Self-assembled and nanostructured siRNA delivery systems

Encapsulation of miRNA and siRNA into Nanomaterials for Cancer Therapeutics

Globally, cancer is amongst the most deadly diseases due to the low efficiency of the conventional and obsolete chemotherapeutic methodologies and their many downsides. The poor aqueous solubility of most anticancer medications and their low biocompatibility make them ineligible candidates for the design of delivery systems. A significant drawback associated with chemotherapy is that there are no advanced solutions to multidrug resistance, which poses a major obstacle in cancer management. Since RNA interference (RNAi) can repress the expression of genes, it is viewed as a novel tool for advanced drug delivery. this is being explored as a promising drug targeting strategy for the treatment of multiple diseases, including cancer. However, there are many obstructions that hinder the clinical uses of siRNA drugs due to their low permeation into cells, off-target impacts, and possible unwanted immune responses under physiological circumstances. Thus, in this article, we review the design measures for siRNA conveyance frameworks and potential siRNA and miRNA drug delivery systems for malignant growth treatment, including the use of liposomes, dendrimers, and micelle-based nanovectors and functional polymer-drug delivery systems. This article sums up the advancements and challenges in the use of nanocarriers for siRNA delivery and remarkably centers around the most critical modification strategies for nanocarriers to build multifunctional siRNA and miRNA delivery vectors. In short, we hope this review will throw light on the dark areas of RNA interference, which will further open novel research arenas in the development of RNAi drugs for cancer.

Applications and perspectives of polyphenol-loaded solid lipid nanoparticles and nanostructured lipid carriers for foods

Imbalanced nutrition in modern society is one of the reasons for disorders, such as cancer, cardiovascular disease, and diabetes, which have attracted the interest in bioactives (particularly polyphenols) to assist in the balanced diet of modern people. Although stability can be maintained during preparation and storage, the ingested polyphenols undergo harsh gastrointestinal digestion processes, resulting in limited bioaccessibility and low gut-epithelial permeation and bioavailability. Several lipid-based formulations have been proposed to overcome these issues. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) have also been highlighted as carrier systems for the oral delivery of lipophilic bioactives, including polyphenols. This paper summarizes the research on the ingredients, production methods, post-processing procedures, general characteristics, and advantages and disadvantages of SLNs and NLCs. Overall, this paper reviews the applications and perspectives of polyphenol-loaded SLNs and NLCs in foods, as well as their regulation, production, storage, and economic feasibility.

Albumin Nanostructures for Nucleic Acid Delivery in Cancer: Current Trend, Emerging Issues, and Possible Solutions

Cancer is one of the major health problems worldwide, and hence, suitable therapies with enhanced efficacy and reduced side effects are desired. Gene therapy, involving plasmids, small interfering RNAs, and antisense oligonucleotides have been showing promising potential in cancer therapy. In recent years, the preparation of various carriers for nucleic acid delivery to the tumor sites is gaining attention since intracellular and extracellular barriers impart major challenges in the delivery of naked nucleic acids. Albumin is a versatile protein being used widely for developing carriers for nucleic acids. It provides biocompatibility, tumor specificity, the possibility for surface modification, and reduces toxicity. In this review, the advantages of using nucleic acids in cancer therapy and the challenges associated with their delivery are presented. The focus of this article is on the different types of albumin nanocarriers, such as nanoparticles, polyplexes, and nanoconjugates, employed to overcome the limitations of the direct use of nucleic acids in vivo. This review also highlights various approaches for the modification of the surface of albumin to enhance its transfection efficiency and targeted delivery in the tumor sites.

Self-assembling peptides cross-linked with genipin: resilient hydrogels and self-standing electrospun scaffolds for tissue engineering applications

Self-assembling peptides (SAPs) are synthetic bioinspired biomaterials that can be feasibly multi-functionalized for applications in surgery, drug delivery, optics and tissue engineering (TE). Despite their promising biocompatibility and biomimetic properties, they have never been considered real competitors of polymers and/or cross-linked extracellular matrix (ECM) natural proteins. Indeed, synthetic SAP-made hydrogels usually feature modest mechanical properties, limiting their potential applications, due to the transient non-covalent interactions involved in the self-assembling phenomenon. Cross-linked SAP-hydrogels have been recently introduced to bridge this gap, but several questions remain open. New strategies leading to stiffer gels of SAPs may allow for a full exploitation of the SAP technology in TE and beyond. We have developed and characterized a genipin cross-linking strategy significantly increasing the stiffness and resiliency of FAQ(LDLK)3, a functionalized SAP already used for nervous cell cultures. We characterized different protocols of cross-linking, analyzing their dose and time-dependent efficiency, influencing stiffness, bioabsorption time and molecular arrangements. We choose the best developed protocol to electrospin into nanofibers, for the first time, self-standing, water-stable and flexible fibrous mats and micro-channels entirely made of SAPs. This work may open the door to the development and tailoring of bioprostheses entirely made of SAPs for different TE applications.

