Cationic lipid-protamine-DNA (LPD) complexes for delivery of antisense c-myc oligonucleotides

Use of Protamine in Nanopharmaceuticals-A Review

Macromolecular biomolecules are currently dethroning classical small molecule therapeutics because of their improved targeting and delivery properties. Protamine-a small polycationic peptide-represents a promising candidate. In nature, it binds and protects DNA against degradation during spermatogenesis due to electrostatic interactions between the negatively charged DNA-phosphate backbone and the positively charged protamine. Researchers are mimicking this technique to develop innovative nanopharmaceutical drug delivery systems, incorporating protamine as a carrier for biologically active components such as DNA or RNA. The first part of this review highlights ongoing investigations in the field of protamine-associated nanotechnology, discussing the self-assembling manufacturing process and nanoparticle engineering. Immune-modulating properties of protamine are those that lead to the second key part, which is protamine in novel vaccine technologies. Protamine-based RNA delivery systems in vaccines (some belong to the new class of mRNA-vaccines) against infectious disease and their use in cancer treatment are reviewed, and we provide an update on the current state of latest developments with protamine as pharmaceutical excipient for vaccines.

Delivery of oligonucleotides with lipid nanoparticles

Since their inception in the 1980s, oligonucleotide-based (ON-based) therapeutics have been recognized as powerful tools that can treat a broad spectrum of diseases. The discoveries of novel regulatory methods of gene expression with diverse mechanisms of action are still driving the development of novel ON-based therapeutics. Difficulties in the delivery of this class of therapeutics hinder their in vivo applications, which forces drug delivery systems to be a prerequisite for clinical translation. This review discusses the strategy of using lipid nanoparticles as carriers to deliver therapeutic ONs to target cells in vitro and in vivo. A discourse on how chemical and physical properties of the lipid materials could be utilized during formulation and the resulting effects on delivery efficiency constitutes the major part of this review.

Protamine-oligonucleotide-nanoparticles: Recent advances in drug delivery and drug targeting

Application of oligonucleotides as active compounds has become a crucial field of pharmaceutical research in recent years. In order to improve inadequate transfection rate and to avoid rapid enzymatic degradation of antisense oligonucleotides (AS-ODNs) a novel nanoparticulate delivery system was reported by our group at the beginning of 2000. AS-ODNs are condensed by the polycationic peptide protamine into solid particles in the size range of 100-200nm. Nanoparticle formation is driven by a self-assembling process based on electrostatic interactions between the oppositely charged biomolecules. This new delivery system was named "proticles" and showed very efficient protection against enzymatic digestion, high transfection rates and significant antisense effects in vitro. Throughout broader research, this promising approach was enlarged, and AS-ODNs were replaced by siRNA or CpG-oligonucleotides to address the aspect of immune-modulation and vaccination. More recent studies on proticles verified upscaling of the self-assembling process as well as the potential of proticle formulations for active drug targeting, like tumor- or atherosclerotic plaque targeting. Thereby also the application for diagnostic purposes was emphasized. This review will focus on the characterization of the nucleoprotein protamine as well as on the variety of possible nucleotides/peptides which were already assembled into the proticle matrix. Furthermore it will provide an insight into the broad area of application where proticles can present a valuable tool for successful oligonucleotide delivery.

Ternary nanoparticles composed of cationic solid lipid nanoparticles, protamine, and DNA for gene delivery

Background

The objective of this research was to design an effective gene delivery system composed of cationic solid lipid nanoparticles (SLNs), protamine, and Deoxyribonucleic acid DNA.

Methods

Cationic SLNs were prepared using an aqueous solvent diffusion method with octadecylamine as the cationic lipid material. First, protamine was combined with DNA to form binary protamine/DNA nanoparticles, and the ternary nanoparticle gene delivery system was then obtained by combining binary protamine/DNA nanoparticles with cationic SLNs. The size, zeta potential, and ability of the binary and ternary nanoparticles to compact and protect DNA were characterized. The effect of octadecylamine content in SLNs and the SLNS/DNA ratios on transfection efficiency, cellular uptake and cytotoxicity of the ternary nanoparticles were also assessed using HEK293 cells.

