Cationic and PEGylated Amphiphilic Cyclodextrins: Co-Formulation Opportunities for Neuronal Sirna Delivery

Advances in carrier-delivered small interfering RNA based therapeutics for treatment of neurodegenerative diseases

Neurodegenerative diseases are devastating diseases that severely affect the health of people all over the world. RNA therapies have become one of the most promising critical drug treatments for neurodegenerative diseases due to their excellent gene and protein editing effects. However, the successful transport of RNA via the systemic route to the central nervous system remains one of the major obstacles in treating neurodegenerative diseases. This review will focus on therapeutic RNA that can successfully overcome the blood-brain barrier (BBB), with particular attention to small interfering RNAs (siRNAs), focusing on different types of neurodegenerative disease treatment strategies and accelerating their translation into clinical practice.

The Many Faces of Cyclodextrins within Self-Assembling Polymer Nanovehicles: From Inclusion Complexes to Valuable Structural and Functional Elements

Most chemotherapeutic agents are poorly soluble in water, have low selectivity, and cannot reach the tumor in the desired therapeutic concentration. On the other hand, sensitive hydrophilic therapeutics like nucleic acids and proteins suffer from poor bioavailability and cell internalization. To solve this problem, new types of controlled release systems based on nano-sized self-assemblies of cyclodextrins able to control the speed, timing, and location of therapeutic release are being developed. Cyclodextrins are macrocyclic oligosaccharides characterized by a high synthetic plasticity and potential for derivatization. Introduction of new hydrophobic and/or hydrophilic domains and/or formation of nano-assemblies with therapeutic load extends the use of CDs beyond the tried-and-tested CD-drug host-guest inclusion complexes. The recent advances in nano drug delivery have indicated the benefits of the hybrid amphiphilic CD nanosystems over individual CD and polymer components. This review provides a comprehensive overview of the most recent advances in the design of CDs self-assemblies and their use for delivery of a wide range of therapeutic molecules. It aims to offer a valuable insight into the many roles of CDs within this class of drug nanocarriers as well as current challenges and future perspectives.

Use of Protamine in Nanopharmaceuticals-A Review

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

Optimization of PEGylated KL4 Peptide for siRNA Delivery with Improved Pulmonary Tolerance

Pulmonary delivery of small interfering RNA (siRNA) is a promising therapeutic strategy for treating various respiratory diseases but an effective carrier for the delivery of siRNA into the cells of the lungs and a robust gene-silencing effect is still lacking. Previously, we reported that the KL4 peptide, a synthetic cationic peptide with a repeating KLLLL sequence, can mediate effective siRNA transfection in lung epithelial cells but its high hydrophobic leucine content, and hence poor water solubility, limits its application as a delivery vector. Here, we show that the covalent attachment of monodisperse poly(ethylene glycol) (PEG) improves the solubility of KL4 and the uptake of its complex with siRNA into lung epithelial cells, such that very robust silencing is produced. All PEGylated KL4 peptides, with PEG length varying between 6 and 24 monomers, could bind and form nanosized complexes with siRNA, but the interaction between siRNA and peptides became weaker as the PEG chain length increased. All PEGylated KL4 peptides exhibited satisfactory siRNA transfection efficiency on three human lung epithelial cell lines, including A549 cells, Calu-3 cells, and BEAS-2B cells. The PEG₁₂KL4 peptide, which contains 12 monomers of PEG, was optimal for siRNA delivery and also demonstrated a low risk of inflammatory response and toxicity in vivo following pulmonary administration.

