Soluplus-stabilized 5-fluorouracil-entrapped niosomal formulations prepared via active and passive loading techniques: comparative physico-chemical evaluation

The objective of this study was to prepare and conduct a comparative analysis on 5-fluorouracil (5FU) niosomes stabilized with or without Soluplus, utilizing, respectively, passive loading and active loading techniques. Cholesterol was combined with Span 40 and Tween 40 surfactants to prepare several niosomal formulations by either passive or active methods. Encapsulation efficiency (EE%), loading capacity (LC), mean particle sizes, polydispersity indices (PDI), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), pH stability, and in vitro drug release in bio relevant media of pH 1.2, 6.8, and 7.4 were employed to evaluate the formulations. Batches made using the active loading approach (B1-B5) demonstrated higher entrapment efficiency (25-40%) (p < 0.05) than those made using the passive loading method (20%) (with the exception of batch A1). In comparison to niosomes made using the passive loading method, the active loading methodology produced niosomes with a lower PDI (< 0.25) and particle size (< 70 nm). SEM revealed spherical and discrete vesicles for the Soluplus stabilized niosomes. Both approaches produced niosomes with prominent hydrogen bonding as observed in the FTIR study. The formulations were stable and sustained drug release, but the active loading strategy imparted a more sustained release pattern than the passively loaded one. Soluplus stabilized niosomes demonstrated higher (p < 0.05) drug release (60-70%) in all release media. Based on the production of smaller particle sizes and narrower size distribution, the active loading strategy may be a more effective way to load hydrophilic medicines such as 5FU into niosomes.