Polylysine-modified polyethylenimines as siRNA carriers for effective tumor treatment

Novel polyurethane-based ionene nanoparticles electrostatically stabilized with hyaluronic acid for effective gene therapy

Gene therapy is considered to be a valuable strategy for effective cancer treatment. However, the development of effective delivery systems that can specifically deliver gene materials, such as siRNA to tumor tissues plays a critical role in cancer therapy. In the present study, we have developed a novel complex that is based on an electrostatic interaction between cationic polyurethane ionene (CPUI) nanoparticles and an anti-signal transducer and activator of transcription 3 (STAT3) siRNA. For active targeting, hyaluronic acid (HA) was used to coat the complexes, which significantly reduced the cytotoxicity of the blank nanocarriers while demonstrating high transport efficiency of the siRNA via the CD44-mediated endocytosis pathway in MCF-7 breast cancer cells. The targeted nanocarriers (HA/CPUI/siRNA) showed significantly higher cellular internalization in flow cytometry and confocal microscopy compared with the non-targeted system (CPUI/siRNA). In addition, the incorporation of HA on the surface of the complexes resulted in significantly greater suppression of the STAT3 gene compared to the corresponding non-targeted formulation. Whole-body fluorescence images showed more significant tumor accumulation of the targeted nanocarriers in 4T1 breast tumor-bearing mice. Therefore, HA/CPUI/siRNA nanocarriers are an interesting option for the siRNA-targeted treatment of breast cancer cells.

Comparison of tyrosine-modified low molecular weight branched and linear polyethylenimines for siRNA delivery

Polyethylenimines (PEIs) have been previously introduced for siRNA delivery. In particular, in the case of higher molecular weight PEIs, this is associated with toxicity, while low molecular weight PEIs are often insufficient for siRNA complexation. The tyrosine-modification of PEIs has been shown to enhance PEI efficacy and biocompatibility. This paper evaluates a set of tyrosine-modified low molecular weight linear or branched polyethylenimines as efficient carriers of siRNA. Complexation efficacies and biophysical complex properties were analyzed by zeta potential, dynamic light scattering and circular dichroism measurements as well as gel electrophoresis. Biological knockdown was studied in 2 D cell culture and 3 D ex vivo tissue slice air-liquid interface culture. The results demonstrate that siRNAs were able to form stable complexes with all tested polymers. Complexation was able to protect siRNA from degradation by RNase and to mediate target gene knockdown, as determined on the mRNA level and in PC3-Luc3/EGFP and HCT116-Luc3/EGFP expressing reporter cells on the protein level, using flow cytometry and confocal microscopy. The direct comparison of the studied polymers revealed differences in biological efficacies. Moreover, the tyrosine-modified PEIs showed high biocompatibility, as determined by LDH release and mitochondria integrity (J-aggregate assay) as well as caspase 3/7 (apoptosis) and H₂O₂ levels (ROS). In 3 D tissue slices, complexes based on LP10Y proved to be most efficient, by combining tissue penetration with efficient gene expression knockdown.

Unmodified and tyrosine-modified polyethylenimines as potential carriers for siRNA: Biophysical characterization and toxicity

Polyethylenimines (PEIs) are being explored as efficient non-viral nanocarriers for nucleic acid delivery in vitro and in vivo. To address limitations regarding PEI efficacy and biocompatibility, modifications of the chemical structure of linear and branched PEIs have been introduced, including grafting with tyrosine. The aim has been to compare linear and branched polyethylenimines of a wider range of different molecular mass with their tyrosine-modified derivatives. To do so, physico-chemical and biological properties of the polymers were investigated. Even in the absence of a negatively charged nucleic acid counterpart, PEIs form particle structures with defined size and surface potential. Tyrosine modification of PEI led to significantly reduced toxicity, while simultaneously increasing interaction with cellular membranes. All the effects were also dependent on the PEI molecular weight and structure (i.e., linear vs. branched). Especially in the case of linear PEIs, the improved membrane interaction also translated into slightly enhanced hemolysis, whereas their genotoxic potential was essentially abolished. Due to the improvement of properties critical for nano-vector efficacy and biocompatibility, our data demonstrate that tyrosine-modified PEIs are very promising and safe nanocarriers for the delivery of small RNAs, like siRNAs and miRNAs.

