Arginine-engrafted biodegradable polymer for the systemic delivery of therapeutic siRNA

Non-viral vectors for RNA delivery

RNA-based therapy is a promising and potential strategy for disease treatment by introducing exogenous nucleic acids such as messenger RNA (mRNA), small interfering RNA (siRNA), microRNA (miRNA) or antisense oligonucleotides (ASO) to modulate gene expression in specific cells. It is exciting that mRNA encoding the spike protein of COVID-19 (coronavirus disease 2019) delivered by lipid nanoparticles (LNPs) exhibits the efficient protection of lungs infection against the virus. In this review, we introduce the biological barriers to RNA delivery in vivo and discuss recent advances in non-viral delivery systems, such as lipid-based nanoparticles, polymeric nanoparticles, N-acetylgalactosamine (GalNAc)-siRNA conjugate, and biomimetic nanovectors, which can protect RNAs against degradation by ribonucleases, accumulate in specific tissue, facilitate cell internalization, and allow for the controlled release of the encapsulated therapeutics.

Intranasal delivery of cancer-targeting doxorubicin-loaded PLGA nanoparticles arrests glioblastoma growth

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumour and treatment is very challenging. Despite the recent advances in drug delivery systems, various approaches that allow sufficient deposition of anti-cancer drugs within the brain remain unsuccessful due to limited drug delivery throughout the brain. In this study, we utilised an intranasal (IN) approach to allow delivery of anti-cancer drug, encapsulated in PLGA nanoparticles (NPs). PLGA NPs were modified with the RGD ligand to enable A_vβ₃ expressing tumour-specific delivery. IN delivery of RGD-conjugated-doxorubicin (DOX)-loaded-PLGA-nanoparticles (RGD-DOX-NP) showed cancer-specific delivery of NP and inhibition of brain tumour growth compared to the free-DOX or non-modified DOX-NP in the C6-implanted GBM model. Further, IN treatment with RGD-DOX-NP induces apoptosis in the tumour region without affecting normal brain cells. Our study provides therapeutic evidence to treat GBM using a non-invasive IN approach, which may further be translated to other brain-associated diseases.

Progress in arginine-based gene delivery systems

Arginine based gene delivery systems with enhanced membrane penetration and lower cytotoxicity greatly enrich the gene vectors library and outline a new development direction of gene delivery.

Thiolated polymers: Bioinspired polymers utilizing one of the most important bridging structures in nature

Thiolated polymers designated "thiomers" are obtained by covalent attachment of thiol functionalities on the polymeric backbone of polymers. In 1998 these polymers were first described as mucoadhesive and in situ gelling compounds forming disulfide bonds with cysteine-rich substructures of mucus glycoproteins and crosslinking through inter- and intrachain disulfide bond formation. In the following, it was shown that thiomers are able to form disulfides with keratins and membrane-associated proteins exhibiting also cysteine-rich substructures. Furthermore, permeation enhancing, enzyme inhibiting and efflux pump inhibiting properties were demonstrated. Because of these capabilities thiomers are promising tools for drug delivery guaranteeing a strongly prolonged residence time as well as sustained release on mucosal membranes. Apart from that, thiomers are used as drugs per se. In particular, for treatment of dry eye syndrome various thiolated polymers are in development and a first product has already reached the market. Within this review an overview about the thiomer-technology and its potential for different applications is provided discussing especially the outcome of studies in non-rodent animal models and that of numerous clinical trials. Moreover, an overview on product developments is given.

ATP-activated decrosslinking and charge-reversal vectors for siRNA delivery and cancer therapy

Stimuli-responsive polycations have been developed for improved nucleic acid transfection and enhanced therapeutic efficacy. The most reported mechanisms for controlled release of siRNA are based on polyelectrolyte exchange reactions in the cytoplasm and the degradation of polycations initiated by specific triggers. However, the degradation strategy has not always been sufficient due to unsatisfactory kinetics and binding of cationic fragments to siRNA, which limits the gene silencing effect. In this study, a new strategy that combines degradation and charge reversal is proposed.

Methods: We prepared a polycation (CrossPPA) by crosslinking of phenylboronic acid (PBA)-grafted 1.8k PEI with alginate. It was compared with 25k PEI, 1.8k PEI and 1.8k PEI-PBA on siRNA encapsulation, ATP-responsive behavior and mechanism, cytotoxicity, cell uptake, siRNA transfection, in vivo biodistribution and in vivo anti-tumor efficacy. The in vitro and in vivo experiments were performed on 4T1 murine breast cancer cells and 4T1 tumor model separately.

Results: The crosslinking strategy obviously improve the siRNA loading ability of 1.8k PEI. We validated that intracellular levels of ATP could trigger CrossPPA disassembly and charge reversal, which resulted in efficient and rapid siRNA release due to electrostatic repulsion. Besides, CrossPPA/siRNA showed strong cell uptake in 4T1 cells compared with 1.8k PEI/siRNA. Notably, the cytotoxicity of CrossPPA was pretty low, which was owing to its biodegradability. Furthermore, the crosslinked polyplexes significantly enhanced siRNA transfection and improved tumor accumulation. The high gene silencing ability of CrossPPA polyplex led to strong anti-tumor efficacy when using Bcl2-targeted siRNA.

Conclusion: These results indicated that the ATP-triggered disassembly and charge reversal strategy provided a new way for developing stimuli-responsive siRNA carriers and showed potential for nucleic acid delivery in the treatment of cancer.

Anti-HER2 functionalized graphene oxide as survivin-siRNA delivery carrier inhibits breast carcinoma growth in vitro and in vivo

BACKGROUND

The success of gene therapy is mostly dependent on the development of gene carrier. Graphene oxide (GO) possesses excellent aqueous solubility and biocompatibility, which is important for its biochemical and medical applications. Our previous work proved that GO can deliver siRNA into cells efficiently and downregulate the expression of desired protein.

METHODS

In this study, a novel delivery carrier, GO-R8/anti-HER2 (GRH), was developed by conjugating octaarginine (R8) and anti-HER2 antibody with GO as a tumor active-targeting vector for survivin-siRNA delivery.

RESULTS

GRH/survivin-siRNA formed nanoglobes of 195±10 nm in diameter. Real-time polymerase chain reaction analysis revealed that survivin messenger RNA expression showed a 42.4%±2.69% knockdown. The expression of survivin protein was downregulated to 50.86%±2.94% in enzyme-linked immunosorbent assay. In MTT tests, GRH exhibited no testable cytotoxicity. In vivo, GRH/survivin-siRNA showed gene silencing and inhibition of tumor growth.

CONCLUSION

The in vitro and in vivo results consistently demonstrated that GRH/survivin-siRNA has potential to be an efficient gene silencing carrier for siRNA delivery in cancer therapy.

Systemic siRNA delivery to tumors by cell-penetrating α-helical polypeptide-based metastable nanoparticles

Systemic, non-viral siRNA delivery for cancer treatment is mainly achieved via condensation by cationic materials (e.g., lipids and cationic polymers), which nevertheless, suffers from poor serum stability, non-specific tissue interaction, and unsatisfactory membrane activity against efficient in vivo gene knockdown. Here, we report the design of a metastable, cancer-targeting siRNA delivery system based on two functional polymers, PVBLG-8, a cationic, helical cell-penetrating polypeptide, and poly(l-glutamic acid) (PLG), an anionic random-coiled polypeptide. PVBLG-8 with rigid, linear structure showed weak siRNA condensation capability, and PLG with flexible chains was incorporated as a stabilizer which provided sufficient molecular entanglement with PVBLG-8 to encapsulate the siRNA within the polymeric network. The obtained PVBLG-8/siRNA/PLG nanoparticles (PSP NPs) with positive charges were sequentially coated with additional amount of PLG, which reversed the surface charge from positive to negative to yield the metastable PVBLG-8/siRNA/PLG@PLG (PSPP) NPs. The PSPP NPs featured desired serum stability during circulation to enhance tumor accumulation via the enhanced permeability and retention (EPR) effect. Upon acidification in the tumor extracellular microenvironment and intracellular endosomes, the partial protonation of PLG on PSPP NPs surface would lead to dissociation of PLG coating from NPs, exposure of the highly membrane-active PVBLG-8, and surface charge reversal from negative to positive, which subsequently promoted tumor penetration, selective cancer cell internalization, and efficient endolysosomal escape. When siRNA against epidermal growth factor receptor (EGFR) was encapsulated, the PSPP NPs showed excellent tumor penetration capability, tumor cell uptake level, EGFR silencing efficiency, and tumor growth inhibition efficacy in U-87 MG glioblastoma tumor spheroids in vitro and in xenograft tumor-bearing mice in vivo, outperforming the PSP NPs and several commercial reagents such as Lipofectamine 2000 and poly(l-lysine) (PLL). This study therefore demonstrates a facile and unique design approach of metastable and charge reversal NPs, which overcomes multiple biological barriers against systemic siRNA delivery toward anti-cancer treatment.

Reduction-sensitive polymeric nanomedicines: An emerging multifunctional platform for targeted cancer therapy

The development of smart delivery systems that are robust in circulation and quickly release drugs following selective internalization into target cancer cells is a key to precision cancer therapy. Interestingly, reduction-sensitive polymeric nanomedicines showing high plasma stability and triggered cytoplasmic drug release behavior have recently emerged as one of the most exciting platforms for targeted delivery of various anticancer drugs including small chemical drugs, proteins, and nucleic acids. In vivo studies in varying tumor models reveal that these reduction-sensitive multifunctional nanomedicines outperform the currently used clinical formulations and reduction-insensitive counterparts, bringing about not only significantly enhanced tumor selectivity, accumulation and inhibition efficacy but also markedly reduced systemic toxicity and improved therapeutic index. In this review, we will highlight the cutting-edge advancement with a focus on in vivo performances as well as future perspectives on reduction-sensitive polymeric nanomedicines for targeted cancer therapy.

Targeted drug delivery to melanoma

Melanoma derived from melanocytes is the most aggressive genre of skin cancer. Although the considerable advancement in the study of human cancer biology and drug discovery, most advanced melanoma patients are inevitably unable to be cured. With the emergence of nanotechnology, the use of nano-carriers is widely expected to alter the landscape of melanoma treatment. In this review, we will discuss melanoma biology, current treatment options, mechanisms behind drug resistance, and nano-based solutions for effective anti-cancer therapy, followed by challenges and perspectives in both pre-clinical and clinical settings.

Bioreducible Cross-Linked Hyaluronic Acid/Calcium Phosphate Hybrid Nanoparticles for Specific Delivery of siRNA in Melanoma Tumor Therapy

This study introduces a novel cross-linking strategy capable of successfully stabilizing CaP nanoparticles and stimuli-responsive small interfering RNA (siRNA) release. We synthesized a polysaccharide derivative thiolated hyaluronic acid (HA-SH), which was slightly modified but multifunctional and developed a smart redox-responsive delivery system. siRNA was efficaciously condensed by calcium phosphate (CaP) via electrostatic interaction to form a positively charged inner "core". Disulfide cross-linked HA (HA-ss-HA) was formed and played a role as an anionic outer "shell" to stabilize the CaP core. We demonstrated that the nanoparticles were stable both in the storage milieu and systemic circulation, thus overcoming the most serious disadvantage of CaP nanoparticles for gene delivery. Meanwhile, this smart system could selectively release siRNA into the cytosol by both a GSH-triggered disassembly and successful endosomal escape. Therefore, the hybrid delivery system achieved an 80% gene-silencing efficiency in vitro for both luciferase and Bcl2. Silencing of Bcl2 resulted in dramatic apoptosis of B16F10 cells. Besides, equipped with the tumor-targeting component HA, the nanoparticles significantly suppressed the growth of B16F10 xenograft tumor in mice. The anionic HA-ss-HA-equipped nanoparticles showed no apparent toxicity in vitro or in vivo, as well as showed a high transfection efficiency. Taken together, this redox-responsive, tumor-targeting smart anionic nanoparticle holds great promise for exploitation in functionalized siRNA delivery and tumor therapy.

Self-assembled PEG-b-PDPA-b-PGEM copolymer nanoparticles as protein antigen delivery vehicles to dendritic cells: preparation, characterization and cellular uptake

Antigen uptake by dendritic cells (DCs) is a key step for initiating antigen-specific T cell immunity. In the present study, novel synthetic polymeric nanoparticles were prepared as antigen delivery vehicles to improve the antigen uptake by DCs. Well-defined cationic and acid-responsive copolymers, monomethoxy poly(ethylene glycol)-block-poly(2-(diisopropyl amino) ethyl methacrylate)-block-poly(2-(guanidyl) ethyl methacrylate) (mPEG-b-PDPA-b-PGEM, PEDG) were synthesized by reversible addition-fragmentation chain transfer polymerization of 2-(diisopropylamino)ethyl methacrylate) and N-(tert-butoxycarbonyl) amino ethyl methacrylate monomers, followed by deprotection of tert-butyl protective groups and guanidinylation of obtained primary amines. 1H NMR, 13C NMR and GPC results indicated the successful synthesis of well-defined PEDG copolymers. PEDG copolymers could self-assemble into nanoparticles in aqueous solution, which were of cationic surface charges and showed acid-triggered disassembly contributed by PGEM and PDPA moieties, respectively. Significantly, PEDG nanoparticles could effectively condense with negatively charged model antigen ovalbumin (OVA) to form OVA/PEDG nanoparticle formulations with no influence on its secondary and tertiary structures demonstrating by far-UV circular dichroism and UV-vis spectra. In vitro antigen cellular uptake by bone marrow DCs (BMDCs) indicated using PEDG nanoparticles as antigen delivery vehicles could significantly improve the antigen uptake efficiency of OVA compared with free OVA or the commercialized Alum adjuvant. Moreover, as the surface cationic charges of OVA/PEDG nanoparticle formulations reduced, the uptake efficiency decreased correspondingly. Collectively, our work suggests that guanidinylated, cationic and acid-responsive PEDG nanoparticles represent a new kind of promising antigen delivery vehicle to DCs and hold great potential to serve as immunoadjuvants in the development of vaccines.

Gene-silencing effects of anti-survivin siRNA delivered by RGDV-functionalized nanodiamond carrier in the breast carcinoma cell line MCF-7

Nanodiamond (ND) is a renowned material in nonviral small interfering RNA (siRNA) carrier field due to its unique physical, chemical, and biological properties. In our previous work, it was proven that ND could deliver siRNA into cells efficiently and downregulate the expression of desired protein. However, synthesizing a high-efficient tumor-targeting carrier using ND is still a challenge. In this study, a novel carrier, NDCONH(CH₂)₂NH-VDGR, was synthesized for siRNA delivery, and its properties were characterized with methods including Fourier transform infrared spectrometry, transmission electron microscopy, scanning electron microscopy, gel retardation assay, differential scanning calorimetry, confocal microscopy, releasing test, real-time polymerase chain reaction (PCR) assay, enzyme-linked immunosorbent assay (ELISA), flow cytometry, cytotoxicity assay, and gene-silencing efficacy assay in vitro and in vivo. The mechanism of NDCONH(CH₂)₂NH-VDGR/survivin-siRNA-induced tumor apoptosis was evaluated via flow cytometer assay using Annexin V–fluorescein isothiocyanate/propidium iodide staining method. The NDCONH(CH₂)₂NH-VDGR/survivin-siRNA nanoparticle with 60–110 nm diameter and 35.65±3.90 mV zeta potential was prepared. For real-time PCR assay, the results showed that the expression of survivin mRNA was reduced to 46.77%±6.3%. The expression of survivin protein was downregulated to 48.49%±2.25%, as evaluated by ELISA assay. MTT assay showed that NDCONH(CH₂)₂NH-VDGR/survivin-siRNA had an inhibitory effect on MCF-7 cell proliferation. According to these results, the survivin-siRNA could be delivered, transported, and released stably, which benefits in increasing the gene-silencing effect. Therefore, as an siRNA carrier, NDCONH(CH₂)₂NH-VDGR was suggested to be used in siRNA delivery system and in cancer treatments.

Cationic cell-penetrating peptides as vehicles for siRNA delivery

RNA interference mediated gene silencing has tremendous applicability in fields ranging from basic biological research to clinical therapy. However, delivery of siRNA across the cell membrane into the cytoplasm, where the RNA silencing machinery is located, is a significant hurdle in most primary cells. Cell-penetrating peptides (CPPs), peptides that possess an intrinsic ability to translocate across cell membranes, have been explored as a means to achieve cellular delivery of siRNA. Approaches using CPPs by themselves or through incorporation into other siRNA delivery platforms have been investigated with the intent of improving cytoplasmic delivery. Here, we review the utilization of CPPs for siRNA delivery with a focus on strategies developed to enhance cellular uptake, endosomal escape and cytoplasmic localization of CPP/siRNA complexes.

Novel targets for paclitaxel nano formulations: Hopes and hypes in triple negative breast cancer

Triple negative breast cancer is defined as one of the utmost prevailing breast cancers worldwide, possessing an inadequate prognosis and treatment option limited to chemotherapy and radiotherapy, creating a challenge for researchers as far as developing a specific targeted therapy is concerned. The past research era has shown several promising outcomes for TNBC such as nano-formulations of the chemotherapeutic agents already used for the management of the malignant tumor. Taking a glance at paclitaxel nano formulations, it has been proven beneficial in several researches in the past decade; nevertheless its solubility is often a challenge to scientists in achieving success. We have henceforth discussed the basic heterogeneity of triple negative breast cancer along with the current management options as well as a brief outlook on pros and cons of paclitaxel, known as the most widely used chemotherapeutic agent for the treatment of the disease. We further analyzed the need of nanotechnology pertaining to the problems encountered with the current paclitaxel formulations available discussing the strategic progress in various nano-formulations till date taking into account the basic research strategies required in terms of solubility, permeability, physicochemical properties, active and passive targeting. A thorough review in recent advances in active targeting for TNBC was carried out whereby the various ligands which are at present finding its way into TNBC research such as hyaluronic acid, folic acid, transferrin, etc. were discussed. These ligands have specific receptor affinity to TNBC tumor cells hence can be beneficial for novel drug targeting approaches. Conversely, there are currently several novel strategies in the research pipeline whose targeting ligands have not yet been studied. Therefore, we reviewed upon the numerous novel receptor targets along with the respective nano-formulation aspects which have not yet been fully researched upon and could be exemplified as outstanding target strategies for TNBC which is currently an urgent requirement.

Optical Imaging and Gene Therapy with Neuroblastoma-Targeting Polymeric Nanoparticles for Potential Theranostic Applications

Recently, targeted delivery systems based on functionalized polymeric nanoparticles have attracted a great deal of attention in cancer diagnosis and therapy. Specifically, as neuroblastoma occurs in infancy and childhood, targeted delivery may be critical to reduce the side effects that can occur with conventional approaches, as well as to achieve precise diagnosis and efficient therapy. Thus, biocompatible poly(d,l-lactide-co-glycolide) (PLG) nanoparticles containing an imaging probe and therapeutic gene are prepared, followed by modification with rabies virus glycoprotein (RVG) peptide for neuroblastoma-targeting delivery. RVG peptide is a well-known neuronal targeting ligand and is chemically conjugated to PLG nanoparticles without changing their size or shape. RVG-modified nanoparticles are effective in specifically targeting neuroblastoma both in vitro and in vivo. RVG-modified nanoparticles loaded with a fluorescent probe are useful to detect the tumor site in a neuroblastoma-bearing mouse model, and those encapsulating a therapeutic gene cocktail (siMyc, siBcl-2, and siVEGF) significantly suppressed tumor growth in the mouse model. This approach to designing and tailoring of polymeric nanoparticles for targeted delivery may be useful in the development of multimodality systems for theranostic approaches.

Guanidinylated cationic nanoparticles as robust protein antigen delivery systems and adjuvants for promoting antigen-specific immune responses in vivo

Guanidinylated nanoparticles could act as effective immune adjuvants to elicit both potent antigen-specific cellular and humoral immune responses.

One-pot Synthesis of Functional Poly(amino ester sulfide)s and Utility in Delivering pDNA and siRNA

The development of efficacious carriers is an important long-standing challenge in gene therapy. In the past few decades, tremendous progress has been made toward non-viral vectors for gene delivery including cationic lipids and polymers. However, there continues to be a need for clinically translatable polymer-based delivery carriers because they offer tunable degradation profiles and functional groups, diverse structures/morphologies, and scalability in preparation. Herein, we developed a library of 144 degradable polymers with varying amine and hydrophobic content via a facile method that involves thiobutyrolactone aminolysis and consequent thiol-(meth)acrylate or acrylamide addition in one-pot. The polymer platform was evaluated for pDNA and siRNA delivery to HeLa cells in vitro. Hydrophobically modified 5S, 2E1, 6CY1, 5CY2, and 2M1 grafted HEMATL polymers are capable of delivering pDNA depending on the chemical composition and the size of the polyplexes. Hydrophobically modified 5S and 2B grafted HEMATL and 5S grafted ATL polymers exhibit capability for siRNA delivery that approaches the efficacy of commercially available transfection reagents. Due to tunable functionality and scalable preparation, this synthetic approach may have broad applicability in the design of delivery materials for gene therapy.

Synthesis and characterization of a PAMAM dendrimer nanocarrier functionalized by SRL peptide for targeted gene delivery to the brain

Blood-brain barrier inhibits most of drugs and genetic materials from reaching the brain. So, developing high efficiency carriers for gene and drug delivery to the brain, is the challenging area in pharmaceutical sciences. This investigation aimed to target DNA to brain using Serine-Arginine-Leucine (SRL) functionalized PAMAM dendrimers as a novel gene delivery system. The SRL peptide was linked on G4 PAMAM dendrimers using bifunctional PEG. DNA was then loaded in these functionalized nanoparticles and their physicochemical properties and cellular uptake/distribution evaluated by AFM, NMR, FTIR and fluorescence and confocal microscopy. Also, biodistribution and brain localization of nanoparticles were studied after IV injection of nanoparticles into rat tail. Unmodified nanoparticles were used as control in all evaluations. In vitro studies showed that SRL-modified nanoparticles have good transfection efficacy and low toxicity. Results also showed that SRL is a LRP ligand and SRL-modified nanoparticles internalized by clathrin/caveolin energy-dependent endocytosis to brain capillary endothelial cells. After intravenous administration, the SRL-modified nanoparticles were able to cross the blood-brain barrier and enter the brain parenchyma. Our result showed that, SRL-modified nanoparticles provide a safe and effective nanocarrier for brain gene delivery.

Design of a multicomponent peptide-woven nanocomplex for delivery of siRNA

We developed and tested a multicomponent peptide-woven siRNA nanocomplex (PwSN) comprising different peptides designed for efficient cellular targeting, endosomal escape, and release of siRNA. To enhance tumor-specific cellular uptake, we connected an interleukin-4 receptor-targeting peptide (I4R) to a nine-arginine peptide (9r), yielding I4R-9r. To facilitate endosomal escape, we blended endosomolytic peptides into the I4R-9r to form a multicomponent nanocomplex. Lastly, we modified 9r peptides by varying the number and positions of positive charges to obtain efficient release of siRNA from the nanocomplex in the cytosol. Using this step-wise approach for overcoming the biological challenges of siRNA delivery, we obtained an optimized PwSN with significant biological activity in vitro and in vivo. Interestingly, surface plasmon resonance analyses and three-dimensional peptide models demonstrated that our designed peptide adopted a unique structure that was correlated with faster complex disassembly and a better gene-silencing effect. These studies further elucidate the siRNA nanocomplex delivery pathway and demonstrate the applicability of our stepwise strategy to the design of siRNA carriers capable of overcoming multiple challenges and achieving efficient delivery.

Recent advances in targeted nanoparticles drug delivery to melanoma

Melanoma is one of the most aggressive skin cancers, notorious for its high multidrug resistance and low survival rate. Conventional therapies (e.g., dacarbazine, interferon-alpha-2b and interleukin-2) are limited by low response rate and demonstrate no overall survival benefit. Novel targeted therapies (e.g., vemurafenib, dabrafenib and trametinib) have higher initial response rate and clear impact on the overall survival, but relapse usually occurs within 6 to 9 months. Although immunotherapy (e.g., ipilimumab, pembrolizumab and nivolumab) can achieve long-term and durable response, rate of adverse events is extremely high. With the development of nanotechnology, the applications of nanocarriers are widely expected to change the landscape of melanoma therapy for foreseeable future. In this review, we will relate recent advances in the application of multifunctional nanocarriers for targeted drug delivery to melanoma, in melanoma nanotheranostics and combination therapy, and nanopharmaceutical associated melanoma clinical trials, followed by challenges and perspectives. From the clinical editor: The team of authors describes the current treatment regimes of malignant melanoma emphasizing the importance of achieving a better efficacy and the need to develop a better understanding of melanoma tumorigenesis.

Attachment of cell-binding ligands to arginine-rich cell-penetrating peptides enables cytosolic translocation of complexed siRNA

Cell-penetrating peptides (CPPs), such as nona-arginine (9R), poorly translocate siRNA into cells. Our studies demonstrate that attaching 9R to ligands that bind cell surface receptors quantitatively increases siRNA uptake and importantly, allows functional delivery of complexed siRNA. The mechanism involved accumulation of ligand-9R:siRNA microparticles on the cell membrane, which induced transient membrane inversion at the site of ligand-9R binding and rapid siRNA translocation into the cytoplasm. siRNA release also occurred late after endocytosis when the ligand was attached to the L isoform of 9R, but not the protease-resistant 9DR, prolonging mRNA knockdown. This critically depended on endosomal proteolytic activity, implying that partial CPP degradation is required for endosome-to-cytosol translocation. The data demonstrate that ligand attachment renders simple polycationic CPPs effective for siRNA delivery by restoring their intrinsic property of translocation.

Next generation delivery system for proteins and genes of therapeutic purpose: why and how?

Proteins and genes of therapeutic interests in conjunction with different delivery systems are growing towards new heights. "Next generation delivery systems" may provide more efficient platform for delivery of proteins and genes. In the present review, snapshots about the benefits of proteins or gene therapy, general procedures for therapeutic protein or gene delivery system, and different next generation delivery system such as liposome, PEGylation, HESylation, and nanoparticle based delivery have been depicted with their detailed explanation.

Drug delivery nanoparticles in skin cancers

Nanotechnology involves the engineering of functional systems at nanoscale, thus being attractive for disciplines ranging from materials science to biomedicine. One of the most active research areas of the nanotechnology is nanomedicine, which applies nanotechnology to highly specific medical interventions for prevention, diagnosis, and treatment of diseases, including cancer disease. Over the past two decades, the rapid developments in nanotechnology have allowed the incorporation of multiple therapeutic, sensing, and targeting agents into nanoparticles, for detection, prevention, and treatment of cancer diseases. Nanoparticles offer many advantages as drug carrier systems since they can improve the solubility of poorly water-soluble drugs, modify pharmacokinetics, increase drug half-life by reducing immunogenicity, improve bioavailability, and diminish drug metabolism. They can also enable a tunable release of therapeutic compounds and the simultaneous delivery of two or more drugs for combination therapy. In this review, we discuss the recent advances in the use of different types of nanoparticles for systemic and topical drug delivery in the treatment of skin cancer. In particular, the progress in the treatment with nanocarriers of basal cell carcinoma, squamous cell carcinoma, and melanoma has been reported.

Recent In Vivo Evidences of Particle-Based Delivery of Small-Interfering RNA (siRNA) into Solid Tumors

Small-interfering RNA (siRNA) is both a powerful tool in research and a promising therapeutic platform to modulate expression of disease-related genes. Malignant tumors are attractive disease targets for nucleic acid-based therapies. siRNA directed against oncogenes, and genes driving metastases or angiogenesis have been evaluated in animal models and in some cases, in humans. The outcomes of these studies indicate that drug delivery is a significant limiting factor. This review provides perspectives on in vivo validated nanoparticle-based siRNA delivery systems. Results of recent advances in liposomes and polymeric and inorganic formulations illustrate the need for mutually optimized attributes for performance in systemic circulation, tumor interstitial space, plasma membrane, and endosomes. Physiochemical properties conducive to efficient siRNA delivery are summarized and directions for future research are discussed.

Bioreducible polymers for therapeutic gene delivery

Most currently available cationic polymers have significant acute toxicity concerns such as cellular toxicity, aggregation of erythrocytes, and entrapment in the lung capillary bed, largely due to their poor biocompatibility and non-degradability under physiological conditions. To develop more intelligent polymers, disulfide bonds are introduced in the design of biodegradable polymers. Herein, the sustained innovations of biomimetic nano-sized constructs with bioreducible poly(disulfide amine)s demonstrate a viable clinical tool for the treatment of cardiovascular disease, anemia, diabetes, and cancer.

Effect of biodegradability on CXCR4 antagonism, transfection efficacy and antimetastatic activity of polymeric Plerixafor

Chemokine receptor CXCR4 and its sole ligand SDF-1 are key players in regulating cancer cell invasion and metastasis. Plerixafor (AMD3100) is a small-molecule CXCR4 antagonist that prevents binding of SDF-1 to CXCR4 and has potential in prevention of cancer metastasis. This study investigates the influence of biodegradability of a recently reported polymeric Plerixafor (PAMD) on CXCR4 antagonism, antimetastatic activity, and transfection efficacy of PAMD polyplexes with plasmid DNA. We show that PAMD exhibits CXCR4 antagonism and inhibition of cancer cell invasion in vitro regardless of its biodegradability. Biodegradable PAMD showed considerably enhanced transfection efficiency and decreased cytotoxicity when compared with the non-degradable PAMD. Despite similar CXCR4 antagonism in vitro, only biodegradable PAMD displayed antimetastatic activity in experimental lung metastasis model in vivo.

Cationic bovine serum albumin based self-assembled nanoparticles as siRNA delivery vector for treating lung metastatic cancer

It is generally believed that intravenous application of cationic vectors is limited by the binding of abundant negatively charged serum components, which may cause rapid clearance of the therapeutic agent from the blood stream. However, previous studies show that systemic delivery of cationic gene vectors mediates specific and efficient transfection within the lung, mainly as a result of interaction of the vectors with serum proteins. Based on these findings, a novel and charge-density-controllable siRNA delivery system is developed to treat lung metastatic cancer by using cationic bovine serum albumin (CBSA) as the gene vector. By surface modification of BSA, CBSA with different isoelectric points (pI) is synthesized and the optimal cationization degree of CBSA is determined by considering the siRNA binding and delivery ability, as well as toxicity. The CBSA can form stable nanosized particles with siRNA and protect siRNA from degradation. CBSA also shows excellent abilities to intracellularly deliver siRNA and mediate significant accumulation in the lung. When Bcl2-specific siRNA is introduced to this system, CBSA/siRNA nanoparticles exhibit an efficient gene-silencing effect that induces notable cancer cell apoptosis and subsequently inhibits the tumor growth in a B16 lung metastasis model. These results indicate that CBSA-based self-assembled nanoparticles can be a promising strategy for a siRNA delivery system for lung targeting and metastatic cancer therapy.

