Cationic liposome/DNA complexes: from structure to interactions with cellular membranes

Molecular localization and exchange kinetics in pharmaceutical liposome and mRNA lipoplex nanoparticle products determined by small angle X-ray scattering and pulsed field gradient NMR diffusion measurements

We have used pulsed field gradient (PFG)-NMR diffusion experiments, also known as DOSY, in combination with small angle X-ray scattering measurements to investigate structure and molecular exchange dynamics between pharmaceutical lipid nanoparticles and the bulk phase. Using liposomes and lipoplexes formed after complexation of the liposomes with messenger mRNA as test systems, information on dynamics of encapsulated water molecules, lipids and excipients was obtained. The encapsulated fraction, having a diffusivity similar to that of the liposomes, could be clearly identified and quantified by the NMR diffusion measurements. The unilamellar liposome membranes allowed a fast exchange of water molecules, while sucrose, used as an osmolyte and model solute, showed very slow exchange. Upon interactions with mRNA a topological transition from a vesicular to a lamellar organization took place, where the mRNA was inserted in repeating lipid bilayer stacks. In the lipoplexes, a small fraction of tightly bound water molecules was present, with a diffusivity that was influenced by the additional presence of sucrose. This extended information on dynamic coherencies inside pharmaceutical nanoparticle products, provided by the combined application of SAXS and PFG-NMR diffusion measurements, can be valuable for evaluation of quality and comparability of nanoscaled pharmaceuticals.

Lipoplexes' Structure, Preparation, and Role in Managing Different Diseases

Lipid-based vectors are becoming promising alternatives to traditional therapies over the last 2 decades specially for managing life-threatening diseases like cancer. Cationic lipids are the most prevalent non-viral vectors utilized in gene delivery. The increasing number of clinical trials about lipoplex-based gene therapy demonstrates their potential as well-established technology that can provide robust gene transfection. In this regard, this review will summarize this important point. These vectors however have a modest transfection efficiency. This limitation can be partly addressed by using functional lipids that provide a plethora of options for investigating nucleic acid-lipid interactions as well as in vitro and in vivo nucleic acid delivery for biomedical applications. Despite their lower gene transfer efficiency, lipid-based vectors such as lipoplexes have several advantages over viral ones: they are less toxic and immunogenic, can be targeted, and are simple to produce on a large scale. Researchers are actively investigating the parameters that are essential for an effective lipoplex delivery method. These include factors that influence the structure, stability, internalization, and transfection of the lipoplex. Thorough understanding of the design principles will enable synthesis of customized lipoplex formulations for life-saving therapy.

Strategies for Improved pDNA Loading and Protection Using Cationic and Neutral LNPs with Industrial Scalability Potential Using Microfluidic Technology

Purpose

In recent years, microfluidic technologies have become mainstream in producing gene therapy nanomedicines (NMeds) following the Covid-19 vaccine; however, extensive optimizations are needed for each NMed type and genetic material. This article strives to improve LNPs for pDNA loading, protection, and delivery, while minimizing toxicity.

Methods

The microfluidic technique was optimized to form cationic or neutral LNPs to load pDNA. Classical "post-formulation" DNA addition vs "pre" addition in the aqueous phase were compared. All formulations were characterized (size, homogeneity, zeta potential, morphology, weight yield, and stability), then tested for loading efficiency, nuclease protection, toxicity, and cell uptake.

Results

Optimized LNPs formulated with DPPC: Chol:DOTAP 1:1:0.1 molar ratio and 10 µg of DOPE-Rhod, had a size of 160 nm and good homogeneity. The chemico-physical characteristics of cationic LNPs worsened when adding 15 µg/mL of pDNA with the "post" method, while maintaining their characteristics up to 100 µg/mL of pDNA with the "pre" addition remaining stable for 30 days. Interestingly, neutral LNPs formulated with the same method loaded up to 50% of the DNA. Both particles could protect the DNA from nucleases even after one month of storage, and low cell toxicity was found up to 40 µg/mL LNPs. Cell uptake occurred within 2 hours for both formulations with the DNA intact in the cytoplasm, outside of the lysosomes.

Conclusion

In this study, the upcoming microfluidic technique was applied to two strategies to generate pDNA-LNPs. Cationic LNPs could load 10x the amount of DNA as the classical approach, while neutral LNPs, which also loaded and protected DNA, showed lower toxicity and good DNA protection. This is a big step forward at minimizing doses and toxicity of LNP-based gene therapy.

Nanoparticles and siRNA: A new era in therapeutics?

Since its discovery in 1998, the use of small interfering RNA (siRNA) has been increasing in biomedical studies because of its ability to very selectively inhibit the expression of any target gene. Thus, siRNAs can be used to generate therapeutic compounds for different diseases, including those that are currently 'undruggable'. This has led siRNA-based therapeutic compounds to break into clinical settings, with them holding the promise to potentially revolutionise therapeutic approaches. To date, the United States Food and Drug Administration (FDA) have approved 5 compounds for treating different diseases including hypercholesterolemia, transthyretin-mediated amyloidosis (which leads to polyneuropathy), hepatic porphyria, and hyperoxaluria. This current article presents an overview of the molecular mechanisms involved in the selective pharmacological actions of siRNA-based compounds. It also describes the ongoing clinical trials of siRNA-based therapeutic compounds for hepatic diseases, pulmonary diseases, atherosclerosis, hypertriglyceridemia, transthyretin-mediated amyloidosis, and hyperoxaluria, kidney diseases, and haemophilia, as well as providing a description of FDA-approved siRNA therapies. Because of space constraints and to provide an otherwise comprehensive review, siRNA-based compounds applied to cancer therapies have been excluded. Finally, we discuss how the use of lipid-based nanoparticles to deliver siRNAs holds promise for selectively targeting mRNA-encoding proteins associated with the genesis of different diseases. Thus, siRNAs can help reduce the cellular levels of these proteins, thereby contributing to disease treatment. As consequence, a marked increase in the number of marketed siRNA-based medicines is expected in the next two decades, which will likely open up a new era of therapeutics.

