Stable and monodisperse lipoplex formulations for gene delivery

Elucidating Structural Configuration of Lipid Assemblies for mRNA Delivery Systems

The development of mRNA delivery systems utilizing lipid-based assemblies holds immense potential for precise control of gene expression and targeted therapeutic interventions. Despite advancements in lipid-based gene delivery systems, a critical knowledge gap remains in understanding how the biophysical characteristics of lipid assemblies and mRNA complexes influence these systems. Herein, we investigate the biophysical properties of cationic liposomes and their role in shaping mRNA lipoplexes by comparing various fabrication methods. Notably, an innovative fabrication technique called the liposome under cryo-assembly (LUCA) cycle, involving a precisely controlled freeze-thaw-vortex process, produces distinctive onion-like concentric multilamellar structures in cationic DOTAP/DOPE liposomes, in contrast to a conventional extrusion method that yields unilamellar liposomes. The inclusion of short-chain DHPC lipids further modulates the structure of cationic liposomes, transforming them from multilamellar to unilamellar structures during the LUCA cycle. Furthermore, the biophysical and biological evaluations of mRNA lipoplexes unveil that the optimal N/P charge ratio in the lipoplex can vary depending on the structure of initial cationic liposomes. Cryo-EM structural analysis demonstrates that multilamellar cationic liposomes induce two distinct interlamellar spacings in cationic lipoplexes, emphasizing the significant impact of the liposome structures on the final structure of mRNA lipoplexes. Taken together, our results provide an intriguing insight into the relationship between lipid assembly structures and the biophysical characteristics of the resulting lipoplexes. These relationships may open the door for advancing lipid-based mRNA delivery systems through more streamlined manufacturing processes.

Diffusion coefficient of cationic liposomes during lipoplex formation determines transfection efficiency in HepG2 cells

Cationic lipid-based lipoplexes are well-known for gene delivery. To determine the relationship between physicochemical characteristics and transfection efficiency, cationic liposomes of different sizes were prepared and incubated with plasmid DNA at different temperatures to form lipoplexes. We found that the liposome diffusion coefficient during lipoplex formation strongly correlated with the physicochemical characteristics of lipoplexes, accessibility of plasmid DNA in lipoplexes, and logarithm of gene expression per metabolic activity. Clathrin-mediated endocytosis was the major route for lipoplexes comprising 100 nm-liposomes, as reported previously. As liposome size increased, the major route shifted to lipid raft-mediated endocytosis. In addition, macropinocytosis was observed for all liposome sizes. The role of reactive oxygen species might depend on liposome size and endocytosis. Information from this study would be useful for understanding cationic lipoplex-mediated transfection.

Lipid-based nucleic acid therapeutics with in vivo efficacy

Synthetic vectors for therapeutic nucleic acid delivery are currently competing significantly with their viral counter parts due to their reduced immunogenicity, large payload capacity, and ease of manufacture under GMP-compliant norms. The approval of Onpattro, a lipid-based siRNA therapeutic, and the proven clinical success of two lipid-based COVID-19 vaccines from Pfizer-BioNTech, and Moderna heralded the specific advantages of lipid-based systems among all other synthetic nucleic acid carriers. Lipid-based systems with diverse payloads-plasmid DNA (pDNA), antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA (miRNA), small activating RNA (saRNA), and messenger RNA (mRNA)-are now becoming a mature technology, with growing impact in the clinic. Research over four decades identified the key factors determining the therapeutic success of these multi-component systems. Here, we discuss the main nucleic acid-based technologies, presenting their mechanism of action, delivery barriers facing them, the structural properties of the payload as well as the component lipids that regulate physicochemical properties, pharmacokinetics and biodistribution, efficacy, and toxicity of the resultant nanoparticles. We further detail on the formulation parameters, evolution of the manufacturing techniques that generate reproducible and scalable outputs, and key manufacturing aspects that enable control over physicochemical properties of the resultant particles. Preclinical applications of some of these formulations that were successfully translated from in vitro studies to animal models are subsequently discussed. Finally, clinical success and failure of these systems starting from 1993 to present are highlighted, in a holistic literature review focused on lipid-based nucleic acid delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Development of mRNA Vaccines/Therapeutics and Their Delivery System

The rapid development of mRNA vaccines has contributed to the management of the current coronavirus disease 2019 (COVID-19) pandemic, suggesting that this technology may be used to manage future outbreaks of infectious diseases. Because the antigens targeted by mRNA vaccines can be easily altered by simply changing the sequence present in the coding region of mRNA structures, it is more appropriate to develop vaccines, especially during rapidly developing outbreaks of infectious diseases. In addition to allowing rapid development, mRNA vaccines have great potential in inducing successful antigen-specific immunity by expressing target antigens in cells and simultaneously triggering immune responses. Indeed, the two COVID-19 mRNA vaccines approved by the U.S. Food and Drug Administration have shown significant efficacy in preventing infections. The ability of mRNAs to produce target proteins that are defective in specific diseases has enabled the development of options to treat intractable diseases. Clinical applications of mRNA vaccines/therapeutics require strategies to safely deliver the RNA molecules into targeted cells. The present review summarizes current knowledge about mRNA vaccines/ therapeutics, their clinical applications, and their delivery strategies.

