Poly(ethylene glycol)-Based Peptidomimetic "PEGtide" of Oligo-Arginine Allows for Efficient siRNA Transfection and Gene Inhibition

A cathepsin B/GSH dual-responsive fluorinated peptide for effective siRNA delivery to cancer cells

Small interfering RNA (siRNA) can be exploited to silence specific genes associated with cancer development, and successful siRNA therapy is highly dependent on the efficiency of the siRNA delivery vector. Herein, a well-designed novel redox- and enzyme-responsive fluorinated polyarginine (PFC-PR) was developed to be used as an anti-cancer siRNA carrier. The multiple guanidine groups could provide positive charges and bind with siRNA efficiently, and further fluorination modification enhanced the interaction with siRNA, resulting in a more stable PFC-PR/siRNA nanocomplex, improving serum tolerance, and promoting cellular uptake and endosome escape. Meanwhile, the PFC-PR was responsive to overexpressed cathepsin B and high levels of glutathione in cancer cells, conferring its ability to enhance siRNA release within cancer cells and making it cancer-targeting. Consequently, PFC-PR showed good biocompatibility and high gene silencing efficiency, which could inhibit cancer cell growth when delivered the siRNA targeting vascular endothelial growth factor, suggesting that it can be potentially used for anti-cancer gene therapy applications.

PEG-mediated transduction of rAAV as a platform for spatially confined and efficient gene delivery

BACKGROUND

Recombinant adeno-associated viruses (rAAV) are commonly used vectors for gene delivery in both basic neuroscience and clinical applications due to their nonpathogenic, minimally immunogenic, and sustained expression properties. However, several challenges remain for the wide-scale rAAV applications, including poor infection of many clinically important cell lines, insufficient expression at low titers, and diffusive transduction in vivo.

METHODS

In this work, PEG, which is a safe and non-toxic polymer of ethylene oxide monomer, was applied as an auxiliary transduction agent to improve the expression of rAAV. In detail, a small dose of PEG was added into the rAAV solution for the transgene expression in cell lines in vitro, and in the central nervous system (CNS) in vivo. The biocompatibility of PEG enhancer was assessed by characterizing the immune responses, cell morphology, cell tropism of rAAV, neuronal apoptosis, as well as motor function of animals.

RESULTS

The results show that small dose of PEG additive can effectively improve the gene expression characteristics of rAAV both in vitro and in vivo. Specifically, the PEG additive allows efficient transgene expression in cell lines that are difficult to be transfected with rAAV alone. In vivo studies show that the PEG additive can promote a spatially confined and efficient transgene expression of low-titer rAAV in the brain over long terms. In addition, no obvious side effects of PEG were observed on CNS in the biocompatibility studies.

CONCLUSIONS

This spatially confined and efficient transduction method can facilitate the applications of rAAV in fundamental research, especially in the precise dissection of neural circuits, and also improve the capabilities of rAAV in the treatment of neurological diseases which originate from the disorders of small nuclei in the brain.

Smart arginine-equipped polycationic nanoparticles for p/CRISPR delivery into cells

An efficient and safe delivery system for the transfection of CRISPR plasmid (p/CRISPR) into target cells can open new avenues for the treatment of various diseases. Herein, we design a novel nonvehicle by integrating an arginine-disulfide linker with low-molecular-weight PEI (PEI_1.8k) for the delivery of p/CRISPR. These PEI_1.8k-Arg nanoparticles facilitate the plasmid release and improve both membrane permeability and nuclear localization, thereby exhibiting higher transfection efficiency compared to native PEI_1.8kin the delivery of nanocomplexes composed of PEI_1.8k-Arg and p/CRISPR into conventional cells (HEK 293T). This nanovehicle is also able to transfect p/CRISPR in a wide variety of cells, including hard-to-transfect primary cells (HUVECs), cancer cells (HeLa), and neuronal cells (PC-12) with nearly 5-10 times higher efficiency compared to the polymeric gold standard transfection agent. Furthermore, the PEI_1.8k-Arg nanoparticles can edit the GFP gene in the HEK 293T-GFP reporter cell line by delivering all possible forms of CRISPR/Cas9 system (e.g. plasmid encoding Cas9 and sgRNA targeting GFP, and Cas9/sgRNA ribonucleoproteins (RNPs) as well as Cas9 expression plasmid andin vitro-prepared sgRNA) into HEK 293T-GFP cells. The successful delivery of p/CRISPR into local brain tissue is also another remarkable capability of these nanoparticles. In view of all the exceptional benefits of this safe nanocarrier, it is expected to break new ground in the field of gene editing, particularly for therapeutic purposes.

How Far Are Non-Viral Vectors to Come of Age and Reach Clinical Translation in Gene Therapy?

Efficient delivery of genetic material into cells is a critical process to translate gene therapy into clinical practice. In this sense, the increased knowledge acquired during past years in the molecular biology and nanotechnology fields has contributed to the development of different kinds of non-viral vector systems as a promising alternative to virus-based gene delivery counterparts. Consequently, the development of non-viral vectors has gained attention, and nowadays, gene delivery mediated by these systems is considered as the cornerstone of modern gene therapy due to relevant advantages such as low toxicity, poor immunogenicity and high packing capacity. However, despite these relevant advantages, non-viral vectors have been poorly translated into clinical success. This review addresses some critical issues that need to be considered for clinical practice application of non-viral vectors in mainstream medicine, such as efficiency, biocompatibility, long-lasting effect, route of administration, design of experimental condition or commercialization process. In addition, potential strategies for overcoming main hurdles are also addressed. Overall, this review aims to raise awareness among the scientific community and help researchers gain knowledge in the design of safe and efficient non-viral gene delivery systems for clinical applications to progress in the gene therapy field.

Antimicrobial PEGtides: A Modular Poly(ethylene glycol)-Based Peptidomimetic Approach to Combat Bacteria

Despite their high potency, the widespread implementation of natural antimicrobial peptides is still challenging due to their low scalability and high hemolytic activities. Herein, we address these issues by employing a modular approach to mimic the key amino acid residues present in antimicrobial peptides, such as lysine, leucine, and serine, but on the highly biocompatible poly(ethylene glycol) (PEG) backbone. A series of these PEG-based peptides (PEGtides) were developed using functional epoxide monomers, corresponding to each key amino acid, with several possessing highly potent bactericidal activities and controlled selectivities, with respect to their hemolytic behavior. The critical role of the composition and the structure of the PEGtides in their selectivities was further supported by coarse-grained molecular dynamic simulations. This modular approach is anticipated to provide the design principles necessary for the future development of antimicrobial polymers.

Engineering a sustained release vaccine with a pathogen-mimicking manner for robust and durable immune responses

Sustained release vaccine carriers can facilitate an increased interaction time between the antigen and immune system to strengthen immune responses, but their promotion on adaptive immune responses, especially cellular immunity, are still unfavorable. Herein, we report a sustained antigen delivery vector, which carries abundant antigens, a nucleic acid adjuvant and pathogen-associated molecular patterns to simulate a natural pathogen to reinforce immune responses. Specifically, murine colorectal cancer cells MC38 lysate and Toll-like receptor 9 agonist CpG are loaded into yeast derived β-glucan particles (GPs). After vaccination, these particles can form a vaccine depot that continuously release the antigen similar to the traditional aluminum hydroxide gel, but recruit more immune cells and induce more cytokine secretion at the injection site. Stronger antibody responses, Th1 and Th17 biased cellular immunity and immune memory are achieved compared with aluminum hydroxide gel. More importantly, treatment with these particles significantly suppress tumor growth in a therapeutic tumor model. This work shed light on the efficacy of combining sustained antigen release with pathogen-mimicking manner in vaccine design.

In Vitro and In Vivo Assessment of PEGylated PEI for Anti-IL-8/CxCL-1 siRNA Delivery to the Lungs

Inhalation offers a means of rapid, local delivery of siRNA to treat a range of autoimmune or inflammatory respiratory conditions. This work investigated the potential of a linear 10 kDa Poly(ethylene glycol) (PEG)-modified 25 kDa branched polyethyleneimine (PEI) (PEI-LPEG) to effectively deliver siRNA to airway epithelial cells. Following optimization with anti- glyceraldehyde 3-phosphate dehydrogenase (GAPDH) siRNA, PEI and PEI-LPEG anti-IL8 siRNA nanoparticles were assessed for efficacy using polarised Calu-3 human airway epithelial cells and a twin stage impinger (TSI) in vitro lung model. Studies were then advanced to an in vivo lipopolysaccharide (LPS)-stimulated rodent model of inflammation. In parallel, the suitability of the siRNA-loaded nanoparticles for nebulization using a vibrating mesh nebuliser was assessed. The siRNA nanoparticles were nebulised using an Aerogen^® Pro vibrating mesh nebuliser and characterised for aerosol output, droplet size and fine particle fraction. Only PEI anti-IL8 siRNA nanoparticles were capable of significant levels of IL-8 knockdown in vitro in non-nebulised samples. However, on nebulization through a TSI, only PEI-PEG siRNA nanoparticles demonstrated significant decreases in gene and protein expression in polarised Calu-3 cells. In vivo, both anti-CXCL-1 (rat IL-8 homologue) nanoparticles demonstrated a decreased CXCL-1 gene expression in lung tissue, but this was non-significant. However, PEI anti-CXCL-1 siRNA-treated rats were found to have significantly less infiltrating macrophages in their bronchoalveolar lavage (BAL) fluid. Overall, the in vivo gene and protein inhibition findings indicated a result more reminiscent of the in vitro bolus delivery rather than the in vitro nebulization data. This work demonstrates the potential of nebulised PEI-PEG siRNA nanoparticles in modulating pulmonary inflammation and highlights the need to move towards more relevant in vitro and in vivo models for respiratory drug development.