siRNA Delivery by Stimuli-Sensitive Nanocarriers

Inorganic nanoparticle-based advanced cancer therapies: promising combination strategies

Inorganic nanoparticles for drug delivery in cancer treatment offer many potential advantages because they can maximize therapeutic effect through targeting ligands while minimizing off-target side-effects through drug adsorption and infiltration. Although inorganic nanoparticles were introduced as drug carriers, they have emerged as having the capacity for combined therapeutic capabilities, including anticancer effects through cytotoxicity, suppression of oncogenes and cancer cell signaling pathway inhibition. The most promising advanced strategies for cancer therapy are as synergistic platforms for RNA interference (siRNA, miRNA, shRNA) and as synergistic drug delivery agents for the inhibition of cancer cell signaling pathways. The present work summarizes relevant current work, the promise of which is suggested by a projected compound annual growth rate of ∼20% for drug delivery alone.

The Future of Tissue-Targeted Lipid Nanoparticle-Mediated Nucleic Acid Delivery

The earliest example of in vivo expression of exogenous mRNA is by direct intramuscular injection in mice without the aid of a delivery vehicle. The current state of the art for therapeutic nucleic acid delivery is lipid nanoparticles (LNP), which are composed of cholesterol, a helper lipid, a PEGylated lipid and an ionizable amine-containing lipid. The liver is the primary organ of LNP accumulation following intravenous administration and is also observed to varying degrees following intramuscular and subcutaneous routes. Delivery of nucleic acid to hepatocytes by LNP has therapeutic potential, but there are many disease indications that would benefit from non-hepatic LNP tissue and cell population targeting, such as cancer, and neurological, cardiovascular and infectious diseases. This review will concentrate on the current efforts to develop the next generation of tissue-targeted LNP constructs for therapeutic nucleic acids.

Macrophage membrane- and cRGD-functionalized thermosensitive liposomes combined with CPP to realize precise siRNA delivery into tumor cells

Despite the success of small interfering RNAs (siRNAs) in clinical settings, their fast clearance and poor delivery efficiency to target cells still hinder their therapeutic effect. Herein, a new treatment system was constructed by combining thermosensitive liposomes with the macrophage membrane, tumor-targeting cyclic Arg-Gly-Asp peptide, a cell-penetrating peptide, and thermotherapy. The constructed system was found to be thermosensitive and stable; the proteins were inherited from the macrophage membrane. This new system combined with thermotherapy displayed the least uptake by macrophages, the greatest uptake by HepG2 cells, the most obvious HepG2 cell apoptosis, and the strongest inhibition of Bcl-2 mRNA and Bcl-2 protein in HepG2 cells. Moreover, 24 h after system administration in tumor-bearing mice, the most prominent distribution of siRNA was observed in tumors, while almost no siRNA was found in other organs. The strongest inhibition of Bcl-2 mRNA, Bcl-2 protein, and tumors was found in mice that had received the proposed system. In summary, when using the constructed system both in vitro and in mice, less uptake by the reticuloendothelial system, greater accumulation in tumor cells, and improved therapeutic efficacy were observed. Therefore, this new system can deliver siRNA selectively and efficiently, and it is a promising therapeutic candidate for precise tumor-targeted therapy.

Photoactivation of sulfonated polyplexes enables localized gene silencing by DsiRNA in breast cancer cells

Translation potential of RNA interference nanotherapeutics remains challenging due to in vivo off-target effects and poor endosomal escape. Here, we developed novel polyplexes for controlled intracellular delivery of dicer substrate siRNA, using a light activation approach. Sulfonated polyethylenimines covalently linked to pyropheophorbide-α for photoactivation and bearing modified amines (sulfo-pyro-PEI) for regulated endosomal escape were investigated. Gene knock-down by the polymer-complexed DsiRNA duplexes (siRNA-NPs) was monitored in breast cancer cells. Surprisingly, sulfo-pyro-PEI/siRNA-NPs failed to downregulate the PLK1 or eGFP proteins. However, photoactivation of these cell associated-polyplexes with a 661-nm laser clearly restored knock-down of both proteins. In contrast, protein down-regulation by non-sulfonated pyro-PEI/siRNA-NPs occurred without any laser treatments, indicating cytoplasmic disposition of DsiRNA followed a common intracellular release mechanism. Therefore, sulfonated pyro-PEI holds potential as a unique trap and release light-controlled delivery platform for on-demand gene silencing bearing minimal off target effects.

