Octaarginine-modified multifunctional envelope-type nanoparticles for gene delivery

Neutralized nanoparticle composed of SS-cleavable and pH-activated lipid-like material as a long-lasting and liver-specific gene delivery system

Charge-neutralized lipid envelope-type nanoparticles formed with SS-cleavable and pH-activated lipid-like materials (ssPalm) accumulate rapidly in the liver without forming aggregates in the blood circulation, and result in a liver-specific gene expression for a long duration (>2 weeks) with neither immunological responses nor hepatotoxicity after intraveneous administration, when it carries pDNA free from CpG-motifs.

Octaarginine-modified liposomes enhance cross-presentation by promoting the C-terminal trimming of antigen peptide

Exogenous antigen proteolysis by proteasomes and amino peptidases is essential for the production of mature major histocompatibility complex class I (MHC-I) peptides to induce cross-presentation. We report here that when liposomes are modified with octaarginine (R8-Lip), a type of cell-penetrating peptide, the production of the mature MHC-I peptide is enhanced by promoting the C-terminal trimming of the antigen peptide. The efficiency of cross-presentation of ovalbumin (OVA) using the R8-Lip was dramatically higher than that by octalysine modified liposomes (K8-Lip) in mouse bone-marrow derived dendritic cells (BMDCs), although the physical characters of both liposomes were comparable. In this study, we investigated the mechanism responsible for the enhancement in cross-presentation by R8-Lip. Although the efficiencies of cellular uptake, endosomal escape, proteolysis of OVA and DC maturation between the two systems were essentially the same, an analysis of peptide trimming to SIINFEKL (mature MHC-I peptide of OVA) by using R8-Lip and K8-Lip encapsulating peptides of various length clearly indicates that the use of R8-Lip enhances the efficiency of the C-terminal cleavage of antigen-derived peptides. This finding provides a new strategy for achieving efficient cross-presentation by using R8 peptide and arginine-rich peptides. Moreover, this result may contribute to the development of a new paradigm regarding the machinery associated with antigen peptide production.

A novel nonviral gene delivery system: multifunctional envelope-type nano device

In this review we introduce a new concept for developing a nonviral gene delivery system which we call "Programmed Packaging." Based on this concept, we succeeded in developing a multifunctional envelope-type nano device (MEND), which exerts high transfection activities equivalent to those of an adenovirus in a dividing cell. The use of MEND has been extended to in vivo applications. PEG/peptide/DOPE ternary conjugate (PPD)-MEND, a new in vivo gene delivery system for the targeting of tumor cells that dissociates surface-modified PEG in tumor tissue by matrix metalloproteinase (MMP) and exerts significant transfection activities, was developed. In parallel with the development of MEND, a quantitative gene delivery system, Confocal Image-assisted 3-dimensionally integrated quantification (CIDIQ), also was developed. This method identified the rate-limiting step of the nonviral gene delivery system by comparing it with adenoviral-mediated gene delivery. The results of this analysis provide a new direction for the development of rational nonviral gene delivery systems.

Liposomes physically coated with peptides: preparation and characterization

Physically coating liposomes with peptides of desirable functions is an economic, versatile, and less time-consuming approach to prepare drug delivery vehicles. In this work, we designed three peptides-Ac-WWKKKGGNNN-NH2 (W2K3), Ac-WWRRRGGNNN-NH2(W2R3), Ac-WWGGGGGNNN-NH2(W2G3)-and studied their coating ability on negatively charged liposomes. It was found that the coating was mainly driven by the electrostatic interaction between the peptides' cationic side groups and the acidic lipids, which also mediated the "anchoring " of Trp residuals in the interfacial region of lipid bilayers. At the same conditions, the amount of the coated W2R3 was more than that of W2K3, but the stability of the liposome coated with W2R3 was deteriorated. This was caused by the delocalized charge of the guanidinium group of arginine. The coating of the peptide rendered the liposome pH-responsive behavior but did not prominently change the phase transition temperature. The liposome coated with peptides displayed appropriate pH/temperature dual responsive characteristics and was able to release the content in a controlled manner.

A nanocarrier system for the delivery of nucleic acids targeted to a pancreatic beta cell line

Pancreatic β cells secrete insulin in response to glucose levels and thus are involved in controlling blood glucose levels. A line of pancreatic β cells "MIN6" has been used in studies related to the function of β cells and diabetes therapy. Regulating gene expression in MIN6 cells could accelerate these studies, but an efficient method for the transfection of nucleic acids targeted to MIN6 cells is required. We report here on a liposome-based carrier targeted to pancreatic β cells (Multifunctional envelope-type nano device for pancreatic β cells, β-MEND). We identified a lipid composition for use in preparing the β-MEND, which permits the particles to be efficiently internalized into MIN6, as evidenced by flow cytometry analyses. Intracellular observation by confocal laser scanning microscopy showed that the β-MEND efficiently delivered the oligo nucleic acids to the cytosol of MIN6 cells. Moreover, using a β-MEND encapsulating a 2'-O-Methyl RNA complementary to a microRNA that suppresses insulin secretion, the knockdown of the targeted microRNA and an up-regulation of insulin secretion were observed in MIN6. Thus, the β-MEND holds promise as an efficient system for delivering nucleic acids targeted to MIN6 and can contribute to research and therapy aimed at diabetes.

