Enhancement of liposome mediated gene transfer by adding cholesterol and cholesterol modulating drugs.

Cholesterol is an important cell membrane component and has been used as co-lipid for cationic liposome to enhance gene delivery. However, the role of cholesterol in transfection efficiency has not been fully understood. In this study, transfection efficiency of liposome was measured after cholesterol was added to the cell culture medium. As a result, addition of cholesterol increased transfection efficiency of several liposomes consisting of different lipid components in various cells (AGS, CHO, COS7 and, MCF7). Furthermore, treatment of cells with cholesterol modulating drugs, imipramine and U18666A, also increased transfection efficiency of liposomes. To elucidate the role of added cholesterol in gene transfer, endocytotic mechanism was studied and also revealed that adding cholesterol in culture media induced participation of caveolae-mediated endocytosis and micropinocytosis in CHO cell. Therefore, the results of this work suggest that modulation of intracellular cholesterol can be an important method to enhance gene delivery.

Synthesis of cholesteryl doxorubicin and its anti-cancer activity.

Doxorubicin (dox) has been used as anti-cancer agent, but there are disadvantages such as rapid excretion, short retention time and cardiotoxicity. For giving lipophilic properties to dox, it was modified with cholesterol derivatives that were validated as a component of liposomal gene delivery. This article describes the synthesis of dox derivatives (lipo-dox A-D), their cytotoxicity and cellular uptake. In A549, HeLa, MCF7 and MDA MB 231 cell lines, lipo-dox A and lipo-dox B substituted at alcohol group showed similar anti-cancer effect as dox, but lipo-dox C and lipo-dox D substituted at amino group did not. As a result, the amino group of dox seems an important site for its cancer cell inhibition. Lipophilic property of lipo-dox A and lipo-dox B induced more accumulation in cells compared to parent drug. Therefore, the newly synthesized lipo-dox A and lipo-dox B would be a good candidate for anti-cancer agent.

DOTAP/DOPE ratio and cell type determine transfection efficiency with DOTAP-liposomes.

The effects of lipid compositions on their physicochemical properties and transfection efficiencies were investigated. Four liposome formulations with different 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) to dioleoylphosphatidylethanolamine (DOPE) weight ratios were investigated, that is, weight ratios 1:0 (T1P0), 3:1 (T3P1), 1:1 (T1P1), and 1:3 (T1P3). Mean sizes of liposomes were influenced by their lipid composition and the preparation concentration at the time of sonication. Zeta potentials of liposomes were inversely correlated with their liposome sizes. However, neither liposome sizes nor zeta potentials were correlated with transfection efficiency. The optimum composition of liposomes was cell-line dependent (T1P0 and T3P1 for Huh7 and AGS, T3P1 and T1P1 for COS7, and T1P1 and T1P3 for A549). The shape of lipoplexes was changed from lamellar to inverted hexagonal structure according to the increased ratio of DOPE, but there was no definite advantage of specific structure in transfection efficiency throughout all used cell lines. However, cellular internalization was consistently faster in T1P0, T3P1, T1P1 compared to T1P3 in all cell lines, suggesting the importance of endosomal escape. Our findings show that the transfection efficiency of DOTAP liposomes is mainly influenced by lipid composition and cell type, and not by size or zeta potential.

Synthesis and validation of novel cholesterol-based fluorescent lipids designed to observe the cellular trafficking of cationic liposomes.

Cholesterol-based fluorescent lipids with ether linker were synthesized using NBD (Chol-E-NBD) or Rhodamine B (Chol-E-Rh), and the usefulnesses as fluorescent probes for tracing cholesterol-based liposomes were validated. The fluorescent intensities of liposomes containing these modified lipids were measured and observed under a microscope. Neither compound interfered with the expression of GFP plasmid, and live cell images were obtained without interferences. Changes in the fluorescent intensity of liposomes containing Chol-E-NBD were followed by flow cytometry for up to 24h. These fluorescent lipids could be useful probes for trafficking of cationic liposome-mediated gene delivery.

Efficient delivery of plasmid DNA using cholesterol-based cationic lipids containing polyamines and ether linkages.

