More reference to support introduction

This section of the introduction could benefit from a few more references that are needed to refer to the called-out scientific facts or opinions, as certain statements that are currently not referenced should be referenced in my opinion.

For example, ‘More-over, the optical flow cytometer can analyze several thousands of cells per second’ would need a reference, as this number has to come from somewhere else – it will depend on assay setup, instrument, date, and many different factors.

This statement also remains true for the other sections in the introduction. As an interesting reference to point to, which is of newer date, but closely related to the work presented here, please have a look at:

https://www.mdpi.com/1999-4915/16/3/339

as this approach probably is the closest to the developed approach. It might be worth adding a short introduction to it.