Factors Influencing the Ability of Nuclear Localization Sequence Peptides To Enhance Nonviral Gene Delivery

Advancing ocular gene therapy: a machine learning approach to enhance delivery, uptake and gene expression

Ocular gene therapy offers a promising approach for treating various eye diseases, centered on the process of transfection, including delivery, cellular uptake and gene expression. This study addresses anatomical and physiological barriers, such as the eyelids, tear film, conjunctiva, cornea, sclera, choroid and retina, affecting therapeutic success. A three-step machine-learning approach is proposed. The first step predicts gene delivery efficacy by integrating molecular characteristics of the ocular gene therapy product, ocular barrier properties and patient demographics. The second step predicts cellular uptake rates, analyzing product penetration and cellular interactions. The final step forecasts gene expression levels, considering factors like nucleic acid type and endosomal escape. An artificial neural network model is recommended to capture complex, nonlinear relationships, enhancing our understanding of therapeutic and biological interactions.

Nanocarrier-based gene delivery for immune cell engineering

Clinical advances in genetically modified immune cell therapies, such as chimeric antigen receptor T cell therapies, have raised hope for cancer treatment. The majority of these biotechnologies are based on viral methods for ex vivo genetic modification of the immune cells, while the non-viral methods are still in the developmental phase. Nanocarriers have been emerging as materials of choice for gene delivery to immune cells. This is due to their versatile physicochemical properties such as large surface area and size that can be optimized to overcome several practical barriers to successful gene delivery. The in vivo nanocarrier-based gene delivery can revolutionize cell-based cancer immunotherapies by replacing the current expensive autologous cell manufacturing with an off-the-shelf biomaterial-based platform. The aim of this research is to review current advances and strategies to overcome the challenges in nanoparticle-based gene delivery and their impact on the efficiency, safety, and specificity of the process. The main focus is on polymeric and lipid-based nanocarriers, and their recent preclinical applications for cancer immunotherapy.

Nuclear localization signal-tagged systems: relevant nuclear import principles in the context of current therapeutic design

Nuclear targeting of therapeutics provides a strategy for enhancing efficacy of molecules active in the nucleus and minimizing off-target effects. 'Active' nuclear-directed transport and efficient translocations across nuclear pore complexes provide the most effective means of maximizing nuclear localization. Nuclear-targeting systems based on nuclear localization signal (NLS) motifs have progressed significantly since the beginning of the current millennium. Here, we offer a roadmap for understanding the basic mechanisms of nuclear import in the context of actionable therapeutic design for developing NLS-therapeutics with improved treatment efficacy.

Peptide-Assisted Nucleic Acid Delivery Systems on the Rise

Concerns associated with nanocarriers' therapeutic efficacy and side effects have led to the development of strategies to advance them into targeted and responsive delivery systems. Owing to their bioactivity and biocompatibility, peptides play a key role in these strategies and, thus, have been extensively studied in nanomedicine. Peptide-based nanocarriers, in particular, have burgeoned with advances in purely peptidic structures and in combinations of peptides, both native and modified, with polymers, lipids, and inorganic nanoparticles. In this review, we summarize advances on peptides promoting gene delivery systems. The efficacy of nucleic acid therapies largely depends on cell internalization and the delivery to subcellular organelles. Hence, the review focuses on nanocarriers where peptides are pivotal in ferrying nucleic acids to their site of action, with a special emphasis on peptides that assist anionic, water-soluble nucleic acids in crossing the membrane barriers they encounter on their way to efficient function. In a second part, we address how peptides advance nanoassembly delivery tools, such that they navigate delivery barriers and release their nucleic acid cargo at specific sites in a controlled fashion.

Human-derived NLS enhance the gene transfer efficiency of chitosan

Nuclear import is considered as one of the major limitations for non-viral gene delivery systems and the incorporation of nuclear localization signals (NLS) that mediate nuclear intake can be used as a strategy to enhance internalization of exogenous DNA.

