Targeted minicircle DNA delivery using folate–poly(ethylene glycol)–polyethylenimine as non-viral carrier

Polyethylenimine (PEI) in gene therapy: Current status and clinical applications

Polyethlyenimine (PEI) was introduced 1995 as a cationic polymer for nucleic acid delivery. PEI and its derivatives are extensively used in basic research and as reference formulations in the field of polymer-based gene delivery. Despite its widespread use, the number of clinical applications to date is limited. Thus, this review aims to consolidate the past applications of PEI in DNA delivery, elucidate the obstacles that hinder its transition to clinical use, and highlight potential prospects for novel iterations of PEI derivatives. The present review article is divided into three sections. The first section examines the mechanism of action employed by PEI, examining fundamental aspects of cellular delivery including uptake mechanisms, release from endosomes, and transport into the cell nucleus, along with potential strategies for enhancing these delivery phases. Moreover, an in-depth analysis is conducted concerning the mechanism underlying cellular toxicity, accompanied with approaches to overcome this major challenge. The second part is devoted to the in vivo performance of PEI and its application in various therapeutic indications. While systemic administration has proven to be challenging, alternative localized delivery routes hold promise, such as treatment of solid tumors, application as a vaccine, or serving as a therapeutic agent for pulmonary delivery. In the last section, the outcome of completed and ongoing clinical trials is summarized. Finally, an expert opinion is provided on the potential of PEI and its future applications. PEI-based formulations for nucleic acid delivery have a promising potential, it will be an important task for the years to come to introduce innovations that address PEI-associated shortcomings by introducing well-designed PEI formulations in combination with an appropriate route of administration.

BSA-PEI Nanoparticle Mediated Efficient Delivery of CRISPR/Cas9 into MDA-MB-231 Cells

The discovery of bacterial-derived Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system has revolutionized genome engineering and gene therapy due to its wide range of applications. One of the major challenging issues in CRISPR/Cas system is the lack of an efficient, safe, and clinically suitable delivery of the system’s components into target cells. Here, we describe the development of polyethylenimine coated-bovine serum albumin nanoparticles (BSA-PEI NPs) for efficient delivery of CRISPR/Cas9 system in both DNA (px458 plasmid) and ribonucleoprotein (RNP) forms into MDA-MB-231 human breast cancer cell line. Our data showed that synthesized BSA-PEI (BP) NPs delivered plasmid px458 at concentrations of 0.15, 0.25, and 0.35 µg/µl with efficiencies of approximately 29.7, 54.8, and 84.1% into MDA-MB-231 cells, respectively. Our study demonstrated that Cas9/sgRNA RNP complex efficiently (~ 92.6%) delivered by BSA-PEI NPs into the same cells. Analysis of toxicity and biocompatibility of synthesized NPs on human red blood cells, MDA-MB-231 cells, and mice showed that the selected concentration (28 µg/µl) of BSA-PEI NPs for transfection had no remarkable toxicity effects. Thus, obtained results suggest BSA-PEI NPs as one of the most promising carrier for delivering CRISPR/Cas9 to target cells.

New approaches to moderate CRISPR-Cas9 activity: Addressing issues of cellular uptake and endosomal escape

CRISPR-Cas9 is rapidly entering molecular biology and biomedicine as a promising gene-editing tool. A unique feature of CRISPR-Cas9 is a single-guide RNA directing a Cas9 nuclease toward its genomic target. Herein, we highlight new approaches for improving cellular uptake and endosomal escape of CRISPR-Cas9. As opposed to other recently published works, this review is focused on non-viral carriers as a means to facilitate the cellular uptake of CRISPR-Cas9 through endocytosis. The majority of non-viral carriers, such as gold nanoparticles, polymer nanoparticles, lipid nanoparticles, and nanoscale zeolitic imidazole frameworks, is developed with a focus toward optimizing the endosomal escape of CRISPR-Cas9 by taking advantage of the acidic environment in the late endosomes. Among the most broadly used methods for in vitro and ex vivo ribonucleotide protein transfection are electroporation and microinjection. Thus, other delivery formats are warranted for in vivo delivery of CRISPR-Cas9. Herein, we specifically revise the use of peptide and nanoparticle-based systems as platforms for CRISPR-Cas9 delivery in vivo. Finally, we highlight future perspectives of the CRISPR-Cas9 gene-editing tool and the prospects of using non-viral vectors to improve its bioavailability and therapeutic potential.

A novel immunochemotherapy based on targeting of cyclooxygenase and induction of immunogenic cell death

Cyclooxygenase (COX) plays a crucial role in the "inflammogenesis of cancer", which leads to tumor progression, metastasis, and immunotherapy resistance. Therefore, reducing "inflammogenesis" by COX inhibition may be a key perspective for cancer therapy. However, the role of tumor-derived COX in the actions of COX inhibitors remains incompletely understood. In this study, applying "old drug new tricks" to repurpose 5-aminosalicylic acid (5-ASA), a COX inhibitor, we examined the effect of 5-ASA, alone or in combination with doxorubicin (DOX), in several cancer cell lines with different levels of COX expression. To facilitate the evaluation of the combination effect on tumors in vivo, a new micellar carrier based on PEG-b-PNHS polymer-conjugated 5-ASA (PASA) was developed to enhance codelivery of 5-ASA and DOX. Folate was also introduced to the polymer (folate-PEG-NH₂-conjugated PASA (FASA)) to further improve delivery to tumors via targeting both tumor cells and tumor macrophages. An unprecedented high DOX loading capacity of 42.28% was achieved through various mechanisms of carrier/drug interactions. FASA was highly effective in targeting to and in inhibiting the growth of both 4T1.2 and CT26 tumors in BALB/c mice. However, FASA was more effective in CT26 tumor that has a high level of COX expression. Codelivery of DOX via PASA and FASA led to a further improvement in antitumor activity. Mechanistic studies suggest that inhibition of COX in vivo led to a more active tumor immune microenvironment. Interestingly, treatment with FASA led to upregulation of PD-1 on T cells, likely due to repressing the inhibitory effect of prostaglandin E2 (PGE₂) on PD-1 expression on T cells. Combination of FASA/DOX with anti-PD-1 antibody led to a drastic improvement in the overall antitumor activity including regression of some established tumors at a suboptimal dose of FASA/DOX. Our data suggest that FASA/DOX may represent a new and effective immunochemotherapy for various types of cancers, particularly those cancers with high levels of COX expression.

