Delivering the goods: viral and non-viral gene therapy systems and the inherent limits on cargo DNA and internal sequences

Recent advances in carbon quantum dots for gene delivery: A comprehensive review

Gene therapy is a revolutionary technology in healthcare that provides novel therapeutic options and has immense potential in addressing genetic illnesses, malignancies, and viral infections. Nevertheless, other obstacles still need to be addressed regarding safety, ethical implications, and technological enhancement. Nanotechnology and gene therapy fields have shown significant promise in transforming medical treatments by improving accuracy, effectiveness, and personalization. This review assesses the possible uses of gene therapy, its obstacles, and future research areas, specifically emphasizing the creative combination of gene therapy and nanotechnology. Nanotechnology is essential for gene delivery as it allows for the development of nano-scale carriers, such as carbon quantum dots (CQDs), which may effectively transport therapeutic genes into specific cells. CQDs exhibit distinctive physicochemical characteristics such as small size, excellent stability, and minimal toxicity, which render them highly favorable for gene therapy applications. The objective of this study is to review and describe the current advancements in the utilization of CQDs for gene delivery. Additionally, it intends to assess existing research, explore novel applications, and identify future opportunities and obstacles. This study offers a thorough summary of the current state and future possibilities of using CQDs for gene delivery. Combining recent research findings highlights the potential of CQDs to revolutionize gene therapy and its delivery methods.

Viscosity-aided electromechanical poration of cells for transfecting molecules

Cell poration technologies offer opportunities not only to understand the activities of biological molecules but also to investigate genetic manipulation possibilities. Unfortunately, transferring large molecules that can carry huge genomic information is challenging. Here, we demonstrate electromechanical poration using a core-shell-structured microbubble generator, consisting of a fine microelectrode covered with a dielectric material. By introducing a microcavity at its tip, we could concentrate the electrical field with the application of electric pulses and generate microbubbles for electromechanical stimulation of cells. Specifically, the technology enables transfection with molecules that are thousands of kDa even into osteoblasts and Chlamydomonas, which are generally considered to be difficult to inject. Notably, we found that the transfection efficiency can be enhanced by adjusting the viscosity of the cell suspension, which was presumably achieved by remodeling of the membrane cytoskeleton. The applicability of the approach to a variety of cell types opens up numerous emerging gene engineering applications.

A Quality by Design Approach in Pharmaceutical Development of Non-Viral Vectors with a Focus on miRNA

Cancer is the leading cause of death worldwide. Tumors consist of heterogeneous cell populations that have different biological properties. While conventional cancer therapy such as chemotherapy, radiotherapy, and surgery does not target cancer cells specifically, gene therapy is attracting increasing attention as an alternative capable of overcoming these limitations. With the advent of gene therapy, there is increasing interest in developing non-viral vectors for genetic material delivery in cancer therapy. Nanosystems, both organic and inorganic, are the most common non-viral vectors used in gene therapy. The most used organic vectors are polymeric and lipid-based delivery systems. These nanostructures are designed to bind and protect the genetic material, leading to high efficiency, prolonged gene expression, and low toxicity. Quality by Design (QbD) is a step-by-step approach that investigates all the factors that may affect the quality of the final product, leading to efficient pharmaceutical development. This paper aims to provide a new perspective regarding the use of the QbD approach for improving the quality of non-viral vectors for genetic material delivery and their application in cancer therapy.

Nanomedicines for Endometriosis: Lessons Learned from Cancer Research

Endometriosis is an incurable gynecological disease characterized by the abnormal growth of endometrium-like tissue, characteristic of the uterine lining, outside of the uterine cavity. Millions of people with endometriosis suffer from pelvic pain and infertility. This review aims to discuss whether nanomedicines that are promising therapeutic approaches for various diseases have the potential to create a paradigm shift in endometriosis management. For the first time, the available reports and achievements in the field of endometriosis nanomedicine are critically evaluated, and a summary of how nanoparticle-based systems can improve endometriosis treatment and diagnosis is provided. Parallels between cancer and endometriosis are also drawn to understand whether some fundamental principles of the well-established cancer nanomedicine field can be adopted for the development of novel nanoparticle-based strategies for endometriosis. This review provides the state of the art of endometriosis nanomedicine and perspective for researchers aiming to realize and exploit the full potential of nanoparticles for treatment and imaging of the disorder.

Carbon nanotube-delivered iC9 suicide gene therapy for killing breast cancer cells in vitro

AIM

To induce a safe death to MCF-7 human breast cancer cell line through gene therapy based on iC9 suicide gene.

MATERIALS & METHODS

To induce apoptosis to MCF-7 cell line, iC9 gene was transfected using pyridine-functionalized multi-walled carbon nanotubes. Then, to enhance chemotherapy, iC9 suicide gene therapy was performed alongside.

RESULTS

The results show that the MCF-7 cells were efficiently eliminated in a high percentage by this approach. Furthermore, the suicide gene by itself/in combination with the chemotherapeutic drugs managed to pass the cell cycle arrests.

CONCLUSION

We introduced an in vitro treatment approach based on suicide gene therapy and the first step was taken toward the enhancement of chemotherapy, although more investigation is required.

Synthesis of Cationic Polymer Libraries for Gene Delivery Using Diglycidyl Ethers

Gene therapy has the potential to cure many different genetic diseases, if safe and effective gene delivery vectors can be developed. This chapter describes protocols for the synthesis of novel polymers using diglycidyl ether and diamine or polyamine monomers for transgene delivery and expression. The resulting poly (amino ethers) are able to transfect a higher number of cells, with lower cytotoxicity than other commercially available polymers (e.g., Polyethyleneimine, PEI).

