3.6. Entrapment Efficiency of ASLNs

The encapsulation efficiency was estimated by an ultracentrifugation method. Briefly, 1 mL of ASLNs was centrifuged at 20,000 rpm (21,242× g) for 45 min at 4 °C. The supernatant was collected and the amount of ABZ (which corresponds to the free drug) was measured at 265 nm in UV spectrophotometer (Mapada UV-6100 S, Shanghai Mapada Instruments Co Ltd., Shanghai, China) [25]. The sensitivity of the developed method was found to be in the range of 2–20 mcg/mL (r² value = 0.09997). Supernatant obtained from BSLNs in the same manner was used as blank. The entrapment efficiency was calculated from the following equation.