Design and Optimization of Cationic Nanocapsules for Topical Delivery of Tretinoin: Application of the Box-Behnken Design, In Vitro Evaluation, and Ex Vivo Skin Deposition Study

Table 1

Design-Expert for optimization of the encapsulated TTN.

(a)

Factors (independent variables)	Levels
	High (+1)	Medium (0)	Low (-1)
: polymer amount (mg)	200	125	50
: drug amount (mg)	20	12.5	5
: oil amount (ml)	1	0.6	0.2

(b)

Responses (dependent variables)	Constraints
: encapsulation efficiency (%)	Maximize
: particle size (nm)	Minimize