Escherichia coli Enumeration in a Capillary-Driven Microfluidic Chip with SERS

Abstract

Pathogen detection is still a challenging issue for public health, especially in food products. A selective preconcentration step is also necessary if the target pathogen concentration is very low or if the sample volume is limited in the analysis. Plate counting (24–48 h) methods should be replaced by novel biosensor systems as an alternative reliable pathogen detection technique. The usage of a capillary-driven microfluidic chip is an alternative method for pathogen detection, with the combination of surface-enhanced Raman scattering (SERS) measurements. Here, we constructed microchambers with capillary microchannels to provide nanoparticle–pathogen transportation from one chamber to the other. Escherichia coli (E. coli) was selected as a model pathogen and specific antibody-modified magnetic nanoparticles (MNPs) as a capture probe in a complex milk matrix. MNPs that captured E. coli were transferred in a capillary-driven microfluidic chip consisting of four chambers, and 4-aminothiophenol (4-ATP)-labelled gold nanorods (Au NRs) were used as the Raman probe in the capillary-driven microfluidic chip. The MNPs provided immunomagnetic (IMS) separation and preconcentration of analytes from the sample matrix and then, 4-ATP-labelled Au NRs provided an SERS response by forming sandwich immunoassay structures in the last chamber of the capillary-driven microfluidic chip. The developed SERS-based method could detect 101–107 cfu/mL of E. coli with the total analysis time of less than 60 min. Selectivity of the developed method was also tested by using Salmonella Enteritidis (S. Enteritidis) and Staphylococcus aureus (S. aureus) as analytes, and very weak signals were observed.

Recent progress of microfluidic sample preparation techniques

“…The majority of microfluidic MAE is implemented in the form of MSPE based on magnetic particles. For example, Dogan et al [45] extracted E. coli from bacteria-spiked milk by specific antibody-modified magnetic nanoparticles, and transported the magnetic immunocomplexes to the SERS detection microchamber by moving the external magnet. To achieve bacteria detection in milk, Yin et al [46] fabricated an array of microchips having multiple functional units for cell lysis, bacterial DNA extraction, multiplex digital recombinase polymerase amplification, and fluorescence detection.…”

“…For example, Dogan et al. [45] extracted E. coli from bacteria‐spiked milk by specific antibody‐modified magnetic nanoparticles, and transported the magnetic immunocomplexes to the SERS detection microchamber by moving the external magnet. To achieve bacteria detection in milk, Yin et al.…”

“Magnet” Based on Activated Silver Nanoparticles Adsorbed Bacteria to Predict Refractory Apical Periodontitis Via Surface-Enhanced Raman Scattering

“…At present, most reported strategies for bacterial detection aim to indirectly acquire the SERS signals via binding to nanoparticles with antibodies, aptamers, and antibiotics. For example, Dogan et al . designed a specific antibody-coupled capture probe and signal probe to enable the sensitive detection of Escherichia coli (E.…”