Sustained polymeric delivery of gene silencing antisense ODNs, siRNA, DNAzymes and ribozymes: in vitro and in vivo studies

A Convenient Oligonucleotide Conjugation via Tandem Staudinger Reaction and Amide Bond Formation at the Internucleotidic Phosphate Position

Staudinger reaction on the solid phase between an electronodeficit organic azide, such as sulfonyl azide, and the phosphite triester formed upon phosphoramidite coupling is a convenient method for the chemical modification of oligonucleotides at the internucleotidic phosphate position. In this work, 4-carboxybenzenesulfonyl azide, either with a free carboxy group or in the form of an activated ester such as pentafluorophenyl, 4-nitrophenyl, or pentafluorobenzyl, was used to introduce a carboxylic acid function to the terminal or internal internucleotidic phosphate of an oligonucleotide via the Staudinger reaction. A subsequent treatment with excess primary alkyl amine followed by the usual work-up, after prior activation with a suitable peptide coupling agent such as a uronium salt/1-hydroxybenzotriazole in the case of a free carboxyl, afforded amide-linked oligonucleotide conjugates in good yields including multiple conjugations of up to the exhaustive modification at each phosphate position for a weakly activated pentafluorobenzyl ester, whereas more strongly activated and, thus, more reactive aryl esters provided only single conjugations at the 5'-end. The conjugates synthesized include those with di- and polyamines that introduce a positively charged side chain to potentially assist the intracellular delivery of the oligonucleotide.

A promising nucleic acid therapy drug: DNAzymes and its delivery system

Based on the development of nucleic acid therapeutic drugs, DNAzymes obtained through in vitro selection technology in 1994 are gradually being sought. DNAzymes are single-stranded DNA molecules with catalytic function, which specifically cleave RNA under the action of metal ions. Various in vivo and in vitro models have recently demonstrated that DNAzymes can target related genes in cancer, cardiovascular disease, bacterial and viral infection, and central nervous system disease. Compared with other nucleic acid therapy drugs, DNAzymes have gained more attention due to their excellent cutting efficiency, high stability, and low cost. Here, We first briefly reviewed the development and characteristics of DNAzymes, then discussed disease-targeting inhibition model of DNAzymes, hoping to provide new insights and ways for disease treatment. Finally, DNAzymes were still subject to some restrictions in practical applications, including low cell uptake efficiency, nuclease degradation and interference from other biological matrices. We discussed the latest delivery strategy of DNAzymes, among which lipid nanoparticles have recently received widespread attention due to the successful delivery of the COVID-19 mRNA vaccine, which provides the possibility for the subsequent clinical application of DNAzymes. In addition, the future development of DNAzymes was prospected.

DNAzyme loaded nano-niosomes attenuate myocardial ischemia/reperfusion injury by targeting apoptosis, inflammation in a NF-κB dependent mechanism

Although DNAzymes have been found to reduce injury after myocardial ischemia/reperfusion (MI/R), their efficiency have been limited due to rapid degradation in vivo. Thus, this study was conducted to extend their half-life by encapsulation into nano‑niosomes and examine their cardioprotective effects in a rat model of myocardial infarction (MI). In order to synthesize nano‑niosomes, surface active agent film hydration method was used. Characterization of nano‑niosomes was performed using the atomic force microscopy (AFM). In order to establish MI/R model in rats, left anterior descending coronary artery (LAD) was ligated for 30 min. A single dose (150µL) of drug formulations was injected into the infarcted region. The cardiac function was evaluated using echocardiography. The expression of pro-inflammatory cytokines, apoptotic factors, and nuclear factor-κB (NF-κB) were evaluated using Western blot and immunohistochemistry, respectively. Particle size of only nano-niosomes was in the range of 60-90 nm, while a shift to 70-110 nm was seen after DNAzyme encapsulation. MI rats treated with DNAzyme‑loaded nano‑niosomes could markedly reduce Bax, caspase3, TNF-α, IL-1β, and NF-κB as well as increase Bcl-2 compared to only MI/R group. Collectively, our finding show that nano‑niosomes can be considered excellent drug delivery platforms to extend half-life and stability of DNAzyme, when it is used to reduce myocardial I/R injury.

mRNA-activated DNAzyme nanoprobe for tumor cell precise imaging and gene therapy

A novel Au-nucleic acid nanoprobe, catalyzed by mRNA, has been developed for live cell imaging and precise treatment of tumor cells. This nanoprobe exhibits the remarkable ability to differentiate between tumor cells and normal cells through live cell mRNA imaging, while selectively inducing apoptosis in tumor cells.

Recent advances in therapeutic nucleic acids and their analytical methods

Therapeutic nucleic acids are various chemically modified RNA or DNA with different functions, which mainly play roles at the gene level. Owing to its accurately targeting at pathogenic genes, nucleic acid based therapeutics have a wide range of application prospects. Recently, the improvement on chemical synthesis and delivery materials accelerated the development of therapeutic nucleic acids rapidly. Up to now, 17 nucleic acid based therapeutics approved by Food and Drug Administration (FDA) or European Medicines Agency (EMA). The development of therapeutics raised higher requirements for analytical methods, both in quality control and in clinical research. The first part of this review introduces different classes of therapeutic nucleic acids, including antisense oligonucleotide (ASO), RNA interference (RNAi) therapy, mRNA, aptamer and other classes which are under research. The second part reviews the therapeutic nucleic acids commercialized from 2019 to now. The third part discusses the analytical methods for nucleic acid based therapeutics, including liquid chromatography-based methods, capillary gel electrophoresis (CGE), hybridization enzyme-linked immunosorbent assay (ELISA) and other infrequently used methods. Finally, the advantages and shortcomings of these methods are summarized, and the future development of analysis methods are prospected.

DNAzymes, Novel Therapeutic Agents in Cancer Therapy: A Review of Concepts to Applications

The past few decades have witnessed a rapid evolution in cancer drug research which is aimed at developing active biological interventions to regulate cancer-specific molecular targets. Nucleic acid-based therapeutics, including ribozymes, antisense oligonucleotides, small interference RNA (siRNA), aptamer, and DNAzymes, have emerged as promising candidates regulating cancer-specific genes at either the transcriptional or posttranscriptional level. Gene-specific catalytic DNA molecules, or DNAzymes, have shown promise as a therapeutic intervention against cancer in various in vitro and in vivo models, expediting towards clinical applications. DNAzymes are single-stranded catalytic DNA that has not been observed in nature, and they are synthesized through in vitro selection processes from a large pool of random DNA libraries. The intrinsic properties of DNAzymes like small molecular weight, higher stability, excellent programmability, diversity, and low cost have brought them to the forefront of the nucleic acid-based therapeutic arsenal available for cancers. In recent years, considerable efforts have been undertaken to assess a variety of DNAzymes against different cancers. However, their therapeutic application is constrained by the low delivery efficiency, cellular uptake, and target detection within the tumour microenvironment. Thus, there is a pursuit to identify efficient delivery methods in vivo before the full potential of DNAzymes in cancer therapy is realized. In this light, a review of the recent advances in the use of DNAzymes against cancers in preclinical and clinical settings is valuable to understand its potential as effective cancer therapy. We have thus sought to firstly provide a brief overview of construction and recent improvements in the design of DNAzymes. Secondly, this review stipulates the efficacy, safety, and tolerability of DNAzymes developed against major hallmarks of cancers tested in preclinical and clinical settings. Lastly, the recent advances in DNAzyme delivery systems along with the challenges and prospects for the clinical application of DNAzymes as cancer therapy are also discussed.

