Physicochemical properties and nuclease resistance of antisense-oligodeoxynucleotides entrapped in the core of polyion complex micelles composed of poly(ethylene glycol)-poly(L-lysine) block copolymers

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Noncovalent Stabilization of Vesicular Polyion Complexes with Chemically Modified/Single-Stranded Oligonucleotides and PEG-b-guanidinylated Polypeptides for Intracavity Encapsulation of Effector Enzymes Aimed at Cooperative Gene Knockdown

For the simultaneous delivery of antisense oligonucleotides and their effector enzymes into cells, nanosized vesicular polyion complexes (PICs) were fabricated from oppositely charged polyion pairs of oligonucleotides and poly(ethylene glycol) (PEG)-b-polypeptides. First, the polyion component structures were carefully designed to facilitate a multimolecular (or secondary) association of unit PICs for noncovalent (or chemical cross-linking-free) stabilization of vesicular PICs. Chemically modified, single-stranded oligonucleotides (SSOs) dramatically stabilized the multimolecular associates under physiological conditions, compared to control SSOs without chemical modifications and duplex oligonucleotides. In addition, a high degree of guanidino groups in the polypeptide segment was also crucial for the high stability of multimolecular associates. Dynamic light scattering and transmission electron microscopy revealed the stabilized multimolecular associates to have a 100 nm sized vesicular architecture with a narrow size distribution. The loading number of SSOs per nanovesicle was determined to be ∼2500 using fluorescence correlation spectroscopic analyses with fluorescently labeled SSOs. Furthermore, the nanovesicle stably encapsulated ribonuclease H (RNase H) as an effector enzyme at ∼10 per nanovesicle through simple vortex-mixing with preformed nanovesicles. Ultimately, the RNase H-encapsulated nanovesicle efficiently delivered SSOs with RNase H into cultured cancer cells, thereby eliciting the significantly higher gene knockdown compared with empty nanovesicles (without RNase H) or a mixture of nanovesicles with RNase H without encapsulation. These results demonstrate the great potential of noncovalently stabilized nanovesicles for the codelivery of two varying bio-macromolecule payloads for ensuring their cooperative biological activity.

Self-Assembled Casein Nanoparticles Loading Triptolide for the Enhancement of Oral Bioavailability

Triptolide (TP), a broad-spectrum antitumor drug, has very poor solubility and oral bioavailability, which limits its clinical use. Compared with conventional formulations of TP, a casein (Cas)-based drug delivery system has been reported to have significant advantages for the improvement of solubility and bioavailability of insoluble drugs. In this paper, we report the successful preparation of TP-loaded Cas nanoparticles (TP-Cas) using the self-assembly characteristics of Cas in water and the optimization of the formulation by evaluation of entrapment efficiency (EE) and loading efficiency (LE). Dynamic light scattering, transmission electron microscopy, Fourier-transform infrared spectrometry, X-ray diffractometry (XRD), and differential scanning calorimetry (DSC) was adopted to characterize the TP-Cas. Results showed that the obtained TP-Cas were approximately spherical with a particle size of 128.7 ± 11.5 nm, EE of 72.7 ± 4.7 %, and LE of 8.0% ± 0.5%. Furthermore, in vitro release behavior of TP-Cas in PBS (pH = 7.4) was also evaluated, showing a sustained-release profile. Additionally, an in vivo study in rats displayed that the mean plasma concentration of TP after oral administration of TP-Cas was significantly higher than that treated with TP oral suspension. The C max value for TP-Cas (8.0 ± 4.4 μg/mL) was significantly increased compared with the free TP (0.9 ± 0.3 μg/mL). Accordingly, the area under the curve (AUC0-8) of TP-Cas was 2.8 ± 0.8 mg/L·h, 4.3-fold higher than that of TP suspension (0.6 ± 0.1 mg/L·h). Therefore, it can be concluded that TP-Cas enhanced the absorption and improved oral bioavailability of TP. Taking the good oral safety of Cas into consideration, TP-Cas should be a more promising preparation of TP for clinical application.

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.

Effect of Ionic Group on the Complex Coacervate Core Micelle Structure

Pairs of ionic group dependence of the structure of a complex coacervate core micelle (C3M) in an aqueous solution was investigated using DLS, cryo-TEM, and SANS with a contrast matching technique and a detailed model analysis. Block copolyelectrolytes were prepared by introducing an ionic group (i.e., ammonium, guanidinium, carboxylate, and sulfonate) to poly(ethylene oxide-b-allyl glycidyl ether) (NPEO = 227 and NPAGE = 52), and C3Ms were formed by simple mixing of two oppositely-charged block copolyelectrolyte solutions with the exactly same degree of polymerization. All four C3Ms are spherical with narrow distribution of micelle dimension, and the cores are significantly swollen by water, resulting in relatively low brush density of PEO chains on the core surface. With the pair of strong polyelectrolytes, core radius and aggregation number increases, which reflects that the formation of complex coacervates are significantly sensitive to the pairs of ionic groups rather than simple charge pairing.