An optimized mesoporous silica nanosphere-based carrier system with chemically removable Au nanoparticle caps for redox-stimulated and targeted drug delivery

To date, numerous drug delivery systems based on mesoporous silica nanoparticles (MSNs) have been explored, but little has been done on optimizing the structure and composition of MSNs to achieve effective drug delivery for cancer cells. Ideal mesoporous drug carriers should incorporate drugs in a way that prevents pre-release in biological surroundings before reaching the targeted area, which usually requires the capping of the open ends on the surface and the incorporation of targeting ligands on the exterior of nanocarriers. In this study, an MSN-based drug carrier system was synthesized with biocompatible Au nanoparticles (NPs) as the 'hard caps', and folic acid conjugated to the surface for targeting folate receptor-overexpressed cancer cells. Disulfide bonds linking Au and MSN NPs were introduced to the MSN surface as the redox-sensitive and chemically removable components. To study the effect of structures of MSNs in drug release, three types of MSNs were compared, including hollow mesoporous silica NPs, large-pore hollow mesoporous silica NPs and typical nano-sized pores on the surface (MSN). To achieve optimal coverage of thiol groups, two methods of functionalization were compared in effecting drug loading and release in vitro. Finally, the effect of residual surfactant was also discussed in anticancer studies. Therefore, the appropriate MSN nanostructure for redox-sensitive and targeted drug delivery was optimized.

"Watson-Crick G[triple bond, length as m-dash]C"-inspired supramolecular nanodrug of methotrexate and 5-fluorouracil for tumor microenvironment-activatable self-recognizing synergistic chemotherapy

Carrier-free nanodrugs, generated via the straightforward small-molecule self-assembly of anticancer drugs, provide a promising route for cancer chemotherapy. However, their low structural stability, lack of targeting specificity, and poor stimulus responsiveness are still limiting their therapeutic effect. Inspired by Watson-Crick G[triple bond, length as m-dash]C base pairing, the FDA-approved chemo-drug methotrexate (MTX, which can bind with folate receptors) and 5-fluorouracil (5-FU, a DNA/RNA synthetase inhibitor) were adopted for direct assembly into self-recognizing MTX-5-FU nanoparticles via "Watson-Crick-like base pairing"-driven precise supramolecular assembly. Sequentially, our synthesized weak acidity-responsive polyethylene glycol (PEG) was inserted onto the nanoparticle surface to temporarily shield the self-targeting function of MTX and prolong the blood circulation time. Once PEG-MTX-5-FU nanoparticles reached the weakly acidic tumor microenvironment, the PEG corona could be cleaved from their surface and then MTX could be re-exposed to recover its self-recognition ability and significantly elevate tumor cell uptake; furthermore, the de-PEGylated MTX-5-FU nanoparticles could respond to the stronger acidity of lysosome, triggering core disassembly and thus the burst release of both MTX and 5-FU. Further in vitro and in vivo studies consistently confirmed that the nanodrugs exhibited preferable accumulation at the tumor sites with highly synergistic chemotherapeutic effects. The supramolecular recognition-inspired, cascade-triggered self-targeting and controlled release of nanodrugs could be a promising strategy to improve synergistic chemotherapy.

Ligand targeting and peptide functionalized polymers as non-viral carriers for gene therapy

Ligand targeting and peptide functionalized polymers serve as gene carriers for efficient gene delivery.

Methotrexate-Coated Complexes of Plasmid DNA and Polyethylenimine for Gene Delivery

Folate receptors are overexpressed on the surface cancer cells. We successfully constructed a new gene delivery vector of methotrexate (MTX)-coated plasmid DNA-polyethylenimine (pDNA-PEI) complexes (PEI complexes) by electrostatic binding. The stable anionic nanoparticle was optimized at MTX charge ratios of 120 or more. pDNA-PEI-MTX complexes (MTX complexes) demonstrated gene expression efficiency as high as cationic pDNA-PEI complexes in the mouse melanoma cell line, B16-F10. The MTX complexes were taken up by the cell-specific uptake mechanisms via the folate receptor. MTX-coated complexes are useful as endocytosis ligands. The MTX120 complexes exhibited no blood aggregation. The transgene efficiency of MTX120 complexes in the liver and spleen after their intravenous administration was higher than that of PEI complexes. Therefore, MTX complexes are expected as a new gene vector in the future.

Drug-Loaded Polymeric Nanoparticles for Cancer Stem Cell Targeting

Cancer stem cells (CSCs) have been reported to play critical roles in tumor initiation, propagation, and regeneration of cancer. Nano-size vehicles are employed to deliver drugs to target the CSCs for cancer therapy. Polymeric nanoparticles have been considered as the most efficient vehicles for drug delivery due to their excellent pharmacokinetic properties. The CSCs specific antibodies or ligands can be conjugated onto the surface or interior of nanoparticles to successfully target and finally eliminate CSCs. In this review, we focus on the approaches of polymeric nanoparticles design for loading drug, and their potential application for CSCs targeting in cancer therapy.

