Specific Delivery of MiRNA for High Efficient Inhibition of Prostate Cancer by RNA Nanotechnology

RNA Nanotechnology for Codelivering High-Payload Nucleoside Analogs to Cancer with a Synergetic Effect

Nucleoside analogs are potent inhibitors for cancer treatment, but the main obstacles to their application in humans are their toxicity, nonspecificity, and lack of targeted delivery tools. Here, we report the use of RNA four-way junctions (4WJs) to deliver two nucleoside analogs, floxuridine (FUDR) and gemcitabine (GEM), with high payloads through routine and simple solid-state RNA synthesis and nanoparticle assembly. The design of RNA nanotechnology for the co-delivery of nucleoside analogs and the chemotherapeutic drug paclitaxel (PTX) resulted in synergistic effects and high efficacy in the treatment of Triple-Negative Breast Cancer (TNBC). The 4WJ-drug complexes were confirmed to have efficient tumor spontaneous targeting and no toxicity because the motility of RNA nanoparticles has been previously shown to enable these RNA-drug complexes to spontaneously accumulate in tumor blood vessels. The negative charge of RNA enables those RNA complexes that are not targeted to tumor vasculature to circulate in the blood and enter the urine through the kidney glomerulus, without accumulating in organs, therefore being nontoxic. Drug incorporation into RNA 4WJ can be precisely controlled with a defined loading amount, location, and ratio. The incorporation of nucleoside analogs into 4WJ only requires one step using nucleoside analogue phosphoramidites during solid-phase RNA synthesis, without the need for additional conjugation and purification processes.

Posterior eye delivery of angiogenesis-inhibiting RNA nanoparticles via subconjunctival injection

Neovascularization contributes to various posterior eye segment diseases such as age-related macular degeneration and diabetic retinopathy. RNA nanoparticles were demonstrated previously to enter the corneal and retinal cells after subconjunctival injection for ocular delivery. In the present study, antiangiogenic aptamers (anti-vascular endothelial growth factor (VEGF) and anti-angiopoietin-2 (Ang2) aptamers) were conjugated to RNA nanoparticles. The objectives were to investigate the clearance and distribution of these angiogenesis-inhibiting RNA nanoparticles after subconjunctival injection in vivo and their antiangiogenic effects for inhibiting ocular neovascularization in vitro. The results in the whole-body fluorescence imaging study showed that the clearance of RNA nanoparticles was size-dependent with no significant differences between RNA nanoparticles with and without the aptamers except for pRNA-3WJ. The distribution study of RNA nanoparticles by confocal microscopy of the dissected eye tissues in vivo indicated cell internalization of the larger RNA nanoparticles in the retina and retinal pigment epithelium after subconjunctival injection, and the larger nanoparticles with aptamers showed higher levels of cell internalization than those without. In the cell proliferation assay in vitro, RNA nanoparticles with multiple aptamers had higher antiangiogenic effects. With both longer retention time and high antiangiogenic effect, SQR-VEGF-Ang2 could be a promising RNA nanoparticle for posterior eye delivery.

RNA four-way junction (4WJ) for spontaneous cancer-targeting, effective tumor-regression, metastasis suppression, fast renal excretion and undetectable toxicity

The field of RNA therapeutics has been emerging as the third milestone in pharmaceutical drug development. RNA nanoparticles have displayed motile and deformable properties to allow for high tumor accumulation with undetectable healthy organ accumulation. Therefore, RNA nanoparticles have the potential to serve as potent drug delivery vehicles with strong anti-cancer responses. Herein, we report the physicochemical basis for the rational design of a branched RNA four-way junction (4WJ) nanoparticle that results in advantageous high-thermostability and -drug payload for cancer therapy, including metastatic tumors in the lung. The 4WJ nanostructure displayed versatility through functionalization with an anti-cancer chemical drug, SN38, for the treatment of two different cancer models including colorectal cancer xenograft and orthotopic lung metastases of colon cancer. The resulting 4WJ RNA drug complex spontaneously targeted cancers effectively for cancer inhibition with and without ligands. The 4WJ displayed fast renal excretion, rapid body clearance, and little organ accumulation with undetectable toxicity and immunogenicity. The safety parameters were documented by organ histology, blood biochemistry, and pathological analysis. The highly efficient cancer inhibition, undetectable drug toxicity, and favorable Chemical, Manufacturing, and Control (CMC) production of RNA nanoparticles document a candidate with high potential for translation in cancer therapy.

In Vitro and In Vivo Evaluation of the Pathology and Safety Aspects of Three- and Four-Way Junction RNA Nanoparticles

RNA therapeutics has advanced into the third milestone in pharmaceutical drug development, following chemical and protein therapeutics. RNA itself can serve as therapeutics, carriers, regulators, or substrates in drug development. Due to RNA's motile, dynamic, and deformable properties, RNA nanoparticles have demonstrated spontaneous targeting and accumulation in cancer vasculature and fast excretion through the kidney glomerulus to urine to prevent possible interactions with healthy organs. Furthermore, the negatively charged phosphate backbone of RNA results in general repulsion from negatively charged lipid cell membranes for further avoidance of vital organs. Thus, RNA nanoparticles can spontaneously enrich tumor vasculature and efficiently enter tumor cells via specific targeting, while those not entering the tumor tissue will clear from the body quickly. These favorable parameters have led to the expectation that RNA has low or little toxicity. RNA nanoparticles have been well characterized for their anticancer efficacy; however, little detail on RNA nanoparticle pathology and safety is known. Here, we report the in vitro and in vivo assessment of the pathology and safety aspects of different RNA nanoparticles including RNA three-way junction (3WJ) harboring 2'-F modified pyrimidine, folic acid, and Survivin siRNA, as well as the RNA four-way junction (4WJ) harboring 2'-F modified pyrimidine and 24 copies of SN38. Both animal models and patient serum were investigated. In vitro studies include hemolysis, platelet aggregation, complement activation, plasma coagulation, and interferon induction. In vivo studies include hematoxylin and eosin (H&E) staining, hematological and biochemical analysis as the serum profiling, and animal organ weight study. No significant toxicity, side effect, or immune responses were detected during the extensive safety evaluations of RNA nanoparticles. These results further complement previous cancer inhibition studies and demonstrate RNA nanoparticles as an effective and safe drug delivery vehicle for future clinical translations.

RNA nanostructures for targeted drug delivery and imaging

The RNA molecule plays a pivotal role in many biological processes by relaying genetic information, regulating gene expression, and serving as molecular machines and catalyzers. This inherent versatility of RNA has fueled significant advancements in the field of RNA nanotechnology, driving the engineering of complex nanoscale architectures toward biomedical applications, including targeted drug delivery and bioimaging. RNA polymers, serving as building blocks, offer programmability and predictability of Watson-Crick base pairing, as well as non-canonical base pairing, for the construction of nanostructures with high precision and stoichiometry. Leveraging the ease of chemical modifications to protect the RNA from degradation, researchers have developed highly functional and biocompatible RNA architectures and integrated them into preclinical studies for the delivery of payloads and imaging agents. This review offers an educational introduction to the use of RNA as a biopolymer in the design of multifunctional nanostructures applied to targeted delivery in vivo, summarizing physical and biological barriers along with strategies to overcome them. Furthermore, we highlight the most recent progress in the development of both small and larger RNA nanostructures, with a particular focus on imaging reagents and targeted cancer therapeutics in pre-clinical models and provide insights into the prospects of this rapidly evolving field.

