transfection of endothelial cells Cell density should be 50~80% confluent on the day of transfection for each well of cells to be transfected, dilute 05 μg of dna into 100 μl of opti-mem® i reduced serum medium without serum if using plus™ reagent: mix plus™ reagent gently before use, then add 05 μl plus™ reagent (a 1:1 ratio to dna) directly to the diluted dna.