Furthermore, an experimental design was employed in order to study the effect of independent variables, namely drug amount (X1, 500-1000 mg), the amount of PVA (X2, 3.33-7.5%), the amount of chitosan (X3, 0.5-1%), and F-T cycle (X4, 3-7 cycles) on the dependent variables, including encapsulation efficiency, swelling index, adsorption of protein onto hydrogel surface, and skin permeation. 
THERM