Nanopreparations for organelle-specific delivery in cancer

To efficiently deliver therapeutics into cancer cells, a number of strategies have been recently investigated. The toxicity associated with the administration of chemotherapeutic drugs due to their random interactions throughout the body necessitates the development of drug-encapsulating nanopreparations that significantly mask, or reduce, the toxic side effects of the drugs. In addition to reduced side effects associated with drug encapsulation, nanocarriers preferentially accumulate in tumors as a result of its abnormally leaky vasculature via the Enhanced Permeability and Retention (EPR) effect. However, simple passive nanocarrier delivery to the tumor site is unlikely to be enough to elicit a maximum therapeutic response as the drug-loaded carriers must reach the intracellular target sites. Therefore, efficient translocation of the nanocarrier through the cell membrane is necessary for cytosolic delivery of the cargo. However, crossing the cell membrane barrier and reaching cytosol might still not be enough for achieving maximum therapeutic benefit, which necessitates the delivery of drugs directly to intracellular targets, such as bringing pro-apoptotic drugs to mitochondria, nucleic acid therapeutics to nuclei, and lysosomal enzymes to defective lysosomes. In this review, we discuss the strategies developed for tumor targeting, cytosolic delivery via cell membrane translocation, and finally organelle-specific targeting, which may be applied for developing highly efficacious, truly multifunctional, cancer-targeted nanopreparations.

Threaded macromolecules as a versatile framework for biomaterials

In this feature article, the recent progress in biomaterial application of threaded macromolecules including polyrotaxanes such as drug delivery and gene delivery is described.

A method for screening mitochondrial fusogenic envelopes for use in mitochondrial drug delivery

Various types of mitochondrial dysfunctions have been implicated in a variety of human diseases. This suggests that mitochondria would be promising therapeutic drug targets and mitochondrial therapy would be expected to be useful for the treatment of various diseases. We have already reported the development of a MITO-Porter, a liposome-based nano-carrier that delivers its cargo to mitochondria via a membrane-fusion mechanism. In our strategy for delivering cargos to mitochondria using a MITO-Porter, the carriers must fuse with the organelle membrane. Here we report on methodology for screening various types of lipid envelopes that have the potential for fusing with a mitochondrial membrane. The method involves monitoring the cancellation of fluorescence resonance energy transfer (FRET) and evaluating membrane fusion between the carriers and mitochondria in living cells by FRET analysis using a spectral imaging fluorescent microscopy system.

Investigation of siRNA Nanoparticle Formation Using Mono-Cationic Detergents and Its Use in Gene Silencing in Human HeLa Cells

The focus of recent research has been on the development of siRNA vectors to achieve an innovative gene therapy. Most of the conventional vectors are siRNA nanoparticles complexed with cationic polymers and liposomes, making it difficult to release siRNA. In this study, we report on the use of MCD, a quaternary ammonium salt detergent containing a long aliphatic chain (L-chain) as an siRNA complexation agent using human HeLa cells (a model cancer cell). We prepared siRNA nanoparticles using various MCDs, and measured the diameters and zeta-potentials of the particles. The use of an MCD with a long L-chain resulted in the formation of a positively charged nanoparticle. In contrast, a negatively charged nanoparticle was formed when a MCD with a short L-chain was used. We next evaluated the gene silencing efficiency of the nanoparticles using HeLa cells expressing the luciferase protein. The results showed that the siRNA/MCD nanoparticles showed a higher gene silencing efficiency than Lipofectamine 2000. We also found that the efficiency of gene silencing is a function of the length of the alkyl chain in MCD and zeta-potential of the siRNA/MCD nanoparticles. Such information provides another viewpoint for designing siRNA vectors.

Cell-penetrating peptides (CPPs) as a vector for the delivery of siRNAs into cells

"Cell-penetrating peptides (CPPs)" is an inclusive term describing relatively small peptides (6-30 amino acid residues) having membrane translocation activity. Due to their efficacy in cellular internalisation and the accompanying low cytotoxicity, CPPs are regarded as promising vectors for intracellular delivery of various membrane-impermeable bioactive molecules. This review provides an overview of the current approaches and describes the potential of CPP-based siRNA delivery systems, specifically those using arginine-rich CPPs.

Merging the best of both worlds: hybrid lipid-enveloped matrix nanocomposites in drug delivery

The advent of nanotechnology has revolutionized drug delivery in terms of improving drug efficacy and safety. Both polymer-based and lipid-based drug-loaded nanocarriers have demonstrated clinical benefit to date. However, to address the multifaceted drug delivery challenges ahead and further expand the spectrum of therapeutic applications, hybrid lipid-polymer nanocomposites have been designed to merge the beneficial features of both polymeric drug delivery systems and liposomes in a single nanocarrier. This review focuses on different classes of nanohybrids characterized by a drug-loaded polymeric matrix core enclosed in a lipid shell. Various nanoengineering approaches to obtain lipid-polymer nanocomposites with a core-shell nanoarchitecture will be discussed as well as their predominant applications in drug delivery.

Strategies on the nuclear-targeted delivery of genes

To improve the nuclear-targeted delivery of non-viral vectors, extensive effort has been carried out on the development of smart vectors which could overcome multiple barriers. The nuclear envelope presents a major barrier to transgene delivery. Viruses are capable of crossing the nuclear envelope to efficiently deliver their genome into the nucleus through the specialized protein components. However, non-viral vectors are preferred over viral ones because of the safety concerns associated with the latter. Non-viral delivery systems have been designed to include various types of components to enable nuclear translocation at the periphery of the nucleus. This review summarizes the progress of research regarding nuclear transport mechanisms. "Smart" non-viral vectors that have been modified by peptides and other small molecules are able to facilitate the nuclear translocation and enhance the efficacy of gene expression. The resulting technology may also enhance delivery of other macromolecules to the nucleus.

