Optical methods for monitoring probe hybridization using
nanomaterials vary in complexity. For example, a
sensor for E. coli O157:H7 and Salmonella has been reported
based on the immobilization of aptamers onto the
surface of gold nanoparticles (Pieta, Szczerba,
Dobroczynska, & Grabas, 2013; Wu et al., 2012). In one
example, upon binding of the pathogen target there is a
visible change of the nanobeads from red to blue. The
sensor is claimed to be 100% selective in detecting pathogens
although the sensitivity is relatively low with a detection
limit of 4 log cfu/g