Silver nanoparticle-embedded graphene oxide-methotrexate for targeted cancer treatment

Combination therapies are widely investigated cancer treatment modalities. Carbon based systems such as graphene oxide (GO), plasmonic nanoparticles such as silver nanoparticles (AgNPs), and the folate analog, methotrexate (MTX), have been separately studied for their potential anticancer effects. In this study, we combined these systems to develop AgNPs-embedded GO with conjugated MTX (MTX-GO/AgNPs) and studied their folate receptor-targeted anticancer effects. Results revealed successful formation of AgNPs on GO along with MTX conjugation as suggested by UV/visible, TEM, AFM, FTIR, and XRD analysis. Folate receptor-positive MCF-7 cells were more prone to cytotoxic effects of MTX-GO/AgNPs compared to folate receptor-negative HepG2 cells. Folic acid analog MTX interacts with folate receptors expressed in MCF-7 cells, improving cellular uptake and subsequent anticancer effects of the system. Importantly, AgNPs enhanced the total ROS production within the treated cells leading to improve cellular apoptosis, as evidenced by western blot. Moreover, near infrared (NIR)-induced photothermal effects of GO improved the anticancer activity of the system. Therefore, the combinational therapy system MTX-GO/AgNPs can be potentially applied for effective folate receptor-targeted treatment of cancers.

Folate-Mediated Targeted Delivery of Combination Chemotherapeutics Loaded Reduced Graphene Oxide for Synergistic Chemo-Photothermal Therapy of Cancers

PURPOSE

Larger surface area for drug incorporation and superior optical activity makes reduced graphene oxide (rGO) a suitable drug carrier for combination chemotherapeutics delivery. And folate receptors are potential mediators for cancer targeted delivery. This study mainly aimed to prepare irinotecan (IRI)- and docetaxel (DOC)-loaded, folate (FA)-conjugated rGO (FA-P407-rGO/ID) for synergistic cancer therapy.

METHODS

FA-P407-rGO/ID was prepared as aqueous dispersion. Characterization was performed using high performance liquid chromatography (HPLC), transmission electron microscopy (TEM), atomic force microscopy (AFM), ultraviolet/visible spectroscopy, fourier transform infrared spectroscopy (FTIR) and drug release. In vitro cellular studies were performed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), fluorescence-activated cell sorting (FACS) and western blot analyses.

RESULTS

Our results revealed successful preparation of stable FA-P407-rGO/ID formulation with enhanced drug release profiles in acidic microenvironment. In vitro cytotoxicity of the formulation on folate receptor-expressing human mammary carcinoma (MCF-7) cells was higher than that when free IRI/DOC combination (ID) was used; such increased cytotoxicity was not observed in folate receptor-negative hepatocellular carcinoma (HepG2) cells. Cellular uptake of FA-P407-rGO/ID in MCF-7 cells was higher than in HepG2 cells. Further, FACS and western blot analysis revealed better apoptotic effects of the formulation in MCF-7 cells than in HepG2 cells, suggesting the important role of folate receptors for targeted chemotherapy delivery to cancer cells. Near infrared irradiation further enhanced the apoptotic effect in cancer cells, resulting from the photothermal effects of rGO.

CONCLUSIONS

Hence, FA-P407-rGO/ID can be considered as a potential formulation for folate-targeted chemo-photothermal therapy in cancer cells.

Conjugates of small targeting molecules to non-viral vectors for the mediation of siRNA

To use siRNA (small interfering RNA) for gene therapy, a gene delivery system is often necessary to overcome several challenging requirements including rapid excretion, low stability in blood serum, non-specific accumulation in tissues, poor cellular uptake and inefficient intracellular release. Active and/or passive targeting should help the delivery system to reach the desired tissue or cell, to be internalized, and to deliver siRNA to the cytoplasm so that siRNA can inhibit protein synthesis. This review covers conjugates of small targeting molecules and non-viral delivery systems for the mediation of siRNA, with a focus on their transfection properties in order to help the development of new and efficient siRNA delivery systems, as the therapeutic solutions of tomorrow.

STATEMENT OF SIGNIFICANCE

The delivery of siRNA into cells or tissues remains to be a challenge for its applications, an alternative strategy for siRNA delivery systems is direct conjugation of non-viral vectors with targeting moieties for cellular delivery. In comparison to macromolecules, small targeting molecules have attracted great attention due to their many potential advantages including significant simplicity and ease of production, good repeatability and biodegradability. This review will focus on the most recent advances in the delivery of siRNA using conjugates of small targeting molecules and non-viral delivery systems. Based the editor's suggestions, we hope the revised manuscript could provide more profound understanding to the conjugates of targeting molecules to vectors for mediation of siRNA.

Multifunctional oligomer incorporation: a potent strategy to enhance the transfection activity of poly(l-lysine)

The multifunctional oligomer incorporation strategy is used for the first time to evaluate target effects by the ligand modified oligomer assembly, forming complexes with DNA and polycations.