Overcoming Resistance to Immune Checkpoint Inhibitor Therapy Using Calreticulin-Inducing Nanoparticle

Nanoparticles (NPs) have the ability to transform poorly immunogenic tumors into activated 'hot' targets. In this study, we investigated the potential of a liposome-based nanoparticle (CRT-NP) expressing calreticulin as an in-situ vaccine to restore sensitivity to anti-CTLA4 immune checkpoint inhibitor (ICI) in CT26 colon tumors. We found that a CRT-NP with a hydrodynamic diameter of approximately 300 nm and a zeta potential of approximately +20 mV induced immunogenic cell death (ICD) in CT-26 cells in a dose-dependent manner. In the mouse model of CT26 xenograft tumors, both CRT-NP and ICI monotherapy caused moderate reductions in tumor growth compared to the untreated control group. However, the combination therapy of CRT-NP and anti-CTLA4 ICI resulted in remarkable suppression of tumor growth rates (>70%) compared to untreated mice. This combination therapy also reshaped the tumor microenvironment (TME), achieving the increased infiltration of antigen-presenting cells (APCs) such as dendritic cells and M1 macrophages, as well as an abundance of T cells expressing granzyme B and a reduction in the population of CD4+ Foxp3 regulatory cells. Our findings indicate that CRT-NPs can effectively reverse immune resistance to anti-CTLA4 ICI therapy in mice, thereby improving the immunotherapeutic outcome in the mouse model.

Theory of self-coacervation in semi-dilute and concentrated zwitterionic polymer solutions

Based on the random phase approximation, we develop a molecular theory of self-coacervation in zwitterionic polymer solutions. We show that the interplay between the volume interactions of the monomeric units and electrostatic correlations of charged groups on a polymer backbone can result in liquid-liquid phase separation (self-coacervation). We analyse the behavior of the coacervate phase polymer concentration depending on the electrostatic interaction strength - the ratio of the Bjerrum length to the bond length of the chain. We establish that in a wide range of polymer concentration values - from a semi-dilute to a rather concentrated solution - the chain connectivity and excluded volume interaction of the monomeric units have an extremely weak effect on the contribution of the electrostatic interactions of the dipolar monomeric units to the total free energy. We show that for rather weak electrostatic interactions, the electrostatic correlations manifest themselves as Keesom interactions of point-like freely rotating dipoles (Keesom regime), while in the region of strong electrostatic interactions the electrostatic free energy is described by the Debye-Hückel limiting law (Debye regime). We show that for real zwitterionic coacervates the Keesom regime is realized only for sufficiently small polymer concentrations of the coacervate phase, while the Debye regime is approximately realized for rather dense coacervates. Using the mean-field variant of the density functional theory, we calculate the surface tension (surface free energy) of the "coacervate-solvent" interface as a function of the bulk polymer concentration. Obtained results can be used to estimate the parameters of the polymer chains needed for practical applications such as drug encapsulation and delivery, as well as the design of adhesive materials.

Review on Different Vesicular Drug Delivery Systems (VDDSs) and Their Applications

BACKGROUND

Colloidal dispersions, also known as vesicular drug delivery systems (VDDSs), are highly ordered assemblies composed of one or more concentric bilayers formed by the self-assembly of amphiphilic building blocks in the presence of water.

OBJECTIVE

VDDSs are important to target the entrapped drugs at specific sites inside the body, control the drug release, enhance the drug bioavailability, and reduce undesired side effects.

METHODS

There are different types of VDDSs suitable for the entrapment of both hydrophilic and lipophilic drugs. According to the patent composition, VDDSs are classified into lipid-based and nonlipid- based VDDSs.

RESULTS

There are different types of VDDSs which include liposomes, ethosomes, transferosomes, ufasomes, colloidosomes, cubosomes, niosomes, bilosomes, aquasomes, etc. Conclusion: This review article aims to address the different types of VDDSs, their advantages and disadvantages, and their therapeutic applications.

Mechanistic Insights into the Superior DNA Delivery Efficiency of Multicomponent Lipid Nanoparticles: An In Vitro and In Vivo Study

Lipid nanoparticles (LNPs) are currently having an increasing impact on nanomedicines as delivery agents, among others, of RNA molecules (e.g., short interfering RNA for the treatment of hereditary diseases or messenger RNA for the development of COVID-19 vaccines). Despite this, the delivery of plasmid DNA (pDNA) by LNPs in preclinical studies is still unsatisfactory, mainly due to the lack of systematic structural and functional studies on DNA-loaded LNPs. To tackle this issue, we developed, characterized, and tested a library of 16 multicomponent DNA-loaded LNPs which were prepared by microfluidics and differed in lipid composition, surface functionalization, and manufacturing factors. 8 out of 16 formulations exhibited proper size and zeta potential and passed to the validation step, that is, the simultaneous quantification of transfection efficiency and cell viability in human embryonic kidney cells (HEK-293). The most efficient formulation (LNP15) was then successfully validated both in vitro, in an immortalized adult keratinocyte cell line (HaCaT) and in an epidermoid cervical cancer cell line (CaSki), and in vivo as a nanocarrier to deliver a cancer vaccine against the benchmark target tyrosine-kinase receptor HER2 in C57BL/6 mice. Finally, by a combination of confocal microscopy, transmission electron microscopy and synchrotron small-angle X-ray scattering, we were able to show that the superior efficiency of LNP15 can be linked to its disordered nanostructure consisting of small-size unoriented layers of pDNA sandwiched between closely apposed lipid membranes that undergo massive destabilization upon interaction with cellular lipids. Our results provide new insights into the structure-activity relationship of pDNA-loaded LNPs and pave the way to the clinical translation of this gene delivery technology.

Tailoring Lipid-Based Drug Delivery Nanosystems by Synchrotron Small Angle X-ray Scattering

Thanks to specific physico-chemical properties, drug delivery systems based on nanoparticles have proven to effectively transport delicate molecules for therapeutic purposes, protecting them from degradation, increasing their stability in the blood circulation and allowing to convey and release the transported substances in specific areas of the body. Nanoparticles obtained from biopolymers for applications in medicine and pharmaceutics have become particularly popular in recent years due to the enormous research effort in the field of vaccines to respond to the pandemic emergency. Among the various types of biopolymers used to produce nanoparticles for therapeutics, lipids have characteristics that make them biocompatible, with low toxicity and ease of clearance. They can be synthesized by designing their characteristics according to the foreseen administration path, or to the target of the transported drug. The analytical methods mostly used to evaluate the characteristics of lipid nanosytems for drug delivery involve studying their effects on cells, in vitro and in vivo. Although it is often considered a "niche technique" for research in the bio-related sciences, Small Angle X-ray Scattering (SAXS) is a versatile tool to study the structure of nanosystems based on lipids, both ex situ and in situ. Therefore, it allows to evaluate both the effect of the different synthesis parameters and of the exposure of lipid nanoparticles to physiological conditions, which is of fundamental importance to design efficient drug delivery systems. In this mini-review, we will report some recent examples of characterization and design of nanoparticles based on lipids, where SAXS has been a fundamental step both to guide the synthesis of nanomaterials with tailored characteristics, and to understand the interaction between nanomaterials and cells.

