IntroductionThere exist two main approaches for the functionalization of nanoparticles (NPs) with polymer chains fixed on the NPs' surface. The "grafting-to" method is performed by utilizing polymers bearing suitable functional end groups (anchor groups), which are able to bind to the surface of the particle. Alternatively, the "grafting-from" approach can be used to obtain core-shell nanoparticles. In this case, the initiating moiety is immobilized on the nanoparticle surface and the polymerization takes place directly from the surface. 1,2 We present the synthesis of core-shell NPs via the grafting-from approach utilizing a dopamine based ATRP initiator. Dopamine is considered to be a robust anchor for iron oxide surfaces in aqueous media. Grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) via surface-initiated ATRP yielded dual responsive core-shell NPs being responsive to temperature and pH. Due to the great potential of cationic polymers for non-viral gene delivery the hybrid material was further investigated related to biotechnical applications. The cytotoxicity and the efficiency as transfection reagent were studied under standard conditions and compared to the "gold standard" poly(ethylene imine), PEI.

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.

The synthesis of galactose-displaying core-shell nanospheres exhibiting both fluorescent and magnetic properties by grafting a glycocopolymer consisting of 6-O-methacryloylgalactopyranose (MAGal) and 4-(pyrenyl)butyl methacrylate (PyMA) onto magnetic silica particles via thiol-ene chemistry is reported. Magnetization measurements indicated that neither the encapsulation of the iron oxide particles into silica nor the grafting of the glycocopolymer chains had a significant influence on the superparamagnetic properties. This not only simplifies the purification of the particles but may facilitate the use of the particles in applications such as hyperthermia or magnetic resonance imaging (MRI). Furthermore, the hydrophilic glycopolymer shell provided solubility of the particles in aqueous medium and enabled the uptake of the particles into the cytoplasm and nucleus of lung cancer cells via carbohydrate-lectin recognition effects.

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The versatility of polymer and hybrid systems containing the polycation PDMAEMA, especially in the star-shaped topology, is reviewed. Different complexation schemes are addressed, including the use of stimuli-responsive counterions. This leads to the use of PDMAEMA stars for nucleotide transfection or advanced hydrogel formulations. GwieŸdzisty poli(metakrylan 2-dimetyloaminoetylu) i jego pochodne -nowe w³aoeciwooeci i kierunki zastosowañStreszczenie: Artyku³ stanowi przegl¹d literaturowy dotycz¹cy w³aoeciwooeci i zastosowania poli(metakrylanu 2-dimetyloaminoetylu) (PDMAEMA) i jego pochodnych. Przedstawiono wszechstronnooeae bazowego polimeru oraz uk³adów hybrydowych zawieraj¹cych polikation PDMAEMA, zw³aszcza o gwieŸdzistej topologii. Omówiono mo¿liwooeci wykorzystania wra¿liwooeci polimeru na zmiany temperatury i pH roztworu, a tak¿e ró¿ne schematy kompleksowania z udzia³em przeciwjonów reaguj¹cych na wspomniane bodŸce. GwieŸdziste pochodne PDMAEMA mog¹ znaleŸae zastosowanie w terapii genowej do transfekcji nukleotydów, jak równie¿ do wytwarzania zaawansowanych preparatów hydro¿elowych.S³owa kluczowe: polimer reaguj¹cy na bodŸce, polimer gwieŸdzisty, micelizacja, transfekcja genów, hydro¿el, hybrydy. 66 2014, , 59 nr 1