Lyophilized Hybrid Nanostructured Lipid Carriers to Enhance the Cellular Uptake of Verapamil: Statistical Optimization and In Vitro Evaluation

Table 1 Description of 2⁴ full factorial design

Factors (independent variables)	Low level	High level
A: Homogenization time	20.00 min	30.00 min
B: Solid lipid (Compritol 888 ATO®)	270.00 mg	285.00 mg
C: Liquid lipid (oleic acid)	15.00 mg	30.00 mg
D: Surfactants (Poloxamer 188: Tween 80®, 1:1)	200.00 mg	300.00 mg
Responses (dependent variables)	Constraints
PS (nm)	Minimize
PDI	Minimize
ZP (mV)	Maximize
EE (%)	Maximize

PS particle size, PDI polydispersity index, ZP zeta potential, EE entrapment efficiency