Targeting lung cancer with clinically relevant EGFR mutations using anti-EGFR RNA aptamer

A significant fraction of non-small cell lung cancer (NSCLC) cases are due to oncogenic mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR). Anti-EGFR antibodies have shown limited clinical benefit for NSCLC, whereas tyrosine kinase inhibitors (TKIs) are effective, but resistance ultimately occurs. The current landscape suggests that alternative ligands that target wild-type and mutant EGFRs are desirable for targeted therapy or drug delivery development. Here we evaluate NSCLC targeting using an anti-EGFR aptamer (MinE07). We demonstrate that interaction sites of MinE07 overlap with clinically relevant antibodies targeting extracellular domain III and that MinE07 retains binding to EGFR harboring the most common oncogenic and resistance mutations. When MinE07 was linked to an anti-c-Met aptamer, the EGFR/c-Met bispecific aptamer (bsApt) showed superior labeling of NSCLC cells in vitro relative to monospecific aptamers. However, dual targeting in vivo did not improve the recognition of NSCLC xenografts compared to MinE07. Interestingly, biodistribution of Cy7-labeled bsApt differed significantly from Alexa Fluor 750-labeled bsApt. Overall, our findings demonstrate that aptamer formulations containing MinE07 can target ectopic lung cancer without additional stabilization or PEGylation and highlights the potential of MinE07 as a targeting reagent for the recognition of NSCLC harboring clinically relevant EGFRs.

3WJ RNA Nanoparticles-Aptamer Functionalized Exosomes From M2 Macrophages Target BMSCs to Promote the Healing of Bone Fractures

Up to now, impaired bone regeneration severely affects the healing of bone fractures, thus bringing tremendous suffering to patients. As a vital mediator between inflammatory response and bone regeneration, M2 macrophage-derived exosomes (M2-Exos) attenuate inflammation and promote tissue repair. However, due to a lack of specific targeting property, M2-Exos will be rapidly eliminated after systematic administration, thus compromising their effectiveness in promoting bone regeneration. To solve this hurdle, we initially harvested and characterized the pro-osteogenic properties of M2-Exos. A bone marrow mesenchymal stem cell (BMSC)-specific aptamer was synthesized and 3-way junction (3WJ) RNA nanoparticles were applied to conjugate the BMSC-specific aptamer and M2-Exos. In vitro assays revealed that M2-Exos bore the representative features of exosomes and significantly promoted the proliferation, migration, and osteogenic differentiation of BMSCs. 3WJ RNA nanoparticles-aptamer functionalized M2-Exos (3WJ-BMSCapt/M2-Exos) maintained the original physical characteristics of M2-Exos, but bore a high specific binding ability to BMSCs. Furthermore, when being systemically administered in the mice model with femoral bone fractures, these functionalized M2-Exos mainly accumulated at the bone fracture site with a slow release of exosomal cargo, thereby significantly accelerating the healing processes compared with the M2-Exos group. Our study indicated that the 3WJ-BMSCapt/M2-Exos with BMSCs targeting ability and controlled release would be a promising strategy to treat bone fractures.

Tumor targeting and therapeutic assessments of RNA nanoparticles carrying α9-nAChR aptamer and anti-miR-21 in triple-negative breast cancers

Triple-negative breast cancer (TNBC) is highly aggressive with a poor prognosis because of a lack of cell markers as drug targets. α9-Nicotinic acetylcholine receptor (nAChR) is expressed abundantly in TNBC; thus, it is a valuable biomarker for TNBC detection and treatment. In this study, we utilized thermodynamically stable three-way junction (3WJ) packaging RNA (pRNA) as the core to construct RNA nanoparticles with an α9-nAChR RNA aptamer as a targeting ligand and an anti-microRNA-21 (miR-21) as a therapeutic module. We compared the configuration of the two RNA nanoparticles and found that 3WJ-B-α9-nAChR-aptamer fluorescent RNA nanoparticles (3WJ-B-α9-apt-Alexa) exhibited better specificity for α9-nAChR in TNBC cells compared with 3WJ-C-α9-nAChR. Furthermore, 3WJ-B-α9-apt-Alexa bound more efficiently to TNBC patient-derived xenograft (PDX) tumors than 3WJ fluorescent RNA nanoparticles (3WJ-Alexa) with little or no accumulation in healthy organs after systemic injection in mice. Moreover, 3WJ-B-α9-nAChR-aptamer RNA nanoparticles carrying anti-miR-21 (3WJ-B-α9-apt-anti-miR-21) significantly suppressed TNBC-PDX tumor growth and induced cell apoptosis because of reduced miR-21 gene expression and upregulated the phosphatase and tensin homolog (PTEN) and programmed cell death 4 (PDCD4) proteins. In addition, no pathological changes were detected upon toxicity examination of treated mice. In conclusion, the 3WJ-B-α9-nAChR-aptamer RNA nanoparticles established in this study efficiently deliver therapeutic anti-miR-21, indicating their potential as a novel TNBC therapy.

Addressing the in vivo delivery of nucleic-acid nanostructure therapeutics

DNA and RNA nanostructures are being investigated as therapeutics, vaccines, and drug delivery systems. These nanostructures can be functionalized with guests ranging from small molecules to proteins with precise spatial and stoichiometric control. This has enabled new strategies to manipulate drug activity and to engineer devices with novel therapeutic functionalities. Although existing studies have offered encouraging in vitro or pre-clinical proof-of-concepts, establishing mechanisms of in vivo delivery is the new frontier for nucleic-acid nanotechnologies. In this review, we first provide a summary of existing literature on the in vivo uses of DNA and RNA nanostructures. Based on their application areas, we discuss current models of nanoparticle delivery, and thereby highlight knowledge gaps on the in vivo interactions of nucleic-acid nanostructures. Finally, we describe techniques and strategies for investigating and engineering these interactions. Together, we propose a framework to establish in vivo design principles and advance the in vivo translation of nucleic-acid nanotechnologies.

Revolving hexameric ATPases as asymmetric motors to translocate double-stranded DNA genome along one strand

DsDNA translocation through nanoscale pores is generally accomplished by ATPase biomotors. The discovery of the revolving dsDNA translocation mechanism, as opposed to rotation, in bacteriophage phi29 elucidated how ATPase motors move dsDNA. Revolution-driven, hexameric dsDNA motors have been reported in herpesvirus, bacterial FtsK, Streptomyces TraB, and T7 phage. This review explores the common relationship between their structure and mechanisms. Commonalities include moving along the 5'→3' strand, inchworm sequential action leading to an asymmetrical structure, channel chirality, channel size, and 3-step channel gating for controlling motion direction. The revolving mechanism and contact with one of the dsDNA strands addresses the historic controversy of dsDNA packaging using nicked, gapped, hybrid, or chemically modified DNA. These controversies surrounding dsDNA packaging activity using modified materials can be answered by whether the modification was introduced into the 3'→5' or 5'→3' strand. Perspectives concerning solutions to the controversy of motor structure and stoichiometry are also discussed.

New insights and options into the mechanisms and effects of combined targeted therapy and immunotherapy in prostate cancer

Chronic inflammation is believed to drive prostate carcinogenesis by producing reactive oxygen species or reactive nitrogen species to induce DNA damage. This effect might subsequently cause epigenetic and genomic alterations, leading to malignant transformation. Although established therapeutic advances have extended overall survival, tumors in patients with advanced prostate cancer are prone to metastasis, transformation into metastatic castration-resistant prostate cancer, and therapeutic resistance. The tumor microenvironment (TME) of prostate cancer is involved in carcinogenesis, invasion and drug resistance. A plethora of preclinical studies have focused on immune-based therapies. Understanding the intricate TME system in prostate cancer may hold much promise for developing novel therapies, designing combinational therapeutic strategies, and further overcoming resistance to established treatments to improve the lives of prostate cancer patients. In this review, we discuss nonimmune components and various immune cells within the TME and their putative roles during prostate cancer initiation, progression, and metastasis. We also outline the updated fundamental research focusing on therapeutic advances of targeted therapy as well as combinational options for prostate cancer.

