Membrane fusion plays an important role in gene transfection mediated by cationic liposomes

Versatility of Liposomes for Antisense Oligonucleotide Delivery: A Special Focus on Various Therapeutic Areas

Nucleic acid therapeutics, specifically antisense oligonucleotides (ASOs), can effectively modulate gene expression and protein function, leading to long-lasting curative effects. The hydrophilic nature and large size of oligonucleotides present translational challenges, which have led to the exploration of various chemical modifications and delivery systems. The present review provides insights into the potential role of liposomes as a drug delivery system for ASOs. The potential benefits of liposomes as an ASO carrier, along with their method of preparation, characterization, routes of administration, and stability aspects, have been thoroughly discussed. A novel perspective in terms of therapeutic applications of liposomal ASO delivery in several diseases such as cancer, respiratory disease, ophthalmic delivery, infectious diseases, gastrointestinal disease, neuronal disorders, hematological malignancies, myotonic dystrophy, and neuronal disorders remains the major highlights of this review.

CRISPR/Cas9-loaded stealth liposomes effectively cleared established HPV16-driven tumours in syngeneic mice

Gene-editing has raised the possibility of being able to treat or cure cancers, but key challenges remain, including efficient delivery, in vivo efficacy, and its safety profile. Ideal targets for cancer therapy are oncogenes, that when edited, cause cell death. Here, we show, using the human papillomavirus (HPV) type 16 cancer cell line TC1, that CRISPR/Cas9 targeting the E7 oncogene and packaged in PEGylated liposomes cleared established tumours in immunocompetent mice. Treatment caused no significant toxicity in the spleen or liver. An ideal therapeutic outcome would be the induction of an immunogenic cell death (ICD), such that recurrent tumours would be eliminated by the host immune system. We show here for the first time that CRISPR/Cas9-mediated cell death via targeting E7 did not result in ICD. Overall, our data show that in vivo CRISPR/Cas targeting of oncogenes is an effective treatment approach for cancer.

Deciphering the response of asymmetry in the hydrophobic chains of novel cationic lipids towards biological function

Cationic liposomes, a type of non-viral vectors, often play the important biological function of delivering nucleic acids during cell transfection. Variations in the molecular architecture of di-alkyl dihydroxy ethyl ammonium chloride-based cationic lipids involving hydrophobic tails have been found to influence their biological function in terms of cell transfection efficiency. For example, liposomes based on a cationic lipid (Lip1814) with asymmetry in the hydrophobic chains were found to display higher transfection efficacy in cultured mammalian cell lines than those comprising of symmetric Lip1818 or asymmetric Lip1810. The effect of variations in the molecular architecture of the cationic lipids on the biological activity of liposomes has been explored here via the photophysical studies of 8-anilino-1-naphthalenesulphonate (ANS) and Nile Red (NR) in three cationic liposomes, namely Lip1810, Lip1814 and Lip1818. Time-resolved fluorescence of ANS revealed reduced hydration at the lipid-water interface and enhanced relaxation dynamics of surface water (lipid headgroup bound water molecules) in Lip1810- and Lip1814-based liposomes in the presence of cholesterol. As the probe ANS failed to be incorporated into the lipid-water interface of Lip1818 due to the significantly high rigidity of these liposomes, no information concerning the extent of hydration of the lipid-water interface or the interfacial water dynamics could be obtained. Time-resolved polarization-gated anisotropy measurements of NR in the presence of cholesterol revealed the rigidity of the cationic liposomes to be increasing in the order of Lip1810 < Lip1814 < Lip1818. In the presence of cholesterol, moderately higher rigidity, reduced membrane hydration and enhanced relaxation dynamics of the interfacial water molecules gave rise to the superior cell transfection efficacy of Lip1814-based cationic liposomes than those of the highly flexible Lip1810 or the highly rigid Lip1818.

Exploring membrane permeability of Tomatidine to enhance lipid mediated nucleic acid transfections

Intracellular delivery of nucleic acids is one of the critical steps in the transfections. Prior findings demonstrated various strategies including membrane fusion, endosomal escape for the efficient cytoplasmic delivery. In our continuing efforts to improve the nucleic acids transfections, we harnessed cell permeable properties of Tomatidine (T), a steroidal alkaloid abundantly found in green tomatoes for maximizing intracellular delivery of lipoplexes. We doped Tomatidine into liposomes of cationic lipid with amide linker (A) from our lipid library. Six liposomal formulations (AT) of Lipid A (1 mM) with varying concentrations of Tomatidine (0-1 mM) were prepared and evaluated for their transfection efficacies. Owing to its signature characteristic of cell membrane permeability, Tomatidine modulated endocytosis process, enhanced the intracellular delivery of the lipoplexes, and in turn increased the transfection efficacy of cationic liposomes. Our findings provide 'proof of concept' for enhancing transfections in gene delivery applications with Tomatidine in cationic liposomal formulations. These findings can be further applied in lipid mediated gene therapy and drug delivery applications.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

Amphiphilic polyethylenimine (PEI) as highly efficient non-viral gene carrier

Efficient and safe gene vectors are important for gene therapy. Here, a novel family of amphiphilic polyethylenimine (PEI) LD1-PEI bearing a polar group of branched PEI 25K and four dodecyl chains was developed. Agarose gel electrophoresis was used to confirm the formation of complexes. The transfection activity of the amphiphilic carrier was evaluated in different cell lines. The in vitro study showed that LD1-PEI showed a higher transfection efficiency with improved biocompatibility than PEI 25K. Serum showed almost no or only a slight effect on LD1-PEI/DNA transfection efficiency. In summary, LD1-PEI is a promising nonviral gene carrier.

