Gold nanorod probes for the detection of multiple pathogens

A simple and novel method to completely replace the cetyltrimethylammonium bromide (CTAB) bilayer on gold nanorods with amine groups provided by a biocompatible and water-soluble chemical, cystamine with a disulfide compound, was demonstrated. The use of various gold nanorod bioprobes with different aspect ratios, conjugated to anti-E.coli and anti-S. thyphimurium antibodies, was also investigated. The visible/NIR spectra of gold nanorods show a weak transverse plasmon band at 524 nm and a strong longitudinal plasmon (LP) band at 650 nm. The spectrum for CTAB in the as-prepared substrates show two intense bands, assigned to asymmetric stretching vibrations of C-CH₂ in the methylene chains. The results also show that the detection of E. coli either in small or large numbers can be detected by changes in the intensity and position of the LP bands.