Recent advances in gene therapy: genetic bullets to the root of the problem

Genetics and molecular genetic techniques have changed many perspectives and paradigms in medicine. Using genetic methods, many diseases have been cured or alleviated. Gene therapy, in its simplest definition, is application of genetic materials and related techniques to treat various human diseases. Evaluation of the trends in the field of medicine and therapeutics clarifies that gene therapy has attracted a lot of attention due to its powerful potential to treat a number of diseases. There are various genetic materials that can be used in gene therapy such as DNA, single- and double-stranded RNA, siRNA and shRNA. The main gene editing techniques used for in vitro and in vivo gene modification are ZNF, TALEN and CRISPR-Cas9. The latter has increased hopes for more precise and efficient gene targeting as it requires two separate recognition sites which makes it more specific and can also cause rapid and sufficient cleavage within the target sequence. There must be carriers for delivering genes to the target tissue. The most commonly used carriers for this purpose are viral vectors such as adenoviruses, adeno-associated viruses and lentiviruses. Non-viral vectors consist of bacterial vectors, liposomes, dendrimers and nanoparticles.

Efficient Delivery of DNA Using Lipid Nanoparticles

DNA vaccination has been extensively studied as a promising strategy for tumor treatment. Despite the efforts, the therapeutic efficacy of DNA vaccines has been limited by their intrinsic poor cellular internalization. Electroporation, which is based on the application of a controlled electric field to enhance DNA penetration into cells, has been the method of choice to produce acceptable levels of gene transfer in vivo. However, this method may cause cell damage or rupture, non-specific targeting, and even degradation of pDNA. Skin irritation, muscle contractions, pain, alterations in skin structure, and irreversible cell damage have been frequently reported. To overcome these limitations, in this work, we use a microfluidic platform to generate DNA-loaded lipid nanoparticles (LNPs) which are then characterized by a combination of dynamic light scattering (DLS), synchrotron small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Despite the clinical successes obtained by LNPs for mRNA and siRNA delivery, little is known about LNPs encapsulating bulkier DNA molecules, the clinical application of which remains challenging. For in vitro screening, LNPs were administered to human embryonic kidney 293 (HEK-293) and Chinese hamster ovary (CHO) cell lines and ranked for their transfection efficiency (TE) and cytotoxicity. The LNP formulation exhibiting the highest TE and the lowest cytotoxicity was then tested for the delivery of the DNA vaccine pVAX-hECTM targeting the human neoantigen HER2, an oncoprotein overexpressed in several cancer types. Using fluorescence-activated cell sorting (FACS), immunofluorescence assays and fluorescence confocal microscopy (FCS), we proved that pVAX-hECTM-loaded LNPs produce massive expression of the HER2 antigen on the cell membrane of HEK-293 cells. Our results provide new insights into the structure–activity relationship of DNA-loaded LNPs and pave the way for the access of this gene delivery technology to preclinical studies.

Hemiacetal-linked pH-sensitive PEG-lipids for non-viral gene delivery

Cationic lipid–DNA complexes containing a novel hemiacetal PEG-lipid for endosomal escape were characterized in terms of pH-response, stability, and biological activity.

Correlation between Biophysical Properties of Niosomes Elaborated with Chloroquine and Different Tensioactives and Their Transfection Efficiency

Lipid nanocarriers, such as niosomes, are considered attractive candidates for non-viral gene delivery due to their suitable biocompatibility and high versatility. In this work, we studied the influence of incorporating chloroquine in niosomes biophysical performance, as well as the effect of non-ionic surfactant composition and protocol of incorporation in their biophysical performance. An exhaustive comparative evaluation of three niosome formulations differing in these parameters was performed, which included the analysis of their thermal stability, rheological behavior, mean particle size, dispersity, zeta potential, morphology, membrane packing capacity, affinity to bind DNA, ability to release and protect the genetic material, buffering capacity and ability to escape from artificially synthesized lysosomes. Finally, in vitro biological studies were, also, performed in order to determine the compatibility of the formulations with biological systems, their transfection efficiency and transgene expression. Results revealed that the incorporation of chloroquine in niosome formulations improved their biophysical properties and the transfection efficiency, while the substitution of one of the non-ionic surfactants and the phase of addition resulted in less biophysical variations. Of note, the present work provides several biophysical parameters and characterization strategies that could be used as gold standard for gene therapy nanosystems evaluation.

Microfluidic Formulation of DNA-Loaded Multicomponent Lipid Nanoparticles for Gene Delivery

In recent years, lipid nanoparticles (LNPs) have gained considerable attention in numerous research fields ranging from gene therapy to cancer immunotherapy and DNA vaccination. While some RNA-encapsulating LNP formulations passed clinical trials, DNA-loaded LNPs have been only marginally explored so far. To fulfil this gap, herein we investigated the effect of several factors influencing the microfluidic formulation and transfection behavior of DNA-loaded LNPs such as PEGylation, total flow rate (TFR), concentration and particle density at the cell surface. We show that PEGylation and post-synthesis sample concentration facilitated formulation of homogeneous and small size LNPs with high transfection efficiency and minor, if any, cytotoxicity on human Embryonic Kidney293 (HEK-293), spontaneously immortalized human keratinocytes (HaCaT), immortalized keratinocytes (N/TERT) generated from the transduction of human primary keratinocytes, and epidermoid cervical cancer (CaSki) cell lines. On the other side, increasing TFR had a detrimental effect both on the physicochemical properties and transfection properties of LNPs. Lastly, the effect of particle concentration at the cell surface on the transfection efficiency (TE) and cell viability was largely dependent on the cell line, suggesting that its case-by-case optimization would be necessary. Overall, we demonstrate that fine tuning formulation and microfluidic parameters is a vital step for the generation of highly efficient DNA-loaded LNPs.

