Topical non-invasive gene delivery using gemini nanoparticles in interferon-γ-deficient mice

Pulmonary delivery of nano-particles for lung cancer diagnosis and therapy: Recent advances and future prospects

Although our understanding of lung cancer has significantly improved in the past decade, it is still a disease with a high incidence and mortality rate. The key reason is that the efficacy of the therapeutic drugs is limited, mainly due to insufficient doses of drugs delivered to the lungs. To achieve precise lung cancer diagnosis and treatment, nano-particles (NPs) pulmonary delivery techniques have attracted much attention and facilitate the exploration of the potential of those in inhalable NPs targeting tumor lesions. Since the therapeutic research focusing on pulmonary delivery NPs has rapidly developed and evolved substantially, this review will mainly discuss the current developments of pulmonary delivery NPs for precision lung cancer diagnosis and therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Targeted Delivery Platforms for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative condition of the central nervous system (CNS) that presents with varying levels of disability in patients, displaying the significance of timely and effective management of this complication. Though several treatments have been developed to protect nerves, comprehensive improvement of MS is still considered an essential bottleneck. Therefore, the development of innovative treatment methods for MS is one of the core research areas. In this regard, nanoscale platforms can offer practical and ideal approaches to the diagnosis and treatment of various diseases, especially immunological disorders such as MS, to improve the effectiveness of conventional therapies. It should be noted that there is significant progress in the development of neuroprotective strategies through the implementation of various nanoparticles, monoclonal antibodies, peptides, and aptamers. In this study, we summarize different particle systems as well as targeted therapies, such as antibodies, peptides, nucleic acids, and engineered cells for the treatment of MS, and discuss their potential in the treatment of MS in the preclinical and clinical stages. Future advances in targeted delivery of medical supplies may offer new strategies for complete recovery as well as practical treatment of progressive forms of MS.

Cationic gemini surfactant properties, its potential as a promising bioapplication candidate, and strategies for improving its biocompatibility: A review

Gemini surfactants consist of two cationic monomers of a surfactant linked together with a spacer. The specific structure of a cationic gemini surfactant is the reason for both its high surface activity and its ability to decrease the surface tension of water. The high surface activity and unique structure of gemini surfactants result in outstanding properties, including antibacterial and antifungal activity, anticorrosion properties, unique aggregation behaviour, the ability to form various structures reversibly in response to environmental conditions, and interactions with biomacromolecules such as DNA and proteins. These properties can be tailored by selecting the optimal structure of a gemini surfactant in terms of the nature and length of its alkyl substituents, spacer, and head group. Additionally, regarding their properties, comparison with their monomeric counterparts demonstrates that gemini surfactants have higher performance efficacy at lower concentrations. Hence, less material is needed, and the toxicity is lower. However, there are some limitations regarding their biocompatibility that have led researchers to develop amino acid-based and sugar-based gemini surfactants. Owing to their remarkable properties, cationic gemini surfactants are promising candidates for bioapplications such as drug delivery systems, gene carriers, and biomaterial surface modification.

The structure - Activity correlation in the family of dicationic imidazolium surfactants: Antimicrobial properties and cytotoxic effect

BACKGROUND

The development of new effective microbicide surfactants and the search for the structure-biological activity relationship is an important and promising problem. Surfactants containing imidazolium fragment attract attention of researchers in the field of chemotherapy, because these compounds often exhibit high antimicrobial activity. The aim of this work is to identify the newly synthesized surfactants from the viewpoint of their potential usefulness in pharmacology and medicine. For this purpose, a detailed study of antimicrobial, hemolytic and cytotoxic activity of dicationic alkylimidazolium surfactants of the m-s-m (Im) series with a variable length of a hydrocarbon tail (m = 10, 12) and a spacer fragment (s = 2, 3, 4) was carried out.

METHODS

Aggregation of surfactants in solutions was estimated by tensiometry and conductivity. Antimicrobial activity was determined by the serial dilution technique. Cytotoxic effects of the test compounds on human cancer and normal cells were estimated by means of the multifunctional Cytell Cell Imaging system. Cell Apoptosis Analysis was made by flow cytometry.

RESULTS

The test compounds show high antimicrobial activity against a wide range of test microorganisms and do not possess high hemolytic activity. Importantly, some of them display a bactericidal activity comparable to ciprofloxacin fluoroquinolone antibiotic against Gram-positive bacteria, including methicillin-resistant strains of S. aureus (MRSA). The cytotoxicity of the compounds against normal and tumor human cell lines has been tested as well, with cytotoxic effect and selectivity strongly controlled by structural factor and kind of cell line. Superior results were revealed for compound 10-4-10 (Im) in the case of HuTu 80 cell line (duodenal adenocarcinoma), for which IC₅₀ value at the level of doxorubicin and a markedly higher selectivity index (SI 7.5) were demonstrated. Flow cytometry assay shows apoptosis-inducing effect of this compound on HuTu 80 cells, through significant changes in the potential of mitochondrial membrane.

