2.6. Entrapment efficiency (E%)
The pEGFP-encapsulated nanoparticles in AOT microemulsion were separated after ultracentrifugation (40,000 rpm for 4 h at 4 °C) and the pellet, after washing with hexane, was dissolved in acidic buffer (pH 3). The amount of DNA released from the nanoparticles, [DNA]r, was estimated spectrophotometrically by measuring the optical density at ?260nm. The entrapment efficiency (E) was then calculated from the amount of DNA originally added to the microemulsion ([DNA]0) using the equation E% = [DNA]r /[DNA]0 × 100.