I am looking to conduct transport studies in CaCo-2 cells using three fluorescent dextrans namely, Fluorescein Salt (MW~3.7KD), FD4 (MW~ 3-5KD) and FD20S (MW~20KD). All three of them are from Sigma-Aldrich. Though, generally they are used in a 1mg/ml concentration, but, I am still wondering is there any other variation to it which someone has used before?