Using resazurin is a little bit tricky since it is self-quenching due to its color. It's best to use just slightly more than the maximum amount of reducing equivalents t be measured. Having said that, for use with cells, our 'standard' solution is 0.12 mg/ml in PBS. 10 ul is transferred to a well containing cells in 100 ul of medium.

I am not an expert in this field, but I am very interested and have researched to find an answer. I received some assistance from tlooto.com for this response. Could you please review the response below to see if it is correct?

To prepare resazurin for the MIC assay, dissolve 15 mg of resazurin powder in 50 mL of sterile distilled water to make a 0.03% (w/v) solution, as suggested by existing protocols. Filter-sterilize the solution using a 0.22 µm filter to prevent microbial contamination. Add 10 µL of this solution to each well in a 96-well plate with your bacterial culture and test compound. Incubate at 37°C for 4-6 hours. A color change from blue to pink indicates viable bacteria; the MIC is the lowest concentration without color change [1][2]. This method ensures reliable results in determining bacterial viability.

Reference

[1]

Lavogina, D., Lust, H., Tahk, M., Laasfeld, T., Vellama, H., Nasirova, N., Vardja, M., Eskla, K., Salumets, A., Rinken, A., & Jaal, J. (2022). Revisiting the Resazurin-Based Sensing of Cellular Viability: Widening the Application Horizon. Biosensors-Basel, 12.

[2]

Foerster, S., Desilvestro, V., Hathaway, L. J., Althaus, C., & Unemo, M. (2017). A new rapid resazurin-based microdilution assay for antimicrobial susceptibility testing of Neisseria gonorrhoeae. Journal of Antimicrobial Chemotherapy, 72, 1961 - 1968.

That protocol uses about 2X as much as we do but it should be fine.