A highly efficient synthetic vector: nonhydrodynamic delivery of DNA to hepatocyte nuclei in vivo

Multifunctional membrane-core nanoparticles, composed of calcium phosphate cores, arginine-rich peptides, cationic and PEGylated lipid membranes, and galactose targeting ligands, have been developed as synthetic vectors for efficient nuclear delivery of plasmid DNA and subsequent gene expression in hepatocytes in vivo. Targeted particles exhibited rapid and extensive hepatic accumulation and were predominantly internalized by hepatocytes, while the inclusion of such peptides in LCP was sufficient to elicit high degrees of nuclear translocation of plasmid DNA. Monocyclic CR8C significantly enhanced in vivo gene expression over 10-fold more than linear CR8C, likely due to a release-favoring mechanism of the DNA/peptide complex. Though 100-fold lower in activity than that achieved via hydrodynamic injection, this formulation presents as a much less invasive alternative. To our knowledge, this is the most effective synthetic vector for liver gene transfer.

An approach to transgene expression in liver endothelial cells using a liposome-based gene vector coated with hyaluronic acid

Dysfunctional sinusoidal liver endothelial cells (LECs) are associated with liver diseases, such as liver fibrosis, cirrhosis, and portal hypertension. Because of this, gene therapy targeted to LECs would be a useful and productive strategy for directly treating these diseases at the level of genes. Here, we report on the development of a transgene vector that specifically targets LECs. The vector is a liposome-based gene vector coated with hyaluronic acid (HA). HA is a natural ligand for LECs and confers desirable properties on particles, rendering them biodegradable, biocompatible, and nonimmunogenic. In this study, we constructed HA-modified carriers, and evaluated cellular uptake and transfection activity using cultured LECs from KSN nude mice (KSN-LECs). Cellular uptake analyses showed that KSN-LECs recognized the HA-modified carriers more effectively than skin endothelial cells. The transfection assay indicated that the efficient gene expression in KSN-LECs, using the HA-modified carriers, required an adequate lipid composition and a functional device to control intracellular trafficking. This finding contributes to our overall knowledge of transgene expression targeted to LECs.

Octa-arginine-modified pegylated liposomal doxorubicin: an effective treatment strategy for non-small cell lung cancer

The present study aims to evaluate the efficacy of octa-arginine (R8)-modified pegylated liposomal doxorubicin (R8-PLD) for the treatment of non-small cell lung cancer, for which the primary treatment modality currently consists of surgery and radiotherapy. Cell-penetrating peptide R8 modification of Doxorubicin-(Dox)-loaded liposomes was performed by post-insertion of an R8-conjugated amphiphilic PEG-PE copolymer (R8-PEG-DOPE) into the liposomal lipid bilayer. In vitro analysis with the non-small cell lung cancer cell line, A549 confirmed the efficient cellular accumulation of Dox, delivered by R8-PLD compared to PLD. It led to the early initiation of apoptosis and a 9-fold higher level of the apoptotic regulator, caspase 3/7 (9.24±0.34) compared to PLD (1.07±0.19) at Dox concentration of 100 μg/mL. The treatment of A549 monolayers with R8-PLD increased the level of cell death marker lactate dehydrogenase (LDH) secretion (1.2±0.1 for PLD and 2.3±0.1 for R8-PLD at Dox concentration of 100 μg/mL) confirming higher cytotoxicity of R8-PLD than PLD, which was ineffective under the same treatment regimen (cell viability 90±6% in PLD vs. 45±2% in R8-PLD after 24h). R8-PLD had significantly higher penetration into the hypoxic A549 tumor spheroids compared to PLD. R8-PLD induced greater level of apoptosis to A549 tumor xenograft and dramatic inhibition of tumor volume and tumor weight reduction. The R8-PLD treated tumor lysate had a elevated caspase 3/7 expression than with R8-PLD treatment. This suggested system improved the delivery efficiency of Dox in selected model of cancer which supports the potential usefulness of R8-PLD in cancer treatment, lung cancer in particular.

Nanomaterials as Non-viral siRNA Delivery Agents for Cancer Therapy

Gene therapy has been recently shown as a promising tool for cancer treatment as nanotechnology-based safe and effective delivery methods are developed. Generally, genes are wrapped up in extremely tiny nanoparticles which could be taken up easily by cancer cells, not to their healthy neighboring cells. Several nanoparticle systems have been investigated primarily to address the problems involved in other methods of gene delivery and observed improved anticancer efficacy suggesting that nanomedicine provides novel opportunities to safely deliver genes, thus treat cancer. In this review, various nanoparticle types and related strategies, used in gene delivery for cancer treatment, have been discussed.

Bacillus Calmette-Guerin (BCG) immunotherapy for bladder cancer: current understanding and perspectives on engineered BCG vaccine

Since the first report in 1976, accumulated clinical evidence has supported intravesical Bacillus Calmette-Guerin (BCG) therapy as one of the standard methods of management of intermediate- and high-risk non-muscle invasive bladder cancer. Despite its efficacy, intravesical BCG therapy is associated with a variety of adverse events (AEs), most of which are tolerable or controllable with supportive care. However, some patients receiving intravesical BCG therapy may experience uncommon but severe AEs, leading to cessation of BCG therapy. Not all, but most severe AEs result from either local or systemic infection with live BCG. Intravesical instillation of BCG elicits multiple immune reactions, although the precise immunological mechanism of BCG therapy is not clear. It is convenient to separate the complex reactions into the following three categories: infection of urothelial cells or bladder cancer cells, induction of immune reactions, and induction of antitumor effects. Recently, our knowledge about each category has increased. Based on this understanding, predictors of the efficacy of intravesical BCG therapy, such as urinary cytokine measurement and cytokine gene polymorphism, have been investigated. Recently, preclinical studies using a novel engineered mycobacterium vaccine have been conducted to overcome the limitations of BCG therapy. One approach is Th1 cytokine-expressing recombinant forms of BCG; another approach is development of non-live bacterial agents to avoid AEs due to live BCG infection. We also briefly describe our approach using an octaarginine-modified liposome-incorporating BCG cell wall component to develop future substitutes for live BCG.

