Construction Of Multi-responsive Gene Vector Via Layer-by-Layer Assembly

Nonviral vectors for gene therapy have received significant attention due to their potential advantages such as improved biosafety, low cytotoxicity and facile manufacturing, so scientists always hope to find a carrier with high safety and high efficiency and achieve breakthrough in gene therapy. In this work, we have developed a novel approach to prepare a controlled magnetic target gene carrier with magnetic Fe₃O₄ nanoparticles as core and PEG segment as corona via a combination of layer-by-layer (LbL) assembly and shell-crosslinking. Magnetic nanoparticles (MNPs) were first modified by 3-methacryloxy propyl trimethoxysilane (MPS) on their surface, and then grafted with poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) via radical polymerization. The resulting MNPs with polycationic groups were used to complex with DNA through LbL assembly, involving four steps: (1) the binding of DNA to the polycation PDMAEMA on the surface of MNPs; (2) the produced particles in Step 1 with negative charge interacting with additional polycation PDMAEMA homopolymer, leading to a positive charge surface; (3) using carboxyl group (-COO-) of poly(acrylic acid) in a diblock copolymer (MePEG2000-b-PMAASH) as polyanion, which has partial mercapto groups (-SH) in poly(acrylic acid) segment, to complex with the particles produced in Step 2; (4) the shell of the composite nanoparticle was crosslinked by oxidizing the -SH groups of the MePEG2000-b-PMAASH to form disulfide linkage (S-S). All the processes of LbL were investigated by agarose gel retardation assay and zeta potential measurements. The average particle sizes of the complexes in each step were determined by dynamic light scattering (DLS). And MTT assay was carried out to evaluate the cytotoxicity of the final complexes. The results indicate that the polyions/DNA magnetic nanoparticles have excellent properties and potential applications in nonviral polymeric gene carriers. Surface modification and functionalization of nanoparticles can satisfy the needs of many kinds of materials. In this work, we combine Atom Transfer Radical Polymerization (ATRP) with"Click"reaction to modify the particle surface with polymers like PDMAEMA to obtain some functions. First, Fe₃O₄ nanoparticles with SiO₂ shell (Fe₃O₄@SiO₂ nanoparticles) were prepared via sol-gel method and PDMAEMA with alkynyl tail was prepared by ATRP. Second, Fe₃O₄@SiO₂ nanoparticles were surface modified with azide group by silanization reaction. Finally, PDMAMEA was grafted onto the surface of Fe₃O₄@SiO₂ nanoparticles by"Click"reaction. 1HNMR spectra conformed that the ATRP initiator and PDMAEMA with alkynyl group were successfully prepared. From TEM graphs and FT-IR spectra, we can clearly see that uniform Fe₃O₄@SiO₂ nanoparticles were successfully prepared and PDMAEMA was successfully grafted onto the particle surface. With this kind of method, efficient surface modification of nanoparticles can be performed to obtain special functions, by which the needs of many kinds of materials in different fields can be satisfied.