Self-assembling doxorubicin-prodrug nanoparticles as siRNA drug delivery system for cancer treatment: in vitro and in vivo

Co-delivery of siRNAs and chemotherapeutic drugs to kill tumors have achieved superior tumor growth inhibition. However, due to siRNAs and chemotherapeutic drugs with different molecular properties, co-delivery carriers use more cationic materials to bind siRNAs and excessive inert materials to embed drugs, causing low drug-loading contents and systemic toxicity. To achieve this goal, doxorubicin (DOX) is chemically conjugated to stearoyl chloride (C18) through N-methyldiethanol amine (N) as cross-linker to form amphiphilic C18-N-DOX. C18-N-DOX contains a tertiary amine that can complex siRNAs at low pH (pH 3) and reduce the density of the positive charges on the surface of NPs at physiological pH (pH 7.4). C18-N-DOX, together with 1,2-distearoyl-sn-g/ycero-3-phosphoethanolamine-N-methoxy-poly(ethylene glycol 2000) DSPE-PEG2000, self-assemble into DOX-prodrug nanoparticles (DOX-prodrug NPs), which bind siRNAs in citrate buffer (pH 3) to form DOX-prodrug NPs/siRNA. After replacing citrate buffer (pH 3) with PBS (pH 7.4), DOX-prodrug NPs/siRNA have slight negative charges due to complexed more siRNAs. In this study, clear evidence is shown that DOX-prodrug NPs can deliver siRNA to the same tumor cells both in vitro and in vivo. Moreover, DOX-prodrug NPs/siRNA show a great effect on inhibiting tumor cell growth both in vitro and in vivo. Therefore, the DOX-prodrug NPs are promising candidates as siRNAs delivery system for tumor therapy.