Poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline) star polymers with 3, 4 and 6 arms are synthesized from pluritriflate initiators. Characterization of the topology was achieved by NMR, SEC and kinetic studies. The initiation step of 2-ethyl-2-oxazoline being slow, heterogeneous star polymers in arm molar masses are obtained for low molar mass polymers. However, for both monomers, high molar mass homogeneous star polymers are obtained. A fast initiation is observed for the polymerization of 2-methyl-2-oxazoline, providing a control of the topology even at low molar mass. In the studied molar mass range, linear kinetic first order plots and linear molar mass as a function of conversion are obtained for both monomers, suggesting living polymerizations.
The synthesis of double hydrophilic block copolymers (DHBCs) containing a polyethylenimine (PEI) and a poly(2-alkyl-2-oxazoline) in two steps was investigated in this study. First, well-defined copolymers of poly(2-methyl-2-oxazoline)-b-poly(2-ethyl-2-oxazoline) (PMeOx-b-PEtOx) and poly(2-isopropyl-2-oxazoline)-b-poly(2-methyl-2-oxazoline) (PiPrOx-b-PMeOx) were synthesized. Then, their thermoresponsive properties were analyzed to obtain a selective hydrolysis of the PMeOx block. Concerning the PMeOx-b-PEtOx copolymers, no phase transiton was witnessed, and a selectivity appeared but was quite low regardless of the copolymer composition tested, while for the PiPrOx-b-PMeOx copolymers, a complete selective hydrolysis was achieved, allowing the synthesis of PiPrOx-b-PEI DHBCs due to micelles formations in the reactive media at high temperature. Thus, for different PiPrOx-b-PMeOx with varying composition, a MeOx unit hydrolysis degree higher than 90% was obtained with nearly no hydrolysis of the PiPrOx block, providing block copolymers suitable for gene transfer experiments. The reproducibility of the reaction was also demonstrated.
Background: Gene delivery is a promising technology for treating diseases linked to abnormal gene expression. Since nucleic acids are the therapeutic entities in such approach, a transfecting vector is required because the macromolecules are not able to efficiently enter the cells by themselves. Viral vectors have been evidenced to be highly effective in this context; however, they suffer from fundamental drawbacks, such as the ability to stimulate immune responses. The development of synthetic vectors has accordingly emerged as an alternative. Objectives: Gene delivery by using non-viral vectors is a multi-step process that poses many challenges, either regarding the extracellular or intracellular media. We explore the delivery pathway and afterwards, we review the main classes of non-viral gene delivery vectors. We further focus on the progresses concerning polyethylenimine-based polymer-nucleic acid polyplexes, which have emerged as one of the most efficient systems for delivering genetic material inside the cells. Discussion: The complexity of the whole transfection pathway, along with a lack of fundamental understanding, particularly regarding the intracellular trafficking of nucleic acids complexed to non-viral vectors, probably justifies the current (beginning of 2021) limited number of formulations that have progressed to clinical trials. Truly, successful medical developments still require a lot of basic research. Conclusion: Advances in macromolecular chemistry and high-resolution imaging techniques will be useful to understand fundamental aspects towards further optimizations and future applications. More investigations concerning the dynamics, thermodynamics and structural parameters of polyplexes would be valuable since they can be connected to the different levels of transfection efficiency hitherto evidenced.
Mimicking and extending the gating properties of biological pores is of paramount interest for the fabrication of membranes that could be used in filtration or drug processing. Here, we build a selective and switchable nanopore for macromolecular cargo transport. Our approach exploits polymer graftings within artificial nanopores to control the translocation of biomolecules. To measure transport at the scale of individual biomolecules, we use fluorescence microscopy with a zero-mode waveguide set up. We show that grafting polymers that exhibit a lower critical solution temperature creates a toggle switch between an open and closed state of the nanopore depending on the temperature. We demonstrate tight control over the transport of DNA and viral capsids with a sharp transition (∼1 °C) and present a simple physical model that predicts key features of this transition. Our approach provides the potential for controllable and responsive nanopores in a range of applications.
Gene delivery is now a part of the therapeutic arsenal for vaccination and treatments of inherited or acquired diseases. Polymers represent an opportunity to develop new synthetic vectors for gene transfer, with a prerequisite of improved delivery and reduced toxicity compared to existing polymers. Here, the synthesis in a two‐step's procedure of linear poly(ethylenimine‐b‐2‐isopropyl‐2‐oxazoline) block copolymers with the linear polyethylenimine (lPEI) block of various molar masses is reported; the molar mass of the poly(2‐isopropyl‐2‐oxazoline) (PiPrOx) block has been set to 7 kg mol−1. Plasmid DNA condensation is successfully achieved, and in vitro transfection efficiency of the copolymers is at least comparable to that obtained with the lPEI of same molar mass. lPEI‐b‐PiPrOx block copolymers are however less cytotoxic than their linear counterparts. PiPrOx can be a good alternative to PEG which is often used in drug delivery systems. The grafting of histidine moieties on the lPEI block of lPEI‐b‐PiPrOx does not provide any real improvement of the transfection efficiency. A weak DNA condensation is observed, due to increased steric hindrance along the lPEI backbone. The low cytotoxicity of lPEI‐b‐PiPrOx makes this family a good candidate for future gene delivery developments.
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