Lipid Nanoparticle Delivery Systems to Enable mRNA-Based Therapeutics

The world raced to develop vaccines to protect against the rapid spread of SARS-CoV-2 infection upon the recognition of COVID-19 as a global pandemic. A broad spectrum of candidates was evaluated, with mRNA-based vaccines emerging as leaders due to how quickly they were available for emergency use while providing a high level of efficacy. As a modular technology, the mRNA-based vaccines benefitted from decades of advancements in both mRNA and delivery technology prior to the current global pandemic. The fundamental lessons of the utility of mRNA as a therapeutic were pioneered by Dr. Katalin Kariko and her colleagues, perhaps most notably in collaboration with Drew Weissman at University of Pennsylvania, and this foundational work paved the way for the development of the first ever mRNA-based therapeutic authorized for human use, COMIRNATY^®. In this Special Issue of Pharmaceutics, we will be honoring Dr. Kariko for her great contributions to the mRNA technology to treat diseases with unmet needs. In this review article, we will focus on the delivery platform, the lipid nanoparticle (LNP) carrier, which allowed the potential of mRNA therapeutics to be realized. Similar to the mRNA technology, the development of LNP systems has been ongoing for decades before culminating in the success of the first clinically approved siRNA-LNP product, ONPATTRO^®, a treatment for an otherwise fatal genetic disease called transthyretin amyloidosis. Lessons learned from the siRNA-LNP experience enabled the translation into the mRNA platform with the eventual authorization and approval of the mRNA-LNP vaccines against COVID-19. This marks the beginning of mRNA-LNP as a pharmaceutical option to treat genetic diseases.

Niosomes-based gene delivery systems for effective transfection of human mesenchymal stem cells

Gene transfer to mesenchymal stem cells (MSCs) has arisen as a powerful approach to increase the therapeutic potential of this effective cell population. Over recent years, niosomes have emerged as self-assembled carriers with promising performance for gene delivery. The aim of our work was to develop effective niosomes-based DNA delivery platforms for targeting MSCs. Niosomes based on 1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA; 0, 7 or 15%) as cationic lipid, cholesterol as helper lipid, and polysorbate 60 as non-ionic surfactant, were prepared using a reverse phase evaporation technique. Niosomes dispersions (filtered or not) and their corresponding nioplexes with a lacZ plasmid were characterized in terms of size, charge, protection, and complexation abilities. DOTMA concentration had a large influence on the physicochemical properties of resulting nioplexes. Transfection efficiency and cytotoxic profiles were assessed in two immortalized cell lines of MSCs. Niosomes formulated with 15% DOTMA provided the highest values of β-galactosidase activity, being similar to those achieved with Lipofectamine®, but showed less cytotoxicity. Filtration of niosomes dispersions before adding to the cells resulted in a loss of their biological activities. Storage of niosomes formulations (for 30 days at room temperature) caused minor modification of their physicochemical properties but also attenuated the transfection capability of the nioplexes. Differently, addition of the lysosomotropic agent sucrose into the culture medium during transfection or to the formulation itself improved the transfection performance of non-filtered niosomes. Indeed, steam heat-sterilized niosomes prepared in sucrose medium demonstrated transfection capability.

Advances in gene-based vaccine platforms to address the COVID-19 pandemic

The novel betacoronavirus, SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has spread across the globe at an unprecedented rate since its first emergence in Wuhan City, China in December 2019. Scientific communities around the world have been rigorously working to develop a potent vaccine to combat COVID-19 (coronavirus disease 2019), employing conventional and novel vaccine strategies. Gene-based vaccine platforms based on viral vectors, DNA, and RNA, have shown promising results encompassing both humoral and cell-mediated immune responses in previous studies, supporting their implementation for COVID-19 vaccine development. In fact, the U.S. Food and Drug Administration (FDA) recently authorized the emergency use of two RNA-based COVID-19 vaccines. We review current gene-based vaccine candidates proceeding through clinical trials, including their antigenic targets, delivery vehicles, and route of administration. Important features of previous gene-based vaccine developments against other infectious diseases are discussed in guiding the design and development of effective vaccines against COVID-19 and future derivatives.

Controlling Nanoparticle Formulation: A Low-Budget Prototype for the Automation of a Microfluidic Platform

Active pharmaceutical ingredients (API) with suboptimal pharmacokinetic properties may require formulation into nanoparticles. In addition to the quality of the excipients, production parameters are crucial for producing nanoparticles which reliably deliver APIs to their target. Microfluidic platforms promise increased control over the formulation process due to the decreased degrees of freedom at the micro- and nanoscale. Publications about these platforms usually provide only limited information about the soft- and hardware required to integrate the microfluidic chip seamlessly into an experimental set-up. We describe a modular, low-budget prototype for microfluidic mixing in detail. The prototype consists of four modules. The control module is a raspberry pi executing customizable python scripts to control the syringe pumps and the fraction collector. The feeding module consists of up to three commercially available, programable syringe pumps. The formulation module can be any macro- or microfluidic chip connectable to syringe pumps. The collection module is a custom-built fraction collector. We describe each feature of the working prototype and demonstrate its power with polyplexes formulated from siRNA and two different oligomers that are fed to the chip at two different stages during the assembly of the nanoparticles.