Annealing novel nucleobase-lipids with oligonucleotides or plasmid DNA based on H-bonding or π-π interaction: Assemblies and transfections

Lipid derivatives of nucleoside analogs have been highlighted for their potential for effective gene delivery. A novel class of nucleobase-lipids are rationally designed and readily synthesized, comprising thymine/cytosine, an ester/amide linker and an oleyl lipid. The diversity of four nucleobase-lipids termed DXBAs (DOTA, DNTA, DOCA and DNCA) is investigated. Besides, DNCA is demonstrated to be an effective neutral transfection material for nucleic acid delivery, which enbles to bind to oligonucleotides via H-bonding and π-π stacking with reduced toxicity in vitro and in vivo. Several kinds of nucleic acid drugs including aptamer, ssRNA, antisense oligonucleotide, and plasmid DNAs can be delivered by DXBAs, especially DNCA. In particular, G4-aptamer AS1411 encapsulated by DNCA exhibits cellular uptake enhancement, lysosome degradation reduction, cell apoptosis promotion, cell cycle phase alteration in vitro and duration prolongation in vivo, resulting in significant anti-proliferative activity. Our results demonstrate that DNCA is a promising transfection agent for G4-aptamers and exhibites bright application prospects in the permeation improvement of single-stranded oligonucleotides or plasmid DNAs.

Copper oxide loaded PLGA nanospheres: towards a multifunctional nanoscale platform for ultrasound-based imaging and therapy

Copper oxide nanoparticles (CuO-NPs) are increasingly becoming the subject of investigation exploring their potential use for diagnostic and therapeutic purposes. Recent work has demonstrated their anticancer potential, as well as contrast agent capabilities for magnetic resonance imaging (MRI) and through-transmission ultrasound. However, no capability of CuO-NPs has been demonstrated using conventional ultrasound systems, which, unlike the former, are widely deployed in the clinic. Furthermore, in spite of their potential as multifunctional nano-based materials for diagnosis and therapy, CuO-NPs have been delayed from further clinical application due to their inherent toxicity. Herein, we present the synthesis of a novel nanoscale system, composed of CuO-loaded PLGA nanospheres (CuO-PLGA-NS), and demonstrate its imaging detectability and augmented heating effect by therapeutic ultrasound. The CuO-PLGA-NS were prepared by a double emulsion (W/O/W) method with subsequent solvent evaporation. They were characterized as sphere-shaped, with size approximately 200 nm. Preliminary results showed that the viability of PANC-1, human pancreatic adenocarcinoma cells was not affected after 72 h exposure to CuO-PLGA-NS, implying that PLGA masks the toxic effects of CuO-NPs. A systematic ultrasound imaging evaluation of CuO-PLGA-NS, using a conventional system, was performed in vitro and ex vivo using poultry heart and liver, and also in vivo using mice, all yielding a significant contrast enhancement. In contrast to CuO-PLGA-NS, neither bare CuO-NPs nor blank PLGA-NS possess these unique advantageous ultrasonic properties. Furthermore, CuO-PLGA-NS accelerated ultrasound-induced temperature elevation by more than 4 °C within 2 min. The heating efficiency (cumulative equivalent minutes at 43 °C) was increased approximately six-fold, demonstrating the potential for improved ultrasound ablation. In conclusion, CuO-PLGA-NS constitute a versatile platform, potentially useful for combined imaging and therapeutic ultrasound-based procedures.

Nanoengineered strategies for siRNA delivery: from target assessment to cancer therapeutic efficacy

The promise of RNA interference (RNAi) technology in cancer therapeutics aims to deliver small interfering RNA (siRNA) for silencing of gene expression in cell type-specific pathway. However, the challenge for the delivery of stable siRNA is hindered by an immune-hostile tumor microenvironment and physiological barriers of the circulatory system. Therefore, the development and validation of safe, stable, and efficient nanoengineered delivery systems are highly essential for effective delivery of siRNA into cancer cells. This review focuses on gene-silencing mechanisms, challenges to siRNA delivery, design and delivery of nanocarrier systems, ongoing clinical trials, and translational prospects for siRNA-mediated cancer therapeutics.

