Abstract
A potential confounding factor in the development and evaluation of biosensors is the diverse nature of the disciplines involved. Biosensor technology involves electrochemistry, microbiology, chemical synthesis, and engineering, among many other disciplines. Biological systems, due to non-homogeneous distribution, are already imprecise compared with other systems, especially food based systems. Inadequate knowledge of the techniques to moderate this leads to ineffective evaluation strategies and potentially halting the pursuit of excellent technology that was merely poorly evaluated. This research was undertaken to evaluate the effect culture age had on the capture efficiency of the electrically active magnetic nanoparticles (EAMNP) using culture as the evaluation tool. The age of culture used for immunomagnetic separation (IMS) over all the experiments was 6 to 18 hours. Ideal culture age range for evaluating biosensors is 4 to 10 hours according to the growth curve for E. coli O157: H7 in trypticase soy broth. This is supported by the statistically significant difference among organisms in groups from 3 to 10 hours old compared with those grouped from 11 to 18 and >19 hours old (α = 0.05, p = 0.001 and p = 0.014 respectively). The two older categories were not different from each other. The capture efficiency in all biosensor analysis will vary less than when culture of only viable cells is the diagnostic tool. This allows a true evaluation of the consistency and accuracy of the method, less hindered by the variation in the ability to culture the organism.
Highlights
Immunomagnetic separation (IMS) is a rapid method for extracting and concentrating a target analyte from its sample matrix
E. coli O157:H7 strains, E. coli non-H7 strains and non-E. coli bacterial strains were obtained from the STEC Center collection at Michigan State University (MSU) (Shannon Manning, MPH, PhD), the Nano-Biosensors Laboratory at MSU (Evangelyn Alocilja, PhD), Neogen Inc
A 1 mL aliquot of the liquid culture was transferred to a new vial of broth and stored at 37 ̊C for up to 6 days. This culture was used to inoculate a new vial of broth with 1 mL of inoculum 10 to 24 h before each experiment to produce fresh bacterial cells which were serially diluted in 0.1% (w/v) peptone water (Fluka-Biochemika, Switzerland) prior to their use in the IMS procedure
Summary
Immunomagnetic separation (IMS) is a rapid method for extracting and concentrating a target analyte from its sample matrix. This is imperative due to the high level of interference the matrix of a food has on any diagnostic test [1]. Filtration, or capture of target on an immuno-functionalized surface, the IMS is simpler, and generally results in higher capture efficiency due to the greater surface area available for target binding [2] [14]. This is especially true of nano-sized particles. The surface chemistry of nano-sized particles such as surface tension, magnetization and sheer volume of surface area improves the amount of functionalized space for reaction to occur and improves the capture ability and longevity of the resultant IMS particles [2] [14]
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