Inhibition of lymphangiogenesis of endothelial progenitor cells with VEGFR-3 siRNA delivered with PEI-alginate nanoparticles

Lymphangiogenesis is implicated in lymphatic metastasis of tumor cells. Recently, growing evidences show that endothelial progenitor cells (EPCs) are involved in lymphangiogenesis. This study has investigated effects of VEGF-C/VEGFR-3 (vascular endothelial growth factor receptor-3) signaling pathway on EPC differentiation and effectiveness of inhibiting lymphatic formation of EPCs with VEGFR-3 siRNA delivered in PEI (polyethylenimine)-alginate nanoparticles. CD34⁺VEGFR-3⁺ EPCs were sorted from mononuclear cells of human cord blood. Under induction with VEGF-C, the cells differentiated toward lymphatic endothelial cells. The nanoparticles were formulated with 25 kDa branched PEI and alginate. The size and surface charge of PEI-alginate nanoparticles loading VEGFR-3 siRNA (N/P = 16) are 139.1 nm and 7.56 mV respectively. VEGFR-3 siRNA specifically inhibited expression of VEGFR-3 mRNA in the cells. After treatment with PEI-alginate/siRNA nanocomplexes, EPCs could not differentiate into lymphatic endothelial cells, and proliferation, migration and lymphatic formation of EPC-derived cells were suppressed significantly. These results demonstrate that VEGFR-3 signaling plays an important role in differentiation of CD34⁺VEGFR-3⁺ EPCs. VEGFR-3 siRNA delivered with PEI-alginate nanoparticles can effectively inhibit differentiation and lymphangiogenesis of EPCs. Inhibiting VEGFR-3 signaling with siRNA/nanocomplexes would be a potential therapy for suppression of tumor lymphangiogenesis and lymphatic metastasis.

Arginine-grafted biodegradable polymer: a versatile transfection reagent for both DNA and siRNA

Effective delivery of DNA or siRNA into primary cells demands an efficient delivery system. However, the significant differences in physical and molecular characteristics of the two molecules generally necessitate distinct delivery systems or considerable differences in carrier formulation protocols for effective transfection. Arginine-grafted bioreducible poly (disulfide amine) (ABP) is a redox-sensitive, bioreducible, positively charged polymer which complexes with siRNA and DNA via charge interactions to form nanoplexes. ABP effectively mediates cytoplasmic delivery of both DNA and siRNA into multiple cell types, including primary cells like myoblast, human umbilical vein endothelial cells (HUVECs), and primary rat aorta vascular smooth muscle cells (SMCs) eliciting functional activity. In this chapter, we provide the detailed protocols for the synthesis of ABP as well as transfection of both siRNA and DNA using ABP.

Self-crosslinked human serum albumin nanocarriers for systemic delivery of polymerized siRNA to tumors

The safe and effective systemic delivery of siRNA is a prerequisite for the successful development of siRNA-based cancer therapeutics. For the enhanced delivery of siRNA, cationic lipids and polymers have been widely used as siRNA carriers to form electrolyte complexes with anionic siRNA. However, the considerable toxicity of strong cationic-charged molecules hampers their clinical use. In this study, we utilized human serum albumin (HSA), which is the most abundant of the plasma proteins, as a siRNA carrier for systemic tumor-targeted siRNA delivery. Both HSA and siRNA molecules were thiol-introduced to improve the binding affinity for each other. The resulting thiolated HSA (tHSA) and polymerized siRNA (psi) formed stable nanosized complexes (psi-tHSAs) by chemical crosslinking and self-crosslinking. After internalization, the psi-tHSAs showed target gene silencing activity in vitro comparable to conventional Lipofectamine™-siRNA complexes, without remarkable cytotoxicity. After intravenous injection in tumor-bearing mice, psi-tHSAs accumulated specifically at the tumor sites, leading to efficient gene silencing in the tumors in a sequential manner. The therapeutic VEGF siRNA was loaded into psi-tHSAs, which significantly inhibited tumor-related angiogenesis in PC-3 tumor xenografts and resulted in retarding the growth of PC-3 tumors. The results showed that self-crosslinked psi-tHSA nanocarriers might provide a promising approach for the systemic siRNA therapy of various human cancers.