Results

When the weight ratio of protamine to DNA reached 1.5:1, the plasmid DNA could be effectively compacted and protected. The average hydrodynamic diameter of the ternary nanoparticles when combined with protamine increased from 188.50 ± 0.26 nm to 259.33 ± 3.44 nm, and the zeta potential increased from 25.50 ± 3.30 mV to 33.40 ± 2.80 mV when the weight ratio of SLNs to DNA increased from 16/3 to 80/3. The ternary nanoparticles showed high gene transfection efficiency compared with Lipofectamine™ 2000/DNA nanoparticles. Several factors that might affect gene transfection efficiency, such as content and composition of SLNs, post-transfection time, and serum were examined. The ternary nanoparticles composed of SLNs with 15 wt% octadecylamine (50/3 weight ratio of SLNs to DNA) showed the best transfection efficiency (26.13% ± 5.22%) in the presence of serum. It was also found that cellular uptake of the ternary nanoparticles was better than that of the SLN/DNA and binary protamine/DNA nanoparticle systems, and DNA could be transported to the nucleus.

Conclusion

SLNs enhanced entry of binary protamine/DNA nanoparticles into the cell, and protamine protected DNA from enzyme degradation and transported DNA into the nucleus. Compared with Lipofectamine 2000/DNA nanoparticles, these cationic ternary nanoparticles showed relatively durable and stable gene transfection in the presence of serum.

Efficient down-regulation of PKC-α gene expression in A549 lung cancer cells mediated by antisense oligodeoxynucleotides in dendrosomes

The completion of human genome project has increased our knowledge of the molecular mechanisms of many diseases, including cancer, thus providing new opportunities for gene therapy. Antisense oligodeoxynucleotides (AsODN) possess great potential as sequence-specific therapeutic agents, which in contrast to classic treatments provide more efficient and target-specific approach to modulate disease-related genes. To be therapeutically effective, sufficient concentrations of intact AsODN must bypass membrane barriers and access the site of action. In this study, a dendrosome delivery strategy was designed to improve the encapsulation of AsODN in non-cationic liposomes to target PKC-α in lung cancer cells in vitro. Subcellular trafficking of fluorescently labeled AsODN was visualized using confocal microscopy. Uptake and expression of mRNA and target protein after AsODN delivery was measured by flow cytometry, qRT-PCR and Western blot analysis, respectively. Dendrosomes showed favorable physicochemical parameters: high encapsulation efficiency and uptake in serum-containing medium with no apparent cytotoxicity. AsODN encapsulated in dendrosome efficiently and specifically suppress the target gene at both mRNA and protein levels. Additional in vivo studies on the application of dendrosome as a delivery system for nucleic acid molecules may lead to improvement of this technology and facilitate the development of therapeutic antisense techniques.

Cellular delivery of cationic lipid nanoparticle-based SMAD3 antisense oligonucleotides for the inhibition of collagen production in keloid fibroblasts

SMAD3 is a key player in the TGFβ signaling pathway as a primary inducer of fibrosis. The inhibition of SMAD3 production is one strategy to alleviate fibrosis in keloid fibroblasts. In the present study, antisense oligonucleotides (ASOs) against SMAD3 were designed to specifically block the expression of SMAD3. The cationic lipid nanoparticles (cLNs) were formulated to enhance an intracellular activity of SMAD3 ASOs in keloid fibroblasts. This formulation was prepared using melt-homogenization method, composed of 3-[N-(N',N'-dimethylaminoethane)-carbamol] cholesterol (DC-Chol), dioleoylphosphatidylethanolamine (DOPE), Tween20, and trimyristin as a lipid core (1:1:1:1.3, w/w). The size and zeta potential of cLNs and cLN/ASO complexes were measured using light scattering. AFM was used to confirm the morphology and the size distribution of cLNs and cLN/ASO complexes. The prepared cLNs had a nano-scale sized spherical shape with highly positive charge, which were physically stable without aggregation during the storage. The cLN/SMAD3 ASO complexes were successfully generated and internalized onto keloid fibroblasts without toxicity. After the treatment with cLN/ASO complexes, SMAD3 was inhibited and collagen type I was also significantly suppressed in keloid fibroblasts. These results suggest that SMAD3 ASOs complexed with cLNs have a therapeutic potential to suppress collagen deposition in fibrotic diseases. Therefore, this strategy might be developed to lead to anti-fibrotic therapies.

