Flow cytometers and cell sorters have become powerful tools for research and are now in common use. Flow cytometers pass cell suspensions in a narrow fluid stream through a laser beam, measuring various characteristics of each cell that passes by (cell size, volume, light/fluorescent qualities, etc.) before flowing into a waste collection container. Cell sorters operate on a similar principle, with the addition that once the flow cytometer measures a cell’s characteristics, desired cells are diverted into a separate collection vessel. This occurs when a force is applied to the cell suspension fluid stream, forming droplets containing single cells that are then physically separated (commonly via electrostatic charge) from the other cell droplets that do not meet those characteristics.
Based on this principle of operation, aerosols are readily produced during use. This poses a considerable hazard when biohazardous materials are being utilized. BSCs (Biological Safety Cabinets), sometimes custom-built for the equipment, can house flow cytometers and cell sorters to contain and help mitigate exposure to biohazardous aerosols. For example, the sorting of unfixed fluorescently labeled HEK293 cells (a human-derived cell line) must be conducted on a cell sorter that resides within a BSC to contain potentially aerosolized human cells that can harbor bloodborne pathogens. Additionally, vented flow cytometer waste containers require an appropriate filter (ex. in-line HEPA filter) on the vent. This helps to reduce the risk of biohazardous aerosol exposure from the waste container until it can be appropriately decontaminated. When appropriate engineering controls are not available for flow cytometry/cell sorting of live, biohazardous materials, additional risk assessment will be required to determine the appropriate PPE and administrative controls.
Samples that are fixed using a validated method and are no longer biohazardous may be analyzed in a flow cytometer on the open bench at BSL1. Fixed or unfixed samples containing chemical or radiological hazards have additional considerations and require extra precautions. Please contact the Office of Biological Safety at biosafety@uky.edu, the Office of Chemical and Laboratory Safety at labsafety@uky.edu, or the Office of Radiation Safety at radsafe@uky.edu if you plan to perform flow cytometry/cell sorting on materials with these hazards.
The following points are important to remember when conducting work with flow cytometers or cell sorters: