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

Redox-Responsive Polymeric Nanoparticle for Nucleic Acid Delivery and Cancer Therapy: Progress, Opportunities, and Challenges

Cancer development and progression of cancer are closely associated with the activation of oncogenes and loss of tumor suppressor genes. Nucleic acid drugs (e.g., siRNA, mRNA, and DNA) are widely used for cancer therapy due to their specific ability to regulate the expression of any cancer-associated genes. However, nucleic acid drugs are negatively charged biomacromolecules that are susceptible to serum nucleases and cannot cross cell membrane. Therefore, specific delivery tools are required to facilitate the intracellular delivery of nucleic acid drugs. In the past few decades, a variety of nanoparticles (NPs) are designed and developed for nucleic acid delivery and cancer therapy. In particular, the polymeric NPs in response to the abnormal redox status in cancer cells have garnered much more attention as their potential in redox-triggered nanostructure dissociation and rapid intracellular release of nucleic acid drugs. In this review, the important genes or signaling pathways regulating the abnormal redox status in cancer cells are briefly introduced and the recent development of redox-responsive NPs for nucleic acid delivery and cancer therapy is systemically summarized. The future development of NPs-mediated nucleic acid delivery and their challenges in clinical translation are also discussed.

Construction of Degradable and Amphiphilic Triblock Polymer Carriers for Effective Delivery of siRNA

The development of effective and safe delivery carriers is one of the prerequisites for the clinical translation of siRNA-based therapeutics. In this study, a library of 144 functional triblock polymers using ring-opening polymerization (ROP) and thiol-ene click reaction is constructed. These triblock polymers are composed of hydrophilic poly (ethylene oxide) (PEO), hydrophobic poly (ε-caprolactone) (PCL), and cationic amine blocks. Three effective carriers are discovered by high-throughput screening of these polymers for siRNA delivery to HeLa-Luc cells. In vitro evaluation shows that siLuc-loaded nanoparticles (NPs) fabricated with leading polymer carriers exhibit sufficient knockdown of luciferase genes and relatively low cytotoxicity. The chemical structure of polymers significantly affects the physicochemical properties of the resulting siRNA-loaded NPs, which leads to different cellular uptake of NPs and endosomal escape of loaded siRNA and thus the overall in vitro siRNA delivery efficacy. After systemic administration to mice with xenograft tumors, siRNA NPs based on P2-4.5A8 are substantially accumulated at tumor sites, suggesting that PEO and PCL blocks are beneficial for improving blood circulation and biodistribution of siRNA NPs. This functional triblock polymer platform may have great potential in the development of siRNA-based therapies for the treatment of cancers.

α-Amino acid N-carboxyanhydride (NCA)-derived synthetic polypeptides for nucleic acids delivery

In recent years, gene therapy has come into the spotlight for the prevention and treatment of a wide range of diseases. Polypeptides have been widely used in mediating nucleic acid delivery, due to their versatilities in chemical structures, desired biodegradability, and low cytotoxicity. Chemistry plays an essential role in the development of innovative polypeptides to address the challenges of producing efficient and safe gene vectors. In this Review, we mainly focused on the latest chemical advances in the design and preparation of polypeptide-based nucleic acid delivery vehicles. We first discussed the synthetic approach of polypeptides via ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs), and introduced the various types of polypeptide-based gene delivery systems. The extracellular and intracellular barriers against nucleic acid delivery were then outlined, followed by detailed review on the recent advances in polypeptide-based delivery systems that can overcome these barriers to enable in vitro and in vivo gene transfection. Finally, we concluded this review with perspectives in this field.

Indocyanine Green and Curcumin Co-Loaded Nano-Fireball-Like Albumin Nanoparticles Based on Near-Infrared-Induced Hyperthermia for Tumor Ablation

Background

Indocyanine green (ICG) has received considerable interest as a biocompatible organic photothermal agent, and curcumin (Cur) is considered an attractive natural chemopreventive and chemotherapeutic compound. However, the in vivo applicability of ICG and Cur is significantly restricted by their poor ability to target tumors and their extremely low solubility.

Materials and Methods

To address these problems, ICG/Cur-loaded albumin nanoparticles (ICG-BSA-Cur-NPs) based on the nab^TM (nanoparticle albumin-bound) technology were applied to neuroblastomas in vivo.

Results

The fabricated ICG-BSA-Cur-NPs were found to be spherical, ~150 nm in size and highly dispersible and stable in aqueous solution. Approximately 80% of the incorporated ICG and Cur were gradually released from the NPs over 48 h. All formulations of ICG-BSA-Cur-NPs (5~20 µg/mL) showed efficient hyperthermia profiles (up to 50–60°C within 5 min) in response to 808-nm NIR laser irradiation in vitro and in vivo. Notably, ICG-BSA-Cur-NPs illuminated with 808-nm laser irradiation (1.5 W/cm²) showed excellent cytotoxicity toward N2a cells in vitro and undisputable antitumor efficacy in N2a-xenografted mice in vivo, compared to other tested sample groups (tumor volumes for PBS, BSA-Cur-NPs, free ICG, and ICG-BSA-Cur-NPs groups were 1408.6 ± 551.9, 1190.6 ± 343.6, 888.6 ± 566.2, and 103.0 ± 111.3 mm³, respectively).