Studies on intracellular delivery of carboxyl-coated CdTe quantum dots mediated by fusogenic liposomes

The use of Quantum Dots (QDs) as fluorescent probes for understanding biological functions has emerged as an advantageous alternative over application of conventional fluorescent dyes. Intracellular delivery of QDs is currently a specific field of research. When QDs are tracking a specific target in live cells, they are mostly applied for extracellular membrane labeling. In order to study intracellular molecules and structures it is necessary to deliver free QDs into the cell cytosol. In this work, we adapted the freeze and thaw method to encapsulate water dispersed carboxyl-coated CdTe QDs into liposomes of different compositions, including cationic liposomes with fusogenic properties. We showed that labeled liposomes were able to fuse with live human stem cells and red blood cells in an endocytic-independent way. We followed the interactions of liposomes containing QDs with the cells. The results were minutely discussed and showed that QDs were delivered, but they were not freely diffused in the cytosol of those cells. We believe that this approach has the potential to be applied as a general route for encapsulation and delivery of any membrane-impermeant material into living cells.

Cellular uptake mechanisms of novel anionic siRNA lipoplexes

PURPOSE

To investigate cellular uptake pathways of novel anionic siRNA-lipoplexes as a function of formulation composition.

METHODS

Anionic formulations with anionic lipid/Ca(2+)/siRNA ratio of 1.3/2.5/1 (AF1) and 1.3/0.3/1 (AF2) were utilized. Uptake mechanisms were investigated using uptake inhibition and co-localization approaches in breast cancer cells. Actin-mediated uptake was investigated using actin polymerization and rearrangement assays. Silencing efficiency and endosomal escaping capability of lipoplexes were evaluated. The cationic formulation Lipofectamine-2000 was used as a control.

RESULTS

Anionic lipoplexes entered the breast cancer cells via endocytosis specifically via macropinocytosis or via both macropinocytosis and HSPG (heparin sulfate proteoglycans) pathways, depending on the Ca(2+)/siRNA ratio. Additionally, uptake of these lipoplexes was both microtubule and actin dependent. The control cationic lipid-siRNA complexes (Lipofectamine-2000) were internalized via both endocytic (phagocytosis, HSPG) and non-endocytic (membrane fusion) pathways. Their uptake was microtubule independent but actin dependent. Silencing efficiency of the AF2 formulation was negligible mainly due to poor endosomal release (rate-limiting step).

CONCLUSIONS

Formulation composition significantly influences the internalization mechanism of anionic lipoplexes. Uptake mechanism together with formulation bioactivity helped in identification of the rate-limiting steps to efficient siRNA delivery. Such studies are extremely useful for formulation optimization to achieve enhanced intracellular delivery of nucleic acids.

Structure relationship of cationic lipids on gene transfection mediated by cationic liposomes

The aim of this study was to investigate the transfection efficiency of cationic liposomes formulated with phosphatidylcholine (PC) and novel synthesized diethanolamine-based cationic lipids at a molar ratio of 5:1 in comparison with Lipofectamine™ 2000. Factors affecting transfection efficiency and cell viability, including the chemical structure of the cationic lipids, such as different amine head group (diamine and polyamine; and non-spermine and spermine) and acyl chain lengths (C14, C16, and C18) and the weight ratio of liposomes to DNA were evaluated on a human cervical carcinoma cell line (HeLa cells) using the pDNA encoding green fluorescent protein (pEGFP-C2). Characterizations of these lipoplexes in terms of size and charge measurement and agarose gel electrophoresis were performed. The results from this study revealed that almost no transfection was observed in the liposome formulations composed of cationic lipids with a non-spermine head group. In addition, the transfection efficiency of these cationic liposomes was in the following order: spermine-C14 > spermine-C16 > spermine-C18. The highest transfection efficiency was observed in the formulation of spermine-C14 liposomes at a weight ratio of 25; furthermore, this formulation was safe for use in vitro. In conclusion, cationic liposomes containing spermine head groups demonstrated promising potential as gene carriers.

Effect of unsaturated alkyl chains on transfection activity of poly(amidoamine) dendron-bearing lipids

In an earlier study, we developed a new type of gene vector using poly(amidoamine) (PAMAM) dendron-bearing lipids and reported that their transfection activity was affected by their structures, such as dendron generation and alkyl chain length. In this study, for improvement of their performance as gene vectors, we examined the effect of unsaturated chains of the dendron-bearing lipids using DL-G1-2C(18), which consists of PAMAM G1 dendron moiety and two octadecyl chains, and achieved the most efficient transfection activity among the dendron-bearing lipids having saturated alkyl chains, and DL-G1-2C(18)-U2, which consists of the same dendron-moiety and two octadecenyl chains. DL-G1-2C(18)-U2 showed a higher ability to form lipoplexes with plasmid DNA than DL-G1-2C(18). The DL-G1-2C(18)-U2 lipoplexes exhibited much smaller particle sizes than the DL-G1-2C(18). In addition, the DL-G1-2C(18)-U2 lipoplexes exhibited more efficient transfection of HeLa cells than DL-G1-2C(18) did. Results demonstrate the importance of unsaturated chains for the production of the dendron-bearing lipids having excellent gene transfection performance. Without the help of additional fusogenic lipids such as dioleoylphosphatidylethanolamine, DL-G1-2C(18)-U2 lipoplexes achieved the highly efficient transfection of the cells without marked cellular toxicity, in the presence of serum. Therefore, DL-G1-2C(18)-U2 might be promising as a potent gene vector.