Flash Technology-Based Self-Assembly in Nanoformulation: From Fabrication to Biomedical Applications

Advances in nanoformulation have driven progress in biomedicine by producing nanoscale tools for biosensing, imaging, and drug delivery. Flash-based technology, the combination of rapid mixing technique with the self-assembly of macromolecules, is a new engine for the translational nanomedicine. Here, we review the state-of-the-art in flash-based self-assembly including theoretical and experimental principles, mixing device design, and applications. We highlight the fields of flash nanocomplexation (FNC) and flash nanoprecipitation (FNP), with an emphasis on biomedical applications of FNC, and discuss challenges and future directions for flash-based nanoformulation in biomedicine.

Efficiency of Chitosan/Hyaluronan-Based mRNA Delivery Systems In Vitro: Influence of Composition and Structure

Messenger RNA (mRNA)-containing nanoparticles were produced by electrostatic complexation with a library of pharmaceutical grade chitosans with different degrees of deacetylation and hyaluronic acids (HAs) (native vs. sulfated). Polymer length (Mn), HA degree of sulfation (DS), and amine to phosphate to carboxyl + sulfate (from HA) ratio (N:P:C) were controlled. In vitro transfections were performed in the presence/absence of trehalose and at different pH. Particle size and ζ-potential were correlated with transfection efficiency. Polymer length and charge densities (degree of deacetylation, degree of sulfation) of both HA and chitosan had a direct influence on transfection efficiency through modulation of avidity to mRNA. N:P:C ratio, trehalose, mixing concentration, and nucleic acid dose influenced transfection efficiency with optimized formulations reaching ∼60%-65% transfection efficiency relative to commercially available lipid control with no apparent toxicity for transfection at slightly acidic pH 6.5.

Lipid-Based DNA Therapeutics: Hallmarks of Non-Viral Gene Delivery

Gene therapy is a promising strategy for the treatment of monogenic disorders. Non-viral gene delivery systems including lipid-based DNA therapeutics offer the opportunity to deliver an encoding gene sequence specifically to the target tissue and thus enable the expression of therapeutic proteins in diseased cells. Currently, available gene delivery approaches based on DNA are inefficient and require improvements to achieve clinical utility. In this Review, we discuss state-of-the-art lipid-based DNA delivery systems that have been investigated in a preclinical setting. We emphasize factors influencing the delivery and subsequent gene expression in vitro, ex vivo, and in vivo. In addition, we cover aspects of nanoparticle engineering and optimization for DNA therapeutics. Finally, we highlight achievements of lipid-based DNA therapies in clinical trials.

Development of novel lipidic particles for siRNA delivery that are highly effective after 12 months storage

Liposomes are versatile and well-proven as a means to deliver nucleic acids into cells. Most of the formulation procedures used are labour intensive and result in unstable end products. We have previously reported on the development of a simple, yet efficient, hydration-of-freeze-dried-matrix (HFDM) method to entrap siRNA within lipid particles. Here we show that the particles are stable up to 12 months after storage at room temperature (RT), 4°C or -20°C. While RT storage results in changes in particle size and polydispersity, gene silencing of all particles was similar to freshly prepared particles following storage for 3, 6, 9 or 12 months at all temperatures. This is the first report of such long-term stability in siRNA-loaded liposomes.

Novel peptide-dendrimer/lipid/oligonucleotide ternary complexes for efficient cellular uptake and improved splice-switching activity

Despite the advances in gene therapy and in oligonucleotide (ON) chemistry, efficient cellular delivery remains an obstacle. Most current transfection reagents suffer from low efficacy or high cytotoxicity. In this report, we describe the synergism between lipid and dendrimer delivery vectors to enhance the transfection efficiency, while avoiding high toxicity. We screened a library of 20 peptide dendrimers representing three different generations and evaluated their capability to deliver a single-stranded splice-switching ON after formulating with lipids (DOTMA/DOPE). The transfection efficiency was analyzed in 5 reporter cell lines, in serum-free and serum conditions, and with 5 different formulation protocols. All formulations displayed low cytotoxicity to the majority of the tested cell lines. The complex sizes were < 200 nm; particle size distributions of effective mixtures were < 80 nm; and, the zeta potential was dependent on the formulation buffer used. The best dendrimer enhanced transfection in a HeLa reporter cell line by 30-fold compared to untreated cells under serum-free conditions. Interestingly, addition of sucrose to the formulation enabled - for the first time - peptide dendrimers/lipid complexes to efficiently deliver splice-switching ON in the presence of serum, reaching 40-fold increase in splice switching. Finally, in vivo studies highlighted the potential of these formulae to change the biodistribution pattern to be more towards the liver (90% of injected dose) compared to the kidneys (5% of injected dose) or to unformulated ON. This success encourages further development of peptide dendrimer complexes active in serum and future investigation of mechanisms behind the influence of additives on transfection efficacy.