Chemistry of Peptide-Oligonucleotide Conjugates: A Review

Peptide-oligonucleotide conjugates (POCs) represent one of the increasingly successful albeit costly approaches to increasing the cellular uptake, tissue delivery, bioavailability, and, thus, overall efficiency of therapeutic nucleic acids, such as, antisense oligonucleotides and small interfering RNAs. This review puts the subject of chemical synthesis of POCs into the wider context of therapeutic oligonucleotides and the problem of nucleic acid drug delivery, cell-penetrating peptide structural types, the mechanisms of their intracellular transport, and the ways of application, which include the formation of non-covalent complexes with oligonucleotides (peptide additives) or covalent conjugation. The main strategies for the synthesis of POCs are viewed in detail, which are conceptually divided into (a) the stepwise solid-phase synthesis approach and (b) post-synthetic conjugation either in solution or on the solid phase, especially by means of various click chemistries. The relative advantages and disadvantages of both strategies are discussed and compared.

PLGA/PCADK composite microspheres containing hyaluronic acid-chitosan siRNA nanoparticles: A rational design for rheumatoid arthritis therapy

Myeloid cell leukemia-1 (Mcl-1), a member of the Bcl-2 anti-apoptotic family, is overexpressed in the synovial macrophages of patients with rheumatoid arthritis (RA). Small interfering RNA (siRNA) Mcl-1 can induce macrophage apoptosis in the joints and is a potential therapeutic target of RA. Nevertheless, the application of siRNA is limited owing to its instability and susceptibility to degradation in vivo. To address these shortcomings, we developed composite microspheres (MPs) loaded with hyaluronic acid (HA)-chitosan (CS) nanoparticles (NPs). First, we synthesized HA-CS/siRNA NPs (HCNPs) using ionotropic gelation process. Then, HCNPs, as an internal aqueous phase, were loaded into poly (D, L-lactide-co-glycolide) (PLGA) and poly (cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK) MPs using the double emulsion method. The NPs-in-MPs (NiMPs) composite system provided sustained release of NPs, protected siRNA against nuclease degradation in the serum, and could readily cross the cellular membrane. In addition, we evaluated the advantages of NiMPs in an adjuvant-induced arthritis rat model. Our experimental results demonstrate that NiMPs have greater pharmacodynamic effects than common MPs. Meanwhile, compared with HCNPs, NiMPs reduced the frequency of drug administration. Therefore, NiMPs are a promising and novel siRNA delivery vehicle for RA therapy.

I-Motif-Based in Situ Bipedal Hybridization Chain Reaction for Specific Activatable Imaging and Enhanced Delivery of Antisense Oligonucleotides

The efficient and precise delivery of antisense oligonucleotides (ASOs) to target cells is of great value in gene silencing. However, the specificity and packaging capacity of delivery system still remains challenging. Here, we designed an i-motif forming-initiated in situ bipedal hybridization chain reaction (pH-Apt-BiHCR) amplification strategy for specific target cells imaging and enhanced gene delivery of ASOs. As a proof of concept, an 8-nt ASO modified with locked nucleic acid (LNA) which is complementary to the seed region of microRNA21 (miR-21) was used for gene silencing studies. Benefiting from the design of hairpin-contained i-motif, the stimuli-responsive assembly of pH-Apt-BiHCR was successfully achieved on MCF-7 cells surface based on the specific recognition of aptamer. Using this strategy, the pH-Apt-BiHCR not only contains repeated fluorescence resonance energy transfer (FRET) units for activatable tumor imaging with high contrast but also arrays with plenty of LNA ASOs as interference molecules for cancer cells inhibition. An in vitro assay showed that this strategy presented an excellent response ability in buffer within a narrow pH range (6.0-7.0) with a transition midpoint (pH^T) of 6.44 ± 0.06. Moreover, live cell studies revealed that it realized a specific activatable imaging of target cells, while the ASOs arrayed pH-Apt-BiHCR exhibited improved internalization via an endocytosis pathway and enhanced gene silencing to MCF-7 cells compared to single ASO alone. We believe that this design will inspire the development of novel probes for early diagnosis and therapy of cancer cells.

Mechanistic profiling of the release kinetics of siRNA from lipidoid-polymer hybrid nanoparticles in vitro and in vivo after pulmonary administration

Understanding the release kinetics of siRNA from nanocarriers, their cellular uptake, their in vivo biodistribution and pharmacokinetics is a fundamental prerequisite for efficient optimisation of the design of nanocarriers for siRNA-based therapeutics. Thus, we investigated the influence of composition on the siRNA release from lipid-polymer hybrid nanoparticles (LPNs) consisting of cationic lipidoid 5 (L₅) and poly(DL-lactic-co-glycolic acid) (PLGA) intended for pulmonary administration. An array of siRNA-loaded LPNs was prepared by systematic variation of: (i) the L₅ content (10-20%, w/w), and (ii) the L₅:siRNA ratio (10,1-30:1, w/w). For comparative purposes, L₅-based lipoplexes, L₅-based stable nucleic acid lipid nanoparticles (SNALPs). and dioleoyltrimethylammoniumpropane (DOTAP)-modified LPNs loaded with siRNA were also prepared. Release studies in buffer and lung surfactant-containing medium showed that siRNA release is dependent on the presence of both surfactant and heparin (a displacing agent) in the release medium, since these interact with the lipid shell structure thereby facilitating decomplexation of L₅ and siRNA, as evident from the retarded siRNA release when the L₅ content and the L₅:siRNA ratio were increased. This confirms the hypothesis that siRNA loaded in LPNs is predominantly present as complexes with the cationic lipid and primarily is located near the particle surface. Cellular uptake and tolerability studies in the human macrophage cell line THP-1 and the type I-like human alveolar epithelial cell line hAELVi, which together represents a monolayer-based barrier model of lung epithelium, indicated that uptake of LPNs was much higher in THP-1 cells in agreement with their primary clearance role. In vivo biodistributions of formulations loaded with Alexa Fluor® 750-labelled siRNA after pulmonary administration in mice were compared by using quantitative fluorescence imaging tomography. The L₅-modified LPNs, SNALPs and DOTAP-modified LPNs displayed significantly increased lung retention of siRNA as compared to L₅-based lipoplexes, which had a biodistribution profile comparable to that of non-loaded siRNA, for which >50% of the siRNA dose permeated the air-blood barrier within 6 h and subsequently was excreted via the kidneys. Hence, the enhanced lung retention upon pulmonary administration of siRNA-loaded LPNs represents a promising characteristic that can be used to control the delivery of the siRNA cargo to lung tissue for local management of disease.