Targeted delivery of RNAi to cancer cells using RNA-ligand displaying exosome

Exosome is an excellent vesicle for in vivo delivery of therapeutics, including RNAi and chemical drugs. The extremely high efficiency in cancer regression can partly be attributed to its fusion mechanism in delivering therapeutics to cytosol without endosome trapping. However, being composed of a lipid-bilayer membrane without specific recognition capacity for aimed-cells, the entry into nonspecific cells can lead to potential side-effects and toxicity. Applying engineering approaches for targeting-capacity to deliver therapeutics to specific cells is desirable. Techniques with chemical modification in vitro and genetic engineering in cells have been reported to decorate exosomes with targeting ligands. RNA nanoparticles have been used to harbor tumor-specific ligands displayed on exosome surface. The negative charge reduces nonspecific binding to vital cells with negatively charged lipid-membrane due to the electrostatic repulsion, thus lowering the side-effect and toxicity. In this review, we focus on the uniqueness of RNA nanoparticles for exosome surface display of chemical ligands, small peptides or RNA aptamers, for specific cancer targeting to deliver anticancer therapeutics, highlighting recent advances in targeted delivery of siRNA and miRNA that overcomes the previous RNAi delivery roadblocks. Proper understanding of exosome engineering with RNA nanotechnology promises efficient therapies for a wide range of cancer subtypes.

Preparation, characterisation, and in vitro cancer-suppression function of RNA nanoparticles carrying miR-301b-3p Inhibitor

BACKGROUND

Multidrug resistance is the biggest barrier on the way to chemotherapy for lung adenocarcinoma (LUAD). For some LUAD patients with cisplatin (DDP) resistance and poor prognoses, the authors put forward RNA nanoparticles (NPs) carrying miR-301b-3p Inhibitor.

METHODS

The NPs were composed of miR-301b-3p, A549 aptamer (A549apt), and Cyanine 5 in a bottom-up manner with a 3-way-junction (3WJ) structure. Diameter, assembly process, and morphology of NPs were observed by Dynamic Light Scattering, Native-Polyacrylamide Gel Electrophoresis, and Atomic Force Microscopy. Cell internalisation, toxicity, proliferation, migration, invasion, and apoptosis were assayed by confocal laser scanning microscope, CCK8, colony formation assay, Transwell, western blot, and flow cytometry.

RESULTS

3WJ-apt-miR was evenly distributed, with diameter of 19.61 ± 0.49 nm and triangular branching structures. The accurate delivery of this NP in vivo was ensured by A549 aptamer featuring specific targeting, with smaller side effects than traditional chemotherapy. Such nanomaterials were effectively internalized by cancer cells, with normal cell activity intact. Cancer cell proliferation, invasion, and migration were suppressed, and DDP sensitivity was enhanced, causing DNA damage and facilitating apoptosis of DDP-resistant cells.

CONCLUSION

Based on RNA self-assembling, the authors researched the effect of miRNA on DDP sensitivity in LUAD regarding gene regulation. 3WJ-apt-miR paves the way for clinical tumour therapy.

Nucleic acid-based artificial nanocarriers for gene therapy

Nucleic acid nanotechnology is a powerful tool in the fields of biosensing and nanomedicine owing to their high editability and easy synthesis and modification. Artificial nucleic acid nanostructures have become an emerging research hotspot as gene carriers with low cytotoxicity and immunogenicity for therapeutic approaches. In this review, recent progress in the design and functional mechanisms of nucleic acid-based artificial nano-vectors especially for exogenous siRNA and antisense oligonucleotide delivery is summarized. Different types of DNA nanocarriers, including DNA junctions, tetrahedrons, origami, hydrogels and scaffolds, are introduced. The enhanced targeting strategies to improve the delivery efficacy are demonstrated. Furthermore, RNA based gene nanocarrier systems by self-assembly of short strands, rolling circle transcription, chemical crosslinking and using RNA motifs and DNA-RNA hybrids are demonstrated. Finally, the outlook and potential challenges are highlighted. The nucleic acid-based artificial nanocarriers offer a promising and precise tool for gene delivery and therapy.

Therapeutic potential of targeting mirnas to prostate cancer tumors: using psma as an active target

Prostate cancer (PC) is a commonly diagnosed malignancy in men and is associated with high mortality rates. Current treatments for PC include surgery, chemotherapy, and radiation therapy. However, recent advances in targeted delivery systems have yielded promising new approaches to PC treatment. As PC epithelial cells express high levels of prostate-specific membrane antigen (PSMA) on the cell surface, new drug conjugates focused on PSMA targeting have been developed. microRNAs (miRNAs) are small noncoding RNAs that regulate posttranscriptional gene expression in cells and show excellent possibilities for use in developing new therapeutics for PC. PSMA-targeted therapies based on a miRNA payload and that selectively target PC cells enhances therapeutic efficacy without eliciting damage to normal surrounding tissue. This review discusses the rationale for utilizing miRNAs to target PSMA, revealing their potential in therapeutic approaches to PC treatment. Different delivery systems for miRNAs and challenges to miRNA therapy are also explored.

Aptamers as Theragnostic Tools in Prostate Cancer

Despite of the capacity that several drugs have for specific inhibition of the androgen receptor (AR), in most cases, PCa progresses to an androgen-independent stage. In this context, the development of new targeted therapies for prostate cancer (PCa) has remained as a challenge. To overcome this issue, new tools, based on nucleic acids technology, have been developed. Aptamers are small oligonucleotides with a three-dimensional structure capable of interacting with practically any desired target, even large targets such as mammalian cells or viruses. Recently, aptamers have been studied for treatment and detection of many diseases including cancer. In PCa, numerous works have reported their use in the development of new approaches in diagnostics and treatment strategies. Aptamers have been joined with drugs or other specific molecules such as silencing RNAs (aptamer–siRNA chimeras) to specifically reduce the expression of oncogenes in PCa cells. Even though these studies have shown good results in the early stages, more research is still needed to demonstrate the clinical value of aptamers in PCa. The aim of this review was to compile the existing scientific literature regarding the use of aptamers in PCa in both diagnosis and treatment studies. Since Prostate-Specific Membrane Antigen (PSMA) aptamers are the most studied type of aptamers in this field, special emphasis was given to these aptamers.

The dynamic, motile and deformative properties of RNA nanoparticles facilitate the third milestone of drug development

Besides mRNA, rRNA, and tRNA, cells contain many other noncoding RNA that display critical roles in the regulation of cellular functions. Human genome sequencing revealed that the majority of non-protein-coding DNA actually codes for non-coding RNAs. The dynamic nature of RNA results in its motile and deformative behavior. These conformational transitions such as the change of base-pairing, breathing within complemented strands, and pseudoknot formation at the 2D level as well as the induced-fit and conformational capture at the 3D level are important for their biological functions including regulation, translation, and catalysis. The dynamic, motile and catalytic activity has led to a belief that RNA is the origin of life. We have recently reported that the deformative property of RNA nanoparticles enhances their penetration through the leaky blood vessel of cancers which leads to highly efficient tumor accumulation. This special deformative property also enables RNA nanoparticles to pass the glomerulus, overcoming the filtration size limit, resulting in fast renal excretion and rapid body clearance, thus low or no toxicity. The biodistribution of RNA nanoparticles can be further improved by the incorporation of ligands for cancer targeting. In addition to the favorable biodistribution profiles, RNA nanoparticles possess other properties including self-assembly, negative charge, programmability, and multivalency; making it a great material for pharmaceutical applications. The intrinsic negative charge of RNA nanoparticles decreases the toxicity of drugs by preventing nonspecific binding to the negative charged cell membrane and enhancing the solubility of hydrophobic drugs. The polyvalent property of RNA nanoparticles allows the multi-functionalization which can apply to overcome drug resistance. This review focuses on the summary of these unique properties of RNA nanoparticles, which describes the mechanism of RNA dynamic, motile and deformative properties, and elucidates and prepares to welcome the RNA therapeutics as the third milestone in pharmaceutical drug development.

Role of Nano-miRNAs in Diagnostics and Therapeutics

MicroRNAs (miRNA) are key regulators of gene expression, controlling different biological processes such as cellular development, differentiation, proliferation, metabolism, and apoptosis. The relationships between miRNA expression and the onset and progression of different diseases, such as tumours, cardiovascular and rheumatic diseases, and neurological disorders, are well known. A nanotechnology-based approach could match miRNA delivery and detection to move beyond the proof-of-concept stage. Different kinds of nanotechnologies can have a major impact on the diagnosis and treatment of miRNA-related diseases such as cancer. Developing novel methodologies aimed at clinical practice represents a big challenge for the early diagnosis of specific diseases. Within this context, nanotechnology represents a wide emerging area at the forefront of research over the last two decades, whose potential has yet to be fully attained. Nanomedicine, derived from nanotechnology, can exploit the unique properties of nanometer-sized particles for diagnostic and therapeutic purposes. Through nanomedicine, specific treatment to counteract only cancer-cell proliferation will be improved, while leaving healthy cells intact. In this review, we dissect the properties of different nanocarriers and their roles in the early detection and treatment of cancer.

Perspectives of using microRNA-loaded nanocarriers for epigenetic reprogramming of drug resistant colorectal cancers

Epigenetic regulation by microRNAs (miRs) demonstrated a promising therapeutic potential of these molecules to regulate genetic activity in different cancers, including colorectal cancers (CRCs). The RNA-based therapy does not change genetic codes in tumor cells but can silence oncogenes and/or reactivate inhibited tumor suppressor genes. In many cancers, specific miRs were shown to promote or stop tumor progression. Among confirmed and powerful epigenetic regulators of colon carcinogenesis and development of resistance are onco-miRs, which include let-7, miR-21, miR-22, miR-23a, miR-27a, miR-34, miR-92, miR-96, miR-125b, miR-135b, miR-182, miR-200c, miR-203, miR-221, miR-421, miR-451, and others. Moreover, various tumor-suppressor miRs (miR-15b-5b, miR-18a, miR-20b, miR-22, miR-96, miR-139-5p, miR-145, miR-149, miR-197, miR-199b, miR-203, miR-214, miR-218, miR-320, miR-375-3p, miR-409-3p, miR-450b-5p, miR-494, miR-577, miR-874, and others) were found silenced in drug-resistant CRCs. Re-expression of tumor suppressor miR is complicated by the chemical nature of miRs that are not long-lasting compounds and require protection from the enzymatic degradation. Several recent studies explored application of miRs using nanocarrier complexes. This study critically describes the most successfully tested nanoparticle complexes used for intracellular delivery of nuclear acids and miRs, including micelles, liposomes, inorganic and polymeric NPs, dendrimers, and aptamers. Nanocarriers shield incorporated miRs and improve the agent stability in circulation. Attachment of antibodies and/or specific peptide or ligands facilitates cell-targeted miR delivery. Addressing in vivo challenges, a broad spectrum of non-toxic materials has been tested and indicated reliable advantages of lipid-based (lipoplexes) and polymer-based liposomes. Recent cutting-edge developments indicated that lipid-based complexes with multiple cargo, including several miRs, are the most effective approach to eradicate drug-resistant tumors. Focusing on CRC-specific miRs, this review provides a guidance and insights towards the most promising direction to achieve dramatic reduction in tumor growth and metastasis using miR-nanocarrier complexes.

Anhydrous Nucleic Acid Nanoparticles for Storage and Handling at Broad Range of Temperatures

Recent advances in nanotechnology now allow for the methodical implementation of therapeutic nucleic acids (TNAs) into modular nucleic acid nanoparticles (NANPs) with tunable physicochemical properties which can match the desired biological effects, provide uniformity, and regulate the delivery of multiple TNAs for combinatorial therapy. Despite the potential of novel NANPs, the maintenance of their structural integrity during storage and shipping remains a vital issue that impedes their broader applications. Cold chain storage is required to maintain the potency of NANPs in the liquid phase, which greatly increases transportation costs. To promote long-term storage and retention of biological activities at higher temperatures (e.g., +50 °C), a panel of representative NANPs is first exposed to three different drying mechanisms-vacuum concentration (SpeedVac), lyophilization (Lyo), and light-assisted drying (LAD)-and then rehydrated and analyzed. While SpeedVac primarily operates using heat, Lyo avoids temperature increases by taking advantage of pressure reduction and LAD involves a near-infrared laser for uniform drying in the presence of trehalose. This work compares and defines refinements crucial in formulating an optimal strategy for producing stable, fully functional NANPs and presents a forward advancement in their development for clinical applications.

Modulating microRNAs in cancer: Next-generation therapies

MicroRNAs (miRNAs) are a class of endogenously expressed non-coding regulators of the genome with an ability to mediate a variety of biological and pathological processes. There is growing evidence demonstrating frequent dysregulation of microRNAs in cancer cells, which is associated with tumor initiation, development, migration, invasion, resisting cell death, and drug resistance. Studies have shown that modulation of these small RNAs is a novel and promising therapeutic tool in the treatment of a variety of diseases, especially cancer, due to their broad influence on multiple cellular processes. However, suboptimal delivery of the appropriate miRNA to the cancer sites, quick degradation by nucleases in the blood circulation, and off target effects have limited their research and clinical applications. Therefore, there is a pressing need to improve the therapeutic efficacy of miRNA modulators, while at the same time reducing their toxicities. Several delivery vehicles for miRNA modulators have been shown to be effective in vitro and in vivo. In this review, we will discuss the role and importance of miRNAs in cancer and provide perspectives on currently available carriers for miRNA modulation. We will also summarize the challenges and prospects for the clinical translation of miRNA-based therapeutic strategies.

Self-Assembling Nucleic Acid Nanostructures Functionalized with Aptamers

Researchers have worked for many decades to master the rules of biomolecular design that would allow artificial biopolymer complexes to self-assemble and function similarly to the diverse biochemical constructs displayed in natural biological systems. The rules of nucleic acid assembly (dominated by Watson-Crick base-pairing) have been less difficult to understand and manipulate than the more complicated rules of protein folding. Therefore, nucleic acid nanotechnology has advanced more quickly than de novo protein design, and recent years have seen amazing progress in DNA and RNA design. By combining structural motifs with aptamers that act as affinity handles and add powerful molecular recognition capabilities, nucleic acid-based self-assemblies represent a diverse toolbox for use by bioengineers to create molecules with potentially revolutionary biological activities. In this review, we focus on the development of self-assembling nucleic acid nanostructures that are functionalized with nucleic acid aptamers and their great potential in wide ranging application areas.

The Role of miR-23b in Cancer and Autoimmune Disease

Short-stranded miRNAs are single-stranded RNA molecules involved in the regulation of gene expression. miRNAs are involved in a variety of cellular physiological processes, including cell proliferation, differentiation, and apoptosis. miR-23b have been identified to act both as oncogenes and as tumor suppressors. In addition, miR-23b is related to inflammation resistance to various autoimmune diseases and restrained inflammatory cell migration. The characterization of the specific alterations in the patterns of miR-23b expression in cancer and autoimmune disease has great potential for identifying biomarkers for early disease diagnosis, as well as for potential therapeutic intervention in various diseases. In this review, we summarize the ever-expanding role of miR-23b and its target genes in different models and offer insight into how this multifunctional miRNA modulates tumor cell proliferation and apoptosis or inflammatory cell activation, differentiation, and migration.

