Gene transfection efficacies of novel cationic gemini lipids possessing aromatic backbone and oxyethylene spacers

Six novel gemini cationic lipids based on aromatic backbone, bearing n-C14H 29 or n-C16H33 hydrocarbon chains, differing in the length of oxyethylene type spacers -CH2-(CH2-O-CH2)m-CH2- between each ammonium headgroups have been synthesized, where m varies from 1 to 3. Each of these lipids formed stable suspensions in aqueous media. Cationic liposomes were prepared from each of these lipids individually and as mixtures of each cationic lipid and DOPE. These were used as nonviral gene delivery agents. Transfection studies showed that among lipids bearing n-C14H29 chains, the transfection efficacies decreased with the increase in the length of the spacer, whereas in case of lipids bearing n-C 16H33 chains, the transfection efficacies increased with the increase in the length of the spacer. Lipid bearing n-C16H33 hydrocarbon chains with a [-(CH2-CH2-O-CH2-CH2-O-CH2-CH2-O-CH2-CH2)-] spacer was found to be a potent gene transfer agent and its transfection was highly serum compatible even in the presence of 50% serum conditions.     

Association of albumin or protamine to lipoplexes: enhancement of transfection and resistance to serum

BACKGROUND: The successful application of gene therapy depends on the availability of carriers to efficiently deliver genetic material into target cells. Such efficacy is strongly related to key parameters including serum resistance and protection of DNA. METHODS: The complexes were tested in terms of their biological activity, in the absence or presence of serum, by following transfection activity. Interaction with plasma proteins was evaluated by immunoblotting, while cytotoxicity was assessed by the Alamar Blue assay. Extent of DNA protection was determined both by using ethidium bromide intercalation and DNase I digestion assays. RESULTS: Our results show that, depending on the charge ratio and on the lipid composition, albumin and protamine can be used (either individually or co-associated) to generate cationic liposome/DNA complexes fulfilling in vivo requirements, while exhibiting high levels of transfection activity. In the present work a novel cationic lipid was tested. It was demonstrated that 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (EPOPC):cholesterol (Chol) liposomes constitute a very promising carrier for gene delivery as illustrated by their enhancing effect on transfection, as compared with DOTAP-containing liposomes. Moreover, the biological activity of EPOPC-containing complexes is significantly improved upon association of albumin, even in the presence of 60% serum (namely for the 4/1 lipid/DNA charge ratio). Nevertheless, our studies also show that transfection activity mediated by DOTAP-containing complexes can be significantly enhanced upon pre-condensation of DNA with protamine. CONCLUSIONS: Co-association of HSA and protamine to lipoplexes ensures a high degree of DNA protection and results in high levels of transfection activity even in the presence of serum.     

Pyridinium cationic lipids in gene delivery: an in vitro and in vivo comparison of transfection efficiency versus a tetraalkylammonium congener

Cationic lipids provide a promising alternative to the use of viruses for delivering genes therapeutically. Among the several classes of lipidic vectors, those bearing a heterocyclic cationic head have shown important advantages, such as low cytotoxicity and improved efficiency across different cell lines. We recently reported a simple and efficient strategy for obtaining pyridinium cationic lipids, starting from pyrylium salts and primary amines. The present study is aimed to compare the cellular toxicity and transfection efficiency generated by the pyridinium polar head versus the tetramethylammonium one on several tumor cell lines and also in experimental animals, delivered via intratumor injections. Thus, the lead compound 1-(2,3-dioleoyloxypropyl)-2,4,6-trimethylpyridinium lipid (2Oc), coformulated with different helper lipids in various molar ratios, was tested against its ammonium congener DOTAP-a standard transfection reagent. The results revealed that when formulated with cholesterol at 1:1 molar ratio, the pyridinium lipid 2Oc was able to transfect several cancer cell lines with similar or better efficiency than its tetraalkylammonium congener DOTAP, while producing lower cytotoxicity. The NCI-H23 lung cancer cell line was found to be the most susceptible to be transfected. Therefore, we designed an in vivo assay based on this type of carcinoma in nude mice, which were injected intratumoral with 2Oc- and DOTAP-based lipoplexes. The red fluorescent protein reporter revealed that the pyridinium cationic lipid was superior to its tetraalkylammonium congener, transfecting the tissue on a higher area and with higher efficiency. These encouraging findings, together with the simple and efficient synthetic strategy, lay the foundation for further development of pyridinium lipids for gene therapy with improved transfection efficiency in vivo and even further reduced cytotoxicity.     

