Intracellular tracking of protamine/antisense oligonucleotide nanoparticles and their inhibitory effect on HIV-1 transactivation

A Review of Protein- and Peptide-Based Chemical Conjugates: Past, Present, and Future

Over the past few decades, the complexity of molecular entities being advanced for therapeutic purposes has continued to evolve. A main propellent fueling innovation is the perpetual mandate within the pharmaceutical industry to meet the needs of novel disease areas and/or delivery challenges. As new mechanisms of action are uncovered, and as our understanding of existing mechanisms grows, the properties that are required and/or leveraged to enable therapeutic development continue to expand. One rapidly evolving area of interest is that of chemically enhanced peptide and protein therapeutics. While a variety of conjugate molecules such as antibody-drug conjugates, peptide/protein-PEG conjugates, and protein conjugate vaccines are already well established, others, such as antibody-oligonucleotide conjugates and peptide/protein conjugates using non-PEG polymers, are newer to clinical development. This review will evaluate the current development landscape of protein-based chemical conjugates with special attention to considerations such as modulation of pharmacokinetics, safety/tolerability, and entry into difficult to access targets, as well as bioavailability. Furthermore, for the purpose of this review, the types of molecules discussed are divided into two categories: (1) therapeutics that are enhanced by protein or peptide bioconjugation, and (2) protein and peptide therapeutics that require chemical modifications. Overall, the breadth of novel peptide- or protein-based therapeutics moving through the pipeline each year supports a path forward for the pursuit of even more complex therapeutic strategies.

Modified Stability of microRNA-Loaded Nanoparticles

microRNAs represent promising drugs to treat and prevent several diseases, such as diabetes mellitus. microRNA delivery brings many obstacles to overcome, and one strategy to bypass them is the manufacturing of self-assembled microRNA protein nanoparticles. In this work, a microRNA was combined with the cell-penetrating peptide protamine, forming so-called proticles. Previous studies demonstrated a lack of microRNA dissociation from proticles. Therefore, the goal of this study was to show the success of functionalizing binary proticles with citric acid in order to reduce the binding strength between the microRNA and protamine and further enable sufficient dissociation. Thus, we outline the importance of the present protons provided by the acid in influencing colloidal stability, achieving a constant particle size, and monodispersing the particle size distribution. The use of citric acid also provoked an increase in drug loading. Against all expectations, the AFM investigations demonstrated that our nanoparticles were loose complexes mainly consisting of water, and the addition of citric acid led to a change in shape. Moreover, a successful reduction in binding affinity and nanoparticulate stability are highlighted. Low cellular toxicity and a constant cellular uptake are demonstrated, and as uptake routes, active and passive pathways are discussed.

Recent Advances in the Delivery Carriers and Chemical Conjugation Strategies for Nucleic Acid Drugs

With the development of new anticancer medicines, novel modalities are being explored for cancer treatment. For many years, conventional modalities, such as small chemical drugs and antibody drugs, have worked by "inhibiting the function" of target proteins. In recent years, however, nucleic acid drugs, such as ASOs and siRNAs, have attracted attention as a new modality for cancer treatment because nucleic acid drugs can directly promote the "loss of function" of target genes. Recently, nucleic acid drugs for use in cancer therapy have been extensively developed and some of them have currently been under investigation in clinical trials. To develop novel nucleic acid drugs for cancer treatment, it is imperative that cancer researchers, including ourselves, cover and understand those latest findings. In this review, we introduce and provide an overview of various DDSs and ligand modification technologies that are being employed to improve the success and development of nucleic acid drugs, then we also discuss the future of nucleic acid drug developments for cancer therapy. It is our belief this review will increase the awareness of nucleic acid drugs worldwide and build momentum for the future development of new cancer-targeted versions of these drugs.

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.

Decoding Live Cell Interactions with Multi-Nanoparticle Systems: Differential Implications for Uptake, Trafficking, and Gene Regulation

Surface modification with oligonucleotides renders gold nanoparticles to endocytose through very different pathways as compared to unmodified ones. Such oligonucleotide-modified gold nanoparticles (OGNs) have been exploited as effective nanocarriers for gene regulation therapies. Notably, in an effort to reduce overall dosage and provide safer transition to the clinic, cooperative systems composed of two or more discrete nanomaterials have been recently proposed as an alternative to intrinsically multifunctional nanoparticles. Yet, our understanding of such systems designed to synergistically cooperate in their diagnostic or therapeutic functions remains acutely limited. Specifically, cellular interactions and uptake of OGNs are poorly understood when the cell simultaneously interacts with other types of nanoparticles. Here, we investigated the impact of simultaneous uptake of similar-sized iron oxide nanoparticles (IOPs) on the endocytosis and gene regulation function of OGNs, whose analogues have been proposed for sensitization, targeting, and treatment of tumors. We discovered that both the OGN uptake amount and, remarkably, the gene regulation function remained stable when exposed to a very wide range of extracellular concentrations of IOPs. Additionally, the co-localization analysis showed that a proportion of OGNs was co-localized with IOPs inside cells, which hints at the presence of similar trafficking pathways for OGNs and IOPs following endocytosis. Taken together, our observations indicate that while the OGN endocytosis is highly independent of the IOP endocytosis, it shares transport pathways inside cells-but does so without affecting the gene regulation behavior. These results provide key insights into concomitant interactions of cells with diverse nanoparticles and offer a basis for the future design and optimization of cooperative nanomaterials for diverse theranostic applications.

