Label-free 1D microfluidic dipstick counting of microbial colonies and bacteriophage plaques

Rapid point-of-care pathogen sensing in the post-pandemic era

In the post-pandemic era, interest in on-site technologies capable of rapidly and accurately diagnosing viral or bacterial pathogens has significantly increased. Advances in functional nanomaterials and bioengineering have propelled the progress of point-of-care (POC) sensors, enhancing their speed, specificity, sensitivity, affordability, ease of use, and accuracy. Notably, biosensors that utilize surface-enhanced Raman scattering (SERS) technology have revolutionized the rapid and sensitive diagnosis of biomarkers in pathogenic infections. This review of current POC diagnostics highlights the growing emphasis on immunoassays for swift pathogen analysis, augmented by the integration of deep learning for swift interpretation of complex signals through tailored algorithms.

Direct optical microalgal growth assessment using 'dip stick' microcapillary strips: A case study with Parachlorella kessleri

Microalgal cultivation is increasingly important for industrial, agricultural, and environmental monitoring. Current methodologies for monitoring microalgal growth require periodical sampling, bulky laboratory equipment and specialized personnel. A novel 'dip-stick' micro-cultivation methodology based on fluorinated ethylene propylene microcapillary strips is herein proposed for real-time detection of microalgal growth. Cultivation of the microalgae Parachlorella kessleri in microcapillary strips, with no replacement of growing media nor physical aeration, matched the growth rate µ observed for a sparged Erlenmeyer (µ=0.37 /day) representing a > 3-fold improvement compared to an unsparged Erlenmeyer (µ=0.12 /day). Growth modelling of P. kessleri in the microcapillary strips established light intensity as a limiting growth factor. The transparency of the microcapillary strips enabled accurate and non-invasive determination of single-cell morphology and cell cycle events, which have been benchmarked against high-resolution flow cytometry. The microanalytical solution herein presented could offer a new bioanalytical solution for in-situ water management and high-throughput microalgal productivity assessment.

High-Throughput Bacteriophage Testing with Potency Determination: Validation of an Automated Pipetting and Phage Drop-Off Method

The development of bacteriophages (phages) as active pharmaceutical ingredients for the treatment of patients is on its way and regulatory agencies are calling for reliable methods to assess phage potency. As the number of phage banks is increasing, so is the number of phages that need to be tested to identify therapeutic candidates. Currently, assessment of phage potency on a semi-solid medium to observe plaque-forming units is unavoidable and proves to be labor intensive when considering dozens of phage candidates. Here, we present a method based on automated pipetting and phage drop-off performed by a liquid-handling robot, allowing high-throughput testing and phage potency determination (based on phage titer and efficiency of plaquing). Ten phages were tested, individually and assembled into one cocktail, against 126 Escherichia coli strains. This automated method was compared to the reference one (manual assay) and validated in terms of reproducibility and concordance (ratio of results according to the Bland and Altman method: 0.99; Lin's concordance correlation coefficient: 0.86). We found that coefficients of variation were lower with automated pipetting (mean CV: 13.3% vs. 24.5%). Beyond speeding up the process of phage screening, this method could be used to standardize phage potency evaluation.

Progress in methods for the detection of viable Escherichia coli

Escherichia coli (E. coli) is a prevalent enteric bacterium and a necessary organism to monitor for food safety and environmental purposes. Developing efficient and specific methods is critical for detecting and monitoring viable E. coli due to its high prevalence. Conventional culture methods are often laborious and time-consuming, and they offer limited capability in detecting potentially harmful viable but non-culturable E. coli in the tested sample, which highlights the need for improved approaches. Hence, there is a growing demand for accurate and sensitive methods to determine the presence of viable E. coli. This paper scrutinizes various methods for detecting viable E. coli, including culture-based methods, molecular methods that target DNAs and RNAs, bacteriophage-based methods, biosensors, and other emerging technologies. The review serves as a guide for researchers seeking additional methodological options and aiding in the development of rapid and precise assays. Moving forward, it is anticipated that methods for detecting E. coli will become more stable and robust, ultimately contributing significantly to the improvement of food safety and public health.