Assessment of new biocompatible poly(N-(morpholino)ethyl methacrylate)-based copolymers by transfection of immortalized keratinocytes

Skin carcinomas are among the most commonly diagnosed tumors in the world. In this study, we investigated the transfection of immortalized keratinocytes, used as an in vitro model for skin carcinoma, using the antisense technology and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-based copolymers. In order to improve the transfection efficiency of the classic PDMAEMA polymers, copolymers were synthesized including a poly(N-morpholino)ethylmethacrylate) (PMEMA) moiety for an improved proton-sponge effect, intended to favour the release of the oligonucleotide from the acidic endosome. These copolymers were synthesized either statistically (with alternating PDMAEMA and PMEMA fragments) or in blocks (one PDMAEMA block followed by one PMEMA block). MTT assays were performed using the PDMAEMA-PMEMA copolymers and revealed no significant cytotoxicity of these polymers at an N/P ratio of 7.3. Using fluorescent oligonucleotides and analyzing transfection efficiency by flow cytometry, we noticed no significant differences between the two kinds of copolymers. However copolymers with a higher DMAEMA content and a higher Mn were also those displaying the highest vectorization efficiency. Confocal microscopy showed that these copolymers induced a fine granular distribution of the transfected antisense oligonucleotides inside the cells. We also assessed the functionality of the transfected antisense oligonucleotide by transfecting immortalized GFP expressing keratinocytes with a GFP antisense oligonucleotide using these copolymers. A significant silencing was achieved with a PDMAEMA-PMEMA in block copolymer (Mn=41,000, 89 % PDMAEMA). Together, these results suggest that PDMAEMA-PMEMA copolymers combining low toxicity, vectorization and proton sponge properties, can be efficiently used to transfect immortalized keratinocytes and so open new perspectives in the therapy of skin carcinomas as well as of other skin diseases of genetic or immunological origin.

Comparative study of the in vitro and in vivo characteristics of cationic and neutral liposomes

Neutral liposomes (NLP) exhibit preferential localization in solid tumors based on the enhanced permeation and retention (EPR) effect. Cationic liposomes (CLP) have a propensity for localizing in newly formed tumor vessels and they have a potentially enhanced antitumor effect. However, an increased amount of cationic lipids in liposomes also induces aggregation through electrostatic interactions between the liposomes and the anionic species in the circulation, which results in a reduced EPR effect. Consequently, it is important to investigate the characteristics of liposomes with different surface potentials in vitro to achieve an optimal intratumoral distribution and antitumor effect in vivo. In this study, the authors evaluated the characteristics of doxorubicin (DOX)-loaded NLPs, CLPs, polyethylene glycol (PEG)-modified NLPs (NLP-PEG), and PEGylated CLPs (CLP-PEG) (ie, encapsulation efficacy, zeta potential, size, membrane fluidity, aggregation in serum, and uptake of liposomes into rat aortic endothelial cells (RAECs)) to further understand their influences on the pharmacokinetics, biodistribution, and antitumor therapy in vivo. The results showed that increased amounts of cationic lipids resulted in severe liposome aggregation in the presence of serum, yet it did not alter the membrane fluidity to a large extent. The uptake of liposomes into RAECs, visualized by confocal fluorescence microscopy, confirmed the rapid uptake of CLP by the endothelial cells compared with NLP. However, the pharmacokinetics, biodistribution and anticancer efficacies of these liposomes in vivo revealed that the CLP with highly positive surface potentials exhibited reduced circulation times and poor distribution in tumors. The NLP-PEG exhibited the highest anticancer efficacy; CLP-PEG, the second highest; and CLP with the most positive surface potential, the lowest. These phenomena were mostly due to the rapid aggregation in serum and subsequent accumulation in the lungs upon the intravenous injection of the CLP. Caution should be exercised when chemotherapeutic drugs are loaded into CLP for tumor therapy.

Radiolabeled oligonucleotides for antisense imaging

Oligonucleotides radiolabeled with isotopes emitting γ-rays (for SPECT imaging) or positrons (for PET imaging) can be useful for targeting messenger RNA (mRNA) thereby serving as non-invasive imaging tools for detection of gene expression in vivo (antisense imaging). Radiolabeled oligonucleotides may also be used for monitoring their in vivo fate, thereby helping us better understand the barriers to its delivery for antisense targeting. These developments have led to a new area of molecular imaging and targeting, utilizing radiolabeled antisense oligonucleotides. However, the success of antisense imaging relies heavily on overcoming the barriers for its targeted delivery in vivo. Furthermore, the low ability of the radiolabeled antisense oligonucleotide to subsequently internalize into the cell and hybridize with its target mRNA poses additional challenges in realizing its potentials. This review covers the advances in the antisense imaging probe development for PET and SPECT, with an emphasis on radiolabeling strategies, stability, delivery and in vivo targeting.