In Vivo Gene Transfer to the Mouse Nasal Cavity Mucosa Using a Stable Cationic Lipid Emulsion

We evaluate a new cationic emulsion as a mucosal gene carrier and elucidate the relationship between the transfection efficiency and the stability of the carrier/DNA complex. A cationic lipid emulsion was formulated with soybean oil and 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP) as major components and was used to transfer genes to the epithelial cells of the mouse nasal cavity via intranasal instillation. Correlation between the transfection efficiency and the stability of the carrier/DNA complex was investigated by measuring the carrier size changes and by observing the degree of DNA protection against DNase I digestion in the presence of heparin. The cationic emulsion showed at least 3 times better transfection activity than the liposomal carriers in nasal mucosae. The cationic emulsion was stable in the presence of heparin whereas the liposomal carriers became very unstable. Unlike DNA in liposome/DNA complexes, DNA in the emulsion/DNA complex was resistant to heparin exchange and DNase I digestion. The cationic emulsion was more effective in delivering DNA to nasal mucosae than commercially available liposomal carriers. The transfection activities of the lipid carriers in nasal cavity mucosae are in agreement with the stability of the lipid carriers and their complexes with DNA.     

Successful transfection of hepatoma cells after encapsulation of plasmid DNA into negatively charged liposomes

The application of conventional cationic liposomes/DNA complexes in gene transfer was hampered due to their large size, instability, and limited transfection site in vivo. In this report, we described a dialysis-based method and produced small, stable, and negatively charged DNA-containing liposomes composed of low content of cationic lipid and high content of fusogenic lipid. The liposomes were relatively spherical with a condensed core inside, and exhibited small size with narrow particle size distribution. The encapsulation efficiency of the liposomes was 42.53 +/- 2.29%. They were stable and showed enough protective ability to plasmid DNA from degradation after incubation with different amounts of DNase. Twenty-fold higher transfection efficiency for the liposomes was achieved when compared with that of naked plasmid DNA and no toxicities to hepatocellular carcinoma cells were observed. Our results indicate that the negatively charged DNA-containing liposomes can facilitate gene transfer in cultured cells, and may alleviate the drawbacks of the conventional cationic liposomes/DNA complexes for gene delivery in vivo.     

Biosurfactants of MEL-A increase gene transfection mediated by cationic liposomes.

Many microorganisms growing on water-insoluble substrates have been known to produce surface-active compounds called biosurfactants. Although biosurfactants have received increasing attention due to their special properties, there has been no information available until now of a role for them with regard to gene transfection. Thus, we studied here the effects of biosurfactants on gene transfection by cationic liposomes with a cationic cholesterol derivative. Our results showed clearly that a biosurfactant of mannosylerythritol lipid A (MEL-A) increased dramatically the efficiency of gene transfection mediated by cationic liposomes with a cationic cholesterol derivative. Among them, the liposomes with a cationic cholesterol derivative, cholesteryl-3 beta-carboxyamindoethylene-N-hydroxyethylamine (I), were much more effective for gene transfection than the liposomes with DC-Chol (cholesteryl-3 beta-oxycarboxyamidoethylenedimethylamine) or liposomes without MEL-A in various cultured cells. This demonstrates that this new finding has great potential in the experiment of gene transfection and gene therapy mediated by nonviral vectors such as cationic liposomes.     

Example of fatty acid-loaded lipoplex in enhancing in vitro gene transfer efficacies of cationic amphiphile