Silencing the roadblocks to effective triple-negative breast cancer treatments by siRNA nanoparticles

Over the past decade, RNA interference (RNAi) has been ubiquitously utilized to study biological function in vitro; however, limitations were associated with its utility in vivo More recently, small interfering RNA (siRNA) nanoparticles with improved biocompatibility have gained prevalence as a potential therapeutic option for the treatment of various diseases. The adaptability of siRNA nanoparticles enables the delivery of virtually any siRNA, which is especially advantageous for therapeutic applications in heterogeneous diseases that lack unifying molecular features, such as triple-negative breast cancer (TNBC). TNBC is an aggressive subtype of breast cancer that is stratified by the lack of estrogen receptor/progesterone receptor expression and HER2 amplification. There are currently no FDA-approved targeted therapies for the treatment of TNBCs, making cytotoxic chemotherapy the only treatment option available to these patients. In this review, we outline the current status of siRNA nanoparticles in clinical trials for cancer treatment and discuss the promising preclinical approaches that have utilized siRNA nanoparticles for TNBC treatment. Next, we address TNBC subtype-specific therapeutic interventions and highlight where and how siRNA nanoparticles fit into these strategies. Lastly, we point out ongoing challenges in the field of siRNA nanoparticle research that, if addressed, would significantly improve the efficacy of siRNA nanoparticles as a therapeutic option for cancer treatment.

Recent advances in self-assembled peptides: Implications for targeted drug delivery and vaccine engineering

Self-assembled peptides have shown outstanding characteristics for vaccine delivery and drug targeting. Peptide molecules can be rationally designed to self-assemble into specific nanoarchitectures in response to changes in their assembly environment including: pH, temperature, ionic strength, and interactions between host (drug) and guest molecules. The resulting supramolecular nanostructures include nanovesicles, nanofibers, nanotubes, nanoribbons, and hydrogels and have a diverse range of mechanical and physicochemical properties. These molecules can be designed for cell-specific targeting by including adhesion ligands, receptor recognition ligands, or peptide-based antigens in their design, often in a multivalent display. Depending on their design, self-assembled peptide nanostructures have advantages in biocompatibility, stability against enzymatic degradation, encapsulation of hydrophobic drugs, sustained drug release, shear-thinning viscoelastic properties, and/or adjuvanting properties. These molecules can also act as intracellular transporters and respond to changes in the physiological environment. Furthermore, this class of materials has shown sequence- and structure-dependent impacts on the immune system that can be tailored to non-immunogenic for drug targeting, and immunogenic for vaccine delivery. This review explores self-assembled peptide nanostructures (beta sheets, alpha helices, peptide amphiphiles, amino acid pairing, elastin like polypeptides, cyclic peptides, short peptides, Fmoc peptides, and peptide hydrogels) and their application in vaccine delivery and drug targeting.

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.

Chitosan-Based Nano-Embedded Microparticles: Impact of Nanogel Composition on Physicochemical Properties

Chitosan-based nanogels have been widely applied as drug delivery vehicles. Spray-drying of said nanogels allows for the preparation of dry powder nano-embedded microparticles. In this work, chitosan-based nanogels composed of chitosan, alginate, and/or sodium tri-penta phosphate were investigated, particularly with respect to the impact of composition on the resulting physicochemical properties. Different compositions were obtained as nanogels with sizes ranging from 203 to 561 nm. The addition of alginate and exclusion of sodium tri-penta phosphate led to an increase in nanogel size. The nanogels were subsequently spray-dried to form nano-embedded microparticles with trehalose or mannitol as matrix excipient. The microparticles of different composition were mostly spherical with a smooth surface and a mass median aerodynamic diameter of 6-10 µm. Superior redispersibility was observed for microparticles containing amorphous trehalose. This study demonstrates the potential of nano-embedded microparticles for stabilization and delivery of nanogel-based delivery systems.