Comparison of PEGylated and non-PEGylated proticles: An in vitro and in vivo study

The development of so-called Proticles opens attractive possibilities for new drug delivery systems. Proticles are nanoparticles (NPs), which are formed by self-assembly of negatively charged oligonucleotides in combination with the positively charged peptide protamine. Polyethylene glycol (PEG) is a widely known pharmaceutical agent to stop particle growth and prolong circulation half-life of drug delivery systems. Therefore, two different NP formulations - one PEGylated and one non-PEGylated - were used in this work to gain information about the biological stability and half-life in circulation of Proticles. Thus, this study presents data of in vitro stability and in vivo pharmacokinetics of both, non-PEGylated and PEGylated Proticles radiolabeled with ¹¹¹InCl₃. The study demonstrated that successful radiolabeling of both Proticle-formulations was performed resulting in high radiochemical yields (> 85 %). Furthermore, the influence of PEGylation on the in vitro stability of ¹¹¹In-radiolabeled NPs was investigated. No significant difference due to PEGylation was found. Unlike in vitro results, non-PEGylated ¹¹¹In-Proticles seemed to degrade faster in vivo than PEGylated ¹¹¹In-proticles, resulting in significantly higher blood values (¹¹¹In-PEG-proticles: 0.23 ± 0.01 % ID/g 1 h p.i.; ¹¹¹In-proticles: 0.06 ± 0.01 % ID/g 1 h p.i.; p < 0.05). Visualized by SPECT imaging urinary excretion represented the major pathway of elimination for both NP-formulations. In conclusion, this study provides data indicating a positive influence of PEG-derivatization on the biodistribution and pharmacokinetics of Proticles. These results form the basis for further developments as drug delivery and active drug targeting devices.

Assessment of the permeability and toxicity of polymeric nanocapsules using the zebrafish model

Aim: To assess the capacity of a new drug delivery nanocapsule (NC) with a double shell of hyaluronic acid and protamine to overcome biological barriers using the zebrafish model. Materials & methods: NCs were prepared by the solvent displacement method, tagged with fluorescent makers and physicochemically characterized. Toxicity was evaluated according to the Fish Embryo Acute Toxicity test, and permeability was tested by exposing zebrafish, with and without chorion, to the fluorescent NCs. Results: Toxicity of NCs was very low as compared with that of a control nanoemulsion. Double-shell NCs were able to cross chorion and skin. Conclusion: Beyond the potential value of hyaluronic acid:protamine NCs for overcoming epithelial barriers, this works highlights the utility of zebrafish for fast screening of nanocarriers.

Manufacturing of a Secretoneurin Drug Delivery System with Self-Assembled Protamine Nanoparticles by Titration

Since therapeutic peptides and oligonucleotides are gathering interests as active pharmaceutical ingredients (APIs), nanoparticulate drug delivery systems are becoming of great importance. Thereby, the possibility to design drug delivery systems according to the therapeutic needs of APIs enhances clinical implementation. Over the last years, the focus of our group was laid on protamine-oligonucleotide-nanoparticles (so called proticles), however, the possibility to modify the size, zeta potential or loading efficiencies was limited. Therefore, at the present study we integrated a stepwise addition of protamine (titration) into the formation process of proticles loaded with the angiogenic neuropeptide secretoneurin (SN). A particle size around 130 nm was determined when proticles were assembled by the commonly used protamine addition at once. Through application of the protamine titration process it was possible to modify and adjust the particle size between approx. 120 and 1200 nm (dependent on mass ratio) without influencing the SN loading capacity. Dynamic light scattering pointed out that the difference in particle size was most probably the result of a secondary aggregation. Initially-formed particles of early stages in the titration process aggregated towards bigger assemblies. Atomic-force-microscopy images also revealed differences in morphology along with different particle size. In contrast, the SN loading was only influenced by the applied mass ratio, where a slight saturation effect was observable. Up to 65% of deployed SN could be imbedded into the proticle matrix. An in-vivo biodistribution study (i.m.) showed a retarded distribution of SN from the site of injection after the application of a SN-proticle formulation. Further, it was demonstrated that SN loaded proticles can be successfully freeze-dried and resuspended afterwards. To conclude, the integration of the protamine titration process offers new possibilities for the formulation of proticles in order to address key parameters of drug delivery systems as size, API loading or modified drug release.