Functional and Clinical Significance of Dysregulated microRNAs in Liver Cancer

Liver cancer is the leading cause of cancer-related mortality in the world. This mainly reflects the lack of early diagnosis tools and effective treatment methods. MicroRNAs (miRNAs) are a class of non-transcribed RNAs, some of which play important regulatory roles in liver cancer. Here, we discuss microRNAs with key impacts on liver cancer, such as miR-122, miR-21, miR-214, and miR-199. These microRNAs participate in various physiological regulatory pathways of liver cancer cells, and their modulation can have non-negligible effects in the treatment of liver cancer. We discuss whether these microRNAs can be used for better clinical diagnosis and/or drug development. With the advent of novel technologies, fast, inexpensive, and non-invasive RNA-based biomarker research has become a new mainstream approach. However, the clinical application of microRNA-based markers has been limited by the high sequence similarity among them and the potential for off-target problems. Therefore, researchers particularly value microRNAs that are specific to or have special functions in liver cancer. These include miR-122, which is specifically expressed in the liver, and miR-34, which is necessary for the replication of the hepatitis C virus in liver cancer. Clinical treatment drugs have been developed based on miR-34 and miR-122 (MRX34 and Miravirsen, respectively), but their side effects have not yet been overcome. Future research is needed to address these weaknesses and establish a feasible microRNA-based treatment strategy for liver cancer.

Rational design for controlled release of Dicer-substrate siRNA harbored in phi29 pRNA-based nanoparticles

Small interfering RNA (siRNA) for silencing genes and treating disease has been a dream since ranking as a top Breakthrough of the Year in 2002 by Science. With the recent FDA approval of four siRNA-based drugs, the potential of RNA therapeutics to become the third milestone in pharmaceutical drug development has become a reality. However, the field of RNA interference (RNAi) therapeutics still faces challenges such as specificity in targeting, intracellular processing, and endosome trapping after targeted delivery. Dicer-substrate siRNAs included onto RNA nanoparticles may be able to overcome these challenges. Here, we show that pRNA-based nanoparticles can be designed to efficiently harbor the Dicer-substrate siRNAs in vitro and in vivo to the cytosol of tumor cells and release the siRNA. The structure optimization and chemical modification for controlled release of Dicer-substrate siRNAs in tumor cells were also evaluated through molecular beacon analysis. Studies on the length requirement of the overhanging siRNA revealed that at least 23 nucleotides at the dweller's arm were needed for dicer processing. The above sequence parameters and structure optimization were confirmed in recent studies demonstrating the release of functional Survivin siRNA from the pRNA-based nanoparticles for cancer inhibition in non-small-cell lung, breast, and prostate cancer animal models.

Thermostability, Tunability, and Tenacity of RNA as Rubbery Anionic Polymeric Materials in Nanotechnology and Nanomedicine-Specific Cancer Targeting with Undetectable Toxicity

RNA nanotechnology is the bottom-up self-assembly of nanometer-scale architectures, resembling LEGOs, composed mainly of RNA. The ideal building material should be (1) versatile and controllable in shape and stoichiometry, (2) spontaneously self-assemble, and (3) thermodynamically, chemically, and enzymatically stable with a long shelf life. RNA building blocks exhibit each of the above. RNA is a polynucleic acid, making it a polymer, and its negative-charge prevents nonspecific binding to negatively charged cell membranes. The thermostability makes it suitable for logic gates, resistive memory, sensor set-ups, and NEM devices. RNA can be designed and manipulated with a level of simplicity of DNA while displaying versatile structure and enzyme activity of proteins. RNA can fold into single-stranded loops or bulges to serve as mounting dovetails for intermolecular or domain interactions without external linking dowels. RNA nanoparticles display rubber- and amoeba-like properties and are stretchable and shrinkable through multiple repeats, leading to enhanced tumor targeting and fast renal excretion to reduce toxicities. It was predicted in 2014 that RNA would be the third milestone in pharmaceutical drug development. The recent approval of several RNA drugs and COVID-19 mRNA vaccines by FDA suggests that this milestone is being realized. Here, we review the unique properties of RNA nanotechnology, summarize its recent advancements, describe its distinct attributes inside or outside the body and discuss potential applications in nanotechnology, medicine, and material science.

Radiolabeled RNA Nanoparticles for Highly Specific Targeting and Efficient Tumor Accumulation with Favorable In Vivo Biodistribution

Therapeutic efficiency and toxicity are two of the three critical factors in molecular therapy and pharmaceutical drug development. Specific tumor targeting and rapid renal excretion contribute to improving efficiency and reducing toxicity. We recently found that RNA nanoparticles display rubber-like properties, enabling them to deliver therapeutics to cancer with high efficiency. Off-target RNA nanoparticles were rapidly cleared by renal excretion, resulting in nontoxicity. However, previous biodistribution studies relied mainly on fluorescent markers, which can cause interference from fluorophore quenching and autofluorescence. Thus, the quantification of biodistribution requires further scrutiny. In this study, radionuclide [³H] markers were used for quantitative pharmacokinetic (PK) studies to elucidate the favorable PK profile of RNA nanoparticles. Approximately 5% of [³H]-RNA nanoparticles accumulated in tumors, in contrast to the 0.7% tumor accumulation reported in the literature for other kinds of nanoparticles. The amount of [³H]-RNA nanoparticles accumulated in tumors was higher than that in the liver, heart, lung, spleen, and brain throughout the entire process after IV injection. [³H]-RNA nanoparticles rapidly reached the tumor vasculature within 30 min and remained in tumors for more than 2 days. Nontargeting [³H]-RNA nanoparticles were found in the urine 30 min after IV injection without degradation and processing, and more than 55% of the IV-injected radiolabeled RNA nanoparticles were cleared from the body within 12 h, while the other 45% includes the radiative counts that cannot be recovered due to whole-body distribution and blood dilution after intravenous injection. The high specificity of tumor targeting, fast renal excretion, and low organ accumulation illustrate the high therapeutic potential of RNA nanoparticles in cancer treatment as efficient cancer-targeting carriers with low toxicity and side effects.

Nucleic acid nanoparticles (NANPs) as molecular tools to direct desirable and avoid undesirable immunological effects

Nucleic acid nanoparticles (NANPs) represent a highly versatile molecular platform for the targeted delivery of various therapeutics. However, despite their promise, further clinical translation of this innovative technology can be hindered by immunological off-target effects. All human cells are equipped with an arsenal of receptors that recognize molecular patterns specific to foreign nucleic acids and understanding the rules that guide this recognition offer the key rationale for the development of therapeutic NANPs with tunable immune stimulation. Numerous recent studies have provided increasing evidence that in addition to NANPs' physicochemical properties and therapeutic effects, their interactions with cells of the immune system can be regulated through multiple independently programmable architectural parameters. The results further suggest that defined immunomodulation by NANPs can either support their immunoquiescent delivery or be used for conditional stimulation of beneficial immunological responses.

Non-Small-Cell Lung Cancer Regression by siRNA Delivered Through Exosomes That Display EGFR RNA Aptamer

Lung cancer is the second most common cancer in both men and women and is the leading cause of cancer death in the United States. The development of drug resistance to commonly used chemotherapeutics in non-small-cell lung cancer (NSCLC) poses significant health risks and there is a dire need to improve patient outcomes. In this study, we report the use of RNA nanotechnology to display ligand on exosome that was loaded with small interfering RNA (siRNA) for NSCLC regression in animal trials. Cholesterol was used to anchor the ligand targeting epidermal growth factor receptor on exosomes that were loaded with siRNA to silence the antiapoptotic factor survivin. The cytosolic delivery of siRNA overcame the problem of endosome trapping, leading to potent gene knockdown, chemotherapy sensitization, and tumor regression, thus achieving a favorable IC₅₀ of 20 nmol/kg siRNA encapsulated by exosome particles in the in vivo gene knockdown assessment.