Synergistic Integration of Layer-by-Layer Assembly of Photosensitizer and Gold Nanorings for Enhanced Photodynamic Therapy in the Near Infrared

A layer-by-layer (LbL) assembly strategy was used to incorporate high concentrations of Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) photosensitizer (PS) onto plasmonic Au nanorings (Au NRs) for increasing the cellular uptake of AlPcS4 and subsequently enhancing the efficacy of photodynamic therapy (PDT) of human breast cancer cells (MDA-MB-231) in the near-infrared (NIR) range. Au NRs with two layers of AlPcS4 (Au NR/(AlPcS4)2) markedly increased the cellular internalization of AlPcS4 and elevated the generation of reactive oxygen species (ROS). Quenching the photosensitivity of AlPcS4 on the Au NR surface during the uptake and then significant ROS formation only upon PS release inside the cellular compartment made it possible to achieve a high PDT specificity and efficacy. PDT of breast cancer cells following 4 h of incubation with various formula revealed the following cell destruction rate: ∼10% with free AlPcS4, ∼23% with singly layered Au NR/(AlPcS4)1 complex, and ∼50% with doubly layered Au NR/(AlPcS4)2. Incubation with Au NR/(AlPcS4)2 for an additional 2 h resulted in ∼85% cell killing, more than 8-fold increase compared to AlPcS4 alone. Together, integration of LbL of PS with Au NRs holds a significant promise for PDT therapeutic treatment of a variety of cancers.

Gas-generating TPGS-PLGA microspheres loaded with nanoparticles (NIMPS) for co-delivery of minicircle DNA and anti-tumoral drugs

Drug-DNA combination therapies are receiving an ever growing focus due to their potential for improving cancer treatment. However, such approaches are still limited by the lack of multipurpose delivery systems that encapsulate drugs and condense DNA simultaneously. In this study, we describe the successful formulation of gas-generating pH-responsive D-α-tocopherol PEG succinate-poly(D,L-lactic-co-glycolic acid) (TPGS-PLGA) hollow microspheres loaded with both Doxorubicin (Dox) and minicircle DNA (mcDNA) nanoparticles as a strategy to co-deliver these therapeutics. For this study mcDNA vectors were chosen due to their increased therapeutic efficiency in comparison to standard plasmid DNA. The results demonstrate that TPGS-PLGA microcarriers can encapsulate Dox and chitosan nanoparticles completely condense mcDNA. The loading of mcDNA-nanoparticles into microspheres was confirmed by 3D confocal microscopy and co-localization analysis. The resulting TPGS-PLGA-Dox-mcDNA nanoparticle-in-microsphere hybrid carriers exhibit a well-defined spherical shape and neutral surface charge. Microcarriers incubation in acidic pH produced a gas-mediated Dox release, corroborating the microcarriers stimuli-responsive character. Also, the dual-loaded TPGS-PLGA particles achieved 5.2-fold higher cellular internalization in comparison with non-pegylated microspheres. This increased intracellular concentration resulted in a higher cytotoxic effect. Successful transgene expression was obtained after nanoparticle-mcDNA co-delivery in the microspheres. Overall these findings support the concept of using nanoparticle-microsphere multipart systems to achieve efficient co-delivery of various drug-mcDNA combinations.

Targeted polymeric nanoparticles for cancer gene therapy

In this article, advances in designing polymeric nanoparticles for targeted cancer gene therapy are reviewed. Characterization and evaluation of biomaterials, targeting ligands, and transcriptional elements are each discussed. Advances in biomaterials have driven improvements to nanoparticle stability and tissue targeting, conjugation of ligands to the surface of polymeric nanoparticles enable binding to specific cancer cells, and the design of transcriptional elements has enabled selective DNA expression specific to the cancer cells. Together, these features have improved the performance of polymeric nanoparticles as targeted non-viral gene delivery vectors to treat cancer. As polymeric nanoparticles can be designed to be biodegradable, non-toxic, and to have reduced immunogenicity and tumorigenicity compared to viral platforms, they have significant potential for clinical use. Results of polymeric gene therapy in clinical trials and future directions for the engineering of nanoparticle systems for targeted cancer gene therapy are also presented.

Using inositol as a biocompatible ligand for efficient transgene expression

Transgene transfection techniques using cationic polymers such as polyethylenimines (PEIs) and PEI derivatives as gene vectors have shown efficacy, although they also have shortcomings. PEIs have decent DNA-binding capability and good cell internalization performance, but they cannot deliver gene payloads very efficiently to cell nuclei. In this study, three hyperbranched polyglycerol-polyethylenimine (PG6-PEI) polymers conjugated with myo-inositol (INO) molecules were developed. The three resulting PG6-PEI-INO polymers have an increased number of INO ligands per molecule. PG6-PEI-INO 1 had only 14 carboxymethyl INO (CMINO) units per molecule. PG6-PEI-INO 2 had approximately 130 CMINO units per molecule. PG6-PEI-INO 3 had as high as 415 CMINO units approximately. Mixing PG6-PEI-INO polymers with DNA produced compact nanocomposites. We then performed localization studies using fluorescent microscopy. As the number of conjugated inositol ligands increased in PG6-PEI-INO polymers, there was a corresponding increase in accumulation of the polymers within 293T cell nuclei. Transfection performed with spherical 293T cells yielded 82% of EGFP-positive cells when using PG6-PEI-INO 3 as the vehicle. Studies further revealed that extracellular adenosine triphosphate (eATP) can inhibit the transgene efficiency of PG6-PEI-INO polymers, as compared with PEI and PG6-PEI that were not conjugated with inositol. Our work unveiled the possibility of using inositol as an effective ligand for transgene expression.