Laser enhancement of cancer cell destruction by photothermal therapy conjugated glutathione (GSH)-coated small-sized gold nanoparticles

The current study presents the employment of glutathione (GSH)-modified small-sized gold nanoparticles (AuNPs) ~ 3 nm in photothermal therapy (PTT), to evaluate the targeting and the toxic effect of cancer rather than normal cells. GSH is pH-sensitive surfaces that exhibit a fast response to the variation in pH conditions between normal (~ 7.4) and cancer cells (6-6.5). Results showed a considerable toxic impact via GSH-AuNP accumulation in cancer cells by both green and NIR laser irradiation. A proportional relation of cellular death to AuNP concentration, exposure time, and light-to-heat conversion efficiency has been demonstrated. The small-sized GSH-AuNPs represent promising agents for developing the safety issues of photothermal cancer treatment by the selective targeting of cancer rather than normal cells, reducing the NP toxicity by their size overlapping with the renal clearance barrier of kidney filtration (~ 5.5 nm), and promoting the photothermal performance in the NIR region, in which light penetration into deep cancer regions is more interested.

Integration of Polylactide into Polyethylenimine Facilitates the Safe and Effective Intracellular siRNA Delivery

Polyethylenimine (PEI) is a gold standard polymer with excellent transfection efficacy, yet its severe toxicity and nondegradability hinders its therapeutic application as a gene delivery vector. To tackle this problem, herein we incorporated the biodegradable polylactide (PLA) into the branched PEI by synthesizing a PEI-PLA copolymer via a facile synthetic route. PLA modification significantly improved the cytocompatibility of PEI, PEI-PLA copolymer showed much higher cell viability than PEI as verified in three different human cancer cell lines (HCT116, HepG2 and SKOV3). Interestingly, the PEI-PLA copolymer could effectively bind siRNA targeting PKM2, and the obtained polyplex displayed much higher stability in serum than naked siRNA as determined by agarose gel electrophoresis. Moreover, cellular uptake study demonstrated that PEI-PLA could efficiently deliver the Cy5-labled siRNA into the three tested cancer cell lines, and the transfection efficiency is equivalent to the commercial Lipofectamine^® 2000. Finally, it is noteworthy that the polyplex is comparable to Lipo2000 in down-regulating the expression of PKM2 at both mRNA and protein level as measured by q-PCR and western blotting, respectively. Overall, the PEI-PLA copolymer developed in this study has the potential to be developed as a versatile carrier for safe and effective delivery of other nucleic acid-based agents.

Bioinspired Smart Nanosystems in Advanced Therapeutic Applications

BACKGROUND

Nanoparticle technologies used for human administration must be designed to interact with a living host environment. The idea about bioinspired smart drug delivery carriers includes the development of biocompatible nanomaterials which can be further loaded with the drug for specific targeted drug delivery applications.

OBJECTIVE

Biosmart nanosystems are used for several applications in the delivery of drugs and pharmaceuticals for their therapeutic applications like biological markers, diagnostic purposes such as imaging applications and also for gene therapy. Thus, the bioinspired nanocarriers are capable of carrying biologically active molecules to the target sites. This bioinspired nanosystem constitutes of lipids, polymers and biomaterials which utilizes various responsive sensors for targeted drug delivery systems. However, external conditions such as heat, light, magnetic or electric field and ultrasounds, along with temperature, altered pH and ionic strength can affect the bioinspired smart nanosystem for drug delivery.

CONCLUSION

The present review focuses on challenges for the development of bioinspired smart nanocarriers for the management of various disorders.

siRNA intervention inhibiting viral replication and delivery strategies for treating herpes simplex viral infection

The effective treatment of herpes simplex virus (HSV) infections generally involves the use of antiviral nucleoside drugs, but with increasing reports of antiviral resistance, the use of these drugs is challenged. Hence, a need arises to explore alternate treatment options. In this review we have discussed various targets that have been explored to control the HSV replication using siRNA therapeutics. We have also discussed the advantages of targeting a less explored UL10 gene to develop an alternate therapeutic intervention. Gene silencing can induce an inhibitory activity to virus spread and infection. The capacity and suitability of UL10 gene as siRNA induced silencing target in eliciting the desired antiviral effect in patients is identified and particularly discussed. The major challenge associated with the siRNA therapeutics is their delivery. The various viable delivery options, that are being explored in the recent times is summarized and different delivery pathways and strategies are reviewed as a part of the study.