Herein, we report on the design and synthesis of a novel nontoxic cationic amphiphile N,N-di-n-tetradecyl-N-[2-[N',N'-bis(2-hydroxyethyl)amino]ethyl]-N-(2-hydroxyethyl)ammonium chloride (lipid 1) whose in vitro gene transfer efficacies in CHO, COS-1, MCF-7, and HepG2 cells are remarkably enhanced when used in combination with 30 mole percent added myristic acid. Reporter gene expression assay using p-CMV-SPORT-beta-gal reporter gene revealed poor gene transfer properties of the cationic liposomes of lipid 1 and cholesterol (colipid). However, the in vitro gene delivery efficacies of lipid 1 were found to be remarkably enhanced when the cationic liposomes of lipid 1 and cholesterol were prepared in the presence of 30 mole percent added myristic acid (with respect to lipid 1) as the third liposomal ingredient. The whole cell histochemical X-gal staining of representative CHO cells further confirmed the significantly enhanced gene transfer properties of the fatty acid-loaded cationic liposomes of lipid 1 and cholesterol. Electrophoretic gel patterns in the gel mobility shift assay supports the notion that better DNA release from fatty acid lipoplexes might play a role in their enhanced gene transfer properties. In addition, such myristic acid-loaded lipoplexes of lipid 1 were also found to be serum-compatible up to 30% added serum. Taken together, our present findings demonstrate that the transfection efficacies of fatty acid-loaded lipoplexes are worth evaluating particularly when traditional cationic liposomes prepared with either cholesterol or DOPE colipids fail to transfect cultured cells.     

Cationic Liposomes Containing Disulfide Bonds in Delivery of Plasmid DNA

Abstract

Cationic liposomes are non-viral gene transfer vectors for in vitro and in vivo experiments. In the present studies, we investigated whether a disulfide linkage in a cationic lipid was reducible by cell lysate resulting in the release of plasmid DNA and enhanced gene transfection. We also investigated if the differences in transgene production were from differences in total amount of cellular associated plasmid DNA. We systematically compared the gene transfection of disulfide bond containing-cationic lipid, 1', 2'-dioleoyl-sn-glycero-3'-succinyl-2-hydroxyethyl disulfide ornithine conjugate (DOGSDSO), its non-disulfide-containing analog, 1', 2'-dioleyl-sn-glycero-3'-succinyl-1, 6-hexanediol ornithine conjugate (DOGSHDO), 1, 2-dioleoyl-3-trimethylammonium-propane (DOTAP). Two transgene reporter systems (i.e., luciferase and green fluorescent protein (GFP)) were used to address transgene transgene expression and transgene efficiency. Experiments with the luciferase expression plasmid resulted in transgene activity up to 11 times greater transgene production for the disulfide containing lipid in at least two different cell lines, COS 1 and CHO cells. When transgene expression was determined by GFP activity, DOGSDSO liposomes were four times greater than the non-disulfide lipid or positive control (DOTAP) liposomes. By quantifying nucleic acid uptake by flow cytometry it was also demonstrated that increase expression was not solely from an increase in cellular plasmid DNA accumulation. These results demonstrate that cationic lipids containing a disulfide linkage are a promising method for gene transfer.     

Effect of the hydrocarbon chain and polymethylene spacer lengths on gene transfection efficacies of gemini lipids based on aromatic backbone

Design, syntheses, and gene delivery efficacies of fifteen novel gemini (dimeric) and three monomeric cationic lipids anchored on an aromatic backbone have been described. Each new lipid has been used for liposome formation, and optimal formulations were used to determine the structure-activity correlation of the gene transfection efficacies of these lipids in HeLa and HT1080 cells. The results of the present investigation bring out the effect of hydrocarbon chain lengths and the length of the spacer between the headgroups on gene transfection efficiencies of the cationic gemini lipids based on aromatic backbone. The lipids bearing n-C 14H 29 hydrocarbon chain lengths have been found to be the best transfecting agents compared to their counterparts with n-C 16H 33 and n-C 12H 25 chains in HeLa cells. On the other hand, in HT1080 cells, the lipids based on n-C 12H 25 and n-C 14H 29 chains were found to be more potent transfecting agents than lipids possessing n-C 16H 33 chains. Transmission electron microscopy examination revealed the existence of spherical lipid-DNA complexes.     

Influence of minor backbone structural variations in modulating the in vitro gene transfer efficacies of α-tocopherol based cationic transfection lipids

Toward probing the influence of backbone structural variation in cationic lipid mediated gene delivery of α-tocopherol based lipids, two novel α-tocopherol based lipids 1 and 2 have been designed and synthesized. The only structural difference between the cationic amphiphiles 1 and 2 is the backbone structure, where lipid 1 has a non-glycerol backbone and lipid 2 has a glycerol backbone. The lipids 1 and 2 showed contrasting transfection efficiencies: lipid 1 showed high gene transfer efficacy in multiple cultured animals cell lines, whereas lipid 2 is transfection incompetent. In summary, the present findings demonstrate that in the case of α-tocopherol based lipids even minor structural variations like backbone can profoundly influence size, DNA binding characteristics, cellular uptake, and consequently gene delivery efficacies.     