Copolymer micelles function as pH-responsive nanocarriers to enhance the cytotoxicity of a HER2 aptamer in HER2-positive breast cancer cells

Efficient delivery of nucleic acids into target cells is crucial for nucleic acid-based therapies. Various nucleic acid delivery systems have been developed, each with its own advantages and limitations. We previously developed a nanoparticle-based delivery system for small chemical drugs using pH-responsive PEG₈-PDPA₁₀₀-PEG₈ polymer micelles as carriers. In this study, we extend the application of these pH-responsive micelle-like nanoparticles (MNPs) to deliver oligonucleotides. We demonstrate that the MNPs efficiently encapsulate and deliver oligonucleotides of different lengths (20-100 nt) into cells. The cargo oligonucleotides are rapidly released at pH 5.0. We prepared MNPs carrying a Texas red-fluorescently labeled anti-human epidermal growth factor receptor 2 (HER2) aptamer (HApt). Compared to free HApt, the HApt-MNPs resulted in significantly better cellular uptake, reduced cell viability, and increased apoptosis in SKBR3 breast cancer cells, which overexpress HER2. Moreover, HApt-MNPs were significantly less cytotoxic to MCF7 breast cancer cells, which express low levels of HER2. After cellular uptake, HApt-MNPs mainly accumulated in lysosomes; inhibition of lysosomal activity using bafilomycin A1 and LysoTracker Red staining confirmed that lysosomal activity and low pH were required for HApt-MNP accumulation and release. Furthermore, HER2 protein expression declined significantly following treatment with HApt-MNPs in SKBR3 cells, indicating that HApt-induced translocation of HER2 to lysosomes exerted a potent cytotoxic effect by altering signaling downstream of HER2. In conclusion, this pH-responsive and lysosome-targeting nanoparticle system can efficiently deliver oligonucleotides to specific target cells and has significant potential for nucleic acid-based cancer therapies.

Direct reprogramming of mouse fibroblasts into neural cells via Porphyra yezoensis polysaccharide based high efficient gene co-delivery

BACKGROUND

The cell source for transplantation therapy is always a prerequisite question to be solved in clinical applications. Neural cells are considered non-regenerable, which highly restrict their application in the treatment for nerve injury. Therefore, neural trans-differentiation based on gene transfection provides a new solution to this issue. Compared to viral strategy, non-viral gene delivery systems are considered as a more promising way to achieve this aim. This study centers on a novel application of Porphyra yezoensis polysaccharide as a non-viral gene carrier for the neural trans-differentiation of mouse fibroblasts.

RESULTS

Ethanediamine modified P. yezoensis polysaccharide (Ed-PYP) served as a gene carrier and a group of plasmids that encode Ascl1, Brn4, and Tcf3 (pABT) self-assembled into nanoparticles. Results demonstrated that Ed-PYP-pABT nanoparticles at Ed-PYP: pABT weight ratio of 40:1 was the optimal candidate for gene delivery. ELISA assay revealed the highest expression levels of NGF, BDNF and SHH at 14 days after last transfection. Immunofluorescence and western blot assays also showed robust expression of neural markers including Nestin, GFAP, β-3tubulin, NF200, GAP43 and MAP2, in induced 3T6 cells at this time point.

CONCLUSION

Overall, these findings indicated that the P. yezoensis polysaccharide-based non-viral gene co-delivery system is a promising strategy for the generation of neural cells, which might facilitate the developments in the recovery of neural injuries.

Delivering Nucleic-Acid Based Nanomedicines on Biomaterial Scaffolds for Orthopedic Tissue Repair: Challenges, Progress and Future Perspectives

As well as acting to fill defects and allow for cell infiltration and proliferation in regenerative medicine, biomaterial scaffolds can also act as carriers for therapeutics, further enhancing their efficacy. Drug and protein delivery on scaffolds have shown potential, however, supraphysiological quantities of therapeutic are often released at the defect site, causing off-target side effects and cytotoxicity. Gene therapy involves the introduction of foreign genes into a cell in order to exert an effect; either replacing a missing gene or modulating expression of a protein. State of the art gene therapy also encompasses manipulation of the transcriptome by harnessing RNA interference (RNAi) therapy. The delivery of nucleic acid nanomedicines on biomaterial scaffolds - gene-activated scaffolds -has shown potential for use in a variety of tissue engineering applications, but as of yet, have not reached clinical use. The current state of the art in terms of biomaterial scaffolds and delivery vector materials for gene therapy is reviewed, and the limitations of current procedures discussed. Future directions in the clinical translation of gene-activated scaffolds are also considered, with a particular focus on bone and cartilage tissue regeneration.

Targeting tumor suppressor genes for cancer therapy

Cancer drugs are broadly classified into two categories: cytotoxic chemotherapies and targeted therapies that specifically modulate the activity of one or more proteins involved in cancer. Major advances have been achieved in targeted cancer therapies in the past few decades, which is ascribed to the increasing understanding of molecular mechanisms for cancer initiation and progression. Consequently, monoclonal antibodies and small molecules have been developed to interfere with a specific molecular oncogenic target. Targeting gain-of-function mutations, in general, has been productive. However, it has been a major challenge to use standard pharmacologic approaches to target loss-of-function mutations of tumor suppressor genes. Novel approaches, including synthetic lethality and collateral vulnerability screens, are now being developed to target gene defects in p53, PTEN, and BRCA1/2. Here, we review and summarize the recent findings in cancer genomics, drug development, and molecular cancer biology, which show promise in targeting tumor suppressors in cancer therapeutics.

DNA-binding-domain fusions enhance the targeting range and precision of Cas9

The CRISPR-Cas9 system is commonly used in biomedical research; however, the precision of Cas9 is suboptimal for applications that involve editing a large population of cells (for example, gene therapy). Variations on the standard Cas9 system have yielded improvements in the precision of targeted DNA cleavage, but they often restrict the range of targetable sequences. It remains unclear whether these variants can limit lesions to a single site in the human genome over a large cohort of treated cells. Here we show that by fusing a programmable DNA-binding domain (pDBD) to Cas9 and attenuating Cas9's inherent DNA-binding affinity, we were able to produce a Cas9-pDBD chimera with dramatically improved precision and an increased targeting range. Because the specificity and affinity of this framework can be easily tuned, Cas9-pDBDs provide a flexible system that can be tailored to achieve extremely precise genome editing at nearly any genomic locus.