Pre-clinical evaluation of liposomal gene transfer to improve dermal and epidermal regeneration

Liposomal gene transfer effectively enhances dermal and epidermal regeneration in burned rodents. To advance this treatment to clinical studies, we investigated the efficacy of liposomal gene transfer in a clinically relevant porcine wound model. Mimicking the clinical scenario, six female Yorkshire pigs (40-50 kg) received up to 12 burns of 50 cm(2) area that were fully excised and covered with skin autograft meshed at 4:1 ratio 24 h post-burn. Animals received control injections (empty liposomes), liposomes (DMRIE-C) containing 1 mg LacZ-cDNA, or liposomes (DMRIE-C) with 1 mg of platelet-derived growth factor (PDGF)-cDNA, or the naked PDGF gene. Serial biopsies were taken from different wound sites at multiple time points up to 12 days post-wounding. Transfection efficacy and transfection rate of LacZ and localization of beta-gal were determined by immunohistochemical and immunofluorescent techniques. RT-PCR and multiplex protein analysis (ELISA) were used to measure levels of growth factor mRNA transcribed and growth factor protein translated. Wound re-epithelialization and graft adhesion was evaluated using planimetric analysis and clinical scores. We found that peak transfection of liposomal beta-galactosidase occurred on day 2, with a fluorescence increase of 154% to baseline (P<0.001). Transfection intensity dropped to 115% above baseline on day 4 (P<0.001) and 109% on day 7. Immunohistochemistry showed a maximum transfection rate of 34% of cells in wound tissue. Gene transfer of liposomal PDGF-cDNA resulted in increased PDGF-mRNA and protein expression on days 2 and 4, and accelerated wound re-epithlialization as well as graft adhesion on day 9 (P<0.05). In this study, we showed that liposomal cDNA gene transfer is possible in a porcine wound model, and by using PDGF-cDNA we further showed that dermal and epidermal regeneration can be improved. These data indicate that liposomal gene transfer can be a new therapeutic approach to improve wound healing in humans.

The biological routes of gene delivery mediated by lipid-based non-viral vectors

Cationic lipid/DNA complexes (lipoplexes) represent an attractive alternative to viral vectors for cell transfection in vitro and in vivo but still suffer from relatively low efficiency. Comprehension of the interactions between vectors and DNA as well as cellular pathways and mechanisms in DNA entry into cells and ultimately nuclei will lead to the design of better adapted non-viral vectors for gene therapy applications. Here, some recent developments in the field on the pathways and mechanisms involved in lipoplex-mediated transfection are discussed. The techniques that are widely used to study the mechanism of gene delivery are also discussed.

The effect of nocodazole on the transfection efficiency of lipid-bilayer coated gold nanoparticles

Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement. Therefore, NCZ can be used as a transfection enhancer in DODAB-AuNPs mediated transfection system. This work also gave an insight to improving the efficiency of lipid-mediated transfection: modifying lipid on gold nanoparticles and pre-treating cells by NCZ before the transfection.

Biophysical properties of CDAN/DOPE-analogue lipoplexes account for enhanced gene delivery

Typically, cationic liposomes are formulated from the combination of a synthetic cationic lipid (cytofectin) and a neutral, biologically available co-lipid. However, the use of cationic liposome formulations to mediate gene delivery to cells is hampered by a paradox. Cationic lipids, such as N(1)-cholesteryloxycarbonyl-3-7-diazanonane-1,9-diamine (CDAN), are needed to ensure the formation of cationic liposome-DNA (lipoplex, LD) particles by plasmid DNA (pDNA) condensation, as well as for efficient cell binding of LD particles and intracellular trafficking of pDNA post-intracellular delivery by endocytosis. However, the same cationic lipids can exhibit toxicity, and also promote LD particle colloidal instability, leading to aggregation. This results from electrostatic interactions with anionic agents in biological fluids, particularly in vivo. One of the most commonly used neutral, bioavailable co-lipids, dioleoyl L-alpha-phosphatidylethanolamine (DOPE), has been incorporated into many cationic liposome formulations owing to its fusogenic characteristics that are associated with a preference for the inverted hexagonal (H(II)) phase-a phase typical of membrane-membrane fusion events. However, these same fusogenic characteristics also destabilize LD particles substantially with respect to aggregation, in vitro and especially in vivo. Therefore, there is a real need to engineer more stable cationic liposome systems with lower cellular toxicity. We hypothesize that one way to achieve this goal should be to find the means to reduce the mol fraction of cationic lipid in cationic liposomes without impairing the overall transfection efficiency, by replacing DOPE with an alternative co-lipid with fusogenic properties "tuned" with a greater preference for the more stable lamellar phases than DOPE is able to achieve. Herein, we document the syntheses of triple bond variants of DOPE, and their formulation into a range of low charge, low cationic lipid containing LD systems. The first indications are that our hypothesis is correct in vitro.

Generation of highly potent nonviral gene vectors by complexation of lipoplexes and transferrin-bearing fusogenic polymer-modified liposomes in aqueous glucose solution

We reported previously that complexation of lipoplexes containing 3,5-dipentadecyloxybenzamidine (TRX-20) and transferrin-bearing succinylated poly(glycidol) (SucPG)-modified liposome, which becomes fusogenic under weakly acidic conditions, might produce gene carriers with high transfection activity. For the present study, we prepared the lipoplex-SucPG-modified liposome complexes by mixing them either in phosphate-buffered saline or in an aqueous 5% glucose solution. The complexes prepared in phosphate-buffered saline have large particles of more than 800 nm, whereas the complexes prepared in the glucose solution were remarkably small: 200-300 nm. The small complexes were taken up more effectively by HeLa cells, and their transfection was induced more efficiently than the large complexes'. In addition, the small complexes achieved cellular transfection more efficiently in the presence of serum than in the absence of serum, without marked cytotoxicity. Considering that their affinity to the cell is based on ligand-receptor interaction, the small complexes are highly promising as a safe vector with high transfection activity and high target cell specificity.

