PDMAEMA-Grafted Core–Shell–Corona Particles for Nonviral Gene Delivery and Magnetic Cell Separation

Abstract

Monodisperse, magnetic nanoparticles as vectors for gene delivery were successfully synthesized via the grafting-from approach. First, oleic acid stabilized maghemite nanoparticles (γ-Fe2O3) were encapsulated with silica utilizing a reverse microemulsion process with simultaneous functionalization with initiating sites for atom transfer radical polymerization (ATRP). Polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from the core-shell nanoparticles led to core-shell-corona hybrid nanoparticles (γ-Fe2O3@silica@PDMAEMA) with an average grafting density of 91 polymer chains of DP(n) = 540 (PDMAEMA540) per particle. The permanent attachment of the arms was verified by field-flow fractionation. The dual-responsive behavior (pH and temperature) was confirmed by dynamic light scattering (DLS) and turbidity measurements. The interaction of the hybrid nanoparticles with plasmid DNA at various N/P ratios (polymer nitrogen/DNA phosphorus) was investigated by DLS and zeta-potential measurements, indicating that for N/P ≥ 7.5 the complexes bear a positive net charge and do not undergo secondary aggregation. The hybrids were tested as transfection agents under standard conditions in CHO-K1 and L929 cells, revealing transfection efficiencies >50% and low cytotoxicity at N/P ratios of 10 and 15, respectively. Due to the magnetic properties of the hybrid gene vector, it is possible to collect most of the cells that have incorporated a sufficient amount of magnetic material by using a magnetic activated cell sorting system (MACS). Afterward, cells were further cultivated and displayed a transfection efficiency of ca. 60% together with a high viability.

Polycationic star polymers with hyperbranched cores for gene delivery

“…Increasing N/P from 1 to 16 caused a change in the R h 90° of approximately 70 nm. A similar trend was observed by Mueller et al [ 24] observed an increase in size for nanoparticles with a magnetic core, silica shell and PDMAEMA corona complexed with plasmid DNA pEGFP-N1 (4.7 kilobase pair). They assumed bridging of two hybrid nanoparticles with one pDNA.…”

“…To discuss the results of the biological tests, the fact that the PDMAEMA stars are pH sensitive in water [22,24,45] should be taken into consideration. At acidic pH, the tertiary amino groups in the arms are completely charged.…”

“…Tam et al grafted DMAEMA onto four arm poly(ethylene oxide) [19,20] or onto C 60 -fullerene [21]. Different inorganic cores have also been applied to obtain stable star nanoparticles for gene therapy, including cores made of silica [22], silsesquioxanes [18,23] and γ-Fe 2 O 3 [24].…”

Influence of Polyplex Formation on the Performance of Star-Shaped Polycationic Transfection Agents for Mammalian Cells

“…In particular these were: (PDMAEMA 230 ) 20 [15]: silsesquioxane nanoparticle core; stock solution: 183 mg/mL in sterile Milli Q water (1150 mM N-residues). Poly(1,2-butadiene)-block-PDMAEMA (B 290 D 240 ) [15,19]: polybutadiene hydrophobic core (290 monomeric units); stock solution: 10.7 mg/mL in sterile PBS (48.3 mM N residues); molecules form star-shaped micelles in aqueous solution.…”

“…Poly(1,2-butadiene)-block-PDMAEMA (B290D240) [15,19]: polybutadiene hydrophobic core (290 monomeric units); stock solution: 10.7 mg/mL in sterile PBS (48.3 mM N residues); molecules form star-shaped micelles in aqueous solution. γ-Fe2O3@silica@(PDMAEMA540)91 [20]: silica-coated γ-Fe2O3-nanoparticle core; stock solution: 1.75 mg/mL in sterile Milli Q water (31.1 mM N-residues). In addition, a γ-Fe2O3@silica@(PDMAEMA1037)46 (stock solution: 4.5 mg/mL, 19.2 mM N-residues) was prepared analogously to γ-Fe2O3@silica@(PDMAEMA540)91.…”