2.6. Entrapment Efficiency (EE%)

The EE% of AT-NLC dispersion was assessed by the centrifugation method [25]. A known volume of freshly prepared AT-NLCs was centrifuged at 12,000 rpm and 4 °C for 1 h using a cooling centrifuge (2-16KL, Sigma Laborzentrifugen GmbH, Osterode am Harz, Germany). The supernatant was diluted to a suitable concentration, and the concentration of the free (non-entrapped) drug was measured spectrophotometrically against a blank at 246 nm. AT entrapment efficiency was then determined using the following equation [26]:

where EE% is the entrapment efficiency, W_t is the amount of added drug during the preparation of NLCs, and W_f is the free drug amount in the supernatant after centrifugation.