Cyclodextrin-Based Functional Glyconanomaterials

Cyclodextrins (CDs) have long occupied a prominent position in most pharmaceutical laboratories as "off-the-shelve" tools to manipulate the pharmacokinetics of a broad range of active principles, due to their unique combination of biocompatibility and inclusion abilities. The development of precision chemical methods for their selective functionalization, in combination with "click" multiconjugation procedures, have further leveraged the nanoscaffold nature of these oligosaccharides, creating a direct link between the glyco and the nano worlds. CDs have greatly contributed to understand and exploit the interactions between multivalent glycodisplays and carbohydrate-binding proteins (lectins) and to improve the drug-loading and functional properties of nanomaterials through host-guest strategies. The whole range of capabilities can be enabled through self-assembly, template-assisted assembly or covalent connection of CD/glycan building blocks. This review discusses the advancements made in this field during the last decade and the amazing variety of functional glyconanomaterials empowered by the versatility of the CD component.

Potential therapeutic application of dendrimer/cyclodextrin conjugates with targeting ligands as advanced carriers for gene and oligonucleotide drugs

Despite the recent approval of some gene medicines and nucleic acid drugs, further improvement of delivery techniques for these drugs is strongly required. Several delivery technologies for these drugs have been developed, in other words, viral and two types of nonviral (lipofection and polyfection) vectors. Among the polyfection system, the potential use of various cyclodextrin (CyD) derivatives and CyD-appended polymers as carriers for gene and nucleic acid drugs has been demonstrated. The polyamidoamine dendrimer (G3) conjugates with α-CyD (α-CDE (G3)) have been reported to possess noteworthy properties as DNA and nucleic acid drugs carriers. This review will focus on the attempts to develop such cell-specific drug carriers by preparing polyethylene glycol, galactose, lactose, mannose, fucose and folic acid-appended α-CDEs as tissue and cell-selective carriers of gene and nucleic acid drugs.

Amphiphilic cyclodextrin nanoparticles

Cyclodextrins are cyclic oligosaccharides obtained by enzymatic digestion of starch. The α-, β- and γ- cyclodextrins contain respectively 6, 7 and 8 glucopyranose units, with primary and secondary hydroxyl groups located on the narrow and wider rims of a truncated cone shape structure. Such structure is that of a hydrophobic inner cavity with a hydrophilic outer surface allowing to interact with a wide range of molecules like ions, protein and oligonucleotides to form inclusion complexes. Many cyclodextrin applications in the pharmaceutical area have been widely described in the literature due to their low toxicity and low immunogenicity. The most important is to increase the solubility of hydrophobic drugs in water. Chemically modified cyclodextrin derivatives have been synthesized to enhance their properties and more specifically their pharmacological activity. Among these, amphiphilic derivatives were designed to build organized molecular structures, through selfassembling systems or by incorporation in lipid membranes, expected to improve the vectorization in the organism of the drug-containing cyclodextrin cavities. These derivatives can form a variety of supramolecular structures such as micelles, vesicles and nanoparticles. The purpose of this review is to summarize applications of amphiphilic cyclodextrins in different areas of drug delivery, particularly in protein and peptide drug delivery and gene delivery. The article highlights important amphiphilic cyclodextrin applications in the design of novel delivery systems like nanoparticles.

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

In the field of host-guest chemistry, some of the most widely used hosts are probably cyclodextrins (CDs). As CDs are able to increase the water solubility of numerous drugs by inclusion into their hydrophobic cavity, they have been widespread used to develop numerous pharmaceutical formulations. Nevertheless, CDs are also able to interact with endogenous substances that originate from an organism, tissue or cell. These interactions can be useful for a vast array of topics including cholesterol manipulation, treatment of Alzheimer's disease, control of pathogens, etc. In addition, the use of natural CDs offers the great advantage of avoiding or reducing the use of common petroleum-sourced drugs. In this paper, the general features and applications of CDs have been reviewed as well as their interactions with isolated biomolecules leading to the formation of inclusion or exclusion complexes. Finally, some potential medical applications are highlighted throughout several examples.

