Microscopic insight into the DNA condensation process of a zwitterion‐functionalized polycation

Abstract

Zwitterion-functionalized polycations are ideal gene carriers with long circulation, high cellular uptaking and low cell viability. However, the trade-off between the DNA condensation efficiency and the cell viability must be addressed. The purpose of this study is to provide a microscopic insight into the DNA condensation process and to explore the effect of a zwitterionic block of zwitterion-functionalized polycation, which is of great significance in designing novel gene delivery systems. Poly[2-(dimethylamino)ethyl methacrylate-b-(sulfobetaine methacrylate)] (PDMAEMA-b-PSBMA) copolymers were synthesized and used as the model systems. Different from the conventional concept that the PSBMA zwitterionic block act only as the "stealthy" groups, the subtle differences in physical and colloidal characteristics between the polycation/DNA polyplexes show that the PSBMA segment is capable of wrapping DNA attributed to the quaternary ammonium cations, without compromising the DNA condensation capability. On the other hand, the incorporation of PSBMA block reduces the surface charge of the polyplexes, which substantially result in the inefficient transfection and the reduced cytotoxicity.

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

“…No statistically relevant differences were observed between the plateau values of the different nano-stars. Similar values, i.e., maximum zeta potentials around 20 mV, have previously been reported for other polycationic transfection agents [23]. Most polyplexes were already positively charged at the lowest investigated N/P-ratio, i.e., N/P 5.…”

“…The effect was most pronounced for P1 (0.006 arm per nm 2 ) and P2 (0.011 arm per nm 2 ), while the behavior of the polyplexes formed with P3 (0.024 arm per nm 2 ) already approached that of the polyplexes formed with the middle arm density nano-stars P4 (0.054 arm per nm 2 ) and P5 (0.064 arm per nm 2 ). Middle, but also high arm density nano-stars (P6–P10) formed smaller polyplexes with hydrodynamic radii ≤ 300 nm, a size that is considered suitable for endocytosis and transfection [23]. The molar mass of the nano-star, on the other hand, had little influence on the hydrodynamic radius of the ensuing polyplex, for example, polyplexes formed with P10 ( M n 172,466 kg/mol) were smaller than those formed with P5 ( M n 12,470 kg/mol).…”

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

“…It has been demonstrated that dense polyplexes with positive net charge and sizes below 300 nm are most easily internalized by cells. 41,42 The ζ-potentials of the free polymers were measured for the dispersions in ultrapure water and the culture medium Opti-MEM. For the corresponding polyplexes, the ζ-potentials were determined after dilution with Opti-MEM (serum-free) or R10 (serum-containing) culture media to mimic transfection conditions.…”

“…Size and surface charge (ζ-potential) are relevant in polyplexes intended for gene delivery, as they are related to cytotoxicity, cellular uptake, and transfection efficiency. It has been demonstrated that dense polyplexes with positive net charge and sizes below 300 nm are most easily internalized by cells. , …”

Development of poly(ethyleneimine) grafted amphiphilic copolymers: Evaluation of their cytotoxicity and ability to complex DNA

“…These properties, which are related to polymer-DNA binding affinity, influence the cytotoxicity, and transfection efficiency of the complexes, 32,33 taking into account that positively charged particles with sizes below 300 nm are more easily internalized by cells. 34,35 The ζ potential values of the polyplexes were measured as a function of the N/P ratio after their formation in HBG solution and their subsequent dilution with OptiMEM (Figure 7). Although the surface charge increased with the N/P ratio, the average values remained negative for all copolymers, except for PP6L3 at the highest N/P ratios.…”