Peptidic Biomaterials: From Self-Assembling to Regenerative Medicine

Peptidic biomaterials represent a particularly exciting topic in regenerative medicine. Peptidic scaffolds can be specifically designed for biomimetic customization for targeted therapy. The field is at a pivotal point where preclinical research is being translated into clinics, so it is crucial to understand the theory and describe the status of this rapidly developing technology. In this review, we highlight major advantages and current limitations of self-assembling peptide-based biomaterials, and we discuss the most widely used classes of assembling peptides, describing recent and promising approaches in tissue engineering, drug delivery, and clinics. We also suggest design strategies and hurdles that still need to be overcome to fully exploit their therapeutic potential.

Unimolecular micelles of camptothecin-bonded hyperbranched star copolymers via β-thiopropionate linkage: synthesis and drug delivery

The pH- and redox-sensitive camptothecin-loaded unimolecular micelles display low cytotoxicity and controlled drug release in a sustained manner.

Extracellular vesicles and their synthetic analogues in aging and age-associated brain diseases

Multicellular organisms rely upon diverse and complex intercellular communications networks for a myriad of physiological processes. Disruption of these processes is implicated in the onset and propagation of disease and disorder, including the mechanisms of senescence at both cellular and organismal levels. In recent years, secreted extracellular vesicles (EVs) have been identified as a particularly novel vector by which cell-to-cell communications are enacted. EVs actively and specifically traffic bioactive proteins, nucleic acids, and metabolites between cells at local and systemic levels, modulating cellular responses in a bidirectional manner under both homeostatic and pathological conditions. EVs are being implicated not only in the generic aging process, but also as vehicles of pathology in a number of age-related diseases, including cancer and neurodegenerative and disease. Thus, circulating EVs-or specific EV cargoes-are being utilised as putative biomarkers of disease. On the other hand, EVs, as targeted intercellular shuttles of multipotent bioactive payloads, have demonstrated promising therapeutic properties, which can potentially be modulated and enhanced through cellular engineering. Furthermore, there is considerable interest in employing nanomedicinal approaches to mimic the putative therapeutic properties of EVs by employing synthetic analogues for targeted drug delivery. Herein we describe what is known about the origin and nature of EVs and subsequently review their putative roles in biology and medicine (including the use of synthetic EV analogues), with a particular focus on their role in aging and age-related brain diseases.

Hyaluronic Acid-Based Nanogels Produced by Microfluidics-Facilitated Self-Assembly Improves the Safety Profile of the Cationic Host Defense Peptide Novicidin

PURPOSE

Cationic host defence peptides constitute a promising class of therapeutic drug leads with a wide range of therapeutic applications, including anticancer therapy, immunomodulation, and antimicrobial activity. Although potent and efficacious, systemic toxicity and low chemical stability have hampered their commercial development. To overcome these challenges a novel nanogel-based drug delivery system was designed.

METHOD

The peptide novicidin was self-assembled with an octenyl succinic anhydride-modified analogue of hyaluronic acid, and this formulation was optimized using a microfluidics-based quality-by-design approach.

RESULTS

By applying design-of-experiment it was demonstrated that the encapsulation efficiency of novicidin (15% to 71%) and the zeta potential (-24 to -57 mV) of the nanogels could be tailored by changing the preparation process parameters, with a maximum peptide loading of 36 ± 4%. The nanogels exhibited good colloidal stability under different ionic strength conditions and allowed complete release of the peptide over 14 days. Furthermore, self-assembly of novicidin with hyaluronic acid into nanogels significantly improved the safety profile at least five-fold and six-fold when tested in HUVECs and NIH 3T3 cells, respectively, whilst showing no loss of antimicrobial activity against Escherichia coli and Staphylococcus aureus.

CONCLUSION

Formulation in nanogels could be a viable approach to improve the safety profile of host defence peptides.

Investigations on agglomeration and haemocompatibility of vitamin E TPGS surface modified berberine chloride nanoparticles

The objective of the present study is to investigate the influence of surface modification on systemic stability of NPs. Vitamin E TPGS (1% w/v) was used for surface modification of berberine chloride nanoparticles. Naked and surface modified NPs were incubated in different SBFs (pH 6.8 and 7.4) with or without bile salts and human plasma. NPs were observed for particle agglomeration and morphology by particle size analyzer and TEM, respectively. The haemocompatibility studies were conducted on developed NPs to evaluate their safety profile. The surface modified NPs were stable compared to naked NPs in different SBFs due to the steric stabilization property of vitamin E TPGS. Particle agglomeration was not seen when NPs were incubated in SBF (pH 6.8) with bile salts. No agglomeration was observed in NPs after their incubation in plasma but particle size of the naked NPs increased due to adhesion of plasma proteins. The TEM images confirmed the particle size results. DSC and FT-IR studies confirmed the coexistence of TPGS in surface modified NPs. The permissible haemolysis, LDH release, and platelet aggregation revealed that NPs were compatible for systemic administration. Thus, the study illustrated that the surface modification is helpful in the maintenance of stability of NPs in systemic conditions.