Carbohydrate-based amphiphilic nano delivery systems for cancer therapy

Nanoparticles (NPs) are novel drug delivery systems that have been attracting more and more attention in recent years, and have been used for the treatment of cancer, infection, inflammation and other diseases. Among the numerous classes of materials employed for constructing NPs, organic polymers are outstanding due to the flexibility of design and synthesis and the ease of modification and functionalization. In particular, NP based amphiphilic polymers make a great contribution to the delivery of poorly-water soluble drugs. For example, natural, biocompatible and biodegradable products like polysaccharides are widely used as building blocks for the preparation of such drug delivery vehicles. This review will detail carbohydrate based amphiphilic polymeric systems for cancer therapy. Specifically, it focuses on the nature of the polymer employed for the preparation of targeted nanocarriers, the synthetic methods, as well as strategies for the application and evaluation of biological activity. Applications of the amphiphilic polymer systems include drug delivery, gene delivery, photosensitizer delivery, diagnostic imaging and specific ligand-assisted cellular uptake. As a result, a thorough understanding of the relationship between chemical structure and biological properties facilitate the optimal design and rational clinical application of the resulting carbohydrate based nano delivery systems for cancer therapy.

Effective combination treatment of lung cancer cells by single vehicular delivery of siRNA and different anticancer drugs

In recent years, lung cancer has become one of the fastest growing cancers in the world. Thus, the development of efficient combination therapy to treat lung cancer has attracted significant attention in the cancer therapy field. In this article, we developed a single vehicle drug delivery system, based on quantum dot (QD) nanoparticles, to deliver small interfering RNA (siRNA; target Bcl-2) and different anticancer drugs (carboplatin, paclitaxel, and doxorubicin) simultaneously for treating A549 lung cancer cells efficiently by combination therapy. The QD nanoparticles were conjugated with l-arginine (l-Arg) and different kinds of hydroxypropyl-cyclodextrins (HP-α-CDs, HP-β-CDs, and HP-γ-CDs) on the surface to form the delivery nanocarriers (QD nanocarriers). They were able to not only bind and transport the siRNA through electrostatic interactions with l-Arg residues but also accommodate various disparate anticancer drugs using different HP-CD modifications. Compared with free drug treatments, the use of QD nanocarriers to deliver Bcl-2 siRNA and different anticancer drugs simultaneously exerted a threefold to fourfold increase in cytotoxicity in A549 cells, which greatly improved the treatment efficacy through combined action. Furthermore, the QD nanocarriers could be used as a probe for real-time imaging of the drug delivery and release because of their strong fluorescence properties. These findings indicate that multifunctional QD nanocarriers hold great promise as a powerful tool for combination therapy for lung cancer.

Nanoparticle-mediated siRNA delivery assessed in a 3D co-culture model simulating prostate cancer bone metastasis

siRNA has emerged as a potential therapeutic for the treatment of prostate cancer but effective delivery remains a major barrier to its clinical application. This study aimed to develop and characterise a 3D in vitro co-culture model to simulate prostate cancer bone metastasis and to assess the ability of the model to investigate nanoparticle-mediated siRNA delivery and gene knockdown. PC3 or LNCaP prostate cancer cells were co-cultured with hFOB 1.19 osteoblast cells in 2D on plastic tissue culture plates and in 3D on collagen scaffolds mimicking the bone microenvironment. To characterise the co-culture model, cell proliferation, enzyme secretion and the utility of two different gene delivery vectors to mediate siRNA uptake and gene knockdown were assessed. Cell proliferation was reduced by∼50% by day 7 in the co-culture system relative to monoculture (PC3 and LNCaP co-cultures, in 2D and 3D) and an enhanced level of MMP9 (a marker of bone metastasis) was secreted into the media (1.2-4-fold increase depending on the co-culture system). A cationic cyclodextrin gene delivery vector proved significantly less toxic in the co-culture system relative to the commercially available vector Lipofectamine 2000(®). In addition, knockdown of both the GAPDH gene (minimum 15%) and RelA subunit of the NF-κB transcription factor (minimum 20%) was achieved in 2D and 3D cell co-cultures. Results indicate that the prostate cancer-osteoblast in vitro co-culture model was more physiologically relevant vs the monoculture. This model has the potential to help improve the design and efficacy of gene delivery formulations, to more accurately predict in vivo performance and, therefore, to reduce the risk of product failure in late-stage clinical development.