Microparticle Depots for Controlled and Sustained Release of Endosomolytic Nanoparticles

Introduction

Nucleic acids have gained recognition as promising immunomodulatory therapeutics. However, their potential is limited by several drug delivery barriers, and there is a need for technologies that enhance intracellular delivery of nucleic acid drugs. Furthermore, controlled and sustained release is a significant concern, as the kinetics and localization of immunomodulators can influence resultant immune responses. Here, we describe the design and initial evaluation of poly(lactic-co-glycolic) acid (PLGA) microparticle (MP) depots for enhanced retention and sustained release of endosomolytic nanoparticles that enable the cytosolic delivery of nucleic acids.

Methods

Endosomolytic p[DMAEMA]_10kD-bl-[PAA_0.3-co-DMAEMA_0.3-co-BMA_0.4]_25kD diblock copolymers were synthesized by reversible addition-fragmentation chain transfer polymerization. Polymers were electrostatically complexed with nucleic acids and resultant nanoparticles (NPs) were encapsulated in PLGA MPs. To modulate release kinetics, ammonium bicarbonate was added as a porogen. Release profiles were quantified in vitro and in vivo via quantification of fluorescently-labeled nucleic acid. Bioactivity of released NPs was assessed using small interfering RNA (siRNA) targeting luciferase as a representative nucleic acid cargo. MPs were incubated with luciferase-expressing 4T1 (4T1-LUC) breast cancer cells in vitro or administered intratumorally to 4T1-LUC breast tumors, and silencing via RNA interference was quantified via longitudinal luminescence imaging.

Results

Endosomolytic NPs complexed to siRNA were effectively loaded into PLGA MPs and release kinetics could be modulated in vitro and in vivo via control of MP porosity, with porous MPs exhibiting faster cargo release. In vitro, release of NPs from porous MP depots enabled sustained luciferase knockdown in 4T1 breast cancer cells over a five-day treatment period. Administered intratumorally, MPs prolonged the retention of nucleic acid within the injected tumor, resulting in enhanced and sustained silencing of luciferase relative to a single bolus administration of NPs at an equivalent dose.

Conclusion

This work highlights the potential of PLGA MP depots as a platform for local release of endosomolytic polymer NPs that enhance the cytosolic delivery of nucleic acid therapeutics.

Small interfering RNAs (siRNAs) in cancer therapy: a nano-based approach

Cancer is one of the most complex diseases that has resulted in multiple genetic disorders and cellular abnormalities. Globally, cancer is the most common health concern disease that is affecting human beings. Great efforts have been made over the past decades in biology with the aim of searching novel and more efficient tools in therapy. Thus, small interfering RNAs (siRNAs) have been considered one of the most noteworthy developments which are able to regulate gene expression following a process known as RNA interference (RNAi). RNAi is a post-transcriptional mechanism that involves the inhibition of gene expression through promoting cleavage on a specific area of a target messenger RNA (mRNA). This technology has shown promising therapeutic results for a good number of diseases, especially in cancer. However, siRNA therapeutics have to face important drawbacks in therapy including stability and successful siRNA delivery in vivo. In this regard, the development of effective siRNA delivery systems has helped addressing these issues by opening novel therapeutic windows which have allowed to build up important advances in Nanomedicine. In this review, we discuss the progress of siRNA therapy as well as its medical application via nanoparticle-mediated delivery for cancer treatment.

Injectable Biodegradable Chitosan-Alginate 3D Porous Gel Scaffold for mRNA Vaccine Delivery

mRNA vaccines have proven to be more stable, effective, and specific than protein/peptide-based vaccines in stimulating both humoral and cellular immune response. However, mRNA's fast degradation rate and low-transfection efficiency in vivo impede its potential in vaccination. Recent research in gene delivery has focused on nonviral vaccine carriers and either implantable or injectable delivery systems to improve transgene expression in vivo. Here, an injectable chitosan-alginate gel scaffold for the local delivery of mRNA vaccines is reported. Gel scaffold biodegradation rates and biocompatibility are quantified. Scaffold-mediated mRNA in vivo transgene expression as well as ovalbumin antigen specific cellular and humoral immune responses are evaluated in vivo. Luciferase reporter protein expression resulting from mRNA lipoplex-loaded gel scaffolds is five times higher than systemic injection. Compared to systemic injections of naked mRNA or mRNA:lipoplexes, elevated levels of T cell proliferation and IFN-γ secretion are seen with in vivo scaffold-mediated mRNA lipoplex delivery. Furthermore, a humoral response (ovalbumin antigen specific IgG levels) is observed as early as week 1 for scaffold-mediated mRNA lipoplex delivery, while protein-based immunization did not elicit IgG production until 2 weeks post-injection. Results suggest that injectable scaffold mRNA vaccine delivery maybe a viable alternative to traditional nucleic acid immunization methods.

Therapeutic Potential of DNAzyme Loaded on Chitosan/Cyclodextrin Nanoparticle to Recovery of Chemosensitivity in the MCF-7 Cell Line

Commonly, acquired resistances to anticancer drug are mediated by overexpression of a membrane-associated protein that encode via multi-drug resistance gene-1 (MDR1). Herein, the mRNA-cleaving DNAzyme that targets the mRNA of MDR1 gene in doxorubicin-resistant breast cancer cell line (MCF-7/DR) loaded on the chitosan β-cyclodextrin complexes was used as a tropical agent. Chitosan/β-cyclodextrin complexes were used to deliver DNAzymes into cancer cells. Determination of the physicochemical characteristics of the particles was done by photon correlation spectroscopy and scanning electron microscopy. The encapsulation efficiency of the complexes was tested by using gel retardation assay. Positively charged nanoparticles interacted with DNAzyme that could perform as an efficient DNAzyme transfection system. The rationale usage of this platform is to sensitize MCF-7/DR to doxorubicin by downregulating the drug-resistance gene MDR1. Results demonstrated a downregulation of MDR1 mRNAs in MCF-7/DR/DNZ by real-time PCR, compared to the MCF-7/DR as control. WST1 assay showed the 22-fold decrease in drug resistance on treated cells 24 h after transfection. Results showed the intracellular accumulation of Rh123 increased in the treated cells with DNAzyme. Results suggested a potential platform in association with chemotherapy drug for cancer therapy and indicated extremely efficient at delivery of DNAzyme in restoring chemosensitivity.