Cytocompatibility and Cellular Internalization of PEGylated "Clickable" Nucleic Acid Oligomers

The recently developed synthetic oligonucleotides referred to as "click" nucleic acids (CNAs) are promising due to their relatively simple synthesis based on thiol-X reactions with numerous potential applications in biotechnology, biodetection, gene silencing, and drug delivery. Here, the cytocompatibility and cellular uptake of rhodamine tagged, PEGylated CNA copolymers (PEG-CNA-RHO) were evaluated. NIH 3T3 fibroblast cells treated for 1 h with 1, 10, or 100 μg/mL PEG-CNA-RHO maintained an average cell viability of 86%, which was not significantly different from the untreated control. Cellular uptake of PEG-CNA-RHO was detected within 30 s, and the amount internalized increased over the course of 1 h. Moreover, these copolymers were internalized within cells to a higher degree than controls consisting of either rhodamine tagged PEG or the rhodamine alone. Uptake was not affected by temperature (i.e., 4 or 37 °C), suggesting a passive uptake mechanism. Subcellular colocalization analysis failed to indicate significant correlations between the internalized PEG-CNA-RHO and the organelles examined (mitochondria, endoplasmic reticulum, endosomes and lysosomes). These results indicate that CNA copolymers are cytocompatible and are readily internalized by cells, supporting the idea that CNAs are a promising alternative to DNA in antisense therapy applications.

PEO-PPO-PEO Tri-Block Copolymers for Gene Delivery Applications in Human Regenerative Medicine-An Overview

Lineal (poloxamers or Pluronic^®) or X-shaped (poloxamines or Tetronic^®) amphiphilic tri-block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PEO-PPO-PEO) have been broadly explored for controlled drug delivery in different regenerative medicine approaches. The ability of these copolymers to self-assemble as micelles and to undergo sol-to-gel transitions upon heating has endowed the denomination of “smart” or “intelligent” systems. The use of PEO-PPO-PEO copolymers as gene delivery systems is a powerful emerging strategy to improve the performance of classical gene transfer vectors. This review summarizes the state of art of the application of PEO-PPO-PEO copolymers in both nonviral and viral gene transfer approaches and their potential as gene delivery systems in different regenerative medicine approaches.

Synthesis and characterization of bioreducible cationic biarm polymer for efficient gene delivery

We synthesized a new cationic AB₂ miktoarm block copolymer consisting of one poly (ethylene glycol) (PEG) block and two cationic poly (l-lysine) (PLL) blocks, wherein the PLL blocks were conjugated to the PEG blocks with or without a bioreducible linker (disulfide bonds). Bioreducible and non-bioreducible miktoarm block copolymers (mPEG-(ss-PLL)₂ and mPEG-PLL₂) were prepared for efficient gene delivery as a non-viral gene delivery approach. Both cationic copolymers (bioreducible and nonbioreducible) efficiently formed the nanopolyplexes with plasmid DNA (pDNA) through electrostatic interaction at different weight ratio of polymer and pDNA. Gene condensation ability of the polymers and release of the DNA under reduction condition were measured by gel electrophoresis. Dynamic light scattering (DLS) and field-emission transmission electron microscopy (FE-TEM) were used to measure the average hydrodynamic diameter and morphology of the nanoparticles, respectively. The bioreducible nanopolyplexes showed lower cytotoxicity and higher gene expression than the non-reducible nanopolyplexes in cancer cells.

RETRACTED: Highly antibacterial polypeptide-based amphiphilic copolymers as multifunctional non-viral vectors for enhanced intracellular siRNA delivery and anti-infection

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Authors. The manuscript contains in vivo animal experiment (antiinfection study). The corresponding author checked all raw data again and found that the approval from the Animal Ethics Committee at Xi’an Jiaotong University was not received prior to performing the animal experiment, although it was stated as such in the paper. The authors apologize for the oversight. Given the situation, the authors do not have the confidence in the normalization of the animal experiments process and corresponding results. To maintain the academic standards and rigor, the authors request the retraction of this paper. All authors agree with this retraction except for Peter X. Ma where no response could be solicited in time.

Bulk and nanoscale polypeptide based polyelectrolyte complexes

Polyelectrolyte complexes (PECs) formed using polypeptides have great potential for developing new self-assembled materials, in particular for the development of drug and gene delivery vehicles. This review discusses the latest advancements in PECs formed using polypeptides as the polyanion and/or the polycation in both polyelectrolyte complexes that form bulk materials and block copolymer complexes that form nanoscale assemblies such as PEC micelles and other self-assembled structures. We highlight the importance of secondary structure formation between homogeneous polypeptide complexes, which, unlike PECs formed using other polymers, introduces additional intermolecular interactions in the form of hydrogen bonding, which may influence precipitation over coacervation. However, we still include heterogeneous complexes consisting of polypeptides and other polymers such as nucleic acids, sugars, and other synthetic polyelectrolytes. Special attention is given to complexes formed using nucleic acids as polyanions and polypeptides as polycations and their potential for delivery applications.