MAJOR CONCLUSIONS

Antibacterial properties are shown to be controlled by alkyl chain length, with the highest activity demonstrated by surfactants with decyl tail, with the length of the spacer fragment showing practically no effect. The results indicate that the mechanism of cytotoxic effect of the compounds can be associated with the induction of apoptosis via the mitochondrial pathway.

GENERAL SIGNIFICANCE

Selectivity against pathogenic microorganisms and low toxicity against eukaryotic cells allow considering dicationic imidazolium surfactants as new effective antimicrobial agents. At the same time, high selectivity against some cancer cell lines indicates the prospect of their using as components of new anticancer drugs.

Peptide-Modified Gemini Surfactants: Preparation and Characterization for Gene Delivery

Diquaternary ammonium-based gemini surfactants have been investigated widely as nonviral gene delivery systems. These unique cationic lipids have versatility in their chemical structure, show relatively low toxicity, are able to compact genetic material (pDNA, RNA) into nano-sized lipoplexes, and can be easily produced. In addition, the gemini surfactants show significant improvement in the transfection activity and biocompatibility compared to other cationic lipids used as nonviral gene delivery agents. The successful applications of gemini surfactant-based lipoplexes as topical gene delivery systems in animal models indicate their potential as noninvasive carriers for genetic immunization, theranostic agents, and in other gene therapy treatments. Detailed physicochemical characterization of gemini surfactant lipoplexes is a key factor in terms of formulation optimization and elucidation of the cellular uptake and stability of the lipoplexes system. In this chapter, we describe in detail different formulation methods to prepare gemini surfactant lipoplexes and comprehensive physicochemical characterization. In addition, we illustrate general protocols for in vitro evaluations.

Cellular Uptake and Distribution of Gemini Surfactant Nanoparticles Used as Gene Delivery Agents

Gemini surfactants are promising molecules utilized as non-viral gene delivery vectors. However, little is known about their cellular uptake and distribution after they release their therapeutic cargo. Therefore, we quantitatively evaluated the cellular uptake and distribution of three gemini surfactants: unsubstituted (16-3-16), with pyridinium head groups (16(Py)-S-2-S-16(Py)) and substituted with a glycyl-lysine di-peptide (16-7N(GK)-16). We also assessed the relationship between cellular uptake and distribution of each gemini surfactant and its overall efficiency and toxicity. Epidermal keratinocytes PAM 212 were treated with gemini surfactant nanoparticles formulated with plasmid DNA and harvested at various time points to collect the enriched nuclear, mitochondrial, plasma membrane, and cytosolic fractions. Gemini surfactants were then extracted from each subcellular fraction and quantified using a validated flow injection analysis-tandem mass spectrometry (FIA-MS/MS) method. Mass spectrometry is superior to the use of fluorescent tags that alter the physicochemical properties and pharmacokinetics of the nanoparticles and can be cleaved from the gemini surfactant molecules within biological systems. Overall, a significantly higher cellular uptake was observed for 16-7N(GK)-16 (17.0%) compared with 16-3-6 (3.6%) and 16(Py)-S-2-S-16(Py) (1.4%), which explained the relatively higher transfection efficiency of 16-7N(GK)-16. Gemini surfactants 16-3-16 and 16(Py)-S-2-S-16(Py) displayed similar subcellular distribution patterns, with major accumulation in the nucleus, followed by the mitochondrion, cytosol, and plasma membrane. In contrast, 16-7N(GK)-16 was relatively evenly distributed across all four subcellular fractions. However, accumulation within the nucleus after 5 h of treatment was the highest for 16(Py)-S-2-S-16(Py) (50.3%), followed by 16-3-16 (41.8%) and then 16-7N(GK)-16 (33.4%), possibly leading to its relatively higher toxicity. Graphical Abstract.

Non-Lamellar Lyotropic Liquid Crystalline Lipid Nanoparticles for the Next Generation of Nanomedicine

Nonlamellar lyotropic liquid crystalline (LLC) lipid nanomaterials have emerged as a promising class of advanced materials for the next generation of nanomedicine, comprising mainly of amphiphilic lipids and functional additives self-assembling into two- and three-dimensional, inverse hexagonal, and cubic nanostructures. In particular, the lyotropic liquid crystalline lipid nanoparticles (LCNPs) have received great interest as nanocarriers for a variety of hydrophobic and hydrophilic small molecule drugs, peptides, proteins, siRNAs, DNAs, and imaging agents. Within this space, there has been a tremendous amount of effort over the last two decades elucidating the self-assembly behavior and structure-function relationship of natural and synthetic lipid-based drug delivery vehicles in vitro, yet successful clinical translation remains sparse due to the lack of understanding of these materials in biological bodies. This review provides an overview of (1) the benefits and advantages of using LCNPs as drug delivery nanocarriers, (2) design principles for making LCNPs with desirable functionalities for drug delivery applications, (3) current understanding of the LLC material-biology interface illustrated by more than 50 in vivo, preclinical studies, and (4) current patenting and translation activities in a pharmaceutical context. Together with our perspectives and expert opinions, we anticipate that this review will guide future studies in developing LCNP-based drug delivery nanocarriers with the objective of translating them into a key player among nanoparticle platforms comprising the next generation of nanomedicine for disease therapy and diagnosis.