Advances on non-invasive physically triggered nucleic acid delivery from nanocarriers

Nucleic acids (NAs) have been considered as promising therapeutic agents for various types of diseases. However, their clinical applications still face many limitations due to their charge, high molecular weight, instability in biological environment and low levels of transfection. To overcome these drawbacks, therapeutic NAs should be carried in a stable nanocarrier, which can be viral or non-viral vectors, and released at specific target site. Various controllable gene release strategies are currently being evaluated with interesting results. Endogenous stimuli-responsive systems, for example pH-, redox reaction-, enzymatic-triggered approaches have been widely studied based on the physiological differences between pathological and normal tissues. Meanwhile, exogenous triggered release strategies require the use of externally non-invasive physical triggering signals such as light, heat, magnetic field and ultrasound. Compared to internal triggered strategies, external triggered gene release is time and site specifically controllable through active management of outside stimuli. The signal induces changes in the stability of the delivery system or some specific reactions which lead to endosomal escape and/or gene release. In the present review, the mechanisms and examples of exogenous triggered gene release approaches are detailed. Challenges and perspectives of such gene delivery systems are also discussed.

Synthesis of Doxorubicin and miRNA Stimuli-Sensitive Conjugates for Combination Therapy

Recent advances in combination therapy by using chemotherapeutic drugs and small noncoding RNAs have highlighted the need for optimization of such agents to allow their carriage in a single delivery system. This protocol details the synthesis of a doxorubicin prodrug, where a NHS coupling reaction was used to sensitize the drug to the proteolytic activity of tumor microenvironments. The design of a lipid-modified miRNA by an S-S coupling reaction is also described. Modification of both, doxorubicin and miRNA, facilitated their simultaneous incorporation into mixed micelles for use in combination therapy against tumor cells.

Non-viral Delivery of Nucleic Acids: Insight Into Mechanisms of Overcoming Intracellular Barriers

Delivery of genes, including plasmid DNAs, short interfering RNAs (siRNAs), and messenger RNAs (mRNAs), using artificial non-viral nanotherapeutics is a promising approach in cancer gene therapy. However, multiple physiological barriers upon systemic administration remain a key challenge in clinical translation of anti-cancer gene therapeutics. Besides extracellular barriers including sequestration of gene delivery nanoparticles from the bloodstream by resident organ-specific macrophages, and their poor extravasation and tissue penetration in tumors, overcoming intracellular barriers is also necessary for successful delivery of nucleic acids. Whereas for RNA delivery the endosomal barrier holds a key importance, transfer of DNA cargo additionally requires translocation into the nucleus. Better understanding of crossing membrane barriers by nucleic acid nanoformulations is essential to the improvement of current non-viral carriers. This review aims to summarize relevant literature on intracellular trafficking of non-viral nanoparticles and determine key factors toward surmounting intracellular barriers. Moreover, recent data allowed us to propose new interpretations of current hypotheses of endosomal escape mechanisms of nucleic acid nanoformulations.

Micelle-like nanoparticles as siRNA and miRNA carriers for cancer therapy

Gene therapy has emerged as an alternative in the treatment of cancer, particularly in cases of resistance to chemo and radiotherapy. Different approaches to deliver genetic material to tumor tissues have been proposed, including the use of small non-coding RNAs due to their multiple mechanisms of action. However, such promise has shown limits in in vivo application related to RNA's biological instability and stimulation of immunity, urging the development of systems able to overcome those barriers. In this review, we discuss the use of RNA interference in cancer therapy with special attention to the role of siRNA and miRNA and to the challenges of their delivery in vivo. We introduce a promising class of drug delivery system known as micelle-like nanoparticles and explore their synthesis and advantages for gene therapy as well as the recent findings in in vitro, in vivo and clinical studies.

Smart polymeric nanoparticles with pH-responsive and PEG-detachable properties for co-delivering paclitaxel and survivin siRNA to enhance antitumor outcomes

Background

The co-delivery of chemotherapeutic agents and small interfering RNA (siRNA) within one cargo can enhance the anticancer outcomes through its synergistic therapeutic effects.