Enhancing the in vivo stability of polyanion gene carriers by using PEGylated hyaluronic acid as a shielding system

To increase the in vivo stability of cationic gene carriers and avoid the adverse effects of their positive charge, we synthesized a new shielding material by conjugating low molecular weight polyethylene glycol (PEG) to a hyaluronic acid (HA) core. The HA-PEG conjugate assembled with the positively charged complex, forming a protective layer through electrostatic interactions. DNA/polyetherimide/HA-PEG (DNA/PEI/HA-PEG) nanoparticles had higher stability than both DNA/polyethyleneimine (DNA/PEI) and DNA/PEI/HA complexes. Furthermore, DNA/PEI/HA-PEG nanoparticles also showed a diminished nonspecific response toward serum proteins in vivo. The in vivo transfection efficiency was also enhanced by the low cytotoxicity and the improved stability; therefore, this material might be promising for use in gene delivery applications.

Organobase 1,1,3,3-tetramethyl guanidine catalyzed rapid ring-opening polymerization of α-amino acid N-carboxyanhydrides adaptive to amine, alcohol and carboxyl acid initiators

For amine, hydroxyl and carboxyl terminated initiators, the organobase 1,1,3,3-tetramethylguanidine (TMG) catalyzes the rapid polymerization to afford polypeptides with controllable molecular weights and dispersities.

Highly Enhanced Antitumor Immunity by a Three-Barreled Strategy of the l-Arginine-Promoted Nanovaccine and Gene-Mediated PD-L1 Blockade

Weak T cell responses and immune checkpoints within tumors could be two key factors for limiting antitumor efficacy in the field of cancer immunotherapy. Thus, the combined strategy of tumor vaccines and immune checkpoint blockade has been widely studied and expected to boost antitumor immune responses. Herein, we first developed a two-barreled strategy to combine the nanovaccine with a gene-mediated PD-L1 blockade. On the one hand, polyethyleneimine (PEI) worked as a vaccine carrier to codeliver the antigen ovalbumin (OVA) and the adjuvant unmethylated cytosine-phosphate-guanine (CpG) to formulate the PEI/OVA/CpG nanovaccine through electrostatic binding, which realized both dendritic cell activation and antigen cross-presentation enhancement. On the other hand, the PD-L1 silence gene was loaded by PEI to form PEI/pshPD-L1 complexes, which were further in situ shielded by aldehyde-modified polyethylene glycol (OHC-PEG-CHO) via pH-responsive Schiff base bonds. The formed pshPD-L1@NPs could decrease PD-L1 expression on the tumor cells. However, such a combined two-barreled strategy improved feebly for tumor inhibition in comparison with monotherapy, exhibiting the antagonistic effect, which might be due to the limited T cell response enhancement in the tumor microenvironment. To solve this problem, we have further developed a three-barreled strategy to combine oral administration of l-arginine, which worked as an amplifier to induce robust T cell response enhancement, without causing the upregulation of other negative immune regulators. Superior antitumor behavior and tumor rechallenge protection were realized by the three-barreled strategy in B16F10-OVA (B16-OVA)-bearing mice. The unique three-barreled strategy we developed might offer a novel clinical therapeutic treatment.

Progress on ocular siRNA gene-silencing therapy and drug delivery systems

Age-related macular degeneration (AMD) and glaucoma are global ocular diseases with high blindness rate. RNA interference (RNAi) is being increasingly used in the treatment of these disorders with siRNA drugs, bevasiranib, AGN211745 and PF-04523655 for AMD, and SYL040012 and QPI-1007 for glaucoma. Administration routes and vectors of gene drugs affect their therapeutic effect. Compared with the non-viral vectors, viral vectors have limited payload capacity and potential immunogenicity. This review summarizes the progress of the ocular siRNA gene-silencing therapy by focusing on siRNA drugs for AMD and glaucoma already used in clinical research, the main routes of drug delivery and the non-viral vectors for siRNA drugs.