Strategies for improving the specificity of siRNAs for enhanced therapeutic potential

INTRODUCTION

RNA interference has become a tool of choice in the development of drugs in various therapeutic areas of Post Transcriptional Gene Silencing (PTGS). The critical element in developing successful RNAi therapeutics lies in designing small interfering RNA (siRNA) using an efficient algorithm satisfying the designing criteria. Further, translation of siRNA from bench-side to bedside needs an efficient delivery system and/or chemical modification. Areas covered: This review emphasizes the importance of dicer, the criteria for efficient siRNA design, the currently available algorithms and strategies to overcome off-target effects, immune stimulatory effects and endosomal trap. Expert opinion: Specificity and stability are the primary concerns for siRNA therapeutics. The design criteria and algorithms should be chosen rationally to have a siRNA sequence that binds to the corresponding mRNA as it happens in the Watson and Crick base pairing. However, it must evade a few more hurdles (Endocytosis, Serum stability etc.) to be functional in the cytosol.

Cross-Platform Cancer Cell Identification Using Telomerase-Specific Spherical Nucleic Acids

Distinguishing tumor cells from normal cells holds the key to precision diagnosis and effective intervention of cancers. The fundamental difficulties, however, are the heterogeneity of tumor cells and the lack of truly specific and ideally universal cancer biomarkers. Here, we report a concept of tumor cell detection, bypassing the specific genotypic and phenotypic features of different tumor cell types and directly going toward the hallmark of cancer, uncontrollable growth. Combining spherical nucleic acids (SNAs) with exquisitely engineered molecular beacons (SNA beacons, dubbed SNAB technology) is capable of identifying tumor cells from normal cells based on the molecular phenotype of telomerase activity, largely bypassing the heterogeneity problem of cancers. Owing to the cell-entry capability of SNAs, the SNAB probe readily achieves tumor cell detection across multiple platforms, ranging from solution-based assay, to single cell imaging and in vivo solid tumor imaging (unlike PCR that is restricted to cell lysates). We envision the SNAB technology will impact cancer diagnosis, therapeutic response assessment, and image-guided surgery.

Engineering of small interfering RNA-loaded lipidoid-poly(DL-lactic-co-glycolic acid) hybrid nanoparticles for highly efficient and safe gene silencing: A quality by design-based approach

Safety and efficacy of therapeutics based on RNA interference, e.g., small interfering RNA (siRNA), are dependent on the optimal engineering of the delivery technology, which is used for intracellular delivery of siRNA to the cytosol of target cells. We investigated the hypothesis that commonly used and poorly tolerated cationic lipids might be replaced with more efficacious and safe lipidoids as the lipid component of siRNA-loaded lipid-polymer hybrid nanoparticles (LPNs) for achieving more efficient gene silencing at lower and safer doses. However, formulation design of such a complex formulation is highly challenging due to a strong interplay between several contributing factors. Hence, critical formulation variables, i.e. the lipidoid content and siRNA:lipidoid ratio, were initially identified, followed by a systematic quality-by-design approach to define the optimal operating space (OOS), eventually resulting in the identification of a robust, highly efficacious and safe formulation. A 17-run design of experiment with an I-optimal approach was performed to systematically assess the effect of selected variables on critical quality attributes (CQAs), i.e. physicochemical properties (hydrodynamic size, zeta potential, siRNA encapsulation/loading) and the biological performance (in vitro gene silencing and cell viability). Model fitting of the obtained data to construct predictive models revealed non-linear relationships for all CQAs, which can be readily overlooked in one-factor-at-a-time optimization approaches. The response surface methodology further enabled the identification of an OOS that met the desired quality target product profile. The optimized lipidoid-modified LPNs revealed more than 50-fold higher in vitro gene silencing at well-tolerated doses and approx. a twofold increase in siRNA loading as compared to reference LPNs modified with the commonly used cationic lipid dioleyltrimethylammonium propane (DOTAP). Thus, lipidoid-modified LPNs show highly promising prospects for efficient and safe intracellular delivery of siRNA.

Novel siRNA formulation to effectively knockdown mutant p53 in osteosarcoma

Objectives

The tumor suppressor p53 plays a crucial role in the development of osteosarcoma. The primary objective of this study is to develop and optimize lipid based nanoparticle formulations that can carry siRNA and effectively silence mutant p53 in 318–1, a murine osteosarcoma cell line.

Methods

The nanoparticles were composed of a mixture of two lipids (cholesterol and DOTAP) and either PLGA or PLGA-PEG and prepared by using an EmulsiFlex-B3 high pressure homogenizer. A series of studies that include using different nanoparticles, different amount of siRNAs, cell numbers, incubation time, transfection media volume, and storage temperature was performed to optimize the gene silencing efficiency.

Key findings

Replacement of lipids by PLGA or PLGA-PEG decreased the particle size and overall cytotoxicity. Among all lipid-polymer nanoformulations, nanoparticles with 10% PLGA showed highest mutant p53 knockdown efficiency while maintaining higher cell viability when a nanoparticle to siRNA ratio equal to 6.8:0.66 and 75 nM siRNA was used. With long term storage the mutant p53 knockdown efficiency decreased to a greater extent.

Conclusions

This study warrants a future evaluation of this formulation for gene silencing efficiency of mutant p53 in tissue culture and animal models for the treatment of osteosarcoma.

Recent development of synthetic nonviral systems for sustained gene delivery

Sustained gene delivery is of particular importance today because it circumvents the need for repeated therapeutic administration and provides spatial and temporal control of the release profile. Better understanding of the genetic basis of diseases and advances in gene therapy have propelled significant research on biocompatible gene carriers for therapeutic purposes. Varied biodegradable polymer-based architectures have been used to create new compositions with unique properties suitable for sustained gene delivery. This review presents the most recent advances in various polymeric systems: hydrogels, microspheres, nanospheres and scaffolds, having complex architectures to encapsulate and deliver functional genes. Through the recombination of different existing polymer systems, the multicomplex systems can be further endowed with new properties for better-targeted biomedical applications.

Synthetic nanocarriers for the delivery of polynucleotides to the eye

This review is a comprehensive analysis of the progress made so far on the delivery of polynucleotide-based therapeutics to the eye, using synthetic nanocarriers. Attention has been addressed to the capacity of different nanocarriers for the specific delivery of polynucleotides to both, the anterior and posterior segments of the eye, with emphasis on their ability to (i) improve the transport of polynucleotides across the different eye barriers; (ii) promote their intracellular penetration into the target cells; (iii) protect them against degradation and, (iv) deliver them in a long-term fashion way. Overall, the conclusion is that despite the advantages that nanotechnology may offer to the area of ocular polynucleotide-based therapies (especially AS-ODN and siRNA delivery), the knowledge disclosed so far is still limited. This fact underlines the necessity of more fundamental and product-oriented research for making the way of the said nanotherapies towards clinical translation.

