No abstract

The importance of food safety has resulted in a demand for a more rapid, high-throughput method for total viable count (TVC). The industry standard for TVC determination (ISO 4833:2003) is widely used but presents users with some drawbacks. The method is materials- and labor-intensive, requiring multiple agar plates per sample. More importantly, the method is slow, with 72 h typically required for a definitive result. Luxcel Biosciences has developed the GreenLight Model 960, a microtiter plate-based assay providing a rapid high-throughput method of aerobic bacterial load assessment through analysis of microbial oxygen consumption. Results are generated in 1-12 h, depending on microbial load. The mix and measure procedure allows rapid detection of microbial oxygen consumption and equates oxygen consumption to microbial load (CFU/g), providing a simple, sensitive means of assessing the microbial contamination levels in foods (1). As bacteria in the test sample grow and respire, they deplete O2, which is detected as an increase in the GreenLight probe signal above the baseline level (2). The time required to reach this increase in signal can be used to calculate the CFU/g of the original sample, based on a predetermined calibration. The higher the initial microbial load, the earlier this threshold is reached (1).

High-throughput in vitro cell metabolism assays are of particular use for identification and delineation of mitochondrial toxicity and related metabolic perturbation. Here, a panel of fluorescence-based metabolism assays are described for measuring oxygen consumption, glycolytic flux, and cellular oxygenation. They can be applied to analysis of both isolated mitochondria and cell models. Sample data are presented illustrating how these protocols can be used to examine drug treatment, the interplay between oxidative and glycolytic ATP generation, and the impact of cell oxygenation on this balance. Descriptions are provided on how these measurements can be applied to 3D systems and how they can be multiplexed with other relevant metabolic readouts. Mitochondrial isolation and cell permeabilization protocols are also provided. © 2016 by John Wiley & Sons, Inc.

Knowledge of in situ oxygenation of cells in 2D and 3D cultures offers important insights into the impact of oxygen on cellular function. Here we outline how such measurements can be performed in 2D cultures of adherent cells and also in cells cultured on 3D scaffolds. Measurements are performed on conventional time-resolved fluorescence plate readers using the intracellular oxygen-sensitive probe MitoXpress(®)-Intra. We also illustrate how the impact of drug treatment on cell oxygenation can be assessed and how the link between oxygenation and glycolytic metabolism can be examined.

The data currently described was generated within the EU/FP7 HeCaToS project (Hepatic and Cardiac Toxicity Systems modeling). The project aimed to develop an in silico prediction system to contribute to drug safety assessment for humans. For this purpose, multi-omics data of repeated dose toxicity were obtained for 10 hepatotoxic and 10 cardiotoxic compounds. Most data were gained from in vitro experiments in which 3D microtissues (either hepatic or cardiac) were exposed to a therapeutic (physiologically relevant concentrations calculated through PBPK-modeling) or a toxic dosing profile (IC20 after 7 days). Exposures lasted for 14 days and samples were obtained at 7 time points (therapeutic doses: 2-8-24-72-168-240-336 h; toxic doses 0-2-8-24-72-168-240 h). Transcriptomics (RNA sequencing & microRNA sequencing), proteomics (LC-MS), epigenomics (MeDIP sequencing) and metabolomics (LC-MS & NMR) data were obtained from these samples. Furthermore, functional endpoints (ATP content, Caspase3/7 and O2 consumption) were measured in exposed microtissues. Additionally, multi-omics data from human biopsies from patients are available. This data is now being released to the scientific community through the BioStudies data repository (https://www.ebi.ac.uk/biostudies/).