Tuning optimum transfection of gemini surfactant-phospholipid-DNA nanoparticles by validated theoretical modeling

Gemini nanoparticles (NPs) are a family of non-viral gene delivery systems with potential for applications in non-invasive gene therapy. Translation of these non-viral gene delivery systems requires improvement of transfection efficiency (TE) through fine-tuning of their physicochemical properties such as electric charge and exact ratios of their components. Since high-throughput experimental screening of minute differences in NP compositions is not routinely feasible, we have developed a coarse-grained model to quantitatively study the energetics of the formation of gene delivery complexes with cationic gemini surfactants (G) (m-s-m type) and helper lipids (H) (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and DOPE/1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC)), in order to use it as a tool to predict effective compositions. The model is based on the polymorphic structural conformational flip of NPs and incorporates the electrostatic, entropic and elastic energies, to predict the formation energy and stability of different polymorphic structures as a function of the electric charge of cationic surfactants and concentration of constituent helper lipids. Our results show that these two factors are intertwined in determining the behavior of gene delivery vectors. Specifically, we show that increasing H/G lowers free energy per DNA base pair and increases the stability of the complex. At pH 7, low H/G and charge ratio (ρ±), where the lamellar structure is favored, the formation free energy per DNA base pair is between 0 and -14kBT. At higher values of H/G (2-3) and ρ±, where HII and cubic structures are formed, the formation free energy drops down to values ≈-50kBT, indicating the stable existence of these polymorphic structures in the NPs. At pH 5, the structural transformation of NPs in the endosomes to the lamellar/HII structure with free energy values of about -40kBT is beneficial for endosomal escape, and correlates with increased transfection efficiency. The theoretical model is supported by transfection data in A7 astrocytes with a panel of 16-3-16 gemini NPs, which validates the mathematical model and supports the hypothesis that the NP polymorphic phase transition increases transfection efficiency.

Gemini Amphiphile-Based Lipoplexes for Efficient Gene Delivery: Synthesis, Formulation Development, Characterization, Gene Transfection, and Biodistribution Studies

Some quaternary gemini amphiphiles (GAs) were synthesized as nonviral gene delivery carriers. The critical miceller concentration values of these amphiphiles are indicative of their superior surface-active properties. All of the synthesized GAs, alone or along with lipids like cholesterol and/or dioleoylphosphatidyl ethanolamine (DOPE), were formulated as liposomes. Formulations of GAs with DOPE showed average particle diameters of 326-400 nm with positive ζ-potential (30.1-46.4 mV). The lipoplexes of theses formulations showed complete pDNA retention at the base at a N/P ratio higher than 1.0 in gel retardation study. The GAs were effective in condensing pDNA into a ψ-phase, as indicated by circular dichroism study, and provided complete protection of the pDNA against the enzyme DNase at a N/P ratio more than 1. In vitro cell line studies showed that GA liposomal formulations caused β-gal expression and offered a higher transfection efficiency than that of liposomes prepared with the help of N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (DOTAP)/DOPE and dicyclocarbodiimide (DCC)/DOPE but comparable to those of Lipofectamine 2000 in A549 and HeLa cell lines. Modulation of head group polarity significantly affected the transfection efficacy of GAs. The cell viabilities of almost all of the formulations were comparable to those of the standards (DCC/DOPE and DOTAP/DOPE liposomes). Incorporation of cholesterol [GA/DOPE/cholesterol in the ratio of 1:1:1] further improved the serum compatibility of the formulations and improved the transfection efficacy when evaluated in A549 and HeLa cell lines. Fluorescence-assisted cell sorting studies showed comparable number of transfected cells to Lipofectamine 2000 in the HeLa cell line. Intracellular trafficking studies using confocal microscopy indicated transfection of the HeLa cells with the reporter gene within 30 min of lipoplex treatment. γ-Scintigraphy using ^99mTc-labeled lipoplexes showed higher concentrations of the lipoplexes in vital tissues like liver, spleen, lungs, and kidneys.

Molecular Engineering as an Approach To Modulate Gene Delivery Efficiency of Peptide-Modified Gemini Surfactants