A nucleic acid nanogel dually bears siRNA and CpG motifs for synergistic tumor immunotherapy

The immune system plays a key role in restraining tumor progression. Therefore, enhancing immune functions using immune stimulants, such as unmethylated CpG oligonucleotides, has emerged as a promising strategy for antitumor therapy. However, poor cellular uptake of negatively charged oligonucleotides and M2 polarization of tumor-associated macrophages remain two major challenges for CpG-based immunotherapy. Herein, we construct a spherical nucleic acid (SNA)-like nanogel assembled by a CpG-grafted polycaprolactone (CpG-g-PCL) brush and an anti-STAT3 siRNA crosslinker for synergistic tumor immunotherapy. After accumulation at the tumor site, this dual siRNA- and CpG-bearing nanogel (CpGgel-siSTAT3) can efficiently trigger M1 type macrophage activation and deter its M2 polarization via block STAT3 signaling, increase the intratumor CD8⁺ T cell infiltration, and thus successfully restrain tumor growth. Our study demonstrates the new potential of a nucleic acid nanogel platform for the co-delivery of different therapeutic oligonucleotides and combinatorial CpG-based immunotherapy.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

A brain glioma gene delivery strategy by angiopep-2 and TAT-modified magnetic lipid-polymer hybrid nanoparticles

Owing to the existence of the blood-brain barrier (BBB), most treatments cannot achieve significant effects on gliomas. In this study, synergistic multitarget Ang-TAT-Fe3O4-pDNA-(ss)373 lipid-polymer hybrid nanoparticles (LPNPs) were designed to penetrate the BBB and deliver therapeutic genes to glioma cells. The basic material of the nanoparticles was PCL3750-ss-PEG7500-ss-PCL3750, and is called (ss)373 herein. (ss)373 NPs, Fe3O4 magnetic nanoparticles (MNPs), DOTAP, and DSPE-PEG-MAL formed the basic structure of LPNPs by self-assembly. The Fe3O4 MNPs were wrapped in (ss)373 NPs to implement magnetic targeting. Then, the Angiopep-2 peptide (Ang) and transactivator of transcription (TAT) were coupled with DSPE-PEG-MAL. Both can enhance BBB penetration and tumor targeting. Finally, the pDNA was compressed on DOTAP to form the complete gene delivery system. The results indicated that the Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs were 302.33 nm in size. In addition, their zeta potential was 4.66 mV, and they had good biocompatibility. The optimal nanoparticles/pDNA ratio was 5 : 1, as shown by gel retardation assay. In this characterization, compared with other LPNPs, the modified single Ang or without the addition of the Fe3O4 MNPs, the penetration efficiency of the BBB model formed by hCMEC/D3 cells, and the transfection efficiency of C6 cells using pEGFP-C1 as the reporter gene were significantly improved with Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs in the magnetic field.

Lipid-Nucleic Acid Complexes: Physicochemical Aspects and Prospects for Cancer Treatment

Cancer is an extremely complex disease, typically caused by mutations in cancer-critical genes. By delivering therapeutic nucleic acids (NAs) to patients, gene therapy offers the possibility to supplement, repair or silence such faulty genes or to stimulate their immune system to fight the disease. While the challenges of gene therapy for cancer are significant, the latter approach (a type of immunotherapy) starts showing promising results in early-stage clinical trials. One important advantage of NA-based cancer therapies over synthetic drugs and protein treatments is the prospect of a more universal approach to designing therapies. Designing NAs with different sequences, for different targets, can be achieved by using the same technologies. This versatility and scalability of NA drug design and production on demand open the way for more efficient, affordable and personalized cancer treatments in the future. However, the delivery of exogenous therapeutic NAs into the patients’ targeted cells is also challenging. Membrane-type lipids exhibiting permanent or transient cationic character have been shown to associate with NAs (anionic), forming nanosized lipid-NA complexes. These complexes form a wide variety of nanostructures, depending on the global formulation composition and properties of the lipids and NAs. Importantly, these different lipid-NA nanostructures interact with cells via different mechanisms and their therapeutic potential can be optimized to promising levels in vitro. The complexes are also highly customizable in terms of surface charge and functionalization to allow a wide range of targeting and smart-release properties. Most importantly, these synthetic particles offer possibilities for scaling-up and affordability for the population at large. Hence, the versatility and scalability of these particles seem ideal to accommodate the versatility that NA therapies offer. While in vivo efficiency of lipid-NA complexes is still poor in most cases, the advances achieved in the last three decades are significant and very recently a lipid-based gene therapy medicine was approved for the first time (for treatment of hereditary transthyretin amyloidosis). Although the path to achieve efficient NA-delivery in cancer therapy is still long and tenuous, these advances set a new hope for more treatments in the future. In this review, we attempt to cover the most important biophysical and physicochemical aspects of non-viral lipid-based gene therapy formulations, with a perspective on future cancer treatments in mind.

Non-viral mediated gene therapy in human cystic fibrosis airway epithelial cells recovers chloride channel functionality

Gene therapy strategies based on non-viral vectors are currently considered as a promising therapeutic option for the treatment of cystic fibrosis (CF), being liposomes the most commonly used gene carriers. Niosomes offer a powerful alternative to liposomes due to their higher stability and lower cytotoxicity, provided by their non-ionic surfactant and helper components. In this work, a three-formulation screening is performed, in terms of physicochemical and biological behavior, in CF patient derived airway epithelial cells. The most efficient niosome formulation reaches 28% of EGFP expressing live cells and follows caveolae-mediated endocytosis. Transfection with therapeutic cystic fibrosis transmembrane conductance regulator (CFTR) gene results in 5-fold increase of CFTR protein expression in transfected versus non-transfected cells, which leads to 1.5-fold increment of the chloride channel functionality. These findings highlight the relevance of niosome-based systems as an encouraging non-viral gene therapy platform with potential therapeutic benefits for CF.

Lipid-Based Drug Delivery Nanoplatforms for Colorectal Cancer Therapy

Colorectal cancer (CRC) is a prevalent disease worldwide, and patients at late stages of CRC often suffer from a high mortality rate after surgery. Adjuvant chemotherapeutics (ACs) have been extensively developed to improve the survival rate of such patients, but conventionally formulated ACs inevitably distribute toxic chemotherapeutic drugs to healthy organs and thus often trigger severe side effects. CRC cells may also develop drug resistance following repeat dosing of conventional ACs, limiting their effectiveness. Given these limitations, researchers have sought to use targeted drug delivery systems (DDSs), specifically the nanotechnology-based DDSs, to deliver the ACs. As lipid-based nanoplatforms have shown the potential to improve the efficacy and safety of various cytotoxic drugs (such as paclitaxel and vincristine) in the clinical treatment of gastric cancer and leukemia, the preclinical progress of lipid-based nanoplatforms has attracted increasing interest. The lipid-based nanoplatforms might be the most promising DDSs to succeed in entering a clinical trial for CRC treatment. This review will briefly examine the history of preclinical research on lipid-based nanoplatforms, summarize the current progress, and discuss the challenges and prospects of using such approaches in the treatment of CRC.