Hydrogel-mediated delivery of microRNA-92a inhibitor polyplex nanoparticles induces localized angiogenesis

Localized stimulation of angiogenesis is an attractive strategy to improve the repair of ischemic or injured tissues. Several microRNAs (miRNAs) such as miRNA-92a (miR-92a) have been reported to negatively regulate angiogenesis in ischemic disease. To exploit the clinical potential of miR-92a inhibitors, safe and efficient delivery needs to be established. Here, we used deoxycholic acid-modified polyethylenimine polymeric conjugates (PEI-DA) to deliver a locked nucleic acid (LNA)-based miR-92a inhibitor (LNA-92a) in vitro and in vivo. The positively charged PEI-DA conjugates condense the negatively charged inhibitors into nano-sized polyplexes (135 ± 7.2 nm) with a positive net charge (34.2 ± 10.6 mV). Similar to the 25 kDa-branched PEI (bPEI₂₅) and Lipofectamine RNAiMAX, human umbilical vein endothelial cells (HUVECs) significantly internalized PEI-DA/LNA-92a polyplexes without any obvious cytotoxicity. Down-regulation of miR-92a following the polyplex-mediated delivery of LNA-92a led to a substantial increase in the integrin subunit alpha 5 (ITGA5), the sirtuin-1 (SIRT1) and Krüppel-like factors (KLF) KLF2/4 expression, formation of capillary-like structures by HUVECs, and migration rate of HUVECs in vitro. Furthermore, PEI-DA/LNA-92a resulted in significantly enhanced capillary density in a chicken chorioallantoic membrane (CAM) model. Localized angiogenesis was substantially induced in the subcutaneous tissues of mice by sustained release of PEI-DA/LNA-92a polyplexes from an in situ forming, biodegradable hydrogel based on clickable poly(ethylene glycol) (PEG) macromers. Our results indicate that PEI-DA conjugates efficiently deliver LNA-92a to improve angiogenesis. Localized delivery of RNA interference (RNAi)-based therapeutics via hydrogel-laden PEI-DA polyplex nanoparticles appears to be a safe and effective approach for different therapeutic targets.

Stoichiometry of multi-specific immune checkpoint RNA Abs for T cell activation and tumor inhibition using ultra-stable RNA nanoparticles

Immunotherapy has become a revolutionary subject in cancer therapy during the past few years. Immune checkpoint-targeting antibodies (Abs) could boost anticancer immune responses. However, certain protein-based immunotherapies revealed side effects and unfavorable biodistribution, so effective non-protein options with lower side effects are highly sought after. RNA's ability to form various three-dimensional configurations allows for the creation of a variety of ligands to bind different cell receptors. The rubber-like properties of RNA nanoparticles (NPs) allow for swift lodging to cancer vasculature with little accumulation in vital organs, resulting in a favorable pharmacokinetic/pharmacodynamic (PK/PD) profile and safe pharmacological parameters. Multi-specific drugs are expected to be the fourth wave of biopharmaceutical innovation. Herein, we report the development of multi-specific Ab-like RNA NPs carrying multiple ligands for immunotherapy. The stoichiometries and stereo conformations of the checkpoint-activating RNA NPs were optimized for T cell activation. When compared to mono- and bi-specific RNA NPs, the tri-specific Ab-like RNA NPs bound to the trimeric T cell receptor with the highest efficiency, showed the optimal T cell activation, and promoted the strongest anti-tumor function of immune cells. Animal trials demonstrated that the tri-specific RNA NPs inhibited cancer growth. This Ab-like RNA NP platform represents an alternative to protein Abs for tumor immunotherapy.

Use of Nanoparticles in Delivery of Nucleic Acids for Melanoma Treatment

Melanoma accounts for 4% of all skin cancer malignancies, with only 14% of diagnosed patients surviving for more than 5 years after diagnosis. Until now, there is no clear understanding of the detailed molecular contributors of melanoma pathogenesis. Accordingly, more research is needed to understand melanoma development and prognosis.All the treatment approaches that are currently applied have several significant limitations that prevent effective use in melanoma. One major limitation in the treatment of cancer is the acquisition of multidrug resistance (MDR). The MDR results in significant treatment failure and poor clinical outcomes in several cancers, including skin cancer. Treatment of melanoma is especially retarded by MDR. Despite the current advances in targeted and immune-mediated therapy, treatment arms of melanoma are severely limited and stand as a significant clinical challenge. Further, the poor pharmacokinetic profile of currently used chemotherapeutic agents is another reason for treatment failure. Therefore, more research is needed to develop novel drugs and carrier tools for more effective and targeted treatment.Nucleic acid therapy is based on nucleic acids or chemical compounds that are closely related, such as antisense oligonucleotides, aptamers, and small-interfering RNAs that are usually used in situations when a specific gene implicated in a disorder is deemed a therapeutically beneficial target for inhibition. However, the proper application for nucleic acid therapies is hampered by the development of an effective delivery system that can maintain their stability in the systemic circulation and enhance their uptake by the target cells. In this chapter, the prognosis of the different types of melanoma along with the currently used medications is highlighted, and the different types of nucleic acids along with the currently available nanoparticle systems for delivering these nucleic acids into melanoma cells are discussed. We also discuss recently conducted research on the use of different types of nanoparticles for nucleic acid delivery into melanoma cells and highlight the most significant outcomes.

Opportunities, Barriers, and a Strategy for Overcoming Translational Challenges to Therapeutic Nucleic Acid Nanotechnology

Recent clinical successes using therapeutic nucleic acids (TNAs) have accelerated the transition of nucleic acid nanotechnology toward therapeutic applications. Significant progress in the development, production, and characterization of nucleic acid nanomaterials and nucleic acid nanoparticles (NANPs), as well as abundant proof-of-concept data, are paving the way toward biomedical applications of these materials. This recent progress has catalyzed the development of new strategies for biosensing, imaging, drug delivery, and immunotherapies with previously unrecognized opportunities and identified some barriers that may impede the broader clinical translation of NANP technologies. A recent workshop sponsored by the Kavli Foundation and the Materials Research Society discussed the future directions and current challenges for the development of therapeutic nucleic acid nanotechnology. Herein, we communicate discussions on the opportunities, barriers, and strategies for realizing the clinical grand challenge of TNA nanotechnology, with a focus on ways to overcome barriers to advance NANPs to the clinic.

Self-assembly of four generations of RNA dendrimers for drug shielding with controllable layer-by-layer release

Chemical dendrimers have been shown to be a promising drug delivery platform due to their advantageous properties such as monodispersity, multivalency and branched structure. Taking advantage of self-assembly and its intrinsic negative charge, we used RNA as the building block for dendrimer construction to eliminate complex synthesis procedures and cationic charge-related toxicity. Oligo ribonucleotides produced by solid phase chemical synthesis allow the large-scale manufacture of homologous RNA dendrimers. Employing concepts from RNA nanotechnology enabled the controllable production of dendrimers with generations from G1, G2, G3, to G4 with layer-by-layer release capability. The conjugation of functional groups into individual RNA strands and the incorporation of functionalized RNA strands into the dendrimers at different sites have been reported. Anticancer drugs loaded into RNA dendrimers showed comparable cancer cell inhibition effect to free drugs. Encapsulation of cell binding ligands and hydrophobic drugs within the dendrimer significantly reduced the efficiency of cell binding and protein binding respectively, demonstrating the shielding effect of RNA dendrimers. The results imply a potential application of RNA dendrimer for delivery, shielding and controlled release of hydrophobic drugs in vivo.

