Abstract: Layered double hydroxide (LDH)@SiO₂ nanoparticles were developed as a delivery carrier for the plasmid DNA expressing the Newcastle disease virus F gene. The LDH was hydrotalcite-like materials. The plasmid DNA encapsulated in the LDH@SiO₂ nanoparticles (pFDNA-LDH@SiO₂-NPs) was prepared by the coprecipitation method, and the properties of pFDNA-LDH@SiO₂-NPs were characterized by transmission electron microscopy, zeta potential analyzer, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The results demonstrated that the pFDNA-LDH@SiO₂-NPs had a regular morphology and high stability with a mean diameter of 371.93 nm, loading capacity of 39.66%±0.45%, and a zeta potential of +31.63 mV. A release assay in vitro showed that up to 91.36% of the total plasmid DNA could be sustainably released from the pFDNA-LDH@SiO₂-NPs within 288 hours. The LDH@SiO₂ nanoparticles had very low toxicity. Additionally, their high transfection efficiency in vitro was detected by fluorescent microscopy. Intranasal immunization of specific pathogen-free chickens with pFDNA-LDH@SiO₂-NPs induced stronger cellular, humoral, and mucosal immune responses and achieved a greater sustained release effect than intramuscular naked plasmid DNA, and the protective efficacy after challenge with the strain F₄₈E₉ with highly virulent (mean death time of chicken embryos ≤60 hours, intracerebral pathogenicity index in 1 -day-old chickens >1.6) was 100%. Based on the results, LDH@SiO₂ nanoparticles can be used as a delivery carrier for mucosal immunity of Newcastle disease DNA vaccine, and have great application potential in the future.
Keywords: LDH@SiO₂ nanoparticles, Newcastle disease, mucosal immunity, Cytotoxicity, IgA