The unique molecular structure confers the diquaternary ammonium gemini surfactants with enhanced nucleic acid complexation ability, bottom-up design flexibility, and relatively low cytotoxicity. To capitalize on their potential as gene delivery vectors, novel structural modifications should be explored. In this work, 22 novel peptide-modified gemini surfactants with various alkyl tails and peptide spacer modifications were evaluated. This work represents the first report of dendrimer-like gemini surfactants and first evaluation of the impact of incorporating a hydrocarbon linker into the peptide chain. Our aim was to establish a structure activity relationship of the peptide-modified gemini surfactants and to identify the fundamental architectural requirements needed for the ultimate gene delivery systems. In vitro assessment revealed that the highest transfection efficiency and lowest cytotoxicity were associated with the glycyl-lysine modified gemini surfactants having the hexadecyl tail, 16-7N(G-K)-16. In fact, it showed an 8-fold increase in secreted protein with 20% increase in cell viability relative to the first-generation unsubstituted gemini surfactants. Further increase in the size of the attached peptides resulted in a decrease in the transfection efficiency and cell viability. Whereas the incorporation of a hydrocarbon linker into the peptide chain decreased the transfection efficiency of compounds with dipeptides, it increased the transfection efficiency of compounds with larger peptide chains. Such an increase was more prominent with the incorporation of a longer hydrocarbon linker. We conclude that a balance between the hydrophilic and hydrophobic characteristics of the compound is necessary since it results in physicochemical parameters conducive to the gene delivery process.

Ionic liquid mediated micelle to vesicle transition of a cationic gemini surfactant: a spectroscopic investigation

In this contribution, we have examined a composition dependent self aggregated structural modification of a catanionic mixture of the surface active ionic liquid (IL) 1-butyl-3-methylimidazolium octyl sulphate and a cationic gemini surfactant (14-5-14) in aqueous medium. We have observed that the hydrodynamic diameter of the aggregates increases with increasing IL concentration and microscopic evidence (HRTEM, FESEM, and LCSM) shows the formation of vesicle like aggregates (Dh ≈ 200 nm) at XIL = 0.5. The steady state fluorescence anisotropy of the membrane binding probe DPH shows a micelle to vesicle transition at this composition. The viscosity of the solution shows a peak at XIL = 0.3, indicating the formation of a worm like micelle as an intermediate of the micelle to vesicle transition. The rotational dynamics shows a stiffer surfactant packing in the vesicles compared to the micelles, whereas, the solvation dynamics measurements indicate a higher abundance of bound type water in the vascular medium compared to that for the micelle. The formed vesicles also show stability towards temperature and biomolecules, which can be used for respective applications.

Tandem mass spectrometric analysis of novel peptide-modified gemini surfactants used as gene delivery vectors

Diquaternary ammonium gemini surfactants have emerged as effective gene delivery vectors. A novel series of 11 peptide-modified compounds was synthesized, showing promising results in delivering genetic materials. The purpose of this work is to elucidate the tandem mass spectrometric (MS/MS) dissociation behavior of these novel molecules establishing a generalized MS/MS fingerprint. Exact mass measurements were achieved using a hybrid quadrupole orthogonal time-of-flight mass spectrometer, and a multi-stage MS/MS analysis was conducted using a triple quadrupole-linear ion trap mass spectrometer. Both instruments were operated in the positive ionization mode and are equipped with electrospray ionization. Abundant triply charged [M+H]³⁺ species were observed in the single-stage analysis of all the evaluated compounds with mass accuracies of less than 8 ppm in mass error. MS/MS analysis showed that the evaluated gemini surfactants exhibited peptide-related dissociation characteristics because of the presence of amino acids within the compounds' spacer region. In particular, diagnostic product ions were originated from the neutral loss of ammonia from the amino acids' side chain resulting in the formation of pipecolic acid at the N-terminus part of the gemini surfactants. In addition, a charge-directed amide bond cleavage was initiated by the amino acids' side chain producing a protonated α-amino-ε-caprolactam ion and its complimentary C-terminus ion that contains quaternary amines. MS/MS and MS³ analysis revealed common fragmentation behavior among all tested compounds, resulting in the production of a universal MS/MS fragmentation pathway. Copyright © 2017 John Wiley & Sons, Ltd.

Multiple sclerosis: Therapeutic applications of advancing drug delivery systems

Multiple sclerosis (MS) is an inflammatory autoimmune disease of the central nervous system, which is accompanying with demyelination, neurodegeneration and sensibility to oxidative stress. In MS, auto-reactive lymphocytes cross the blood-brain barrier (BBB) and reside in the perivenous demyelinating lesions which create various distinct inflammatory demyelinated plaques situated predominantly in the white matter. The current MS-related therapeutic approaches can be classified into disease-modifying therapies (DMTs) and symptomatic therapy. DMTs suppress circulating immune cells, inhibit passing the BBB and decrease the inflammatory responses. Recent advances have remarkably delayed disease development and improved the quality of life for numerous patients. In spite of major improvements in therapeutic options, there are some limitations regarding the routes of administration and the necessity for repeated and long-term dosing in which cause to systemic disadvantageous consequences and patient non-compliance. Nanotechnology presents promising approaches to improve autoimmune disease treatment with the capability to overcome many of the limitations common to the current immunosuppressive and biological therapies. Here we emphasis on nanomedicine-based drug delivery approaches of biological immunomodulatory mediators for the treatment of multiple sclerosis. This comprehensive review details the most successful drugs in MS therapy and also focuses on conceptions and clinical potential of novel nanomedicine attitudes for inducing immunosuppression and immunological tolerance in MS to modulate abnormal and pathologic immune responses.