Efficient preparation of liposomes encapsulating food materials using lecithins by a mechanochemical method

In order to evaluate to the feasibility of using lecithins for nanocapsules including functional food materials, liposomes were prepared from different commercially available lecithins (SLP-WHITE, SLP-PC70 and PL30S) by the Bangham method, and their physicochemical properties were examined by using a confocal laser scanning microscopy (CLSM) and the measurements of trapping efficiency. There was little difference in the trapping efficiency among the three types of liposomes. In all cases, the trapping efficiency clearly increased with an increase of the lecithin concentration up to 10 wt % , and the maximum efficiency reached at approximately 15%. CLSM observation showed the particle size of liposomes prepared from SLP-WHITE is significantly smaller than that prepared from other lecithins. In addition, liposomal solution prepared from SLP-WHITE remained well dispersed for at least 30 days, while two other liposomal solutions showed a phase separation due to aggregation and/or fusion of liposomes. These results indicated that SLP-WHITE is the most appropriate for the preparation of stable liposomes with well dispersed among the lecithins tested. SLP-WHITE liposomes were then prepared by the mechanochemical method using a homogenizer and microfluidizer, aiming at improving the preparation efficiency and liposome stability. The particle size of the prepared SLP-WHITE liposomes decreased with increasing inlet pressure and the number of processed cycles, and reached between 73 and 123 nm based on the measurement using dynamic light scattering. Moreover, freeze-fracture transmission electron microscopy revealed that the prepared liposomes are small unilamellar vesicles (SUV) with a diameter of approximately 100 nm. The extract of Curcuma longa Linn. (Ukon), which contains curcumins as a functional food material, was then subjected to the mechanochemical method with SLP-WHITE to give liposomes including the functional materials. Interestingly, the trapping efficiency of the liposomes for curcumins was found to reach over 85%. From these results, the present mechanochemical method is very likely to allow us to efficiently prepare stable and functional liposomes from the low-cost lecithin. The method may thus have a potential for manufacturing practical nanocapsules, which serves as a novel carrier of functional food materials.

NBD-conjugated biosurfactant (MEL-A) shows a new pathway for transfection

Gene transfection is a fundamental technology for molecular and cell biology, and also clinical gene therapy. A variety of non-viral vectors have been investigated for gene transfection, but their gene delivery had remained an inefficient process. Recently, we found that a biosurfactant, mannosylerythritol lipid (MEL)-A, dramatically increased the efficiency in transfection of plasmid DNA mediated by cationic liposomes. However, its mechanism has not been understood yet. Here we examined the mechanism of the transfection mediated by cationic liposomes with NBD-conjugated MEL-A. We found that MEL-A first gradually distributed on the intracellular membranes through the plasma membranes of target cells, while the cationic liposomes with MEL-A fused to the plasma membranes in 20-35 min. Thereafter, the oligonucleotide released from the vesicles was immediately transferred to the nucleus. The present results showed a new role of non-viral vectors in transfection.

Synergy in lipofection by cationic lipid mixtures: superior activity at the gel-liquid crystalline phase transition

Some mixtures of two cationic lipids including phospholipid compounds (O-ethylphosphatidylcholines) as well as common, commercially available cationic lipids, such as dimethylammonium bromides and trimethylammonium propanes, deliver therapeutic DNA considerably more efficiently than do the separate molecules. In an effort to rationalize this widespread "mixture synergism", we examined the phase behavior of the cationic lipid mixtures and constructed their binary phase diagrams. Among a group of more than 50 formulations, the compositions with maximum delivery activity resided unambiguously in the solid-liquid crystalline two-phase region at physiological temperature. Thus, the transfection efficacy of formulations exhibiting solid-liquid crystalline phase coexistence is more than 5 times higher than that of formulations in the gel (solid) phase and over twice that of liquid crystalline formulations; phase coexistence occurring at physiological temperature thus appears to contribute significantly to mixture synergism. This relationship between delivery activity and physical property can be rationalized on the basis of the known consequences of lipid-phase transitions, namely, the accumulation of defects and increased disorder at solid-liquid crystalline phase boundaries. Packing defects at the borders of coexisting solid and liquid crystalline domains, as well as large local density fluctuations, could be responsible for the enhanced fusogenicity of mixtures. This study leads to the important conclusion that manipulating the composition of the lipid carriers so that their phase transition takes place at physiological temperature can enhance their delivery efficacy.

MR contrast probes that trace gene transcripts for cerebral ischemia in live animals

The aim of this research was to validate transcription magnetic resonance (MR) imaging (MRI) for gene transcript targeting in acute neurological disorders in live subjects. We delivered three MR probe variants with superparamagnetic iron oxide nanoparticles (SPION, a T2 susceptibility agent) linked to a phosphorothioate-modified oligodeoxynucleotide (sODN) complementary to c-fos mRNA (SPION-cfos) or beta-actin mRNA (SPION-beta-actin) and to sODN with random sequence (SPION-Ran). Each probe (1 microg Fe in 2 microl) was delivered via intracerebroventricular infusion to the left cerebral ventricle of male C57Black6 mice. We demonstrated SPION retention, measured as decreased T2* signal or increased R2* value (R2* = 1/T2*). Animals that received the SPION-beta-actin probe exhibited the highest R2* values, followed (in descending order) by SPION-cfos and SPION-Ran. SPION-cfos retention was localized in brain regions where SPION-cfos was present and where hybrids of SPION-cfos and its target c-fos mRNA were detected by in situ reverse transcription PCR. In animals that experienced cerebral ischemia, SPION-cfos retention was significantly increased in locations where c-fos mRNA increased in response to the ischemic insult; these elevations were not observed for SPION-beta-actin and SPION-Ran. This study should enable MR detection of mRNA alteration in disease models of the central nervous system.

