pH-triggered nanoparticle mediated delivery of siRNA to liver cells in vitro and in vivo

How Advanced are Nanocarriers for Effective Subretinal Injection?

Subretinal injection (SR injection) is a commonly used method of ocular drug delivery and has been mainly applied for the treatment of neovascular age-associated macular degeneration (nAMD) and sub-macular hemorrhage (SMH) caused by nAMD, as well as various types of hereditary retinopathies (IRD) such as Stargardt's disease (STGD), retinitis pigmentosa (RP), and a series of fundus diseases such as Leber's congenital dark haze (LCA), choroidal defects, etc. The commonly used carriers of SR injection are mainly divided into viral and non-viral vectors. Leber's congenital amaurosis (LCA), choroidal agenesis, and a series of other fundus diseases are also commonly treated using SR injection. The commonly used vectors for SR injection are divided into two categories: viral vectors and non-viral vectors. Viral vectors are a traditional class of SR injection drug carriers that have been extensively studied in clinical treatment, but they still have many limitations that cannot be ignored, such as poor reproduction efficiency, small loading genes, and triggering of immune reactions. With the rapid development of nanotechnology in the treatment of ocular diseases, nanovectors have become a research hotspot in the field of non-viral vectors. Nanocarriers have numerous attractive properties such as low immunogenicity, robust loading capacity, stable structure, and easy modification. These valuable features imply greater safety, improved therapeutic efficacy, longer duration, and more flexible indications. In recent years, there has been a growing interest in nanocarriers, which has led to significant advancements in the treatment of ocular diseases. Nanocarriers have not only successfully addressed clinical problems that viral vectors have failed to overcome but have also introduced new therapeutic possibilities for certain classical disease types. Nanocarriers offer undeniable advantages over viral vectors. This review discusses the advantages of subretinal (SR) injection, the current status of research, and the research hotspots of gene therapy with viral vectors. It focuses on the latest progress of nanocarriers in SR injection and enumerates the limitations and future perspectives of nanocarriers in the treatment of fundus lesions. Furthermore, this review also covers the research progress of nanocarriers in the field of subretinal injection and highlights the value of nanocarrier-mediated SR injection in the treatment of fundus disorders. Overall, it provides a theoretical basis for the application of nanocarriers in SR injection.

RNA vaccines for cancer: Principles to practice

Vaccines are the most impactful medicines to improve health. Though potent against pathogens, vaccines for cancer remain an unfulfilled promise. However, recent advances in RNA technology coupled with scientific and clinical breakthroughs have spurred rapid discovery and potent delivery of tumor antigens at speed and scale, transforming cancer vaccines into a tantalizing prospect. Yet, despite being at a pivotal juncture, with several randomized clinical trials maturing in upcoming years, several critical questions remain: which antigens, tumors, platforms, and hosts can trigger potent immunity with clinical impact? Here, we address these questions with a principled framework of cancer vaccination from antigen detection to delivery. With this framework, we outline features of emergent RNA technology that enable rapid, robust, real-time vaccination with somatic mutation-derived neoantigens-an emerging "ideal" antigen class-and highlight latent features that have sparked the belief that RNA could realize the enduring vision for vaccines against cancer.

A Comprehensive Review of Small Interfering RNAs (siRNAs): Mechanism, Therapeutic Targets, and Delivery Strategies for Cancer Therapy

Small interfering RNA (siRNA) delivery by nanocarriers has been identified as a promising strategy in the study and treatment of cancer. Short nucleotide sequences are synthesized exogenously to create siRNA, which triggers RNA interference (RNAi) in cells and silences target gene expression in a sequence-specific way. As a nucleic acid-based medicine that has gained popularity recently, siRNA exhibits novel potential for the treatment of cancer. However, there are still many obstacles to overcome before clinical siRNA delivery devices can be developed. In this review, we discuss prospective targets for siRNA drug design, explain siRNA drug properties and benefits, and give an overview of the current clinical siRNA therapeutics for the treatment of cancer. Additionally, we introduce the siRNA chemical modifications and delivery systems that are clinically sophisticated and classify bioresponsive materials for siRNA release in a methodical manner. This review will serve as a reference for researchers in developing more precise and efficient targeted delivery systems, promoting ongoing advances in clinical applications.

