Multilayer Dual-polymer-coated Upconversion Nanoparticles For Multimodal Imaging And Serum-enhanced Gene Delivery

Objective To study the multi-layer dual-polymer coated upconversion nanoparticles(UCNP-PEG@2×PEI) for magnetic response imaging and upconversion luminescencecontrast agent.Methods1) Synthesize Gd3+-doped UCNP nanoparticles, which is then coated bypolyethylene glycol，polyethylenimine and poly acrylic acid to acquire high stability inphysiological solutions. And then, the exosyndromes of UCNP-PEG@2×PEI wereevaluated.2) The cytotoxicity of UCNP-PEG@2×PEI was evaluated by MTT assay.3)The multimodal images of MR T1-weighted images and UCL images were performedusing a series of UCNP-PEG@2×PEI solutions with different concentrations incubatedwith HeLa cells for4h in vitro.Results1) From the transmission electron microscopy (TEM) imaging, we found thatUCNP nanoparticles were serving as the core and after modifying two layers PEI，UCNP-PEG@2×PEI exhibited excellent stability in various physiological solutions. Zetapotentials and size distributions of UCNP-PEG@2×PEI suggested positively chargedPEI coating would make the polymer shell on UCNPs to be more condensed. The UCLintensity of UCNP-PEG@2×PEI was still high.2) In vitro cytotoxicity assay showed nosignificant cytotoxic response of cells even at high nanoparticles concentrations.3) MRimages and UCL images showed UCNP-PEG@2×PEI could serve as imaging probes for both optical and MR imaging and showed a concentration-dependent brightening effect.Conclusion UCNP-PEG@2×PEI which with two layers PEI coated on UCNPs, werestable in physiological environments and exhibited excellent positively charges andcondensed structure. In vitro study uncovered no obvious toxicity forUCNP-PEG@2×PEI nanoparticles. Besides, UCNP-PEG@2×PEI nanoparticles showedexcellent capacities of multimodal imaging. Therefore, UCNP-PEG@2×PEI could serveas novel imaging-trackable nano-vectors for tumor diagnosis. Objective The multi-layer dual-polymer coated upconversion nanoparticles serve asgene delivery vectors and serum-enhanced gene delivery.Methods1) To study the pDNA binding ability of UCNP-PEG@2×PEI and bare PEI, weuse gel electrophoresis assay. Appropriate amounts of UCNP-PEG@2×PEI and bare PEIpolymer were mixed with1g plasmid DNA at different N/P ratios (1,2,5,10,20), afterincubation for30min at room temperature, the samples were analyzed by0.8%agarosegel electrophoresis.2) In vitro EGFP plasmid transfection under serum-free conditions indifferent N/P ratios. Appropriate amounts of UCNP-PEG@2×PEI and bare PEI polymerwere mixed with EGFP plasmid and incubated for30min at room temperature beforebeing added into HeLa cells under serum-free conditions. Both confocal fluorescencemicroscopy and flow cytometry were employed to determine the EGFP transfectionefficiencies.3) In vitro EGFP plasmid transfection under serum-containing conditions inconsistent N/P ratio. Appropriate amounts of UCNP-PEG@2×PEI and bare PEI polymer were mixed with EGFP plasmid and incubated for30min at room temperature beforebeing added into HeLa cells under serum-containing conditions. Both confocalfluorescence microscopy and flow cytometry were employed to determine the EGFPtransfection efficiencies.Results1) UCNP-PEG@2×PEI and bare PEI both mixed with EGFP plasmid at the N/Pratio above5, significant retardation of plasmid moving in gel electrophoresis wereobserved.2) Under serum-free conditions, UCNP-PEG@2×PEI and bare PEI were ableto transfect HeLa cells with EGFP plasmid at N/P ratios from5to20, while thetransfection efficiencies of UCNP-PEG@2×PEI were significantly lower than that ofbare PEI at the same N/P ratio.3) Under serum-containing conditions, at the N/P ratio of10, the transfection efficiencies of UCNP-PEG@2×PEI increased obviously than barePEI.Conclusion Multi-layer dual-polymer coated upconversion nanoparticles could serve asnovel vectors for efficient gene delivery in vitro and potentially in vivo.