Table 1.

Orthogonal design factors and levels for the double emulsion method

Factors	Level
	1	2	3
Inner water phase volume (mL) (A)	0.1	0.2	0.4
VLPVPR (mg) (B)	5	7.5	10
Outer water phase volume (mL) (C)	1	2	3
Ultrasound for double emulsion (D)	5 s ×1	5 s ×2	5 s ×3

Note: (A), (B), (C), and (D) are used to represent different factors.

Abbreviations: s, seconds; VLPVPR, Val-Leu-Pro-Val-Pro-Arg.