Short interfering RNA therapeutics: nanocarriers, prospects and limitations

Since the first experiment depicting gene inhibition using RNA interference mechanism, extensive research has been carried out to design targeted delivery systems that use short interfering RNAs (siRNAs) for gene expression regulation. Although several siRNAs loaded nanoparticle systems have reached clinical trial stage, cellular uptake, reticuloendothelial entrapment and endosomal escape still limit the efficacy of these drugs considerably. This review discusses about the RNA interference mechanism, nanostructures being used as non-viral vectors for targeted delivery, limitations of the common delivery systems and the current siRNA-loaded nanoparticle formulations undergoing clinical testing.

Anisamide-targeted gold nanoparticles for siRNA delivery in prostate cancer - synthesis, physicochemical characterisation and in vitro evaluation

Metastatic prostate cancer is a leading cause of cancer-related death in men and current chemotherapies are largely inadequate in terms of efficacy and toxicity. Hence improved treatments are required. The application of siRNA as a cancer therapeutic holds great promise. However, translation of siRNA into the clinic is dependent on the availability of an effective delivery system. Gold nanoparticles (AuNPs) are known to be effective and non-toxic siRNA delivery agents. In this study, a stable gold nanosphere coated with poly(ethylenimine) (PEI) was prepared to yield PEI capped AuNPs (Au-PEI). The PEI was further conjugated with the targeting ligand anisamide (AA, is known to bind to the sigma receptor overexpressed on the surface of prostate cancer cells) to produce an anisamide-targeted nanoparticle (Au-PEI-AA). The resulting untargeted and targeted nanoparticles (Au-PEI and Au-PEI-AA respectively) were positively charged and efficiently complexed siRNA. Au-PEI-AA mediated siRNA uptake into PC3 prostate cancer cells via binding to the sigma receptor. In addition, the Au-PEI-AA·siRNA complexes resulted in highly efficient knockdown of the RelA gene (∼70%) when cells were transfected in serum-free medium. In contrast, no knockdown was observed in the presence of serum, suggesting that adsorption of serum proteins inhibits the binding of the anisamide moiety to the sigma receptor. This study provides (for the first time) proof of principle that anisamide-labelled gold nanoparticles can target the sigma receptor. Further optimisation of the formulation to increase serum stability will enhance its potential to treat prostate cancer.

A novel, anisamide-targeted cyclodextrin nanoformulation for siRNA delivery to prostate cancer cells expressing the sigma-1 receptor

Prostate cancer is a leading cause of cancer-related death in men and RNA interference (RNAi) has emerged as a potential therapeutic option. However, the absence of a safe and specific delivery vector remains a major obstacle to the clinical application of RNAi. Cyclodextrin derivatives are known to be efficient delivery systems with low toxicity in a variety of cell types. In this study, a cationic cyclodextrin derivative was synthesized to complex siRNA. The nanoparticle was then further modified by exploiting the ability of the β-cyclodextrin cavity to form an inclusion complex with the hydrophobic molecule adamantane. PEGylated adamantane derivatives were synthesized with and without the anisamide-targeting ligand on the terminal end of the PEG chain. Anisamide is known to bind specifically to the sigma receptor which is overexpressed on the surface of prostate cancer cells. The resulting nanocomplexes were slightly cationic and less than 300 nm in size. They successfully protected siRNA from serum-induced nuclease degradation and were non-toxic to prostate cancer cells. In addition, the targeted nanoparticles mediated high levels of siRNA cellular uptake and corresponding PLK1 gene knockdown in prostate cancer cells in vitro. To our knowledge, this is the first time that the ability of cyclodextrins to form inclusion complexes with adamantane derivatives has been exploited for the targeted delivery of siRNA to prostate cancer cells via the sigma receptor.