Design and in vitro evaluation of layer by layer siRNA nanovectors targeting breast tumor initiating cells

Efficient therapeutics and early detection has helped to increase breast cancer survival rates over the years. However, the recurrence of breast cancer remains to be a problem and this may be due to the presence of a small population of cells, called tumor initiating cells (TICs). Breast TICs are resistant to drugs, difficult to detect, and exhibit high self-renewal capabilities. In this study, layer by layer (LBL) small interfering RNA (siRNA) nanovectors (SNVs) were designed to target breast TICs. SNVs were fabricated using alternating layers of poly-L-lysine and siRNA molecules on gold (Au) nanoparticle (NP) surfaces. The stability, cell uptake, and release profile for SNVs were examined. In addition, SNVs reduced TIC-related STAT3 expression levels, CD44⁺/CD24⁻/EpCAM⁺ surface marker levels and the number of mammospheres formed compared to the standard transfection agent. The data from this study show, for the first time, that SNVs in LBL assembly effectively delivers STAT3 siRNA and inhibit the growth of breast TICs in vitro.

Amphiphilic biodegradable PEG-PCL-PEI triblock copolymers for FRET-capable in vitro and in vivo delivery of siRNA and quantum dots

Amphiphilic triblock copolymers represent a versatile delivery platform capable of co-delivery of nucleic acids, drugs, and/or dyes. Multifunctional cationic triblock copolymers based on poly(ethylene glycol), poly-ε-caprolactone, and polyethylene imine, designed for the delivery of siRNA, were evaluated in vitro and in vivo. Moreover, a nucleic acid-unpacking-sensitive imaging technique based on quantum dot-mediated fluorescence resonance energy transfer (QD-FRET) was established. Cell uptake in vitro was measured by flow cytometry, whereas transfection efficiencies of nanocarriers with different hydrophilic block lengths were determined in vitro and in vivo by quantitative real-time PCR. Furthermore, after the proof of concept was demonstrated by fluorescence spectroscopy/microscopy, a prototype FRET pair was established by co-loading QDs and fluorescently labeled siRNA. The hydrophobic copolymer mediated a 5-fold higher cellular uptake and good knockdown efficiency (61 ± 5% in vitro, 55 ± 18% in vivo) compared to its hydrophilic counterpart (13 ± 6% in vitro, 30 ± 17% in vivo), which exhibited poor performance. FRET was demonstrated by UV-induced emission of the acceptor dye. Upon complex dissociation, which was simulated by the addition of heparin, a dose-dependent decrease in FRET efficiency was observed. We believe that in vitro/in vivo correlation of the structure and function of polymeric nanocarriers as well as sensitive imaging functionality for mechanistic investigations are prerequisites for a more rational design of amphiphilic gene carriers.

Nanoparticle-Based Delivery of RNAi Therapeutics: Progress and Challenges

RNA interference (RNAi) is an evolutionarily conserved, endogenous process for post-transcriptional regulation of gene expression. Although RNAi therapeutics have recently progressed through the pipeline toward clinical trials, the application of these as ideal, clinical therapeutics requires the development of safe and effective delivery systems. Inspired by the immense progress with nanotechnology in drug delivery, efforts have been dedicated to the development of nanoparticle-based RNAi delivery systems. For example, a precisely engineered, multifunctional nanocarrier with combined passive and active targeting capabilities may address the delivery challenges for the widespread use of RNAi as a therapy. Therefore, in this review, we introduce the major hurdles in achieving efficient RNAi delivery and discuss the current advances in applying nanotechnology-based delivery systems to overcome the delivery hurdles of RNAi therapeutics. In particular, some representative examples of nanoparticle-based delivery formulations for targeted RNAi therapeutics are highlighted.

