Plasmonic and Electrostatic Interactions Enable Uniformly Enhanced Liquid Bacterial Surface-Enhanced Raman Scattering (SERS)

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a promising cellular identification and drug susceptibility testing platform, provided it can be performed in a controlled liquid environment that maintains cell viability. We investigate bacterial liquid-SERS, studying plasmonic and electrostatic interactions between gold nanorods and bacteria that enable uniformly enhanced SERS. We synthesize five nanorod sizes with longitudinal plasmon resonances ranging from 670 to 860 nm and characterize SERS signatures of Gram-negative Escherichia coli and Serratia marcescens and Gram-positive Staphylococcus aureus and Staphylococcus epidermidis bacteria in water. Varying the concentration of bacteria and nanorods, we achieve large-area SERS enhancement that is independent of nanorod resonance and bacteria type; however, bacteria with higher surface charge density exhibit significantly higher SERS signal. Using cryo-electron microscopy and zeta potential measurements, we show that the higher signal results from attraction between positively charged nanorods and negatively charged bacteria. Our robust liquid-SERS measurements provide a foundation for bacterial identification and drug testing in biological fluids.

Rapid, Label-Free Prediction of Antibiotic Resistance in Salmonella typhimurium by Surface-Enhanced Raman Spectroscopy

“…Thus, in a complex system, such as a bacterial cell, SERS signals carry information about the mixture of inherent biomolecules [40][41][42][43], which in turn gives birth to a wholefingerprint spectrum of a whole cell. Therefore, as a laser beam penetrated through a sample of bacteria and colloidal AuNPs, it could produce an identifiable Raman spectrum with high sensitivity to provide information based on whole-cell molecular vibrations.…”

General Background of SERS Sensing and Perspectives on Polymer‐Supported Plasmon‐Active Multiscale and Hierarchical Sensor Particles

“…[ 41–42 ] Thus, Raman spectroscopy became an important tool for biomedical, biochemical, and cell biological investigation. [ 43–45 ] The schematics of the basic principles of IR, UV–visible, and Raman spectroscopy are shown in Figure .…”

Nanobiotechnology enabled approaches for wastewater based epidemiology

“…Liquid SERS has been quite effective for detection of both Gram negative ( Escherichia coli and Serratia marcescens ) and Gram positive ( Staphylococcus aureus and Staphylococcus epidermidis ) bacteria using Au nanorod probes ( Fig. 3 A) [ 38 ]. The use of SERS reporter molecules, such as malachite green isothiocyanate (MGITC) or 4-(1H-pyrazol-4-yl)-pyridine (PPY), is often done to tag target molecules with a unique label [ 37 ].…”

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Fig. 3 (A) Detection of bacteria using a liquid SERS platform (Reprinted with permission from [ 38 ]); (B) Illustration showing the detection of the protein biomarker, neuron specific enolase (NSE) in blood plasma using a paper based lateral flow strip (PLFS) immunoassay (Reprinted with permission from [ 45 ]); (C) a microfluidic platform for the capture of avian influenza A viruses from clinical samples and rapid label-free SERS identification (Reprinted with permission from [ 47 ]); (D) The captured viruses on the chip are (i) immunostained, then (ii) propagated via cell culture and are finally (iii) genome sequenced for identification of subtypes (Reprinted with permission from [ 47 ]); (E) Application of a SERS based lateral flow immunoassay (LFIA) for detection of Influenza A H1N1 virus and human adenovirus (Reprinted with permission from [ 46 ]).

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