Current development of targeted oligonucleotide-based cancer therapies: Perspective on HER2-positive breast cancer treatment

This Review discusses the various types of non-coding oligonucleotides, which have garnered extensive interest as new alternatives for targeted cancer therapies over small molecule inhibitors and monoclonal antibodies. These oligonucleotides can target any hallmark of cancer, no longer limited to so-called "druggable" targets. Thus, any identified gene that plays a key role in cancer progression or drug resistance can be exploited with oligonucleotides. Among them, small-interfering RNAs (siRNAs) are frequently utilized for gene silencing due to the robust and well established mechanism of RNA interference. Despite promising advantages, clinical translation of siRNAs is hindered by the lack of effective delivery platforms. This Review provides general criteria and consideration of nanoparticle development for systemic siRNA delivery. Different classes of nanoparticle candidates for siRNA delivery are discussed, and the progress in clinical trials for systemic cancer treatment is reviewed. Lastly, this Review presents HER2 (human epidermal growth factor receptor type 2)-positive breast cancer as one example that could benefit significantly from siRNA technology. How siRNA-based therapeutics can overcome cancer resistance to such therapies is discussed.

Surface-mediated delivery of siRNA from fibrin hydrogels for knockdown of the BMP-2 binding antagonist noggin

Antagonists and inhibitory molecules responsible for maintaining tissue homeostasis can present a significant barrier to healing when tissue engineering/regenerative medicine strategies are employed. One example of this situation is the up-regulation of antagonists such as noggin in response to increasing concentrations of bone morphogenetic protein-2 (BMP-2) present from endogenous bone repair processes or delivered exogenously from biomaterials (synthetic bone grafts). While recombinant human (rh)BMP-2 delivered from synthetic bone grafts has been shown to be an effective alternative to autografts and allografts, the supraphysiological doses of rhBMP-2 have led to clinically-adverse side effects. The high rhBMP-2 dosage may be required, in part, to overcome the presence of antagonists such as noggin. Small interfering RNA (siRNA) is an appealing approach to overcome this problem because it can knock-down antagonists or inhibitory molecules in a temporary manner. Here, we conducted fundamental studies on the delivery of siRNA from material surfaces as a means to knock-down antagonists like noggin. Non-viral cationic lipid (Lipofectamine)-siRNA complexes were delivered from a fibrin hydrogel surface to MC3T3-E1 preosteoblasts that were treated with a supraphysiological dose of rhBMP-2 to achieve noggin mRNA expression levels higher than cells naïve to rhBMP-2. Confocal microscopy and flow cytometry showed intracellular uptake of siRNA in over 98% of MC3T3-E1 cells after 48 h. Doses of 0.5 and 1 μg noggin siRNA were able to significantly reduce noggin mRNA to levels equivalent to those in MC3T3-E1 cells not exposed to rhBMP-2 with no effects on cell viability.

STATEMENT OF SIGNIFICANCE

Small interfering RNA (siRNA) has been considered for treatment of diseases ranging from Alzheimer's to cancer. However, the ability to use siRNA in conjunction with biomaterials to direct tissue regeneration processes has received relatively little attention. Using the bone morphogenetic protein 2 antagonist, noggin, as a model, this research describes an approach to knock-down molecules that are inhibitory to desired regenerative pathways at the mRNA level via siRNA delivery from a hydrogel surface. Interactions between the material (fibrin) surface and polycation-siRNA complexes, release of the siRNA from the material surface, high levels of cellular uptake/internalization of siRNA, and significant knockdown of the targeting (noggin) mRNA are demonstrated. Broader future applications include those to nerve regeneration, cardiovascular tissue engineering, directing (stem) cell behavior, and mitigating inflammatory responses to materials.