Stratum corneum lipid liposome-encapsulated panomycocin: preparation, characterization, and the determination of antimycotic efficacy against Candida spp. isolated from patients with vulvovaginitis in an in vitro human vaginal epithelium tissue model

In this study, a liposomal lyophilized powder formulation of panomycocin was developed for therapeutic purposes against vulvovaginal candidiasis which affects 80% of women worldwide. Panomycocin is a potent antimycotic protein secreted by the yeast Wickerhamomyces anomalus NCYC 434. This study involved the preparation of panomycocin-loaded stratum corneum lipid liposomes (SCLLs), characterization of the SCLLs, and determination of antimycotic efficacy of the formulation against Candida albicans and Candida glabrata clinical vaginal isolates in a human vaginal epithelium tissue model. The encapsulation and loading efficiencies of SCLLs were 73% and 76.8%, respectively. In transmission electron microscopy images, the SCLLs appeared in the submicron size range. Dynamic light scattering analyses showed that the SCLLs had uniform size distribution. Zeta potential measurements revealed stable and positively charged SCLLs. In Fourier transform infrared spectroscopy analyses, no irreversible interactions between the encapsulated panomycocin and the SCLLs were detected. The SCLLs retained >98% of encapsulated panomycocin in aqueous solution up to 12 hours. The formulation was fungicidal at the same minimum fungicidal concentration values for non-formulated pure panomycocin when tested on an in vitro model of vaginal candidiasis. This is the first study in which SCLLs and a protein as an active ingredient have been utilized together in a formulation. The results obtained in this study led us to conduct further preclinical trials of this formulation for the development of an effective topical anti-candidal drug with improved safety.

Automated in-line mixing system for large scale production of chitosan-based polyplexes

Chitosan (CS)-based polyplexes are efficient non-viral gene delivery systems that are most commonly prepared by manual mixing. However, manual mixing is not only poorly controlled but also restricted to relatively small preparation volumes, limiting clinical applications. In order to overcome these drawbacks and to produce clinical quantities of CS-based polyplexes, a fully automated in-line mixing platform was developed for production of large batches of small-size and homogeneous CS-based polyplexes. Operational conditions to produce small-sized homogeneous polyplexes were identified. Increasing mixing concentrations of CS and nucleic acid was directly associated with an increase in size and polydispersity of both CS/pDNA and CS/siRNA polyplexes. We also found that although the speed of mixing has a negligible impact on the properties of CS/pDNA polyplexes, the size and polydispersity of CS/siRNA polyplexes are strongly influenced by the mixing speed: the higher the speed, the smaller the size and polydispersity. While in-line and manual CS/pDNA polyplexes had similar size and PDI, CS/siRNA polyplexes were smaller and more homogenous when prepared in-line in the non-laminar flow regime compared to manual method. Finally, we found that in-line mixed CS/siRNA polyplexes have equivalent or higher silencing efficiency of ApoB in HepG2 cells, compared to manually prepared polyplexes.

Enzyme-responsive destabilization of stabilized plasmid-lipid nanoparticles as an efficient gene delivery

Stabilized plasmid-lipid particles (SPLPs) have been developed to overcome the low stability issue of cationic liposomes, however, SPLPs that are too stable result in unsatisfactory transfection efficiency. In this article, we prepared enzyme-responsive SPLPs (eSPLPs) composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and mPEG-GLFG-K-(C16)2, a PEG lipid with an enzymatically-cleavable linker (glycine-phenylalanine-leucine-glycine, GFLG). eSPLPs were successfully prepared with plasmid DNA (pDNA) encapsulation efficiency of over 80%, using the detergent dialysis method. The PEG shell stabilized eSPLPs and maintained a hydrodynamic diameter of around 200nm. Although typical SPLPs were relatively intact in endosomal condition, the PEG shell of eSPLPs was cleaved following the degradation of the GFLG linker by cathepsin B in the endosome. Then, eSPLPs collapsed and induced endosomal disruption triggering the controlled release of the encapsulated pDNA into cytoplasm. Owing to the enzyme-responsive destabilization, eSPLPs showed a 10 to 100-fold higher transfection efficiency than control SPLPs, which was confirmed using luciferase assay. These results suggest that eSPLPs might be promising candidates for practical use as gene delivery systems, with both stability and high transfection efficiency for future in vivo applications.

A method for concentrating lipid peptide DNA and siRNA nanocomplexes that retains their structure and transfection efficiency

Nonviral gene and small interfering RNA (siRNA) delivery formulations are extensively used for biological and therapeutic research in cell culture experiments, but less so in in vivo and clinical research. Difficulties with formulating the nanoparticles for uniformity and stability at concentrations required for in vivo and clinical use are limiting their progression in these areas. Here, we report a simple but effective method of formulating monodisperse nanocomplexes from a ternary formulation of lipids, targeting peptides, and nucleic acids at a low starting concentration of 0.2 mg/mL of DNA, and we then increase their concentration up to 4.5 mg/mL by reverse dialysis against a concentrated polymer solution at room temperature. The nanocomplexes did not aggregate and they had maintained their biophysical properties, but, importantly, they also mediated DNA transfection and siRNA silencing in cultured cells. Moreover, concentrated anionic nanocomplexes administered by convection-enhanced delivery in the striatum showed efficient silencing of the β-secretase gene BACE1. This method of preparing nanocomplexes could probably be used to concentrate other nonviral formulations and may enable more widespread use of nanoparticles in vivo.

Current progress in gene delivery technology based on chemical methods and nano-carriers

Gene transfer methods are promising in the field of gene therapy. Current methods for gene transfer include three major groups: viral, physical and chemical methods. This review mainly summarizes development of several types of chemical methods for gene transfer in vitro and in vivo by means of nano-carriers like; calcium phosphates, lipids, and cationic polymers including chitosan, polyethylenimine, polyamidoamine dendrimers, and poly(lactide-co-glycolide). This review also briefly introduces applications of these chemical methods for gene delivery.

