Search

Cationic polymers have shown great potential in the delivery of nucleic acids and proteins. In this study, a series of pyrimidine-based cationic polymers were synthesized via the Michael addition reaction from pyrimidine-based linkages and low molecular weight polyethyleneimine (PEI). The structure-activity relationship (SAR) of these materials in DNA and protein delivery was investigated. These materials could condense both DNA and protein into nanoparticles with proper sizes and zeta-potentials. In vitro experiments indicated that such polymers were efficient in transporting DNA and proteins into cells. Furthermore, the bioactivity of the genes and proteins encapsulated in these polymers were maintained during the delivery processes. Among the polymers, U-PEI600 synthesized from a uracil-containing linker and PEI 600 Da mediated comparable gene expression to PEI 25 kDa. Moreover, the activities of β-galactosidase delivered by U-PEI600 were well maintained after entering the cells. Evaluation using an immune response assay showed that the U-PEI600/OVA polyplex could stimulate greater production of immune factors with low cytotoxicity. Our study provides a strategy for the construction of cationic polymeric gene and cytosolic protein vectors with high efficiency and low toxicity.

The construction of efficient and low toxic non-viral gene delivery vectors is of great significance for gene therapy. Herein, two novel polycations were constructed via Michael addition from low molecular weight polyethylenimine (PEI) 600 Da and amino acid-containing linkages. Lysine and histidine were introduced for the purpose of improved DNA binding and pH buffering capacity, respectively. The ester bonds afforded the polymer biodegradability, which was confirmed by the gel permeation chromatography (GPC) measurement. The polymers could well condense DNA into nanoparticles and protect DNA from degradation by nuclease. Compared with PEI 25 kDa, these polymers showed higher transfection efficiency, lower toxicity, and better serum tolerance. Study of this mechanism revealed that the polyplexes enter the cells mainly through caveolae-mediated endocytosis pathway; this, together with their biodegradability, facilitates the internalization of polyplexes and the release of DNA. The results reveal that the amino acid-linked low molecular weight PEI polymers could serve as promising candidates for non-viral gene delivery.

Polycation carriers hold great potential in gene therapy. However, they usually suffer from obvious cytotoxicity and unsatisfactory transfection efficiency. In this report, a series of fluorobenzene substituted and thioacetal contained polycations (TAEA-S-xF) were prepared to explore novel alternatives for safe and efficient non-viral polymeric gene vectors. The reactive oxygen species (ROS)-responsive property of thioacetal moieties together with the fluorine effect were hope to bring the vector better performance in gene delivery process. These materials could efficiently condense DNA into nanoparticles with proper size and surface potential. The structure-activity relationship of these materials was systematically investigated, and the In vitro transfection results revealed that the amount of fluorine atoms on the linkage plays important role to ensure the transfection efficiency and serum tolerance. The ROS-responsive behavior was verified by NMR, gel electrophoresis experiment and dynamic light scattering (DLS) assay. Cytotoxicity assay results also suggest that these ROS-degradable polycations show good biocompatibility in response to higher ROS level in cancer cells. Among these fluorinated polymers, the one with the most fluorine atoms showed the best transfection efficiency, which was up to 54 times higher than polyethyleneimine (PEI) 25 kDa. Mechanism studies reveal that its better performance may come from good cellular uptake and endosome escape ability., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Carbon dots have attracted rapidly growing interest in recent years. In this report, we prepared two cationic polymer-derived carbon dots (Taea-CD and Cyclen-CD, collectively called C-dots) via a hydrothermal method. Transmission electron microscopy (TEM) results show that the C-dots were sphere-like and the size distribution was 1.8 ± 0.4 nm for Taea-CD and 5.4 ± 2 nm for Cyclen-CD. The C-dots emitted bright blue fluorescence under UV light (365 nm). Confocal laser scanning microscopy (CLSM) assay indicates that the C-dots-mediated transfection process could be detected in real time, and their tunable fluorescence emission under different wavelengths could satisfy varying requirements. Luciferase assay indicates that the transformation from the polymer to CD is an effective strategy to improve the transfection efficiency (TE) of the materials. Moreover, the C-dots also exhibit higher serum tolerance and cell viability than commercially available polyethyleneimine (PEI). These results demonstrate that the preparation of carbon dots from polymers is a promising method for developing multifunctional gene vectors with high TE and biocompatibility.