Improving bioavailability and biodistribution of anti-HIV chemotherapy

In the context of the treatment of HIV/AIDS, many improvements have been achieved since the introduction of the combination therapy (HAART). Nevertheless, no cure for this disease has been so far possible, because of some particular features of the therapies. Among them, two important ones have been selected and will be the subject of this review. The first main concern in the treatments is the poor drug bioavailability, resulting in repeated administrations and therefore a demanding compliance (drug regimens consist of multiple drugs daily intake, and non-adherence to therapy is among the important reasons for treatment failure). A second important challenge is the need to target the drugs into the so-called reservoirs and sanctuaries, i.e. cells or body compartments where drugs cannot penetrate or are distributed in sub-active concentrations. The lack of antiviral action in these regions allows the virus to lie latent and start to replicate at any moment after therapy suspension. Recent drug delivery strategies addressing these two limitations will be presented in this review. In the first part, strategies to improve the bioavailability are proposed in order to overcome the absorption or the target cell barrier, or to extend the efficacy time of drugs. In the second section, the biodistribution issues are considered in order to target the drugs into the reservoirs and the sanctuaries, in particular the mononuclear phagocyte system and the brain.

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.

Protamine sulfate-calcium carbonate-plasmid DNA ternary nanoparticles for efficient gene delivery

Ternary nanoparticles, protamine sulfate-calcium carbonate-plasmid DNA (PS-CaCO3-DNA), were prepared for efficient gene delivery. By adding the cationic polypeptide PS in the co-precipitation system of calcium carbonate and DNA, PS-CaCO3-DNA nanoparticles could be formed by self-assembly facilely. The effect of PS on the properties of the ternary nanoparticles was studied by varying the PS amount in the nanoparticles. The size and ζ-potential measurements indicated that the ternary nanoparticles with an appropriate PS amount exhibited a decreased size and an increased ζ-potential. The in vitro gene transfections mediated by different nanoparticles in 293T cells and HeLa cells were carried out in the presence of 10% fetal bovine serum, using pGL3-Luc and pEGFP-C1 as reporter plasmids. As compared with both PS-DNA nanoparticles and CaCO3-DNA nanoparticles, PS-CaCO3-DNA nanoparticles exhibited significantly enhanced gene delivery efficiency, which was higher than that of Lipofectamine 2000-DNA. Confocal microscopy observation showed that PS-CaCO3-DNA nanoparticles could efficiently deliver DNA to cell nuclei. These results indicated that the ternary PS-CaCO3-DNA nanoparticles prepared in this study have promising applications in gene delivery.

In vivo delivery of cell-permeable antisense hypoxia-inducible factor 1α oligonucleotide to adipose tissue reduces adiposity in obese mice

Ongoing research has gradually recognized and understood the importance of adipose tissue (AT) angiogenesis as a key modulating factor of adipogenesis in the development of obesity. Previously, we carried out the first in vitro demonstration of the down-regulation of hypoxic angiogenesis during adipogenesis using cell-permeable chemical conjugates composed of antisense hypoxia-inducible factor 1α (HIF1α) oligonucleotide (ASO) and low-molecular weight protamine (LMWP). To further confirm the in vivo feasibility, we administered ASO-LMWP conjugates (AL) to diet-induced obese (DIO) mice by intraperitoneal injection (IP). Results showed that the AL conjugates significantly reduced the body weight, total fat tissue weight, and plasma lipid concentrations in the mice. Moreover, the AL conjugates not only decreased liver weight and hepatic triglyceride concentration but also significantly attenuated subcutaneous adipocyte cell size, which was conversely increased in the AL-untreated high-fat diet (HFD) group. Interestingly, more blood vessels were observed in the HFD group than in the lean group, indicating that blood vessel development could induce growth of the fat mass. This pattern was reversed in the AL-treated groups, which displayed a decrease in blood vessel density compared to the AL-untreated HFD group. This study presents the first in vivo evidence, in an obese mouse model, of the feasibility of achieving a biological treatment modality for obesity by blocking the angiogenic transcriptional factor HIF1α, thereby limiting angiogenesis, via the use of an adipose tissue-permeable ASO-LMWP.