Poly(l-glutamic acid)-Based Zwitterionic Polymer in a Charge Conversional Shielding System for Gene Therapy of Malignant Tumors

Recently, pH-sensitive polymers have received extensive attention in tumor therapy. However, the rapid response to pH changes is the key to achieving efficient treatment. Here, a novel shielding system with a rapidly pH-responsive polymer (PAMT) is synthesized by click reaction between poly(γ-allyl-l-glutamate) and thioglycolic acid or 2-(Boc-amino)ethanethiol. The zwitterionic biodegradable polymer PAMT, which is negatively charged at physiological pH, can be used to shield positively charged nanoparticles. PAMT is electrostatically attached to the surface of the positively charged PEI/pDNA complex to form a ternary complex. The zwitterionic PAMT-shielded complex exhibits rapid charge conversion when the pH decreases from 7.4 to 6.8. For the in vivo tumor inhibition experiment, PAMT/PEI/shVEGF injected intravenously shows a more significant inhibitory effect on tumor growth. The excellent results are mainly attributed to introduction of the zwitterionic copolymer PAMT, which can shield the positively charged PEI/shVEGF complex in physiological conditions, while the surface potential of the shielded complexes changes to a positive charge in the acidic tumor environment.

Polycations for Gene Delivery: Dilemmas and Solutions

Gene therapy has been a promising strategy for treating numerous gene-associated human diseases by altering specific gene expressions in pathological cells. Application of nonviral gene delivery is hindered by various dilemmas encountered in systemic gene therapy. Therefore, solutions must be established to address the unique requirements of gene-based treatment of diseases. This review will particularly highlight the dilemmas in polycation-based gene therapy by systemic treatment. Several promising strategies, which are expected to overcome these challenges, will be briefly reviewed. This review will also explore the development of polycation-based gene delivery systems for clinical applications.

In situ dual-crosslinked nanoparticles for tumor targeting gene delivery

The instability of gene delivery systems and their "off-target" features are among the major hurdles in gene therapy. In this study, a facile fabrication platform is constructed to endow the gene delivery system with high stability in the circulation system and achieve targeted delivery of plasmid DNA (pDNA) into cancer cells. Aldehyde groups-bearing hyaluronic acid (HA-CHO) is initially synthesized through oxidation, and is then shielded on polyethylenimine/DNA (PEI/DNA) complex particles to form dual-crosslinked nanoparticles in situ. These nanoparticles simultaneously possess electrostatic and chemical crosslinks between outer layers and cores. The dual-crosslinking system further offers the following advantages when used for gene delivery. First, the two different in situ crosslinking routes strengthen nanoparticle stability. Second, targeting ligands on HA layers mediate specific recognition toward cancer cells. Cell and animal experiments demonstrate that the as-prepared complex particles exhibit enhanced stability in serum and excellent long circulation behavior in vivo. Third, the dual-crosslinked nanoparticles present good accumulation ability in tumors after intravenous injection into nude mice bearing HeLa tumors. Overall, the dual-crosslinking strategy is a promising solution for constructing an efficient gene delivery system.

STATEMENT OF SIGNIFICANCE

This manuscript focused on the in situ dual-crosslinked nanoparticles for tumor targeting pDNA delivery. The novel system is prepared by in situ shielding HA-CHO on PEI/DNA complexes. The electrostatic crosslink formed between carboxyl groups on HA-CHO and amine groups on PEI as well as the reaction between aldehyde groups on HA-CHO and amine groups on PEI contributes to the chemical crosslink. By introduction of HA-CHO on PEI/DNA complexes, they show promoting colloidal stability, enhanced cellular uptake and tumor targeting ability. The in vivo experiments further confirm the excellent ability of long circulation and tumor accumulation. Accordingly, HA-CHO2/PEI/DNA has great potential for tumor targeting antitumor therapy.

pH Triggered Size Increasing Gene Carrier for Efficient Tumor Accumulation and Excellent Antitumor Effect

High efficiency and serum resistant capacity are important for gene carrier in vivo usage. In this study, transfection efficiency and cell toxicity of polyethylenimine (PEI) (branched, Mw = 25K) was remarkably improved, when mixed with polyanion (polyethylene glycol-polyglutamic acid (PEG-PLG) or polyglutamic acid (PLG)). Different composite orders of PEI, polyanion, and gene, for example, PEI is first complexed with DNA, and then with polyanion, or PEI is first complexed with polyanion, and then with DNA, were studied. Results showed that only the polyanion/PEI complexes exhibited additional properties, such as decreased pH, resulting in increased particle size, as well as enhanced serum resistance capability and improved tumor accumulation. The prepared gene carrier showed excellent antitumor effect, with no damage on major organs, which is suitable for in vivo gene antitumor therapy.