In this work, human-derived endogenous NLS peptides based on insulin growth factor binding proteins (IGFBP), namely IGFBP-3 and IGFBP-5, were tested for their ability to improve nuclear translocation of genetic material by non-viral vectors. Several strategies were tested to determine their effect on chitosan mediated transfection efficiency: co-administration with polyplexes, co-complexation at the time of polyplex formation, and covalent ligation to chitosan. Our results show that co-complexation and covalent ligation of the NLS peptide derived from IGFBP-3 to chitosan polyplexes yields a 2-fold increase in transfection efficiency, which was not observed for NLS peptide derived from IGFBP-5.

These results indicate that the integration of IGFBP-NLS-3 peptides into polyplexes has potential as a strategy to enhance the efficiency of non-viral vectors.

Peptides as a material platform for gene delivery: Emerging concepts and converging technologies

Successful gene therapies rely on methods that safely introduce DNA into target cells and enable subsequent expression of proteins. To that end, peptides are an attractive materials platform for DNA delivery, facilitating condensation into nanoparticles, delivery into cells, and subcellular release to enable protein expression. Peptides are programmable materials that can be designed to address biocompatibility, stability, and subcellular barriers that limit efficiency of non-viral gene delivery systems. This review focuses on fundamental structure-function relationships regarding peptide design and their impact on nanoparticle physical properties, biologic activity, and biocompatibility. Recent peptide technologies utilize multi-dimensional structures, non-natural chemistries, and combinations of peptides with lipids to achieve desired properties and efficient transfection. Advances in DNA cargo design are also presented to highlight further opportunities for peptide-based gene delivery. Modern DNA designs enable prolonged expression compared to traditional plasmids, providing an additional component that can be synergized with peptide carriers for improved transfection. Peptide transfection systems are poised to become a flexible and efficient platform incorporating new chemistries, functionalities, and improved DNA cargos to usher in a new era of gene therapy.

Non-Viral Targeted Nucleic Acid Delivery: Apply Sequences for Optimization

In nature, genomes have been optimized by the evolution of their nucleic acid sequences. The design of peptide-like carriers as synthetic sequences provides a strategy for optimizing multifunctional targeted nucleic acid delivery in an iterative process. The optimization of sequence-defined nanocarriers differs for different nucleic acid cargos as well as their specific applications. Supramolecular self-assembly enriched the development of a virus-inspired non-viral nucleic acid delivery system. Incorporation of DNA barcodes presents a complementary approach of applying sequences for nanocarrier optimization. This strategy may greatly help to identify nucleic acid carriers that can overcome pharmacological barriers and facilitate targeted delivery in vivo. Barcode sequences enable simultaneous evaluation of multiple nucleic acid nanocarriers in a single test organism for in vivo biodistribution as well as in vivo bioactivity.

The cell-penetrating YopM protein-functionalized quantum dot-plasmid DNA conjugate as a novel gene delivery vector

Non-viral gene delivery systems have great potential for safe and efficient gene therapy, while inefficient cellular and nuclear uptake remain as the major hurdles. Novel approaches are needed to enhance the transfection efficiency of non-viral vectors. In accordance with this need, the objective of this study was to construct a non-viral vector that could achieve gene delivery without using additional lipid-based transfection agent. We aimed to impart self-delivery property to a non-viral vector by using the cell and nucleus penetrating properties of YopM proteins from the three Yersinia spp. (Y. pestis, Y. enterocolotica and Y. pseudotuberculosis). Plasmid DNA (pDNA) encoding green fluorescent protein (GFP) was labeled with quantum dots (QDs) via peptide-nucleic acid (PNA) recognition site. Recombinant YopM protein was then attached to the conjugate via a second PNA recognition site. The YopM ̶ QDs ̶ pDNA conjugate was transfected into HeLa cells without using additional transfection reagent. All three conjugates produced GFP fluorescence, indicating that the plasmid was successfully delivered to the nucleus. As control, naked pDNA was transfected into the cells by using a commercial transfection reagent. The Y. pseudotuberculosis YopM-functionalized conjugate achieved the highest GFP expression, compared to other two YopM proteins and the transfection reagent. To the best of our knowledge, YopM protein was used for the first time in a non-viral gene delivery vector.