Effect of Protein Corona on The Transfection Efficiency of Lipid-Coated Graphene Oxide-Based Cell Transfection Reagents

Coating graphene oxide nanoflakes with cationic lipids leads to highly homogeneous nanoparticles (GOCL NPs) with optimised physicochemical properties for gene delivery applications. In view of in vivo applications, here we use dynamic light scattering, micro-electrophoresis and one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis to explore the bionano interactions between GOCL/DNA complexes (hereafter referred to as "grapholipoplexes") and human plasma. When exposed to increasing protein concentrations, grapholipoplexes get covered by a protein corona that evolves with protein concentration, leading to biocoronated complexes with modified physicochemical properties. Here, we show that the formation of a protein corona dramatically changes the interactions of grapholipoplexes with four cancer cell lines: two breast cancer cell lines (MDA-MB and MCF-7 cells), a malignant glioma cell line (U-87 MG) and an epithelial colorectal adenocarcinoma cell line (CACO-2). Luciferase assay clearly indicates a monotonous reduction of the transfection efficiency of biocoronated grapholipoplexes as a function of protein concentration. Finally, we report evidence that a protein corona formed at high protein concentrations (as those present in in vivo studies) promotes a higher capture of biocoronated grapholipoplexes within degradative intracellular compartments (e.g., lysosomes), with respect to their pristine counterparts. On the other hand, coronas formed at low protein concentrations (human plasma = 2.5%) lead to high transfection efficiency with no appreciable cytotoxicity. We conclude with a critical assessment of relevant perspectives for the development of novel biocoronated gene delivery systems.

Membrane lipids destabilize short interfering ribonucleic acid (siRNA)/polyethylenimine nanoparticles

Cell entry of polymeric nanoparticles (NPs) bearing polynucleotides is an important stage for successful gene delivery. In this work, we addressed the influence of cell membrane lipids on the integrity and configurational changes of NPs composed of short interfering ribonucleic acid (siRNA) and polyethylenimine. We focused on NPs derived from two different PEIs, unmodified low molecular weight PEI and linoleic acid (LA)-substituted PEI, and their interactions with two membrane lipids (zwitterionic 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC) and anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS)). Our experiments showed that POPS liposomes interacted strongly with both types of NPs, which caused partial dissociation of the NPs. POPC liposomes, however, did not induce any dissociation. Consistent with the experiments, steered molecular dynamics simulations showed a stronger interaction between the NPs and the POPS membrane than between the NPs and the POPC membrane. Lipid substitution on the PEIs enhanced the stability of the NPs during membrane crossing; lipid association between PEIs of the LA-bearing NPs as well as parallel orientation of the siRNAs provided protection against their dissociation (unlike NPs from native PEI). Our observations provide valuable insight into the integrity and structural changes of PEI/siRNA NPs during membrane crossing which will help in the design of more effective carriers for nucleic acid delivery.

A mechanistic explanation of the inhibitory role of the protein corona on liposomal gene expression

The past three decades have witnessed fast advances in the use of cationic liposome-DNA complexes (lipoplexes) for gene delivery applications. However, no lipoplex formulation has reached into the clinical practice so far. The primary drawback limiting clinical use of lipoplexes is the lack of mechanistic understanding of their low transfection efficiency (TE) in vivo. In physiological environments, lipoplexes are coated by a protein corona (PC) that mediates the interactions with the cell machinery. Here we show that the formation of PC can change the interactions of multicomponent (MC) lipoplexes with our cell model (i.e., HeLa). At the highest lipoplex concentration, the formation of PC can reduce the TE of MC lipoplexes from 60% to <5%. Combining dynamic light scattering and synchrotron small-angle X-ray scattering (SAXS), we clarify that the formation of PC modifies physical-chemical properties of MC lipoplexes so as to affect their TE. Moreover, we examined single transfection barriers by a combination of fluorescence-activated cell sorting, single-cell real-time fluorescence confocal microscopy, and synchrotron SAXS. We demonstrate that PC formation has the ability to modify the relative contribution of caveolae-mediated endocytosis and macropinocytosis in lipoplexes uptake, in favor of the latter, increasing accumulation of PC-decorated lipoplexes into degradative lysosomal compartments. Finally, we report evidences that PC reduces the structural stability of lipoplexes against solubilization by cellular lipids, likely favoring premature DNA release and cytosolic digestion by DNAase. These combined effects revealed here offer a comprehensive mechanistic explanation on the reason behind reduction in gene expression of MC lipoplexes.

The Impact of Alkyl-Chain Purity on Lipid-Based Nucleic Acid Delivery Systems - Is the Utilization of Lipid Components with Technical Grade Justified?

The physicochemical properties and transfection efficacies of two samples of a cationic lipid have been investigated and compared in 2D (monolayers at the air/liquid interface) and 3D (aqueous bulk dispersions) model systems using different techniques. The samples differ only in their chain composition due to the purity of the oleylamine (chain precursor). Lipid 8 (using the oleylamine of technical grade for cost-efficient synthesis) shows lateral phase separation in the Langmuir layers. However, the amount of attached DNA, determined by IRRAS, is for both samples the same. In 3D systems, lipid 8 p forms cubic phases, which disappear after addition of DNA. At physiological temperatures, both lipids (alone and in mixture with cholesterol) assemble to lamellar aggregates and exhibit comparable DNA delivery efficiency. This study demonstrates that non-lamellar structures are not compulsory for high transfection rates. The results legitimate the utilization of oleyl chains of technical grade in the synthesis of cationic transfection lipids.

Interplay of protein corona and immune cells controls blood residency of liposomes

In vivo liposomes, like other types of nanoparticles, acquire a totally new 'biological identity' due to the formation of a biomolecular coating known as the protein corona that depends on and modifies the liposomes' synthetic identity. The liposome-protein corona is a dynamic interface that regulates the interaction of liposomes with the physiological environment. Here we show that the biological identity of liposomes is clearly linked to their sequestration from peripheral blood mononuclear cells (PBMCs) of healthy donors that ultimately leads to removal from the bloodstream. Pre-coating liposomes with an artificial corona made of human plasma proteins drastically reduces capture by circulating leukocytes in whole blood and may be an effective strategy to enable prolonged circulation in vivo. We conclude with a critical assessment of the key concepts of liposome technology that need to be reviewed for its definitive clinical translation.