Nanotechnology and the treatment of HIV infection

Suboptimal adherence, toxicity, drug resistance and viral reservoirs make the lifelong treatment of HIV infection challenging. The emerging field of nanotechnology may play an important role in addressing these challenges by creating drugs that possess pharmacological advantages arising out of unique phenomena that occur at the “nano” scale. At these dimensions, particles have physicochemical properties that are distinct from those of bulk materials or single molecules or atoms. In this review, basic concepts and terms in nanotechnology are defined, and examples are provided of how nanopharmaceuticals such as nanocrystals, nanocapsules, nanoparticles, solid lipid nanoparticles, nanocarriers, micelles, liposomes and dendrimers have been investigated as potential anti-HIV therapies. Such drugs may, for example, be used to optimize the pharmacological characteristics of known antiretrovirals, deliver anti-HIV nucleic acids into infected cells or achieve targeted delivery of antivirals to the immune system, brain or latent reservoirs. Also, nanopharmaceuticals themselves may possess anti-HIV activity. However several hurdles remain, including toxicity, unwanted biological interactions and the difficulty and cost of large-scale synthesis of nanopharmaceuticals.

Identification of a LNCaP-specific binding peptide using phage display

PURPOSE

To identify a LNCaP-specific peptide using a phage display library and evaluate its potential applications in targeted drug delivery.

METHODS

Binding abilities of selected phages were evaluated by cell phage ELISA. The KYL peptide encoded by the most specific phage clone was synthesized, labeled with fluorescein, and assayed in various cell lines. A fusion peptide composed of the KYL peptide and a proapoptotic peptide ( D )(KLAKLAK)(2) was synthesized, and the cell death effect was evaluated on different cells. Moreover, the KYL peptide was conjugated to a cationic protein, protamine, to explore its potential application in siRNA delivery.

RESULTS

One phage clone with a high binding affinity to LNCaP cells was identified. Cell phage ELISA and immunostaining demonstrated high specificity of this phage to LNCaP cells. The fluorescein-labeled KYL peptide exhibited higher binding to LNCaP cells in comparison to other cells. The fusion peptide composed of the KYL peptide and the proapoptotic peptide induced cell death in LNCaP cells, but not in PC-3 cells. The KYL peptide-protamine conjugate also efficiently delivered a fluorescein-labeled siRNA into LNCaP cells.

CONCLUSION

We identified a LNCaP-specific peptide and demonstrated its potential applications in targeted drug delivery to LNCaP cells.

Topical application of antisense oligonucleotide-loaded chitosan nanoparticles to rats

Skin delivery of antisense oligonucleotides (AsODNs) has exciting potential in the treatment of skin diseases. However, the therapeutic applications of oligonucleotide-based therapies are limited by the instability of these molecules toward nucleases, short half-life in vivo, and insufficient cellular uptake. The purpose of this study was to investigate in vivo antisense effect of AsODN-loaded chitosan nanoparticles after topical application. AsODN-loaded chitosan nanoparticles were topically applied to Sprague Dawley rats (adult and baby). At 1, 3, 6, 9, and 12 days posttransfection, animals' skin samples were taken for measurement of beta-galactosidase (beta-Gal) expression and histological control. After topical application of AsODN-loaded chitosan nanoparticles in different doses, beta-Gal expression reduced significantly. Highest inhibition was observed after 6 days of transfection of nanoparticles. Free AsODNs exhibited 35% of beta-Gal inhibition on the first day. beta-Gal expression was inhibited in approximately 82-85% with transfection of nanoparticles containing 30 microg AsODNs at 6 days. The antisense effect of AsODN-loaded chitosan nanoparticle in baby skin was evaluated at 6 days: 77-86% of beta-Gal suppression was measured and differences between the doses were not significant. Thus, chitosan nanoparticles are useful carrier for delivery of AsODNs into skin cells of rats and may be used for topical application on human skin.

Nanotechnology-based systems for the treatment and prevention of HIV/AIDS

The HIV/AIDS pandemic is an increasing global burden with devastating health-related and socioeconomic effects. The widespread use of antiretroviral therapy has dramatically improved life quality and expectancy of infected individuals, but limitations of currently available drug regimens and dosage forms, alongside with the extraordinary adapting capacity of the virus, have impaired further success. Alongside, circumventing the escalating number of new infections can only be attained with effective and practical preventative strategies. Recent advances in the field of drug delivery are providing evidence that engineered nanosystems may contribute importantly for the enhancement of current antiretroviral therapy. Additionally, groundwork is also being carried out in the field nanotechnology-based systems for developing preventative solutions for HIV transmission. This manuscript reviews recent advances in the field of nanotechnology-based systems for the treatment and prevention of HIV/AIDS. Particular attention is given to antiretroviral drug targeting to HIV reservoirs and the usefulness of nanosystems for developing topical microbicides and vaccines.