A covalently stabilized lipid-polycation-DNA (sLPD) vector for antisense oligonucleotide delivery

Antisense oligonucleotide G3139 is designed for Bcl-2 downregulation and is known to induce toll-like receptor activation. Novel stabilized lipid-polycation-DNA (sLPD) nanoparticles were constructed and evaluated for the delivery of G3139 to human carcinoma KB cells and for bioactivity in vivo. Polyethylenimine (PEI) was incorporated as a DNA condensing agent. The lipid composition used was DOTAP/DDAB/Chol/TPGS/linoleic acid/hexadecenal at molar ratios of 30/30/34/1/5/0.2. The nanoparticles were stabilized by the formation of a reversible covalent bond between the aldehyde group on the cis-11-hexadecenal and amines on the PEI. When sLPDs were used to transfect KB cells, 90.4% Bcl-2 downregulation was observed, compared to no significant downregulation by free G3139 and 54.6% downregulation by nonstabilized LPD-G3139. The sLPDs were then evaluated for therapeutic efficacy in mice bearing KB subcutaneous tumors and were found to trigger a strong antitumor response, inhibiting tumor growth and prolonging survival with 72% increase in lifespan (ILS). Consistent with previous reports on other G3139 nanoparticles, the increased antitumor activities of sLPDs in vivo were found to be associated with increased cytokine induction rather than Bcl-2 downregulation, suggesting an immunological mechanism.

Novel siRNA delivery system to target podocytes in vivo

Podocytes are injured in several glomerular diseases. To alter gene expression specifically in podocytes in vivo, we took advantage of their active endocytotic machinery and developed a method for the targeted delivery of small interfering ribonucleic acids (siRNA). We generated an anti-mouse podocyte antibody that binds to rat and mouse podocytes in vivo. The polyclonal IgG antibody was cleaved into monovalent fragments, while preserving the antigen recognition sites. One Neutravidin molecule was linked to each monovalent IgG via the available sulfohydryl group. Protamine, a polycationic nuclear protein and universal adaptor for anionic siRNA, was linked to the neutravidin via biotin. The delivery system was named shamporter (sheep anti mouse podocyte transporter). Injection of shamporter coupled with either nephrin siRNA or TRPC6 siRNA via tail vein into normal rats substantially reduced the protein levels of nephrin or TRPC6 respectively, measured by western blot analysis and immunostaining. The effect was target specific because other podocyte-specific genes remained unchanged. Shamporter + nephrin siRNA induced transient proteinuria in rats. Control rats injected with shamporter coupled to control-siRNA showed no changes. These results show for the first time that siRNA can be delivered efficiently and specifically to podocytes in vivo using an antibody-delivery system.

Anionic LPD complexes for gene delivery to macrophage: preparation, characterization and transfection in vitro

In the present study, anionic lipid/peptide/DNA (LPD) complexes consisting of pH-sensitive liposome and protamine were introduced as the carriers targeting RAW 264.7 cell line, which had been reported to be difficult for transfection. The LPD complexes were physically characterized. The pH sensitivities and sizes of liposomes were investigated. The zeta potentials of LPD complexes altered significantly with the addition of protamine sulfate and anionic liposomes. It was demonstrated that the carriers produced an increase in the stability of plasmid DNA against DNase I. The TEM showed that the size distribution of LPD complexes was irregular. In the in vitro transfection, the efficiency of LPD complexes was higher than that of Lipofectamine 2000 and protamine/DNA complexes, but lower than that of electroporation. A possible mechanism for the internalization of plasmid DNA mediated by the anionic LPD complexes was also proposed. With a high safety certificated by MTT assay, LPD complexes prepared in this study might be potentially employed as a macrophage gene therapy.