Dendrimeric anticancer prodrugs for targeted delivery of ursolic acid to folate receptor-expressing cancer cells: synthesis and biological evaluation

The anticancer efficacy of ursolic acid (UA) was limited by poor water solubility, non-specific tumor distribution, and low bioavailability. To overcome this problem, polyamidoamine (PAMAM) conjugated with UA and folic acid (FA) as novel dendrimeric prodrugs were designed and successfully synthesized by a concise one-pot synthetic approach. Both FA and UA were covalently conjugated to the surface of PAMAM through acid-labile ester bonds and the covalently linked UA could be hydrolysed either in acidic (pH 5.4) or in neutral (pH 7.4) PBS solution. The cellular uptake study indicated that the presence of FA enhanced uptake of the dendrimeric prodrugs in folate receptor (FR) over-expressing Hela cells. The enhanced cellular uptake could be due to the electrostatic absorptive endocytosis and FR-mediated endocytosis. In contrast, for HepG2 cells, a FR-negative cell line, FA conjugation on the surface of the dendrimer showed no effect on the cellular uptake. In MTT assay and cell cycle analysis, FA-modified dendrimeric prodrugs showed significantly enhanced toxicity than non-FA-modified ones in Hela cells. These results suggested that FA-modified dendrimeric UA prodrugs have the potential for targeted delivery of UA into cancer cells to improve its anti-tumor efficacy.

Ligand-functionalized degradable polyplexes formed by cationic poly(aspartic acid)-grafted chitosan-cyclodextrin conjugates

Polypeptide-based degradable polyplexes attracted considerable attention in drug delivery systems. Polysaccharides including cyclodextrin (CD), dextran, and chitosan (CS) were readily grafted with cationic poly(aspartic acid)s (PAsps). To further enhance the transfection performances of PAsp-based polyplexes, herein, different types of ligand (folic acid, FA)-functionalized degradable polyplexes were proposed based on the PAsp-grafted chitosan-cyclodextrin conjugate (CCPE), where multiple β-CDs were tied on a CS chain. The FA-functionalized CCPE (i.e., CCPE-FA) was obtained via a host-guest interaction between the CD units of CCPE and the adamantane (Ad) species of Ad-modified FA (Ad-FA). The resulting CCPE/pDNA, CCPE-FA/pDNA, and ternary CCPE-FA/CCPE/pDNA (prepared by layer-by-layer assembly) polyplexes were investigated in detail using different cell lines. The CCPE-based polyplexes displayed much higher transfection efficiencies than the CS-based polyplexes reported earlier by us. The ternary polyplexes of CCPE-FA/CCPE/pDNA produced excellent gene transfection abilities in the folate receptor (FR)-positive tumor cells. This work would provide a promising means to produce highly efficient polyplexes for future gene therapy applications.

Mesoporous silica nanoparticles for 19F magnetic resonance imaging, fluorescence imaging, and drug delivery

Multifunctional mesoporous silica nanoparticles (MSNs) are good candidates for multimodal applications in drug delivery, bioimaging, and cell targeting. In particular, controlled release of drugs from MSN pores constitutes one of the superior features of MSNs. In this study, a novel drug delivery carrier based on MSNs, which encapsulated highly sensitive 19F magnetic resonance imaging (MRI) contrast agents inside MSNs, was developed. The nanoparticles were labeled with fluorescent dyes and functionalized with small molecule-based ligands for active targeting. This drug delivery system facilitated the monitoring of the biodistribution of the drug carrier by dual modal imaging (NIR/19F MRI). Furthermore, we demonstrated targeted drug delivery and cellular imaging by the conjugation of nanoparticles with folic acid. An anticancer drug (doxorubicin, DOX) was loaded in the pores of folate-functionalized MSNs for intracellular drug delivery. The release rates of DOX from the nanoparticles increased under acidic conditions, and were favorable for controlled drug release to cancer cells. Our results suggested that MSNs may serve as promising 19F MRI-traceable drug carriers for application in cancer therapy and bio-imaging.

Tumor-targeted paclitaxel-loaded folate conjugated poly(ethylene glycol)-poly(L-lactide) microparticles produced by supercritical fluid technology

The new biodegradable diblock copolymers poly(ethylene glycol)-poly(L-lactide) (PEG-PLLA) were synthesized and were chemically conjugated with folate (FA) in the PEG terminal ends to form FA-PEG-PLLA. Then the hydrophobic drug paclitaxel (PTX) loaded microparticles (PTX/FA-PEG-PLLA) were produced via solution enhanced dispersion by supercritical fluids (SEDS). These microparticles exhibited sphere-like shape by scanning electron microscopy observation and showed narrow hydrodynamic size distributions by dynamic light scattering measurement. Drug loading of PTX loaded microparticles was about 7-9% and the encapsulation efficiency of PTX loaded microparticles was about 18-23%. Flow cytometry and confocal laser scanning microscope analyses revealed that fluorescein isothiocyanate labeled FA conjugated microparticles presented significantly higher cellular uptake than FA-free group due to the FA-receptor-mediated endocytosis. In vitro cytotoxicity evaluation indicated that FA-PEG-PLLA expressed negligible cytotoxicity to mouse fibroblasts L929 cells. Moreover, PTX/FA-PEG-PLLA microparticles exhibited much higher anti-cancer efficacy than PTX/PEG-PLLA microparticles against human ovarian cancer SKOV3 cells. Nude mice xenografted with SKOV3 cells were used in biodistribution studies, the results indicated that an increased amount of PTX was accumulated in the tumor tissue deal with PTX/FA-PEG-PLLA microparticles. These results collectively suggested that PTX/FA-PEG-PLLA microparticles prepared by SEDS would have potential in anti-tumor applications as a tumor-targeted drug delivery formulation.

