Characterisation of cationic amphiphilic cyclodextrins for neuronal delivery of siRNA: Effect of reversing primary and secondary face modifications

Targeted Delivery Methods for Anticancer Drugs

Simple Summary

The current main technological strategies for the delivery of anticancer drugs are discussed herein. This comprehensive review may help researchers design suitable delivery systems.

Abstract

Several drug-delivery systems have been reported on and often successfully applied in cancer therapy. Cell-targeted delivery can reduce the overall toxicity of cytotoxic drugs and increase their effectiveness and selectivity. Besides traditional liposomal and micellar formulations, various nanocarrier systems have recently become the focus of developmental interest. This review discusses the preparation and targeting techniques as well as the properties of several liposome-, micelle-, solid-lipid nanoparticle-, dendrimer-, gold-, and magnetic-nanoparticle-based delivery systems. Approaches for targeted drug delivery and systems for drug release under a range of stimuli are also discussed.

Cyclodextrins in the antiviral therapy

The main antiviral drug-cyclodextrin interactions, changes in physicochemical and physiological properties of the most commonly used virucides are summarized. The potential complexation of antiviral molecules against the SARS-Cov2 also pointed out the lack of detailed information in designing effective and general medicines against viral infections. The principal problem of the current molecules is the 3D structures of the currently active compounds. Improving the solubility or bioavailability of antiviral molecules is possible, however, there is no universal solution, and the complexation experiments dominantly use the already approved cyclodextrin derivatives. This review discusses the basic properties of the different cyclodextrin derivatives, their potential in antiviral formulations, and the prevention and treatment of viral infections. The biologically active new cyclodextrin derivatives are also discussed.

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.

Localised non-viral delivery of nucleic acids for nerve regeneration in injured nervous systems

Axons damaged by traumatic injuries are often unable to spontaneously regenerate in the adult central nervous system (CNS). Although the peripheral nervous system (PNS) has some regenerative capacity, its ability to regrow remains limited across large lesion gaps due to scar tissue formation. Nucleic acid therapy holds the potential of improving regeneration by enhancing the intrinsic growth ability of neurons and overcoming the inhibitory environment that prevents neurite outgrowth. Nucleic acids modulate gene expression by over-expression of neuronal growth factor or silencing growth-inhibitory molecules. Although in vitro outcomes appear promising, the lack of efficient non-viral nucleic acid delivery methods to the nervous system has limited the application of nucleic acid therapeutics to patients. Here, we review the recent development of efficient non-viral nucleic acid delivery platforms, as applied to the nervous system, including the transfection vectors and carriers used, as well as matrices and scaffolds that are currently used. Additionally, we will discuss possible improvements for localised nucleic acid delivery.

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.

Cyclodextrin-siRNA conjugates as versatile gene silencing agents

Functional siRNAs (luciferase and PLK1) have been conjugated to β-cyclodextrin and the ability of the conjugates to retain gene knockdown activity has been assessed by delivery to cancer cell lines using various formulations. Initially two formulations used complexation with polycations, namely Lipofectamine 2000 and an amphiphilic polycationic cyclodextrin. Gene knockdown results for human glioblastoma cells (U87) and prostate cancer cells (PC3, DU145) showed that conjugation to the cyclodextrin did not reduce gene silencing by the RNA. A third mode of delivery involved formation of targeted nanoparticles in which the conjugate was first complexed with adamantyl-PEG-ligands (targeting ligand RVG peptide or dianisamide) by adamantyl inclusion in the cyclodextrin cavities of the conjugates, followed by charge neutralisation with the cationic polymer chitosan. Enhanced knockdown was achieved by these ligand-targeted formulations. In summary, while this study illustrated the gene silencing efficacy of a simple cyclodextrin-siRNA conjugate it is envisaged that future studies will explore the use of conjugates with a modified cyclodextrin which would be self-delivering. Detailed data such as stability, lysosomal escape etc. will then be reported for each conjugate, since this will be appropriate for conjugates which are intended to exploit, rather than merely demonstrate, the concept. The present paper was intended to demonstrate the viability and generality of this novel concept.