Novel nanomaterials for clinical neuroscience

Neurodegenerative disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke are rapidly increasing as population ages. The field of nanomedicine is rapidly expanding and promises revolutionary advances to the diagnosis and treatment of devastating human diseases. This paper provides an overview of novel nanomaterials that have potential to improve diagnosis and therapy of neurodegenerative disorders. Examples include liposomes, nanoparticles, polymeric micelles, block ionomer complexes, nanogels, and dendrimers that have been tested clinically or in experimental models for delivery of drugs, genes, and imaging agents. More recently discovered nanotubes and nanofibers are evaluated as promising scaffolds for neuroregeneration. Novel experimental neuroprotective strategies also include nanomaterials, such as fullerenes, which have antioxidant properties to eliminate reactive oxygen species in the brain to mitigate oxidative stress. Novel technologies to enable these materials to cross the blood brain barrier will allow efficient systemic delivery of therapeutic and diagnostic agents to the brain. Furthermore, by combining such nanomaterials with cell-based delivery strategies, the outcomes of neurodegenerative disorders can be greatly improved.

Nanomedicine in the diagnosis and therapy of neurodegenerative disorders

Neurodegenerative and infectious disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke are rapidly increasing as population's age. Alzheimer's disease alone currently affects 4.5 million Americans, and more than $100 billion is spent per year on medical and institutional care for affected people. Such numbers will double in the ensuing decades. Currently disease diagnosis for all disorders is made, in large measure, on clinical grounds as laboratory and neuroimaging tests confirm what is seen by more routine examination. Achieving early diagnosis would enable improved disease outcomes. Drugs, vaccines or regenerative proteins present "real" possibilities for positively affecting disease outcomes, but are limited in that their entry into the brain is commonly restricted across the blood-brain barrier. This review highlights how these obstacles can be overcome by polymer science and nanotechnology. Such approaches may improve diagnostic and therapeutic outcomes. New developments in polymer science coupled with cell-based delivery strategies support the notion that diseases that now have limited therapeutic options can show improved outcomes by advances in nanomedicine.

Interplay of polyethyleneimine molecular weight and oligonucleotide backbone chemistry in the dynamics of antisense activity

The widespread utilization of gene silencing techniques, such as antisense, is impeded by the poor cellular delivery of oligonucleotides (ONs). Rational design of carriers for enhanced ON delivery demands a better understanding of the role of the vector on the extent and time course of antisense effects. The aim of this study is to understand the effects of polymer molecular weight (MW) and ON backbone chemistry on antisense activity. Complexes were prepared between branched polyethyleneimine (PEI) of various MWs and ONs of phosphodiester and phosphorothioate chemistries. We measured their physico-chemical properties and evaluated their ability to deliver ONs to cells, leading to an antisense response. Our key finding is that the antisense activity is not determined solely by PEI MW or by ON chemistry, but rather by the interplay of both factors. While the extent of target mRNA down-regulation was determined primarily by the polymer MW, dynamics were determined principally by the ON chemistry. Of particular importance is the strength of interactions between the carrier and the ON, which determines the rate at which the ONs are delivered intracellularly. We also present a mathematical model of the antisense process to highlight the importance of ON delivery to antisense down-regulation.

Nanotools for megaproblems: probing protein misfolding diseases using nanomedicine modus operandi

Misfolding and self-assembly of proteins in nanoaggregates of different sizes and morphologies (nanoensembles, primary nanofilaments, nanorings, filaments, protofibrils, fibrils, etc.) is a common theme unifying a number of human pathologies termed protein misfolding diseases. Recent studies highlight increasing recognition of the public health importance of protein misfolding diseases, including various neurodegenerative disorders and amyloidoses. It is understood now that the first essential elements in the vast majority of neurodegenerative processes are misfolded and aggregated proteins. Altogether, the accumulation of abnormal protein nanoensembles exerts toxicity by disrupting intracellular transport, overwhelming protein degradation pathways, and/or disturbing vital cell functions. In addition, the formation of inclusion bodies is known to represent a major problem in the production of recombinant therapeutic proteins. Formulation of these therapeutic proteins into delivery systems and their in vivo delivery are often complicated by protein association. Thus, protein folding abnormalities and subsequent events underlie a multitude of human pathologies and difficulties with protein therapeutic applications. The field of medicine therefore can be greatly advanced by establishing a fundamental understanding of key factors leading to misfolding and self-assembly responsible for various protein folding pathologies. This article overviews protein misfolding diseases and outlines some novel and advanced nanotechnologies, including nanoimaging techniques, nanotoolboxes and nanocontainers, complemented by appropriate ensemble techniques, all focused on the ultimate goal to establish etiology and to diagnose, prevent, and cure these devastating disorders.