EVAnalyzer: High content imaging for rigorous characterisation of single extracellular vesicles using standard laboratory equipment and a new open-source ImageJ/Fiji plugin

Extracellular vesicle (EV) research increasingly demands for quantitative characterisation at the single vesicle level to address heterogeneity and complexity of EV subpopulations. Emerging, commercialised technologies for single EV analysis based on, for example, imaging flow cytometry or imaging after capture on chips generally require dedicated instrumentation and proprietary software not readily accessible to every lab. This limits their implementation for routine EV characterisation in the rapidly growing EV field. We and others have shown that single vesicles can be detected as light diffraction limited fluorescent spots using standard confocal and widefield fluorescence microscopes. Advancing this simple strategy into a process for routine EV quantitation, we developed 'EVAnalyzer', an ImageJ/Fiji (Fiji is just ImageJ) plugin for automated, quantitative single vesicle analysis from imaging data. Using EVAnalyzer, we established a robust protocol for capture, (immuno-)labelling and fluorescent imaging of EVs. To exemplify the application scope, the process was optimised and systematically tested for (i) quantification of EV subpopulations, (ii) validation of EV labelling reagents, (iii) in situ determination of antibody specificity, sensitivity and species cross-reactivity for EV markers and (iv) optimisation of genetic EV engineering. Additionally, we show that the process can be applied to synthetic nanoparticles, allowing to determine siRNA encapsulation efficiencies of lipid-based nanoparticles (LNPs) and protein loading of SiO2 nanoparticles. EVAnalyzer further provides a pipeline for automated quantification of cell uptake at the single cell-single vesicle level, thereby enabling high content EV cell uptake assays and plate-based screens. Notably, the entire procedure from sample preparation to the final data output is entirely based on standard reagents, materials, laboratory equipment and open access software. In summary, we show that EVAnalyzer enables rigorous characterisation of EVs with generally accessible tools. Since we further provide the plugin as open-source code, we expect EVAnalyzer to not only be a resource of immediate impact, but an open innovation platform for the EV and nanoparticle research communities.

Emerging Approaches for Enabling RNAi Therapeutics

RNA interference (RNAi) is a primitive evolutionary mechanism developed to escape incorporation of foreign genetic material. siRNA has been instrumental in achieving the therapeutic potential of RNAi by theoretically silencing any gene of interest in a reversible and sequence-specific manner. Extrinsically administered siRNA generally needs a delivery vehicle to span across different physiological barriers and load into the RISC complex in the cytoplasm in its functional form to show its efficacy. This review discusses the designing principles and examples of different classes of delivery vehicles that have proved to be efficient in RNAi therapeutics. We also briefly discuss the role of RNAi therapeutics in genetic and rare diseases, epigenetic modifications, immunomodulation and combination modality to inch closer in creating a personalized therapy for metastatic cancer. At the end, we present, strategies and look into the opportunities to develop efficient delivery vehicles for RNAi which can be translated into clinics.

A functional and self-assembling octyl-phosphonium-tagged esculetin as an effective siRNA delivery agent

Herein, we document a self-assembling octyl-TPP tagged esculetin (Mito-Esc) as functionally active and as a novel small molecule siRNA delivery vector. While Mito-Esc itself induces selective breast cancer cell death, the amphiphilic nature of Mito-Esc delivers therapeutic siRNAs intracellularly without the need for any excipient to exacerbate the anti-proliferative effects.

