Plasmonic enhancement in lateral flow sensors for improved sensing of E. coli O157:H7

• Published in: Biosensors & bioelectronics 2019-02, Vol.126, p.324-331
• Main Authors: Ren, Wen, Ballou, Dexter R., FitzGerald, Ryan, Irudayaraj, Joseph
• Format: Article
• Language: English
• Subjects: biosensors; colorimetry; E. coli O157:H7; encapsulation; Escherichia coli O157; Gold nanoparticle aggregation, rapid detection; immunoassays; Lateral flow sensor; Liposome; liquids; microbial detection; nanogold; Plasmonic enhancement; polyethyleneimine; rapid methods; translation (genetics)
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2018.10.066

We propose a plasmonic enhanced lateral flow sensor (pLFS) concept with an enhanced colorimetric signal by utilizing liposome encapsulating reagent to trigger the aggregation of gold nanoparticles (GNPs). Our signal enhancement strategy incorporates the simplicity of lateral flow immunoassays (LFIA) utilizing plasmonic enhancement. The conceptualized hybrid pLFS for onsite rapid detection of pathogens in low numbers in a user friendly format requiring simple steps is the first step in the translation of plasmonic enhancement sensing to a practical regime. The pLFS was carried out with a biotinylated liposome label ruptured to release branched polyethylenimine (BPEI) to trigger the aggregation of GNPs for colorimetric signal generation. BPEI has multiple amino groups and more positive charges in PBS buffer, therefore few of the BPEI groups could induce the aggregation of GNPs, resulting in an enhanced colorimetric signal to detect E. coli O157:H7. Compared with the reported conventional LFIA, the proposed pLFS demonstrated more than 1000-fold improvement in sensitivity. The pLFS could detect as low as 100 CFU/ml of E. coli O157:H7 in buffer and 600 CFU/ml E. coli O157:H7 in liquid food systems. In this work we report on a plasmonic enhancement-based lateral flow sensor (pLFS) for detecting pathogens. Based on colorimetric signal, the proposed pLFS demonstrated a greatly improved detection sensitivity down to 100 CFU/ml with E. coli O157:H7 chosen as target, compared to that from conventional lateral flow immunoassay methods. Furthermore, the detection capability of the pLFS was investigated with cranberry juice, and as low as 600 CFU/ml of the pathogen could be recognized. Instead of color generating enzymatic reaction, we introduced liposomes to label the captured target bacteria wherein the branched polyethylenimine released from the liposomes triggered the aggregation of GNP monomers. The GNP aggregates formed by this process in the lateral flow strips provided an intense color which is more sensitive and robust compared to the conventional lateral flow systems in the market. [Display omitted]