Cationic liposomes are broadly used as non-viral vectors to deliver genetic materials that can be used to treat various diseases including cancer. To circumvent problems associated with cationic liposome-mediated delivery systems such as low transfection efficiency and serum-induced inhibition, cholesterol-based cationic lipids have been synthesized that resist the effects of serum. The introduction of an ether-type linkage and extension of the aminopropyl head group on the cholesterol backbone increased the transfection efficiency and DNA binding affinity compared to a carbamoyl-type linkage and a mono aminopropyl head group, respectively. Under optimal conditions, each liposome formulation showed higher transfection efficiency in AGS and Huh-7 cells than commercially available cationic liposomes, particularly in the presence of serum. The following molecular structures were found to have a positive effect on transfection properties: (i) extended aminopropyl head groups for a strong binding affinity to plasmid DNA; (ii) an ether linkage that favors electrostatic binding to plasmid DNA; and (iii) a cholesterol backbone for serum resistance.

Endocytic pathway and resistance to cholesterol depletion of cholesterol derived cationic lipids for gene delivery.

Cholesterol-based cationic lipids have been widely used because of biocompatibility and serum resistance. However, the reason for the effectiveness of cholesterol-based cationic lipids remains unclear. We compared the transfection route of CHOL-E, a cholesterol-based cationic lipid having an amine head and an ether linker, with that of DOTAP. The luciferase assay with chemical inhibitors and microscopic observation of pathway markers revealed that clathrin mediated endocytosis is the main pathway for CHOL-E and DOTAP. However, CHOL-E showed resistance to cholesterol depletion by methyl-ß-cyclodextrin. Furthermore, CHOL-E recovered the transfection efficiency of DOTAP from cholesterol depletion. These results suggested that superior transfection of CHOL-E might be partly derived from effects on the cell membrane.

Homodimeric SV40 NLS peptide formed by disulfide bond as enhancer for gene delivery.

Recently, cysteine residue incorporation increased liposome-mediated transfection compared to unmodified peptide. Therefore, we designed novel modified SV40 NLS peptides, homodimeric (NLS-CTHD, NLS-NTHD) and closed structure (cyclic NLS), simply using disulfide bond between cysteines to develop more efficient and safe non-viral gene delivery system. The simple mix of NLS-CTHD among these novel transfection enhancing peptides with DNA increased the gene transfer potency of cationic liposomes more efficiently with no additional cytotoxicity.

The synthesis of cholesterol-based cationic lipids with trimethylamine head and the effect of spacer structures on transfection efficiency.

Five cholesterol-based cationic lipids were newly synthesized based on cholest-5-en-3ß-oxyethane-N,N,N-trimethylammonium bromide (Chol-ETA) structure where the cholesterol backbone is linked to cationic head via various lengths of ether-linked carbon spacer. The transfection efficiency of these compounds was increased in order of three (Chol-PRO)

Synthesis of novel cholesterol-based cationic lipids for gene delivery.

The new cholesterol-based cationic lipids B, C, and D with an ether linked spacer were synthesized by using aminopropyl chain extension with acrylonitrile. The cholesterol-based cationic lipid A with carbamoyl linkage were also synthesized in order to compare the difference in transfection efficiency of the two linkage types. To this end, GFP expression of these cationic lipids was confirmed respectively.

In-vitro and in-vivo difference in gene delivery by lithocholic acid-polyethyleneimine conjugate.

Polyethyleneimine (PEI) is widely used for the delivery of nucleic acids, but its clinical application is limited due to high cytotoxicity and instability in biological fluids. To overcome these challenges, linear PEI (2.5 kDa) was modified with lithocholic acid (LCA) to produce a LCA-PEI conjugate (lp), and its complex with plasmid DNA (pDNA) was covered with hyaluronic acid (HA). Ternary complexes of pDNA, lp, and HA ("DlpH") were prepared in different ratios and tested in cells and tumor-bearing mice for gene transfection efficiency. DlpH with a relatively high lp/pDNA ratio (Hi-DlpH) was more resistant to DNase and heparin treatment and showed more efficient gene transfection than DlpH with a lower lp/pDNA ratio (Lo-DlpH) in vitro. In contrast, Hi- and Lo-DlpH showed distinct transfection efficiency in vivo in a tumor-size dependent manner, where Hi-DlpH showed relatively high gene transfection in tumors of <300 mm3 but performed poorly in tumors of >500 mm3 and Lo-DlpH did the opposite. Tumor-associated macrophages, which increase with tumor growth and preferentially intercept Hi-DlpH, may account for the poor performance of Hi-DlpH in relatively large tumors. Accordingly, suggestions are made for future in vitro screening of new gene formulations to better predict their in vivo performances.