Short interfering RNA (siRNA)-Based Therapeutics for Cartilage Diseases

Articular cartilage injury, as a hallmark of arthritic diseases, is difficult to repair and causes joint pain, stiffness, and loss of mobility. Over the years, the most significant problems for the drug-based treatment of arthritis have been related to drug administration and delivery. In recent years, much research has been devoted to developing new strategies for repairing or regenerating the damaged osteoarticular tissue. The RNA interference (RNAi) has been suggested to have the potential for implementation in targeted therapy in which the faulty gene can be edited by delivering its complementary Short Interfering RNA (siRNA) at the post-transcriptional stage. The successful editing of a specific gene by the delivered siRNA might slow or halt osteoarthritic diseases without side effects caused by chemical inhibitors. However, cartilage siRNA delivery remains a challenging objective because cartilage is an avascular and very dense tissue with very low permeability. Furthermore, RNA is prone to degradation by serum nucleases (such as RNase H and RNase A) due to an extra hydroxyl group in its phosphodiester backbone. Therefore, successful delivery is the first and most crucial requirement for efficient RNAi therapy. Nanomaterials have emerged as highly advantage tools for these studies, as they can be engineered to protect siRNA from degrading, address barriers in siRNA delivery to joints, and target specific cells. This review will discuss recent breakthroughs of different siRNA delivery technologies for cartilage diseases.

Advanced Therapeutics, Vaccinations, and Precision Medicine in the Treatment and Management of Chronic Hepatitis B Viral Infections; Where Are We and Where Are We Going?

The management of chronic hepatitis B virus (CHB) infection is an area of massive unmet clinical need worldwide. In spite of the development of powerful nucleoside/nucleotide analogue (NUC) drugs, and the widespread use of immune stimulators such as interferon-alpha (IFNα) or PEGylated interferon-alpha (PEG-IFNα), substantial improvements in CHB standards of care are still required. We believe that the future for CHB treatment now rests with advanced therapeutics, vaccination, and precision medicine, if all are to bring under control this most resilient of virus infections. In spite of a plethora of active drug treatments, anti-viral vaccinations and diagnostic techniques, the management of CHB infection remains unresolved. The reason for this is the very complexity of the virus replication cycle itself, giving rise to multiple potential targets for therapeutic intervention some of which remain very intractable indeed. Our review is focused on discussing the potential impact that advanced therapeutics, vaccinations and precision medicine could have on the future management of CHB infection. We demonstrate that advanced therapeutic approaches for the treatment of CHB, in the form of gene and immune therapies, together with modern vaccination strategies, are now emerging rapidly to tackle the limitations of current therapeutic approaches to CHB treatment in clinic. In addition, precision medicine approaches are now gathering pace too, starting with personalized medicine. On the basis of this, we argue that the time has now come to accelerate the design and creation of precision therapeutic approaches (PTAs) for CHB treatment that are based on advanced diagnostic tools and nanomedicine, and which could maximize CHB disease detection, treatment, and monitoring in ways that could genuinely eliminate CHB infection altogether.

Fluorescent Peptide Dendrimers for siRNA Transfection: Tracking pH Responsive Aggregation, siRNA Binding, and Cell Penetration

Transfecting nucleic acids into various cells is a key procedure in biological research also envisioned for therapeutic applications. In our effort to obtain simple reagents that would be readily accessible from commercial building blocks, we recently reported peptide dendrimers as single component siRNA transfection reagents accessible in pure form by solid-phase peptide synthesis. Here, we extend our studies of these dendrimers by identifying analogs bearing a coumarin or BODIPY fluorescent label in their core and displaying comparable siRNA transfection efficiencies, pH dependent aggregation, siRNA binding, and secondary structures. Fluorescence resonance energy transfer (FRET) studies show that the dendrimers are tightly associated with siRNA within the formed nanoparticles at pH 7.4 but are released into solution at pH 5.0 and can participate in endosome escape by destabilizing the membrane at this pH value. Colocalization studies furthermore suggest that peptide dendrimers and siRNA remain tightly associated throughout the transfection process.