Efficient gene delivery to human umbilical cord mesenchymal stem cells by cationized Porphyra yezoensis polysaccharide nanoparticles

This study centered on an innovative application of Porphyra yezoensis polysaccharide (PPS) with cationic modification as a safe and efficient nonviral gene vector to deliver a plasmid encoding human Wnt3a (pWnt3a) into human umbilical cord mesenchymal stem cells (HUMSCs). After modification with branched low-molecular-weight (1,200 Da) polyethylenimine, the cationized PPS (CPPS) was combined with pWnt3a to form spherical nanoscale particles (CPPS-pWnt3a nanoparticles). Particle size and distribution indicated that the CPPS-pWnt3a nanoparticles at a CPPS:pWnt3a weight ratio of 40:1 might be a potential candidate for DNA plasmid transfection. A cytotoxicity assay demonstrated that the nanoparticles prepared at a CPPS:pWnt3a weight ratio of 40:1 were nontoxic to HUMSCs compared to those of Lipofectamine 2000 and polyethylenimine (25 kDa). These nanoparticles were further transfected to HUMSCs. Western blotting demonstrated that the nanoparticles (CPPS:pWnt3a weight ratio 40:1) had the greatest transfection efficiency in HUMSCs, which was significantly higher than that of Lipofectamine 2000; however, when the CPPS:pWnt3a weight ratio was increased to 80:1, the nanoparticle-treated group showed no obvious improvement in translation efficiency over Lipofectamine 2000. Therefore, CPPS, a novel cationic polysaccharide derived from P. yezoensis, could be developed into a safe, efficient, nonviral gene vector in a gene-delivery system.

Carbon nanotubes part II: a remarkable carrier for drug and gene delivery

INTRODUCTION

Carbon nanotubes (CNT) have recently been studied as novel and versatile drug and gene delivery vehicles. When CNT are suitably functionalized, they can interact with various cell types and are taken up by endocytosis.

AREAS COVERED

Anti-cancer drugs cisplatin and doxorubicin have been delivered by CNT, as well as methotrexate, taxol and gemcitabine. The delivery of the antifungal compound amphotericin B and the oral administration of erythropoietin have both been assisted using CNT. Frequently, targeting moieties such as folic acid, epidermal growth factor or various antibodies are attached to the CNT-drug nanovehicle. Different kinds of functionalization (e.g., polycations) have been used to allow CNT to act as gene delivery vectors. Plasmid DNA, small interfering RNA and micro-RNA have all been delivered by CNT vehicles. Significant concerns are raised about the nanotoxicology of the CNT and their potentially damaging effects on the environment.

EXPERT OPINION

CNT-mediated drug delivery has been studied for over a decade, and both in vitro and in vivo studies have been reported. The future success of CNTs as vectors in vivo and in clinical application will depend on achievement of efficacious therapy with minimal adverse effects and avoidance of possible toxic and environmentally damaging effects.

Synthetic biology in cell-based cancer immunotherapy

The adoptive transfer of genetically engineered T cells with cancer-targeting receptors has shown tremendous promise for eradicating tumors in clinical trials. This form of cellular immunotherapy presents a unique opportunity to incorporate advanced systems and synthetic biology approaches to create cancer therapeutics with novel functions. We first review the development of synthetic receptors, switches, and circuits to control the location, duration, and strength of T cell activity against tumors. In addition, we discuss the cellular engineering and genome editing of host cells (or the chassis) to improve the efficacy of cell-based cancer therapeutics, and to reduce the time and cost of manufacturing.

Transfection system of amino-functionalized calcium phosphate nanoparticles: in vitro efficacy, biodegradability, and immunogenicity study

Many methods have been developed in order to use calcium phosphate (CaP) for delivering nucleotides into living cells. Surface functionalization of CaP nanoparticles (CaP NPs) with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was shown recently to achieve dispersed NPs with a positive surface charge, capable of transfection (Chem. Mater. 2013, 25 (18), 3667). In this study, different crystal structures of amino-modified CaP NPs (brushite and hydroxyapatite) were investigated for their interaction in cell culture systems in more detail. Qualitative (confocal laser scanning microscopy) and quantitative (flow cytometry) transfection experiments with two cell lines showed the higher transfection efficacy of brushite versus hydroxyapatite. The transfection also revealed a cell type dependency. HEK293 cells were easier to transfect compared to A549 cells. This result was supported by the cytotoxicity results. A549 cells showed a higher degree of tolerance toward the CaP NPs. Further, the impact of the surface modification on the interaction with macrophages and complement as two important components of the innate immune system were considered. The amine surface functionalization had an effect of decreasing the release of proinflammatory cytokines. The complement interaction investigated by a C3a complement activation assay did show no significant differences between CaP NPs without or with amine modification and overall weak interaction. Finally, the degradation of CaP NPs in biological media was studied with respect to the two crystal structures and at acidic and neutral pH. Both amino-modified CaP NPs disintegrate within days at neutral pH, with a notable faster disintegration of brushite NPs at acidic pH. In summary, the fair transfection capability of this amino functionalized CaP NPs together with the excellent biocompatibility, biodegradability, and low immunogenicity make them interesting candidates for further evaluation.

