Table 4.

Scheme of the central composite design: independent values, experimental values of the response variables and overall desirability (D)

Runs	Coded values		Responses				Desirability (D)
X1	X2	Y1	Y2	Y3	Y4
1	−1	1	82.18	0.41	62.1	23.2	0.69
2	1	−1	88.53	0.36	82.6	15.3	0.38
3	0	0	93.87	0.39	68	19.3	0.63
4	0	−1.41	94.54	0.45	74	18.6	0.69
5	0	0	94.23	0.42	65.6	16.6	0.66
6	−1.41	0	86.57	0.43	45.3	27.3	0.92
7	1.41	0	79.11	0.33	90.7	12.6	0.16
8	−1	−1	84.8	0.41	59.4	25.9	0.77
9	0	0	92.15	0.4	67.3	15.9	0.58
10	1	1	74.3	0.32	73.7	17.2	0.27
11	0	1.41	60.2	0.32	61.3	20.5	0.30
12	0	0	96.2	0.4	69.6	16.4	0.61

Note: Experimental batch included 4 factorial runs, 4 axial runs and 4 center points.

Abbreviations: X₁, oil/mixed-surfactants ratio; X₂, proportion of aqueous phase; Y₁, encapsulation efficiency (%); Y₂, drug loading (%); Y₃, particle size (nm); Y₄, zeta potential (mV).