Self-assembling peptides improve the stability of glucagon-like peptide-1 by forming a stable and sustained complex

The multiple physiological characterizations of glucagon-like peptide-1 (GLP-1) make it a promising drug candidate for the treatment of T2DM. However, the short half-life of GLP-1 limits its clinical utility. Self-assembling peptides are presumed to wrap GLP-1 peptide, and this helps to prolong the stability of GLP-1 consequently. The aim of this study was to investigate whether self-assembling peptides could be applied to prolong the half-life of GLP-1 as sustained release preparations. In this study, five different self-assembling peptides were employed. The formation of the complexes was monitored using gel filtration and mass spectrometry and was simulated by Molecular Dynamics. Stabilization, insulin secretion stimulation, and glucose tolerance tests were performed to investigate the physiological characteristics retained by GLP-1 following complex formation with self-assembling peptides. Our findings revealed that, among the five different self-assembling peptides tested, complex of Pep-1 and GLP-1 exhibited a remarkable extension in the half-life of GLP-1. In addition, the experimental animals treated with a GLP-1/Pep-1 complex exhibited better blood glucose clearance activity over a greater duration of time than the animals treated with GLP-1 alone. Based on our results, an adjustment of the Pep-1 and GLP-1 ratios is presumed to be able to control the half-life of GLP-1 (e.g., medium-acting and long-acting). Collectively, the findings in this study suggest that the self-assembling peptide Pep-1 could serve as a powerful drug preparation tool to extend the short half-life of therapeutic peptides.

Polycation-detachable nanoparticles self-assembled from mPEG-PCL-g-SS-PDMAEMA for in vitro and in vivo siRNA delivery

Long circulation, cell internalization, endosomal escape and small interfering RNA (siRNA) release to the cytoplasm are the prerequisite considerations for siRNA delivery vectors. Herein, a kind of sheddable nanoparticles (NPs) with micelle architecture for siRNA delivery were fabricated by using an intracellular-activated polycation-detachable copolymer (PECssD), which was prepared by introducing highly reducing environment-responsive disulfide linkages between PEGylated polycaprolactone (PCL) and the grafted polycation, poly(2-dimethylaminoethyl methacrylate) (PDMAEMA). The architecture of PECssD self-assembled NPs includes a biodegradable hydrophobic PCL core, a PEG shield and a detachable comb-like polycation surface. The stable nanosized complexes of PECssD NPs with siRNA, termed PECssD/siRNA micelleplexes, were formed, which could prolong circulation, improve accumulation and retention in tumor tissue, and be favorable for internalization. In particular, the cleavage of the disulfide linkages in the intracellular microenvironment and the subsequent dissociation of the PDMAEMA/siRNA polyplexes from the PEGylated PCL cores of PECssD/siRNA micelleplexes were also confirmed, which facilitated the endosomal escape and the efficient release of siRNA. As a result, the distribution of siRNA in cytoplasm was enhanced and subsequently promoted the efficiency of siRNA in gene silencing. Furthermore, systemic administration of the NPs carrying siPlk1 (polo-like kinase 1 specific siRNA) induced a tumor-suppressing effect in the HeLa-Luc xenograft murine model. Therefore, the devised strategy of the polycation-detachable copolymer PECssD NPs could address the requirements of the multistep systemic delivery process of siRNA. The hydrophobic core of the PECssD/siRNA micelleplexes is expected to entrap antitumor drugs or other therapeutic agents for combined therapies.

Targeted delivery of antisense oligonucleotides by chemically self-assembled nanostructures

Synthetic nucleic acids have shown great potential in the treatment of various diseases. Nevertheless, the selective delivery to a target tissue has proved challenging. The coupling of nucleic acids to targeting peptides, proteins, and antibodies has been explored as an approach for their selective tissue delivery. Nevertheless, the preparation of covalently coupled peptides and proteins that can also undergo intracellular release as well as deliver more than one copy of the nucleic acid has proved challenging. Recently, we have developed a novel method for the rapid noncovalent conjugation of nucleic acids to targeting single chain antibodies (scFv) using chemically self-assembled nanostructures (CSANs). CSANs have been prepared by the self-assembly of two dihydrofolate reductase molecules (DHFR(2)) and a targeting scFv in the presence of bis-methotrexate (bis-MTX). The valency of the nanorings can be tuned from one to eight subunits, depending on the length and composition of the linker between the dihydrofolate reductase molecules. To explore their potential for the therapeutic delivery of nucleic acids as well as the ability to expand the capabilities of CSANs by incorporating smaller cyclic targeting peptides, we prepared DHFR(2) proteins fused through a flexible peptide linker to cyclic-RGD, which targets αvβ3 integrins, and a bis-MTX chemical dimerizer linked to an antisense oligonucleotide (bis-MTX-ASO) that has been shown to silence expression of eukaryotic translation initiation factor 4E (eIF4E). Monomeric and multimeric cRGD-CSANs were then prepared with bis-MTX-ASO and shown to undergo endocytosis in the breast cancer cell line, MDA-MB-231, which overexpresses αvβ3. The bis-MTX-ASO was shown to undergo endosomal escape resulting in the knock down of eIF4E with at least the same efficiency as ASO delivered by oligofectamine. The modularity, flexibility, and common method of conjugation may prove to be a useful general approach for the targeted delivery of ASOs, as well as other nucleic acids to cells.