Synthesis, characterization and association behavior of linear-dendritic amphiphilic diblock copolymers based on poly(ethylene oxide) and a dendron derived from 2,2′-bis(hydroxymethyl)propionic acid

Two new amphiphilic linear-dendritic block copolymers have been synthesized and characterized. And their association behaviors have also been studied.

Inhibition of atherosclerosis-promoting microRNAs via targeted polyelectrolyte complex micelles

Polyelectrolyte complex micelles have great potential as gene delivery vehicles because of their ability to encapsulate charged nucleic acids forming a core by neutralizing their charge, while simultaneously protecting the nucleic acids from non-specific interactions and enzymatic degradation. Furthermore, to enhance specificity and transfection efficiency, polyelectrolyte complex micelles can be modified to include targeting capabilities. Here, we describe the design of targeted polyelectrolyte complex micelles containing inhibitors against dys-regulated microRNAs (miRNAs) that promote atherosclerosis, a leading cause of human mortality and morbidity. Inhibition of dys-regulated miRNAs in diseased cells associated with atherosclerosis has resulted in therapeutic efficacy in animal models and has been proposed to treat human diseases. However, the non-specific targeting of microRNA inhibitors via systemic delivery has remained an issue that may cause unwanted side effects. For this reason, we incorporated two different peptide sequences to our miRNA inhibitor containing polyelectrolyte complex micelles. One of the peptides (Arginine-Glutamic Acid-Lysine-Alanine or REKA) was used in another micellar system that demonstrated lesion-specific targeting in a mouse model of atherosclerosis. The other peptide (Valine-Histidine-Proline-Lysine-Glutamine-Histidine-Arginine or VHPKQHR) was identified via phage display and targets vascular endothelial cells through the vascular cell adhesion molecule-1 (VCAM-1). In this study we have tested the in vitro efficacy and efficiency of lesion- and cell-specific delivery of microRNA inhibitors to the cells associated with atherosclerotic lesions via peptide-targeted polyelectrolyte complex micelles. Our results show that REKA-containing micelles (fibrin-targeting) and VHPKQHR-containing micelles (VCAM-1 targeting) can be used to carry and deliver microRNA inhibitors into macrophages and human endothelial cells, respectively. Additionally, the functionality of miRNA inhibitors in cells was demonstrated by analyzing miRNA expression as well as the expression or the biological function of its downstream target protein. Our study provides the first demonstration of targeting dys-regulated miRNAs in atherosclerosis using targeted polyelectrolyte complex micelles and holds promising potential for translational applications.

Mannosylated chitosan nanoparticles for delivery of antisense oligonucleotides for macrophage targeting

The therapeutic potential of antisense oligonucleotides (ASODN) is primarily dependent upon its safe and efficient delivery to specific cells overcoming degradation and maximizing cellular uptake in vivo. The present study focuses on designing mannosylated low molecular weight (LMW) chitosan nanoconstructs for safe ODNs delivery by macrophage targeting. Mannose groups were coupled with LMW chitosan and characterized spectroscopically. Mannosylated chitosan ODN nanoparticles (MCHODN NPs) were formulated by self-assembled method using various N/P ratio (moles of amine groups of MCH to phosphate moieties of ODNs) and characterized for gel retardation assay, physicochemical characteristics, cytotoxicity and transfection efficiency, and antisense assay. Complete complexation of MCH/ODN was achieved at charge ratio of 1:1 and above. On increasing the N/P ratio of MCH/ODN, particle size of the NPs decreased whereas zeta potential (ZV) increased. MCHODN NPs displayed much higher transfection efficiency into Raw 264.7 cells (bears mannose receptors) than Hela cells and no significant toxicity was observed at all MCH concentrations. Antisense assay revealed that reduction in lipopolysaccharide (LPS) induced serum TNF-α is due to antisense activity of TJU-2755 ODN (sequence complementary to 3′-UTR of TNF-α). These results suggest that MCHODN NPs are acceptable choice to improve transfection efficiency in vitro and in vivo.

Molecular dynamics study on the interaction between doxorubicin and hydrophobically modified chitosan oligosaccharide

Both π–π interactions and hydrophobic interactions were found to be essential for the loading of doxorubicin on hydrophobically modified chitosan oligosaccharides.

Multifunctional triblock co-polymer mP3/4HB-b-PEG-b-lPEI for efficient intracellular siRNA delivery and gene silencing

A non-viral siRNA carrier composed of mono-methoxy-poly (3-hydroxybutyrate-co-4-hydroxybutyrate)-block-polyethylene glycol-block-linear polyethyleneimine (mP3/4HB-b-PEG-b-lPEI) was synthesized using 1800 Da linear polyethyleneimine and evaluated for siRNA delivery. Our study demonstrated that siRNA could be efficiently combined with mP3/4HB-b-PEG-b-lPEI (mAG) co-polymer and was protected from nuclease degradation. The combined siRNA were released from the complexes easily under heparin competition. The particle size of the mAG/siRNA complexes was 158 nm, with a ζ-potential of around 28 mV. Atomic force microscopy images displayed spherical and homogeneously distributed complexes. The mAG block co-polymer displayed low cytotoxicity and efficient cellular uptake of Cy3-siRNA in A549 cells by flow cytometry and confocal microscopy. In vitro transfection efficiency of the block co-polymer was assessed using siRNA against luciferase in cultured A549-Luc, HeLa-Luc, HLF-Luc, A375-Luc and MCF-7-Luc cells. A higher transfection efficiency and lower cytotoxicity was obtained by mAG block co-polymer in five cell lines. Furthermore, a remarkable improvement in luciferase gene silencing efficiency of the mAG complex (up to 90-95%) over that of Lipofectamine™ 2000 (70-82%) was observed in HLF-Luc and A375-Luc cells. Additionally, a mAG/p65-siRNA complex also showed a better capability than Lipofectamine™ 2000/p65-siRNA complex to drastically reduce the p65 mRNA level down to 10-16% in HeLa, U251 and HUVEC cells at an N/P ratio of 70.

Hepatocyte-targeting gene transfer mediated by galactosylated poly(ethylene glycol)-graft-polyethylenimine derivative

Biscarbamate cross-linked polyethylenimine derivative (PEI-Et) has been reported as a novel nonviral vector for efficient and safe gene transfer in our previous work. However, it had no cell-specificity. To achieve specific delivery of genes to hepatocytes, galactosylated poly(ethylene glycol)-graft-polyethylenimine derivative (GPE) was prepared through modification of PEI-Et with poly(ethylene glycol) and lactobionic acid, bearing a galactose group as a hepatocyte-targeting moiety. The composition of GPE was characterized by proton nuclear magnetic resonance. The weight-average molecular weight of GPE measured with a gel permeation chromatography instrument was 9489 Da, with a polydispersity of 1.44. GPE could effectively condense plasmid DNA (pDNA) into nanoparticles. Gel retardation assay showed that GPE/pDNA complexes were completely formed at weigh ratios (w/w) over 3. The particle size of GPE/pDNA complexes was 79-100 nm and zeta potential was 6-15 mV, values which were appropriate for cellular uptake. The morphology of GPE/pDNA complexes under atomic force microscopy appeared spherical and uniform in size, with diameters of 53-65 nm. GPE displayed much higher transfection efficiency than commercially available PEI 25 kDa in BRL-3A cell lines. Importantly, GPE showed good hepatocyte specificity. Also, the polymer exhibited significantly lower cytotoxicity compared to PEI 25 kDa at the same concentration or weight ratio in BRL-3A cell lines. To sum up, our results indicated that GPE might carry great potential in safe and efficient hepatocyte-targeting gene delivery.

Investigation of the performance of PEG-PEI/ROCK-II-siRNA complexes for Alzheimer's disease in vitro

Recent studies have showed inhibiting ROCK promoted axonal regeneration and suppressing ROCK-II decreased Aβ formation, suggesting ROCK is a potential target for the treatment of Alzheimer's disease. Because ROCK-II mRNA is abundantly expressed in brain, we targeted ROCK-II mRNA using a siRNA approach. To suppress ROCK-II mRNA expression, we synthesized PEG-PEI/ROCK-II-siRNA complexes and transfected C17.2 neural stem cells in vitro. The characteristics of the complexes were tested using a gel retardation assay. Particle size and zeta potential were examined using dynamic light scattering and the morphology of the complexes were observed by transmission electron microscopy. The toxicity was detected by an MTT assay and transfection efficiency was determined by flow cytometry. Laser confocal microscopy was employed to investigate the cell uptake of the complexes. RT-PCR and western blotting were used to verify the effect of gene silencing. Our results indicated that the characteristics of the complexes depended on the N/P ratios. At a high N/P ratio, PEG-PEI could completely condense the siRNA into small-sized uniform particles. However, high N/P ratios are accompanied with high cytotoxicity. Because of high transfection efficiency and low cytotoxicity, N/P=50 was chosen to transfect C17.2 cells in vitro. Laser confocal microscopy showed that ROCK-II-siRNA with green fluorescence was mainly distributed in the cytoplasm and synapses. Moreover, ROCK-II-siRNA was successfully released from the lysosome. RT-PCR and western blotting demonstrated effective gene silencing. These results indicated that PEG-PEI/ROCK-II-siRNA complexes effectively suppressed ROCK-II mRNA expression, providing the basis for future research in vivo.

The interactions of amphiphilic antisense oligonucleotides with serum proteins and their effects on in vitro silencing activity

Antisense oligonucleotides (AONs) are a class of compounds with high therapeutic potential. One of the challenges facing this platform is the development of effective techniques to achieve cellular delivery. AON conjugates, in which traditional AONs are attached to certain biomolecules, can exhibit improved intracellular bioavailability in the absence of delivery systems. In this study, the lipophilic moieties docosahexaenoic acid, cholesterol, and docosanoic acid (DSA) were conjugated to various phosphorothioated DNA and chemically-modified 2'-fluoro-arabinonucleic acid AONs via an amino-hexanol-linker added to the 5'-end of the molecule. The gene silencing potential of these compounds was evaluated in vitro in the absence or presence of a transfecting agent (polyion complex micelle). Incubation with sub-micromolar concentration of DSA-conjugates could, in the absence of serum proteins, downregulate more than 60% of the targeted mRNA under carrier-free and carrier-loaded delivery methods. Gene silencing activity of carrier-free DSA-conjugates was, however, decreased in a dose-dependent fashion by adding albumin in the transfection medium. Supplementing the medium with free fatty acid prevented the interaction of the DSA-conjugate with albumin, and restored its silencing activity. These findings suggest that strategies aiming at preventing the association of hydrophobized AONs to serum proteins at the site of action may improve their activity.

Efficient delivery of antitumor drug to the nuclei of tumor cells by amphiphilic biodegradable poly(L-aspartic acid-co-lactic acid)/DPPE co-polymer nanoparticles

The use of biodegradable polymeric nanoparticles (NPs) for controlled drug delivery has shown significant therapeutic potential. Polyaspartic acid and polylactic acid are the most intensively studied biodegradable polymers. In the present study, novel amphiphilic biodegradable co-polymer NPs, poly(L-aspartic acid-co-lactic acid) with 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) (poly(AA-co-LA)/DPPE) is synthesized and subsequently used to encapsulate an antitumor drug doxorubicin (DOX). The formulation parameters of the NPs are optimized to improve encapsulation efficiency. The resulting drug-loaded NPs possess better size homogeneity (polydispersity) and exhibit pH-responsive drug release profiles. Cellular viability assays indicate that the poly(AA-co-LA)/DPPE NPs did not induce cell death, whereas doxorubicin encapsulated NPs were cytotoxic to various types of tumor cells. In addition, the free NPs could not enter the cell nuclei after internalized in tumor cells. The DOX-loaded NPs exhibit efficient intracellular delivery in tumor cells with co-localization in lysosome and delay entering into the nucleus, which suggests a time- and pH-dependent drug release profile within cells. When applied to deliver chemotherapeutics to a mouse xenograft model of human lung adenocarcinoma, DOX-loaded NPs have a comparable antitumor activity with free DOX, and greatly reduce systemic toxicity and mortality. The delivery of cytotoxic drugs directly to the nucleus specifically within tumor cells is of great interest. These results demonstrate the feasibility of the application of the amphiphilic polyaspartic acid derivative, poly(AA-co-LA)/DPPE, as a nanocarrier for cell nuclear delivery of potent antitumor drugs.

Biscarbamate cross-linked polyethylenimine derivative with low molecular weight, low cytotoxicity, and high efficiency for gene delivery

Polyethylenimine (PEI), especially PEI 25 kDa, has been widely studied for delivery of nucleic acid drugs both in vitro and in vivo. However, it lacks degradable linkages and is too toxic for therapeutic applications. Hence, low-molecular-weight PEI has been explored as an alternative to PEI 25 kDa. To reduce cytotoxicity and increase transfection efficiency, we designed and synthesized a novel small-molecular-weight PEI derivative (PEI-Et, Mn: 1220, Mw: 2895) with ethylene biscarbamate linkages. PEI-Et carried the ability to condense plasmid DNA (pDNA) into nanoparticles. Gel retardation assay showed complete condensation of pDNA at w/w ratios that exceeded three. The particle size of polymer/pDNA complexes was between 130 nm and 180 nm and zeta potential was 5–10 mV, which were appropriate for cell endocytosis. The morphology of PEI-Et/pDNA complexes observed by atomic force microscopy (AFM) was spherically shaped with diameters of 110–190 nm. The transfection efficiency of polymer/pDNA complexes as determined with the luciferase activity assay as well as fluorescence-activated cell-sorting analysis (FACS) was higher than commercially available PEI 25 kDa and Lipofectamine 2000 in various cell lines. Also, the polymer exhibited significantly lower cytotoxicity compared to PEI 25 kDa at the same concentration in three cell lines. Therefore, our results indicated that the PEI-Et would be a promising candidate for safe and efficient gene delivery in gene therapy.

Nanocarrier possibilities for functional targeting of bioactive peptides and proteins: state-of-the-art

This review attempts to provide an updated compilation of studies reported in the literature pertaining to production of nanocarriers encasing peptides and/or proteins, in a way that helps the reader direct a bibliographic search and develop an integrated perspective of the subject. Highlights are given to bioactive proteins and peptides, with a special focus on those from dairy sources (including physicochemical characteristics and properties, and biopharmaceutical application possibilities of e.g. lactoferrin and glycomacropeptide), as well as to nanocarrier functional targeting. Features associated with micro- and (multiple) nanoemulsions, micellar systems, liposomes and solid lipid nanoparticles, together with biopharmaceutical considerations, are presented in the text in a systematic fashion.

Engineering of amphiphilic block copolymers for polymeric micellar drug and gene delivery

The use of nano-delivery systems formed through assembly of synthetic amphiphilic block copolymers (ABCs) in experimental medicine and pharmaceutical sciences is experiencing rapid development. This rapid development is driven by a crucial need in improving the performance of existing therapeutic agents, as well as the necessity for the development of advanced delivery systems for complex new entities such as genes, proteins and other cellular components. The flexibility in the construction of appropriate carriers for the delivery requirements of these complex new "drugs" offered by versatile polymer chemistry provides an undeniable advantage for polymer based nano-delivery systems compared to other colloids in this regard. With seven formulations already in different stages of clinical trials, polymeric micelles are in the front line of drug development among different ABC-based nano-carriers. The success in rapid advancement of polymeric micelles from bench to bedside is owed to the rational engineering of core/shell structure so that the polymeric micellar carrier can meet the requirements for optimum delivery of specific drug(s) in certain disease condition(s). The engineering efforts in this regard have mostly been aimed at providing efficient drug loading, micellar stabilization, and sustained and/or site specific drug release. The objective of this review is to provide an update on different engineering strategies employed to achieve optimum polymeric micellar formulations.

Self-assembled and nanostructured siRNA delivery systems

A wide range of organic and inorganic materials have been used in the development of nano-scale self-assembling gene delivery systems to improve the therapeutic efficacy of nucleic acid drugs. Small interfering RNA (siRNA) has recently been recognized as a promising and potent nucleic acid medicine for the treatment of incurable genetic disorders including cancer; however, siRNA-based therapeutics suffer from the same delivery problems as conventional nucleic acid drugs such as plasmid DNA and antisense oligonucleotides. Many of the delivery strategies developed for nucleic acid drugs have been applied to siRNA therapeutics, but they have not produced satisfactory in vivo gene silencing efficiencies to warrant clinical trials. This review discusses recent progress in the development of self-assembled and nanostructured delivery systems for efficient siRNA-induced gene silencing and their potential application in clinical settings.

siRNA nanocarriers based on methacrylic acid copolymers

Poly(ethylene glycol)-b-poly(propyl methacrylate-co-methacrylic acid) (PEG-b-P(PrMA-co-MAA) can be complexed with poly(amido amine) (PAMAM) dendrimers and nucleic acids to form pH-responsive nanosized core-shell type polyion complex micelles (PICMs). These PICMs have the ability to lose their shell and release the PAMAM/nucleic acid core under mildly acidic conditions such as those encountered in the endosomal compartment. In this work, pH-sensitive PICMs composed of PEG-b-P(PrMA-co-MAA), different PAMAMs, and siRNAs were prepared and characterized. These micelles had mean diameters ranging from 50 to 100 nm depending on the structure of the polycationic component. In order to trigger PICM uptake by receptor-mediated endocytosis, the micelles were decorated with an antibody fragment directed against the transferrin receptor (anti-CD71). The targeting ligand was stably conjugated to a semi-telechelic amino-PEG-b-P(PrMA-co-MAA) via a maleimide/activated ester bifunctional linker, yielding up to 60%-80% functionalization of the maleimide groups. The cellular uptake of the micelles was assessed on human prostate cancer cells (PC-3) via flow cytometry. Native PICMs and micelles bearing a non-specific antibody fragment were taken up to the same extent with a low efficiency, whereas anti-CD71 Fab'-decorated PICMs exhibited significantly higher uptake. The capacity of the targeted, siRNA-loaded, PICMs to downregulate the expression of the Bcl-2 anti-apoptotic oncoprotein was investigated using the appropriate unmodified or 2'-modified (2'F-RNA and 2'F-ANA) siRNA sequence. Bcl-2 mRNA and protein levels were greatly reduced when the cells were transfected with anti-CD71 decorated PICMs. Optimal silencing was achieved with the chemically modified siRNA. These data suggest that combining optimized siRNA chemistry with an effective delivery system can potentiate the activity of siRNA, thereby potentially reducing the total dose of carrier required to achieve a pharmacological effect.

The investigation of polymer-siRNA nanoparticle for gene therapy of gastric cancer in vitro

Small interfering RNA (siRNA) molecules have significant therapeutic promise for the genetic treatment of cancer. To overcome instability and low transfection efficiency, polyethylene glycol-polyethyleneimine (PEG-PEI) was synthesized and investigated as a non-viral carrier of siRNA targeting CD44v6 in gastric carcinoma cells. The size, surface charge using zeta potential, and morphology via scanning electron microscopy (SEM) of PEG-PEI/siRNA nanoparticles was characterized, and their cytotoxicity, transfection efficiency, and interaction with SGC7901 human gastric carcinoma cells was evaluated. The transfection efficiency of PEG-PEI/siRNA nanocomplexes was dependant on the charge ratio between amino groups of PEG-PEI and phosphate groups of siRNA (N/P) values, which reflected the molar ratio of PEG-PEI to siRNA during complex formation. The transfection efficiency of PEG-PEI/siRNA at N/P 15 was 72.53% ± 2.38%, which was higher than that observed using Lipofectamine 2000 and PEI as delivery carriers. Cytotoxicity of PEG-PEI was determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay and was obviously lower than that of PEI. Moreover, when N/P was below 15, PEG-PEI/siRNA was less toxic than Lipofectamine 2000/siRNA. RT-PCR (real time polymerase chain reaction) and Western blot analyses of CD44v6 expression demonstrated the gene silencing effect of PEG-PEI/siRNA at N/P 15. These data indicate that PEG-PEI may be a promising non-viral carrier for altering gene expression in the treatment of gastric cancer with many advantages, such as relatively high gene transfection efficiency and low cytotoxicity.

siRNA-based therapy ameliorates glomerulonephritis

RNA interference by short interfering RNAs (siRNAs) holds promise as a therapeutic strategy, but use of siRNAs in vivo remains limited. Here, we developed a system to target delivery of siRNAs to glomeruli via poly(ethylene glycol)-poly(l-lysine)-based vehicles. The siRNA/nanocarrier complex was approximately 10 to 20 nm in diameter, a size that would allow it to move across the fenestrated endothelium to access to the mesangium. After intraperitoneal injection of fluorescence-labeled siRNA/nanocarrier complexes, we detected siRNAs in the blood circulation for a prolonged time. Repeated intraperitoneal administration of a mitogen-activated protein kinase 1 (MAPK1) siRNA/nanocarrier complex suppressed glomerular MAPK1 mRNA and protein expression in a mouse model of glomerulonephritis; this improved kidney function, reduced proteinuria, and ameliorated glomerular sclerosis. Furthermore, this therapy reduced the expression of the profibrotic markers TGF-beta1, plasminogen activator inhibitor-1, and fibronectin. In conclusion, we successfully silenced intraglomerular genes with siRNA using nanocarriers. This technique could aid the investigation of molecular mechanisms of renal disease and has potential as a molecular therapy of glomerular diseases.

Development of a targeted siRNA delivery system using FOL-PEG-PEI conjugate

Receptor mediated delivery of siRNA enables silencing of target genes in specific tissues. Folate receptor (FR) is an attractive target for tumor-selective gene delivery. The focus of this study was to deliver the dihydrofolate reductase (DHFR) siRNA expressing plasmid and to silence the DHFR gene in FR positive KB cells, by complexing the plasmid with a folate-polyethylene glycol-polyethylenimine (FOL-PEG-PEI) conjugate, as a gene carrier. A DHFR siRNA sequence was cloned into a pSUPER-RNAi vector and complexed with the FOL-PEG-PEI conjugate. The complex was characterized by particle size analyzer, gel retardation and DNase protection assay. The FOL-PEG-PEI/pSUPER-siDHFR complex was transfected to FR overexpressing (KB) and FR negative (A549) cells. The transfection effiencies and gene inhibition were analyzed by fluorescence microscopy and RT-PCR. The pSUPER-siDHFR/PEI-PEG-FOL complex delivered the siRNA vector and inhibited DHFR gene in KB cells, while A549 cells were unaffected. Lipofectamine mediated transfection of pSUPER-siDHFR, delivered the vector and inhibited the DHFR gene in both KB and A549 cells. FR mediated delivery of siDHFR complexed with PEI-PEG-FOL conjugate inhibits the DHFR expression in FR positive cells alone. This strategy can be extended to deliver a wide range of drugs and post-transcriptional gene silencing therapeutics.

Intelligent polymeric micelles from functional poly(ethylene glycol)-poly(amino acid) block copolymers

This review describes our recent efforts on the design and preparation of intelligent polymeric micelles from functional poly(ethylene glycol)-poly(amino acid) (PEG-PAA) block copolymers. The polymeric micelles feature a spherical sub-100 nm core-shell structure in which anticancer drugs are loaded avoiding undesirable interactions in vivo. Chemical modification of the core-forming block of PEG-PAA with a hydrazone linkage allows the polymeric micelles to release drugs selectively at acidic pH (4-6). Installation of folic acids on the micelle surface improves cancer cell-specific drug delivery efficiency along with pH-controlled drug release. These intelligent micelles appear to be superior over classical micelles that physically incorporate drugs. Studies showed both controlled drug release and targeted delivery features of the micelles reduced toxicity and improved efficacy significantly. Further developments potentiate combination delivery of multiple drugs using mixed micelles. Therefore clinically relevant performance of the polymeric micelles provides a promising approach for more efficient and patient-friendly cancer therapy.

Prospects for nanomedicine in treating age-related macular degeneration

Polyion complex (PIC) micelles have a size range of tens of nanometers formed through electrostatic interaction. In experimental choroidal neovascularization (CNV) in rats, the PIC micelle accumulates to the CNV lesions and is retained. PIC micelles can be used for effective drug delivery to CNV. A novel dendritic photosensitizer encapsulated by a polymeric-micelle formulation was employed for an effective photodynamic therapy for age-related macular degeneration. With its highly selective accumulation on experimental CNV lesions, this treatment resulted in a remarkably efficacious CNV occlusion with minimal unfavorable phototoxicity. Gene therapy is a promising approach to treat age-related macular degeneration. A ternary complex, composed of a core containing DNA packaged with cationic peptides and enveloped in the anionic dendrimer phthalocyanine, has been developed, which provides the photosensitizing action. Subconjunctival injection of the ternary complex followed by laser irradiation resulted in transgene expression only in the laser-irradiated site in rats.

Complex coacervate core micelles

In this review we present an overview of the literature on the co-assembly of neutral-ionic block, graft, and random copolymers with oppositely charged species in aqueous solution. Oppositely charged species include synthetic (co)polymers of various architectures, biopolymers - such as proteins, enzymes and DNA - multivalent ions, metallic nanoparticles, low molecular weight surfactants, polyelectrolyte block copolymer micelles, metallo-supramolecular polymers, equilibrium polymers, etcetera. The resultant structures are termed complex coacervate core/polyion complex/block ionomer complex/interpolyelectrolyte complex micelles (or vesicles); i.e., in short C3Ms (or C3Vs) and PIC, BIC or IPEC micelles (and vesicles). Formation, structure, dynamics, properties, and function will be discussed. We focus on experimental work; theory and modelling will not be discussed. Recent developments in applications and micelles with heterogeneous coronas are emphasized.

Polymer nanocarriers for the delivery of small fragments of nucleic acids: oligonucleotides and siRNA

The success of the application of new therapeutic methods based on RNA interfering strategies requires the in vivo delivery of active ODN or siRNA down to the intracellular compartment of the target cells. This article aims to review the studies related to the formulation of RNA interfering agents in polymer nanocarriers. It will present the different types of polymer nanocarriers used as well as the biological activity of the resulting ODN and siRNA loaded nanocarriers. As will be explained, the part of the in vitro studies provided useful data about the intracellular delivery of the formulated RNA interfering agents. Investigations performed in vivo have considered animal models of different relevant diseases. Results from these investigations have clearly demonstrated the interest of several polymer nanocarriers tested so far to deliver active RNA interfering effectors in vivo making possible their administration by the intravenous route.

Block copolymer micelles as delivery vehicles of hydrophobic drugs: Micelle–cell interactions

One-third of drugs in development are water insoluble and one-half fail in trials because of poor pharmacokinetics. Block copolymer micelles are nanosized particles that can solubilize hydrophobic drugs and alter their kinetics in vitro and in vivo. However, block copolymer micelles are not solely passive drug containers that simply solubilize hydrophobic drugs; cells internalize micelles. To facilitate the development of advanced, controlled, micellar drug delivery vehicles, we have to understand the fate of micelles and micelle-incorporated drugs in cells and in vivo. With micelle-based drug formulations recently reaching clinical trials, the impetus for answers is ever so strong and detailed studies of interactions of micelles and cells are starting to emerge. Most notably, the question arises: Is the internalization of block copolymer micelles carrying small molecular weight drugs an undesired side effect or a useful means of improving the effectiveness of the incorporated drugs?

Characterization of polyion complex micelles designed to address the challenges of oligonucleotide delivery

PURPOSE

To optimize oligonucleotide (ODN)-based polyion complex micelles (PICMs) by studying the effects of polymer composition and length on their properties.

METHODS

Atom transfer radical polymerization was used to synthesize copolymers with increasing hydrophilic nonionic and cationic block lengths. PICMs were prepared by mixing the copolymers and ODN at various nitrogen-to-phosphate (N/P) ratios and characterized by gel electrophoresis and dynamic light scattering. The stability of the complexes towards dissociation was tested using a competitive assay with heparin. Finally, protection of the incorporated ODN against DNAse I degradation was evaluated.

RESULTS

A library of copolymers composed of poly(ethylene glycol) (PEG) and poly(aminoethyl methacrylate) (PAEMA) and/or poly((dimethylamino)ethylmethacrylate) (PDMAEMA) was synthesized. All polymers efficiently interacted with the ODN at N/P ratios approaching 1.5. Narrowly distributed but easily dissociable PICMs were obtained using PEG 5000 and short DMAEMA chains. Shortening the PEG block to 2000, increasing the number of cationic units and using AEMA produced more stable complexes but at the cost of colloidal properties. All polymers were able to protect the ODN from nuclease degradation.

CONCLUSIONS

PEG 3000-based PICMs possess good colloidal properties, intermediate stability towards dissociation and adjustable buffering capacity, making them potentially useful for the delivery of nucleic acid drugs.