Formulation and optimization of silymarin-encapsulated binary micelles for enhanced amyloid disaggregation activity

Silymarin (SLY) is a natural hydrophobic polyphenol that possesses antioxidant and amyloid fibril (Aβ_1-42) inhibition activity, but its activity is hindered due to low aqueous solubility. In this study, SLY is encapsulated in binary micelle (SLY-BM) that has been utilized to enhance the Aβ_1-42 fibril disaggregation. To enhance the aqueous solubility, SLY payload in micelles were optimized using Box-Behnken Design (BBD) to increase the efficiency of Aβ_1-42 fibril disaggregation. BBD was used to investigate the effect of ratio of Solutol HS15:Poloxamer-188, amount of acetone and hydration volume on critical quality attributes, particle size, and entrapment efficiency for SLY-BM. Furthermore, SLY-BM was characterized for its physical and drug release properties. The Aβ_1-42 fibril disaggregation and antioxidant studies were monitored using spectroscopic and microscopic techniques. BBD optimized the particle size <50 nm with %EE > 80%, and solubility factor of SLY-BM was enhanced to 460 folds than free SLY. Inhibitory concentration 50% (IC₅₀) value of SLY-BM was 19.67 µg/mL compared to free SLY (30.06 µg/mL) in diphenylpicrahydrazyl assay. SLY-BM increased the Aβ_1-42 disaggregation compared to free SLY observed via thioflavin-T assay, photon correlation spectroscopy, and circular dichorism. Further morphological evaluation of Aβ_1-42 disaggregation was monitored by microscopy which showed that SLY-BM disaggregated the fibrils in 48 h. According to our findings, we concluded that SLY-BM micelles are potential candidates for delivery of neuroprotective agents.