Inhaled gene delivery: a formulation and delivery approach

INTRODUCTION

Gene therapy is a potential alternative to treat a number of diseases. Different hurdles are associated with aerosol gene delivery due to the susceptibility of plasmid DNA (pDNA) structure to be degraded during the aerosolization process. Different strategies have been investigated in order to protect and efficiently deliver pDNA to the lungs using non-viral vectors. To date, no successful therapy involving non-viral vectors has been marketed, highlighting the need for further investigation in this field. Areas covered: This review is focused on the formulation and delivery of DNA to the lungs, using non-viral vectors. Aerosol gene formulations are divided according to the current delivery systems for the lung: nebulizers, dry powder inhalers and pressurized metered dose inhalers; highlighting its benefits, challenges and potential application. Expert opinion: Successful aerosol delivery is achieved when the supercoiled DNA structure is protected during aerosolization. A formulation strategy or compounds that can protect, stabilize and efficiently transfect DNA into the cells is desired in order to produce an effective, low-cost and safe formulation. Nebulizers and dry powder inhalers are the most promising approaches to be used for aerosol delivery, due to the lower shear forces involved. In this context it is also important to highlight the importance of considering the 'pDNA-formulation-device system' as an integral part of the formulation development for a successful nucleic acid delivery.

Recent progress in gene therapy to deliver nucleic acids with multivalent cationic vectors

Due to the potential use as transfecting agents of nucleic acids (DNA or RNA), multivalent cationic non-viral vectors have received special attention in the last decade. Much effort has been addressed to synthesize more efficient and biocompatible gene vectors able to transport nucleic acids into the cells without provoking an immune response. Among them, the mostly explored to compact and transfect nucleic acids are: (a) gemini and multivalent cationic lipids, mixed with a helper lipid, by forming lipoplexes; and (b) cationic polymers, polycations, and polyrotaxanes, by forming polyplexes. This review is focused on the progress and recent advances experimented in this area, mainly during the present decade, devoting special attention to the lipoplexes and polyplexes, as follows: (a) to its biophysical characterization (mainly electrostatics, structure, size and morphology) using a wide variety of experimental methods; and (b) to its biological activity (transfection efficacy and cytotoxicity) addressed to confirm the optimum formulations and viability of these complexes as very promising gene vectors of nucleic acids in nanomedicine.

Interactions between DNA and Gemini surfactant: impact on gene therapy: part I

Nonviral gene therapy using gemini surfactants is a unique approach to medicine that can be adapted toward the treatment of various diseases. Recently, gemini surfactants have been utilized as candidates for the formation of nonviral vectors. The chemical structure of the surfactant (variations in the alkyl tail length and spacer/head group) and the resulting physicochemical properties of the lipoplexes are critical parameters for efficient gene transfection. Moreover, studying the interaction of the surfactant with DNA can help in designing an efficient vector and understanding how transfection complexes overcome various cellular barriers. Part I of this review provides an overview of various types of gemini surfactants designed for gene therapy and their transfection efficiency; and Part II will focus on different novel methods utilized to understand the interactions between the gemini and DNA in a lipoplex.

Non-viral gene therapy: Gains and challenges of non-invasive administration methods

Gene therapy is becoming an influential part of the rapidly increasing armamentarium of biopharmaceuticals for improving health and combating diseases. Currently, three gene therapy treatments are approved by regulatory agencies. While these treatments utilize viral vectors, non-viral alternative technologies are also being developed to improve the safety profile and manufacturability of gene carrier formulations. We present an overview of gene-based therapies focusing on non-viral gene delivery systems and the genetic therapeutic tools that will further revolutionize medical treatment with primary focus on the range and development of non-invasive delivery systems for dermal, transdermal, ocular and pulmonary administrations and perspectives on other administration methods such as intranasal, oral, buccal, vaginal, rectal and otic delivery.

Nanotechnology-based inhalation treatments for lung cancer: state of the art

Considering the challenges associated with conventional chemotherapy, targeted and local delivery of chemotherapeutics via nanoparticle (NP) carriers to the lungs is an emerging area of interest. Recent studies and growing clinical application in cancer nanotechnology showed the huge potential of NPs as drug carriers in cancer therapy, including in lung carcinoma for diagnosis, imaging, and theranostics. Researchers have confirmed that nanotechnology-based inhalation chemotherapy is viable and more effective than conventional chemotherapy, with lesser side effects. Recently, many nanocarriers have been investigated, including liposomes, polymeric micelles, polymeric NPs, solid lipid NPs, and inorganic NPs for inhalation treatments of lung cancer. Yet, the toxicity of such nanomaterials to the lungs tissues and further distribution to other organs due to systemic absorption on inhalation delivery is a debatable concern. Here, prospect of NPs-based local lung cancer targeting through inhalation route as well as its associated challenges are discussed.

