Zwitterionic Polymer-Decorated Lipid Nanoparticles for mRNA Delivery in Mammalian Cells.

Lipid nanoparticles (LNPs) play a key role in the effective transport of mRNA into cells for protein translation. Despite the stealthiness of poly(ethylene glycol) (PEG) that helps protect LNPs from protein absorption and blood clearance, the generation of anti-PEG antibodies resulting in PEG allergies remains a challenge for the development of an mRNA vaccine. Herein, a non-PEG lipid was developed by conjugating 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) with an antifouling zwitterionic polymer, poly(2-methyacryloyloxyethyl phosphorylcholine) (PMPC), of different chain lengths. The PMPC-LNPs formulated from DPPE-PMPC were spherical (diameter ≈ 144-255 nm), neutral in charge, and stable at 4 °C for up to 28 days. Their fraction of stealthiness being close to 1 emphasized the antifouling characteristics of PMPC decorated on LNPs. The PMPC-LNPs were nontoxic to HEK293T cells, did not induce inflammatory responses in THP-1 cells, and exhibited an mRNA transfection efficiency superior to that of PEG-LNPs. This work demonstrated the potential of the developed zwitterionic polymer-conjugated LNPs as promising mRNA carriers.

Pyrene-Labeled and Quaternized Chitosan: Synthesis, Characterization, and Its Potential Application for Fluorescently Trackable Nucleic Acid Delivery into Cells.

A chitosan derivative (Pyr-CS-HTAP) having pyrene (Pyr) and N-[(2-hydroxyl-3-trimethylammonium)] propyl (HTAP) units conjugated at C6 and C2 positions, respectively, was synthesized and characterized. Dynamic light scattering and scanning electron microscopy revealed that Pyr-CS-HTAP self-assembled into spherical nanoparticles with a hydrodynamic diameter of 211 ± 5 nm and a ζ-potential of +49 mV. The successful binding of Pyr-CS-HTAP with nucleic acid was ascertained by fluorescence resonance energy-transfer analysis and gel electrophoresis. Pyr-CS-HTAP facilitated the cellular uptake of nucleic acid up to 99%. Co-localization analysis using fluorescence microscopy revealed the endosomal escape of the Pyr-CS-HTAP/nucleic acid complexes and the successful release of the nucleic acid cargoes from the polyplexes into the nucleus. It is strongly believed that Pyr-CS-HTAP can potentially be developed into a fluorescently trackable gene delivery system in the future.

Gold Nanorods Stabilized by Biocompatible and Multifunctional Zwitterionic Copolymer for Synergistic Cancer Therapy.

A zwitterionic copolymer between methacryloyloxyethyl phosphorylcholine (MPC) and methacrylic acid (MA), PMAMPC is introduced as a potential versatile polymeric stabilizer for gold nanorods (AuNRs). The MA units in the copolymer serve as built-in feature for multiple functionalization, namely introducing additional thiol groups as active sites for binding with the AuNRs and conjugating with doxorubicin (DOX), an anticancer drug via acid-labile hydrazone linkage. The MPC units, on the other hand, provide biocompatibility and antifouling characteristics. The chemically modified PMAMPC can act as an effective stabilizer for AuNRs yielding PMAMPC-DOX-AuNRs with a fairly uniform size and shape with good colloidal stability. In vitro cytotoxicity suggested that PMAMPC can not only improve the AuNRs biocompatibility, but also decrease DOX toxicity to a certain extent. The PMAMPC-DOX-AuNRs were efficiently internalized inside cancer cells and localized in lysosomes, where DOX was presumably acid-triggered released as monitored by confocal laser scanning microscopic analysis and flow cytometry. Furthermore, the combined photothermal-chemo treatment of cancer cells using PMAMPC-DOX-AuNRs exhibited a higher therapeutic efficacy than either single treatment alone. These results suggested that the PMAMPC-DOX-AuNRs could potentially be applied in pH-triggered drug delivery for synergistic cancer therapy.