Long term stability of lyophilized plasmid DNA pDERMATT

In this short note we report on the shelf-life stability of pDERMATT (plasmid DNA encoding recombinant MART-1 and tetanus toxin fragment-c) 2mg lyophilized powder for reconstitution for intradermal administration, used in an in-house, investigator-initiated clinical phase I study. pDERMATT was stored at 25°C/60% relative humidity (6 months), 2-8°C (24 months), and -20°C (66 months) in the dark and analyzed at several timepoints during the conduct of the clinical study for appearance, identity, purity (plasmid topology), content and residual water content. pDERMATT appeared stable at all storage conditions for the periods tested which, although patient inclusion in the study was significantly delayed, ensured the clinical supply needs. This study shows that lyophilization is an useful tool to preserve the quality of the pDNA and can prevent the need for costly and time-consuming additional manufacture of drug product in case of study delays, not uncommon at the early stage of drug development. To our knowledge, this is the first study reporting shelf life stability of a pDNA formulation for more than 5 years.

DNA/Fusogenic Lipid Nanocarrier Assembly: Millisecond Structural Dynamics

Structural changes occurring on a millisecond time scale during uptake of DNA by cationic lipid nanocarriers are monitored by time-resolved small-angle X-ray scattering (SAXS) coupled to a rapid-mixing stopped-flow technique. Nanoparticles (NPs) of nanochannel organization are formed by PEGylation, hydration, and dispersion of a lipid film of the fusogenic lipid monoolein in a mixture with positively charged (DOMA) and PEGylated (DOPE-PEG2000) amphiphiles and are characterized by the inner cubic structure of very large nanochannels favorable for DNA upload. Ultrafast structural dynamics of complexation and assembly of these cubosome particles with neurotrophic plasmid DNA (pDNA) is revealed thanks to the high brightness of the employed synchrotron X-ray beam. The rate constant of the pDNA/lipid NP complexation is estimated from dynamic roentgenograms recorded at 4 ms time resolution. pDNA upload into the vastly hydrated channels of the cubosome carriers leads to a fast nanoparticle-nanoparticle structural transition and lipoplex formation involving tightly packed pDNA.

Recent developments and perspectives on gene therapy using synthetic vectors

Nonviral vector technology is attracting increasing importance in the biomedical community owing to unique advantages and prospects for the treatment of severe diseases by gene therapy. In this review, synthetic vectors that allow the controlled design of efficient and biocompatible carriers are highlighted. The current benefits, potentials, problems and unmet needs of synthetic gene delivery systems, as well as the strategies to overcome the obstacles are also discussed. Common design principles and structure-activity trends have been established that are important for stable and targeted transport to regions of interest in the body, efficient uptake into cells as well as controlled release of drugs inside the cells, for example, in specialized compartments. The status quo of the use of these systems in preclinical and clinical trials is also considered.

Optimized preparation of pDNA/poly(ethylene imine) polyplexes using a microfluidic system

Poly(ethylene imine) (PEI) is an established non-viral vector system for the delivery of various nucleic acids in gene therapy applications. Polyelectrolyte complexes between both compounds, so called polyplexes, are formed by electrostatic interactions of oppositely charged macromolecules and are thought to facilitate uptake into cells. Such complexes form spontaneously and on lab scale they are usually prepared by mixing solutions through pipetting. Hence, an optimized preparation procedure allowing the scale-up of well-defined polyplexes would be of general interest. We developed a new method for microfluidic polyplex preparation on a chip. The mixing behaviour within the microfluidic channels was evaluated. Polyplexes with PEI and plasmid DNA were prepared using this method, in comparison to the standard pipetting procedure. Sizes and polydispersity indices of these complexes were examined. The influence of various parameters on the polyplex characteristics and the suitability of this production procedure for other PEI-based complexes were also evaluated. It was shown that polyplexes could easily be prepared by microfluidics. The ratio of PEI to DNA was most important for the formation of small polyplexes, whereas other parameters had minor influence. The size of polyplexes prepared with this new method was observed to be relatively constant between 140 nm and 160 nm over a wide range of complex concentrations. In comparison, the size of polyplexes prepared by pipetting (approximately 90 nm to 160 nm) varied considerably. The versatility of this system was demonstrated with different (targeted) PEI-based vectors for the formation of complexes with pDNA and siRNA. In conclusion, polyplex preparation using microfluidics could be a promising alternative to the standard pipetting method due to its suitability for preparation of well-defined complexes with different compositions over a wide range of concentrations.