Anchoring Cationic Amphiphiles for Nucleotide Delivery Significance of DNA Release from Cationic Liposomes for Transfection

We have designed and synthesized lithocholic acid-based cationic amphiphile molecules as components of cationic liposomes for gene transfection (lipofection). To study the relationship between the molecular structures of those amphiphilic molecules, particularly the extended hydrophobic appendant (anchor) at the 3-hydroxyl group, and transfection efficiency, we synthesized several lithocholic and isolithocholic acid derivatives, and examined their transfection efficiency. We also compared the physico-chemical properties of cationic liposomes prepared from these derivatives. We found that isolithocholic acid derivatives exhibit higher transfection efficiency than the corresponding lithocholic acid derivatives. This result indicates that the orientation and extension of hydrophobic regions influence the gene transfection process. Isolithocholic acid derivatives showed a high ability to encapsulate DNA in a compact liposome-DNA complex and to protect it from enzymatic degradation. Isolithocholic acid derivatives also facilitated the release of DNA from the liposome-DNA complex, which is a crucial step for DNA entry into the nucleus. Our results show that the transfection efficiency is directly influenced by the ability of the liposome complex to release DNA, rather than by the DNA-encapsulating ability. Molecular modeling revealed that isolithocholic acid derivatives take relatively extended conformations, while the lithocholic acid derivatives take folded structures. Thus, the efficiency of release of DNA from cationic liposomes in the cytoplasm, which contributes to high transfection efficiency, appears to be dependent upon the molecular shape of the cationic amphiphiles.

Characterization of Biosurfactant-Containing Liposomes and Their Efficiency for Gene Transfection

Recently we showed significance of biosurfactants in the field of non-viral vectors for gene transfection. There, a biosurfactant, mannosylerythritol lipid A (MEL-A), especially increased the efficiency of gene transfection mediated with cationic liposomes. However, the molecular mechanism has not been well-understood yet. Here, through the examination of the ability of cationic liposomes containing an MEL (MEL-A, MEL-B or MEL-C) for important transfectional processes of the DNA capsulation and the membrane fusion with anionic liposomes, we found that MEL-A-containing liposomes increased both processes, but that MEL-B and MEL-C-containing liposomes just increased either of them. The results indicated that these kinds of the physicochemical properties in MEL-A-containing liposomes are able to increase the efficiency of liposome-mediated gene transfection.

Mechanisms of co-modified liver-targeting liposomes as gene delivery carriers based on cellular uptake and antigens inhibition effect

In order to deliver antisense oligonucleotides (asODN) into hepatocytes orientedly in the treatment of hepatitis B virus (HBV) infection, the liver-targeting cationic liposomes was developed as a gene carrier, which was co-modified with the ligand of the asialoglycoprotein receptor (ASGPR), beta-sitosterol-beta-d-glucoside (sito-G) and the nonionic surfactant, Brij 35. Flow cytometry (FCM) analysis and enzyme-linked immunosorbent assay (ELISA) showed that the asODN-encapsulating cationic liposomes exhibited high transfection efficiency and strong antigens inhibition effect in primary rat hepatocytes and HepG2.2.15 cells, respectively. With the help of several inhibitors acting on different steps during the targeting lipofection, the cellular uptake mechanisms of the co-modified liver-targeting cationic liposomes were investigated through antigens inhibition effect assay and confocal laser scanning microscopy (CLSM) analysis. The cellular uptake with high transfection efficiency seemed to involve both endocytosis and membrane fusion. The ligand sito-G was confirmed to be able to enhance ASGPR-mediated endocytosis, the nonionic surfactant Brij 35 seemed to be able to facilitate membrane fusion, and the co-modification resulted in the most efficient transfection but no enhanced cytotoxicity. These results suggested that the co-modified liver-targeting cationic liposomes would be a specific and effective carrier to transfer asODN into hepatocytes infected with HBV orientedly.

Higly fusogenic cationic liposomes transiently permeabilize the plasma membrane of HeLa cells

Cationic liposomes can efficiently carry nucleic acids into mammalian cells. This property is tightly connected with their ability to fuse with negatively charged natural membranes (i.e. the plasma membrane and endosomal membrane). We used FRET to monitor and compare the efficiency of lipid mixing of two liposomal preparations — one of short-chained diC14-amidine and one of long-chained unsaturated DOTAP — with the plasma membrane of HeLa cells. The diC14-amidine liposomes displayed a much higher susceptibility to lipid mixing with the target membranes. They disrupted the membrane integrity of the HeLa cells, as detected using the propidium iodide permeabilization test. Morphological changes were transient and essentially did not affect the viability of the HeLa cells. The diC14-amidine liposomes were much more effective at either inducing lipid mixing or facilitating transfection.

Lipoplex formulation of superior efficacy exhibits high surface activity and fusogenicity, and readily releases DNA

Lipoplexes containing a mixture of cationic phospholipids dioleoylethylphosphatidylcholine (EDOPC) and dilauroylethylphosphatidylcholine (EDLPC) are known to be far more efficient agents in transfection of cultured primary endothelial cells than are lipoplexes containing either lipid alone. The large magnitude of the synergy permits comparison of the physical and physico-chemical properties of lipoplexes that have very different transfection efficiencies, but minor chemical differences. Here we report that the superior transfection efficiency of the EDLPC/EDOPC lipoplexes correlates with higher surface activity, higher affinity to interact and mix with negatively charged membrane-mimicking liposomes, and with considerably more efficient DNA release relative to the EDOPC lipoplexes. Observations on cultured cells agree with the results obtained with model systems; confocal microscopy of transfected human umbilical artery endothelial cells (HUAEC) demonstrated more extensive DNA release into the cytoplasm and nucleoplasm for the EDLPC/EDOPC lipoplexes than for EDOPC lipoplexes; electron microscopy of cells fixed and embedded directly on the culture dish revealed contact of EDLPC/EDOPC lipoplexes with various cellular membranes, including those of the endoplasmic reticulum, mitochondria and nucleus. The sequence of events outlining efficient lipofection is discussed based on the presented data.