Tumor-targeting bacterial therapy: A potential treatment for oral cancer (Review)

Certain obligate or facultative anaerobic bacteria, which exhibit an inherent ability to colonize solid tumors in vivo, may be used in tumor targeting. As genetically manipulated bacteria may actively and specifically penetrate into the tumor tissue, bacterial therapy is becoming a promising approach in the treatment of tumors. However, to the best of our knowledge, no reports have been published thus far regarding the bacterial treatment of oral cancer, one of the most common types of cancer worldwide. In this review, the progress in the understanding of bacterial strategies used in tumor-targeted therapy is discussed and particular bacterial strains that may have great therapeutic potential in oral squamous cell carcinoma (OSCC) tumor-targeted therapy are predicted as determined by previous studies.

The development and assessment of high-throughput mass spectrometry-based methods for the quantification of a nanoparticle drug delivery agent in cellular lysate

The safe use of lipid-based drug delivery agents requires fast and sensitive qualitative and quantitative assessment of their cellular interactions. Many mass spectrometry (MS) based analytical platforms can achieve such task with varying capabilities. Therefore, four novel high-throughput MS-based quantitative methods were evaluated for the analysis of a small organic gene delivery agent: N,N-bis(dimethylhexadecyl)-1,3-propane-diammonium dibromide (G16-3). Analysis utilized MS instruments that detect analytes using low-resolution tandem MS (MS/MS) analysis (i.e. QTRAP or linear ion trap in this work) or high-resolution MS analysis (i.e. time of flight (ToF) or Orbitrap). Our results indicate that the validated fast chromatography (FC)-QTRAP-MS/MS, FC- LTQ-Orbitrap-MS, desorption electrospray ionization-collision-induced dissociation (CID)-MS/MS and matrix assisted laser desorption ionization-ToF/ToF-MS MS methods were superior in the area of method development and sample analysis time to a previously developed liquid chromatography (LC)-CID-MS/MS. To our knowledge, this is the first evaluation of the abilities of five MS-based quantitative methods that target a single pharmaceutical analyte. Our findings indicate that, in comparison to conventional LC-CID-MS/MS, the new MS-based methods resulted in a (1) substantial reduction in the analysis time, (2) reduction in the time required for method development and (3) production of either superior or comparable quantitative data. The four new high-throughput MS methods, therefore, were faster, more efficient and less expensive than a conventional LC-CID-MS/MS for the quantification of the G16-3 analyte within tissue culture. When applied to cellular lysate, no significant change in the concentration of G16-3 gemini surfactant within PAM212 cells was observed between 5 and 53 h, suggesting the absence of any metabolism/excretion from PAM212 cells.

The sustained-release behavior and in vitro and in vivo transfection of pEGFP-loaded core-shell-structured chitosan-based composite particles

Novel submicron core-shell-structured chitosan-based composite particles encapsulated with enhanced green fluorescent protein plasmids (pEGFP) were prepared by complex coacervation method. The core was pEGFP-loaded thiolated N-alkylated chitosan (TACS) and the shell was pH- and temperature-responsive hydroxybutyl chitosan (HBC). pEGFP-loaded TACS-HBC composite particles were spherical, and had a mean diameter of approximately 120 nm, as measured by transmission electron microscopy and particle size analyzer. pEGFP showed sustained release in vitro for >15 days. Furthermore, in vitro transfection in human embryonic kidney 293T and human cervix epithelial cells, and in vivo transfection in mice skeletal muscle of loaded pEGFP, were investigated. Results showed that the expression of loaded pEGFP, both in vitro and in vivo, was slow but could be sustained over a long period. pEGFP expression in mice skeletal muscle was sustained for >60 days. This work indicates that these submicron core-shell-structured chitosan-based composite particles could potentially be used as a gene vector for in vivo controlled gene transfection.

Overexpression of Jagged-1 combined with blockade of CD40 pathway prolongs allograft survival

Dendritic cells (DCs) have the tolerogenic potential to regulate adaptive immunity and induce allografts acceptance. Here we investigated whether blockade of the CD40 pathway could enhance the immune tolerance induced by DC2.4 cells modified to express Jagged-1 (JAG1-DC) in heart transplantation. Results showed that JAG1-DC treatment combined with anti-CD40L monoclonal antibody (mAb) administration significantly prolonged cardiac allograft survival in mice, with long-term survival (>110 days) of 50% of the allografts in the recipients. The therapy specifically inhibited the immune response, induced alloantigen-specific T-cell hyporesponsiveness, upregulated transforming growth factor-β synthesis and increased the population of regulatory T cells (Tregs) driven by Jagged-1-Notch activation. These results highlight the potential application of gene therapy to induce alloantigen-specific Tregs effectively by providing the Jagged-1 stimulation.

An assay to monitor the activity of DNA transposition complexes yields a general quality control measure for transpositional recombination reactions

Transposon-based technologies have many applications in molecular biology and can be used for gene delivery into prokaryotic and eukaryotic cells. Common transpositional activity measurement assays suitable for many types of transposons would be beneficial, as diverse transposon systems could be compared for their performance attributes. Therefore, we developed a general-purpose assay to enable and standardize the activity measurement for DNA transposition complexes (transpososomes), using phage Mu transposition as a test platform. This assay quantifies transpositional recombination efficiency and is based on an in vitro transposition reaction with a target plasmid carrying a lethal ccdB gene. If transposition targets ccdB, this gene becomes inactivated, enabling plasmid-receiving Escherichia coli cells to survive and to be scored as colonies on selection plates. The assay was validated with 3 mini-Mu transposons varying in size and differing in their marker gene constitution. Tests with different amounts of transposon DNA provided a linear response and yielded a 10-fold operational range for the assay. The colony formation capacity was linearly correlated with the competence status of the E.coli cells, enabling normalization of experimental data obtained with different batches of recipient cells. The developed assay can now be used to directly compare transpososome activities with all types of mini-Mu transposons, regardless of their aimed use. Furthermore, the assay should be directly applicable to other transposition-based systems with a functional in vitro reaction, and it provides a dependable quality control measure that previously has been lacking but is highly important for the evaluation of current and emerging transposon-based applications.

