Turning Cells into Reagents: The Preparation of Assay Ready Cells for Routine Use in Bioassays.

Assay ready cells are cryopreserved at a highly functional state and can be used in cell-based assay without prior cultivation or cell passaging. Basically, like any other reagent, the cells are applied to the assay instantly after thawing. Introduced initially in the drug discovery process where assay ready Frozen Instant Cells help to streamline cell-based high-throughput screening campaigns, the methodology now has been accepted for a much broader scope of applications and industries. The preparation of assay ready Frozen Instant Cells is not so much a piece of magic but a combination of good cell culture practice, careful handling, and individually optimized cryopreservation protocols. Here, a standard protocol is presented, how HepG2 cells are frozen in an assay ready quality to be used as a reagent in routine cell-based assays.

Development and validation of a ready to use cryo-EROD assay for the standardized screening of dioxins and dioxin-like compounds in foodstuffs.

Recent European regulations have indicated the need for new bioanalytical screening methods capable of monitoring dioxin and dioxin-like compounds in foodstuffs and environmental samples, cost-effectively and with a quicker turnaround. Cryo-cells of the hepatic H4IIE line preserved in 96-well plates were exposed to sample extracts prepared from various foodstuffs and analysed for their content of dioxins and dioxin-like compounds by means of the 7-Ethoxyresorufin-O-Deethylase (EROD)-assay in two laboratories. Assay data were compared between both laboratories and results from instrumental analysis used as a confirmatory method. Additionally, cut-off values for the different studied matrices were derived. The current European regulation regarding methods of analysis for the control of foodstuffs was applied with the aim of determining the feasibility of the cryo-methodology. Results obtained in both laboratories were in congruence with the required validation parameters of the Commission Regulation (EU) No 2017/644. Cut-off values should be established matrix-dependent to reduce the rate of false compliant results and to keep the rate of false non-compliant results under control. In summary, the ready-to-use cryo-assay method for the bioanalytical screening of foodstuffs in control laboratories without cell-culture facilities has successfully proven to be accurate, far quicker and more cost effective than current methods.