Early-stage development of novel cyclodextrin-siRNA nanocomplexes allows for successful postnebulization transfection of bronchial epithelial cells

BACKGROUND

Successful delivery of small interfering RNA (siRNA) to the lungs remains hampered by poor intracellular delivery, vector-mediated cytotoxicity, and an inability to withstand nebulization. Recently, a novel cyclodextrin (CD), SC12CDClickpropylamine, consisting of distinct lipophilic and cationic subunits, has been shown to transfect a number of cell types. However, the suitability of this vector for pulmonary siRNA delivery has not been assessed to date. To address this, a series of high-content analysis (HCA) and postnebulization assays were devised to determine the potential for CD-siRNA delivery to the lungs.

METHODS

SC12CDClickpropylamine-siRNA mass ratios (MRs) were examined for size and zeta potential. In-depth analysis of nanocomplex uptake and toxicity in Calu-3 bronchial epithelial cells was examined using IN Cell(®) HCA assays. Nebulized SC12CDClickpropylamine nanocomplexes were assessed for volumetric median diameter (VMD) and fine particle fraction (FPF) and compared with saline controls. Finally, postnebulization stability was determined by comparing luciferase knockdown elicited by SC12CDClickpropylamine nanocomplexes before and after nebulization.

RESULTS

SC12CDClickpropylamine-siRNA complexation formed cationic nanocomplexes of ≤200 nm in size depending on the medium and led to significantly higher levels of siRNA associated with Calu-3 cells compared with RNAiFect-siRNA-treated cells at all MRs (p<0.001, n=3×4), with evidence of toxicity only at MRs 50-100. Nebulization of SC12CDClickpropylamine nanocomplexes using the Aeroneb(®) Pro resulted in VMDs of ∼4 μm and FPFs of ∼57% at all MRs. SC12CDClickpropylamine-siRNA-mediated luciferase knockdown was found to be 39.8±3.6% at MR=20 before and 35.6±4.55% after nebulization, comparable to results observed using unnebulized commercial transfection reagent, RNAiFect.

CONCLUSIONS

SC12CDClickpropylamine nanocomplexes can be effectively nebulized for pulmonary delivery of siRNA using Aeroneb technology to mediate knockdown in airway cells. To the best of our knowledge, this is the first study examining the suitability of SC12CDClickpropylamine-siRNA nanocomplexes for pulmonary delivery. Furthermore, this work provides an integrated nanomedicine-device combination for future in vitro and in vivo preclinical and clinical studies of inhaled siRNA therapeutics.

The use of collagen-based scaffolds to simulate prostate cancer bone metastases with potential for evaluating delivery of nanoparticulate gene therapeutics

Prostate cancer bone metastases are a leading cause of cancer-related death in men with current treatments offering only marginally improved rates of survival. Advances in the understanding of the genetic basis of prostate cancer provide the opportunity to develop gene-based medicines capable of treating metastatic disease. The aim of this work was to establish a 3D cell culture model of prostate cancer bone metastasis using collagen-based scaffolds, to characterise this model, and to assess the potential of the model to evaluate delivery of gene therapeutics designed to target bone metastases. Two prostate cancer cell lines (PC3 and LNCaP) were cultured in 2D standard culture and compared to 3D cell growth on three different collagen-based scaffolds (collagen and composites of collagen containing either glycosaminoglycan or nanohydroxyapatite). The 3D model was characterised for cell proliferation, viability and for matrix metalloproteinase (MMP) enzyme and Prostate Specific Antigen (PSA) secretion. Chemosensitivity to docetaxel treatment was assessed in 2D in comparison to 3D. Nanoparticles (NPs) containing siRNA formulated using a modified cyclodextrin were delivered to the cells on the scaffolds and gene silencing was quantified. Both prostate cancer cell lines actively infiltrated and proliferated on the scaffolds. Cell culture in 3D resulted in reduced levels of MMP1 and MMP9 secretion in PC3 cells. In contrast, LNCaP cells grown in 3D secreted elevated levels of PSA, particularly on the scaffold composed of collagen and glycosaminoglycans. Both cell lines grown in 3D displayed increased resistance to docetaxel treatment. The cyclodextrin.siRNA nanoparticles achieved cellular uptake and knocked down the endogenous GAPDH gene in the 3D model. In conclusion, development of a novel 3D cell culture model of prostate cancer bone metastasis has been initiated resulting, for the first time, in the successful delivery of gene therapeutics in a 3D in vitro model. Further enhancement of this model will help elucidate the pathogenesis of prostate cancer and also accelerate the design of effective therapies which can penetrate into the bone microenvironment for prostate cancer therapy.