Folate-targeted amphiphilic cyclodextrin nanoparticles incorporating a fusogenic peptide deliver therapeutic siRNA and inhibit the invasive capacity of 3D prostate cancer tumours

The main barrier to the development of an effective RNA interference (RNAi) therapy is the lack of a suitable delivery vector. Modified cyclodextrins have emerged in recent years for the delivery of siRNA. In the present study, a folate-targeted amphiphilic cyclodextrin was formulated using DSPE-PEG₅₀₀₀-folate to target prostate cancer cells. The fusogenic peptide GALA was included in the formulation to aid in the endosomal release of siRNA. Targeted nanoparticles were less than 200nm in size with a neutral surface charge. The complexes were able to bind siRNA and protect it from serum nucleases. Incubation with excess free folate resulted in a significant decrease in the uptake of targeted nanoparticles in LNCaP and PC3 cells, both of which have been reported to have differing pathways of folate uptake. There was a significant reduction in the therapeutic targets, ZEB1 and NRP1 at mRNA and protein level following treatment with targeted complexes. In preliminary functional assays using 3D spheroids, treatment of PC3 tumours with targeted complexes with ZEB1 and NRP1 siRNA resulted in more compact colonies relative to the untargeted controls and inhibited infiltration into the Matrigel™ layer.

Mesoporous self-assembled nanoparticles of biotransesterified cyclodextrins and nonlamellar lipids as carriers of water-insoluble substances

Soft mesoporous hierarchically structured particles were created by the self-assembly of an amphiphilic deep cavitand cyclodextrin βCD-nC₁₀ (degree of substitution n = 7.3), with a nanocavity grafted by multiple alkyl (C₁₀) chains on the secondary face of the βCD macrocycle through enzymatic biotransesterification, and the nonlamellar lipid monoolein (MO). The effect of the non-ionic dispersing agent polysorbate 80 (P80) on the liquid crystalline organization of the nanocarriers and their stability was studied in the context of vesicle-to-cubosome transition. The coexistence of small vesicular and nanosponge membrane objects with bigger nanoparticles with inner multicompartment cubic lattice structures was established as a typical feature of the employed dispersion process. The cryogenic transmission electron microscopy (cryo-TEM) images and small-angle X-ray scattering (SAXS) structural analyses revealed the dependence of the internal organization of the self-assembled nanoparticles on the presence of embedded βCD-nC₁₀ deep cavitands in the lipid bilayers. The obtained results indicated that the incorporated amphiphilic βCD-nC₁₀ building blocks stabilize the cubic lattice packing in the lipid membrane particles, which displayed structural features beyond the traditional CD nanosponges. UV-Vis spectroscopy was employed to characterize the nanoencapsulation of a model hydrophobic dimethylphenylazo-naphthol guest compound (Oil red) in the created nanocarriers. In perspective, these dual porosity carriers should be suitable for co-encapsulation and sustained delivery of peptide, protein or siRNA biopharmaceuticals together with small molecular weight drug compounds or imaging agents.

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.

Folate-targeted amphiphilic cyclodextrin.siRNA nanoparticles for prostate cancer therapy exhibit PSMA mediated uptake, therapeutic gene silencing in vitro and prolonged circulation in vivo

In this study, a folate targeted cyclodextrin (CD) nanoparticle was prepared by co-formulating CD.siRNA complexes with DSPE-PEG₅₀₀₀-folate to target the prostate specific membrane antigen (PSMA). Targeted formulations showed increased uptake, relative to untargeted controls, in two prostate cancer cell lines expressing PSMA (VCaP and LNCaP). Competitive uptake studies, using excess folate, significantly reduced uptake of targeted nanoparticles in PSMA positive cell lines (P<0.001). Relative to untreated controls, folate-targeted nanoparticles significantly reduced the levels of RelA mRNA in VCaP and LNCaP cells by 44% and 22% respectively (P<0.001). In contrast there was no significant reduction in RelA mRNA in these cell lines by untargeted complexes. Pharmacokinetic (PK) data indicated that the incorporation of PEG into the formulation increased the circulation time of siRNA 8-fold. This study highlights the ability of incorporating a folate ligand into CD.siRNA nanoparticles to allow for targeted delivery of siRNA to prostate cancer cells via the PSMA.

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.

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.

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.

Nano-Assemblies of Modified Cyclodextrins and Their Complexes with Guest Molecules: Incorporation in Nanostructured Membranes and Amphiphile Nanoarchitectonics Design

A variety of cyclodextrin-based molecular structures, with substitutions of either primary or secondary faces of the natural oligosaccharide macrocycles of α-, β-, or γ-cyclodextrins, have been designed towards innovative applications of self-assembled cyclodextrin nanomaterials. Amphiphilic cyclodextrins have been obtained by chemical or enzymatic modifications of their macrocycles using phospholipidyl, peptidolipidyl, cholesteryl, and oligo(ethylene oxide) anchors as well as variable numbers of grafted hydrophobic hydrocarbon or fluorinated chains. These novel compounds may self-assemble in an aqueous medium into different types of supramolecular nanoassemblies (vesicles, micelles, nanorods, nanospheres, and other kinds of nanoparticles and liquid crystalline structures). This review discusses the supramolecular nanoarchitectures, which can be formed by amphiphilic cyclodextrin derivatives in mixtures with other molecules (phospholipids, surfactants, and olygonucleotides). Biomedical applications are foreseen for nanoencapsulation of drug molecules in the hydrophobic interchain volumes and nanocavities of the amphiphilic cyclodextrins (serving as drug carriers or pharmaceutical excipients), anticancer phototherapy, gene delivery, as well as for protection of instable active ingredients through inclusion complexation in nanostructured media.