Conclusion

We demonstrate that these hyperthermal chemotherapeutic ICG-BSA-Cur-NPs have potential as a future brain tumor treatment.

Therapeutic siRNA: state of the art

RNA interference (RNAi) is an ancient biological mechanism used to defend against external invasion. It theoretically can silence any disease-related genes in a sequence-specific manner, making small interfering RNA (siRNA) a promising therapeutic modality. After a two-decade journey from its discovery, two approvals of siRNA therapeutics, ONPATTRO® (patisiran) and GIVLAARI™ (givosiran), have been achieved by Alnylam Pharmaceuticals. Reviewing the long-term pharmaceutical history of human beings, siRNA therapy currently has set up an extraordinary milestone, as it has already changed and will continue to change the treatment and management of human diseases. It can be administered quarterly, even twice-yearly, to achieve therapeutic effects, which is not the case for small molecules and antibodies. The drug development process was extremely hard, aiming to surmount complex obstacles, such as how to efficiently and safely deliver siRNAs to desired tissues and cells and how to enhance the performance of siRNAs with respect to their activity, stability, specificity and potential off-target effects. In this review, the evolution of siRNA chemical modifications and their biomedical performance are comprehensively reviewed. All clinically explored and commercialized siRNA delivery platforms, including the GalNAc (N-acetylgalactosamine)-siRNA conjugate, and their fundamental design principles are thoroughly discussed. The latest progress in siRNA therapeutic development is also summarized. This review provides a comprehensive view and roadmap for general readers working in the field.

Self-assembly of poly(allylamine)/siRNA nanoparticles, their intracellular fate and siRNA delivery

Silencing RNA (siRNA) technologies attract significant interest as a therapeutic tool for a large number of diseases. However, the medical translation of this technology is hampered by the lack of effective delivery vehicles for siRNAs in cytosol that prevent their degradation in the bloodstream. The use of molecular complexes based on polyamines have great potential for siRNA delivery as polyamines can protect the siRNA during circulation and at the same time favor siRNA translocation in cytosol. Here, nanoparticles are prepared by complexation of poly(allylamine hydrochloride) (PAH) and siRNA varying the ratio of nitrogen groups from PAH to phosphate groups from siRNA (N/P ratio). Nanoparticles are characterized by transmission electron microscopy and dynamic light scattering. The stability of complexes of green rhodamine labelled PAH (G-PAH) and Cy5 labelled siRNA (R-siRNA) at different pHs and in cell media is studied by fluorescence cross-correlation spectroscopy (FCCS). FCCS studies show that the nanoparticles are stable at physiological pH and in cell media but they disassemble at acidic pH. An optimal N/P ratio of 2 is identified in terms of stability in media, degradation at endosomal pH and toxicity. The intracellular fate of the complexes is studied following uptake in A549 cells. The cross-correlation between G-PAH and R-siRNA decreases substantially 24 h after uptake, while diffusion times of siRNA decrease indicating that the complexes disassemble, liberating the siRNAs. The release of siRNAs into the cytosol is confirmed with parallel confocal laser scanning microscopy. Flow cytometry studies show that PAH/siRNA nanoparticles are effective at silencing green fluorescent protein expression at low N/P ratios at which polyethylenimine/siRNA shows no significant silencing.

Sequential delivery of VEGF siRNA and paclitaxel for PVN destruction, anti-angiogenesis, and tumor cell apoptosis procedurally via a multi-functional polymer micelle

Co-delivery of chemotherapy drugs and VEGF siRNA (siVEGF) to control tumor growth has been a research hotspot for improving cancer treatment. Current systems co-deliver siVEGF and chemo drugs into tumor cells simultaneously. Although effective, these systems do not flow to the abnormal blood vessels around tumor cells (vascular niche, PVN), which play an important role in the metastasis and deterioration of the tumor. Thus, we custom-synthesized triblock copolymer poly(ε-caprolactone)-polyethyleneglycol-poly(L-histidine) (PCL-PEG-PHIS) with previously synthesized folate-PEG-PHIS to construct a targeted multifunctional polymer micelle (PTX/siVEGF-CPPs/TMPM) to sequentially deliver siVEGF-CPPs (disulfide bond-linked siVEGF and cell-penetrating peptides) and paclitaxel (PTX). The sequential delivery vesicles showed the anticipated three-layered TEM structure and dual-convertible (surface charge- and particle size-reversible) features in the tumor environment (pH 6.5), which guaranteed the sequential release of siVEGF-CPPs and PTX in the tumor extracellular environment and tumor cells, respectively. To mimic the in vivo tumor environment, a double cell model was employed by co-culturing HUVECs and MCF-7 cells. Improved cell endocytosis efficiency, VEGF gene silence efficacy, and in vitro anti-proliferation activity were achieved. An in vivo study on MCF-7 tumor-bearing female nude mice also indicated that sequential delivery vesicles could lead to significant induction of tumor cell apoptosis, loss of VEGF expression, and destruction of tumor blood vessels (PVN and neovascularization). These sequential delivery vesicles show potential as an effective co-delivery platform for siVEGF and chemo drugs to improve cancer therapy efficacy.