A chiral, low-cytotoxic [Ni15]-wheel complex

A new chiral [Ni15] complex with a Schiff-base ligand derived from o-vanillin and L-glutamic acid is presented, emphasizing the properties relevant for biology and materials science. The formation of the complex molecules in solution is confirmed by AFM and dynamic light scattering studies. The compound is weakly antiferromagnetic with considerable admixture of excited states, comprising negligibly interacting [Ni3] units. Studies of the interactions with two cell lines indicate low cytotoxicity.

Transferrin- and folate-modified, double-targeted nanocarriers for gene delivery

CONTEXT

Surface modification of nanocarriers with specific ligands defines a new biological identity, which assist in targeting and internalization of the nanocarriers to specific cell populations, such as cancers and disease organs.

OBJECTIVE

This study aimed to develop systemically administrable dual ligands modified nanocarriers, which could target the cells through receptor-mediated pathways to increase the nuclear uptake of genetic materials.

MATERIALS AND METHODS

In the present work, transferrin (Tf) and folate (Fa) were linked onto polyethylene glycol-phosphatidylethanolamine (PEG-PE) separately to get transferrin-PEG-PE (T-PEG-PE) and folate-PEG-PE (F-PEG-PE) ligands for the surface modification of carriers. The in vivo transfection efficiency of the novel dual ligands modified (D-modified) vectors were evaluated in tumor-bearing animal models.

RESULTS

D-Modified solid lipid nanoparticles/enhanced green fluorescence protein plasmid (D-SLN/pEGFP) has a particle size of 226 nm and a gene-loading quantity of 90%. D-SLN/pEGFP displayed over 30% higher transfection efficiency than unmodified SLN/pEGFP and single ligand modified particles in HepG2 cells.

CONCLUSION

It could be concluded that Tf and Fa could function as excellent active targeting ligands to improve the cell-targeting ability of the carriers and the resulting dual ligands modified vectors could be applied as a promising active targeting gene delivery system.

One to rule them all: A highly conserved motif in mariner transposase controls multiple steps of transposition

The development of transposon-based genome manipulation tools can benefit greatly from understanding transposons’ inherent regulatory mechanisms. The Tc1-mariner transposons, which are being widely used in biotechnological applications, are subject to a self-inhibitory mechanism whereby increasing transposase expression beyond a certain point decreases the rate of transposition. In a recent paper, Liu and Chalmers performed saturating mutagenesis on the highly conserved WVPHEL motif in the mariner-family transposase from the Hsmar1 element. Curiously, they found that the majority of all possible single mutations were hyperactive. Biochemical characterizations of the mutants revealed that the hyperactivity is due to a defect in communication between transposase subunits, which normally regulates transposition by reducing the rate of synapsis. This provides important clues for improving transposon-based tools. However, some WVPHEL mutants also showed features that would be undesirable for most biotechnological applications: they showed uncontrolled DNA cleavage activities and defects in the coordination of cleavage between the two transposon ends. The study illustrates how the knowledge of inhibitory mechanisms can help improve transposon tools but also highlights an important challenge, which is to specifically target a regulatory mechanism without affecting other important functions of the transposase.

Fabrication of piezoelectric components for a tunable and efficient device for DNA delivery into mammalian cells

We fabricated three piezoelectric components (PZT) that can produce ultrasonic waves with various generated power in order to improve the delivery of DNA molecule and polymer/DNA complexes into cells. Two cationic polymers (PEI and PDMAEMA) were interacted with DNA to form nano-scaled DNA/polymer complexes with/without the help of PZT devices. The application of PZT devices under optimal conditions helped to avoid cytotoxicity and greatly increased the transfection (DNA delivery) efficiency of these complexes in mammalian cells. The cytotoxicity and transfection efficiency were found to be correlated with the PZT-generated power, waveforms and duration of ultrasonic treatment. There was no observable cytotoxicity in our experimental models and, a maximum transfection efficiency 700% greater than that of polymer/DNA complexes without applying ultrasound was achieved. The transfection efficiency of plain polymer/DNA complexes (without PZT treatment) corresponded to a 630-fold increase in comparison to the naked DNA. The waveforms of generated ultrasound greatly influenced the transfection efficiency, while cytotoxicity was not significantly affected. This means that, for optimal DNA delivery, duration of the peak voltage (Vmax/Div) also plays a role. In addition, the generated waves from PZT do not cause dissociation of polymer/DNA complexes or a change in the particle sizes of these complexes. In conclusion, these results suggest that the operation of PZT devices can be a tunable/safe way to greatly improve DNA delivery for gene therapy.

piggyBac transposon plus insulators overcome epigenetic silencing to provide for stable signaling pathway reporter cell lines

Genetically modified hematopoietic progenitors represent an important testing platform for a variety of cell-based therapies, pharmaceuticals, diagnostics and other applications. Stable expression of a transfected gene of interest in the cells is often obstructed by its silencing. DNA transposons offer an attractive non-viral alternative of transgene integration into the host genome, but their broad applicability to leukocytes and other "transgene unfriendly" cells has not been fully demonstrated. Here we assess stability of piggyBac transposon-based reporter expression in murine prostate adenocarcinoma TRAMP-C2, human monocyte THP-1 and erythroleukemia K562 cell lines, along with macrophages and dendritic cells (DCs) that have differentiated from the THP-1 transfects. The most efficient and stable reporter activity was observed for combinations of the transposon inverted terminal repeats and one 5'- or two cHS4 core insulators flanking a green fluorescent protein reporter construct, with no detectable silencing over 10 months of continuous cell culture in absence of any selective pressure. In monocytic THP-1 cells, the functional activity of luciferase reporters for NF-κB, Nrf2, or HIF-1α has not decreased over time and was retained following differentiation into macrophages and DCs, as well. These results imply pB as a versatile tool for gene integration in monocytic cells in general, and as a convenient access route to DC-based signaling pathway reporters suitable for high-throughput assays, in particular.