Physical Characterization of Gemini Surfactant-Based Synthetic Vectors for the Delivery of Linear Covalently Closed (LCC) DNA Ministrings

In combination with novel linear covalently closed (LCC) DNA minivectors, referred to as DNA ministrings, a gemini surfactant-based synthetic vector for gene delivery has been shown to exhibit enhanced delivery and bioavailability while offering a heightened safety profile. Due to topological differences from conventional circular covalently closed (CCC) plasmid DNA vectors, the linear topology of LCC DNA ministrings may present differences with regards to DNA interaction and the physicochemical properties influencing DNA-surfactant interactions in the formulation of lipoplexed particles. In this study, N,N-bis(dimethylhexadecyl)-α,ω-propanediammonium(16-3-16)gemini-based synthetic vectors, incorporating either CCC plasmid or LCC DNA ministrings, were characterized and compared with respect to particle size, zeta potential, DNA encapsulation, DNase sensitivity, and in vitro transgene delivery efficacy. Through comparative analysis, differences between CCC plasmid DNA and LCC DNA ministrings led to variations in the physical properties of the resulting lipoplexes after complexation with 16-3-16 gemini surfactants. Despite the size disparities between the plasmid DNA vectors (CCC) and DNA ministrings (LCC), differences in DNA topology resulted in the generation of lipoplexes of comparable particle sizes. The capacity for ministring (LCC) derived lipoplexes to undergo complete counterion release during lipoplex formation contributed to improved DNA encapsulation, protection from DNase degradation, and in vitro transgene delivery.

Impact of phospholipids on plasmid packaging and toxicity of gemini nanoparticles

Understanding the relationship of structural modifications on the assembly and disassembly of synthetic or non-viral gene delivery is crucial with regard to their rational development. This study describes the use of fluorescence correlation spectroscopy (FCS), as a new tool, to investigate the effect of systematic chemical modifications to dicationic N,N-bis(dimethylalkyl)-α,ω-alkanediammonium surfactants (gemini surfactants) on the self-assembly and physical properties of a series of gemini nanoparticles (gemini NPs). A systematic screening of 27 gemini-plasmid (GP) complexes and gemini NPs showed that their final morphology is governed by the pre-compaction of plasmid by the gemini surfactants. The assembly process of gemini-plasmid intermediate complex (GP) and the final gemini NP (or gemini-plasmid-lipid complex, GPL) was monitored by the tracking of the Cy5-labeled plasmid. Based on diffusion properties, GP complexes were larger than gemini NPs (300-500 nm for GP and 200-300 nm for GPLs). Stoichiometric analysis of the raw intensity histograms showed that both GPs and GPLs particles were composed of multiple plasmids. The final GPLs contain fewer plasmids (2-20 per particle) compared to the intermediate GP (5-35 per particle). The addition of phospholipids dispersed and stabilized GPs to form GPL, but the type of phospholipid (DOPE or DD 1:3) had little effect on the final size of the particles. The FCS data were both validated and complemented by the results of studies of dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray scattering and dye-exclusion assays. A model for gemini NP assembly involving supramolecular aggregate intermediates is proposed.

A flow cytometric approach to study the mechanism of gene delivery to cells by gemini-lipid nanoparticles: an implication for cell membrane nanoporation

BACKGROUND

Gemini-lipid nanoparticles have been received major attention recently as non-viral delivery systems due to their successful non-invasive gene delivery through tough barriers such as eye and skin. The aim of this study was to evaluate non-viral gene delivery by a series of dicationic gemini surfactant-phospholipid nanoparticles (GL-NPs) and to explore their mechanism of interaction with cellular membranes of murine PAM212 epidermal keratinocytes.

METHODS

NPs containing pCMV-tdTomato plasmid encoding red fluorescent protein (RFP) were prepared using 12 different gemini surfactants (m-s-m, with m = 12, 16 and 18C alkyl tail and s = 3 and 7C polymethylene spacer group and 7C substituted spacers with 7NH and 7NCH3) and dioleoylphosphatidylethanolamine helper lipid. RFP gene expression and cell viability status were evaluated using flow cytometry. MitoTracker Deep Red mitochondrial stain and the cell impermeable Sytox red nuclear stain were used as indicators of cell viability and cell membrane integrity, respectively.

RESULTS

No significant viability loss was detected in cells transfected with 18-3-18, 18-7-18, 18-7NH-18, and 18-7NCH3-18 NPs, whereas a significant reduction of viability was detected in cells treated with 12-3-12, 12-7-12, 12-7NH-12, 16-7NH-16, or 16-7NCH3-16 GL-NPs. Compared to Lipofectamine Plus, 18-3-18 GL-NPs showed higher transfection efficiency and comparable viability profile by evaluation using MitoTracker Deep Red in PAM212 cells. Flow cytometric analysis of PAM212 cells stained with Sytox red revealed two cell populations with low and high fluorescent intensity, representing cells with partially-porated and highly-porated membranes, respectively. Additional combined staining with MitoTracker and ethidium homodimer showed that that 18-3-18 GL-NPs disturbed cell membrane integrity, while cells were still alive and had mitochondrial activity.