Delivery of therapeutic RNA-cleaving oligodeoxyribonucleotides (deoxyribozymes): from cell culture studies to clinical trials

INTRODUCTION

Development of efficient in vivo delivery systems remains a major challenge en route to clinical application of antisense technology, including RNA-cleaving molecules such as deoxyribozymes (DNAzymes). The mechanisms of oligonucleotide uptake and trafficking are clearly dependent on cell type and the type of oligonucleotide analogue. It appears likely that each particular disease target would pose its own specific requirements for a delivery method. Areas covered. In this review we will discuss the available options for DNAzyme delivery in vitro and in vivo, outline various exogenous and endogenous strategies that have been, or are still being, developed and ascertain their applicability with emphasis on those methods that are currently being used in clinical trials. Expert opinion. The available information suggests that a practical system for in vivo delivery has to be biodegradable, as to minimize concerns over long-term toxicity, it should not accumulate in the organism. Extracellular vesicles may offer the most organic way for drug delivery especially as they can be fused with artificial liposomes to produce hybrid nanoparticles. Chemical modification of DNAzymes holds great potential to apply oligonucleotide analogs that would not only be resistant to nuclease digestion, but also able to penetrate cells without external delivery agents.

Screening Immunomodulators To Skew the Antigen-Specific Autoimmune Response

Current therapies to treat autoimmune diseases often result in side effects such as nonspecific immunosuppression. Therapies that can induce antigen-specific immune tolerance provide an opportunity to reverse autoimmunity and mitigate the risks associated with global immunosuppression. In an effort to induce antigen-specific immune tolerance, co-administration of immunomodulators with autoantigens has been investigated in an effort to reprogram autoimmunity. To date, identifying immunomodulators that may skew the antigen-specific immune response has been ad hoc at best. To address this need, we utilized splenocytes obtained from mice with experimental autoimmune encephalomyelitis (EAE) in order to determine if certain immunomodulators may induce markers of immune tolerance following antigen rechallenge. Of the immunomodulatory compounds investigated, only dexamethasone modified the antigen-specific immune response by skewing the cytokine response and decreasing T-cell populations at a concentration corresponding to a relevant in vivo dose. Thus, antigen-educated EAE splenocytes provide an ex vivo screen for investigating compounds capable of skewing the antigen-specific immune response, and this approach could be extrapolated to antigen-educated cells from other diseases or human tissues.

Sustained Release of Cx43 Antisense Oligodeoxynucleotides from Coated Collagen Scaffolds Promotes Wound Healing

Antisense oligodeoxynucleotides targeting the mRNA of the gap junction protein Cx43 promote tissue repair in a variety of different wounds. Delivery of the antisense drug has most often been achieved by a thermoreversible hydrogel, Pluronic F-127, which is very effective in the short term but does not allow for sustained delivery over several days. For chronic wounds that take a long time to heal, repeated dosing with the drug may be desirable but is not always compatible with conventional treatments such as the weekly changing of compression bandages on venous leg ulcers. Here the coating of collagen scaffolds with antisense oligonucleotides is investigated and a way to provide protection of the oligodeoxynucleotide drug is found in conjunction with sustained release over a 7 d period. This approach significantly reduces the normal foreign body reaction to the scaffold, which induces an increase of Cx43 protein and an inhibition of healing. As a result of the antisense integration into the scaffold, inflammation is reduced with the rate of wound healing and contracture is significantly improved. This coated scaffold approach may be very useful for treating venous leg ulcers and also for providing a sustained release of any other types of oligonucleotide drugs that are being developed.

Nanoparticle delivery systems for siRNA-based therapeutics

RNA interference (RNAi) is a naturally occurring endogenous regulatory process in which the short double-stranded RNA causes sequence-specific post-transcriptional gene silencing.

PLGA microspheres encapsulating siRNA

The therapeutic use of small interfering RNA (siRNA) represents a new and powerful approach to suppress the expression of pathologically genes. However, biopharmaceutical drawbacks, such as short half-life, poor cellular uptake, and unspecific distribution into the body, hamper the development of siRNA-based therapeutics. Poly(lactide-co-glycolide), (PLGA) microspheres can be a useful tool to overcome these issues. siRNA can be encapsulated into the PLGA microspheres, which protects the loaded nucleic acid against the enzymatic degradation. Moreover, PLGA microspheres can be injected directly into the action site, where the siRNA can be released in controlled manner, thus avoiding the need of frequent invasive administrations. The complete biodegradability of PLGA to monomers easily metabolized by the body, and its approval by FDA and EMA for parenteral administration, assure the safety of this copolymer and do not require the removal of the device after the complete drug release. In chapter, a basic protocol for the preparation of PLGA microspheres encapsulating siRNA is described. This protocol is based on a double emulsion/solvent evaporation technique, a well known and easy to reproduce method. This specific protocol has been developed to encapsulate a siRNA anti-TNFα in PLGA microspheres, and it has been designed and optimized to achieve high siRNA encapsulation efficiency and slow siRNA release in vitro. However, it can be extended also to other siRNA as well as other RNA or DNA-based oligonucleotides (miRNA, antisense, decoy, etc.). Depending on the applications, chemical modifications of the backbone and site-specific modification within the siRNA sequences could be required.

Megalin-mediated specific uptake of chitosan/siRNA nanoparticles in mouse kidney proximal tubule epithelial cells enables AQP1 gene silencing

RNAi-based strategies provide a great therapeutic potential for treatment of various human diseases including kidney disorders, but face the challenge of in vivo delivery and specific targeting. The chitosan delivery system has previously been shown to target siRNA specifically to the kidneys in mice when administered intravenously. Here we confirm by 2D and 3D bioimaging that chitosan formulated siRNA is retained in the kidney for more than 48 hours where it accumulates in proximal tubule epithelial cells (PTECs), a process that was strongly dependent on the molecular weight of chitosan. Chitosan/siRNA nanoparticles, administered to chimeric mice with conditional knockout of the megalin gene, distributed almost exclusively in cells that expressed megalin, implying that the chitosan/siRNA particle uptake was mediated by a megalin-dependent endocytotic pathway. Knockdown of the water channel aquaporin 1 (AQP1) by up to 50% in PTECs was achieved utilizing the systemic i.v. delivery of chitosan/AQP1 siRNA in mice. In conclusion, specific targeting PTECs with the chitosan nanoparticle system may prove to be a useful strategy for knockdown of specific genes in PTECs, and provides a potential therapeutic strategy for treating various kidney diseases.