Specific down regulation of 3T3-L1 adipocyte differentiation by cell-permeable antisense HIF1alpha-oligonucleotide

Hypoxia is a strong modulator of angiogenesis, accelerating adipose tissue expansion, suggesting that hypoxia inducible factor 1alpha (HIF1alpha) can be a novel target for anti-obesity. We conjugated antisense-HIF1alpha-oligonucleotide (ASO) with low molecular weight protamine (LMWP), a cell-penetrating peptide, to enhance its ability to block hypoxic-angiogenesis, thereby eliciting an anti-obesity effect. Nano-sized ASO-LMWP (AS-L) conjugates enhanced cellular uptake of ASO without yielding a cytotoxic effect and protected the ASO against enzymatic attack and chemical reduction. AS-L showed enhanced intra-cellular localization compared to naked ASO and the complex of ASO with lipofectamine during hypoxic-differentiation. Consequently AS-L induced significant down-regulation of leptin and VEGF gene expressions, thereby reducing fat accumulation in the cell. This proof-of-concept study shows that AS-L produces an inhibitory effect on adipogenesis and angiogenesis during differentiation, indicating LMWP mediated ASO delivery can potentially be a safe and promising treatment for obesity.

Accelerated stem cell labeling with ferucarbotran and protamine

OBJECTIVE

To develop and characterize a clinically applicable, fast and efficient method for stem cell labeling with ferucarbotran and protamine for depiction with clinical MRI.

METHODS

The hydrodynamic diameter, zeta potential and relaxivities of ferucarbotran and varying concentrations of protamine were measured. Once the optimized ratio was found, human mesenchymal stem cells (MSCs) were labeled at varying incubation times (1-24 h). Viability was assessed via Trypan blue exclusion testing. 150,000 labeled cells in Ficoll solution were imaged with T1-, T2- and T2*-weighted sequences at 3 T, and relaxation rates were calculated.

RESULTS

Varying the concentrations of protamine allows for easy modification of the physicochemical properties. Simple incubation with ferucarbotran alone resulted in efficient labeling after 24 h of incubation while assisted labeling with protamine resulted in similar results after only 1 h. Cell viability remained unaffected. R2 and R2* relaxation rates were drastically increased. Electron microscopy confirmed intracellular iron oxide uptake in lysosomes. Relaxation times correlated with results from ICP-AES.

CONCLUSION

Our results show internalization of ferucarbotran can be accelerated in MSCs with protamine, an approved heparin antagonist and potentially clinically applicable uptake-enhancing agent.

Nanotechnologies and controlled release systems for the delivery of antisense oligonucleotides and small interfering RNA

Antisense oligonucleotides and small interfering RNA have enormous potential for the treatment of a number of diseases, including cancer. However, several impediments to their widespread use as drugs still have to be overcome: in particular their lack of stability in physiological fluids and their poor penetration into cells. Association with or encapsulation within nano- and microsized drug delivery systems could help to solve these problems. In this review, we describe the progress that has been made using delivery systems composed of natural or synthetic polymers in the form of complexes, nanoparticles or microparticles.

PTD-modified ATTEMPTS system for enhanced asparaginase therapy: a proof-of-concept investigation

Macromolecular drugs such as proteins and gene products are presumably the most desirable therapeutic agents due to their unmatched substrate specificity and reaction efficiency. Yet, clinical use of these drugs has met with limited success, primarily due to the impermeable nature of the cell membrane that restricts cellular drug uptake to only small (<600 Da) and hydrophobic molecules. The recent discovery of the protein transduction domain (PTD) membrane-penetrating peptides, such as HIV-TAT, has finally offered the possibility of resolving this cell-membrane barrier for macromolecular drug delivery. Via covalent linkages, these PTD peptides have been shown to ferry the attached macromolecular species across membranes of all cell types, both in vitro and in vivo. Nevertheless, the lack of selectivity for PTD-mediated internalization restricts the application of this cell uptake method in clinical practice, due to concerns of inducing systemic toxicity caused by the carried drugs. Presented herein is a modified version of our previously established "ATTEMPTS" approach in delivery of macromolecular drugs, which integrates the cell-penetrating PTDs into a heparin/protamine-regulated delivery system. In vitro findings using asparaginase (ASNase) as a model macromolecular anti-tumor agent were able to validate the feasibility of this delivery system. The chemically constructed TAT-ASNase conjugates not only were able to translocate into the MOLT-4 cells and elicit the cytotoxic effects, but also this PTD-mediated intracellular drug uptake could be regulated (with on/off control) by the addition of heparin and protamine. This modified ATTEMPTS system therefore presents a new avenue of treatment of various types of cancers and other diseases with macromolecular drugs. In vitro characterization and a preliminary proof-of-concept animal investigation that demonstrates the feasibility of this PTD-mediated ASNase therapeutic system is subsequently described.