Microfluidic manufacturing of surface-functionalized graphene oxide nanoflakes for gene delivery

Graphene oxide (GO) is a single-atomic-layered material made of a sheet of oxidized carbon atoms arranged in a honeycomb structure. Thanks to the notable physical and chemical properties of GO, GO-based nanomaterials have applications in many fields of research, including gene delivery. It has been reported that pristine GO can absorb single-stranded DNA and RNA through π-π stacking, which cannot be used as a gene carrier because it is hard to load double-stranded DNA (dsDNA). To tackle this issue, this work was aimed at developing a hybrid nanoparticle (NP) system made of GO coated with cationic lipids (hereafter referred to as GOCL) with suitable physical-chemical properties for gene delivery applications. To this end, nanosized GO flakes (nGO) were coated with the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) by microfluidic mixing. Comprehensive characterization of GOCL NPs was performed by a combination of dynamic light scattering (DLS), micro-electrophoresis and atom force microscopy (AFM). Our results show that GOCL NPs exhibit adequate size (<150 nm) and surface charge (ξ = +15 mV) for gene delivery purposes. Complexes made of GOCL NPs and plasmid DNA (pDNA) were used to transfect human cervical cancer cells (HeLa) and human embryonic kidney (HEK-293) cells. Pristine nGO and DOTAP cationic liposomes were used as a reference. GOCL NPs exhibited a similar TE but a much higher cell viability compared with DOTAP cationic liposomes. Confocal fluorescence microscopy provided a reasonable explanation for the superior performance of GOCL/DNA complexes showing that they are much more numerous, regular in size and homogeneously distributed than DOTAP/DNA complexes, thus splitting their gene payload over the entire cell population. Because of the imperative demand for efficient and safe nanocarriers, this study will contribute to the development of novel surface-functionalized GO-based hybrid gene vectors.

Brain Targeting by Liposome-Biomolecular Corona Boosts Anticancer Efficacy of Temozolomide in Glioblastoma Cells

Temozolomide (TMZ) is the current first-line chemotherapy for treatment of glioblastoma multiforme (GBM). However, similar to other brain therapeutic compounds, access of TMZ to brain tumors is impaired by the blood-brain barrier (BBB) leading to poor response for GBM patients. To overcome this major hurdle, we have synthesized a set of TMZ-encapsulating nanomedicines made of four cationic liposome (CL) formulations with systematic changes in lipid composition and physical-chemical properties. The targeting nature of this nanomedicine is provided by the recruitment of proteins, with natural targeting capacity, in the biomolecular corona (BC) layer that forms around CLs after exposure to human plasma (HP). TMZ-loaded CL-BC complexes were thoroughly characterized by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and nanoliquid chromatography tandem mass spectrometry (nano-LC MS/MS). BCs were found to be enriched of typical BC fingerprints (BCFs) (e.g., Apolipoproteins, Vitronectin, and vitamin K-dependent protein), which have a substantial capacity in binding to receptors that are overexpressed at the BBB (e.g., scavenger receptor class B, type I and low-density lipoprotein receptor). We found that the CL formulation exhibiting the highest levels of targeting BCFs had larger uptake in human umbilical vein endothelial cells (HUVECs) that are commonly used as an in vitro model of the BBB. This formulation could also deliver TMZ to the human glioblastoma U-87 MG cell line and thus substantially enhance their antitumor efficacy compared to corona free CLs. Thus, we propose that the BC-based nanomedicines may pave a more effective way for efficient treatment of GBM.

Preparation of gene drug delivery systems of cationic peptide lipid with 0G-PAMAM as hydrophilic end and its biological properties evaluation

As an efficient gene delivery, non-viral vectors should have high transfection efficiency, excellent endosomal escape, low cytotoxicity, and the ability to rapidly release the gene into the cytoplasm.Cationic liposome have been widely used as efficient gene carriers, but the cytotoxicity, rapid degradation and low cellular uptake are major drawback impeding its further appolication. Herein, with double lauric acid as hydrophobic chains, tartaric acid as skeleton, 0 generation PAMAM modified with lysine as hydrophilic head, a new type cationic peptide lipid was synthetised. The alkyl chain promote lipid across cell membranes and with membrane fusion, 0 generation PAMAM modified with lysine hydrophilic end amino can contain a large number of protons which can change into ammonium and combine with the DNA negatively charge phosphate groups. It is expected that this carrier has low toxicity, high transfection efficiency and targeting property. By adjusting the cationic liposome/gene weight ratio, the transfection system was optimized to improved gene transfection efficiency, reduce cytotoxicity, and increase property and stability, etc.

Hyaluronic acid hydrogel scaffolds loaded with cationic niosomes for efficient non-viral gene delivery

The lack of ideal non-viral gene carriers has motivated the combination of delivery systems and tissue-engineered scaffolds, which may offer relevant advantages such as enhanced stability and reduced toxicity. In this work, we evaluated a new combination between niosome non-viral vectors and hyaluronic acid (HA) hydrogel scaffolds, both widely studied due to their biocompatibility as well as their ability to incorporate a wide variety of molecules. We evaluated three different niosome formulations (niosomes 1, 2 and 3) varying in composition of cationic lipid, helper lipid and non-ionic tensioactives. Niosomes and nioplexes obtained upon the addition of plasmid DNA were characterized in terms of size, polydispersity, zeta potential and ability to transfect mouse bone marrow cloned mesenchymal stem cells (mMSCs) in 2D culture. Niosome 1 was selected for encapsulation in HA hydrogels due to its higher transfection efficiency and the formulation was concentrated in order to be able to incorporate higher amounts of DNA within HA hydrogels. Nioplex-loaded HA hydrogels were characterized in terms of biomechanical properties, particle distribution, nioplex release kinetics and ability to transfect encapsulated mMSCs in 3D culture. Our results showed that nioplex-loaded HA hydrogel scaffolds presented little or no particle aggregation, allowed for extensive cell spreading and were able to efficiently transfect encapsulated mMSCs with high cellular viability. We believe that the knowledge gained through this in vitro model can be utilized to design novel and effective platforms for in vivo local and non-viral gene delivery applications.

Nioplexes encapsulated in HA hydrogel scaffolds present no particle aggregation, incorporate high amount of DNA, allow extensive cell spreading and are able to efficiently transfect mesenchymal stem cells in 3D cultures with high cellular viability.

Polysorbate 20 non-ionic surfactant enhances retinal gene delivery efficiency of cationic niosomes after intravitreal and subretinal administration

The success of non-viral vectors based on cationic niosomes for retinal gene delivery applications depends on the ability to achieve persistent and high levels of transgene expression, ideally from a single administration. In this work, we studied the effect of the non-ionic surfactant component of niosomes in their transfection efficiency in rat retina. For that purpose, three niosome formulations that only differed in the non-ionic tensioactives were elaborated. Niosomes contained: cationic lipid 1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA), helper lipid squalene and polysorbate 20, polysorbate 80 or polysorbate 85. Niosomes and corresponding nioplexes were fully characterized in terms of size, polydispersity index, zeta potential, morphology and ability to protect and release DNA. In vitro experiments were carried out to evaluate transfection efficiency, cell viability and intracellular trafficking pathways of the formulations. Nioplexes based on polysorbate 20 niosomes were the most efficient transfecting retinal cells in vitro. Moreover, subretinal and intravitreal administration of those nioplexes in vivo showed also high levels of transgene expression in rat retinas. Our results demonstrate that the incorporation of polysorbate 20 in cationic niosomes enhances retinal gene delivery. Thus, this formulation emerges as a potential non-viral candidate to efficiently transfer specific therapeutic genes into the eye for biomedical purposes.

