In this study, a development of a novel calcium phosphate-polymer hybrid nanoparticle system is reported.The nanoparticle system can co-encapsulate and co-deliver a combination of therapeutic agents with different physicochemical properties (i.e., inhibitors for microRNA-221 and microRNA-222 (miRi-221/222) and paclitaxel (pac)).miRi-221/222 are hydrophilic and were encapsulated with calcium phosphate by co-precipitation in a water-in-oil emulsion.The precipitates were then coated with an anionic lipid, dioleoylphosphatidic acid (DOPA), to co-encapsulate hydrophobic paclitaxel outside the hydrophilic precipitates and inside the same nanoparticle.The nanoparticles formed by following this approach had a size of about ≤100nm and contained both lipid-coated calcium phosphate/miRi and paclitaxel.This nanoparticle system was found to simultaneously deliver paclitaxel and miRi-221/222 to their intracellular targets, leading to inhibit proliferative mechanisms of miR-221/222 and thus significantly enhancing the therapeutic efficacy of paclitaxel.

Recent studies of signaling networks point out that an order of drugs to be administrated to the cancerous cells can be critical for optimal therapeutic outcomes of recalcitrant metastatic and drug-resistant cell types. In this study, a development of a polymeric nanoparticle system for sequential delivery is reported. The nanoparticle system can co-encapsulate and co-deliver a combination of therapeutic agents with different physicochemical properties [i.e. epidermal growth factor receptor (EGFR) inhibitor, erlotinib (Ei), and doxorubicin (Dox)]. Dox is hydrophilic and was complexed with anionic lipid, 1,2-dioleoyl-sn-glycero-3-phosphate (DOPA), via ion pairing to form a hydrophobic entity. Then it was co-encapsulated with hydrophobic Ei in a poly(L-lactide)-b-polyethylene glycol (PLA-b-PEG) nanoparticle by nanoprecipitation. The complexation of Dox with DOPA greatly helps the encapsulation of Dox, and substantially reduces the release rate of Dox. This nanoparticle system was found to burst the release of Ei with a slow and sustained profile of Dox, which is an optimal course of administration for these two drugs as previously reported. The efficacy of this sequential delivery nanoparticle system was validated in vitro and its in vivo potential applicability was substantiated by fluorescent imaging of high tumor accumulation.