In vitro transfection of plasmid DNA by cationized gelatin prepared from different amine compounds

The objective of this paper is to compare the in vitro transfection efficiency of a luciferase plasmid DNA using cationized gelatin prepared from different amine compounds. The compounds used here were ethylenediamine, putrescine, spermidine and spermine, chemically introduced to the carboxyl group of gelatin for the cationization. Complexation of the cationized gelatin with the plasmid DNA was performed by simply mixing the two materials at various N+/P- mixing ratios (the molar number ratio of amino groups of gelatin to the phosphate groups of DNA) in aqueous solution. Gel retardation studies revealed that the formation of cationized-gelatin-plasmid DNA complexes depended on the N+/P- mixing ratio. The stronger interaction of plasmid DNA with the cationized gelatin of spermine compared to the other cationized gelatins was observed by an ethidium bromide intercalation assay and Scatchard binding analysis. When the transfection efficiency of plasmid DNA complexed with the various cationized gelatins at different N+/P- mixing ratios was evaluated for mouse L929 fibroblasts, the highest transfection efficiency was observed for the complex prepared from the cationized gelatin of spermine at a N+/P- mixing ratio of 2. The present study indicates that there is an optimal N+/P- mixing ratio and a type of amine compound or cationization extent of cationized gelatin to enhance the transfection efficiency of plasmid DNA.

Therapeutic plasmid DNA versus siRNA delivery: common and different tasks for synthetic carriers

Gene therapy offers great opportunities for the treatment of severe diseases including cancer. In recent years the design of synthetic carriers for nucleic acid delivery has become a research field of increasing interest. Studies on the delivery of plasmid DNA (pDNA) have brought up a variety of gene delivery vehicles. The more recently emerged gene silencing strategy by the intracellular delivery of small interfering RNA (siRNA) takes benefit from existing expertise in pDNA transfer. Despite common properties however, delivery of siRNA also faces distinct challenges due to apparent differences in size, stability of the formed nucleic acid complexes, the location and mechanism of action. This review emphasizes the common aspects and main differences between pDNA and siRNA delivery, taking into consideration a wide spectrum of polymer-based, lipidic and peptide carriers. Challenges and opportunities which result from these differences as well as the recent progress made in the optimization of carrier design are presented.

Development of a lyophilized plasmid/LPEI polyplex formulation with long-term stability--A step closer from promising technology to application

Cationic polymer/DNA complexes are limited by their instability in aqueous suspensions and usually have to be freshly prepared prior to administration. Thus, the development of isotonic lyophilized polyplex formulations with long-term stability is a desirable goal. Polyplexes based on 22kDa linear polyethylenimine were prepared using a micro-mixer method. Freeze-thawing and lyophilization were performed on a pilot scale freeze-drier. Several excipients (trehalose, sucrose, lactosucrose, dextran, hydroxypropylbetadex or povidone and combinations thereof) at varying concentrations were evaluated for their stabilizing potential against freezing and dehydration induced stresses. For stability testing the lyophilized samples were stored for 6 weeks at 2-8°C, 20°C and 40°C, respectively. Polyplex samples were characterized for particle size, zeta potential, their in vitro transfection efficiency and metabolic activity in Neuro2A cells. In addition, liquid samples were investigated for turbidity and number of sub-visible particles and solid samples were analyzed for residual moisture content, glass transition temperature and sample morphology. L-histidine buffer pH 6.0 was selected as effective buffer. In isotonic formulations with 14% lactosucrose, 10% hydroxypropylbetadex/6.5% sucrose or 10% povidone/6.3% sucrose, particle size was <170nm for all formulations and did not change after storage for 6weeks at 40°C. Polyplexes formulated with lactosucrose or hydroxypropylbetadex/sucrose showed high transfection efficiencies and cellular metabolic activities. Absence of large aggregates was indicated by turbidity and subvisible particle number measurements. The current standard limits for particulate contamination for small volume parenterals were met for all formulations. All samples were amorphous with low residual moisture levels (<1.3%) and high glass transition temperatures (>90°C).

The establishment of an up-scaled micro-mixer method allows the standardized and reproducible preparation of well-defined plasmid/LPEI polyplexes

Polyplexes based on linear polyethylenimine (LPEI) and plasmid DNA are known as efficient non-viral gene delivery systems. However, the requirement for freshly prepared complexes prior to administration due to their instability in aqueous suspension poses the risk of batch-to-batch variations. Therefore, the aim of the study was the establishment of a reproducible and up-scalable method for the preparation of well-defined polyplexes. Polyplexes consisting of pCMVLuc plasmid and 22 kDa linear polyethylenimine (LPEI) were prepared by classical pipetting or with a micro-mixer method using different mixing speeds and plasmid DNA concentrations (20-400 μg/mL). The z-average diameter of the polyplexes was measured by dynamic light scattering. Metabolic activity and transfection efficiency was evaluated on murine neuroblastoma cells after transfection with polyplexes. When varying mixing speeds of the micro-mixer, polyplex size (59-197 nm) and polydispersity index (0.05-0.19) could be directly controlled. The z-average diameter (65-170 nm) and polydispersity index (0.05-0.22) of the polyplexes increased with increasing plasmid DNA concentration (20-400 μg/mL). The established up-scaled micro-mixer method allows the standardized and reproducible preparation of well-defined, transfection-competent plasmid/LPEI polyplexes with high reproducibility.

Efficient, specific and targeted delivery of genes to the lung

Many inherited and acquired pulmonary disorders without satisfactory therapies may be amenable to gene therapy. Despite numerous advances, efficient delivery and expression of the therapeutic transgene at physiological levels for phenotypic correction of disease has proved elusive. This article focuses on various strategies aimed at achieving targeted delivery to the lungs. Both physical methods and biological targeting have been successfully applied in various gene delivery systems. Targeting of different cell types has been achieved by pseudotyping of viral vectors with capsids from different serotypes and modification of nonviral vectors with targeting ligands. Both classes of vectors are discussed with respect to their gene delivery and expression efficiencies, longevity of expression and immunogenicity. Moreover, gene therapy clinical trials for different lung diseases are discussed.

