Table 1.

Independent and dependent variables of the 3-level, 3-factor Box–Behnken design.

Independent Variables	Coded Levels
	Low Level (−1)	Medium Level (0)	High Level (1)
X1 = solid lipid (mg)	250	300	350
X2 = liquid lipid (mg)	50	100	150
X3 = surfactant (mg)	60	80	100
Dependent variables		Criteria
Y1 = particle size (nm) Y2 = encapsulation efficiency (%) Y3 = loading capacity		Optimum (200 nm)
		Maximum (100%)
		Maximum