Multilayered polyion complexes with dissolvable silica layer covered by controlling densities of cRGD-conjugated PEG chains for cancer-targeted siRNA delivery

Bioinspired Silicification of mRNA-Loaded Polyion Complexes for Macrophage-Targeted mRNA Delivery

In vitro transcribed messenger RNA (mRNA) delivery to macrophages is a promising therapeutic modality for inflammatory diseases because it can modulate the immunological activity of macrophages. However, efficient macrophage-targeted mRNA delivery remains challenging. Herein, we fabricated silica-coated polyion complexes (PICs), termed SilPICs, via bioinspired silicification for stable encapsulation of mRNA and scavenger receptor (SR)-mediated macrophage targeting. Silica coating was readily performed by simply mixing mRNA-loaded PICs with tetramethyl orthosilicate in aqueous media at 25 °C. The silica shell formation was verified by a slight increase in size (∼18 nm), a conversion of ζ-potential from positive (+22 mV) to negative (-23 mV), the peak appearance derived from silanol groups and siloxane bonds in the IR spectra, and elemental analyses by scanning transmission electron microscopy-energy-dispersive X-ray spectrometry (STEM-EDS). The silica shell efficiently protected the mRNA payload from enzymatic degradation in a fetal bovine serum-containing medium. Meanwhile, the reversibility of the silica shell allowed mRNA release from SilPICs after silica dissolution into silicic acids under diluted conditions. Furthermore, SilPICs elicited 20-fold higher mRNA transfection efficiency in the macrophage cell line RAW264.7 compared to noncoated PICs, presumably due to the facilitated cellular internalization by the silica shell. These enhancements were compromised in the RAW264.7 cells incubated with dextran sulfate and poly(inosinic acid) as inhibitors of SR type A1 and were not observed in cultured CT26 colon cancer cells, which are SR-negative cells. Collectively, SilPIC is a promising mRNA delivery vehicle with both mRNA protectability and macrophage targetability.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Increase in the apparent intercalation ability of a platinum complex via multivalency by installation into the sidechain of a graft copolymer and observation of structural changes in the intercalated DNA

Metal complexes with planar structures have been utilized as DNA intercalators that can be inserted into the base pairs of DNA strands, and have potential applications in DNA-targeting drug therapies. When designing the intercalator metal complexes, controlling their interactions with DNA is important, and has been performed by modifying the chemical structure of the metal ligand. Herein, we designed a graft copolymer segment having Pt complexes with bipyridine and poly(ethylene glycol) (p(PEGMA-co-BPyMA-Pt)) as another strategy to control the interaction with DNA via a multivalent effect. The p(PEGMA-co-BPyMA-Pt) increased not only the binding constant as one macromolecule but also the apparent binding constant per intercalator unit compared to the Pt complex with bipyridine (BPy-Pt). Moreover, p(PEGMA-co-BPyMA-Pt) induced a larger change in DNA structure using lower amounts of Pt than BPy-Pt. These observed properties of p(PEGMA-co-BPyMA-Pt) suggest that grafting intercalators on polymer segments is a promising approach for designing novel types of intercalators.

Pt complexes increase their apparent binding constant by grafting on sidechains of polymer segments via multivalent effect.

Selective delivery of PLXDC1 small interfering RNA to endothelial cells for anti-angiogenesis tumor therapy using CD44-targeted chitosan nanoparticles for epithelial ovarian cancer

Angiogenesis plays an essential role in the growth and metastasis of tumor cells, and the modulation of angiogenesis can be an effective approach for cancer therapy. We focused on silencing the angiogenic gene PLXDC1 as an important factor for anti-angiogenesis tumor therapy. Herein, we developed PLXDC1 small interfering siRNA (siRNA)-incorporated chitosan nanoparticle (CH-NP/siRNA) coated with hyaluronic acid (HA) to target the CD44 receptor on tumor endothelial cells. This study aimed to improve targeted delivery and enhance therapeutic efficacy for tumor anti-angiogenesis. The HA-CH-NP/siRNA was 200 ± 10 nm in size with a zeta potential of 26.4 mV. The loading efficiency of siRNA to the HA-CH-NP/siRNA was up to 60%. The selective binding of HA-CH-NP/siRNA to CD44-positive tumor endothelial cells increased by 2.1-fold compared with that of the CD44 nontargeted CH-NP/siRNA. PLXDC1 silencing by the HA-CH-NP/siRNA significantly inhibited tumor growth in A2780 tumor-bearing mice compared with that in the control group (p < .01), and mRNA expression of PLXDC1 was significantly reduced in the HA-CH-NP/siRNA-treated group. Furthermore, treatment with HA-CH-NP/siRNA resulted in significant inhibition of cell proliferation (p < .001), reduced microvessel density (p < .001), and increased cell apoptosis (p < .001). This study demonstrates that HA-CH-NP/siRNA is a highly selective delivery platform for siRNA, and has broad potential to be used in anti-angiogenesis tumor therapy.