Gene therapy in wound healing: present status and future directions

Gene therapy was traditionally considered a treatment modality for patients with congenital defects of key metabolic functions or late-stage malignancies. The realization that gene therapy applications were much vaster has opened up endless opportunities for therapeutic genetic manipulations, especially in the skin and external wounds. Cutaneous wound healing is a complicated, multistep process with numerous mediators that act in a network of activation and inhibition processes. Gene delivery in this environment poses a particular challenge. Numerous models of gene delivery have been developed, including naked DNA application, viral transfection, high-pressure injection, liposomal delivery, and more. Of the various methods for gene transfer, cationic cholesterol-containing liposomal constructs are emerging as a method with great potential for non-viral gene transfer in the wound. This article aims to review the research on gene therapy in wound healing and possible future directions in this exciting field.

[Functional fluctuation]

The discovery of the double-helical structure of DNA, the elucidation of the genetic code, and the determination of the three-dimensional structure of several proteins are some of the outstanding achievements of biochemistry and life sciences in the latter half of the last century. Proteins play key roles in almost all the biological processes and the biological function of a protein depends on its conformation which is defined as the three-dimensional arrangement of the atoms of a molecule. The three-dimensional structure, however, is not rigid but fluctuated. Structural fluctuation plays an important role in bio-macromolecules. How about "functional fluctuation" in biological systems? The present review proposes that functional fluctuation is also very important for understanding the mechanism of supramolecules, biological processes in living cells, and the interaction between biological systems. This new theme is pretty well supported by our recent experiments for neuro-immune crosstalk, gene transfection with cationic liposomes, and cell signaling in embryonic stem cells.

Potential use of drug carried-liposomes for cancer therapy via direct intratumoral injection

Liposomes have recognized advantages as nano-particle drug carriers for tumor therapy. In this study, the pharmacokinetics and distribution of intratumorally administered liposomes were investigated as drug carriers for treating solid tumors via direct intratumoral administration. 99mTc-liposomes were administered intratumorally to nude rats bearing human head and neck squamous cell carcinoma xenografts. Planar gamma camera images were analyzed to evaluate the local retention of the intratumorally administered liposomes. Co-registered pinhole micro-single photon emission computed tomography (SPECT)/computed tomography (CT) images were acquired of the whole animal as well as the dissected tumors to determine intratumoral distribution of the 99mTc-liposomes. For 99mTc-liposomes, there was an initial retention of 47.4 +/- 11.0% (n = 4) in tumors and surrounding tissues. At 20 h, 39.2 +/- 10.6% (n = 4) of 99mTc-activity still remained in the tumor. In contrast, only 18.7 +/- 3.3% (n = 3) of the intratumoral 99mTc-activity remained for unencapsulated 99mTc-complex at 20 h. Pinhole micro-SPECT images demonstrated that 99mTc-liposomes also have a superior intratumoral 99mTc-activity diffusion compared with unencapsulated 99mTc-complex. Higher intratumoral retention of 99mTc-liposomes accompanied by an improved intratumoral diffusion suggests that intratumorally administered liposomal drugs are potentially promising agents for solid tumor local therapy.

Surface properties of dioleoyl-sn-glycerol-3-ethylphosphocholine, a cationic phosphatidylcholine transfection agent, alone and in combination with lipids or DNA

Long-chain cationic amphipaths are routinely used for transfecting DNA into cells, although the mechanism of DNA delivery by these agents is poorly understood. Since their interfacial properties are undoubtedly involved at some stage in the process, a comprehensive study of the surface behavior of at least one of these compounds is highly desirable. Hence, the behavior of the cationic transfection agent EDOPC (dioleoyl-sn-glycerol-3-ethylphosphocholine or O-ethyldioleoylphosphatidylcholine), has been characterized at the air-water interface, by itself and in mixtures with other phospholipids. Surface pressure-molecular area isotherms obtained at the argon-buffer interface revealed that EDOPC is considerably (5-10 A(2)) more expanded than the parent phosphatidylcholine (DOPC) and even more expanded than the corresponding phosphatidylglycerol (DOPG), which has a similar charge density (of opposite polarity) as EDOPC. A 1:1 mixture of EDOPC and DOPG is very slightly condensed relative to DOPG and considerably condensed relative to EDOPC. The surface/dipole potential of this mixture is the mean of those of EDOPC and DOPG and is almost the same as that of DOPC. When the composition of EDOPC mixtures was varied, several surface parameters, including surface dipole moment, collapse pressure, and compressibility, exhibited discontinuities at a 1:1 mole ratio. EDOPC is unusually surface-active; the equilibrium surface tension of its dispersion was lower and the rate of fall of the surface tension (dynamic surface activity) of a dispersion with an initially clean surface was more than an order of magnitude greater than that for dispersions of DOPG. A 1:1 mixture of the cationic lipoid and phosphatidylglycerol had lower surface activity than DOPC in water but similar surface activity in 0.1 NaCl. Analysis, in terms of surface concentration, of the formation of EDOPC monolayers at the air interface of vesicle dispersions revealed a simple exponential rise to a maximum, at least for higher concentrations. Addition of a small proportion of DNA to EDOPC increased its dynamic surface activity even though DNA alone has no detectable surface activity at the concentrations used. This enhancement by DNA is presumably due to the disruption of the continuity of the bilayer and creation of defects from which lipoid spreads readily. The surface properties of this cationic compound, both alone and in combination with anionic lipids, provide insight into the previously described nonbilayer phase preferences of cationic-anionic lipid mixtures. In addition, they provide critical data (area condensation of mixed cationic-anionic monolayers) supporting a previously proposed mechanism of fusion of cationic bilayers with anionic bilayers. Such a process, involving anionic cellular membranes, is believed to be required for release of DNA from lipoplexes and is therefore a key stage of transfection.