Non-viral nanosystems for gene and small interfering RNA delivery to the central nervous system: formulating the solution

The application of gene and RNAi-based therapies to the central nervous system (CNS), for neurological and neurodegenerative disease, offers immense potential. The issue of delivery to the target site remains the single greatest barrier to achieving this. There are challenges to gene and siRNA (small interfering RNA) delivery which are specific to the CNS, including the post-mitotic nature of neurons, their resistance to transfection and the blood-brain barrier. Viral vectors are highly efficient and have been used extensively in pre-clinical studies for CNS diseases. However, non-viral delivery offers an exciting alternative. In this review, we will discuss the extracellular and intracellular barriers to gene and siRNA delivery in the CNS. Our focus will be directed towards various non-viral strategies used to overcome these barriers. In this regard, we describe selected non-viral vectors and categorise them according to the barriers that they overcome by their formulation and targeting strategies. Some of the difficulties associated with non-viral vectors such as toxicity, large-scale manufacture and route of administration are discussed. We provide examples of optimised formulation approaches and discuss regulatory hurdles to clinical validation. Finally, we outline the components of an "ideal" formulation, based on a critical analysis of the approaches highlighted throughout the review.

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

Optimising non-viral vectors for neuronal siRNA delivery presents a significant challenge. Here, we investigate a co-formulation, consisting of two amphiphilic cyclodextrins (CDs), one cationic and the other PEGylated, which were blended together for siRNA delivery to a neuronal cell culture model. Co-formulated CD-siRNA complexes were characterised in terms of size, charge and morphology. Stability in salt and serum was also examined. Uptake was determined by flow cytometry and toxicity was measured by MTT assay. Knockdown of a luciferase reporter gene was used as a measure of gene silencing efficiency. Incorporation of a PEGylated CD in the formulation had significant effects on the physical and biological properties of CD.siRNA complexes. Co-formulated complexes exhibited a lower surface charge and greater stability in a high salt environment. However, the inclusion of the PEGylated CD also dramatically reduced gene silencing efficiency due to its effects on neuronal uptake. The co-formulation strategy for cationic and PEGylated CDs improved the stability of the CD.siRNA delivery systems, although knockdown efficiency was impaired. Future work will focus on the addition of targeting ligands to the co-formulated complexes to restore transfection capabilities.

Gene silencing of TNF-alpha in a murine model of acute colitis using a modified cyclodextrin delivery system

Inflammatory bowel disease (IBD) is a chronic relapsing inflammation of the gastrointestinal tract. The cytokine TNF-alpha (TNF-α) plays a pivotal role in mediating this inflammatory response. RNA interference (RNAi) holds great promise for the specific and selective silencing of aberrantly expressed genes, such as TNF-α in IBD. The aim of this study was to investigate the efficacy of an amphiphilic cationic cyclodextrin (CD) vector for effective TNF-α siRNA delivery to macrophage cells and to mice with induced acute-colitis. The stability of CD.siRNA was examined by gel electrophoresis in biorelevant media reflecting colonic fluids. RAW264.7 cells were transfected with CD.TNF-α siRNA, stimulated with lipopolysaccharide (LPS) and TNF-α and IL-6 responses were measured by PCR and ELISA. Female C57BL/6 mice were exposed to dextran sodium sulphate (DSS) and treated by intrarectal administration with either CD.siRNA TNF-α or a control solution. In vitro, siRNA in CD nanocomplexes remained intact and stable in both fed and fasted simulated colonic fluids. RAW264.7 cells transfected with CD.TNF-α siRNA and stimulated with LPS displayed a significant reduction in both gene and protein levels of TNF-α and IL-6. CD.TNF-α siRNA-treated mice revealed a mild amelioration in clinical signs of colitis, but significant reductions in total colon weight and colonic mRNA expression of TNF-α and IL-6 compared to DSS-control mice were detected. This data indicates the clinical potential of a local CD-based TNF-α siRNA delivery system for the treatment of IBD.