Materials and methods

We prepared smart polymeric nanoparticles (NPs) with pH-responsive and poly(ethylene glycol) (PEG)-detachable properties to systemically co-deliver paclitaxel (PTX) and siRNA against survivin gene for lung cancer therapy. The cationic polyethyleneimine-block-polylactic acid (PEI-PLA) was first synthesized and characterized, with good biocompatibility. PTX was encapsulated into the hydrophobic core of the PEI-PLA polymers by dialysis, and then the survivin siRNA was loaded onto the PTX-loaded NPs (PEI-PLA/PTX) through electrostatic interaction between siRNA and PEI block. Finally, the negatively charged poly(ethylene glycol)-block-poly(L-aspartic acid sodium salt) (PEG-PAsp) was coated onto the surface of NPs by electrostatic interaction to form final smart polymeric NPs with mean particle size of 82.4 nm and zeta potential of 4.1 mV. After uptake of NPs by tumor cells, the PEG-PAsp segments became electrically neutral owing to the lower endosome pH and consequently detached from the smart NPs. This process allowed endosomal escape of the NPs through the proton-sponge effect of the exposed PEI moiety.

Results

The resulting NPs achieved drug loading of 6.04 wt% and exhibited good dispersibility within 24 h in 10% fetal bovine serum (FBS). At pH 5.5, the NPs presented better drug release and cellular uptake than at pH 7.4. The NPs with survivin siRNA effectively knocked down the expression of survivin mRNA and protein owing to enhanced cell uptake of NPs. Cell counting kit-8 (CCK-8) assay showed that the NPs presented low systemic toxicity and improved antiproliferation effect of PTX on A549 cells. Moreover, in vivo studies demonstrated that accumulated NPs in the tumor site were capable of inhibiting the tumor growth and extending the survival rate of the mice by silencing the survivin gene and delivering PTX into tumor cells simultaneously.

Conclusion

These results indicate that the prepared nano-vectors could be a promising co-delivery system for novel chemo/gene combination therapy.

Cholecystokinin Receptor-Targeted Polyplex Nanoparticle Inhibits Growth and Metastasis of Pancreatic Cancer

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) remains the most aggressive malignancy with the lowest 5-year survival rate of all cancers in part owing to the lack of tumor-specific therapy and the rapid metastatic nature of this cancer. The gastrointestinal peptide gastrin is a trophic peptide that stimulates growth of PDAC in an autocrine fashion by interaction with the cholecystokinin receptor that is overexpressed in this malignancy.

METHODS

We developed a therapeutic novel polyplex nanoparticle (NP) that selectively targets the cholecystokinin receptor on PDAC. The NP was characterized in vitro and stability testing was performed in human blood. The effects of the target-specific NP loaded with gastrin small interfering RNA (siRNA) was compared with an untargeted NP and with an NP loaded with a scrambled siRNA in vitro and in 2 orthotopic models of PDAC. A polymerase chain reaction metastasis array examined differentially expressed genes from control tumors compared with tumors of mice treated with the targeted polyplex NP.

RESULTS

The polyplex NP forms a micelle that safely delivers specific gastrin siRNA to the tumor without off-target toxicity. Consistent with these findings, cellular uptake was confirmed only with the targeted fluorescently labeled NP by confocal microscopy in vitro and by IVIS fluorescent based imaging in mice bearing orthotopic pancreatic cancers but not found with untargeted NPs. Tumor uptake and release of the gastrin siRNA NP was verified by decreased cellular gastrin gene expression by quantitative reverse-transcription polymerase chain reaction and peptide expression by immunohistochemistry. Growth of PDAC was inhibited in a dose-related fashion in cell culture and in vivo. The targeted NP therapy completely blocked tumor metastasis and altered tumor-specific genes.

CONCLUSIONS

Our polyplex nanoparticle platform establishes both a strong foundation for the development of receptor-targeted therapeutics and a unique approach for the delivery of siRNA in vivo, thus warranting further exploration of this approach in other types of cancers.

Bioorthogonal strategies for site-directed decoration of biomaterials with therapeutic proteins

Emerging strategies targeting site-specific protein modifications allow for unprecedented selectivity, fast kinetics and mild reaction conditions with high yield. These advances open exciting novel possibilities for the effective bioorthogonal decoration of biomaterials with therapeutic proteins. Site-specificity is particularly important to the therapeutics' end and translated by targeting specific functional groups or introducing new functional groups into the therapeutic at predefined positions. Biomimetic strategies are designed for modification of therapeutics emulating enzymatic strategies found in Nature. These strategies are suitable for a diverse range of applications - not only for protein-polymer conjugation, particle decoration and surface immobilization, but also for the decoration of complex biomaterials and the synthesis of bioresponsive drug delivery systems. This article reviews latest chemical and enzymatic strategies for the biorthogonal decoration of biomaterials with therapeutic proteins and inter-positioned linker structures. Finally, the numerous reports at the interface of biomaterials, linkers, and therapeutic protein decoration are integrated into practical advice for design considerations intended to support the selection of productive ligation strategies.