Therapeutic delivery using cell-penetrating peptides

Intracellular delivery of promising therapeutic agents as well as nanocarriers presents a unique challenge. However, with the discovery of the cell-penetrating peptides (CPPs), overcoming this obstacle seems more plausible. In many cases, CPPs conjugated with therapeutic agent or therapeutic agent loaded-nanoparticles have shown promising results via increased cellular uptake. In this review, the current status of CPPs for the intracellular delivery of not just potential therapeutic small molecules but also large molecules like peptides, nucleic acids and nanocarriers is discussed. In addition, the design of ‘smart stimuli-sensitive nanocarrier’ to overcome the non-target-specificity of CPPs is also described.

Recent advances in the rational design of silica-based nanoparticles for gene therapy

Gene therapy has attracted much attention in modern society and provides a promising approach for treating genetic disorders, diseases and cancers. Safe and effective vectors are vital tools to deliver genetic molecules to cells. This review summarizes recent advances in the rational design of silica-based nanoparticles and their applications in gene therapy. An overview of different types of genetic agents available for gene therapy is provided. The engineering of various silica nanoparticles is described, which can be used as versatile complexation tools for genetic agents and advanced gene therapy. Several challenges are raised and future research directions in the area of gene therapy using silica-based nanoparticles are proposed.

A multifunctional envelope-type nanodevice for use in nanomedicine: concept and applications

In the 21st century, drug development has shifted toward larger molecules such as proteins and nucleic acids, which require the use of new chemical strategies. In this process, the drug delivery system plays a central role and intracellular targeting using nanotechnology has become a key technology for the development of successful new medicines. We have developed a new delivery system, a multifunctional envelope-type nanodevice (MEND) based on "Programmed Packaging." In this new concept of packaging, multifunctional nanodevices are integrated into a nanocarrier system according to a program designed to overcome all barriers during the course of biodistribution and intracellular trafficking. In this Account, we introduce our method for delivering nucleic acids or proteins to intracellular sites of action such as the cytosol, nucleus, and mitochondria and for targeting selective tissues in vivo via systemic administration of the nanodevices. First, we introduce an octaarginine-modified MEND (R8-MEND) as an efficient intracellular delivery system, designed especially for vaccinations and transgene expression. Many types of cells can internalize the R8-MEND, mainly by inducing macropinocytosis, and the MEND escapes from macropinosomes via membrane fusion, which leads to efficient antigen presentation via the major histocompatibility complex I pathway in antigen-presenting cells. In addition, the transfection activities of the R8-MEND in dividing cells, such as HeLa or A549 cells, are as high as those for adenovirus. However, because the R8-MEND cannot induce sufficient transgene activity in primary cultured dendritic cells, which are critical regulators of the immune response, we converted the R8-MEND into a tetralamellar MEND (T-MEND). The T-MEND uses a new packaging method and delivers condensed pDNA into the nucleus via fusion between the envelopes and the nuclear membrane. To achieve efficient transfection activity, we also optimized the decondensation of nucleic acids within the nucleus. To optimize mitochondrial drug delivery, we introduced the MITOPorter. Many types of materials can be packaged into this liposome-based nanocarrier and then delivered to mitochondria via membrane fusion mechanisms. Finally, we describe an integrated strategy for in vivo tumor delivery and optimization of intracellular trafficking. Successful tumor delivery typically requires coating the surfaces of nanoparticles with PEG, but PEG can also limit uptake by the reticuloendothelial system and reduce the efficiency of intracellular trafficking. Here we integrate the optimum biodistribution and intracellular trafficking of the MEND with an innovative strategy such as enzymatically cleavable PEG and a short membrane peptide, GALA. Some of these strategies will soon be tested in the clinic.

Efficient intracellular delivery of nucleic acid pharmaceuticals using cell-penetrating peptides

Over the last 20 years, researchers have designed or discovered peptides that can permeate membranes and deliver exogenous molecules inside a cell. These peptides, known as cell-penetrating peptides (CPPs), typically consist of 6-30 residues, including HIV TAT peptide, penetratin, oligoarginine, transportan, and TP10. Through chemical conjugation or noncovalent complex formation, these structures successfully deliver bioactive and membrane-impermeable molecules into cells. CPPs have also gained attention as an attractive vehicle for the delivery of nucleic acid pharmaceuticals (NAPs), including genes/plasmids, short oligonucleotides, and small interference RNAs and their analogues, due to their high internalization efficacy, low cytotoxicity, and flexible structural design. In this Account, we survey the potential of CPPs for the design and optimization of NAP delivery systems. First, we describe the impact of the N-terminal stearylation of CPPs. Endocytic pathways make a major contribution to the cellular uptake of NAPs. Stearylation at the N-terminus of CPPs with stearyl-octaarginine (R8), stearyl-(RxR)(4), and stearyl-TP10 prompts the formation of a self-assembled core-shell nanoparticle with NAPs, a compact structure that promotes cellular uptake. Researchers have designed modifications such as the addition of trifluoromethylquinoline moieties to lysine residues to destabilize endosomes, as exemplified by PepFect 6, and these changes further improve biological responsiveness. Alternatively, stearylation also allows implantation of CPPs onto the surface of liposomes. This feature facilitates "programmed packaging" to establish multifunctional envelope-type nanodevices (MEND). The R8-MEND showed high transfection efficiency comparable to that of adenovirus in non-dividing cells. Understanding the cellular uptake mechanisms of CPPs will further improve CPP-mediated NAP delivery. The cellular uptake of CPPs and their NAP complex involves various types of endocytosis. Macropinocytosis, a mechanism which is also activated in response to stimuli such as growth factors or viruses, is a primary pathway for arginine-rich CPPs because high cationic charge density promotes this endocytic pathway. The use of larger endosomes (known as macropinosomes) rather than clathrin- or caveolae-mediated endocytosis has been reported in macropinocytosis which would also facilitate the endocytosis of NAP nanoparticles into cells.