Nanoparticles for gene delivery

Nanocarriers are a new type of nonviral gene carriers, many of which have demonstrated a broad range of pharmacological and biological properties, such as being biodegradable in the body, stimulus-responsive towards the surrounding environment, and an ability to specifically targeting certain disease sites. By summarizing some main types of nanocarriers, this Concept considers the current status and possible future directions of the potential clinical applications of multifunctional nanocarriers, with primary attention on the combination of such properties as biodegradability, targetability, transfection ability, and stimuli sensitivity.

Imaging mRNA expression levels in living cells with PNA·DNA binary FRET probes delivered by cationic shell-crosslinked nanoparticles

Optical imaging of gene expression through the use of fluorescent antisense probes targeted to the mRNA has been an area of great interest. The main obstacles to developing highly sensitive antisense fluorescent imaging agents have been the inefficient intracellular delivery of the probes and high background signal from unbound probes. Binary antisense probes have shown great promise as mRNA imaging agents because a signal can only occur if both probes are bound simultaneously to the mRNA target site. Selecting an accessible binding site is made difficult by RNA folding and protein binding in vivo and the need to bind two probes. Even more problematic, has been a lack of methods for efficient cytoplasmic delivery of the probes that would be suitable for eventual applications in vivo in animals. Herein we report the imaging of iNOS mRNA expression in live mouse macrophage cells with PNA·DNA binary FRET probes delivered by a cationic shell crosslinked knedel-like nanoparticle (cSCK). We first demonstrate that FRET can be observed on in vitro transcribed mRNA with both the PNA probes and the PNA·DNA hybrid probes. We then demonstrate that the FRET signal can be observed in live cells when the hybrid probes are transfected with the cSCK, and that the strength of the FRET signal is sequence specific and depends on the mRNA expression level.

Nuclease-resistant DNA via high-density packing in polymeric micellar nanoparticle coronas

Herein, we describe a polymeric micellar nanoparticle capable of rendering nucleic acids resistant to nuclease digestion. This approach relies on utilizing DNA as the polar headgroup of a DNA-polymer amphiphile in order to assemble well-defined, discrete nanoparticles. Dense packing of DNA in the micelle corona allows for hybridization of complementary oligonucleotides while prohibiting enzymatic degradation. We demonstrate the preparation, purification, and characterization of the nanoparticles, then describe their resistance to treatment with endo- and exonucleases including snake-venom phosphodiesterase (SVP), a common, general DNA digestion enzyme.

Dendrimers for siRNA Delivery

Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.

Molecular targeting of liposomal nanoparticles to tumor microenvironment

Liposomes are biodegradable and can be used to deliver drugs at a much higher concentration in tumor tissues than in normal tissues. Both passive and active drug delivery by liposomal nanoparticles can significantly reduce the toxic side effects of anticancer drugs and enhance the therapeutic efficacy of the drugs delivered. Active liposomal targeting to tumors is achieved by recognizing specific tumor receptors through tumor-specific ligands or antibodies coupled onto the surface of the liposomes, or by stimulus-sensitive drug carriers such as acid-triggered release or enzyme-triggered drug release. Tumors are often composed of tumor cells and nontumor cells, which include endothelial cells, pericytes, fibroblasts, stromal, mesenchymal cells, innate, and adaptive immune cells. These nontumor cells thus form the tumor microenvironment, which could be targeted and modified so that it is unfavorable for tumor cells to grow. In this review, we briefly summarized articles that had taken advantage of liposomal nanoparticles as a carrier to deliver anticancer drugs to the tumor microenvironment, and how they overcame obstacles such as nonspecific uptake, interaction with components in blood, and toxicity. Special attention is devoted to the liposomal targeting of anticancer drugs to the endothelium of tumor neovasculature, tumor associated macrophages, fibroblasts, and pericytes within the tumor microenvironment.

