Lateral Flow-Electrochemiluminescent (LF-ECL) Test Strips and Portable Reader for Ultrasensitive Foodborne Pathogen Detection

Summary Abstract
Nanohmics proposes to continue its successful Phase I protect ins which electrochemiluminescence (ECL) from traditional
ruthenium trisbipyridine (Ru(bpy)3) in lateral flow (LF) test strips was used to detect as few as 18 Listeria monocytogenes
bacteria (25 cfu average). This LOD could improve to 1-2 cfu with the addition of a photomultiplier tube (PMT). LF strip
assays are known for being rapid, highly affordable, and facile onsite diagnostics, but generally lack sensitivity and may
miss detection of foodborne pathogens (false negative results) at low levels even in time-consuming enrichment cultures.
In some cases, LF strip developers have turned to fluorescence for added sensitivity. But, fluorescence has innate
autofluorescent background from the excitation of other biological materials in samples, thus limiting its sensitivity.
Although traditional chemiluminescence (CL) can be ultrasensitive due to its initial black background and high signal to
noise ratios (SNRs), CL is difficult to control spatially on a test strip and requires temporal delays to allow it to reach stable
equilibrium prior to measurement which limits reproducibility. However, ECL is simple to control by controlling the
working electrode voltage (only about 1.25V), thus enabling battery-operated handheld readers. ECL can also amplify or
accrue the signal over time each time the Ru(bpy)3 or quantum dot (Qdot) redox “wheel” is turned electrically to release
another red photon, thus giving sensitivity comparable to radioisotopic methods when the ECL signal is integrated over
time. Newer Qdot-based ECL techniques promise as much as a million-fold increase in ECL over Ru(bpy)3-antibody or
aptamer tags as well. Thus, Nanohmics proposes to build on its successful Phase I effort with Listeria and Ru(bpy)3, by
expanding to the other three major foodborne bacterial species (C. jejuni, Shiga toxin producing E. coli O157:H7 and S.
enterica serovar Typhimurium) and inactivated enteroviruses in Phase II and using Ru(bpy)3 and/or Qdots for ECL.
Titration, LOD and cross-reactivity results from the four major foodborne bacterial diseases will be validated by a third
party laboratory (Food Safety Net Services) in Phase II and licensing can be initialized via Nanohmics food safety consultant.

Grant Number: 2R44CK000679-02A1
NIH Institute/Center: ALLCDC
Principal Investigator: John Bruno