Malvern zetasizer 3000 system

The polydispersity index (PDI), hydrodynamic diameter, and zeta potential were measured by a Malvern Zetasizer 3000 system (Malvern Instruments Ltd., Malvern, UK). The morphology of nanoparticles was observed by negative staining method under 80 KV acceleration voltage by transmission electron microscope (TEM, JEM-1400, JEOL, Tokyo, Japan). Several droplets of nano-particle solution were dropped on the carbon-coated copper mesh, air-dried at room temperature, and dyed with 2% (w/v) uranyl acetate solution.

The size distribution, polydispersity (PDI), and zeta potential of the samples were determined using a Malvern Zetasizer 3000 system (Malvern Instruments Ltd., Malvern, UK), and the concentration was 2 mg/mL.
The PCA/DOX NPs solution (40 μg/mL) was dropped on a clean silica gel sheet to dry, and fixed with conductive glue. After being sprayed with gold for 6 min under negative pressure, the samples were observed by a scanning electron microscope (SEM) at a current of 30 mA and a voltage of 30 mV.

The morphology of multifunctional liposomes was observed by transmission electron microscopy (TEM). The particle size, zeta potential, and polydispersity (PDI) were measured via a Malvern Zetasizer 3000 system (Malvern Instruments Ltd., UK). The HPLC was used to detect the drug encapsulation efficiency (EE). Briefly, various liposomes were respectively disrupted into water and equal volume of methanol was added. Subsequently, the solution was sonicated for 20 min and the supernatant was obtained after centrifugation at 10000 rpm for 10 minutes. The amounts of PTX and SOR were measured by HPLC (Shimadzu LC-10AD system, Kyoto, Japan) coupled with a Diamonsil C18 column (250 mm × 4.6 mm, 5 μm) at a flow rate of 1 mL/min and the absorption wavelength of 227 and 266 nm. The mobile phase for PTX was methanol: water (75:25, v/v), while for SOR was a mixture of acetonitrile and disodium phosphate (buffer pH = 4 with phosphoric acid, 55:45, v/v) (Li et al., 2015 (link)). The EE was calculated using the following equations:
$\text{EE}\left(\%\right)=\frac{\text{amount} \text{of} \text{drug} \text{in} \text{the} \text{liposome} }{ \text{amount} \text{of} \text{feeding} \text{drug} }\times 100$