AS1411-decorated niosomes as effective nanocarriers for Ru(iii)-based drugs in anticancer strategies

Niosomes are self-assembled vesicles made up of single chain non-ionic surfactants combined with appropriate amounts of cholesterol or other lipids, exploited as carriers for hydrophilic or lipophilic drugs. Compared to liposomes, niosomes are typically more stable, less expensive and, being generally obtained from synthetic surfactants, more easily derivatizable, providing vesicular structures with a higher versatility and chemical diversity. Herein, we investigated the physico-chemical and biological properties of niosomes loaded with two active ingredients, i.e. the nucleolipidic Ru(iii)-complex HoThyRu, selected as an anticancer agent, and the nucleolin-targeting AS1411 aptamer, allowing selective recognition of cancer cells. The morphology, average size, zeta potential, electrophoretic mobility, and stability over time of the functionalized niosomes were analyzed using different biophysical techniques. These formulations, tested on both cancer and normal cells, showed promising antiproliferative activity on HeLa cells, with a higher efficacy associated with the nanosystems containing both AS1411 and HoThyRu with respect to the controls. In all the tested cell lines, AS1411 proved to markedly enhance the bioactivity of the Ru(iii)-containing niosomes.

Transfection of plasmid DNA by nanocarriers containing a gemini cationic lipid with an aromatic spacer or its monomeric counterpart

This study performed a biophysical characterization (electrochemistry, structure and morphology) and assessment of the biological activity and cell biocompatibility of GCL/DOPE-pDNA lipoplexes comprised of plasmid DNA and a mixed lipid formed by a DOPE zwitterionic lipid and a gemini cationic lipid N-N'-(1,3-phenylene bis (methylene)) bis (N,N-dimethyl-N-(1-dodecyl) ammonium dibromide (12PH12) containing an aromatic spacer or its monomeric counterpart surfactant, N-benzyl-N,N-dimethyl-N-(1-dodecyl) ammonium bromide (12PH). Electrochemical results reveal that i) the gemini cationic lipid (12PH12) and the plasmid pDNA yield effective charges less than their nominal charges (+2 and -2/bp, respectively) and that ii) both vectors (12PH12/DOPE and 12PH/DOPE) could compact pDNA and protect it from DNase I degradation. SAXS and cryo-TEM experiments indicate the presence of a lamellar lyotropic liquid crystal phase represented as alternating layers of mixed lipid and plasmid. Transfection efficiency (by FACS and luminometry) and cell viability assay in COS-7 cells, performed with two plasmid DNAs (pEGFP-C3 and pCMV-Luc VR1216), confirm the goodness of the proposed formulations (12PH12/DOPE and 12PH/DOPE) to transport genetic material, with efficiencies and biocompatibilities comparable to or better than those exhibited by the control Lipofectamine 2000*. In conclusion, although major attention has been paid to gemini cationic lipids in the literature, due to the large variety of modifications that their structures may support to improve the biological activity of the resulting lipoplexes, it is remarkable that the monomeric counterpart surfactant with an aromatic group analyzed in the present work also exhibits good biological activity. The in vitro results reported here indicate that the optimum formulations of the gene vectors studied in this work efficiently transfect plasmid DNA with very low toxicity levels and, thus, may be used in forthcoming in vivo experiments.

Structural insights on biologically relevant cationic membranes by ESR spectroscopy

Cationic bilayers have been used as models to study membrane fusion, templates for polymerization and deposition of materials, carriers of nucleic acids and hydrophobic drugs, microbicidal agents and vaccine adjuvants. The versatility of these membranes depends on their structure. Electron spin resonance (ESR) spectroscopy is a powerful technique that employs hydrophobic spin labels to probe membrane structure and packing. The focus of this review is the extensive structural characterization of cationic membranes prepared with dioctadecyldimethylammonium bromide or diC14-amidine to illustrate how ESR spectroscopy can provide important structural information on bilayer thermotropic behavior, gel and fluid phases, phase coexistence, presence of bilayer interdigitation, membrane fusion and interactions with other biologically relevant molecules.

Clinically approved PEGylated nanoparticles are covered by a protein corona that boosts the uptake by cancer cells

Today, liposomes are an advanced technology of drug carriers with a dozen drugs in clinical practice and many more in clinical trials. A bottleneck associated with the clinical translation of liposomes has long been 'opsonization', i.e. the adsorption of plasma proteins at the liposome surface resulting in their rapid clearance from circulation. For decades, the most popular way to avoid opsonization has been grafting polyethylene glycol (PEG) onto the liposome surface. Recent studies have clarified that grafting PEG onto the liposome surface reduces, but does not completely prevent protein binding. In this work, we employed dynamic light scattering, zeta-potential analysis, one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1D-SDS-PAGE), semi-quantitative densitometry and cell imaging to explore the bio-nano-interactions between human plasma (HP) and Onivyde, a PEGylated liposomal drug that has recently been approved by the Food and Drug Administration (FDA) for the treatment of metastatic pancreatic ductal adenocarcinoma (PDAC). To properly evaluate the role of PEGylation, an unPEGylated variant of Onivyde was used as a reference. Collectively, our findings suggest that: (i) although PEGylated, Onivyde is not "stealth" in HP; (ii) surface chemistry is more important than PEGylation in controlling the bio-nano-interactions between Onivyde and plasma components. Of note is that the PC was found to boost the cellular uptake of Onivyde in the pancreas ductal adenocarcinoma cell line (PANC-1) thus suggesting its prominent role in its indication for PDAC treatment. Relevant implications for drug delivery and drug design are discussed.

Cationic Nanoliposomes Meet mRNA: Efficient Delivery of Modified mRNA Using Hemocompatible and Stable Vectors for Therapeutic Applications

Synthetically modified mRNA is a unique bioactive agent, ideal for use in therapeutic applications, such as cancer vaccination or treatment of single-gene disorders. In order to facilitate mRNA transfections for future therapeutic applications, there is a need for the delivery system to achieve optimal transfection efficacy, perform with durable stability, and provide drug safety. The objective of our study was to comprehensively analyze the use of 3β-[N-(N',N'-dimethylaminoethane) carbamoyl](DC-Cholesterol)/dioleoylphosphatidylethanolamine (DOPE) liposomes as a potential transfection agent for modified mRNAs. Our cationic liposomes facilitated a high degree of mRNA encapsulation and successful cell transfection efficiencies. More importantly, no negative effects on cell viability or immune reactions were detected posttransfection. Notably, the liposomes had a long-acting transfection effect on cells, resulting in a prolonged protein production of alpha-1-antitrypsin (AAT). In addition, the stability of these mRNA-loaded liposomes allowed storage for 80 days, without the loss of transfection efficacy. Finally, comprehensive analysis showed that these liposomes are fully hemocompatible with fresh human whole blood. In summary, we present an extensive analysis on the use of DC-cholesterol/DOPE liposomes as mRNA delivery vehicles. This approach provides the basis of a safe and efficient therapeutic strategy in the development of successful mRNA-based drugs.