Synthesis, characterization, and evaluation of poly (D,L-lactide-co-glycolide)-based nanoformulation of miRNA-150: potential implications for pancreatic cancer therapy

MicroRNAs are small (18–22 nucleotide long) noncoding RNAs that play important roles in biological processes through posttranscriptional regulation of gene expression. Their aberrant expression and functional significance are reported in several human malignancies, including pancreatic cancer. Recently, we identified miR-150 as a novel tumor suppressor microRNA in pancreatic cancer. Furthermore, expression of miR-150 was downregulated in the majority of tumor cases, suggesting that its restoration could serve as an effective approach for pancreatic cancer therapy. In the present study, we developed a nanoparticle-based miR-150 delivery system and tested its therapeutic efficacy in vitro. Using double emulsion solvent evaporation method, we developed a poly (D,L-lactide-co-glycolide) (PLGA)-based nanoformulation of miR-150 (miR-150-NF). Polyethyleneimine (a cationic polymer) was incorporated in PLGA matrix to increase the encapsulation of miR-150. Physical characterization of miR-150-NF demonstrated that these nanoparticles had high encapsulation efficiency (~78%) and exhibited sustained release profile. Treatment of pancreatic cancer cells with miR-150-NF led to efficient intracellular delivery of miR-150 mimics and caused significant downregulation of its target gene (MUC4) expression. Inhibition of MUC4 correlated with a concomitant decrease in the expression of its interacting partner, HER2, and repression of its downstream signaling. Furthermore, treatment of pancreatic cancer cells with miR-150-NF suppressed their growth, clonogenicity, motility, and invasion. Together, these findings suggest that PLGA-based nanoformulation could potentially serve as a safe and effective nanovector platform for miR-150 delivery to pancreatic tumor cells.

The effect of antisense to NF-κB in an albumin microsphere formulation on the progression of left-ventricular remodeling associated with chronic volume overload in rats

BACKGROUND

Increased NF-κB levels play a crucial role in the pathophysiology of heart failure and are known to cause ventricular remodeling. Antisense therapy can be used for blocking the expression of NF-κB and subsequently avoiding heart failure. However, as with most biotechnology products, molecular instability and overall cost are often the major issues and concerns limiting the advancement of most antisense drugs to the market. Therefore, a cost-efficient biodegradable sustained release particle drug delivery system to transport and target NF-kB antisense to its intended site of action would be ideal.

PURPOSE

To evaluate the in vivo performance of a sustained release spray-dried albumin microsphere formulation for effective delivery and treatment of left ventricular remodeling with antisense to NF-κB.

METHODS

Albumin-based microspheres encapsulating antisense to NF-kB were prepared by spray drying and studied in a rat model to treat congestive heart failure.

RESULTS

The NF-κB activation and TNF-α release seen in treated animals were significantly lower than control animals. Ventricular remodeling was controlled in animals with antisense-treated AV fistulas as ΔV0-25 and ΔV0 were significantly lower compared to animals with untreated AV fistulas.

CONCLUSION

This treatment was successful in curbing ventricular remodeling by suppressing NF-κB activation.

Preclinical development of siRNA therapeutics: towards the match between fundamental science and engineered systems

The evolution of synthetic RNAi faces the paradox of interfering with the human biological environment. Due to the fact that all cell physiological processes can be target candidates, silencing a precise biological pathway could be challenging if target selectivity is not properly addressed. Molecular biology has provided scientific tools to suppress some of the most critical issues in gene therapy, while setting the standards for siRNA clinical application. However, the protein down-regulation through the mRNA silencing is intimately related to the sequence-specific siRNA ability to interact accurately with the potential target. Moreover, its in vivo biological fate is highly dependent on the successful design of a vehicle able to overcome both extracellular and intracellular barriers. Anticipating a great deal of innovation, crucial to meet the challenges involved in the RNAi therapeutics, the present review intends to build up a synopsis on the delivery strategies currently developed.

FROM THE CLINICAL EDITOR

This review discusses recent progress and pertinent limiting factors related to the use of siRNA-s as efficient protein-specific "silencing" agents, focusing on targeted delivery not only to cells of interest, but to the proper intracellular destination.

Surface-modified nanoparticles enhance transurothelial penetration and delivery of survivin siRNA in treating bladder cancer

Penetration of the bladder permeability barrier (BPB) is a major challenge when treating bladder diseases via intravesical delivery. To increase transurothelial migration and tissue and tumor cell uptake, poly(lactic-co-glycolic acid; PLGA) nanoparticles (NP) were modified by addition of a low molecular weight (2.5 or 20 kDa) positively charged mucoadhesive polysaccharide, chitosan, to the NP surface. In designing these NPs, we balanced the adhesive properties of chitosan with the release and bioactivity of the siRNA. Chitosan-functionalized NPs demonstrated increased binding to and uptake in intravesically instilled mouse bladders and human ureter at 10 times the level of unmodified NPs. Furthermore, we extended the bioactivity of survivin siRNA in vitro for up to 9 days and demonstrated a decrease in proliferation when using chitosan-modified NPs relative to unmodified NPs. In addition, treatment of xenograft tumors with chitosan-modified NPs that encapsulate survivin siRNA (NP-siSUR-CH2.5) resulted in a 65% reduction in tumor volume and a 75% decrease in survivin expression relative to tumors treated with blank chitosan NPs (NP-Bk-CH2.5). Our low molecular weight chitosan delivery system has the capacity to transport large amounts of siRNA across the urothelium and/or to the tumor site, thus increasing therapeutic response.

Multicompartment micelle-structured peptide nanoparticles: a new biocompatible gene- and drug-delivery tool

Self-assembled, biodegradable materials that embed fragile, soluble, or insoluble compounds of therapeutic interest have potential use as drug delivery systems. The bead-forming peptide Ac-X3-gT can embed hydrophobic and hydrophilic payloads. Loaded peptide beads were internalized by human acute monocytic leukemia cell line (THP-1) macrophages, THP-1 monocytes, and hepatocellular carcinoma cells (Huh7). Furthermore, paclitaxel and doxorubicin coencapsulated in the peptide beads were delivered to THP-1 monocytes, causing a decrease in cell viability due to the activity of the anticancer drugs. In addition to the bead-forming peptide Ac-X3-gT, the use of a positively charged peptide analogue increased the RNA/DNA embedding efficiency to 99% by charge compensation and micellar complexation. Internalization of the resulting gene delivery systems by Huh7 cells led to specific gene silencing either by embedded small interfering RNA or by plasmid-encoding small hairpin RNA delivered in cells. The new class of purely peptidic material caused no measurable toxicity during in vitro experiments, thereby indicating potential use as a drug delivery system for multidrug delivery and gene therapy.