Solid formulation of cell-penetrating peptide nanocomplexes with siRNA and their stability in simulated gastric conditions

Cell-penetrating peptides (CPPs) are short cationic peptides that have been extensively studied as drug delivery vehicles for proteins, nucleic acids and nanoparticles. However, the formulation of CPP-based therapeutics into different pharmaceutical formulations and their stability in relevant biological environments have not been given the same attention. Here, we show that a newly developed CPP, PepFect 14 (PF14), forms non-covalent nanocomplexes with short interfering RNA (siRNA), which are able to elicit efficient RNA-interference (RNAi) response in different cell-lines. RNAi effect is obtained at low siRNA doses with a unique kinetic profile. Furthermore, the solid dispersion technique is utilized to formulate PF14/siRNA nanocomplexes into solid formulations that are as active as the freshly prepared nanocomplexes in solution. Importantly, the nanocomplexes are stable and active in mediating RNAi response after incubation with simulated gastric fluid (SGF) that is highly acidic. These results demonstrate the activity of PF14 in delivering and protecting siRNA in different pharmaceutical forms and biological environments.

Lyophilised ready-to-use formulations of PEG-PCL-PEI nano-carriers for siRNA delivery

The purpose of the present study was to transfer aqueous PEG-PCL-PEI nano-suspensions into dry ready-to-use formulations, suitable for delivery of siRNA. Therefore, freshly prepared nano-suspensions were lyophilised with glucose as lyoprotectant. Firstly, the required glucose concentration for sufficient stabilisation of unloaded carriers was determined via dynamic light scattering. Morphology of fresh and rehydrated carriers was visualised by cryogenic scanning electron microscopy. Subsequently, the feasibility of siRNA loading before and after lyophilisation was investigated. For both strategies complex diameter and in vitro transfection efficiency were determined and correlated to freshly prepared samples. Hydrodynamic diameter (95.2 ± 1.4 nm) and size distribution (0.132 ± 0.019) of unloaded nano-suspension were restored after rehydration by addition of ≥ 1.5% of glucose before lyophilisation. Moreover, after loading of rehydrated carriers with siRNA, no significant difference in complex size was observed as compared to freshly prepared ones. Stabilisation of pre-formed carrier/siRNA complexes during lyophilisation is feasible at elevated N/P (e.g. 20) and glucose concentrations above 5%. As determined via real-time-PCR, lyophilised samples were as active as freshly prepared ones regarding transfection efficiency. In conclusion, lyophilisation is an effective technique to produce physically stable PEG-PCL-PEI formulations. These general findings may be applicable to further particulate gene delivery systems to shelf ready-to-use formulations.

Facial amphipathic deoxycholic acid-modified polyethyleneimine for efficient MMP-2 siRNA delivery in vascular smooth muscle cells

Clinical applications of RNA interference-based therapeutics such as small interfering RNAs (siRNAs) have been limited mainly due to low intracellular delivery efficiency in vitro and in vivo. In this study, facially amphipathic deoxycholic acid (DA)-modified polyethyleneimine (PEI(1.8)) (DA-PEI(1.8)) was synthesized and used as a potent carrier system for siRNA targeted against matrix metalloproteinase-2 (MMP-2) to inhibit the migration of vascular smooth muscle cells (SMCs), which is the major pathomechanism in the development of atherosclerosis and restenosis after arterial injury. A representative facial amphipathic bile acid DA having a high membrane permeability was conjugated to the terminal amine groups of the low molecular weight PEI(1.8) via amide bonds. The DA-PEI(1.8) conjugates formed self-assembled nanoparticles with siRNA molecules in an aqueous phase and the DA-PEI(1.8)/siRNA polyplexes became stabilized and condensed as particle incubation time increased from 0 to 4h. Both cellular internalization and target gene silencing were enhanced as the DA-PEI(1.8)/siRNA polyplexes stabilized. When vascular SMCs were transfected with MMP-2 siRNA, the DA-PEI(1.8)/siRNA polyplex formulation led to a significant decrease in MMP-2 gene expression, resulting in the suppression of cell migration. These results suggest that the DA-PEI(1.8)/MMP-2 siRNA delivery system may be useful in anti-restenotic treatment for various vasculoproliferative disorders such as atherosclerosis, in-stent restenosis, and vein graft failure.