Nanogap traps for passive bacteria concentration and single-point confocal Raman spectroscopy

Microfluidic-SERS platform with in-situ nanoparticle synthesis for rapid E. coli detection in food

A microfluidic-surface enhanced Raman spectroscopy (SERS) platform for rapid detection of Escherichia coli in food products is proposed. By implementing a Y-junction serpentine microfluidic channel, we achieved in-situ synthesis of silver nanoparticles (AgNPs), for enhancing SERS signal intensity. The synthesis of AgNPs was guided by specific aptamers bound to the bacterial cell, which facilitated formation of nanoparticles. This aptamer guided in-situ synthesis ensured specificity and accuracy in detecting E. coli with a limit of detection of 1.1 CFU/mL and a linear detection range from 102 to 108 CFU/mL, showing superior sensitivity compared to other reported methods. The technique also showed recovery value ranging from 83 to 125 % for lettuce sample. The platform combines the advantages of microfluidics and SERS, enabling rapid, sensitive, and label-free detection of pathogens in food. This method addresses limitations of conventional culture-based techniques and other molecular diagnostics, offering a promising tool for microbial food safety analysis.

Development of a Mass-Producible Microfluidic Device for Single and Bulk Mycobacteria Investigations

We developed a mass-producible microfluidic device capable of long-term observations of single bacilli and bulk bacteria culture interactions for subsequent antimicrobial resistance (AMR) studies. The device provides high consistency across separate devices due to its standardized manufacturing process unlike conventional microfluidic devices. Mycobacteria bovis BCG and M. smegmatis are trapped within the microfluidic device using minimal equipment and capillary-based techniques, acting as a surrogate model for the highly pathogenic bacteria M. tuberculosis. Individual bacilli and bulk bacteria aggregates were observed across a span of ten growth cycles, revealing bacteria growth morphologies alike those in past research. We accordingly propose that this chip would be appropriate for observations of AMR trials involving M. tuberculosis.

Raman-Activated, Interactive Sorting of Isotope-Labeled Bacteria

Due to its high spatial resolution, Raman microspectroscopy allows for the analysis of single microbial cells. Since Raman spectroscopy analyzes the whole cell content, this method is phenotypic and can therefore be used to evaluate cellular changes. In particular, labeling with stable isotopes (SIPs) enables the versatile use and observation of different metabolic states in microbes. Nevertheless, static measurements can only analyze the present situation and do not allow for further downstream evaluations. Therefore, a combination of Raman analysis and cell sorting is necessary to provide the possibility for further research on selected bacteria in a sample. Here, a new microfluidic approach for Raman-activated continuous-flow sorting of bacteria using an optical setup for image-based particle sorting with synchronous acquisition and analysis of Raman spectra for making the sorting decision is demonstrated, showing that active cells can be successfully sorted by means of this microfluidic chip.

Constrained Volume Micro- and Nanoparticle Collection Methods in Microfluidic Systems

Particle trapping and enrichment into confined volumes can be useful in particle processing and analysis. This review is an evaluation of the methods used to trap and enrich particles into constrained volumes in microfluidic and nanofluidic systems. These methods include physical, optical, electrical, magnetic, acoustic, and some hybrid techniques, all capable of locally enhancing nano- and microparticle concentrations on a microscale. Some key qualitative and quantitative comparison points are also explored, illustrating the specific applicability and challenges of each method. A few applications of these types of particle trapping are also discussed, including enhancing biological and chemical sensors, particle washing techniques, and fluid medium exchange systems.

Raman spectroscopy-based microfluidic platforms: A promising tool for detection of foodborne pathogens in food products

Rapid and sensitive detection of foodborne pathogens in food products is paramount for ensuring food safety and public health. In the ongoing effort to tackle this issue, detection methods are continually researched and upgraded to achieve rapidity, sensitivity, portability, and cost-effectiveness. This review addresses the critical need for improved technique by focusing on Raman spectroscopy-based microfluidic platforms, which have shown potential in revolutionizing the field of foodborne pathogen analysis offering point-of-care diagnosis and multiplex detection. The key problem lies in the persistent threat of compromised food quality and public health due to inadequate pathogen detection. The review elucidates the various trapping strategies employed in a microfluidic platform, including optical trapping, electrical trapping, mechanical trapping, and acoustic trapping for the capture of microbial cells. Subsequently, the review delves into the key aspects of the application of microbial detection in food products, highlighting recent advances and challenges in the field. The integrated technique allows point-of-care application assessment, which is an attractive quality for in-line and real-time detection of foodborne pathogens. However, the application of the technique in food products is limited and requires further research to combat the complexity of the food matrix, reduced costs of production, and ensure real-time use for diverse pathogens. Ultimately, this review aims to propel advancements in microbial detection, thus promoting enhanced food safety through state-of-the-art technologies.