Nanoparticles for urothelium penetration and delivery of the histone deacetylase inhibitor belinostat for treatment of bladder cancer

Nearly 40% of patients with non-invasive bladder cancer will progress to invasive disease despite locally-directed therapy. Overcoming the bladder permeability barrier (BPB) is a challenge for intravesical drug delivery. Using the fluorophore coumarin (C6), we synthesized C6-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs), which were surface modified with a novel cell penetrating polymer, poly(guanidinium oxanorbornene) (PGON). Addition of PGON to the NP surface improved tissue penetration by 10-fold in intravesically-treated mouse bladder and ex vivo human ureter. In addition, NP-C6-PGON significantly enhanced intracellular uptake of NPs compared to NPs without PGON. To examine biological activity, we synthesized NPs that were loaded with the histone deacetylase (HDAC) inhibitor belinostat (NP-Bel-PGON). NP-Bel-PGON exhibited a significantly lower IC50 in cultured bladder cancer cells, and sustained hyperacetylation, when compared to unencapsulated belinostat. Xenograft tumors treated with NP-Bel-PGON showed a 70% reduction in volume, and a 2.5-fold higher intratumoral acetyl-H4, when compared to tumors treated with unloaded NP-PGON.

FROM THE CLINICAL EDITOR

These authors demonstrate that PLGA nanoparticles with PGON surface functionalization result in greatly enhanced cell penetrating capabilities, and present convincing data from a mouse model of bladder cancer for increased chemotherapy efficacy.

Metabolism studies of unformulated internally [3H]-labeled short interfering RNAs in mice

Absorption, distribution, metabolism, and excretion properties of two unformulated model short interfering RNA (siRNAs) were determined using a single internal [(3)H]-radiolabeling procedure, in which the full-length oligonucleotides were radiolabeled by Br/(3)H -exchange. Tissue distribution, excretion, and mass balance of radioactivity were investigated in male CD-1 mice after a single intravenous administration of the [(3)H]siRNAs, at a target dose level of 5 mg/kg. Quantitative whole-body autoradiography and liquid scintillation counting techniques were used to determine tissue distribution. Radiochromatogram profiles were determined in plasma, tissue extracts, and urine. Metabolites were separated by liquid chromatography and identified by radiodetection and high-resolution accurate mass spectrometry. In general, there was little difference in the distribution of total radiolabeled components after administration of the two unformulated [(3)H]siRNAs. The radioactivity was rapidly and widely distributed throughout the body and remained detectable in all tissues investigated at later time points (24 and 48 hours for [(3)H]MRP4 (multidrug resistance protein isoform 4) and [(3)H]SSB (Sjögren Syndrome antigen B) siRNA, respectively). After an initial rapid decrease, concentrations of total radiolabeled components in dried blood decreased at a much slower rate. A nearly complete mass balance was obtained for the [(3)H]SSB siRNA, and renal excretion was the main route of elimination (38%). The metabolism of the two model siRNAs was rapid and extensive. Five minutes after administration, no parent compound could be detected in plasma. Instead, radiolabeled nucleosides resulting from nuclease hydrolysis were observed. In the metabolism profiles obtained from various tissues, only radiolabeled nucleosides were found, suggesting that siRNAs are rapidly metabolized and that the distribution pattern of total radiolabeled components can be ascribed to small molecular weight metabolites.

Neutral polymeric micelles for RNA delivery

RNA interference (RNAi) drugs have significant therapeutic potential, but delivery systems with appropriate efficacy and toxicity profiles are still needed. Here, we describe a neutral, ampholytic polymeric delivery system based on conjugatable diblock polymer micelles. The diblock copolymer contains a hydrophilic poly[N-(2-hydroxypropyl)methacrylamide-co-N-(2-(pyridin-2-yldisulfanyl)ethyl)methacrylamide) (poly[HPMA-co-PDSMA]) segment to promote aqueous stability and facilitate thiol-disulfide exchange reactions and a second ampholytic block composed of propylacrylic acid (PAA), dimethylaminoethyl methacrylate (DMAEMA), and butyl methacrylate (BMA). The poly[(HPMA-co-PDSMA)-b-(PAA-co-DMAEMA-co-BMA)] was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization with an overall molecular weight of 22 000 g/mol and a PDI of 1.88. Dynamic light scattering and fluorescence measurements indicated that the diblock copolymers self-assemble under aqueous conditions to form polymeric micelles with a hydrodynamic radius and critical micelle concentration of 25 nm and 25 μg/mL, respectively. Red blood cell hemolysis experiments show that the neutral hydrophilic micelles have potent membrane destabilizing activity at endosomal pH values. Thiolated siRNA targeting glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was directly conjugated to the polymeric micelles via thiol exchange reactions with the pyridal disulfide groups present in the micelle corona. Maximum silencing activity in HeLa cells was observed at a 1:10 molar ratio of siRNA to polymer following a 48 h incubation period. Under these conditions 90% mRNA knockdown and 65% protein knockdown at 48 h was achieved with negligible toxicity. In contrast the polymeric micelles lacking a pH-responsive endosomalytic segment demonstrated negligible mRNA and protein knockdown under these conditions. The potent mRNA knockdown and excellent biocompatibility of the neutral siRNA conjugates demonstrate the potential utility of this carrier design for delivering therapeutic siRNA drugs.

Mesoporous silica-supported lipid bilayers (protocells) for DNA cargo delivery to the spinal cord

Amorphous mesoporous silica nanoparticles ('protocells') that support surface lipid bilayers recently characterized in vitro as carrier constructs for small drug and DNA delivery are reported here as highly biocompatible both in vitro and in vivo, involving the brain and spinal cord following spinal delivery into the lumbosacral subarachnoid space (intrathecal; i.t.). Specifically, positively charged, 1, 2-Dioleoyl-3-Trimethylammonium-Propane (DOTAP)-cholesterol (DOTAP:Chol) liposome-formulated protocells revealed stable in vitro cargo release kinetics and cellular interleukin-10 (IL-10) transgene transfection. Recent approaches using synthetic non-viral vector platforms to deliver the pain-suppressive therapeutic transgene, IL-10, to the spinal subarachnoid space have yielded promising results in animal models of peripheral neuropathy, a condition involving aberrant neuronal communication within sensory pathways in the nervous system. Non-viral drug and gene delivery protocell platforms offer potential flexibility because cargo release-rates can be pH-dependent. We report here that i.t. delivery of protocells, with modified chemistry supporting a surface coating of DOTAP:Chol liposomes and containing the IL-10 transgene, results in functional suppression of pain-related behavior in rats for extended periods. This study is the first demonstration that protocell vectors offer amenable and enduring in vivo biological characteristics that can be applied to spinal gene delivery.