Synthesis and characterization of rabies virus glycoprotein-tagged amphiphilic cyclodextrins for siRNA delivery in human glioblastoma cells: in vitro analysis

In man brain cancer is an aggressive, malignant form of tumour, it is highly infiltrative in nature, is associated with cellular heterogeneity and affects cerebral hemispheres of the brain. Current drug therapies are inadequate and an unmet clinical need exists to develop new improved therapeutics. The ability to silence genes associated with disease progression by using short interfering RNA (siRNA) presents the potential to develop safe and effective therapies. In this work, in order to protect the siRNA from degradation, promote cell specific uptake and enhance gene silencing efficiency, a PEGylated cyclodextrin (CD)-based nanoparticle, tagged with a CNS-targeting peptide derived from the rabies virus glycoprotein (RVG) was formulated and characterized. The modified cyclodextrin derivatives were synthesized and co-formulated to form nanoparticles containing siRNA which were analysed for size, surface charge, stability, cellular uptake and gene-knockdown in brain cancer cells. The results identified an optimised co-formulation prototype at a molar ratio of 1:1.5:0.5 (cationic cyclodextrin:PEGylated cyclodextrin:RVG-tagged PEGylated cyclodextrin) with a size of 281 ± 39.72 nm, a surface charge of 26.73 ± 3 mV, with efficient cellular uptake and a 27% gene-knockdown ability. This CD-based formulation represents a potential nanocomplex for systemic delivery of siRNA targeting brain cancer.

Nanoparticles and the blood-brain barrier: advancing from in-vitro models towards therapeutic significance

The blood-brain barrier is a unique cell-based restrictive barrier that prevents the entry of many substances, including most therapeutics, into the central nervous system. A wide range of nanoparticulate delivery systems have been investigated with the aim of targeting therapeutics (drugs, nucleic acids, proteins) to the brain following administration by various routes. This review provides a comprehensive description of the design and formulation of these nanoparticles including the rationale behind individual approaches. In addition, the ability of currently available in-vitro BBB models to accurately predict the in-vivo performance of targeted nanoparticles is critically assessed.

PEGylated cyclodextrins as novel siRNA nanosystems: correlations between polyethylene glycol length and nanoparticle stability

Silencing disease-related genes in the central nervous system (CNS) using short interfering RNA (siRNA) holds great promise for treating neurological disorders. Yet, delivery of RNAi therapeutics to the brain poses major challenges to non-viral systems, especially when considering systemic administration. Cationic nanoparticles have been widely investigated for siRNA delivery, but the tendency of these to aggregate in physiological environments limits their intravenous application. Thus, strategies to increase the stability of nanoparticles have been developed. Here, we investigated the ability of modified cationic amphiphilic or PEGylated amphiphilic cyclodextrins (CD) to formulate stable CD.siRNA nanoparticles. To this end, we describe a simple method for post-modification of pre-formed cationic CD.siRNA nanoparticles at their surface using PEGylated CDs of different PEG lengths. PEGylated CD.siRNA nanoparticles presented reduced surface charges and increased stability in physiological salt conditions. Stability of PEGylated CD.siRNA nanoparticles in vitro increased with both PEG length and PEG density at the surface. Furthermore, in a comparative pharmacokinetic study, increased systemic exposure and reduced clearance were achieved with CD-formulations when compared to naked siRNAs. However, no significant differences were observed among non-PEGylated and PEGylated CD.siRNAs suggesting that longer PEG lengths might be required for improving stability in vivo.