Cationic lipids: molecular structure/ transfection activity relationships and interactions with biomembranes

Abstract Synthetic cationic lipids, which form complexes (lipoplexes) with polyanionic DNA, are presently the most widely used constituents of nonviral gene carriers. A large number of cationic amphiphiles have been synthesized and tested in transfection studies. However, due to the complexity of the transfection pathway, no general schemes have emerged for correlating the cationic lipid chemistry with their transfection efficacy and the approaches for optimizing their molecular structures are still largely empirical. Here we summarize data on the relationships between transfection activity and cationic lipid molecular structure and demonstrate that the transfection activity depends in a systematic way on the lipid hydrocarbon chain structure. A number of examples, including a large series of cationic phosphatidylcholine derivatives, show that optimum transfection is displayed by lipids with chain length of approximately 14 carbon atoms and that the transfection efficiency strongly increases with increase of chain unsaturation, specifically upon replacement of saturated with monounsaturated chains.

DNA release dynamics from bioreducible poly(amido amine) polyplexes

The DNA release dynamics of bioreducible poly(amido amine) polyplexes were studied in real time by atomic force microscopy (AFM). DNA release is triggered by a depolymerization of high-molecular-weight polycations into low-molecular-weight oligocations that occurs by means of the thiol and disulfide exchange reaction mechanism. AFM images were captured in a simulated physiological reducing environment that used dithiothreitol. Distinctive stages of disassembly are common among various polyplexes that have different disulfide content, molecular weight, and polymer architecture, while the DNA release rate depends upon the disulfide content. In the first stage, polyplexes evolve from metastable structures into the more stable toroid structure upon the depolymerization. In the second stage, toroids either aggregate or fuse into larger toroids. In the last stage, DNA wormlike chains and loops are held by a central compact core. The results confirm the prospect of bioreducible poly(amido amine)s as controlled DNA delivery vectors. The study offers new physical insights into the DNA release pathway including intermediate structures that have a high degree of structural heterogeneity and disassembly induced particle growth. The study identifies disassembly induced colloidal and morphological instability as an important issue to be addressed.

Reverse micelle-mediated synthesis of calcium phosphate nanocarriers for controlled release of bovine serum albumin

Calcium phosphate (CaP) nanoparticles with a calcium to phosphorus (Ca:P) molar ratio of 1.5:1 were synthesized using reverse microemulsion. Ca(NO(3))(2).4H(2)O and H(3)PO(4) were used as the aqueous phase, cyclohexane as the organic phase and poly(oxyethylene)(12) nonylphenol ether (NP-12) as the surfactant. Depending on the calcination temperature between 600 and 800 degrees C, CaP nanoparticle showed different phases of calcium-deficient hydroxyapatite (CDHA) and beta-tricalcium phosphate (beta-TCP), particle size between 48 and 69 nm, and a BET specific average surface area between 73 and 57 m(2)g(-1). Bovine serum albumin (BSA) was used as a model protein to study loading and release behavior. The adsorptive property of BSA was investigated by the change in BET surface area of these nanoparticles and the pH of the suspension. At pH 7.5, the maximum amount of BSA was adsorbed onto CaP nanoparticle. The release kinetics of BSA showed a gradual time-dependent increase in pH 4.0 and 6.0 buffer solutions. However, the amount of protein released was significantly smaller at pH 7.2. The BSA release rate also varied depending on the presence of different phases of CaPs in the system, beta-TCP or CDHA. These results suggest that the BSA protein release rate can be controlled by changing the particle size, surface area and phase composition of the CaP nanocarriers.

Nonviral gene vector formation in monodispersed picolitre incubator for consistent gene delivery

A novel picolitre incubator based microfluidic system for consistent nonviral gene carrier formulation is presented. A cationic lipid-based carrier is the most attractive nonviral solution for delivering plasmid DNA, shRNA, or drugs for pharmaceutical research and RNAi applications. The size of the cationic lipid and DNA complex (CL-DNA), or the lipoplex, is one of the important variations for consistency of gene transfection. CL-DNA size, in turn, may be controlled by factors such as the cationic lipid and DNA mixing order, mixing rate, and mixture incubation time. The Picolitre Microfluidic Reactor and Incubator (PMRI) system described here is able to control these parameters in order to create homogeneous CL-DNA. Compared with conventional CL-DNA preparation techniques involving hand-shaking or vortexing, the PMRI system demonstrates a greater ability to constantly and uniformly mix cationic lipids and DNA simultaneously. After mixing in the picolitre droplet reactors, the cationic lipid and DNA is incubated within the picolitre incubator to form CL-DNA. The PMRI generates a narrower size distribution band, while also turning the sample loading, mixing and incubation steps into an integrated process enabling the consistent formation of CL-DNA. The coefficient of variation (CV) of transfection efficiency is 0.05 and 0.30 for PMRI-based and conventional methods, respectively. In addition, this paper demonstrates that the gene transfection efficiency of lipoplex created in the PMRI is more reproducible.