Antisense oligodeoxynucleotide-conjugated hyaluronic acid/protamine nanocomplexes for intracellular gene inhibition

Green fluorescent protein (GFP) antisense oligodeoxynucleotide (ODN) was covalently conjugated to hyaluronic acid (HA) via a reducible disulfide linkage, and the HA-ODN conjugate was complexed with protamine to increase the extent of cellular uptake and enhance the gene inhibition efficiency of GFP expression. The HA-ODN conjugate formed more stable polyelectrolyte complexes with protamine as compared to naked ODN, probably because of its increased charge density. The higher cellular uptake of protamine/HA-ODN complexes than that of protamine/naked ODN complexes was attributed to the formation of more compact nanosized complexes (approximately 200 nm in diameter) in aqueous solution. Protamine/HA-ODN complexes also showed a comparable level of GFP gene inhibition to that of cytotoxic polyethylenimine (PEI)/ODN complexes. Since both HA and protamine are naturally occurring biocompatible materials, the current formulation based on a cleavable conjugation strategy of ODN to HA could be potentially applied as safe and effective nonviral carriers for ODN and siRNA nucleic acid therapeutics.

Recent advances in delivery systems for anti-HIV1 therapy

In the last years, different non-biological and biological carrier systems have been developed for anti-HIV1 therapy. Liposomes are excellent potential anti-HIV1 carriers that have been tested with drugs, antisense oligonucleotides, ribozymes and therapeutic genes. Nanoparticles and low-density lipoproteins (LDLs) are cell-specific transporters of drugs against macrophage-specific infections such as HIV1. Through a process of protein transduction, cell-permeable peptides of natural origin or designed artificially allow the delivery of drugs and genetic material inside the cell. Erythrocyte ghosts and bacterial ghosts are a promising delivery system for therapeutic peptides and HIV vaccines. Of interest are the advances made in the field of HIV gene therapy by the use of autologous haematopoietic stem cells and viral vectors for HIV vaccines. Although important milestones have been reached in the development of carrier systems for the treatment of HIV, especially in the field of gene therapy, further clinical trials are required so that the efficiency and safety of these new systems can be guaranteed in HIV patients.

Immunostimulatory properties of CpG-oligonucleotides are enhanced by the use of protamine nanoparticles

The aim of this paper was to investigate if the immunostimulatory effects of CpG-oligonucleotides (CpG-ODN) can be enhanced by the use of biodegradable protamine nanoparticles (proticles). We analyzed size, surface charge, and morphology of protamine nanoparticles containing CpG-ODN with photon correlation spectroscopy and transmission electron microscopy. Immunostimulatory effects of these nanoparticles on B cells, plasmacytoid dendritic cells (PDC), peripheral blood mononuclear cells, and whole blood were studied. Cytokine production, activation of the cells in terms of upregulation of surface molecules and uptake of nanoparticles were examined. We found that the use of protamine nanoparticles significantly increased (20-fold) CpG-ODN mediated interferon (IFN)-alpha production of PDC. ODN uptake in PDC was only marginally enhanced. CpG-ODN mediated IP-10 production in whole blood was strongly enhanced by the use of nanoparticles. Apart from a slight increase in CpG-ODN-induced interleukin (IL)-6 production in B cells, other parameters like the CpG-mediated activation of B cells and PDC as well as tumor necrosis factor (TNF)-alpha production of PDC remained largely unchanged. The use of control ODN indicated that the protamine nanoparticles themselves have no immunostimulatory properties. These results strongly support the use of particulate delivery systems like biodegradable protamine nanoparticles for the development of CpG-ODN-based therapeutics.

Efficient delivery of a Bcl-2-specific antisense oligodeoxyribonucleotide (G3139) via transferrin receptor-targeted liposomes

A novel transferrin receptor (TfR)-targeted liposomal formulation was synthesized and evaluated for the delivery of a phosphorothioate antisense oligodeoxyribonucleotide (ODN) (G3139, oblimerson sodium, or Genasense) to Bcl-2 in K562 leukemia cells. Liposomes composed of DC-Chol/egg PC/PEG-DSPE (25:73.5:1.5, mol/mol/mol) were loaded with G3139 with high efficiency (70-80%). To prepare targeted liposomes, transferrin was first coupled to PEG-DSPE and then incorporated into the bilayer by post-insertion. The liposomes had a mean diameter of 100 to 150 nm and exhibited colloidal stability for up to 8 weeks. Uptake of Tf-conjugated G3139-containing liposomes in TfR positive K562 cells was found to be more efficient than that of the non-targeted control formulation and could be blocked by excess free Tf. Treatment with Tf-conjugated liposomes resulted in Bcl-2 protein downregulation in K562 cells that was approximately 2-fold greater than with non-targeted liposomes (p<0.05) and 10-fold greater than with free G3139. Treatment with 2 microM G3139 in Tf-conjugated liposomes resulted in >80% reduction in Bcl-2 transcript. In addition, Tf-conjugated liposomal G3139-sensitized K562 cells to daunorubicin, lowering IC50 from 1.8 microM to 0.18 microM. In conclusion, Tf-conjugated liposomes are effective delivery vehicles for G3139 antisense oligos in TfR positive K562 cells and warrant further investigation as an in vivo oligo delivery vehicle.