Carbon nanotubes as vectors for gene therapy: past achievements, present challenges and future goals

Promising therapeutic and prophylactic effects have been achieved following advances in the gene therapy research arena, giving birth to the new generation of disease-modifying therapeutics. The greatest challenge that gene therapy vectors still face is the ability to deliver sufficient genetic payloads in order to enable efficient gene transfer into target cells. A wide variety of viral and non-viral gene therapy vectors have been developed and explored over the past 10years, including carbon nanotubes. In this review we will address the application of carbon nanotubes as non-viral vectors in gene therapy with the aim to give a perspective on the past achievements, present challenges and future goals. A series of important topics concerning carbon nanotubes as gene therapy vectors will be addressed, including the benefits that carbon nanotubes offer over other non-viral delivery systems. Furthermore, a perspective is given on what the ideal genetic cargo to deliver using carbon nanotubes is and finally the geno-pharmacological impact of carbon nanotube-mediated gene therapy is discussed.

Sleeping Beauty transposon system is a reliable gene delivery tool for hereditary tyrosinaemia type 1 disease gene therapy: size of the foreign gene decides the timing of stable integration into the host chromosomes

OBJECTIVE

This study investigated compensation for loss of the fumaryl-acetoacetate hydrolase gene (Fah) by gene therapy using the Sleeping Beauty transposon system (SBTS), in a hereditary tyrosinaemia type 1 (HT-1) mouse model (Fah-/-).

METHODS

Twenty Fah-/- study mice, five wild-type positive controls and five Fah-/- negative controls were included. All Fah-/- mice received 2-(2-nitro-4-trifluoro-methylbenzoyl)-1,3-cyclo hexaedione (NTBC). Fah-/- study mice were randomly injected with one of two SBTS constructs: Fah-SBTS (containing mouse Fah gene), or forkhead box M1b (FOXM1B)-Fah-SBTS (containing mouse Fah and human FOXM1B genes). Firefly luciferase-SBTS was injected as a trace marker. NTBC treatment stopped after construct injection; Fah-/- negative controls were kept healthy with continued NTBC. Mice were weighed daily; the luciferase signal was monitored by in vivo bioluminescence, and Fah and FOXM1B gene expression were evaluated.

RESULTS

The Fah gene integrated into the mouse chromosomes within 1 week of Fah-SBTS injection (mice survived without NTBC thereafter) and within 1 month of FOXM1B-Fah-SBTS injection (mice lost weight dramatically and needed additional NTBC).

CONCLUSION

The shorter Fah gene had an advantage over the longer FOXM1B-Fah gene for stable integration into the host mouse chromosomes.

Chitosan for gene delivery and orthopedic tissue engineering applications

Gene therapy involves the introduction of foreign genetic material into cells in order exert a therapeutic effect. The application of gene therapy to the field of orthopaedic tissue engineering is extremely promising as the controlled release of therapeutic proteins such as bone morphogenetic proteins have been shown to stimulate bone repair. However, there are a number of drawbacks associated with viral and synthetic non-viral gene delivery approaches. One natural polymer which has generated interest as a gene delivery vector is chitosan. Chitosan is biodegradable, biocompatible and non-toxic. Much of the appeal of chitosan is due to the presence of primary amine groups in its repeating units which become protonated in acidic conditions. This property makes it a promising candidate for non-viral gene delivery. Chitosan-based vectors have been shown to transfect a number of cell types including human embryonic kidney cells (HEK293) and human cervical cancer cells (HeLa). Aside from its use in gene delivery, chitosan possesses a range of properties that show promise in tissue engineering applications; it is biodegradable, biocompatible, has anti-bacterial activity, and, its cationic nature allows for electrostatic interaction with glycosaminoglycans and other proteoglycans. It can be used to make nano- and microparticles, sponges, gels, membranes and porous scaffolds. Chitosan has also been shown to enhance mineral deposition during osteogenic differentiation of MSCs in vitro. The purpose of this review is to critically discuss the use of chitosan as a gene delivery vector with emphasis on its application in orthopedic tissue engineering.

Identification of multiple binding sites for the THAP domain of the Galileo transposase in the long terminal inverted-repeats

Galileo is a DNA transposon responsible for the generation of several chromosomal inversions in Drosophila. In contrast to other members of the P-element superfamily, it has unusually long terminal inverted-repeats (TIRs) that resemble those of Foldback elements. To investigate the function of the long TIRs we derived consensus and ancestral sequences for the Galileo transposase in three species of Drosophilids. Following gene synthesis, we expressed and purified their constituent THAP domains and tested their binding activity towards the respective Galileo TIRs. DNase I footprinting located the most proximal DNA binding site about 70 bp from the transposon end. Using this sequence we identified further binding sites in the tandem repeats that are found within the long TIRs. This suggests that the synaptic complex between Galileo ends may be a complicated structure containing higher-order multimers of the transposase. We also attempted to reconstitute Galileo transposition in Drosophila embryos but no events were detected. Thus, although the limited numbers of Galileo copies in each genome were sufficient to provide functional consensus sequences for the THAP domains, they do not specify a fully active transposase. Since the THAP recognition sequence is short, and will occur many times in a large genome, it seems likely that the multiple binding sites within the long, internally repetitive, TIRs of Galileo and other Foldback-like elements may provide the transposase with its binding specificity.

piggyBac as a high-capacity transgenesis and gene-therapy vector in human cells and mice

The stable genomic integration and expression of a large transgene is a major hurdle in gene therapy. We show that the modified piggyBac (PB) transposon system can be used to introduce a 207 kb genomic DNA fragment containing the RORγ/γt locus into human cells and mice. PB-mediated transgenesis results in a single copy of a stably inherited and expressed transgene. These results indicate that PB could serve as an effective high-capacity vector for functional analysis of the mammalian genome and for gene therapy in human cells.

