No abstract

Previously, we developed a multifunctional envelope-type nano device (MEND) for efficient delivery of nucleic acids. For tumor delivery of a MEND, PEGylation is a useful method, which confers a longer systemic circulation and tumor accumulation via the enhanced permeability and retention (EPR) effect. However, PEGylation inhibits cellular uptake and subsequent endosomal escape. To overcome this, we developed a PEG-peptide-DOPE (PPD) that is cleaved in a matrix metalloproteinase (MMP)-rich environment.In this study, we report on the systemic delivery of siRNA to tumors by employing a MEND that is modified with PPD (PPD-MEND). An in vitro study revealed that PPD modification accelerated both cellular uptake and endosomal escape, compared to a conventional PEG modified MEND. To balance both systemic stability and efficient activity, PPD-MEND was further co-modified with PEG-DSPE. As a result, the systemic administration of the optimized PPD-MEND resulted in an approximately 70% silencing activity in tumors, compared to non-treatment. Finally, a safety evaluation showed that the PPD-MEND showed no hepatotoxicity and innate immune stimulation. Furthermore, in a DNA microarray analysis in liver and spleen tissue, less gene alternation was found for the PPD-MEND compared to that for the PEG-unmodified MEND due to less accumulation in liver and spleen.

The purpose of this study was to investigate the host response to systemically administered lipid nanoparticles (NPs) encapsulating plasmid DNA (pDNA) in the spleen using a DNA microarray. As a model for NPs, we used a multifunctional envelope-type nano device (MEND). Microarray analysis revealed that 1,581 of the differentially expressed genes could be identified by polyethylene glycol (PEG)-unmodified NP using a threefold change relative to the control. As the result of PEGylation, the NP treatment resulted in the reduction in the expression of most of the genes. However, the expression of type I interferon (IFN) was specifically increased by PEGylation. Based on the microarray and a pathway analysis, we hypothesize that PEGylation inhibited the endosomal escape of NP, and extended the interaction of toll-like receptor-9 (TLR9) with CpG-DNA accompanied by the production of type I IFN. This hypothesis was tested by introducing a pH-sensitive fusogenic peptide, GALA, which enhances the endosomal escape of PEGylated NP. As expected, type I IFN was reduced and interleukin-6 (IL-6) remained at the baseline. These findings indicate that a carrier design based on microarray analysis and the manipulation of intracellular trafficking constitutes a rational strategy for reducing the host immune response to NPs.