Aminated β-Cyclodextrin-Modified-Carboxylated Magnetic Cobalt/Nanocellulose Composite for Tumor-Targeted Gene Delivery

Gene therapy is a new kind of medicine, which uses genes as drugs in order to treat life threatening diseases. In the present work, a nonviral vector, aminated β-cyclodextrin-modified-carboxylated magnetic cobalt/nanocellulose composite (ACDC-Co/NCC), was synthesized for efficient transfection of genes into tumour cells. The synthesized ACDC-Co/NCC was characterized by means of FTIR, XRD, SEM, and ESR techniques. DNA condensing ability of ACDC-Co/NCC was found to be increased with increase in amount of ACDC-Co/NCC and 84.9% of DNA (1.0 μg/mL) inclusion was observed with 6.0 μg/mL of ACDC-Co/NCC. The cytotoxicity of ACDC-Co/NCC was observed to be minimal, even at higher concentration, with respect to the model transfecting agent, poly(ethyleneimine) (PEI). 88.2% of the gene was transfected at high dose of DNA, as indicated by the highest luciferase expression. These results indicated that ACDC-Co/NCC might be a promising candidate for gene delivery with the characteristics of good biocompatibility, potential biodegradability, minimal cytotoxicity, and relatively high gene transfection efficiency.

Minicircle DNA vectors for gene therapy: advances and applications

INTRODUCTION

Nucleic-acid-based biopharmaceuticals enclose a remarkable potential for treating debilitating or life-threatening diseases that currently remain incurable. This promising area of research envisages the creation of state-of-the-art DNA vaccines, pluripotent cells or gene-based therapies, which can be used to overcome current issues. To achieve this goal, DNA minicircles are emerging as ideal nonviral vectors due to their safety and persistent transgene expression in either quiescent or actively dividing cells.

AREAS COVERED

This review focuses on the characteristics of minicircle DNA (mcDNA) technology and the current advances in their production. The possible modifications to further improve minicircle efficacy are also emphasized and discussed in light of recent advances. As a final point, the main therapeutic applications of mcDNA are summarized, with a special focus on pluripotent stem cells production and cancer therapy.

EXPERT OPINION

Achieving in-target and persistent transgene expression is a challenging issue that is of critical importance for a successful therapeutic outcome. The use of miniaturized mcDNA cassettes with additional modifications that increase and prolong expression may contribute to an improved generation of biopharmaceuticals. The unique features of mcDNA render it an attractive alternative to overcome current technical issues and to bridge the significant gap that exists between basic research and clinical applications.

Divalent folate modification on PEG: an effective strategy for improving the cellular uptake and targetability of PEGylated polyamidoamine-polyethylenimine copolymer

The stability and targeting ability of nanocarrier gene delivery systems are necessary conditions to ensure the good therapeutic effect and low nonspecific toxicity of cancer treatment. Poly(ethylene glycol) (PEG) has been widely applied for improving stability and as a spacer for linking ligands and nanocarriers to improve targetability. However, the cellular uptake and endosomal escape capacity of nanocarriers has been seriously harmed due to the introduction of PEG. In the present study, we synthesized a new gene delivery vector by coupling divalent folate-PEG (PEG3.4k-FA2) onto polyamidoamine-polyethylenimine (PME) copolymer (PME-(PEG3.4k-FA2)1.72). Both PEG and monovalent folate-PEG (PEG3.4k-FA1) modified PME were prepared as control polymers, which were named as PME-(PEG3.5k)1.69 and PME-(PEG3.4k-FA1)1.66, respectively. PME-(PEG3.4k-FA2)1.72 exhibited strong DNA condensation capacity like parent polymer PME which was not significantly influenced by PEG. PME-(PEG3.4k-FA2)1.72/DNA complexes at N/P = 10 had a diameter ∼143 nm and zeta potential ∼13 mV and showed the lowest cytotoxicity and hemolysis and the highest transfection efficiency among all tested polymers. In folate receptor positive (FR-positive) cells, the cellular uptake and transfection efficiency were increased with the increase in the number of folates coupled on PEG; the order was PME-(PEG3.4k-FA2)1.72 > PME-(PEG3.4k-FA1)1.66 > PME-(PEG3.5k)1.69. Folate competition assays showed that PME-(PEG3.4k-FA2)1.72 complexes had stronger targeting ability than PME-(PEG3.5k)1.69 and PME-(PEG3.4k-FA1)1.66 complexes due to their higher folate density per PEG molecule. Cellular uptake mechanism study showed that the folate density on PEG could change the endocytosis pathway of PME-(PEG3.5k)1.69 from clathrin-mediated endocytosis to caveolae-mediated endocytosis, leading to less lysosomal degradation. Distribution and uptake in 3D multicellular spheroid assays showed that divalent folate could offer PME-(PEG3.4k-FA2)1.72 complexes stronger penetrating ability and higher cellular uptake. With these advantages, PME-(PEG3.4k-FA2)1.72 may be a promising nonviral vector candidate for efficient gene delivery. This study also indicates that divalent folate modification on PEG can serve as an efficient strategy to improve the cellular uptake and targeting ability of PEGylated cationic polymers for gene delivery.

A new version of targeted minicircle producer system for EBV-positive human nasopharyngeal carcinoma

Targeted gene therapy needs to be implemented for future therapies to ensure efficient activity at the site of patient primary tumors or metastases without causing intolerable side-effects. One of the elements of gene therapy is vector, which includes viral and non-viral vector. In the present study, we constructed a novel non-viral targeted gene therapeutic system by using the new minicircle (MC) producing plasmid for Epstein-Barr virus (EBV)-positive nasopharyngeal carcinoma (NPC). Molecular cloning technique was used to construct plasmids and electrophoretic analysis. Dual-luciferase reporter assay was used to evaluate the expression of luciferase. Fluorescence microscope was used to detect the expression of enhanced green fluorescence protein (EGFP). We constructed a new MC producing system pMC.BESPX-origin of plasmid replication (oriP), and demonstrated that this system could produce highly purified MC-oriP. Furthermore, our results showed that MC-oriP vector produced by the new system could mediate targeted luciferase gene expression in EBV-positive NPC cells. In addition, we verified that MC could mediate enhanced transgene expression compared with parent plasmid through EGFP transfection. The present study constructed a targeted expression vector pMC.BESPX-oriP which could carry diversified therapeutic genes for EBV-positive NPC and provides a new approach for MC-based therapies.

