Surface Modification for Protein and DNA Immobilization onto GMR Biosensor

Giant magnetoresistance (GMR) biosensor with 20 nm SiO ₂ on surface was successfully modified by 3-aminopropyltriethoxy silane (APTES) and glutaraldehyde (Glu). The resultant functionalized surface with terminal aldehyde groups was able to efficiently capture Interleukin-6 (IL-6) antibody and amine modified DNA (deoxyribonucleic acid) oligonucleotide. The immobilized IL-6 antibody could bind to IL-6 antigen, and fluorescence sandwich assay was demonstrated. The immobilized DNA could also hybridize with complementary DNA oligonucleotide. Streptavidin labeled magnetic nanoparticles with a diameter of 30 nm were both successfully bound to IL-6 antibody and DNA immobilized GMR biosensors after their respective sandwich binding and complementary hybridization. This APTES-Glu modification method could be also applicable to other surface for protein and DNA microarrays.