CONCLUSION

Taken together, this study demonstrated that 18-3-18 GL-NPs have higher transfection efficiency and comparable viability profile to the commercial Lipofectamine Plus, and the interaction of 18-3-18 GL-NPs with PAM212 cell membranes involves a permeability increase, possibly through the formation of nanoscale pores, which could explain efficient gene delivery. This novel nanoconstruct appears to be a promising delivery system for further skin gene therapy studies in vivo.

Development of amino acid substituted gemini surfactant-based mucoadhesive gene delivery systems for potential use as noninvasive vaginal genetic vaccination

Aim: Recently, we synthesized amino acid- and peptide-substituted gemini surfactants, ‘biolipids’ that exhibited high transfection efficiency in vitro. In this study, we developed these plasmid DNA and gemini surfactant lipid particles for noninvasive administration in vaginal cavity. Material & methods: Novel formulations of these gene delivery systems were prepared with poloxamer 407 to induce in situ gelling of the formulation and diethylene glycol monoethyl ether to improve their penetration across mucosal tissue. Results: Poloxamer at 16% w/v concentration in diethylene glycol monoethyl ether aqueous solution produced dispersions that gelled near body temperature and had a high yield value, preventing leakage of the formulation from the vaginal cavity. Intravaginal administration in rabbits showed that the glycyl-lysine-substituted gemini surfactant led to a higher gene expression compared with the parent unsubstituted gemini surfactant. Conclusion: This provides a proof-of-concept that amino acid substituted gemini surfactants can be used as noninvasive mucosal (vaginal) gene delivery systems to treat diseases associated with mucosal epithelia.

Synthesis and Properties of a Series of CO2 Switchable Gemini Imidazolium Surfactants

Novel switchable gemini imidazolium surfactants with different carbon atoms in hydrophobic group were successfully synthesized by condensation of fatty acid with triethylene tetramine, then the intermediates were reacted with CO2 to give the imidazolinium bicarbonates. The structures of intermediates and products were identified by IR and 1H-NMR spectra. As the results show, the structures of the products obtained correspond to the target compounds designed. By surface tension measurements, these Gemini surfactants have excellent surface activity with low cmc and surface tension. The conductivity and surface tension cycles show that these surfactants could be switched from imidazoline (neutral form) to imidazolium bicarbonate (charged form) reversibly and repeatedly.

Bis-quaternary gemini surfactants as components of nonviral gene delivery systems: a comprehensive study from physicochemical properties to membrane interactions

Gemini surfactants have been successfully used as components of gene delivery systems. In the present work, a family of gemini surfactants, represented by the general structure [CmH2m+1(CH3)2N(+)(CH2)sN(+)(CH3)2CmH2m+1]2Br(-), or simply m-s-m, was used to prepare cationic gene carriers, aiming at their application in transfection studies. An extensive characterization of the gemini surfactant-based complexes, produced with and without the helper lipids cholesterol and DOPE, was carried out in order to correlate their physico-chemical properties with transfection efficiency. The most efficient complexes were those containing helper lipids, which, combining amphiphiles with propensity to form structures with different intrinsic curvatures, displayed a morphologically labile architecture, putatively implicated in the efficient DNA release upon complex interaction with membranes. While complexes lacking helper lipids were translocated directly across the lipid bilayer, complexes containing helper lipids were taken up by cells also by macropinocytosis. This study contributes to shed light on the relationship between important physico-chemical properties of surfactant-based DNA vectors and their efficiency to promote gene transfer, which may represent a step forward to the rational design of gene delivery systems.

Gemini imidazolium surfactants: synthesis and their biophysiochemical study

New gemini imidazolium surfactants 9-13 have been synthesized by a regioselective epoxy ring-opening reaction under solvent-free conditions. The surface properties of these new gemini surfactants were evaluated by surface tension and conductivity measurements. These surfactants have been found to have low critical micelle concentration (cmc) values as compared to other categories of gemini cationic surfactants and also showed the tendency to form premicellar aggregates in solution at sufficiently low concentration below their cmc values. The thermal degradation of these surfactants was determined by thermograviometry analysis (TGA). These new cationic surfactants have a good DNA binding capability as determined by agarose gel electrophoresis and ethidium bromide exclusion experiments. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line.

Physical factors affecting plasmid DNA compaction in stearylamine-containing nanoemulsions intended for gene delivery

Cationic lipids have been used in the development of non-viral gene delivery systems as lipoplexes. Stearylamine, a cationic lipid that presents a primary amine group when in solution, is able to compact genetic material by electrostatic interactions. In dispersed systems such as nanoemulsions this lipid anchors on the oil/water interface confering a positive charge to them. The aim of this work was to evaluate factors that influence DNA compaction in cationic nanoemulsions containing stearylamine. The influence of the stearylamine incorporation phase (water or oil), time of complexation, and different incubation temperatures were studied. The complexation rate was assessed by electrophoresis migration on agarose gel 0.7%, and nanoemulsion and lipoplex characterization was done by Dynamic Light Scattering (DLS). The results demonstrate that the best DNA compaction process occurs after 120 min of complexation, at low temperature (4 ± 1 °C), and after incorporation of the cationic lipid into the aqueous phase. Although the zeta potential of lipoplexes was lower than the results found for basic nanoemulsions, the granulometry did not change. Moreover, it was demonstrated that lipoplexes are suitable vehicles for gene delivery.

