Alkaline phosphatase labeled SERS active sandwich immunoassay for detection of Escherichia coli.Spectrochim Acta A Mol Biomol Spectrosc. 2018 Apr 05; 194:8-13.SA
In this study, a sandwich immunoassay method utilizing enzymatic activity of alkaline phosphatase (ALP) on 5-bromo-4-chloro-3-indolyl phosphate (BCIP) for Escherichia coli (E. coli) detection was developed using surface enhanced Raman spectroscopy (SERS). For this purpose, spherical magnetic gold coated core-shell nanoparticles (MNPs-Au) and rod shape gold nanoparticles (Au-NRs) were synthesized and modified for immunomagnetic separation (IMS) of E. coli from the solution. In order to specify the developed method to ALP activity, Au-NRs were labeled with this enzyme. After successful construction of the immunoassay, BCIP substrate was added to produce the SERS-active product; 5-bromo-4-chloro-3-indole (BCI). A good linearity (R2=0.992) was established between the specific SERS intensity of BCI at 600cm-1 and logarithmic E. coli concentration in the range of 1.7×101-1.7×106cfumL-1. LOD and LOQ values were also calculated and found to be 10cfumL-1 and 30cfumL-1, respectively.