Advances in CRISPR/Cas9 Technology for in Vivo Translation

Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has revolutionized therapeutic gene editing by providing researchers with a new method to study and cure diseases previously considered untreatable. While the full range and power of CRISPR technology for therapeutics is being elucidated through in vitro studies, translation to in vivo studies is slow. To date there is no totally effective delivery strategy to carry CRISPR components to the target site in vivo. The complexity of in vivo delivery is furthered by the number of potential delivery methods, the different forms in which CRISPR can be delivered as a therapeutic, and the disease target and tissue type in question. There are major challenges and limitations to delivery strategies, and it is imperative that future directions are guided by well-conducted studies that consider the full effect these variables have on the eventual outcome. In this review we will discuss the advances of the latest in vivo CRISPR/Cas9 delivery strategies and highlight the challenges yet to be overcome.

Lipid Nanoparticles for Delivery of Therapeutic RNA Oligonucleotides

Gene therapy is an exciting field that has the potential to address emerging scientific and therapeutic tasks. RNA-based gene therapy has made remarkable progress in recent decades. Nevertheless, efficient targeted delivery of RNA therapeutics is still a prerequisite for entering the clinics. In this review, we introduce current delivery methods for RNA gene therapeutics based on lipid nanoparticles (LNPs). We focus on the clinical appeal of recent RNA NPs and discuss existing challenges of fabrication and screening LNP candidates for effective translation into drugs of human metabolic diseases and cancer.

pH-Sensitive Polymers as Dynamic Mediators of Barriers to Nucleic Acid Delivery

The nonviral delivery of exogenous nucleic acids (NA) into cells for therapeutic purposes has rapidly matured into tangible clinical impact. Synthetic polymers are particularly attractive vectors for NA delivery due to their relatively inexpensive production compared to viral alternatives and their highly tailorable chemical properties; indeed, many preclinical investigations have revealed the primary biological barriers to nonviral NA delivery by systematically varying polymeric material properties. This review focuses on applications of pH-sensitive chemistries that enable polymeric vectors to serially address multiple biological barriers to NA delivery. In particular, we focus on recent innovations with in vivo evaluation that dynamically enable colloidal stability, cellular uptake, endosomal escape, and nucleic acid release. We conclude with a summary of successes to date and projected areas for impactful future research.

Hyaluronic Acid Surface Modified Liposomes Prepared via Orthogonal Aminoxy Coupling: Synthesis of Nontoxic Aminoxylipids Based on Symmetrically α-Branched Fatty Acids, Preparation of Liposomes by Microfluidic Mixing, and Targeting to Cancer Cells Expressing CD44

New synthetic aminoxy lipids are designed and synthesized as building blocks for the formulation of functionalized nanoliposomes by microfluidization using a NanoAssemblr. Orthogonal binding of hyaluronic acid onto the outer surface of functionalized nanoliposomes via aminoxy coupling ( N-oxy ligation) is achieved at hemiacetal function of hyaluronic acid and the structure of hyaluronic acid-liposomes is visualized by transmission electron microscopy and cryotransmission electron microscopy. Observed structures are in a good correlation with data obtained by dynamic light scattering (size and ζ-potential). In vitro experiments on cell lines expressing CD44 receptors demonstrate selective internalization of fluorochrome-labeled hyaluronic acid-liposomes, while cells with down regulated CD44 receptor levels exhibit very low internalization of hyaluronic acid-liposomes. A method based on microfluidization mixing was developed for preparation of monodispersive unilamellar liposomes containing aminoxy lipids and orthogonal binding of hyaluronic acid onto the liposomal surface was demonstrated. These hyaluronic acid-liposomes represent a potentially new drug delivery platform for CD44-targeted anticancer drugs as well as for immunotherapeutics and vaccines.