Striking structural dynamism and nucleotide sequence variation of the transposon Galileo in the genome of Drosophila mojavensis

Background

Galileo is a transposable element responsible for the generation of three chromosomal inversions in natural populations of Drosophila buzzatii. Although the most characteristic feature of Galileo is the long internally-repetitive terminal inverted repeats (TIRs), which resemble the Drosophila Foldback element, its transposase-coding sequence has led to its classification as a member of the P-element superfamily (Class II, subclass 1, TIR order). Furthermore, Galileo has a wide distribution in the genus Drosophila, since it has been found in 6 of the 12 Drosophila sequenced genomes. Among these species, D. mojavensis, the one closest to D. buzzatii, presented the highest diversity in sequence and structure of Galileo elements.

Results

In the present work, we carried out a thorough search and annotation of all the Galileo copies present in the D. mojavensis sequenced genome. In our set of 170 Galileo copies we have detected 5 Galileo subfamilies (C, D, E, F, and X) with different structures ranging from nearly complete, to only 2 TIR or solo TIR copies. Finally, we have explored the structural and length variation of the Galileo copies that point out the relatively frequent rearrangements within and between Galileo elements. Different mechanisms responsible for these rearrangements are discussed.

Conclusions

Although Galileo is a transposable element with an ancient history in the D. mojavensis genome, our data indicate a recent transpositional activity. Furthermore, the dynamism in sequence and structure, mainly affecting the TIRs, suggests an active exchange of sequences among the copies. This exchange could lead to new subfamilies of the transposon, which could be crucial for the long-term survival of the element in the genome.

Theranostic agents for intracellular gene delivery with spatiotemporal imaging

Gene therapy is the modification of gene expression to treat a disease. However, efficient intracellular delivery and monitoring of gene therapeutic agents is an ongoing challenge. Use of theranostic agents with suitable targeted, controlled delivery and imaging modalities has the potential to greatly advance gene therapy. Inorganic nanoparticles including magnetic nanoparticles, gold nanoparticles, and quantum dots have been shown to be effective theranostic agents for the delivery and spatiotemporal tracking of oligonucleotides in vitro and even a few cases in vivo. Major concerns remain to be addressed including cytotoxicity, particularly of quantum dots; effective dosage of nanoparticles for optimal theranostic effect; development of real-time in vivo imaging; and further improvement of gene therapy efficacy.

Hsmar1 transposition is sensitive to the topology of the transposon donor and the target

Hsmar1 is a member of the Tc1-mariner superfamily of DNA transposons. These elements mobilize within the genome of their host by a cut-and-paste mechanism. We have exploited the in vitro reaction provided by Hsmar1 to investigate the effect of DNA supercoiling on transposon integration. We found that the topology of both the transposon and the target affect integration. Relaxed transposons have an integration defect that can be partially restored in the presence of elevated levels of negatively supercoiled target DNA. Negatively supercoiled DNA is a better target than nicked or positively supercoiled DNA, suggesting that underwinding of the DNA helix promotes target interactions. Like other Tc1-mariner elements, Hsmar1 integrates into 5′-TA dinucleotides. The direct vicinity of the target TA provides little sequence specificity for target interactions. However, transposition within a plasmid substrate was not random and some TA dinucleotides were targeted preferentially. The distribution of intramolecular target sites was not affected by DNA topology.

Using defined finger-finger interfaces as units of assembly for constructing zinc-finger nucleases

Zinc-finger nucleases (ZFNs) have been used for genome engineering in a wide variety of organisms; however, it remains challenging to design effective ZFNs for many genomic sequences using publicly available zinc-finger modules. This limitation is in part because of potential finger–finger incompatibility generated on assembly of modules into zinc-finger arrays (ZFAs). Herein, we describe the validation of a new set of two-finger modules that can be used for building ZFAs via conventional assembly methods or a new strategy—finger stitching—that increases the diversity of genomic sequences targetable by ZFNs. Instead of assembling ZFAs based on units of the zinc-finger structural domain, our finger stitching method uses units that span the finger–finger interface to ensure compatibility of neighbouring recognition helices. We tested this approach by generating and characterizing eight ZFAs, and we found their DNA-binding specificities reflected the specificities of the component modules used in their construction. Four pairs of ZFNs incorporating these ZFAs generated targeted lesions in vivo, demonstrating that stitching yields ZFAs with robust recognition properties.

Ultrasound-mediated targeted drug delivery: recent success and remaining challenges

The potential clinical value of developing a novel, nonviral, ultrasound-directed gene and drug delivery system is immense. Investigators soon will initiate clinical trials with the goal of treating a wide variety of maladies using noninvasive, ultrasound-based technology. The ongoing, scientific validation associated with promising preclinical success portents a novel range of therapeutics. The clinical utility and eventual clinical successes await vigorous testing. This review highlights the recent successes and challenges within the field of ultrasound-mediated drug delivery.