Incorporation of oxyethylene units between hydrocarbon chain and pseudoglyceryl backbone in cationic lipid potentiates gene transfection efficiency in the presence of serum.

Four novel cationic lipids with different numbers of oxyethylene units at the linkage region between the pseudoglyceryl backbone and the hydrocarbon chains have been synthesized and used as mixtures with 1,2-dioleoyl-L-alpha-glycero-3-phosphatidyl ethanolamine (DOPE) for liposome-mediated gene transfection. Incorporation of different numbers of oxyethylene (-CH(2)CH(2)O-) units between long hydrocarbon chain at the C-1 and C-2 positions of the pseudoglyceryl skeleton improved the transfection efficiency considerably compared to the one in which the chains were connected via simple ether links. A pronounced improvement in the gene transfer efficiency was observed with the unsymmetrical cationic lipid 3 in which the long hydrocarbon at the C-1 position of the pseudoglyceryl segment is connected via two (-CH(2)CH(2)O-) units. Notably, the transfection ability of lipid 3 with DOPE in the presence of serum was significantly greater than LIPOFECTAMINE. This suggests that introduction of oxyethylene units between long hydrocarbon chains at the C-1 and C-2 positions of the pseudoglyceryl skeleton provides a novel strategy to achieve efficient gene transfer, especially in conditions where the presence of serum is critical.     

Novel macrocyclic and acyclic cationic lipids for gene transfer: synthesis and in vitro evaluation

The synthesis and in vitro evaluation of four cationic lipid gene delivery vectors, characterized by acyclic or macrocyclic, and saturated or unsaturated hydrophobic regions, is described. The synthesis employed standard protocols, including ring-closing metathesis for macrocyclic lipid construction. All lipoplexes studied, formulated from plasmid DNA and a liposome composed of a synthesized lipid, 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine (EPC), and either 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) or cholesterol as co-lipid, exhibited plasmid DNA binding and protection from DNase I degradation, and concentration dependent cytotoxicity using Chinese hamster ovary-K1 cells. The transfection efficiency of formulations with cholesterol outperformed those with DOPE, and in many cases the EPC/cholesterol control, and formulations with a macrocyclic lipid (+/- 10:1) outperformed their acyclic counterparts (+/- 3:1).     

Aminoglycoside-derived cationic lipids as efficient vectors for gene transfection in vitro and in vivo

Background

Cationic lipids are at present very actively investigated for gene transfer studies and gene therapy applications. Basically, they rely on the formation of DNA/lipid aggregates via electrostatic interactions between their cationic headgroup and the negatively charged DNA. Although their structure/activity relationships are not well understood, it is generally agreed that the nature of the positive headgroup impacts on their transfection activity. Thus, we have directed our efforts toward the development of cationic lipids with novel cationic moieties. In the present work, we have explored the transfection potential of the lipophilic derivatives of the aminoglycoside kanamycin A. Indeed, aminoglycosides, which are natural polyamines known to bind to nucleic acids, provide a favorable scaffold for the synthesis of a variety of cationic lipids because of their structural features and multifunctional nature.

Methods and results

We report here the synthesis of a cationic cholesterol derivative characterized by a kanamycin A headgroup and of its polyguanidinylated derivative. The amino‐sugar‐based cationic lipid is highly efficient for gene transfection into a variety of mammalian cell lines when used either alone or as a liposomal formulation with the neutral phospholipid dioleoylphosphatidylethanolamine (DOPE). Its polyguanidinylated derivative was also found to mediate in vitro gene transfection. In addition, colloidally stable kanamycin‐cholesterol/DOPE lipoplexes were found to be efficient for gene transfection into the mouse airways in vivo.

Conclusions

These results reveal the usefulness of cationic lipids characterized by headgroups composed of an aminoglycoside or its guanidinylated derivative for gene transfection in vitro and in vivo. Copyright © 2002 John Wiley & Sons, Ltd.