Characterization and evaluation of a peptide-based siRNA delivery system in vitro

Since its inception more than a decade ago, gene silencing mediated by double-stranded small interfering RNA (siRNA) has been widely investigated as a potential therapeutic approach for a variety of diseases. However, the use of siRNA is hampered by its rapid degradation and poor cellular uptake in vitro and in vivo. Recently, peptide-based carriers have been applied to siRNA delivery, as an alternative to the traditional delivery systems. Here, a histidine-containing amphipathic amino acid pairing peptide, C6M3, which can form complexes with siRNA, was used as a new siRNA delivery system. This peptide exhibited a high affinity for siRNA and ability to efficiently deliver siRNA into the cells. The interaction of C6M3 with siRNA was investigated to determine the loading capacity of C6M3 at different peptide/siRNA molar ratios. At C6M3/siRNA molar ratio of 10/1, siRNA molecules were entirely associated with C6M3 as indicated by a gel electrophoretic assay and further confirmed by zeta potential analysis. The particle size distribution of the C6M3-siRNA complexes was studied using dynamic light scattering, which showed an intensity-based size distribution peaked approximately at 100 nm in RNase-free water and 220 nm in the Opti-MEM medium. C6M3 adopted a helical secondary structure in RNase-free water and became more so after forming complexes with siRNA. The interaction of siRNA with C6M3 is an entropy-driven spontaneous process, as determined by isothermal titration calorimetry (ITC) study. The efficiency of cellular uptake of the siRNA complexes at different C6M3/siRNA molar ratios was evaluated, and the results showed that C6M3 promoted efficient cellular uptake of siRNA into cells. Furthermore, a significant level of GAPDH gene silencing efficiency (69%) was achieved in CHO-K1 cells, with minimal cytotoxicity.

Nanomedicine therapeutics and diagnostics are the goal

Understanding and exploiting molecular mechanisms in biology is central to chemical biology. In 20 years, chemical biology research has advanced from simple mechanistic studies using isolated biological macromolecules to molecular-level and nanomolecular-level mechanistic studies involving whole organisms. This review documents the best of my personal and collaborative academic research work that has made use of a solid organic chemistry and chemical biology approach toward nanomedicine, in which my focus has been on the design, creation and use of synthetic, self-assembly lipid-based nanoparticle technologies for the functional delivery of active pharmaceutical ingredients to target cells in vivo. This research is now leading to precision therapeutics approaches (PTAs) for the treatment of diseases that may define the future of nanomedicine.

Stimuli-responsive liposomes for drug delivery

The ultimate goal of drug delivery is to increase the bioavailability and reduce the toxic side effects of the active pharmaceutical ingredient (API) by releasing them at a specific site of action. In the case of antitumor therapy, association of the therapeutic agent with a carrier system can minimize damage to healthy, nontarget tissues, while limit systemic release and promoting long circulation to enhance uptake at the cancerous site due to the enhanced permeation and retention effect (EPR). Stimuli-responsive systems have become a promising way to deliver and release payloads in a site-selective manner. Potential carrier systems have been derived from a wide variety of materials, including inorganic nanoparticles, lipids, and polymers that have been imbued with stimuli-sensitive properties to accomplish triggered release based on an environmental cue. The unique features in the tumor microenvironment can serve as an endogenous stimulus (pH, redox potential, or unique enzymatic activity) or the locus of an applied external stimulus (heat or light) to trigger the controlled release of API. In liposomal carrier systems triggered release is generally based on the principle of membrane destabilization from local defects within bilayer membranes to effect release of liposome-entrapped drugs. This review focuses on the literature appearing between November 2008-February 2016 that reports new developments in stimuli-sensitive liposomal drug delivery strategies using pH change, enzyme transformation, redox reactions, and photochemical mechanisms of activation. WIREs Nanomed Nanobiotechnol 2017, 9:e1450. doi: 10.1002/wnan.1450 For further resources related to this article, please visit the WIREs website.