T-cell activation is enhanced by targeting IL-10 cytokine production in toll-like receptor-stimulated macrophages

Toll-like receptor (TLR) agonists represent potentially useful cancer vaccine adjuvants in their ability to stimulate antigen-presenting cells (APCs) and subsequently amplify the cytotoxic T-cell response. The purpose of this study was to characterize APC responses to TLR activation and to determine the subsequent effect on lymphocyte activation. We exposed murine primary bone marrow-derived macrophages to increasing concentrations of agonists to TLRs 2, 3, 4, and 9. This resulted in a dose-dependent increase in production of not only tumor necrosis factor–alpha (TNF-α), a surrogate marker of the proinflammatory response, but also interleukin 10 (IL-10), a well-described inhibitory cytokine. Importantly, IL-10 secretion was not induced by low concentrations of TLR agonists that readily produced TNF-α. We subsequently stimulated lymphocytes with anti-CD3 antibody in the presence of media from macrophages activated with higher doses of TLR agonists and observed suppression of interferon gamma release. Use of both IL-10 knockout macrophages and IL-10 small-interfering RNA (siRNA) ablated this suppressive effect. Finally, IL-10 siRNA was successfully used to suppress CpG-induced IL-10 production in vivo. We conclude that TLR-mediated APC stimulation can induce a paradoxical inhibitory effect on T-cell activation mediated by IL-10.

Intra-articular controlled release of anti-inflammatory siRNA with biodegradable polymer microparticles ameliorates temporomandibular joint inflammation

We investigated the in vivo therapeutic efficacy of an intra-articular controlled release system consisting of biodegradable poly(dl-lactic-co-glycolic acid) (PLGA) microparticles (MPs) encapsulating anti-inflammatory small interfering RNA (siRNA), together with branched poly(ethylenimine) (PEI) as a transfecting agent, in a rat model of painful temporomandibular joint (TMJ) inflammation. The in vivo effects of PLGA MP dose and siRNA-PEI polyplex delivery were examined via non-invasive meal pattern analysis and by quantifying the protein level of the siRNA target as well as of several downstream inflammatory cytokines. Controlled release of siRNA-PEI from PLGA MPs significantly reduced inflammation-induced changes in meal patterns compared to untreated rats with inflamed TMJs. These changes correlated to decreases in tissue-level protein expression of the siRNA target to 20-50% of the amount present in the corresponding control groups. Similar reductions were also observed in the expression of downstream inflammatory cytokines, e.g. interleukin-6, whose tissue levels in the siRNA-PEI PLGA MP groups were 50% of the values for the corresponding controls. This intra-articular sustained release system has significant implications for the treatment of severe TMJ pain, and also has the potential to be readily adapted and applied to mitigate painful, chronic inflammation in a variety of conditions.

Lipid-based vectors for siRNA delivery

siRNA therapeutics has developed rapidly and already there are clinical trials ongoing or planned; however, the delivery of siRNA into cells, tissues or organs remains to be a major obstacle. Lipid-based vectors hold the most promising position among non-viral vectors, as they have a similar structure to cell or organelle membranes. But when used in the form of liposomes, these vectors have shown some problems. Therefore, either the nature of lipids themselves or forms used should be improved. As a novel class of lipid like materials, lipidoids have the advantages of easy synthesis and the ability for delivering siRNA to obtain excellent silencing activity. However, the toxicities of lipidoids have not been thoroughly studied. pH responsive lipids have also gained great attention recently, though some of the amine-based lipids are not novel in terms of chemical structures. More complex self-assembly structures, such as LPD (LPH) and LCP, may provide a good solution to siRNA delivery. They have demonstrated controlled particle morphology and size and siRNA delivery activity for both in vitro and in vivo.

An inhalable β₂-adrenoceptor ligand-directed guanidinylated chitosan carrier for targeted delivery of siRNA to lung

SiRNA-based strategies appear to be an exciting new approach for the treatment of respiratory diseases. To extrapolate siRNA-mediated interventions from bench to bedside in this area, several aspects have to be jointly considered, including a safe and efficient gene carrier with pulmonary deposition efficiency, as well as in vivo method for siRNA/nanoparticles delivery. Accordingly, in this work, (i) a non-viral DNA vector, guanidinylated chitosan (GCS) that has been developed in our previous study [X.Y. Zhai, P. Sun, Y.F. Luo, C.N. Ma, J. Xu, W.G. Liu, 2011], was tested for siRNA delivery. We demonstrated that GCS was able to completely condense siRNA at weight ratio 40:1, forming nanosize particles of diameter ~100 nm, 15 mV in surface potential. Guanidinylation of chitosan not only decreased the cytotoxicity but also facilitated cellular internalization of siRNA nanoparticles, leading to an enhanced gene-silencing efficiency compared to the pristine chitosan (CS). (ii) We chemically coupled salbutamol, a β(2)-adrenoceptor agonist, to GCS (SGCS), which successfully improved targeting specificity of the green fluorescent protein (GFP)-siRNA carrier to lung cells harbored with β(2)-adrenergic receptor, and remarkably enhanced the efficacy of gene silence in vitro and in the lung of enhanced green fluorescent protein (EGFP)-transgenic mice in vivo. (iii) It was proved that this chitosan-based polymer was able to provide both the pDNA and siRNA with the protection against destructive shear forces generated by the mesh-based nebulizers. Aerosol treatment improved the nanoparticle size distribution, which should be in favor of enhancing the transfection efficiency. We suggest a potential application of the chitosan-derived nanodelivery vehicle (SGCS) in RNA interference therapy for lung diseases via aerosol inhalation.

RNA-Cleaving DNA Enzymes and Their Potential Therapeutic Applications as Antibacterial and Antiviral Agents

DNA catalysts are synthetic single-stranded DNA molecules that have been identified by in vitro selection from random sequence DNA pools. The most prominent representatives of DNA catalysts (also known as DNA enzymes, deoxyribozymes, or DNAzymes) catalyze the site-specific cleavage of RNA substrates. Two distinct groups of RNA-cleaving DNA enzymes are the 10-23 and 8-17 enzymes. A typical RNA-cleaving DNA enzyme consists of a catalytic core and two short binding arms which form Watson–Crick base pairs with the RNA targets. RNA cleavage is usually achieved with the assistance of metal ions such as Mg²⁺, Ca²⁺, Mn²⁺, Pb²⁺, or Zn²⁺, but several chemically modified DNA enzymes can cleave RNA in the absence of divalent metal ions. A number of studies have shown the use of 10-23 DNA enzymes for modest downregulation of therapeutically relevant RNA targets in cultured cells and in whole mammals. Here we focus on mechanistic aspects of RNA-cleaving DNA enzymes and their potential to silence therapeutically appealing viral and bacterial gene targets. We also discuss delivery options and challenges involved in DNA enzyme-based therapeutic strategies.