Applications of nanotechnology for melanoma treatment, diagnosis, and theranostics

Melanoma is the most aggressive type of skin cancer and has very high rates of mortality. An early stage melanoma can be surgically removed, with a survival rate of 99%. However, metastasized melanoma is difficult to cure. The 5-year survival rates for patients with metastasized melanoma are still below 20%. Metastasized melanoma is currently treated by chemotherapy, targeted therapy, immunotherapy and radiotherapy. The outcome of most of the current therapies is far from optimistic. Although melanoma patients with a mutation in the oncogene v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) have an initially higher positive response rate to targeted therapy, the majority develop acquired drug resistance after 6 months of the therapy. To increase treatment efficacy, early diagnosis, more potent pharmacological agents, and more effective delivery systems are urgently needed. Nanotechnology has been extensively studied for melanoma treatment and diagnosis, to decrease drug resistance, increase therapeutic efficacy, and reduce side effects. In this review, we summarize the recent progress on the development of various nanoparticles for melanoma treatment and diagnosis. Several common nanoparticles, including liposome, polymersomes, dendrimers, carbon-based nanoparticles, and human albumin, have been used to deliver chemotherapeutic agents, and small interfering ribonucleic acids (siRNAs) against signaling molecules have also been tested for the treatment of melanoma. Indeed, several nanoparticle-delivered drugs have been approved by the US Food and Drug Administration and are currently in clinical trials. The application of nanoparticles could produce side effects, which will need to be reduced so that nanoparticle-delivered drugs can be safely applied in the clinical setting.

Biofunctionalized nanoparticles with pH-responsive and cell penetrating blocks for gene delivery

Bridging the gap between nanoparticulate delivery systems and translational gene therapy is a long sought after requirement in nanomedicine-based applications. However, recent developments regarding nanoparticle functionalization have brought forward the ability to synthesize materials with biofunctional moieties that mimic the evolved features of viral particles. Herein we report the versatile conjugation of both cell penetrating arginine and pH-responsive histidine moieties into the chitosan polymeric backbone, to improve the physicochemical characteristics of the native material. Amino acid coupling was confirmed by 2D TOCSY NMR and Fourier transform infrared spectroscopy. The synthesized chitosan-histidine-arginine (CH-H-R) polymer complexed plasmid DNA biopharmaceuticals, and spontaneously assembled into stable 105 nm nanoparticles with spherical morphology and positive surface charge. The functionalized delivery systems were efficiently internalized into the intracellular compartment, and exhibited remarkably higher transfection efficiency than unmodified chitosan without causing any cytotoxic effect. Additional findings regarding intracellular trafficking events reveal their preferential escape from degradative lysosomal pathways and nuclear localization. Overall, this assembly of nanocarriers with bioinspired moieties provides the foundations for the design of efficient and customizable materials for cancer gene therapy.

NIR light controlled photorelease of siRNA and its targeted intracellular delivery based on upconversion nanoparticles

The most notable role of small interfering RNA (siRNA) is in RNA interference (RNAi) and post-transcriptional gene silencing, which leads to a surge of interest in RNAi for both biomedical research and therapeutic applications. However, "naked" siRNA cannot cross cellular membranes freely because of highly negative charges which limits its utility for gene therapy. In this work, a system of near-infrared (NIR) light-induced siRNA release from silica coated upconversion nanoparticles (Si-UCNPs) is presented. These Si-UCNPs were functionalized with cationic photocaged linkers through covalent bonding, which could effectively adsorb anionic siRNA through electrostatic attractions and were easily internalized by living cells. Upon NIR light irradiation, the photocaged linker on the Si-UCNPs surface could be cleaved by the upconverted UV light and thus initiated the intracellular release of the siRNA. The in vitro agarose gel electrophoresis and intracellular imaging results indicated that the Si-UCNPs-based gene carrier system allowed effective siRNA delivery and the applications of NIR light instead of direct high energy UV irradiation may greatly guarantee less cell damage.

Cyclam-based polymeric copper chelators for gene delivery and potential PET imaging

A series of reducible polycationic copper chelators (RPCs) based on 1,4,8,11-tetraazacyclotetradecane (cyclam) were synthesized by Michael addition. Molecular weight of the polycations was controlled by reaction stoichiometry and reaction conditions, resulting in polymers with molecular weights ranging from 4400 to 13 800. The cyclam moieties in the polycations retained their ability to form complexes with Cu(II). The presence of disulfide bonds in the polycations resulted in substantially lower cytotoxicity than control 25 kDa poly(ethyleneimine). RPC as well as their complexes with Cu(II) exhibited high transfection activity in vitro. The reported polycationic Cu(II) chelates represent promising nucleic acid delivery vectors with potential for future theranostic applications.

Nanoparticles-mediated drug delivery approaches for cancer targeting: a review

Cancer has become the leading cause of death among different populations of the world. The treatment is limited to chemotherapy, radiation, and surgery. Selective targeting to the tumor cells is possible by nanoparticles-based drug delivery system. It maximizes the drug concentration at the desired target and protects the surrounding healthy tissues at the same time. To improve the targeting potential of the anticancer drugs, nanoparticles were optimized for the size and surface characteristics to enhance their circulation time and targeting efficiency. Passive targeting involves surface modification with polyethylene glycol to avoid its elimination by natural body defense mechanism. Active targeting involves chemical interaction with certain antigen, receptors, and genes which are over expressed during progression of disease. In addition, the article highlights recent developments in "smart"-stimulus-responsive-drug carriers designed to enhance the localization and efficacy of therapeutic payloads as compared with free drug. Enhanced targeting potential, imaging, and controlled release of drugs or therapeutic molecules could be possible through multi-functional nanocarrier. Such multi-faceted, versatile nanocarriers and drug delivery systems promise a substantial increase in the efficacy of diagnostic and therapeutic applications in pharmaceutical sciences.