Topical delivery of interleukin-13 antisense oligonucleotides with cationic elastic liposome for the treatment of atopic dermatitis

BACKGROUND

Interleukin (IL)-13, overproduced in the skin of atopic dermatitis (AD), has been shown to play an essential role in the pathogenesis of the disease. Thus, inhibition of IL-13 production should provide a key step to alleviate disease conditions of the atopic skin. In the present study, IL-13 antisense oligonucleotide (ASO) was designed and formulated with cationic elastic liposome (cEL) to improve transdermal delivery.

METHODS

ASOs were generated against murine IL-13 mRNA (+4 to + 23) and complexed with cEL. Physicochemical properties of IL-13 ASO/cEL complex were examined by DNA retardation and DNase I protection assay. An in vitro inhibition study was performed in T-helper 2 (Th2) cells and cytotoxicity was tested by the XTT assay. The in vivo effect of IL-13 ASO/cEL complex was tested in a murine model of AD.

RESULTS

In vitro, the IL-13 ASO/cEL complex showed dose- and ratio-dependent inhibition of IL-13 secretion in Th2 cells. At the IL-13 ASO/cEL ratio of 6, maximum inhibition of IL-13 secretion was observed. When applied to the ovalbumin-sensitized murine model of AD, topically administered IL-13 ASO/cEL complex dramatically suppressed IL-13 production (by up to 70% of the control) in the affected skin region. In addition, the levels of IL-4 and IL-5 were also significantly reduced. Moreover, IL-13 ASO/cEL-treated AD mice showed reduced infiltration of inflammatory cells into the epidermal and dermal areas, with concomitant reduction of skin thickness.

CONCLUSIONS

These data suggests that IL-13 ASO/cEL complex can provide a potential therapeutic tool for the treatment of AD and also be applied to other immune diseases associated with the production of Il-13.

DNA release dynamics from reducible polyplexes by atomic force microscopy

Controlled intracellular disassembly of polyelectrolyte complexes of polycations and DNA (polyplexes) is a crucial step for the success of nonviral gene delivery. Motivated by our previous observation of different gene delivery performances among multiblock reducible copolypeptide vectors ( Manickam, D. S. ; Oupicky, D. Bioconjugate Chem. 2006, 17, 1395- 1403 ), atomic force microscopy is used to visualize plasmid DNA in various decondensed states from reducible polypeptide polyplexes under simulated physiological reducing conditions. DNA decondensation is triggered by reductive degradation of disulfide-containing cationic polypeptides. Striking differences in DNA release dynamics between polyplexes based on polypeptides of histidine-rich peptide (HRP, CKHHHKHHHKC) and nuclear localization signal (NLS, CGAGPKKKRKVC) peptide are presented. The HRP and NLS polyplexes are similar to each other in their initial morphology with a majority of them containing only one DNA plasmid. Upon reductive degradation by dithiothreitol, DNA is released from NLS abruptly regardless of the initial polyplex morphology, while DNA release from HRP polyplexes displays a gradual decondensation that is dependent on the size of polyplexes. The release rate is higher for larger HRP polyplexes. The smaller HRP polyplexes become unstable when they are in contact with expanding chains nearby. The results reveal potentially rich DNA release dynamics that can be controlled by subtle variation in multivalent counterion binding to DNA as well as the cellular matrix.

Preparation and gene delivery of alkaline amino acids-based cationic liposomes

Cationic lipids 1, 2, and 3, based on hydrophobic cholesterol linked to L-lysine, L-histidine or L-arginine, respectively, were designed and tested as gene delivery vectors. Physicochemical and biological properties of all liposomes and lipoplexes were evaluated, including lipid-DNA interactions, size, morphology, zeta potential, acid-base buffering capability, protection of DNA from DNase I digestion, and cytotoxity. The efficiency of luciferase gene transfection of lipoplexes 1-3 was compared with that of commercial dioleoyl-trimethylammonium propane (DOTAP) and polyethyleneimine (PEI) in 293T cells and HepG2 cells with or without poly(ethylene glycol) PEG stabilizer. The complexation and protection of DNA of liposome 3 was the strongest among the three liposomes. The efficiency of gene transfection of liposomes 1-3 was two-to threefold higher than that of PEI and/or DOTAP in 293T cells. Liposomes 1 and 3 in PEG as stabilizer showed sixfold higher transfection efficiency than that of PEI and/or DOTAP, whereas liposome 2 showed very low transfection efficiency. In HepG2 cells, the transfection efficiency of all the cationic liposomes was much lower than that of DOTAP. In conclusion, lipids 1-3 were efficient and non-toxic gene vectors; the headgroup of cationic lipids and the stabilizer of liposome formulation had an important influence on gene transfection.

Structure-function relationship research of glycerol backbone-based cationic lipids for gene delivery

Transfection activities of two series of synthetic glycerol backbone-based cationic lipids were studied as gene delivery carriers. The variable length of hydrocarbon chains, diverse quaternary ammonium heads, different linkage, as well as alternative anion combined with them allowed to find how these factors affect cationic lipids on their gene delivery performance. The structure-function relationship of the synthetic glycerol backbone-based cationic lipids was discussed, and the transfection efficiency of some of the cationic liposomes was superior or parallel to that of two commercial transfection agents.