Self-Assembly of a Multifunctional Lipid With Core-Shell Dendrimer DNA Nanoparticles Enhanced Efficient Gene Delivery at Low Charge Ratios into RPE Cells

Development of safe and effective gene delivery systems is essential in treating ocular genetic disorders. A hybrid nonviral system composed of a multifunctional lipid ECO and a G4 nanoglobule was designed for efficient gene delivery into RPE cells at low charge ratios. This system formed stable DNA nanoparticles at low N/P ratios, exhibited low cytotoxicity, and induced higher GFP expression in ARPE-19 cells at N/P = 6. The hybrid nanoparticles mediated significant reporter gene GFP expression ex-vivo in the retina from wild type C57 mice and in vivo in BALB/c mice. These hybrid nanoparticles are promising for in vitro and in vivo gene delivery at low charge ratios.

Thermosensitive, near-infrared-labeled nanoparticles for topotecan delivery to tumors

Liposomal nanoparticles have proven to be versatile systems for drug delivery. However, the progress in clinic has been slower and less efficient than expected. This suggests a need for further development using carefully designed chemical components to improve usefulness under clinical conditions and maximize therapeutic effect. For cancer chemotherapy, PEGylated liposomes were the first nanomedicine to reach the market and have been used clinically for several years. Approaches toward targeted drug delivery using next generation "thermally triggered" nanoparticles are now in clinical trials. However, clinically tested thermosensitive liposomes (TSLs) lack the markers that allow tumor labeling and improved imaging for tissue specific applied hyperthermia. Here we describe the development of optically labeled TSLs for image guidance drug delivery and proof-of-concept results for their application in the treatment of murine xenograft tumors using the anticancer drug topotecan. These labeled TSLs also allow the simultaneous, real-time diagnostic imaging of nanoparticle biodistribution using a near-infrared (NIR; 750-950 nm) fluorophore coupled to a lipidic component of the lipid bilayer. When combined with multispectral fluorescence analysis, this allows for specific and high sensitivity tracking of the nanoparticles in vivo. The application of NIR fluorescence-labeled TSLs could have a transformative effect on future cancer chemotherapy.

Long non-coding RNAs: critical players in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a complex disease with multiple underlying pathogenic mechanisms caused by a variety of etiologic factors. Emerging evidence showed that long non-coding RNAs (lncRNAs), with size larger than 200 nucleotides (nt), play important roles in various types of cancer development and progression. In recent years, some dysregulated lncRNAs in HCC have been revealed and roles for several of them in HCC have been characterized. All these findings point to the potential of lncRNAs as prospective novel therapeutic targets in HCC. In this review, we summarize known dysregulated lncRNAs in HCC, and review potential biological roles and underlying molecular mechanisms of lncRNAs in HCC. Additionally, we discussed prospects of lncRNAs as potential biomarker and therapeutic target for HCC. In conclusion, this paper will help us gain better understanding of molecular mechanisms by which lncRNAs perform their function in HCC and also provide general strategies and directions for future research.

Delivery of RNAi therapeutics: work in progress

RNA interference (RNAi) therapeutics appear to offer substantial opportunities for future therapy. However, post-administration RNAi effectors are typically unable to reach disease target cells in vivo without the assistance of a delivery system or vector. The main focus of this review is on lipid-based nanoparticle (LNP) delivery systems in current research and development that have at least been shown to act as effective delivery systems for functional delivery of RNAi effectors to disease target cells in vivo. The potential utility of these LNP delivery systems is growing rapidly, and LNPs are emerging as the preferred synthetic delivery systems in preclinical studies and current nonviral RNAi effector clinical trials. Moreover, studies on LNP-mediated delivery in vivo are leading to the emergence of useful biophysical parameters and physical organic chemistry rules that provide a framework for understanding in vivo delivery behaviors and outcomes. These same parameters and rules should also suggest ways and means to develop next generations of LNPs with genuine utility and long-term clinical viability.

