Three milligrams of RH, 9.42 mg of BCL, 331 mg of Labrafil M 1944CS, 580 mg of HS15, 193 mg of PEG400, and 122 mg of Bor-PEG400-LA were stirred strongly at 37 °C overnight. 5 mL of ultrapure water was added dropwise until the solution became homogeneous and transparent with opalescence [21 (link)]. Sd III-M and Bor/C6-M were prepared as the similar methods mentioned above, with the exception of replacing the drugs with corresponding probes. The particle size and zeta potential of different microemulsion formulations were measured by dynamic light scattering (DLS, Nano ZS, Malvern, UK). The morphology was evaluated by transmission electron microscopy (TEM, Tecnai 12, Philips, Amsterdam, Netherlands) following previously established methods. Briefly, 15 μL of each sample was deposited on a carbon-coated copper mesh and stained with 1% (v%) phosphotungstic acid. After being dried under infrared light, the sample was observed by TEM. The encapsulation efficiency (EE) and drug loading capacity (LC) of RH and BCL were calculated by the following equations, where Wtested drug, Wfeeding drug, and Wtotal microemulsion represent the weight of the tested drug, initial feeding drug, and total microemulsion, respectively. Bor/RB-M were loaded into centrifuge tubes and centrifuged at 13,000 rpm for 10 min to observe any stratification of the microemulsion. Bor/RB-M was placed in PBS at pH 7.4 and the temperature was set at 25 °C. The changes in particle size and PDI of the microemulsions were measured with the DLS on day 1, 3, 5, and 9 to evaluate the stability of the microemulsions. RH and BCL were quantified by high-performance liquid chromatography (HPLC) by the chromatographic conditions reported previously [22 (link)].
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