Facile Synthesis Of Multifunctional Nanocomposites For Efficient Dual-modal T₁ And T₂ Magnetic Resonance Imaging And Gene Delivery

ObjectiveTo prepare a multifunctional Fe₃O₄@PEI@DTPA-Gd nanocomposite and to test its feasiability as an efficient dual-modal T₁ and T₂ MRI contrast agent and gene delivery vector.MethodsPEI-coated Fe₃O₄ nanoparticles were synthesized using a hydrothermal method, then conjugated with DTPA,and further coordinated with Gd³⁺ions to form Fe₃O₄@PEI@DTPA-Gd nanocomposites.In vitro magnetic resonance imaging was conducted to study the T₁ and T₂ weighted imaging capabilities of the nanocomposites.Prussian blue staining and cell magnetic resonance imaging experiments were performed to study the uptake of nanocomposites by tumor cells.The biocompatibility of the nanocomposites was studied by MTT method,Hoechst 33342/PI staining method and HE staining of biological tissue sections.The in vitro gene transfection efficiency mediated by Fe₃O₄@PEI@DTPA-Gd nanocomposites was evaluated by transfecting a plasmid DNA encoding GFP into SH-SY5Y and HepG2 cells.Results:1.Successfully synthesis of Fe₃O₄@PEI@DTPA-Gd nanocompositesTransmission electron microscopy?TEM?observations showed that the synthesized nanocomposites had a relatively unifom morphology.The zeta potentials of Fe₃O₄@PEI,Fe₃O₄@PEI@DTPA and Fe₃O₄@PEI@DTPA-Gd nanocomposites were 48.1 mV?19.8mV and 31.2mV,indicating that the reaction in each step was successful.The inductively coupled plasma analyses?ICP?result showed that the mass ratio of Gd/Fe of Fe₃O₄@PEI@DTPA-Gd nanocomposites was 1:32.The thermogravimetric analysis?TGA?result indicated that the content of Gd in the nanocomposites was quantified to be 1.80%.2.Magnetic property of Fe₃O₄@PEI@DTPA-Gd nanocompositesMagnetic properties of the nanocomposites were analyzed by vibrating sample magnetometer?VSM?.It was found that the saturated magnetization of Fe₃O₄@PEI@DTPA-Gd nanocomposites was 72.91 emu/g,the remanence and coercivity were nearly zero,suggesting that Fe₃O₄@PEI@DTPA-Gd nanocomposites exhibited superparamagnetism.The longitudinal relaxivity?R₁?and transverse relaxivity?R₂?of Fe₃O₄@PEI@DTPA-Gd nanocomposites were 4.7 mM^-1s^-1?132.82mM^-1s^-1,respectively,suggesting that the nanocomposites had good T₁ and T₂ imaging effects.3.Fe₃O₄@PEI@DTPA-Gd nanocomposites have good MR imaging effects of tumor cells in both T₁ and T₂ dual modePrussian blue staining results indicated that the Fe₃O₄@PEI@DTPA-Gd nanocomposites could be entered into both HepG2 cells and SH-SY5Y cells,and mainly located into cytoplasm.In cellular MR images,it can be seen that both T₁ and T₂ signals of the cells were changed in a concentration-dependent manner,suggesting the good imaging effects of Fe₃O₄@PEI@DTPA-Gd nanocomposites.4.Fe₃O₄@PEI@DTPA-Gd nanocomposites efficiently deliver plasmid to cellsFe₃O₄@PEI@DTPA-Gd nanocomposites and GFP complex were successfully prepared.Both the results of agarose gel electrophoresis and DNA content analysis showed that the Fe₃O₄@PEI@DTPA-Gd nanocomposites had high binding capacity when the mass ratio of NP to DNA was larger than 30:1.In HepG2 cells and SH-SY5Y cells,GFP plasmid were tansfected successfully and the transfection efficiency of plasmid DNA mediated by Fe₃O₄@PEI@DTPA-Gd nanocomposites were 28.53%and 10.7%,respectively.5.Fe₃O₄@PEI@DTPA-Gd nanocomposites have good biocompatibilityMTT results indicated that both SH-SY5Y cells and HepG2 cells exposed to Fe₃O₄@PEI@DTPA-Gd nanocomposites exhibited high cell viability after 72 h co-incubation.The results of Hoechst 33342 and PI staining methods showed that the apoptosis rates and death rates had no significant difference with control group.HE staining of biological tissue sections showed that the major organs from the experimental group rats injected with Fe₃O₄@PEI@DTPA-Gd nanocomposites appeared no obvious side effects such as fibrosis and vacuoles compared with the control group rats injected with PBS.Above results indicated that the Fe₃O₄@PEI@DTPA-Gd nanocomposites had good biocompatibility.Conclusions:Fe₃O₄@PEI@DTPA@Gd nanocomposites with good biocompatibility,high R₁ and R₂values,high DNA loading capacity and gene transfection efficiency were successfully prepared,which can be utilized as a potential candidate for MRI guided clinical diagnosis and gene delivery guided therapy.