Nanoparticles for Targeting of Prostate Cancer

Prostate cancer (PCa) is the leading cause of death by cancer in men. Because of the drastic decline in the survival rate of PCa patients with advanced/metastatic disease, early diagnosis of disease and therapy without toxic side effects is crucial. Chemotherapy is widely used to control the progression of PCa at the later stages; however, it is associated with off-target toxicities and severe adverse effects due to the lack of specificity. Delivery of therapeutic or diagnostic agents by using targeted nanoparticles is a promising strategy to enhance accuracy and sensitivity of diagnosis of PCa and to increase efficacy and specificity of therapeutic agents. Numerous efforts have been made in past decades to create nanoparticles with different architectural bases for specific delivery payloads to prostate tumors. Major PCa associated cell membrane protein markers identified as targets for such purposes include folate receptor, sigma receptors, transferrin receptor, gastrin-releasing peptide receptor, urokinase plasminogen activator receptor, and prostate specific membrane antigen. Among these markers, prostate specific membrane antigen has emerged as an extremely specific and sensitive targetable marker for designing targeted nanoparticle-based delivery systems for PCa. In this article, we review contemporary advances in design, specificity, and efficacy of nanoparticles functionalized against PCa. Whenever feasible, both diagnostic as well as therapeutic applications are discussed.

Promising RNA-based cancer gene therapy using extracellular vesicles for drug delivery

INTRODUCTION

RNA-based cancer gene therapy shows potential in cancer treatment. However, the safe and efficient transfer of therapeutic RNA to target cells has always been a challenge. The ideal drug delivery system should be effective with low immunogenicity and toxicity. Besides, a high specificity of drug delivery is necessary to improve efficacy and avoid the side effects associated with tumor heterogeneity. As endogenous RNA vehicles, extracellular vesicles (EVs) have shown their advantages and potential as drug delivery systems in gene therapy.

AREAS COVERED

We summarize the performance of EVs as a drug delivery system in RNA-based cancer gene therapy and discuss the advantages, limitations, and potentials of this translational medicine. In addition, we compare the characteristics and differences of current drug delivery systems and expound the principles of selecting a drug delivery system suitable for cancer gene therapy.

EXPERT OPINION

EVs are highly biocompatible membrane structures with low cytotoxicity which provide a new choice for drug delivery in RNA-based cancer gene therapy. The specificity of engineered EVs and artificial EV-mimetics can be improved through peptide or polymer decoration. However, apart from therapeutic RNA, EVs naturally carry many molecules. This may lead to unpredictable effects and thus should be applied with caution.

Nucleic acid nanotechnology for cancer treatment

Cancer is one of the most prevalent potentially lethal diseases. With the increase in the number of investigations into the uses of nanotechnology, many nucleic acid (NA)-based nanostructures such as small interfering RNA, microRNA, aptamers, and immune adjuvant NA have been applied to treat cancer. Here, we discuss studies on the applications of NA in cancer treatment, recent research trends, and the limitations and prospects of specific NA-mediated gene therapy and immunotherapy for cancer treatment. The NA structures used for cancer therapy consist only of NA or hybrids comprising organic or inorganic substances integrated with functional NA. We also discuss delivery vehicles for therapeutic NA and anti-cancer agents, and recent trends in NA-based gene therapy and immunotherapy against cancer.

A cationic amphiphilic co-polymer as a carrier of nucleic acid nanoparticles (Nanps) for controlled gene silencing, immunostimulation, and biodistribution

Programmable nucleic acid nanoparticles (NANPs) provide controlled coordination of therapeutic nucleic acids (TNAs) and other biological functionalities. Beyond multivalence, recent reports demonstrate that NANP technology can also elicit a specific immune response, adding another layer of customizability to this innovative approach. While the delivery of nucleic acids remains a challenge, new carriers are introduced and tested continuously. Polymeric platforms have proven to be efficient in shielding nucleic acid cargos from nuclease degradation while promoting their delivery and intracellular release. Here, we venture beyond the delivery of conventional TNAs and combine the stable cationic poly-(lactide-co-glycolide)-graft-polyethylenimine with functionalized NANPs. Furthermore, we compare several representative NANPs to assess how their overall structures influence their delivery with the same carrier. An extensive study of various formulations both in vitro and in vivo reveals differences in their immunostimulatory activity, gene silencing efficiency, and biodistribution, with fibrous NANPs advancing for TNA delivery.

RNA Nanotechnology to Solubilize Hydrophobic Antitumor Drug for Targeted Delivery

Small-molecule drugs are used extensively in clinics for cancer treatment; however, many antitumor chemical drugs dissolve poorly in aqueous solution. Their poor solubility and nonselective delivery in vivo often cause severe side effects. Here, the application of RNA nanotechnology to enhance the solubility of hydrophobic drugs, using camptothecin (CPT) for proof-of-concept in targeted delivery for cancer treatment is reported. Multiple CPT prodrug molecules are conjugated to RNA oligos via a click reaction, and the resulting CPT-RNA conjugates efficiently self-assemble into thermodynamically stable RNA three-way junction (3WJ) nanoparticles. The RNA 3WJ is covalently linked with seven hydrophobic CPT prodrug molecules through cleavable ester bonds and a folic acid ligand for specific tumor targeting while remaining soluble in aqueous solutions without detectable aggregation at therapeutic dose. This CPT-RNA nanoparticle exhibits efficient and specific cell binding and internalization, leading to cell apoptosis. Tumor growth is effectively inhibited by CPT-RNA nanoparticles; the targeted delivery, strengthened by tumor ligand, further enhances tumor suppression. Compared with the traditional formulation, solubilization of CPT in aqueous buffer using RNA nanoparticles as a carrier is found to be safe and efficacious, demonstrating that RNA nanoparticles are a promising platform for the solubilization and the delivery of hydrophobic antitumor drugs.

Tuning the size, shape and structure of RNA nanoparticles for favorable cancer targeting and immunostimulation

The past decade has shown exponential growth in the field of RNA nanotechnology. The rapid advances of using RNA nanoparticles for biomedical applications, especially targeted cancer therapy, suggest its potential as a new generation of drug. After the first milestone of small molecule drugs and the second milestone of antibody drugs, it was predicted that RNA drugs, either RNA itself or chemicals/ligands that target RNA, will be the third milestone in drug development. Thus, a comprehensive assessment of the current therapeutic RNA nanoparticles is urgently needed to meet the drug evaluation criteria. Specifically, the pharmacological and immunological profiles of RNA nanoparticles need to be systematically studied to provide insights in rational design of RNA-based therapeutics. By virtue of its programmability and biocompatibility, RNA molecules can be designed to construct sophisticated nanoparticles with versatile functions/applications and highly tunable physicochemical properties. This intrinsic characteristic allows the systemic study of the effects of various properties of RNA nanoparticles on their in vivo behaviors such as cancer targeting and immune responses. This review will focus on the recent progress of RNA nanoparticles in cancer targeting, and summarize the effects of common physicochemical properties such as size and shape on the RNA nanoparticles' biodistribution and immunostimulation profiles. This article is categorized under: Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Diagnostic Tools > in vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Folate-displaying exosome mediated cytosolic delivery of siRNA avoiding endosome trapping

Folate (FA) receptor is a cell surface glycoprotein overexpressed on many cancer cells. It is a high affinity ligand for cancer cell targeting. However, delivery of siRNA directly through folate receptor mediated endocytosis for gene silencing has not, if any, been successful in clinical trial. We have reported the application of RNA nanotechnology to construct FA-displaying exosomes for efficient cell targeting, siRNA delivery and cancer regression (Pi et.al Nature Nanotechnology, 2018:13, 82-89; Li et al., Scientific Report, 2018:8, 14,644). However, the mechanism underlying the efficient therapeutic behavior through folate/exosome complex remains elusive. Here we demonstrate that the efficient cancer suppression with the FA-displaying exosome was due to the receptor-mediated cytosol delivery of the siRNA payload without endosome trapping, as attested by fluorescence colocalization analysis, gene knockdown assay and animal tumor regression. It is expected that the high potency of FA-displaying exosome in cytosolic siRNA delivery will renew the concept and interest in using FA as cancer targeting ligand in human cancer therapy.