Visualization of plasmid delivery to keratinocytes in mouse and human epidermis

The accessibility of skin makes it an ideal target organ for nucleic acid-based therapeutics; however, effective patient-friendly delivery remains a major obstacle to clinical utility. A variety of limited and inefficient methods of delivering nucleic acids to keratinocytes have been demonstrated; further advances will require well-characterized reagents, rapid noninvasive assays of delivery, and well-developed skin model systems. Using intravital fluorescence and bioluminescence imaging and a standard set of reporter plasmids we demonstrate transfection of cells in mouse and human xenograft skin using intradermal injection and two microneedle array delivery systems. Reporter gene expression could be detected in individual keratinocytes, in real-time, in both mouse skin as well as human skin xenografts. These studies revealed that non-invasive intravital imaging can be used as a guide for developing gene delivery tools, establishing a benchmark for comparative testing of nucleic acid skin delivery technologies.

Pulmonary gene delivery using polymeric nonviral vectors

Pulmonary delivery provides an easy and well tolerated means of access for the administration of biomacromolecules to the pulmonary epithelium and could therefore be an attractive approach for local and systemic therapies. A growing number of reports, which are summarized in this review, mirror the viability of pulmonary gene delivery. Special attention has been paid to the biological barriers in the lung that must be overcome for successful delivery, and which can be divided into anatomic, physical, immunologic, and metabolic barriers. In light of these barriers, successful nonviral polymer-based formulations of therapeutic genes are presented depending on the chemical nature of the polymer. In addition to polyethyleneimine-based nonviral vectors, which have been most intensively studied for pulmonary gene delivery in the past, other polymeric, dendritic, and targeted materials are also described here, including novel and biodegradable polymers. As new materials need in vitro or ex vivo testing before in vivo application, sophisticated models for all three approaches have been illustrated. Although pulmonary siRNA delivery enjoys popularity in clinical trials, pulmonary gene delivery has so far not been translated into clinical applications. With this review, potential hurdles are demonstrated, but novel approaches that may lead to optimized systems are described as well.

Tandem mass spectrometric analysis of novel diquaternary ammonium gemini surfactants and their bromide adducts in electrospray-positive ion mode ionization

Gemini surfactants are cationic lipids which are utilized for both in vitro and in vivo gene delivery. Structurally, they are comprised of two hydrophobic tail regions with polar head termini that are attached to one another through a spacer region. Structural elucidation and characterization of 29 novel diquaternary ammonium gemini surfactant molecules were achieved using a quadrupole time-of-flight mass spectrometer (QqToF-MS) and a quadrupole-hexapole-quadrupole mass spectrometer (QhQ-MS). The tested compounds were categorized into four distinct structural families based upon the composition of the spacer region. Single stage (MS), tandem stage (MS/MS) and quasimulti-stage (quasi MS(3)) mass spectrometric analysis allowed for confirmation of each gemini surfactant's molecular composition and structure through the identification of common and unique product ions. Identification of similarities in the gemini surfactants' fragmentation behaviour resulted in the production of a universal fragmentation pathway that can assist in the future MS/MS analysis of novel quaternary ammonium gemini surfactants, with unique product ions being indicative of specific structural elements. Furthermore, evidence for the association of agemini surfactant with bromine counter ion was confirmed during MS analysis of tested gemini surfactants regardless of their chemical composition; previously, evidence for bromine and gemini surfactant association was only observed with compounds bearing short alkyl spacer regions. MS/MS analysis of the bromine adducts was also confirmatory to the molecular structure.Understanding the ionization and fragmentation behaviour of gemini surfactants, including bromine adducts, will allow for future qualitative and quantitative identification of these novel drug delivery agents within biological samples.

Nanoparticles in dermatology

Recent advances in the field of nanotechnology have allowed the manufacturing of elaborated nanometer-sized particles for various biomedical applications. A broad spectrum of particles, extending from various lipid nanostructures such as liposomes and solid lipid nanoparticles, to metal, nanocrystalline and polymer particles have already been tested as drug delivery systems in different animal models with remarkable results, promising an extensive commercialization in the coming years. Controlled drug release to skin and skin appendages, targeting of hair follicle-specific cell populations, transcutaneous vaccination and transdermal gene therapy are only a few of these new applications. Carrier systems of the new generation take advantage of improved skin penetration properties, depot effect with sustained drug release and of surface functionalization (e.g., the binding to specific ligands) allowing specific cellular and subcellular targeting. Drug delivery to skin by means of microparticles and nanocarriers could revolutionize the treatment of several skin disorders. However, the toxicological and environmental safety of micro- and nanoparticles has to be evaluated using specific toxicological studies prior to a wider implementation of the new technology. This review aims to give an overview of the most investigated applications of transcutaneously applied particle-based formulations in the fields of cosmetics and dermatology.