Intraportally delivered stem cell spheroids localize in the liver and protect hepatocytes against GalN/LPS-induced fulminant hepatic toxicity.

BACKGROUND: Systemic inflammatory response syndrome (SIRS) is common in severe fulminant hepatic failure (FHF) and has a high mortality rate (20-50%) due to irreversible cerebral edema or sepsis. Stem cell-based treatment has emerged as a promising alternative therapeutic strategy to prolong the survival of patients suffering from FHF via the inhibition of SIRS due to their immunomodulatory effects. METHODS: 3D spheroids of adipose-derived mesenchymal stem cells (3D-ADSC) were prepared by the hanging drop method. The efficacy of the 3D-ADSC to rescue FHF was evaluated in a D-galactosamine/lipopolysaccharide (GalN/LPS)-induced mouse model of FHF via intraportal transplantation of the spheroids. RESULTS: Intraportally delivered 3D-ADSC better engrafted and localized into the damaged livers compared to 2D-cultured adipose-derived mesenchymal stem cells (2D-ADSC). Transplantation of 3D-ADSC rescued 50% of mice from FHF-induced lethality, whereas only 20% of mice survived when 2D-ADSC were transplanted. The improved transplantation outcomes correlated with the enhanced immunomodulatory effect of 3D-ADSC in the liver microenvironment. CONCLUSION: The study shows that the transplantation of optimized 3D-ADSC can efficiently ameliorate GalN/LPS-induced FHF due to improved viability, resistance to exogenous ROS, and enhanced immunomodulatory effects of 3D-ADSC.

Radiation-enhanced delivery of plasmid DNA to tumors utilizing a novel PEI polyplex.

The excitement surrounding the potential of gene therapy has been tempered due to the challenges that have thus far limited its successful implementation in the clinic such as issues regarding stability, transfection efficiency, and toxicity. In this study, low molecular weight linear polyethyleneimine (2.5 kDa) was modified by conjugation to a lipid, lithocholic acid, and complexed with a natural polysaccharide, dermatan sulfate (DS), to mask extra cationic charges of the modified polymer. In vitro examination revealed that these modifications improved complex stability with plasmid DNA (pDNA) and transfection efficiency. This novel ternary polyplex (pDNA/3E/DS) was used to investigate if tumor-targeted radiotherapy led to enhanced accumulation and retention of gene therapy vectors in vivo in tumor-bearing mice. Imaging of biodistribution revealed that tumor irradiation led to increased accumulation and retention as well as decreased off-target tissue buildup of pDNA in not only pDNA/3E/DS, but also in associated PEI-based polyplexes and commercial DNA delivery vehicles. The DS-containing complexes developed in this study displayed the greatest increase in tumor-specific pDNA delivery. These findings demonstrate a step forward in nucleic acid vehicle design as well as a promising approach to overall cancer gene therapy through utilization of radiotherapy as a tool for enhanced delivery.

Polyethylenimine-dermatan sulfate complex, a bioactive biomaterial with unique toxicity to CD146-positive cancer cells.

We report unique bioactivity of a polycation-polyanion complex with potential utility for cancer therapy. A complex of disulfide-crosslinked polyethyleneimine (CLPEI), a polycation used for gene complexation, and dermatan sulfate (DS), an anionic polysaccharide to shield excessive cationic charge of the former, has toxicity to a specific group of cancer cell lines, including B16-F10 murine melanoma, A375SM human melanoma, and PC-3 human prostate cancer cells. These CLPEI-DS-sensitive cells express CD146, which binds to the complex via interaction with DS. There is a positive correlation between toxicity and intracellular level of CLPEI, indicating that the CLPEI-DS-sensitivity is attributable to the increased cellular uptake of CLPEI mediated by the DS-CD146 interactions. In vitro studies show that CLPEI-DS complex causes G0/G1 phase arrest and apoptotic cell death. In syngeneic and allograft models of B16-F10 melanoma, CLPEI-DS complex administered with a sub-toxic level of doxorubicin potentiates the chemotherapeutic effect of the drug by loosening tumor tissues. Given the unique toxicity, CLPEI-DS complex may be a useful carrier of gene or chemotherapeutics for the therapy of CD146-positive cancers.

Tannic acid-mediated surface functionalization of polymeric nanoparticles.