Biophysics and protein corona analysis of Janus cyclodextrin-DNA nanocomplexes. Efficient cellular transfection on cancer cells

The self-assembling processes underlining the capabilities of facially differentiated ("Janus") polycationic amphiphilic cyclodextrins (paCDs) as non-viral gene nanocarriers have been investigated by a pluridisciplinary approach. Three representative Janus paCDs bearing a common tetradecahexanoyl multitail domain at the secondary face and differing in the topology of the cluster of amino groups at the primary side were selected for this study. All of them compact pEGFP-C3 plasmid DNA and promote transfection in HeLa and MCF-7 cells, both in absence and in presence of human serum. The electrochemical and structural characteristics of the paCD-pDNA complexes (CDplexes) have been studied by using zeta potential, DLS, SAXS, and cryo-TEM. paCDs and pDNA, when assembled in CDplexes, render effective charges that are lower than the nominal ones. The CDplexes show a self-assembling pattern corresponding to multilamellar lyotropic liquid crystal phases, characterized by a lamellar stacking of bilayers of the CD-based vectors with anionic pDNA sandwiched among them. When exposed to human serum, either in the absence or in the presence of pDNA, the surface of the cationic CD-based vector becomes coated by a protein corona (PC) whose composition has been analyzed by nanoLC-MS/MS. Some of the CDplexes herein studied showed moderate-to-high transfection levels in HeLa and MCF-7 cancer cells combined with moderate-to-high cell viabilities, as determined by FACS and MTT reduction assays. The ensemble of data provides a detail picture of the paCD-pDNA-PC association processes and a rational base to exploit the protein corona for targeted gene delivery on future in vivo applications.

A biophysical study of gene nanocarriers formed by anionic/zwitterionic mixed lipids and pillar[5]arene polycationic macrocycles

A multivalent cationic macrocycle is used as a mediator between plasmid DNAs and anionic lipids (ALs) to build an efficient and safe gene nanocarrier.

Efficient Cellular Knockdown Mediated by siRNA Nanovectors of Gemini Cationic Lipids Having Delocalizable Headgroups and Oligo-Oxyethylene Spacers

The use of small interfering RNAs (siRNAs) to silence specific genes is one of the most promising approaches in gene therapy, but it requires efficient nanovectors for successful cellular delivery. Recently, we reported liposomal gene carriers derived from a gemini cationic lipid (GCL) of the 1,2-bis(hexadecyl dimethyl imidazolium) oligo-oxyethylene series ((C16Im)2(C2H4O)nC2H4 with n = 1, 2, or 3) and 1,2-dioleyol phosphatidylethanolamine as highly efficient cytofectins for pDNA. On the basis of the satisfactory outcomes of the previous study, the present work focuses on the utility of coliposomes of these gemini lipids with the biocompatible neutral lipid mono oleoyl glycerol (MOG) as highly potent vectors for siRNA cellular transport in the presence of serum. The (C16Im)2(C2H4O)nC2H4/MOG-siRNA lipoplexes were characterized through (i) a physicochemical study (zeta potential, cryo-transmission electron microscopy, small-angle X-ray scattering, and fluorescence anisotropy) to establish the relationship between size, structure, fluidity, and the interaction between siRNA and the GCL/MOG gene vectors and (ii) a biological analysis (flow cytometry, fluorescence microscopy, and cell viability) to report the anti-GFP siRNA transfections in HEK 293T, HeLa, and H1299 cancer cell lines. The in vitro biological analysis confirms the cellular uptake and indicates that a short spacer, a very low molar fraction of GCL in the mixed lipid, and a moderate effective charge ratio of the lipoplex yielded maximum silencing efficacy. At these experimental conditions, the siRNA used in this work is compacted by the GCL/MOG nanovectors by forming two cubic structures (Ia3d and Pm3n) that are correlated with excellent silencing activity. These liposomal nanocarriers possess high silencing activity with a negligible cytotoxicity, which strongly supports their practical use for in vivo knockdown studies.

Mapping surface charge density of lipid bilayers by quantitative surface conductivity microscopy

Local surface charge density of lipid membranes influences membrane–protein interactions leading to distinct functions in all living cells, and it is a vital parameter in understanding membrane-binding mechanisms, liposome design and drug delivery. Despite the significance, no method has so far been capable of mapping surface charge densities under physiologically relevant conditions. Here, we use a scanning nanopipette setup (scanning ion-conductance microscope) combined with a novel algorithm to investigate the surface conductivity near supported lipid bilayers, and we present a new approach, quantitative surface conductivity microscopy (QSCM), capable of mapping surface charge density with high-quantitative precision and nanoscale resolution. The method is validated through an extensive theoretical analysis of the ionic current at the nanopipette tip, and we demonstrate the capacity of QSCM by mapping the surface charge density of model cationic, anionic and zwitterionic lipids with results accurately matching theoretical values.

Surface charges on lipid bilayers deeply influence the way proteins interact with cellular membranes, yet their precise quantification has proven challenging. Here, the authors report on a quantitative method to map and evaluate surface charge densities under physiological conditions.

Preparation and characterisation of the colistin-entrapped liposome driven by electrostatic interaction for intravenous administration

Potential use of liposome for polycationic colistin is hindered by their phospholipid membrane permeability. In this study, liposomes were modified with sodium cholesteryl sulphate (Chol-SO4(-)) for improving the colistin loading by enhancing the colistin-bilayer electrostatic attraction. We have evaluated two liposomes: colistin-entrapped liposome of Chol-SO4(-) (CCL) and coated Chol-SO4(-)/colistin complex liposome (CCCL). In comparison with CCL which formed large aggregates at Chol-SO4(-)/colistin charge ratio below 2:1, CCCL showed a smaller size less dependent on the charge ratio, probably arising from more colistin entrapped on the inner leaflet of bilayer. Both liposomes exhibited significantly increased entrapment efficiency as compared with the liposome without Chol-SO4(-). But colistin released upon dilution, implying free transfer of colistin through bilayers. Pharmacokinetics results showed the approximately four-fold increase in the plasma AUC0-8 h for CCCL and CCL as compared with colistin solution, showing potential benefit for infectious target localisation by prolonging the systemic circulation of colistin.