Delivering the promise of small ncRNA therapeutics

Small non-coding RNA (ncRNA) therapeutics make use of small ncRNA effectors for desired therapeutic purposes that are essentially short (10–20 kD) RNA segments. These small ncRNA effectors are potentially tremendously powerful therapeutic agents, but are typically unable to reach disease target cells in vivo without the assistance of a delivery system or vector. The main focus of this review is the use of lipid-based nanoparticles (LNPs) for the functional delivery of small ncRNA effectors in vivo. LNPs appear to be amongst the most effective delivery systems currently available for this purpose. Moreover, studies on LNP-mediated delivery in vivo are leading to the emergence of useful biophysical parameters and physical organic chemistry rules that provide a framework for understanding LNP-mediated in vivo delivery behaviors and outcomes. These same parameters and rules should also suggest ways and means to develop next generations of LNPs with genuine utility and long-term clinical viability.

MicroRNAs and drug resistance in prostate cancers

Prostate cancer is the second leading cause of cancer related death in American men. Androgen deprivation therapy (ADT) is used to treat patients with aggressive prostate cancers. After androgen deprivation therapy, prostate cancers slowly progress to an androgen-independent status. Taxanes (e.g., docetaxel) are used as standard treatments for androgen-independent prostate cancers. However, these chemotherapeutic agents will eventually become ineffective due to the development of drug resistance. A microRNA (miRNA) is a small noncoding RNA molecule, which can regulate gene expression at the post-transcription level. miRNAs elicit their effects by binding to the 3'-untranslated region (3'-UTR) of their target mRNAs, leading to the inhibition of translation or the degradation of the mRNAs. miRNAs have received increasing attention as targets for cancer therapy, as they can target multiple signaling pathways related to tumor progression, metastasis, invasion, and chemoresistance. Emerging evidence suggests that aberrant expression of miRNAs can lead to the development of resistant prostate cancers. Here, we discuss the roles of miRNAs in the development of resistant prostate cancers and their involvement in various drug resistant mechanisms including androgen signaling, apoptosis avoidance, multiple drug resistance (MDR) transporters, epithelialmesenchymal transition (EMT), and cancer stem cells (CSCs). In addition, we also discuss strategies for treating resistant prostate cancers by targeting specific miRNAs. Different delivery strategies are also discussed with focus on those that have been successfully used in human clinical trials.

Inhibition of hepatitis C virus in chimeric mice by short synthetic hairpin RNAs: sequence analysis of surviving virus shows added selective pressure of combination therapy

We have recently shown that a cocktail of two short synthetic hairpin RNAs (sshRNAs), targeting the internal ribosome entry site of hepatitis C virus (HCV) formulated with lipid nanoparticles, was able to suppress viral replication in chimeric mice infected with HCV GT1a by up to 2.5 log10 (H. Ma et al., Gastroenterology 146:63-66.e5, http://dx.doi.org/10.1053/j.gastro.2013.09.049) Viral load remained about 1 log10 below pretreatment levels 21 days after the end of dosing. We have now sequenced the HCV viral RNA amplified from serum of treated mice after the 21-day follow-up period. Viral RNA from the HCV sshRNA-treated groups was altered in sequences complementary to the sshRNAs and nowhere else in the 500-nucleotide sequenced region, while the viruses from the control group that received an irrelevant sshRNA had no mutations in that region. The ability of the most commonly selected mutations to confer resistance to the sshRNAs was confirmed in vitro by introducing those mutations into HCV-luciferase reporters. The mutations most frequently selected by sshRNA treatment within the sshRNA target sequence occurred at the most polymorphic residues, as identified from an analysis of available clinical isolates. These results demonstrate a direct antiviral activity with effective HCV suppression, demonstrate the added selective pressure of combination therapy, and confirm an RNA interference (RNAi) mechanism of action.