Folate-targeted multifunctional amino acid-chitosan nanoparticles for improved cancer therapy

PURPOSE

Tumor targeting nanomaterials have potential for improving the efficiency of anti-tumoral therapeutics. However, the evaluation of their biological performance remains highly challenging. In this study we describe the synthesis of multifunctional nanoparticles decorated with folic acid-PEG and dual amino acid-modified chitosan (CM-PFA) complexed with DNA and their evaluation in organotypic 2D co-cultures of cancer-normal cells and also on 3D multicellular tumor spheroids models.

METHODS

The physicochemical characterization of CM-PFA multifunctional carriers was performed by FTIR, (1)H NMR and DLS. 2D co-culture models were established by using a 1:2 cancer-to-normal cell ratio. 3D organotypic tumor spheroids were assembled using micromolding technology for high throughput screening. Nanoparticle efficiency was evaluated by flow cytometry and confocal microscopy.

RESULTS

The CM-PFA nanocarriers (126-176 nm) showed hemocompatibility and were internalized by target cells, achieving a 3.7 fold increase in gene expression. In vivo-mimicking 2D co-cultures confirmed a real affinity towards cancer cells and a negligible uptake in normal cells. The targeted nanoparticles penetrated into 3D spheroids to a higher extent than non-targeted nanocarriers. Also, CM-PFA-mediated delivery of p53 tumor suppressor promoted a decrease in tumor-spheroids volume.

CONCLUSION

These findings corroborate the improved efficiency of this delivery system and demonstrate its potential for application in cancer therapy.

Comparative analysis of enzymatically produced novel linear DNA constructs with plasmids for use as DNA vaccines

The use of DNA to deliver vaccine antigens offers many advantages, including ease of manufacture and cost. However, most DNA vaccines are plasmids and must be grown in bacterial culture, necessitating elements which are either unnecessary for effective gene delivery (e.g. bacterial origins of replication) or undesirable (e.g. antibiotic resistance genes). Removing these elements may improve the safety profile of DNA for the delivery of vaccines. Here we describe a novel, double-stranded, linear DNA construct produced by an enzymatic process that solely encodes an antigen expression cassette, comprising antigen, promoter, polyA tail and telomeric ends. We compared these constructs (called ‘Doggybones’ because of their shape) with conventional plasmid DNA. Using luciferase-expressing constructs, we demonstrated that expression levels were equivalent between Doggybones and plasmids both in vitro and in vivo. When mice were immunized with DNA constructs expressing the HIV envelope protein gp140, equivalent humoral and cellular responses were induced. Immunizations with either construct type expressing haemagluttinin were protective against H1N1 influenza challenge. This is the first example of an effective DNA vaccine which can be produced on a large scale by enzymatic processes.

Amphiphilic polyethylenimine (PEI) as highly efficient non-viral gene carrier

Efficient and safe gene vectors are important for gene therapy. Here, a novel family of amphiphilic polyethylenimine (PEI) LD1-PEI bearing a polar group of branched PEI 25K and four dodecyl chains was developed. Agarose gel electrophoresis was used to confirm the formation of complexes. The transfection activity of the amphiphilic carrier was evaluated in different cell lines. The in vitro study showed that LD1-PEI showed a higher transfection efficiency with improved biocompatibility than PEI 25K. Serum showed almost no or only a slight effect on LD1-PEI/DNA transfection efficiency. In summary, LD1-PEI is a promising nonviral gene carrier.

Galactosylated biodegradable poly(ε-caprolactone-co-phosphoester) random copolymer nanoparticles for potent hepatoma-targeting delivery of doxorubicin

A novel biocompatible and biodegradable poly(ε-caprolactone-co-phosphoester) random copolymer conjugated with galactosamine has been synthesized and used for hepatoma-targeting delivery of doxorubicin.

Inositol based non-viral vectors for transgene expression in human cervical carcinoma and hepatoma cell lines

Myo-Inositol (INO) is a biomolecule with crucial functions in many aspects. In this study, hyperbranched copolymers for gene delivery were synthesized based on inositol and low molecular weight polyethylenimine. The capacity of INO-PEIs to load plasmid DNA and their biocompatibility was demonstrated. A tumor target ligand, folic acid (FA), which was widely used for drug delivery systems, was subsequently conjugated to INO-PEIs and resulted in INO-PEI-FA copolymers. The polymers were then evaluated on their activity to mediate transgene expression in mammalian cell lines. As indicated, INO-PEIs were able to mediate efficient transgene expression, which was particularly noticeable in carcinoma cell line HeLa. INO-PEI-FA further improved the efficiency in HepG2. Distribution of INO-PEI-FA polymers in non-carcinoma NIH 3T3 and carcinoma HeLa cell lines was discussed.