Bleomycin in octaarginine-modified fusogenic liposomes results in improved tumor growth inhibition

Bleomycin (BLM) is an example of an anticancer drug that should be delivered into cytosol for its efficient therapeutic action. With this in mind, we developed octaarginine (R8)-modified fusogenic DOPE-liposomes (R8-DOPE-BLM). R8-modification dramatically increased (up to 50-fold) the cell-liposome interaction. R8-DOPE-liposomes were internalized via macropinocytosis and did not end up in the lysosomes. R8-DOPE-BLM led to a significantly stronger cell death and DNA damage in vitro relative to all controls. R8-DOPE-BLM demonstrated a prominent anticancer effect in the BALB/c mice bearing 4T1 tumors. Thus, R8-DOPE-BLM provided efficient intracellular delivery of BLM leading to strong tumor growth inhibition in vivo.

Fabrication of functionalized double-lamellar multifunctional envelope-type nanodevices using a microfluidic chip with a chaotic mixer array

Multifunctional envelope-type nanodevices (MENDs) are very promising non-viral gene delivery vectors because they are biocompatible and enable programmed packaging of various functional elements into an individual nanostructured liposome. Conventionally MENDs have been fabricated by complicated, labor-intensive, time-consuming bulk batch methods. To avoid these problems in MEND fabrication, we adopted a microfluidic chip with a chaotic mixer array on the floor of its reaction channel. The array was composed of 69 cycles of the staggered chaotic mixer with bas-relief structures. Although the reaction channel had very large Péclet numbers (>10(5)) favorable for laminar flows, its chaotic mixer array led to very small mixing lengths (<1.5 cm) and that allowed homogeneous mixing of MEND precursors in a short time. Using the microfluidic chip, we fabricated a double-lamellar MEND (D-MEND) composed of a condensed plasmid DNA core and a lipid bilayer membrane envelope as well as the D-MEND modified with trans-membrane peptide octaarginine. Our lab-on-a-chip approach was much simpler, faster, and more convenient for fabricating the MENDs, as compared with the conventional bulk batch approaches. Further, the physical properties of the on-chip-fabricated MENDs were comparable to or better than those of the bulk batch-fabricated MENDs. Our fabrication strategy using microfluidic chips with short mixing length reaction channels may provide practical ways for constructing more elegant liposome-based non-viral vectors that can effectively penetrate all membranes in cells and lead to high gene transfection efficiency.

Development of viral nanoparticles for efficient intracellular delivery

Viral nanoparticles (VNPs) based on plant viruses such as Cowpea mosaic virus (CPMV) can be used for a broad range of biomedical applications because they present a robust scaffold that allows functionalization by chemical conjugation and genetic modification, thereby offering an efficient drug delivery platform that can target specific cells and tissues. VNPs such as CPMV show natural affinity to cells; however, cellular uptake is inefficient. Here we show that chemical modification of the CPMV surface with a highly reactive, specific and UV-traceable hydrazone linker allows bioconjugation of polyarginine (R5) cell penetrating peptides (CPPs), which can overcome these limitations. The resulting CPMV-R5 particles were taken up into a human cervical cancer cell line (HeLa) more efficiently than native particles. Uptake efficiency was dependent on the density of R5 peptides on the surface of the VNP; particles displaying 40 R5 peptides per CPMV (denoted as CPMV-R5H) interact strongly with the plasma membrane and are taken up into the cells via an energy-dependent mechanism whereas particles displaying 10 R5 peptides per CPMV (CPMV-R5L) are only slowly taken up. The fate of CPMV-R5 versus native CPMV particles within cells was evaluated in a co-localization time course study. It was indicated that the intracellular localization of CPMV-R5 and CPMV differs; CPMV remains trapped in Lamp-1 positive endolysosomes over long time frames; in contrast, 30-50% of the CPMV-R5 particles transitioned from the endosome into other cellular vesicles or compartments. Our data provide the groundwork for the development of efficient drug delivery formulations based on CPMV-R5.

Cell-penetrating peptides for the delivery of nucleic acids

INTRODUCTION

Different gene therapy approaches have gained extensive interest lately and, after many initial hurdles, several promising approaches have reached to the clinics. Successful implementation of gene therapy is heavily relying on finding efficient measures to deliver genetic material to cells. Recently, non-viral delivery of nucleic acids and their analogs has gained significant interest. Among non-viral vectors, cell-penetrating peptides (CPPs) have been extensively used for the delivery of nucleic acids both in vitro and in vivo.

AREAS COVERED

In this review we will discuss recent advances of CPP-mediated delivery of nucleic acid-based cargo, concentrating on the delivery of plasmid DNA, splice-correcting ONs, and small-interfering RNAs.

