Quantifying Lipid-encapsulated Drug Delivery

The STB-ME samples were placed in an ultrafiltration tube with an MW cut off of 10 kDa (Amicon^® Ultra-4, Merck Millipore Ltd. Ireland) and centrifuged (4,000 rpm, 4°C) by a low-temperature centrifuge for 10 min. The filtrate was obtained from the bottom of the ultrafiltration tube by centrifugation, while the STB content of STB-ME was analyzed without centrifugation. The filtrates and the STB-ME samples were diluted with methanol in different proportions, and then the STB content was analyzed by HPLC (Section 2.3). The drug loading (DL) and encapsulation efficiency (EE) were calculated by the following two equations (Vieira et al., 2020 (link); Ma et al., 2022 (link)): $\mathit{D}\mathit{L}\left(\%\right)=\frac{{\mathit{W}}_{\mathit{t}}-{\mathit{W}}_{\mathit{f}}}{{\mathit{W}}_{\mathit{m}}}\times \mathbf{100}\%$
$\mathit{E}\mathit{E}\left(\%\right)=\frac{{\mathit{W}}_{\mathit{t}}-{\mathit{W}}_{\mathit{f}}}{{\mathit{W}}_{\mathit{t}}}\times \mathbf{100}\%$ where ${\mathit{W}}_{\mathit{t}}$ is the mass of total STB in STB-ME, ${\mathit{W}}_{\mathit{f}}$ is the mass of free STB after centrifugation, and ${\mathit{W}}_{\mathit{m}}$ is the mass of STB and lipid.