I did an LDH assay and have six concentrations of drugs I treated my cells with and when I put the LDH assay data in a graph, I see a normal distribution pattern. The 3rd concentration of the drug results in the highest cytotoxicity percentage but from the 4th concentration, the cytotoxicity decreases. How to decide on which concentration is the most suitable for my cells?
Try to calculate the selectivity index value which is a ratio between CC50 of drugs on cells and IC50 of drugs on parasite. This is a better way to discover if the drug/drugs can be used for further investigations or not. The higher the CC50 value and the smaller the IC50 value, the greater the selectivity index and the safer and more efficient are the drugs
Dear Fa Ro ,
There are different approaches depending on your design (do you want it to kill your cells? What will you use this concentration for?). The most common one is IC50 where you end up having both death and living cells.
Here are some common approaches:
1. IC approach: You pick a concentration which kills a certain percentage of your population (IC%). Most common one is IC50 (concentration which kills half of your cells) but you can go for IC25 or IC75 as well.
If you do not have the exact IC% value, you may pick the closest concentration or you may draw a line or a curve in your graph and then calculate from the slope (equation).
2. Lowest effective concentration. You pick the lowest concentration which kills your cells (viability becomes lower than 100% for the first time).
3. Highest ineffective concentration. You pick the highest concentration which does not kill your cells (viability is still 100%). This is usually when you want all of your cells alive (combination studies).
Cheers.
Burak
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