Fluorinated biomaterials have been reported to have promising features as non-viral gene carriers. In this study, a series of fluorinated polymeric gene carriers were synthesized via Michael addition from low molecular weight polyethyleneimine (PEI) and fluorobenzoic acids (FBAs)-based linking compounds with different numbers of fluorine atoms. The structure-activity relationship (SAR) of these materials was systematically investigated. SAR studies showed that fluorine could screen the positive charge of these polymers. However, this shielding effect of fluorine would endow fluorinated polymers with good balance between DNA condensation and release. In vitro transfection results suggested that these fluorinated polymers could mediate efficient gene delivery. Flow cytometry and confocal microscopy studies demonstrated that more efficient cell uptake could be achieved by fluorinated materials with more fluorine atoms. Cytotoxicity assays showed that these fluorinated materials exhibited very low cytotoxicity even at high mass ratios. This study demonstrates that FBA-based fluorinated biopolymers have the potential for practical application., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Synthetic polycations show great potential for the construction of ideal non-viral gene delivery systems. Several cationic polymers were synthesized by the epoxide ring-opening polymerization between diepoxide and various polyamines. Disulfide bonds were introduced to afford the polymers bio-reducibility, while the oxygen-rich structure might enhance the serum tolerance and biocompatibility. The polycations have much lower molecular weights than PEI 25 kDa, but still could well bind and condense DNA into nano-sized particles. DNA could be released from the polyplexes by addition of reductive DTT. Compared to PEI, the polycations have less cytotoxicity possibly due to their lower molecular weights and oxygen-rich structure. More significantly, these materials exhibit excellent serum tolerance than PEI, and up to 6 times higher transfection efficiency than PEI could be obtained in the presence of serum. The transfection mediated by was seldom affected even at a high concentration of serum. Much lower protein adsorption of polycations than PEI was proved by bovine serum albumin adsorption experiments. Flow cytometry also demonstrates their good serum resistance ability.

Routine clinical implementation of human gene therapy requires safe and efficient gene delivery methods. Linear biodegradable polyesters with carbon-carbon double bonds are prepared from unsaturated diacids and diols. Subsequent appending of low molecular weight PEI by Michael addition gives target cationic polymers efficiently. Agarose gel retardation and fluorescence quenching assays show that these materials have good DNA binding ability and can completely retard plasmid DNA at weight ratio of 0.8. The formed polyplexes have appropriate sizes around 275 nm and zeta-potential values about +20-35 mV. The cytotoxicities of these polymers assayed by MTT are much lower than that of 25 kDa PEI. In vitro transfection toward 7402, HEK293 and U-2OS cells show that polymer P1 may give dramatically higher transfection efficiency (TE) than 25 kDa PEI, especially in U-2OS cells, suggesting that such polymer might be promising non-viral gene vectors., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Rapid enzymatic degradation and fragmentation during DNA administration can result in limited gene expression, and consequently, poor efficacy. It is necessary to use novel vectors for DNA delivery. Herein, we aimed to design useful carriers for enhancing transfection efficiency (TE). These lipopolymers were prepared through Michael addition reactions from low-molecular-weight (LMW) polyethyleneimine (PEI) and linkers with three kinds of steroids. Agarose gel electrophoresis assay results displayed that the three lipopolymers could condense plasmid DNA well, and the formed polyplexes had appropriate sizes around 200–300 nm, and zeta potentials of about +25–40 mV. The results of in vitro experiments using HeLa, HEK293, and MCF-7 cells showed that these lipopolymers present higher TE than 25-kDa PEI, both in the absence and presence of 10% serum. Flow cytometry and confocal microscopy studies also demonstrated that these lipopolymer/DNA complexes present higher cellular uptake and intracellular distribution. The measurement of critical micelle concentration (CMC) revealed that these lipopolymers could form micelles, which are suited for drug delivery. All results suggest that the three materials may serve as hopeful candidates for gene and drug delivery in future in vivo applications. [ABSTRACT FROM AUTHOR]