Wen-Jing Yi

Linear polycations by ring-opening polymerization as non-viral gene delivery vectors.

For a clinically effective non-viral gene delivery system, a non-toxic and highly efficient vector is of great importance. A series of linear cationic polymers were synthesized by the ring-opening polymerization between diglycidyl ethers and diamines. Their structure-activity relationships as gene delivery vectors were systematically studied. Besides the amino groups with various densities, these polymers have uniform distribution of hydroxyl groups, which were formed in the polymerization and may benefit their biocompatibility and serum-tolerance. These polymers have good DNA binding ability and could condense DNA into nanoparticles with proper sizes and zeta-potentials. MTT assay revealed that polyplexes formed from title polymers have lower cytotoxicity than that derived from PEI. Most of the polymers have higher transfection efficiency than 25 kDa PEI in the in vitro transfection experiments. Polymers prepared from diglycidyl ethers with less or no N atom (2a and 2b) gave dramatically decreased TE, indicating that secondary amine on the backbone is highly required for efficient gene transfection, and compound 2 may be a good building block in the design of cationic polymers for gene delivery. More importantly, these polymers showed much better serum tolerance. Unlike PEI, the transfection mediated by P5 was seldom affected by the presence of 10% serum. Cellular uptake and intracellular distribution studies also confirmed the good performance of P5 in the transfection process with serum.

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.

Novel imidazole-functionalized cyclen cationic lipids: synthesis and application as non-viral gene vectors.

A series of novel 1,4,7,10-tetraazacyclododecanes (cyclen)-based cationic lipids bearing histidine imidazole group 10a-10e were synthesized. These amphiphilic molecules have different hydrophobic tails (long chain, cholesterol or α-tocopherol) and various type of linking groups (ether, carbamate or ester). These molecules were used as non-viral gene delivery vectors, and their structure-activity relationships were investigated. As expected, the imidazole group could largely improve the buffering capabilities comparing to cyclen. The liposomes formed from 10 and dioleoylphosphatidyl ethanolamine (DOPE) could bind and condense plasmid DNA into nanoparticles with proper size and zeta-potentials. Comparing with Lipofectamine 2000, the formed lipoplexes gave lower transfected cells proportion, but higher fluorescence intensity, indicating their good intracellular delivering ability. Furthermore, results indicate that transfection efficiency of the cationic lipids is influenced by not only the hydrophobic tails but also the linking group. The cyclen-based cationic lipid with α-tocopherol hydrophobic tail and an ester linkage could give the highest transfection efficiency in the presence of serum.

TACN-containing cationic lipids with ester bond: preparation and application in gene delivery.

A series of novel cationic lipids based on 1,4,7-triazacyclononane (TACN) with different hydrophobic chains were synthesized via the formation of a biodegradable ester bond. These lipids were found to have good buffering capacity at the pH range of 5.0-6.5, which is similar to that of the acidic endosomal compartments. The liposomes formed from these lipids and DOPE could condense DNA into nanoparticles with proper sizes. In vitro experiments showed moderate to good gene transfection efficiency of the formed lipoplexes. The structure-activity relationships of this type of lipids were discussed.

TACN-based cationic lipids with amino acid backbone and double tails: Materials for non-viral gene delivery

Cationic lipids have become an efficient type of non-viral vectors for gene delivery. In this Letter, four cationic lipids containing 1,4,7-triazacyclononane (TACN) headgroup, glutamic/aspartic acid backbone and dioleyl tails were designed and synthesized. The TACN headgroup gives these lipids excellent pH buffering capacities, which were higher than branched 25 kDa PEI. Cationic liposomes prepared from these lipids and DOPE showed good DNA affinity, and full DNA condensation was found at N/P ratio of 3 via agarose gel electrophoresis. The lipoplexes were characterized by dynamic light scattering (DLS) assay, which gave proper particle sizes and zeta-potentials for transfection. In vitro gene transfection results in two cell lines reveal that TAN (with aspartic acid and amide bond in the structure) shows the best transfection efficiency, which is close to commercially available transfection agent Lipofectamine 2000.

Diol glycidyl ether-bridged cyclens: preparation and their applications in gene delivery.

Polymeric 1,4,7,10-tetraazacyclododecanes (cyclens) using diol glycidyl ether with different chain length as bridges (5a-e) were designed and synthesized from various diols, 1,7-diprotected cyclen and epichlorohydrin. The molecular weights of the title polymers were measured by GPC with good polydispersity. Agarose gel retardation and fluorescent titration using ethidium bromide showed good DNA-binding ability of 5. They could retard plasmid DNA (pDNA) at an N/P ratio of 4-6 and form polyplexes with sizes around 100-250 nm from an N/P ratio of 10 to 60 and relatively low zeta-potential values (5-22 mV). The cytotoxicity of 5 assayed by MTT is much lower than that of 20 kDa PEI. In vitro transfection against A549 and 293 cells showed that the transfection efficiency (TE) of 5c/DNA polyplexes is close to that of 20 kDa PEI at an N/P ratio of 5. Structure-activity relationship (SAR) of 5 was discussed in their DNA-binding, cytotoxicity, and transfection studies. The TE of 5c/DNA polyplexes could be improved by the introduction of 50 μM of chloroquine, the endosomolytic agents, to pretreated cells. These studies may extend the application areas of macrocyclic polyamines, especially for cyclen.

Biotinylated Cyclen-Contained Cationic Lipids as Non-Viral Gene Delivery Vectors

A series of 1, 4, 7, 10‐tetraazacyclododecane (cyclen)‐based cationic lipids, namely 5a–c bearing a biotin moiety and a variety of end groups (cholesterol, diosgenin, and α‐tocopherol) via biodegradable carbamate bond linkage were prepared and applied as non‐viral gene delivery vectors. The liposomes formed from 5 and dioleoylphosphatidylethanolamine could bind and condense plasmid DNA into nanoparticles with appropriate size and zeta potentials. All biotinylated cyclen cationic lipids showed higher cell viability than commercially available lipofectamine 2000 even at high N/P ratios, while their transfection efficiency was relatively lower. Further, results indicate that among the three lipids, α‐tocopherol‐containing compound 5c has higher DNA‐binding ability, lower cytotoxicity, and higher transfection efficiency. Transfection in two different cell lines revealed that these lipoplexes have higher gene delivery efficiency toward tumor cells.

Small CyclenImidazolium‐Containing Molecules and Their Interactions with DNA

Three small organic molecules containing different numbers of cyclen and imidazolium units were synthesized. Their interactions with plasmid DNA and their potential for gene delivery vectors were investigated. Agarose gel retardation and ethidium bromide exclusion assays revealed that these molecules can effectively condense DNA, and compounds with higher molecular weights are needed to lower w/w ratio for full condensation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated that these compounds may form nanosized spherical particles with DNA. Furthermore, the complex formed from 10, i.e., 10/DNA, can partially release DNA from compact state at a relatively higher concentration of NaCl (200 mM). In the presence of the lipid 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine (DOPE), 10 could transfer plasmid DNA into BEL‐7402 cells. In addition, these compounds exhibited much lower cytotoxicity than PEI 25 kDa.