Rigid nanoparticle-based delivery of anti-cancer siRNA: challenges and opportunities

Gene therapy is a promising strategy to treat various genetic and acquired diseases. Small interfering RNA (siRNA) is a revolutionary tool for gene therapy and the analysis of gene function. However, the development of a safe, efficient, and targetable non-viral siRNA delivery system remains a major challenge in gene therapy. An ideal delivery system should be able to encapsulate and protect the siRNA cargo from serum proteins, exhibit target tissue and cell specificity, penetrate the cell membrane, and release its cargo in the desired intracellular compartment. Nanomedicine has the potential to deal with these challenges faced by siRNA delivery. The unique characteristics of rigid nanoparticles mostly inorganic nanoparticles and allotropes of carbon nanomaterials, including high surface area, facile surface modification, controllable size, and excellent magnetic/optical/electrical properties, make them promising candidates for targeted siRNA delivery. In this review, recent progresses on rigid nanoparticle-based siRNA delivery systems will be summarized.

Photothermally triggered cytosolic drug delivery via endosome disruption using a functionalized reduced graphene oxide

Graphene oxide has unique physiochemical properties, showing great potential in biomedical applications. In the present work, functionalized reduced graphene oxide (PEG-BPEI-rGO) has been developed as a nanotemplate for photothermally triggered cytosolic drug delivery by inducing endosomal disruption and subsequent drug release. PEG-BPEI-rGO has the ability to load a greater amount of doxorubicin (DOX) than unreduced PEG-BPEI-GO via π-π and hydrophobic interactions, showing high water stability. Loaded DOX could be efficiently released by glutathione (GSH) and the photothermal effect of irradiated near IR (NIR) in test tubes as well as in cells. Importantly, PEG-BPEI-rGO/DOX complex was found to escape from endosomes after cellular uptake by photothermally induced endosomal disruption and the proton sponge effect, followed by GSH-induced DOX release into the cytosol. Finally, it was concluded that a greater cancer cell death efficacy was observed in PEG-BPEI-rGO/DOX complex-treated cells with NIR irradiation than those with no irradiation. This study demonstrated the development of the potential of a PEG-BPEI-rGO nanocarrier by photothermally triggered cytosolic drug delivery via endosomal disruption.

Strategies on the nuclear-targeted delivery of genes

To improve the nuclear-targeted delivery of non-viral vectors, extensive effort has been carried out on the development of smart vectors which could overcome multiple barriers. The nuclear envelope presents a major barrier to transgene delivery. Viruses are capable of crossing the nuclear envelope to efficiently deliver their genome into the nucleus through the specialized protein components. However, non-viral vectors are preferred over viral ones because of the safety concerns associated with the latter. Non-viral delivery systems have been designed to include various types of components to enable nuclear translocation at the periphery of the nucleus. This review summarizes the progress of research regarding nuclear transport mechanisms. "Smart" non-viral vectors that have been modified by peptides and other small molecules are able to facilitate the nuclear translocation and enhance the efficacy of gene expression. The resulting technology may also enhance delivery of other macromolecules to the nucleus.

Synthesis and in vitro studies of gold nanoparticles loaded with docetaxel

The aim of these studies was to synthesize, characterize and evaluate the efficacy of pegylated gold nanoparticles (AuNPs) that differed in their PEG molecular weight, using PEG 550 and PEG 2000. The synthesis of the gold nanoparticles was carried out by modified Brust method with a diameter of 4-15 nm. The targeting agent folic acid was introduced by the covalent linkage. Finally, the anti-cancer drug docetaxel was encapsulated by the AuNPs by non covalent adsorption. The nanoparticles were characterized by transmission electron microscopy and used for in vitro studies against a hormone-responsive prostate cancer cell line, LnCaP. The loaded nanoparticles reduced the cell viability in more than 50% at concentrations of 6 nM and above after 144 h of treatment. Moreover, observation of prostate cancer cells by optical microscopy showed damage to the cells after exposure to drug-loaded AuNPs while unloaded AuNPs had much less effect.

Novel polyethylenimine-derived nanoparticles for in vivo gene delivery

INTRODUCTION

Branched and linear polyethylenimines (PEIs) are cationic polymers that have been used to deliver nucleic acids both in vitro and in vivo. Owing to the high cationic charge, the branched polymers exhibit high transfection efficiency, and particularly PEI of molecular weight 25 kDa is considered as a gold standard in gene delivery. These polymers have been extensively studied and modified with different ligands so as to achieve the targeted delivery.

AREAS COVERED

The application of PEI in vivo promises to take the polymer-based vector to the next level wherein it can undergo clinical trials and subsequently could be used for delivery of therapeutics in humans. This review focuses on the various recent developments that have been made in the field of PEI-based delivery vectors for delivery of therapeutics in vivo.

EXPERT OPINION

The efficacy of PEI-based delivery vectors in vivo is significantly high and animal studies demonstrate that such systems have a potential in humans. However, we feel that though PEI is a promising vector, further studies involving PEI in animal models are needed so as to get a detailed toxicity profile of these vectors. Also, it is imperative that the vector reaches the specific organ causing little or no undesirable effects to other organs.

Gene carrier showing all-or-none response to cancer cell signaling

In this work we designed a novel nano carrier, a linear polyethylenimine (LPEI)-peptide conjugate, for cancer-specific expression of transgenes. The conjugate was easily synthesized by using a click chemistry scheme orthogonal to the reactive side groups of the peptide, which is the substrate of protein kinase Cα (PKCα). Polyplexes of the conjugates with plasmid DNA (pDNA) were intact and stably dispersed even in the presence of cell lysate. Despite this stability, the polyplexes readily dissociated upon phosphorylation of the grafted peptides by PKCα. Because of its endosomal escape ability and adequate susceptibility to PKCα, the polyplexes showed an all-or-none type response to PKCα activity in transgene expression in vitro. The polyplexes achieved cancer tissue-specific transgene expression even for a tumor with a relatively low PKCα activity. Thus the LPEI-peptide conjugate has high potential as a nanocarrier for cancer-targeted gene therapy.