Controlled fabrication of gold nanobipyramids/polypyrrole for shell-isolated nanoparticle-enhanced Raman spectroscopy to detect γ-aminobutyric acid.

Shell-isolated nanoparticle-enhanced Raman Spectroscopy (SHINERS) has been a non-destructive, highly sensitive, specific and powerful sensing method. Detection of γ-aminobutyric acid (GABA) and glutamate, main neurotransmitters in the human brain, is important to diagnosis the neurological disorder. The purpose of this study is preparing a simple, rapid and inexpensive fabrication of Au nanobipyramids/polymer core/shell as a SHINERS-based biosensor to detect different neurotransmitters such as GABA and glutamate with high sensitivity and specificity. Au nanobipyramids/polymer core/shell was fabricated by using two steps process. In the first Au nanobipyramids with longitude and latitude axial of about 100 nm and 10 nm, respectively, was prepared based on the chemical reduction of Au ions by using sodium borohydride as a reducing agent. Then a thin layer of polypyrrole was used for decorating the Au nanobipyramids by using direct polymerization in the presence of Au nanobipyramids. The sensor composed Au nanobipyramids with a thin layer of polypyrrole that could measure GABA within a wide range of concentrations in the presence of human serum. And this sensor was used for direct monitoring of GABA and glutamate. The proposed biosensor can be applied to monitor the level of neurotransmitters accurately for the diagnosis of various neurological disorders with optical signal enhancement.