Synthesis and characterization of small-sized gold nanoparticles coated by bovine serum albumin (BSA) for cancer photothermal therapy

In the present study, small gold nanoparticles <5 nm coated with natural protein Bovine Serum Albumin (BSA) was synthesized and characterized using UV-vis spectrophotometer, Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), zeta potential and scanning electron microscopy (SEM). Three types of cancer cell lines; Rhabdomyosarcoma (RD), Murine fibroblast (L20B) and RAW 264.7 monocyte-macrophage (MQ) were tested and treated by photothermal strategy, in vitro, by conjugating BSA-AuNPs complex of (0.125, 0.25, 0.5 and 1 mg/ml) concentrations with continuous low power laser irradiation, green (532 nm) and near-infrared (NIR) (800 nm) at 0.5, 1, 2 and 3 min, separately. Cytotoxicity effect was determined by MTT assay. The vital impact of photothermal technique has investigated at 1 mg/ml and 3 min irradiation period as identified in RD cell line in comparison with other types; where cytotoxicity more than 74% was reached. Prominent results were demonstrated in the green and NIR region by pH -induced aggregation effect of small nanoparticles inside the cancer cells, which make the small-sized BSA-AuNPs are promising agents for cancer photothermal therapy.

Intertwining DNA-RNA nanocapsules loaded with tumor neoantigens as synergistic nanovaccines for cancer immunotherapy

Nanomedicines that co-deliver DNA, RNA, and peptide therapeutics are highly desirable yet remain underdeveloped for cancer theranostics. Herein, we report self-assembled intertwining DNA-RNA nanocapsules (iDR-NCs) that efficiently delivered synergistic DNA CpG and short hairpin RNA (shRNA) adjuvants, as well as tumor-specific peptide neoantigens into antigen presenting cells (APCs) in lymph nodes for cancer immunotherapy. These nanovaccines were prepared by (1) producing tandem CpG and shRNA via concurrent rolling circle replication and rolling circle transcription, (2) self-assembling CpG and shRNA into DNA-RNA microflowers, (3) shrinking microflowers into iDR-NCs using PEG-grafted cationic polypeptides, and (4) physically loading neoantigen into iDR-NCs. CpG and shRNA in iDR-NCs synergistically activate APCs for sustained antigen presentation. Remarkably, iDR-NC/neoantigen nanovaccines elicit 8-fold more frequent neoantigen-specific peripheral CD8⁺ T cells than CpG, induce T cell memory, and significantly inhibit the progression of neoantigen-specific colorectal tumors. Collectively, iDR-NCs represent potential DNA/RNA/peptide triple-co-delivery nanocarriers and synergistic tumor immunotherapeutic nanovaccines.

Nucleic acid nanomedicines are promising for cancer drug delivery. Here, the authors show using a mouse model the tumor immunotherapeutic efficacy of nanovaccines based on intertwining DNA-RNA nanocapsules loaded with DNA CpG, Stat3-silencing short hairpin RNA and tumor-specific peptide neoantigens.

Functional polymer-based siRNA delivery carrier that recognizes site-specific biosignals

Responsive molecular designs to specific biosignals in microenvironments endow site-specific functionalities with associated polymers. Thus, the construction of small interfering RNA (siRNA) carriers with functional polymers enables smart programs that are triggered by sequential biosignals in a pathway to the targeted cytosol for effective gene silencing. In this review, we explain rational strategies for the design of functional polymers with responsiveness to biosignals and describe the examples of smart carriers for siRNA delivery.

Lipid Nanovectors to Deliver RNA Oligonucleotides in Cancer

The growing knowledge on the mechanisms of gene silencing and gene regulation by non-coding RNAs (ncRNA), mainly small interfering RNA (siRNA) and microRNA (miRNA), is providing a significant boost to the development of new therapeutic strategies for the treatment of cancer. However, the design of RNA-based therapeutics is hampered by biopharmaceutical issues, thus requiring the use of suitable delivery strategies. In this regards, lipid nanovectors have been successfully investigated to deliver RNA in different forms of cancer. Compared to other biomaterials, lipids offer advantages such as biocompatibility, biodegradability, easy production, low cost, limited toxicity and immunogenicity. The possibility to formulate these materials in the form of nanovectors allows overcoming biopharmaceutical issues associated to the therapeutic use of RNA, with the possibility to target tumors. This review takes stock of the main lipid nanovectors proposed to deliver ncRNA. For each considered delivery strategy, the rational design and the most meaningful in vitro and in vivo results are reported and discussed.