Bimodal gold nanoparticle therapeutics for manipulating exogenous and endogenous protein levels in mammalian cells

A new advance in cell transfection protocol using a bimodal nanoparticle agent to selectively manipulate protein expression levels within mammalian cells is demonstrated. The nanoparticle based transfection approach functions by controlled release of gene regulatory elements from a 6 nm AuNP (gold nanoparticle) surface. The endosomal release of the regulatory elements from the nanoparticle surface results in endogenous protein knockdown simultaneously with exogenous protein expression for the first 48 h. The use of fluorescent proteins as the endogenous and exogenous signals for protein expression enables the efficiency of codelivery of siRNA (small interfering RNA) for GFP (green fluorescent protein) knockdown and a dsRed-express linearized plasmid for induction to be optically analyzed in CRL-2794, a human kidney cell line expressing an unstable green fluorescent protein. Delivery of the bimodal nanoparticle in cationic liposomes results in 20% GFP knockdown within 24 h of delivery and continues exhibiting knockdown for up to 48 h for the bimodal agent. Simultaneous dsRed expression is observed to initiate within the same time frame with expression levels reaching 34% after 25 days although cells have divided approximately 20 times, implying daughter cell transfection has occurred. Fluorescence cell sorting results in a stable colony, as demonstrated by Western blot analysis. The simultaneous delivery of siRNA and linearized plasmid DNA on the surface of a single nanocrystal provides a unique method for definitive genetic control within a single cell and leads to a very efficient cell transfection protocol.

Use of inert gas jets to measure the forces required for mechanical gene transfection

Background

Transferring genes and drugs into cells is central to how we now study, identify and treat diseases. Several non-viral gene therapy methods that rely on the mechanical disruption of the plasma membrane have been proposed, but the success of these methods has been limited due to a lack of understanding of the mechanical parameters that lead to cell membrane permeability.

Methods

We use a simple jet of inert gas to induce local transfection of plasmid DNA both in vitro (HeLa cells) and in vivo (chicken chorioallantoic membrane). Five different capillary tube inner diameters and three different gases were used to treat the cells to understand the dependency of transfection efficiency on the dynamic parameters.

Results

The simple setup has the advantage of allowing us to calculate the forces acting on cells during transfection. We found permeabilization efficiency was related to the dynamic pressure of the jet. The range of dynamic pressures that led to transfection in HeLa cells was small (200 ± 20 Pa) above which cell stripping occurred. We determined that the temporary pores allow the passage of dextran up to 40 kDa and reclose in less than 5 seconds after treatment. The optimized parameters were also successfully tested in vivo using the chorioallantoic membrane of the chick embryo.

Conclusions

The results show that the number of cells transfected with the plasmid scales with the dynamic pressure of the jet. Our results show that mechanical methods have a very small window in which cells are permeabilized without injury (200 to 290 Pa). This simple apparatus helps define the forces needed for physical cell transfection methods.

Transferrin-PEG-PE modified dexamethasone conjugated cationic lipid carrier mediated gene delivery system for tumor-targeted transfection

Background

The main barriers to non-viral gene delivery include cellular and nuclear membranes. As such, the aim of this study was to develop a type of vector that can target cells through receptor-mediated pathways and by using nuclear localization signal (NLS) to increase the nuclear uptake of genetic materials.

Methods

A dexamethasone (Dexa)-conjugated lipid was synthesized as the material of the solid lipid nanoparticles (SLNs), and transferrin (Tf) was linked onto polyethylene glycol-phosphatidylethanolamine (PEG-PE) to obtain Tf-PEG-PE ligands for the surface modification of the carriers. The in vitro transfection efficiency of the novel modified vectors was evaluated in human hepatoma carcinoma cell lines, and in vivo effects were observed in an animal model.

Results

Tf-PEG-PE modified SLNs/enhanced green fluorescence protein plasmid (pEGFP) had a particle size of 222 nm and a gene loading quantity of 90%. Tf-PEG-PE-modified SLNs/pEGFP (Tf-SLNs/pEGFP) displayed remarkably higher transfection efficiency than non-modified SLNs/pEGFP and the vectors not containing Dexa, both in vitro and in vivo.

Conclusion

It can be concluded that Tf and Dexa could function as an excellent active targeting ligand to improve the cell targeting and nuclear targeting ability of the carriers, and the resulting nanomedicine could be a promising active targeting drug/gene delivery system.

Calcium carbonate microparticles used as a gene vector for delivering p53 gene into cancer cells

Calcium carbonate (CaCO(3) ) microparticles were for the first time used for efficient delivery of p53 gene to transfect human cancer cells HeLa. CaCO(3) microparticles (2-4 μm) absorbed pEGFP-C1-p53 (expressing GFP-P53 fusion protein) to transfect HeLa cells. Flow cytometer (FCM) was used to evaluate the gene transfection efficiency in HeLa cells, which were stably transduced with a green fluorescent protein gene. In this study, CaCO(3) delivering pEGFP-C1-p53 could transfect about 5% of the tumor cells in culture. However, the efficiency of tumor cell apoptosis was surprisingly up to 80%. Meanwhile, the results of MTT assay and crystal violet staining showed that the CaCO(3) microparticles had low cytotoxicity. These findings showed that CaCO(3) microparticles were perspective to be used as new vectors for gene therapy.

Mannosylated liposomes for targeted gene delivery

Background

Liposomes can be modified with different ligands to control their biological properties, such as longevity, targeting ability, and intracellular penetration, in a desired fashion. The aim of this study was to modify liposomes with a novel mannosylated polyethylene glycol-phosphatidylethanolamine (M-PEG-PE) ligand to achieve active targeted gene delivery.

Methods

Rat Kupffer cells were isolated and used as model cells for in vitro evaluation of cytotoxicity and transfection efficiency. The modified liposomes were intravenously injected into the rats, and Kupffer cells were isolated and analyzed by flow cytometry for in vivo gene delivery and expression.

Results

The M-PEG-PE-modified liposome-enhanced green fluorescence protein plasmid (M-PEG-PE-Lipo-pEGFP) complexes had a particle size of 237 nm and a loading efficiency of 90%. The M-PEG-PE-Lipo-pEGFP complexes displayed remarkably higher transfection efficiency than unmodified Lipo-pEGFP, both in vitro (51%–30%) and in vivo (43%–27%).

Conclusion

M-PEG-PE could function as an excellent active targeting ligand, and M-PEG-PE-modified liposomes could be promising active targeted drug delivery vectors.