EXPERT OPINION

CPPs have proved their potential as carriers for nucleic acids. However, similarly to other non-viral vectors, CPPs require further development, as efficient systemic delivery is still seldom achieved. To achieve this, CPPs should be modified with entities that would allow better endosomal escape, targeting of specific tissues and cells, and shielding agents that increase the half-life of the vehicles. Finally, to understand the clinical potential of CPPs, they require more thorough investigations in clinically relevant disease models and in pre-clinical and clinical studies.

Uptake and intracellular fate of fluorescent-magnetic glyco-nanoparticles

Iron oxide based nanoparticles are finding their way as leading actors in nanotechnology applications to medicine. Magnetite nanoparticles are currently being used in clinics for the detection of hepatic tumors based on their unspecific accumulation in liver. More and more works are being published on potential applications of magnetic nanoparticles in diagnostics and therapy. But the interaction between magnetic nanoparticles and human cells at the subcellular level is only now beginning to be studied and more basic research is needed in this field. This work studies the interaction between carbohydrate functionalized gold-coated magnetite nanoparticles and C33 tumoural human cells as the first step towards the in vivo application of these nanoparticles. The uptake of this magnetic material follows a similar trend to that described for other nanoparticles. The intracellular fate of these nanoparticles once internalized has been unveiled, and an automatic methodology for the analysis of co-localization data has also been tested and compared to a more classic approach. These results can help in the optimization of the design of magnetic nanoparticles depending on their final application.

Post-nuclear gene delivery events for transgene expression by biocleavable polyrotaxanes

A quantitative comparison between nuclear DNA release from carriers and their transfection activity would be highly useful for improving the effectiveness of non-viral gene vectors. We previously reported that, for condensed DNA particles, a close relationship exists between the efficiency of DNA release and transfection activity, when biocleavable polyrotaxanes (DMAE-SS-PRX), in which the cationic density can be easily controlled. In this study, we first investigated the efficiencies of DNA release from condensed DNA particles with various types of DMAE-SS-PRX. The findings indicate that an optimal cationic density in DMAE-SS-PRX exists for DNA release. We then packaged condensed DNA particles in a multifunctional envelope-type nano device (MEND), and evaluated their transfection activities. The results showed that the transfection activity was increased and this increase was, to some extent, dependent on the efficiency of the DNA release. However, transfection activity decreased, when the value for the efficiency of DNA release was higher than a certain value. An investigation of the fate of intranuclear DNA indicated that a very high efficiency of DNA release has a positive influence on transcription, however, it would inhibit the post-transcription process; nuclear mRNA export, translation and related processes. Such information provides a new viewpoint for the development of cationic polymer-based vectors.

Cell-penetrating peptides as versatile vehicles for oligonucleotide delivery

Short regulatory oligonucleotides (ONs) have a great therapeutic potential for the modulation of gene expression due to their high specificity and low toxicity. The major obstacles for in vivo clinical applications of ONs are the poor permeability of plasma membrane to nucleic acids and the sensitivity of ONs to enzymatic degradation. Hence, various delivery vehicles have been developed to ensure the transduction of ONs into cells. Among these, the cell-penetrating peptides (CPPs) have gained quickly broadening popularity as promising nonviral transmembrane delivery vectors. For coupling of nucleic acids to CPPs, two distinct strategies may be applied-covalent and noncovalent. The majority of earlier studies have used covalent coupling of CPPs to ONs. However, the number of studies demonstrating very high therapeutic potential of noncovalent complexes of ONs with novel CPP-based delivery vehicles is explosively increasing. In this review, the recent developments in the application of CPP-mediated oligonucleotide delivery by noncovalent strategy will be discussed.

Cell-penetrating peptide-based systems for nucleic acid delivery: a biological and biophysical approach

The increasing knowledge on the genetic basis of disease provides a platform for the development of promising gene-targeted therapies that can be applied to numerous pathological conditions, including cancer. Such genetic-based approaches involve the use of nucleic acids as therapeutic agents, either for the insertion or for the repair and regulation of specific genes. However, despite the huge pharmacological potential of these molecules, their application remains highly dependent on the development of delivery systems capable of mediating efficient cellular uptake. The discovery of a class of small peptides, the so-called cell-penetrating peptides (CPPs), which are able to very efficiently cross cell membranes through a mechanism that is independent of membrane receptors or transporters and avoids lysosomal enzymatic degradation, has been enthusiastically considered of key interest to improve noninvasive cellular delivery of therapeutic molecules. A large number of CPPs have been applied successfully to mediate the intracellular delivery of nucleic acids, including the S4(13)PV peptide for which interactions with membranes and resulting biological effects are illustrated in this chapter. Here, we provide a description of the experimental procedures for the preparation of CPP-based nucleic acid complexes and assessment of their formation, the selection of those protocols leading to the most efficient complexes, the biophysical characterization of CPP membrane interactions, and the evaluation of the biological and cytotoxic activity of the complexes.

[Regulation and analysis of intracellular trafficking of nucleic acids based on quantitative and dynamic imaging]

In the 21st century the category of biomedicine is now expanding from low-molecular drugs to recombinant proteins, antibodies, and nucleic acids (e.q., siRNA and plasmid DNA). In this era also, development of a novel nanotechnology to control intracellular trafficking is highly desired. For a promising gene therapy, an efficient nuclear delivery vector is a minimum requirement. Quantitative and mechanism-based information on differences in transfection efficiency between viral and non-viral vectors would be highly useful to improve the effectiveness of non-viral vectors. In this review, we will summarize our recent progress in quantitative comparison and underlying mechanisms of the intracellular trafficking between adenovirus vectors and plasmid DNA (pDNA) transfected by non-viral vectors. Our analysis has revealed that poor post-nuclear delivery events, as well as the nuclear delivery process itself are key processes to focus on. Especially, less effective transcription and translation are most likely due to poor nuclear decondensation and excess electrostatic interaction between mRNA and the gene carrier, respectively. Meanwhile, we have developed a multi-functional envelope-type nano device (MEND), in which the pDNA/polycation core is encapsulated in the lipid bilayers. Based on feedback information concerning the rate-limiting processes of gene carriers, we controlled the number of lipid envelopes to enhance the decoating of encapsulated pDNA from the envelope structure. As an expanded application of this concept, we have developed a tetra-lamellar MEND (T-MEND), which is designed to overcome the endosome and nuclear membranes by step-wise membrane fusion.

