*3.4. Curcumin Encapsulation Efficiency*

Encapsulation efficiency (the percentage of drug successfully entrapped into the nanoparticle) was estimated by using Equation (1):

$$Enaporation\,\,efficiency = \frac{mg\,\,of\,\,encap\,\,ulated\,\,Current\,\,in}{mg\,\,of\,\,total\,\,\,Current\,\,in} \times 100\tag{1}$$

To determine the encapsulation efficiency of PG-NPs, suspensions were firstly ultracentrifuged (VWR Microstar 17 centrifuge, Germany) at 16,000 rpm and 24 ◦C for 60 min from the aqueous medium containing a known amount of free curcumin. The supernatant was separated, filtered (0.2 μm nylon syringe filters) and injected in a UPLC (ultra-high-performance liquid chromatography) system for released curcumin quantification (chromatographic method described below).
