Table 1 Variables and Their Levels in Box-Behnken Design
Factors Factor levels
− 1 (low) 0 (medium) + 1 (high)
A: lecithin (mg) 100 200 300
B: chitosan (mg) 10 15 20
C: PEG 2000 (mg) 20 30 40
Dependent variables Constraints
Y1 = entrapment efficiency (%EE) Maximise
Y2 = particle size (nm) Minimise
Y3 = zeta potential (mV) Maximise