     

Cerasome as an infusible and cell-friendly gene carrier: synthesis of cerasome-forming lipids and transfection using cerasome

Sonication of a pre-agitated aqueous solution of cationic lipid having a (EtO)3SiCH2CH2CH2 group on the quarternized ammonium nitrogen results in partially silica- or ceramic-coated liposome (cerasome), which can be used as an excellent transfection agent. Non-silylated reference lipid, which may represent cationic lipids that are used in conventional lipofection experiments, form a compact liposome, which undergoes DNA-induced fusion to provide transfection-irrelevant and larger (100-300 nm), more toxic particles. The surface-rigidified cerasome is infusible and the monomeric cerasome complex of DNA is of viral size (approximately 70 nm) and exhibits a remarkable transfection performance with a 10(2)-10(3)-fold higher efficiency (relative to the non-silylated reference lipid), minimized cytotoxicity and serum compatibility. The cerasome lipid is obtained by the reaction of 3-bromopropyltriethoxysilane with a tertiary amine derivative of the lipid. Preparation of an aqueous cerasome solution takes 1-2 h. The cerasome-DNA complex and the transfection takes about 3 d to complete.     

Stabilized plasmid-lipid particles: factors influencing plasmid entrapment and transfection properties.

Previous work has shown that plasmid DNA can be encapsulated in small 'stabilized plasmid-lipid particles' (SPLP) composed of 1, 2-dioleyl-3-phosphatidylethanolamine (DOPE), the cationic lipid N, N-dioleyl-N,N-dimethylammonium chloride (DODAC) and poly(ethylene glycol) (PEG) conjugated ceramides (PEG-Cer), employing a detergent dialysis procedure. These SPLP have potential as vectors for in vivo gene therapy. This study is aimed at characterizing the influence of the cationic lipid and PEG-Cer species on SPLP formation and in vitro transfection properties. It is shown that the transfection potency of SPLP is sensitive to the cationic lipid species employed, the size of the PEG polymer incorporated in the PEG-ceramide and the length of the acyl chain contained in the ceramide anchor. With regard to the influence of cationic lipid, the transfection levels achieved were highest for SPLP containing N-[2, 3-(dioleyloxy)propyl]-N,N-dimethyl-N-cyanomethylammonium chloride (DODMA-AN) and lowest for SPLP containing 3-beta-[N-(N', N'-dimethylaminoethyl)carbamoyl]-cholesterol (DC-CHOL), according to the series DODMA-AN>N-[2,3-(dioleyloxy)propyl]-N,N, N-trimethylammonium chloride (DOTMA)>DODAC>N,N-distearyl-N, N-dimethylammonium chloride (DSDAC)>DC-CHOL. Incorporation of short (PEG(750)) PEG polymers in the PEG-ceramide components resulted in modest improvements in transfection levels over PEG(2000) and PEG(5000) polymers, however variation of the length of the acyl chain contained in the hydrophobic ceramide anchor from octanoyl (PEG-CerC(8)) to myristoyl (PEG-CerC(14)) to arachidoyl (PEG-CerC(20)) had the most dramatic effects. Transfection levels achieved for SPLP containing PEG-CerC(8) were substantially larger than observed for SPLP containing PEG-CerC(14) or PEG-CerC(20), consistent with a requirement for the PEG-ceramide to dissociate from the SPLP surface for maximum transfection potency. It is also shown that the ability of SPLP to be accumulated into cells is a dominant factor influencing transfection potency, and that the transfection potency of SPLP that are accumulated is at least equivalent to that of cationic lipid-plasmid DNA complexes.     

Photoenhancement of transfection efficiency using novel cationic lipids having a photocleavable spacer

New cationic lipids having an o-nitrobenzyl moiety as a photocleavable spacer between its hydrophilic and hydrophobic region were synthesized. To improve the efficiency of transfection with lipoplexes, after transfecting the cationic lipid aggregate/DNA complex, photoirradiation was performed. Photochemical decomposition of lipids would not only make the vector's membrane unstable to facilitate the fusion with endocytic vesicles, but also promote dissociation of cationic lipid-DNA complex, thus aiding the escape of DNA from the endocytic vesicles. Using a luciferase gene as a model, we show that UV irradiation of photoresponsive lipoplex-treated COS-1 cells induces a substantial increase in the efficiency of transfection. Herein, we show a novel photoresponsive gene delivery system.     

