Calcium phosphate-polymeric nanoparticle system for co-delivery of microRNA-21 inhibitor and doxorubicin

[Display omitted] •NPs successfully achieved sequential delivery of miR-21 inhibitor followed by Dox.•NPs delivered miR-21 inhibitor to the cytoplasm through endosomal escape.•NPs downregulated miR-21 levels and upregulated PTEN levels.•NPs showed enhanced cytotoxicity against MDA-MB-231 and A549 cells. Targeted combination therapy has shown promise to achieve maximum therapeutic efficacy by overcoming drug resistance. MicroRNA-21 (miR-21) is frequently overexpressed in various cancer types including breast and non-small cell lung cancer and its functions can be inhibited by miR inhibitor (miR-21i). A combination of miR-21i and a chemo drug, doxorubicin (Dox), can provide synergistic effects. Here, we developed a calcium phosphate (CaP)-coated nanoparticle (NP) formulation to co-deliver miR-21i along with Dox. This NP design can be used to deliver the two agents with different physiochemical properties. The NP formulation was optimized for particle size, polydispersity, Dox loading, and miR-21i loading. The NP formulation was confirmed to downregulate miR-21 levels and upregulate tumor suppressor gene levels. The cytotoxic efficacy of the combined miR-21i and Dox-containing NPs was found to be higher than that of Dox. Therefore, the CaP-coated hybrid lipid-polymeric NPs hold potential for the delivery of miR-21i and Dox.