Small-Angle Scattering as a Structural Probe for Nucleic Acid Nanoparticles (NANPs) in a Dynamic Solution Environment

Nucleic acid-based technologies are an emerging research focus area for pharmacological and biological studies because they are biocompatible and can be designed to produce a variety of scaffolds at the nanometer scale. The use of nucleic acids (ribonucleic acid (RNA) and/or deoxyribonucleic acid (DNA)) as building materials in programming the assemblies and their further functionalization has recently established a new exciting field of RNA and DNA nanotechnology, which have both already produced a variety of different functional nanostructures and nanodevices. It is evident that the resultant architectures require detailed structural and functional characterization and that a variety of technical approaches must be employed to promote the development of the emerging fields. Small-angle X-ray and neutron scattering (SAS) are structural characterization techniques that are well placed to determine the conformation of nucleic acid nanoparticles (NANPs) under varying solution conditions, thus allowing for the optimization of their design. SAS experiments provide information on the overall shapes and particle dimensions of macromolecules and are ideal for following conformational changes of the molecular ensemble as it behaves in solution. In addition, the inherent differences in the neutron scattering of nucleic acids, lipids, and proteins, as well as the different neutron scattering properties of the isotopes of hydrogen, combined with the ability to uniformly label biological macromolecules with deuterium, allow one to characterize the conformations and relative dispositions of the individual components within an assembly of biomolecules. This article will review the application of SAS methods and provide a summary of their successful utilization in the emerging field of NANP technology to date, as well as share our vision on its use in complementing a broad suite of structural characterization tools with some simulated results that have never been shared before.

Delivery of Anti-miRNA for Triple-Negative Breast Cancer Therapy Using RNA Nanoparticles Targeting Stem Cell Marker CD133

Triple-negative breast cancer (TNBC) is an aggressive disease with a short median time from relapse to death. The increased aggressiveness, drug resistance, disease relapse, and metastasis are associated with the presence of stem cells within tumors. Several stem cell markers, such as CD24, CD44, CD133, ALDH1, and ABCG2, have been reported, but their roles in breast cancer tumorigenesis remain unclear. Herein, we apply RNA nanotechnology to deliver anti-microRNA (miRNA) for TNBC therapy. The thermodynamically and chemically stable three-way junction (3WJ) motif was utilized as the scaffold to carry an RNA aptamer binding to CD133 receptor and a locked nuclei acid (LNA) sequence for miRNA21 inhibition. Binding assays revealed the specific uptake of the nanoparticles to breast cancer stem cells (BCSCs) and TNBC cells. Functional assays showed that cancer cell migration was reduced, miR21 expression was inhibited, and downstream tumor suppressor PTEN and PDCD4 expressions were upregulated. In vitro and in vivo studies revealed that these therapeutic RNA nanoparticles did not induce cytokine secretion. Systemic injection of these RNA nanoparticles in animal trial demonstrated high specificity in TNBC tumor targeting and high efficacy for tumor growth inhibition. These results revealed the clinical translation potential of these RNA nanoparticles for TNBC therapy.

Smart-Responsive Nucleic Acid Nanoparticles (NANPs) with the Potential to Modulate Immune Behavior

Nucleic acids are programmable and biocompatible polymers that have beneficial uses in nanotechnology with broad applications in biosensing and therapeutics. In some cases, however, the development of the latter has been impeded by the unknown immunostimulatory properties of nucleic acid-based materials, as well as a lack of functional dynamicity due to stagnant structural design. Recent research advancements have explored these obstacles in tandem via the assembly of three-dimensional, planar, and fibrous cognate nucleic acid-based nanoparticles, called NANPs, for the conditional activation of embedded and otherwise quiescent functions. Furthermore, a library of the most representative NANPs was extensively analyzed in human peripheral blood mononuclear cells (PBMCs), and the links between the programmable architectural and physicochemical parameters of NANPs and their immunomodulatory properties have been established. This overview will cover the recent development of design principles that allow for fine-tuning of both the physicochemical and immunostimulatory properties of dynamic NANPs and discuss the potential impacts of these novel strategies.

RNA interference-based therapy and its delivery systems

RNA interference (RNAi) is considered a highly specific approach for gene silencing and holds tremendous potential for treatment of various pathologic conditions such as cardiovascular diseases, viral infections, and cancer. Although gene silencing approaches such as RNAi are widely used in preclinical models, the clinical application of RNAi is challenging primarily because of the difficulty in achieving successful systemic delivery. Effective delivery systems are essential to enable the full therapeutic potential of RNAi. An ideal nanocarrier not only addresses the challenges of delivering naked siRNA/miRNA, including its chemically unstable features, extracellular and intracellular barriers, and innate immune stimulation, but also offers "smart" targeted delivery. Over the past decade, great efforts have been undertaken to develop RNAi delivery systems that overcome these obstacles. This review presents an update on current progress in the therapeutic application of RNAi with a focus on cancer therapy and strategies for optimizing delivery systems, such as lipid-based nanoparticles.

Optimization of the Split-Spinach Aptamer for Monitoring Nanoparticle Assembly Involving Multiple Contiguous RNAs

The fact that structural RNA motifs can direct RNAs to fold and self-assemble into predictable pre-defined structures is an attractive quality and driving force for RNA’s use in nanotechnology. RNA’s recognized diversity concerning cellular and synthetically selected functionalities, however, help explain why it continues to draw attention for new nano-applications. Herein, we report the modification of a bifurcated reporter system based on the previously documented Spinach aptamer/DFHBI fluorophore pair that affords the ability to confirm the assembly of contiguous RNA strands within the context of the previously reported multi-stranded RNA nanoring. Exploration of the sequence space associated with the base pairs flanking the aptamer core demonstrate that fluorescent feedback can be optimized to minimize the fluorescence associated with partially-assembled RNA nanorings. Finally, we demonstrate that the aptamer-integrated nanoring is capable of assembling directly from transcribed DNA in one pot.

Molecular Engineering of Functional Nucleic Acid Nanomaterials toward In Vivo Applications

Recent advances in nanotechnology and engineering have generated many nanomaterials with unique physical and chemical properties. Over the past decade, numerous nanomaterials are introduced into many research areas, such as sensors for environmental monitoring, food safety, point-of-care diagnostics, and as transducers for solar energy transfer. Meanwhile, functional nucleic acids (FNAs), including nucleic acid enzymes, aptamers, and aptazymes, have attracted major attention from the biomedical community due to their unique target recognition and catalytic properties. Benefiting from the recent progress of molecular engineering strategies, the physicochemical properties of nanomaterials are endowed by the target recognition and catalytic activity of FNAs in the presence of a target analyte, resulting in numerous smart nanoprobes for diverse applications including intracellular imaging, drug delivery, in vivo imaging, and tumor therapy. This progress report focuses on the recent advances in designing and engineering FNA-based nanomaterials, highlighting the functional outcomes toward in vivo applications. The challenges and opportunities for the future translation of FNA-based nanomaterials into clinical applications are also discussed.