Efficient gene transfection by bisguanylated diacetylene lipid formulations

We have previously shown that cationic cholesterol derivatives bearing guanidinium groups were efficient vectors for gene transfer. To further evaluate the potentiality of this novel class of cationic lipids, we undertook to study the transfection efficiency of guanidinium-based lipids with other hydrophobic moieties. Specifically, we synthesized a reagent where two guanidinium groups are linked to a diacetylene lipid which may provide the lipoplexes with favorable structural features. We report here that the cationic lipid bisguanidinium-diacetylene (BGDA) is highly efficient for in vitro gene transfection when formulated with dioleoylphosphatidyl ethanolamine (DOPE). We also show that liposomes composed of BGDA, DOPE, and a neutral diacetylene colipid, hydroxyethylenediacetylene (HEDA), are efficient for transfection. Thus, diacetylene-based lipids provide a novel scaffold for gene transfection and will be particularly useful for gaining new insights into the structure-activity relationships of the lipid/DNA complexes as they offer a means to study the effects of polymerizable domains.     

A transfection compound series based on a versatile Tris linkage

The family of cationic lipid transfection reagents described here demonstrates a modular design that offers potential for the ready synthesis of a wide variety of molecular variants. The key feature of these new molecules is the use of Tris as a linker for joining the hydrophobic domain to a cationic head group. The molecular design offers the opportunity to conveniently synthesise compounds differing in charge, the number and nature of hydrophobic groups in the hydrophobic domain and the characteristics of the spacer between the cationic and hydrophobic moieties. We show that prototype reagents of this design can deliver reporter genes into cultured cells with efficiencies rivaling those of established cationic lipid transfection reagents. A feature of these reagents is that they are not dependent on formulation with a neutral lipid for activity.     

Calcium enhances the transfection potency of plasmid DNA-cationic liposome complexes

It is shown that calcium increases the in vitro transfection potency of plasmid DNA-cationic liposome complexes from 3- to 20-fold. The effect is Ca(2+) specific as other cations, such as Mg(2+) and Na(+), do not give rise to enhanced transfection and the effect can be inhibited by the presence of EGTA. It is shown that Ca(2+) increases cellular uptake of the DNA-lipid complexes, indicating that increased transfection potency arises from increased intracellular delivery of both cationic lipid and plasmid DNA in the presence of Ca(2+). In particular, it is shown that the levels of intact intracellular plasmid DNA are significantly enhanced when Ca(2+) is present. The generality of the Ca(2+) effect for enhancing complex-mediated transfection is demonstrated for a number of different cell lines and different cationic lipid formulations. It is concluded that addition of Ca(2+) represents a simple and useful protocol for enhancing in vitro transfection properties of plasmid DNA-cationic lipid complexes.     

In vitro gene transfer efficacies and serum compatibility profiles of novel mono-, di-, and tri-histidinylated cationic transfection lipids: a structure-activity investigation

Recently, we demonstrated that covalent grafting of an endosome-disrupting single histidine functionality in the headgroup region imparts high gene transfer properties to cationic amphiphiles (Kumar, V. V., et al. Gene Ther. 2003, 10, 1206-1215). However, whether covalent attachment of multiple histidine functionalities in the headgroup region are capable of further enhancing the gene transfer efficacies of cationic amphiphiles remains to be explored. To this end, herein, we report on the design, syntheses, physicochemical characterizations, in vitro gene transfer properties, and serum compatibilities of three novel nontoxic cationic transfection amphiphiles containing mono-, di-, and tri-histidine functionalities in their headgroup regions (lipids 1-3) in multiple cultured cells. Significantly, findings in both the reporter gene expression assay and the whole cell histochemical X-gal staining assay support the notion that there is no linear correlation between the in vitro transfection efficacies and the number of histidine functionalities in the polar headgroup regions for histidinylated cationic amphiphiles. The relative gene transfer efficiencies, as well as the serum compatibilities, of the present histidinylated cationic amphiphiles were found to be strikingly dependent on the medium of lipoplex formation. Most importantly, high serum compatibilities (up to 50% added serum) of the lipoplexes of lipids 1 and 3 make them promising nonviral transfection vectors for future systemic applications.