Title: Detection of pathogenic bacteria using bacteriophages and plasmonic nanoparticles by LSPR and SERS: A brief review

Abstract

Food and water borne diseases are among the most serious and costly public health concerns worldwide. According to WHO millions of deaths occur annually due to food and waterborne diseases mostly caused by pathogenic bacteria including Escherichia coli, Salmonella, Staphylococcus, and many others, even in developed countries - which is a very scary scenery. In addition, the number of antibiotic-resistant bacteria is rapidly increasing - has already raised above very dangerous levels - which is even much more frightening. Monitoring food and water quality has therefore been recognized as one of the most important priorities globally. Current pathogen detection methods include: (i) microbiological techniques (conventional culturing); (ii) nucleic-acid based (e.g., PCR and DNA hybridization using oligonucleotides as bio-recognition elements - bio-probes) and (iii) immunological (e.g., ELISA - using specific antibodies as bio-probes). Using bacteriophages as bio-probes alternative to antibodies and nucleic acids for bacterial detection is a very unique approach and that have been proposed rather recently. Bacteriophages are viruses which only infect bacteria, with excellent host selectivity. Bacteriophages are not only the most abundant biological entities but also probably also the most diverse ones. They may be very specific even at serotype levels, could be easily propagated therefore quite in expensive and have long-shelf life. Bacteriophages have been used for specific detection of target bacteria by using different bio-sensing platforms which are mainly treated in two categories: (i) using labels (including fluorescent, luminescent, enzymes, electrochemically active labels, etc.), (ii) label-free systems (QCM, SPR, Ellipsometer, Raman and Mass spectrometers, etc.). Almost all of technologies mentioned above have been applied for detection of pathogens by using bacteriophages with different extent and success. The challenging objective is to develop enhanced detection technologies with high levels of reliability, sensitivity, and selectivity with short assay times. In recent year due to the “size and shape-dependent” properties metallic, especially gold and silver nanoparticles have been extensively studied in wide variety of applications. Gold nanorods (GNRs) are rod-shape nanoparticles which could easily produced with different aspect ratios (dimensions) - therefore different plasmonic properties. Their unique optical and physical properties have allowed using them for development of bio-sensing platforms mainly as surface signal enhancers. Here we briefly review detection of pathogenic bacteria by using as selective bio-probes together with GNRs, by focusing LSPR and SERS techniques – using also our experiences in the field.