Oligonucleotide-protamine-albumin nanoparticles: Protamine sulfate causes drastic size reduction

Nanoparticles prepared by self-assembly from oligonucleotides (ONs), protamine free base, and human serum albumin ("ternary proticles") are spheres of diameters around 200 nm. Substitution of the protamine free base by protamine sulfate leads to proticles of only around 40 nm in diameter with otherwise unchanged properties. The availability of drug delivery systems of very similar composition but grossly different size may be advantageous when dealing with cells which show size-dependent particle uptake. These nanoparticles are promising candidates for ON delivery to cells because of the following reasons: (1) They are stable for several hours in solutions of up to physiological ionic strength; (2) they are efficiently taken up by cells; (3) after cellular uptake, they easily release the ONs even when these are present as phosphorothioates.

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

In the present study, cationic lipid-peptide-DNA-complexes (LPDs) consisting of AH-Chol-liposomes and protamine-phosphodiester-oligonucleotide-particles (proticles) were introduced as carriers for antisense therapy. The LPDs were physically characterized, and a possible mechanism for adsorption of oligonucleotides (ODNs) was suggested. An increase in stability of ODNs against DNase I and serum nuclease digestion by these carriers was demonstrated. The hydrodynamic diameter increased after incubation with FCS which could be attributed to a protein coating of the particle surface. However, in cell culture medium lower particle sizes of the complexes occurred. In an antisense c-myc in vitro model, the effect of LPDs was tested using U937 cells. The C-MYC level was reduced after treatment of these antisense ODN carrier complexes. Furthermore, no changes in target mRNA concentration of the treated cells was found by reverse transcription and competitive multiplex-PCR.

Albumin-protamine-oligonucleotide-nanoparticles as a new antisense delivery system. Part 2: cellular uptake and effect

Antisense oligonucleotides have been used as a specific tool to inhibit the expression of disease associated genes for many years. Unfortunately, oligonucleotides are polyanionic macromolecules which have a weak permeability through biological membranes and are rapidly degraded by nucleases. The purpose of this work is to characterise a new drug delivery system developed by [V. Vogel, D.Lochmann, J. Weyermann, G. Mayer, C. Tziatios, J.A. van der Brock, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which allows an increased cellular uptake and an intracellular dissociation of the oligonucleotides. The new system based on nanoparticles (NPs) consists of human serum albumin, protamine sulphate and antisense-oligonucleotides (AlPrO). We tested these new nanoparticles on mouse fibroblasts which were stably transfected with a N-methyl-D-aspartate (NMDA) receptor (NR). This cell line enabled us to perform in vitro studies of cellular uptake, intracellular dissociation and effect of the antisense-oligonucleotide in a simple excitotoxicity model. We compared our findings with free oligonucleotides and a commercial available liposomal preparation (DOTAP). We found a 12-fold increased cellular uptake of oligonucleotides in comparison to free oligonucleotides while 100% of the cells were transfected. The AlPrO-NPs showed very low cytotoxic side effects during a 24 h application. We saw an antisense effect of about 35% in a functional assay as well as on the protein level (western blot). The results of the cell penetration and the antisense assay demonstrated that AlPrO nanoparticles are promising carriers for oligonucleotide administration.

Albumin-protamine-oligonucleotide nanoparticles as a new antisense delivery system. Part 1: physicochemical characterization

