Question: How can Xenium slides be stored prior to a Xenium Analyzer run?
Answer: Store cassettes sealed with a Xenium Cassette Lid as indicated in the Xenium In Situ Gene Expression - Probe Hybridization, Ligation & Amplification.
For short-term storage, cassettes with lids should always be stored hydrated with fresh PBS-T buffer at 4°C in the dark. While we recommend proceeding with Xenium Analyzer run within 4 days of the assay workflow, it is possible to store slides for a longer period of time without compromising assay performance. For long-term storage, Xenium cassette lids can be replaced with a slide seal. (Any PCR film is okay as long as it is sticky enough to reduce evaporation.) Xenium slides can be stored for up to 24 days prior to Xenium Analyzer run with minimal impact on data quality generated. During this time, the PBS-T storage buffer is recommended to be replaced through a buffer exchange every ~3-4 days.
The risk of storing slides for more than 24 days is that there may be a lower number of genes or transcripts detected per cell and tissue morphology may change over time. Furthermore, there may be microbe growth. This is dependent on many factors including the input tissue quality, how nuclease-free the workflow is, and how microbe-free the lab environment is.
If there are concerns over microbial contamination during long-term storage, the PBS-T storage buffer can be supplemented with 0.05% sodium azide (NaN3). Sodium azide + PBS-T buffer should be exchanged for PBS-T prior to an instrument run.
As a best practice, PBS-T should always be made fresh, both for the assay workflow and also for slide storage.
Slides can be stored after Xenium Analyzer run (or in the event of a run failure) in a similar manner. Combined storage, both before and after a Xenium Analyzer run should not exceed 1 month in total. Please reach out to firstname.lastname@example.org for more information.
Products: Xenium In Situ Gene Expression, Xenium Analyzer