Silver ions-regulated reliable and rapid detection technique of alkaline phosphatase based on surface-enhanced Raman spectroscopy

Abstract

The first appeal of clinical assay is always accurate and rapid. For alkaline phosphatase (ALP) monitoring in medical treatment, a rapid, reliable surface-enhanced Raman scattering (SERS) detection technique was designed based on controlled “hot spot” effect by the mediation of silver ions (Ag+). Consisting of functionalized Au nanoparticles (NPs), Ag+, and enzyme substrate 2-phospho-L-ascorbic acid triso-dium salt (AAP), the fabricated detection technique can achieve reliable clinical assay of ALP in human serum within several minutes. Herein, due to the coordination interaction of Ag+ and cyanogroup (-CN), Ag+ can coordinate with p-mercaptobenzonitrile (MBN) modified on the surface of Au NPs, leading the connection of adjacent Au NPs in a controllable manner to form chain structure, in which the SERS signal of MBN at 2228 cm-1 in the Raman silent region would be highly amplified; Under the enzymatic biocatalysis of ALP, AAP was turned into ascorbic acid (AA), AA can trigger the reduction of Ag+ into Ag0, resulting in a decrease in the concentration of Ag+, meanwhile, the decrease of SERS intensity of MBN was well-controlled and can be recognized with the increase amounts of ALP, based on this, the SERS detection technique of ALP was established. The limit of detection (LOD) for detection of ALP was as low as 1.23 pg/mL (0.005 U/L), along with ultrahigh stability, this SERS detection technique therefore is an important point-of-care candidate for reliable, efficacious, and highly sensitive detection of ALP.