Systematic Study of a Library of PDMAEMA-Based, Superparamagnetic Nano-Stars for the Transfection of CHO-K1 Cells

Abstract

The introduction of the DNA into mammalian cells remains a challenge in gene delivery, particularly in vivo. Viral vectors are unmatched in their efficiency for gene delivery, but may trigger immune responses and cause severe side-reactions. Non-viral vectors are much less efficient. Recently, our group has suggested that a star-shaped structure improves and even transforms the gene delivery capability of synthetic polycations. In this contribution, this effect was systematically studied using a library of highly homogeneous, paramagnetic nano-star polycations with varied arm lengths and grafting densities. Gene delivery was conducted in CHO-K1 cells, using a plasmid encoding a green fluorescent reporter protein. Transfection efficiencies and cytotoxicities varied systematically with the nano-star architecture. The arm density was particularly important, with values of approximately 0.06 arms/nm2 yielding the best results. In addition, a certain fraction of the cells became magnetic during transfection. The gene delivery potential of a nano-star and its ability to render the cells magnetic did not have any correlations. End-capping the polycation arms with di(ethylene glycol) methyl ether methacrylate (PDEGMA) significantly improved serum compatibility under transfection conditions; such nano-stars are potential candidates for future in vivo testing.

Transient Destabilization of Biological Membranes Contributes to the Superior Performance of Star-Shaped PDMAEMA in Delivering pDNA

“… 5 − 7 In recent years, we and other researchers have demonstrated the potential of poly(2-( N , N ′-dimethylamino)ethyl methacrylate) (PDMAEMA) as an alternative polycationic gene therapy vector. 8 − 13 …”

Amphiphilic Graft Copolymers Capable of Mixed-Mode Interaction as Alternative Nonviral Transfection Agents

“…A similar behavior has previously been described for graft copolymers and nanostar polycations with varied arm lengths and grafting densities. 10,25 Previously published data also showed that negatively charged polycation/ DNA complexes are less condensed, leading to the formation of larger particles. 49,50 In case of the l-PDMAEMA20, polyplexes with larger hydrodynamic radii were indeed obtained under otherwise identical experimental conditions (Table 3), suggesting that the introduced P(CL-co-MPC) domains in the PPxDy copolymers increase the binding affinity toward DNA and therefore should favor the formation of more condensed structures as reviewed in the past 51,52 and as hypothesized in one of our previous publications.…”

“…The experiment was performed at least twice for each material. The correlation coefficient, rho, was calculated according to the nonparametric Spearman correlation statistic test (MYSTAT 12.0, Systat software Inc., San Jose, CA, USA, 2007) as previously described 10 and used to estimate correlations between data sets.…”

“…However, both have weaknesses; for instance, they are not biodegradable and they are highly cytotoxic, while their gene delivery capability is limited compared to the viral vectors. − In this context, it has been shown that in case of linear polymers the transfection efficiency but also the cytotoxicity increase upon increasing the molecular weight. The higher charge density of the long cationic chains that enables disruptive electrostatic interactions with the cellular membranes has been hypothesized as a possible cause. − Reducing the charge density may thus be a useful strategy to reduce toxicity. , In addition, several groups, including our own, have shown that nonlinear structures (stars, dendrimers, grafts) are at least as efficient and are less cytotoxic than the corresponding linear polymers of similar molecular weight. , …”

Double thermoresponsive block–random copolymers with adjustable phase transition temperatures: From block‐like to gradient‐like behavior

“…Obviously, also the onset of the cargo's temperature‐induced release – for example by hyperthermia – could be adjusted by the copolymer composition according to the specific requirements. P(APi‐ co ‐APy) containing block–random copolymers might thus be promising materials for nanoscale “on‐demand” delivery systems, besides other interesting applications.…”