IMPORTANCE

This study presents a detailed analysis of the impact of treating a hepatitis C virus (HCV)-infected animal with synthetic hairpin-shaped RNAs that can degrade the virus's RNA genome. These RNAs can reduce the viral load in these animals by over 99% after 1 to 2 injections. The study results confirm that the viral rebound that often occurred a few weeks after treatment is due to emergence of a virus whose genome is mutated in the sequences targeted by the RNAs. The use of two RNA inhibitors, which is more effective than use of either one by itself, requires that any resistant virus have mutations in the targets sites of both agents, a higher hurdle, if the virus is to retain the ability to replicate efficiently. These results demonstrate a direct antiviral activity with effective HCV suppression, demonstrate the added selective pressure of combination therapy, and confirm an RNAi mechanism of action.

Formulated minimal-length synthetic small hairpin RNAs are potent inhibitors of hepatitis C virus in mice with humanized livers

Short synthetic hairpin RNAs (sshRNAs) (SG220 and SG273) that target the internal ribosome entry site of the hepatitis C virus (HCV) were formulated into lipid nanoparticles and administered intravenously to HCV-infected urokinase plasminogen activator-severe combined immunodeficient mice with livers repopulated with human hepatocytes (humanized livers). Weekly administration of 2.5 mg/kg of each sshRNA for 2 weeks resulted in a maximal mean reduction in viral load of 2.5 log10 from baseline. The viral load remained reduced by more than 90% at 14 days after the last dose was given. The sshRNAs were well tolerated and did not significantly increase liver enzyme levels. These findings indicate the in vivo efficacy of a synthetic RNA inhibitor against the HCV genome in reducing HCV infection.

Acid-degradable polymer-caged lipoplex (PCL) platform for siRNA delivery: facile cellular triggered release of siRNA

An acid-degradable polymer-caged lipoplex (PCL) platform consisting of a cationic lipoplex core and a biocompatible, pH-responsive polymer shell has been developed for the effective delivery of small interfering RNA (siRNA) through a combination of facile loading, rapid acid-triggered release, cellular internalization, and effective endosomal escape. In vitro testing of this degradable PCL delivery platform reveals ∼45- and ∼2.5-fold enhancement of enhanced green fluorescent protein knockdown in cancer cells in comparison to either free siRNA or siRNA-loaded non-acid-degradable lipoplex formulations, respectively.

Delivery materials for siRNA therapeutics

RNA interference (RNAi) has broad potential as a therapeutic to reversibly silence any gene. To achieve the clinical potential of RNAi, delivery materials are required to transport short interfering RNA (siRNA) to the site of action in the cells of target tissues. This Review provides an introduction to the biological challenges that siRNA delivery materials aim to overcome, as well as a discussion of the way that the most effective and clinically advanced classes of siRNA delivery systems, including lipid nanoparticles and siRNA conjugates, are designed to surmount these challenges. The systems that we discuss are diverse in their approaches to the delivery problem, and provide valuable insight to guide the design of future siRNA delivery materials.

Lipid-based nanoparticles in cancer diagnosis and therapy

Today, researchers are constantly developing new nanomaterials, nanodevices, and nanoparticles to meet unmet needs in the delivery of therapeutic agents and imaging agents for cancer therapy and diagnosis, respectively. Of particular interest here are lipid-based nanoparticles (LNPs) that are genuine particles (approximately 100 nm in dimension) assembled from varieties of lipid and other chemical components that act collectively to overcome biological barriers (biobarriers), in order for LNPs to preferentially accumulate in or around disease-target cells for the functional delivery of therapeutic agents for treatment or of imaging agents for diagnosis. The capabilities of these LNPs will clearly vary depending on functional requirements, but the nanoscale allows for an impressive level of diversity in capabilities to enable corresponding LNPs to address an equally diverse range of functional requirements. Accordingly, LNPs should be considered appropriate vehicles to provide an integrated, personalized approach to cancer diagnosis and therapy in future cancer disease management.