Gold-Nanorods-Based Gene Carriers with the Capability of Photoacoustic Imaging and Photothermal Therapy

Multifunctional nanoparticles with high gene transfection activity, low cytotoxicity, photoacoustic imaging ability, and photothermal therapeutic properties were prepared by conjugating low-molecular-weight polyethylenimine onto the surfaces of gold nanorods through the formation of stable S-Au bonded conjugates. Results revealed that the gene transfection efficiency of the prepared polyethylenimine-modified gold nanorods (GNRs-PEI1.8k) was higher and their cytotoxicity was less than those of the commercial reagent PEI25k. GNRs-PEI1.8k could also be potentially used as a photoacoustic and photothermal reagent to evaluate the pharmacokinetics, biodistribution, and antitumor effects of gene/drug nanoparticles. Therefore, GNRs-PEI1.8k can be considered a promising candidate for the clinical diagnosis and treatment of tumors.

Production and clinical development of nanoparticles for gene delivery

Gene therapy is a promising strategy for specific treatment of numerous gene-associated human diseases by intentionally altering the gene expression in pathological cells. A successful clinical application of gene-based therapy depends on an efficient gene delivery system. Many efforts have been attempted to improve the safety and efficiency of gene-based therapies. Nanoparticles have been proved to be the most promising vehicles for clinical gene therapy due to their tunable size, shape, surface, and biological behaviors. In this review, the clinical development of nanoparticles for gene delivery will be particularly highlighted. Several promising candidates, which are closest to clinical applications, will be briefly reviewed. Then, the recent developments of nanoparticles for clinical gene therapy will be identified and summarized. Finally, the development of nanoparticles for clinical gene delivery in future will be prospected.

Exploring the in vivo fates of RGD and PEG modified PEI/DNA nanoparticles by optical imaging and optoacoustic imaging

To improve the abilities of long-term circulation and tumor targeting, poly(ethylene glycol) modified polyethylenimine with or without RGD peptide ligands were synthesized and evaluated in detail.

Powering up the molecular therapy of RNA interference by novel nanoparticles

With more suitable for disease treatment due to reduced cellular toxicity, higher loading capacity, and better biocompatibility, nanoparticle-based siRNA delivery systems have proved to be more potent, higher specific and less toxic than the traditional drug therapy.

Charge-conversional zwitterionic copolymer as pH-sensitive shielding system for effective tumor treatment

A novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery is prepared by introducing a rapid charge-conversional zwitterionic copolymer to the positive surface of PEI/pDNA complexes through electrostatic interaction. The shielding system (OEAL) consists of oligoethylenimine (OEI), poly(l-aspartate) (PBLA), and poly(l-lysine) (PLL). The charge-conversional behavior of the OEAL/PEI/DNA ternary complex is evaluated by zeta potential assay. The surface charges of the complexes can change from negative to positive in the pH range of 7.4-6.8. Under a simulative in vivo environment, OEAL/PEI/DNA exhibits promotion of cellular uptake by tumor cells and enhanced gene transfection efficiency because of its good charge-conversional properties. Antitumor experiments further show that the pH-responsive charge-conversional system can mediate a therapeutic gene that can induce tumor apoptosis (pKH3-rev-casp-3) to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment-sensitive gene delivery shielding system for antitumor therapy.

STATEMENT OF SIGNIFICANCE

This manuscript focused on the novel pH-responsive gene delivery system for tumor acidity-targeted pDNA delivery. The novel system is prepared by introducing a rapid charge-conversional zwitterionic copolymer, consisting of oligoethylenimine, poly(l-aspartate) and poly(l-lysine), to the positive surface of PEI/pDNA complexes. The surface charges of the complexes can change from negative to positive from pH 7.4 to 6.8. OEAL/PEI/DNA shows promoting cellular uptake by tumor cells and enhanced gene transfection efficiency. The antitumor experiments further show that the pH responsive charge conversional system can mediate pKH3-rev-casp-3 to achieve effective tumor inhibition. Accordingly, OEAL can be regarded as a promising tumor microenvironment sensitive gene delivery shielding system for antitumor therapy.