Biomimetic Polymer Nanoparticles Embedding Quantum Dots

To develop new functional fluorescence probe based on semiconductor nanoparticles, such as quantum dots (QD)s, we investigated polymer particle embedding QDs and covered with artificial cell membrane-biointerface. These nanoparticles were prepared by assembling 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer as a platform and biomolecules immobilized on the surface of the nanoparticles. The fluorescence property of QDs remained after embedding in the polymer nanoparticles. The MPC polymer surface showed high resistance to non-specific cellular uptake due to the phosphorylcholine groups in the side chain. On the other hand, when cell-penetration oligopeptide, octaarginine was immobilized on the surface, they could permeate the membrane of cells effectively and good fluorescence based on QDs could be observed. Cytotoxicity and inflammation reaction was not produced by these nanoparticles even after immobilization of octapeptide. In conclusion, we could obtain stable fluorescence polymer nanoparticles covered with artificial cell membrane, which are useful as an excellent bioimaging probe and as a novel evaluation tool for biomolecular function in the target cells.

Cell penetrating peptide-mediated systemic siRNA delivery to the liver

The cell-penetrating peptide (CPP) is one of the most attractive tools for efficiently delivering biomolecules to a target organelle. Here, we describe the use of octaarginine (R8)-modified lipid nanoparticles for the efficient and targeted in vivo delivery of siRNA to the liver. In this study, SR-BI (a scavenger receptor class B, member 1) was targeted by this nanoparticle. Our results demonstrate that R8-modified lipid nanoparticles can be used for the efficient and targeted delivery of liver siRNA to induce the specific knock-down of an endogenous gene with minimum liver toxicity and immune response, and that this CPP based technology holds considerable promise for further in vivo biological applications of siRNA.

Dual function MITO-Porter, a nano carrier integrating both efficient cytoplasmic delivery and mitochondrial macromolecule delivery

Mitochondrial dysfunction is associated with a variety of human diseases including inherited mitochondrial diseases, neurodegenerative disorders, diabetes mellitus, and cancer. Effective medical therapies for mitochondrial diseases will ultimately require an optimal drug delivery system, which will likely be achieved through innovations in the nanotechnology of intracellular trafficking. To achieve efficient mitochondrial drug delivery, two independent processes, i.e., "cytoplasmic delivery through the cell membrane" and "mitochondrial delivery through the mitochondrial membrane" are required. In previous studies, we developed an octaarginine (R8) modified nano carrier for efficient cytoplasmic delivery, showing that R8-modified liposomes were internalized into cells efficiently. On the other hand, we also constructed MITO-Porter for the mitochondrial delivery of macromolecules, a liposome-based carrier that delivers cargos to mitochondria via membrane fusion. Here, we report the development of a dual function MITO-Porter (DF-MITO-Porter), based on the concept of integrating both R8-modified liposomes and MITO-Porter. We show that the DF-MITO-Porter effectively delivers exogenous macro-biomolecules into the mitochondrial matrix, and provide a demonstration of its potential use in therapies aimed at mitochondrial DNA.

An amino acid-based amphoteric liposomal delivery system for systemic administration of siRNA

We demonstrate a systematic and rational approach to create a library of natural and modified, dialkylated amino acids based upon arginine for development of an efficient small interfering RNA (siRNA) delivery system. These amino acids, designated DiLA₂ compounds, in conjunction with other components, demonstrate unique properties for assembly into monodisperse, 100-nm small liposomal particles containing siRNA. We show that DiLA₂-based liposomes undergo a pH-dependent phase transition to an inverted hexagonal phase facilitating efficient siRNA release from endosomes to the cytosol. Using an arginine-based DiLA₂, cationic liposomes were prepared that provide high in vivo siRNA delivery efficiency and are well-tolerated in both cell and animal models. DiLA₂-based liposomes demonstrate a linear dose-response with an ED₅₀ of 0.1 mg/kg against liver-specific target genes in BALB/c mice.

A multifunctional envelope type nano device (MEND) for gene delivery to tumours based on the EPR effect: a strategy for overcoming the PEG dilemma

Gene and nucleic acid therapy are expected to play a major role in the next generation of medicine. We recently developed a multifunctional envelope-type nano device (MEND) for use as a novel non-viral gene delivery system. Poly(ethylene glycol) (PEG)ylation is a useful method for achieving a longer circulation time for delivery of the MEND to a tumour via the enhanced permeability and retention (EPR) effect. However, PEGylation strongly inhibits cellular uptake and endosomal escape, which results in significant loss of activity for the delivery system. For successful gene delivery for cancer treatment, the crucial issue associated with the use of PEG, the 'PEG dilemma' must be addressed. In this review, we describe the development and applications of MEND, and discuss strategies for overcoming the PEG dilemma, based on the manipulation of intracellular trafficking of cellular uptake and endosomal release using functional devices such as specific ligands, cleavable PEG systems and endosomal fusogenic/disruptic peptides.

