Exosomal fragment enclosed polyamine-salt nano-complex for co-delivery of docetaxel and mir-34a exhibits higher cytotoxicity and apoptosis in breast cancer cells

A novel core-shell nanocarrier system has been designed for co-delivery of a small anticancer drug, docetaxel (DTX) and tumor suppressor (TS) miR-34a named as Exo(PAN_34a+DTX). The core is formed by pH dependent polyamine salt aggregates (PSA) containing both the payloads and the shell is formed by RAW 264.7 cell derived exosomal fragments. Herein, phosphate driven polyallylamine hydrochloride (PAH, MW:17,500 Da) PSA was formed in presence of miR-34a and DTX to form PAN_34a+DTX. The formulation exhibited pH dependent DTX release with only 33.55 ± 2.12% DTX release at pH 7.2 and 75.21 ± 1.8% DTX release till 144 h at pH 5.5. At 1.21 molar ratio of phosphate to the amine (known as R value), efficient complexation of miR-34a (3.6 μM) in the PAN particles was obtained. PAN_34a+DTX demonstrated particle size (163.86 ± 12.89 nm) and zeta-potential value of 17.53 ± 5.10 mV which upon exosomal fragment layering changed to - 7.23 ± 2.75 mV which is similar to the zeta-potential of the exosomal fragments, i.e., - 8.40 ± 1.79 mV. The final formulation Exo(PAN_34a+DTX), loaded with 40 ng/mL DTX and 50 nM miR-34a exhibited 48.20 ± 4.59% cytotoxicity in triple negative breast cancer (TNBC) cells, 4T1. Co-localization of CM-DiI (red fluorescence) stained exosomal fragments and FAM-siRNA (green fluorescence) in the cytoplasm of 4T1 cells after 6 h of Exo(PAN_FAM) treatment confirmed the efficiency of the designed system to co-deliver two actives. Exo(PAN_34a+DTX) also reduced BCL-2 expression (target gene for miR-34a) by 8.98 folds in comparison to free DTX confirming promising co-delivery and apoptosis inducing effect of Exo(PAN_34a+DTX) in 4T1.