In this paper, a ternary system of albumin-protamine-oligonucleotide nanoparticles (AlPrO-NP) recently developed by Vogel et al. [V. Vogel, D. Lochmann, J. Weyermann, G. Mayer, C. Tziatzios, J.A. van den Broek, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which could serve as a potential drug delivery system for antisense oligonucleotides. Former studies of binary protamine-oligonucleotide nanoparticles showed two main disadvantages: (i) aggregation of the particles within a few minutes in the presence of salt; (ii) low intracellular dissociation between protamine and oligonucleotide, especially phosphorothioates. To overcome these problems, human serum albumin (HSA) as a non-toxic, biodegradable macromolecule was introduced as protective colloid. The assembly process of AlPrO-NP was investigated by small angle X-ray scattering (SAXS), fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS) measurements and scanning electron microscopy (SEM). 'Initial complexes' of HSA and protamine sulphate with a mean hydrodynamic diameter (dh) of about 10-14 nm were found. After adding oligonucleotides (unmodified, phosphorothioate DNA and small interfering RNA), nanoparticles (NPs) were assembled in water and in isotonic media with a dh in a range of 230-320 nm for most preparations. The chemical composition of the particles was investigated by high performance liquid chromatography and fluorescence spectrometry. The whole amount of oligonucleotides (30 microg) was entrapped into the particles at a 1:2 mass ratio (oligonucleotide/protamine). Approximately 7-10% (w/w) of the HSA was bound to the particles. The surface charge of the particles ranged from about +12 to -60 mV depending on the protamine concentration and the ionic conditions. The size and the molecular weight of the components, initial complexes and two model NP preparations were calculated from FCS data. These data verified the PCS, SEM and SAXS measurements.

Drug delivery of oligonucleotides by peptides

Oligonucleotides are promising tools for in vitro studies where specific downregulation of proteins is required. In addition, antisense oligonucleotides have been studied in vivo and have entered clinical trials as new chemical entities with various therapeutic targets such as antiviral drugs or for tumour treatments. The formulation of these substances were widely studied in the past. With this review we will focus on peptides used as drug delivery vehicles for oligonucleotides. Different strategies are summarised. Cationically charged peptides from different origins were used e.g. as cellular penetration enhancers or nuclear localisation tool. Examples are given for Poly-L-lysine alone or in combination with receptor specific targeting ligands such as asialoglycoprotein, galactose, growth factors or transferrin. Another large group of peptides are those with membrane translocating properties. Fusogenic peptides rich in lysine or arginine are reviewed. They have been used for DNA complexation and condensation to form transport vehicles. Some of them, additionally, have so called nuclear localisation properties. Here, DNA sequences, which facilitate intracellular trafficking of macromolecules to the nucleus were explored. Summarizing the present literature, peptides are interesting pharmaceutical excipients and it seems to be feasible to combine the specific properties of peptides to improve drug delivery devices for oligonucleotides in the future.

Comparison of antisense oligonucleotide drug delivery systems

Antisense oligonucleotides (AS-ONs) are specific drugs to inhibit gene expression at the transcriptional level. They possess a poor bioavailability and can be degraded by nucleases very rapidly. Therefore, a strong need for the development of oligonucleotide drug delivery systems exists. In the present study, two commercially available liposomes (DOTAP, lipofectin), one artificial virus capsoid (polyoma VP1), two cationic acrylate nanoparticles and two protamine-based nanoparticle preparations (proticles) were compared. Physical parameters of all carrier systems including z-average size, size distribution and surface charge regarding were determined. Cellular uptake was measured by a microplate fluorescence quantification method and, in addition, was visualized in mouse fibroblasts by confocal laser scan microscopy (CLSM). A comparison of cytotoxicity of the different drug delivery systems was performed in vitro using a MTT assay. Mouse fibroblasts which were stable transfected with the cDNA of a N-methyl-D-aspartate (NMDA) receptor also served as functional antisense oligonucleotide test system based on excitotoxicity (cell death). In addition, the efficiency of our oligonucleotide delivery systems was compared on the level of protein expression by Western blotting. Concluding the results, an increased uptake of the ON was found (2-18-fold) for all delivery systems compared to the free ON. Protamine-based nanoparticles showed a very low cytotoxicity in contradiction to all other carrier systems. Lipofectin could be identified as the most potent delivery system in terms of antisense effect, followed by protamine nanoparticles and DOTAP. Sequence-specific antisense effects up to 80% were observed in the functional cell death assay. The highest reduction of NMDA expression was obtained from liposomal preparations with approximately 60% analyzed by Western blot.

Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties, and intracellular distribution

Oligodesoxynucleotides (ODNs) or the corresponding phosphorothioates (PTOs) spontaneously form spherical nanoparticles ("proticles") with protamine in aqueous solutions. The proticles can cross cellular membranes and release the ODNs within the cells. Thus, they represent a potential drug delivery system. The major disadvantages of this system are a lack of stability in salt solutions and its inability to also release PTOs. The present study shows, using PTOs and protamine free base, that these shortcomings can be eliminated by the addition of human serum albumin (HSA) as a third component to the starting mixture. The "ternary" proticles thus obtained contain maximally a few percent of the HSA that was originally present. Nevertheless, they differ from the previously studied "binary" proticles: (1) They are stable in salt solutions for at least several hours. (2) They show a high cellular uptake into murine fibroblasts, and they readily release the PTOs after uptake. The ternary proticles therefore represent a considerable improvement over binary proticles for use as drug delivery systems.