A peptide-based vector for efficient gene transfer in vitro and in vivo

Finding suitable nonviral delivery vehicles for nucleic acid-based therapeutics is a landmark goal in gene therapy. Cell-penetrating peptides (CPPs) are one class of delivery vectors that has been exploited for this purpose. However, since CPPs use endocytosis to enter cells, a large fraction of peptides remain trapped in endosomes. We have previously reported that stearylation of amphipathic CPPs, such as transportan 10 (TP10), dramatically increases transfection of oligonucleotides in vitro partially by promoting endosomal escape. Therefore, we aimed to evaluate whether stearyl-TP10 could be used for the delivery of plasmids as well. Our results demonstrate that stearyl-TP10 forms stable nanoparticles with plasmids that efficiently enter different cell-types in a ubiquitous manner, including primary cells, resulting in significantly higher gene expression levels than when using stearyl-Arg9 or unmodified CPPs. In fact, the transfection efficacy of stearyl-TP10 almost reached the levels of Lipofectamine 2000 (LF2000), however, without any of the observed lipofection-associated toxicities. Most importantly, stearyl-TP10/plasmid nanoparticles are nonimmunogenic, mediate efficient gene delivery in vivo, when administrated intramuscularly (i.m.) or intradermally (i.d.) without any associated toxicity in mice.

The liposome-incorporating cell wall skeleton of Mycobacterium bovis bacillus Calmette-Guéin can directly enhance the susceptibility of cancer cells to lymphokine-activated killer cells through up-regulation of natural-killer group 2, member D ligands

OBJECTIVE

• To conduct a preclinical evaluation of the ability of natural killer cells to cytolyze bladder cancer cells that were modified to show enhanced expression of natural-killer group 2, member D (NKG2D) ligands by R8-liposome-bacillus Calmette-Guéin (BCG)-cell wall skeleton (CWS) treatment.

MATERIALS AND METHODS

• The T24 cells and RT-112 cells were co-cultured with R8-liposome-BCG-CWS and BCG for 2, 4, or 6 h, and then the surface expression of NKG2D ligands was analyzed using TaqMan real-time quantitative RT-PCR. • Peripheral blood mononuclear cells were obtained with a conventional preparation kit, and then lymphokine-activated killer (LAK) cells were generated from these purified peripheral blood mononuclear cells via interleukin-2 stimulation. • The anti-tumour effect of LAK cells against untreated and R8-liposome-BCG-CWS co-cultured with cells of the human bladder cancer cell lines T24 and RT-112 was analyzed using the cytotoxic WST-8 assay method at 4 h of culture at various effector/target (E : T) ratios.

RESULTS

• Major histocompatibility complex class I-related chain B (MICB) expression was increased ≈1.5-fold on T24 cells and RT-112 cells with BCG. • UL-16-binding protein (ULBP) 1 expression was also increased ≈1.5-fold on T24 cells and RT-112 cells with BCG. R8-liposome-BCG-CWS increased the surface expression of MICB 2.2-fold on T24 cells but did not increase it significantly on RT-112 cells. • ULBP1 expression was increased ≈2.2-fold on RT-112 cells, although no differences were observed between the expression of ULBP2 and 3 with R8-liposome-BCG-CWS. • T24 cells that were co-cultured with R8-liposome-BCG-CWS showed an ≈1.3-fold increase in sensitivity to cytolysis by LAK cells at an E : T ratio of 4 and RT-112 cells showed an ≈1.4-fold increase at an E : T ratio of 2.

CONCLUSIONS

• In the present study, the induction of surface NKG2D ligands by R8-liposome-BCG-CWS rendered cancer cells more susceptible to cytolysis by LAK cells. • T24 cells and RT-112 cells, even when cultured singly in the absence of immune cells, can directly respond to R8-liposome-BCG-CWS. • The results obtained in the present study may therefore indicate a novel adoptive immunotherapy against bladder cancers.

Intracellular delivery of nanoparticles with CPPs

Cell-penetrating peptides (CPPs), in particular TATp, have been widely used for intracellular delivery of various cargoes, both in vitro and in vivo. Modifications of nanoparticles with CPPs require either covalent or noncovalent approach. Here we describe various methods to attach CPP, such as TATp to surface of nanocarriers (such as liposomes and micelles), loading with drug or DNA and characterization of same for in vitro and in vivo applications. Due to nonselectivity of CPPs and wide distribution in nontarget areas, method for preparation of "smart" nanocarrier with hidden TATp function is also described.

Gateways for the intracellular access of nanocarriers: a review of receptor-mediated endocytosis mechanisms and of strategies in receptor targeting

IMPORTANCE OF THE FIELD

The last 10 years have seen a dramatic growth in understanding and controlling how complex, drug-loaded (nano)structures, as well as pathogens, or biopharmaceuticals can gather access to the cytoplasm, which is a key step to increasing the effectiveness of their action.

AREAS COVERED IN THIS REVIEW

The review offers an updated overview of the current knowledge of endocytic processes; furthermore, the cell surface receptors most commonly used in drug delivery are here discussed on the basis of their reported internalization mechanisms, with examples of their use as nanocarrier targets taken from the most recent scientific literature.

WHAT THE READER WILL GAIN

Knowledge of molecular biology details is increasingly necessary for a rational design of drug delivery systems. Here, the aim is to provide the reader with an attempt to link a mechanistic knowledge of endocytic mechanisms with the identification of appropriate targets (internalization receptors) for nanocarriers.

TAKE HOME MESSAGE

Much advance is still needed to create a complete and coherent biological picture of endocytosis, but current knowledge already allows individuation of a good number of targetable groups for a predetermined intracellular fate of nanocarriers.