Biodegradable cyclen-based linear and cross-linked polymers as non-viral gene vectors

The Development of Functional Non-Viral Vectors for Gene Delivery

Gene therapy is manipulation in/of gene expression in specific cells/tissue to treat diseases. This manipulation is carried out by introducing exogenous nucleic acids, such as DNA or RNA, into the cell. Because of their negative charge and considerable larger size, the delivery of these molecules, in general, should be mediated by gene vectors. Non-viral vectors, as promising delivery systems, have received considerable attention due to their low cytotoxicity and non-immunogenicity. As research continued, more and more functional non-viral vectors have emerged. They not only have the ability to deliver a gene into the cells but also have other functions, such as the performance of fluorescence imaging, which aids in monitoring their progress, targeted delivery, and biodegradation. Recently, many reviews related to non-viral vectors, such as polymers and cationic lipids, have been reported. However, there are few reviews regarding functional non-viral vectors. This review summarizes the common functional non-viral vectors developed in the last ten years and their potential applications in the future. The transfection efficiency and the transport mechanism of these materials were also discussed in detail. We hope that this review can help researchers design more new high-efficiency and low-toxicity multifunctional non-viral vectors, and further accelerate the progress of gene therapy.

Zn(ii) coordination to cyclen-based polycations for enhanced gene delivery

Zn²⁺ coordination greatly improved the gene transfection efficiency of cyclen-based polycations.

First synthesis of orthogonally 1,7-diprotected cyclens

Six novel orthogonally 1,7-heterodiprotected cyclen derivatives have been prepared through an efficient and chromatography-free procedure.

Bio-reducible polycations from ring-opening polymerization as potential gene delivery vehicles

Bio-reducible polycations were prepared via ring-opening polymerization. These materials have relatively low molecular weights and cytotoxicity but have good DNA condensation ability, transfection efficiency and excellent serum tolerance.

A new high-capacity metal ion-complexing gel containing cyclen ligands

“Hairy” nano-scale objects cross-linked into a high-capacity metal-binding hydrogel.

Diol glycidyl ether-bridged low molecular weight PEI as potential gene delivery vehicles

PEI 600-based polymers were synthesized via ring-opening polymerization and exhibited much better transfection efficiency and biocompatibility than PEI 25 kDa.

Bioreducible cross-linked polymers based on G1 peptide dendrimer as potential gene delivery vectors

A series of cationic polymers based on low generation (G1) peptide dendrimer were synthesized with disulfide-containing linkages. The DNA binding abilities of the target polymers were studied by gel electrophoresis and fluorescence quenching assay. The bioreducible property of the disulfide-containing polymers P2 and P3 was also investigated in the presence of dithiothreitol (DTT). Results from dynamic light scattering (DLS) and transmission electron microscopy (TEM) assays reveal that these materials may condense DNA into nanoparticles with proper sizes and zeta-potentials. In vitro cell experiments show that compared to branched 25 KDa PEI, P2 and P3 may exhibit much higher gene transfection efficiency and lower cytotoxicity in both HEK293 and U-2OS cells. Additionally, polymer prepared from Michael addition gives better gene transfection ability, while polymer prepared from ring-opening reaction has better serum tolerance. Results indicate that these polymers might be promising non-viral gene vectors for their easy preparation, very low cytotoxicity, and good transfection efficiency.

Cyclen-based lipidic oligomers as potential gene delivery vehicles

A series of cyclen-based linear oligomers bearing hydrophobic long chains (lipopolymers Cy-LC, where Cy and LC represent cyclen-based linear backbone and hydrophobic long chain substituents, respectively) were designed and synthesized. The effects of type and degree of substitution (DS) of hydrophobic long chains on the transfection efficiency were systematically studied. The nitrogen atoms with relatively strong basicity on the cyclen ensure their good DNA binding ability, which was confirmed by gel retardation and ethidium bromide exclusion assays. Lipopolyplexes could be formed as nanoparticles with suitable sizes and zeta potentials for gene transfection. In vitro gene delivery experiments revealed that the linoleic acid (LIN) substituted material Cy-LIN has better transfection efficiency than 25 kDa polyethylenimine in the absence or in the presence of serum. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and hemolysis assays showed low cytotoxicity and good biocompatibility of the lipopolyplexes. Fluorescent labeled DNA was used to study the cellular uptake and intracellular distribution of transfected DNA. Flow cytometry results suggested that a long chain is necessary for efficient cellular uptake, and images from confocal laser scanning microscopy showed that after 4h transfection, most of the fluorescent labeled DNA accumulated in the perinuclear region, which was required for efficient gene expression. Moreover, it was also found that the DS of the hydrophobic moiety can adjust the balance between DNA binding ability and dissociation of polyplexes, significantly affecting the transfection efficiency.

Synthesis, Characterisation and Molecular Recognition of Novel Zn(II) Macrocyclic Complexes with Imidazole or Benzimidazole Pendants

Macrocyclic polyamine Zn(II) mononuclear and dinuclear complexes bearing imidazole or benzimidazole pendants have been synthesised and their binding constants determined by UV-Vis spectrometric titration. The binding ability of the complexes is stronger than that of the control materials with cytosine (Cyt). The recognition abilities of the dinuclear complexes for Cyt are much higher than that for the other bases or nucleosides (such as uracil, 5-hydroxymeyhyl uracil, adenosine, thymidine and uridine); the binding constants of the dinuclear complexes with m-xylyl or pyridyl as linkers are 25,360 and 22,550 dm3 mol−1 respectively.

Cyclam-based polymeric copper chelators for gene delivery and potential PET imaging

A series of reducible polycationic copper chelators (RPCs) based on 1,4,8,11-tetraazacyclotetradecane (cyclam) were synthesized by Michael addition. Molecular weight of the polycations was controlled by reaction stoichiometry and reaction conditions, resulting in polymers with molecular weights ranging from 4400 to 13 800. The cyclam moieties in the polycations retained their ability to form complexes with Cu(II). The presence of disulfide bonds in the polycations resulted in substantially lower cytotoxicity than control 25 kDa poly(ethyleneimine). RPC as well as their complexes with Cu(II) exhibited high transfection activity in vitro. The reported polycationic Cu(II) chelates represent promising nucleic acid delivery vectors with potential for future theranostic applications.