The effect of PS content on the ability of natural membranes to fuse with positively charged liposomes and lipoplexes

Supramolecular aggregates containing cationic lipids have been widely used as transfection mediators due to their ability to interact with negatively charged DNA molecules and biological membranes. First steps of the process leading to transfection are partly electrostatic, partly hydrophobic interactions of liposomes/lipoplexes with cell and/or endosomal membrane. Negatively charged compounds of biological membranes, namely glycolipids, glycoproteins and phosphatidylserine (PS), are responsible for such events as adsorption, hemifusion, fusion, poration and destabilization of natural membranes upon contact with cationic liposomes/lipoplexes. The present communication describes the dependence of interaction of cationic liposomes with natural and artificial membranes on the negative charge of the target membrane, charges which in most cases were generated by charging the PS content or its exposure. The model for the target membranes were liposomes of variable content of PS or PG (phosphatidylglycerol) and erythrocyte membranes in which the PS and other anionic compound content/exposure was modified in several ways. Membranes of increased anionic phospholipid content displayed increased fusion with DOTAP (1,2-dioleoyl-3-trimethylammoniumpropane) liposomes, while erythrocyte membranes partly depleted of glycocalix, its sialic acid, in particular, showed a decreased fusion ability. The role of the anionic component is also supported by the fact that erythrocyte membrane inside-out vesicles fused easily with cationic liposomes. The data obtained on erythrocyte ghosts of normal and disrupted asymmetry, in particular, those obtained in the presence of Ca(2+), indicate the role of lipid flip-flop movement catalyzed by scramblase. The ATP-depletion of erythrocytes also induced an increased sensitivity to hemoglobin leakage upon interactions with DOTAP liposomes. Calcein leakage from anionic liposomes incubated with DOTAP liposomes was also dependent on surface charge of the target membranes. In all experiments with the asymmetric membranes the fusion level markedly increased with an increase of temperature, which supports the role of membrane lipid mobility. The decrease in positive charge by binding of plasmid DNA and the increase in ionic strength decreased the ability of DOTAP liposomes/lipoplexes to fuse with erythrocyte ghosts. Lower pH promotes fusion between erythrocyte ghosts and DOTAP liposomes and lipoplexes. The obtained results indicate that electrostatic interactions together with increased mobility of membrane lipids and susceptibility to form structures of negative curvature play a major role in the fusion of DOTAP liposomes with natural and artificial membranes.

PS exposure increases the susceptibility of cells to fusion with DOTAP liposomes

Cationic liposomes are used as efficient carriers for gene delivery into mammalian cells due to their ability to bind nucleic acids, adsorb onto the cell surface and fuse with negatively charged membranes. This last property enables the release and escape of their cargo from endosomal compartments. The efficiency of this fusion mainly depends on the surface charge of the target membranes. Here, we report that cells of two different lines, epithelial adenocarcinoma HeLa and lymphocytic leukemia Jurkat T, which externalize PS, are more susceptible to fusion with DOTAP liposomes than control cells. We compared the ability to undergo fusion of untreated and apoptotic cells. Apoptosis was induced by various pro-apoptotic agents and treatments, namely: incubation in the presence of MnCl(2), cytostatic drugs fludarabine and mitoxantrone, staurosporine and serum depletion in the case of HeLa cells. Jurkat T cells were treated similarly except apoptosis was additionally induced by incubation in the presence of 4% EtOH. Epithelial cells fused with the highest efficiencies of lipid mixing, when pretreated with staurosporine. Jurkat T cells were less susceptible to fusion, but they also displayed an increase in fusion efficiency after the induction of apoptosis. Alternatively, we treated the cells with metabolic inhibitors causing ATP-depletion in order to inactivate aminophospholipid translocase. After ATP-depletion, HeLa and Jurkat T cells fused with DOTAP liposomes with higher efficiencies than control cells. Our conclusion is that the lipid asymmetry of natural membranes may limit fusion with cationic liposomes.

Liposome-mediated transient transfection reduces cholesterol-dependent coxsackievirus infectivity

Liposome-mediated gene delivery provides a powerful strategy for the study of gene function and for gene therapy. Coxsackievirus B3 is an important human pathogen associated with various diseases. Here we reported that liposome-mediated transient transfection of plasmid cDNA inhibited coxsackieviral replication at the levels of RNA, protein and viral progeny release. These inhibitory effects were observed in various cell types and by using different liposome reagents. We further showed that the inhibition was likely due to the lack of virus attachment. Moreover, we showed that addition of cholesterol restored, at least in part, the viral infectivity. Interestingly, we found that membrane cholesterol levels were unchanged during transfection, indicating that disruption rather than depletion of membrane cholesterol contributes to the inhibitory effects of transfection. Our data suggest that liposome-mediated cDNA transient transfection inhibits coxsackievirus infectivity via inhibition of viral attachment, which is likely occurring through the changes of membrane cholesterol integrity.