of the Au/GO chip. With respect to the shifts of the SPR angles of the chips, the affinity immunoassay interaction at a BSA concentration of 1 μg/ml for an Au/GO-COOH chip, an Au/GO chip and a traditional SPR chip are 35.5 m°, 9.128 m° and 8.816 m°, respectively. The enhancement of the antigen-antibody interaction of the Au/GO-COOH chip cause this chip to become four times as sensitive to the SPR angle shift and to have the lowest antibody detection limit of 0.01 pg/ml. These results indicate the potential of the chip in detecting specific proteins, and the development of real-time in vivo blood analysis and diagnosis based on cancer tumor markers.