Polymeric nanoparticles (NPs) are decorated with various types of molecules to control their functions and interactions with specific cells. We previously used polydopamine (pD) to prime-coat poly(lactic-co-glycolic acid) (PLGA) NPs and conjugated functional ligands onto the NPs via the pD coating. In this study, we report tannic acid (TA) as an alternative prime coating that is functionally comparable to pD but does not have drawbacks of pD such as optical properties and interference of ligand characterization. TA forms a stable and optically inert coating on PLGA NPs, which can accommodate albumin, chitosan, and folate-terminated polyethylene glycol to control the cell-NP interactions. Moreover, TA coating allows for surface loading of polycyclic planar aromatic compounds. TA is a promising reactive intermediate for surface functionalization of polymeric NPs.

Drug Carriers: Not an Innocent Delivery Man.

Biomaterials used as drug carriers are often considered inactive and assumed to have no other roles than modifying pharmacokinetics and biodistribution of a drug. On the other hand, there are several examples in which the carrier materials show bioactivities in the body, which may have been underestimated or inadvertently ignored. This review highlights several examples where biomaterials used as drug carriers bring biological effects, known or newly discovered, and discusses their implications in development of new drug delivery systems.

Synthesis of NBD-labeled DOTAP analog to track intracellular delivery of liposome.

A DOTAP analog labeled by NBD on the head group (DTNBD) was designed and synthesized to label DOTAP liposome. The structure was confirmed by (1)H NMR and FAB-MS, and the fluorescence of the newly synthesized DT-NBD was observed by fluorescent microscopy. The transfection efficiency of DOTAP liposome containing DT-NBD was comparable to commonly used NBD PE in COS7 and MCF7 cells. Furthermore, the level of cellular uptake and fluorescent intensity of fluorescent liposome containing DT-NBD was higher than NBD PE. Therefore, the novel NBD-labeled DOTAP analog seems to be effectively used for investigation of the cellular interaction and transfection mechanism of DOTAP liposome.

Transfection property of a new cholesterol-based cationic lipid containing tri-2-hydroxyethylamine as gene delivery vehicle.

A novel cholesterol-based cationic lipid containing a tri-2- hydroxyethylamine head group and ether linker (Chol- THEA) was synthesized and examined as a potent gene delivery vehicle. In the preparation of cationic liposome, the addition of DOPE as helper lipid significantly increased the transfection efficiency. To find the optimum transfection efficiency, we screened various weight ratios of DOPE and liposome/DNA (N/P). The best transfection efficiency was found at the Chol-THEA:DOPE weight ratio of 1:1 and N/P weight ratio of 10~15. Most of the plasmid DNA was retarded by this liposome at the optimum N/P weight ratio of 10. The transfection efficiency of Chol-THEA liposome was compared with DOTAP, Lipofectamine, and DMRIE-C using the luciferase assay and GFP expression. Chol-THEA liposome with low toxicity had better or similar potency of gene delivery compared with commercial liposomes in COS-7, Huh-7, and MCF-7 cells. Therefore, Chol-THEA could be a useful non-viral vector for gene delivery.

Synthesis and optimization of cholesterol-based diquaternary ammonium Gemini Surfactant (Chol-GS) as a new gene delivery vector.

Amongst a number of potential nonviral vectors, cationic liposomes have been actively researched, with both gemini surfactants and bola amphiphiles reported as being in possession of good structures in terms of cell viability and in vitro transfection. In this study, a cholesterol-based diquaternary ammonium gemini surfactant (Chol-GS) was synthesized and assessed as a novel nonviral gene vector. Chol-GS was synthesized from cholesterol by way of four reaction steps. The optimal efficiency was found to be at a weight ratio of 1:4 of lipid:DOPE (1,2-dioleoyl-L-alpha- glycero-3-phosphatidylethanolamine), and at a ratio of between 10:1~15:1 of liposome:DNA. The transfection efficiency was compared with commercial liposomes and with Lipofectamine, 1,2-dimyristyloxypropyl-3-dimethylhydroxyethylammonium bromide (DMRIE-C), and N-[1-(2,3-dioleoyloxy)propyl]- N,N,N-trimethylammonium chloride (DOTAP). The results indicate that the efficiency of Chol-GS is greater than that of all the tested commercial liposomes in COS7 and Huh7 cells, and higher than DOTAP and Lipofectamine in A549 cells. Confirmation of these findings was observed through the use of green fluorescent protein expression. Chol-GS exhibited a moderate level of cytotoxicity, at optimum concentrations for efficient transfection, indicating cell viability. Hence, the newly synthesized Chol-GS liposome has the potential of being an excellent nonviral vector for gene delivery.