Functional peptide-based drug delivery systems

Peptides are one of the most important functional motifs for constructing smart drug delivery systems (DDSs). Functional peptides can be conjugated with drugs or carriers via covalent bonds, or assembled into DDSs via supramolecular forces, which enables the DDSs to acquire desired functions such as targeting and/or environmental responsiveness. In this mini review, we first introduce the different types of functional peptides that are commonly used for constructing DDSs, and we highlight representative strategies for designing smart DDSs by using functional peptides in the past few years. We also state the challenges of peptide-based DDSs and come up with prospects.

Enhancement of Angiogenesis by Ultrasound-Targeted Microbubble Destruction Combined with Nuclear Localization Signaling Peptides in Canine Myocardial Infarction

Objective

This study aimed to develop a gene delivery system using ultrasound-targeted microbubbles destruction (UTMD) combined with nuclear localization signal (NLS) and investigate its efficacy and safety for therapeutic angiogenesis in canine myocardial infarction (MI) model.

Methods

Fifty MI dogs were randomly divided into 5 groups and transfected with Ang-1 gene plasmid: (i) group A: only injection of microbubbles and Ang-1 plasmid; (ii) group B: only UTMD mediated gene transfection; (iii) group C: UTMD combined with classical NLS mediated gene transfection; (iv) group D: UTMD combined with mutational NLS mediated transfection; and (v) group E: UTMD combined with classical NLS in the presence of a nucleus transport blocker. The mRNA and protein expression of Ang-1 gene, microvessel density (MVD) cardiac troponin I (cTnI), and cardiac function were determined after transfection.

Results

The expression of mRNA and protein of Ang-1 gene in group C was significantly higher than that of the other groups (all P < 0.01). The MVD of group C was 10.2-fold of group A and 8.1-fold of group E (P < 0.01). The cardiac function in group C was significant improvement without cTnI rising.

Conclusions

The gene delivery system composed of UTMD and NLS is efficient and safe.

Non-Covalent Loading of Anti-Cancer Doxorubicin by Modularizable Peptide Self-Assemblies for a Nanoscale Drug Carrier

We prepared nanoscale, modularizable, self-assembled peptide nanoarchitectures with diameters less of than 20 nm by combining β-sheet-forming peptides tethering a cell-penetrating peptide or a nuclear localization signal sequence. We also found that doxorubicin (Dox), an anti-cancer drug, was non-covalently accommodated by the assemblies at a ratio of one Dox molecule per ten peptides. The Dox-loaded peptide assemblies facilitated cellular uptake and subsequent nuclear localization in HeLa cells, and induced cell death even at low Dox concentrations. This peptide nanocarrier motif is a promising platform for a biocompatible drug delivery system by altering the targeting head groups of the carrier peptides.

Solid-phase supported design of carriers for therapeutic nucleic acid delivery

Nucleic acid molecules are important therapeutic agents in the field of antisense oligonucleotide, RNA interference, and gene therapies. Since nucleic acids are not able to cross cell membranes and enter efficiently into cells on their own, the development of efficient, safe, and precise delivery systems is the crucial challenge for development of nucleic acid therapeutics. For the delivery of nucleic acids to their intracellular site of action, either the cytosol or the nucleus, several extracellular and intracellular barriers have to be overcome. Multifunctional carriers may handle the different special requirements of each barrier. The complexity of such macromolecules however poses a new hurdle in medical translation, which is the chemical production in reproducible and well-defined form. Solid-phase assisted synthesis (SPS) presents a solution for this challenge. The current review provides an overview on the design and SPS of precise sequence-defined synthetic carriers for nucleic acid cargos.

Efficient gene therapy with a combination of ultrasound‑targeted microbubble destruction and PEI/DNA/NLS complexes

Current strategies of gene transfection are not efficient at achieving a notable therapeutic effect. The aim of the present study was to combine ultrasound‑targeted microbubble destruction (UTMD) with a polyethylenimine/pEGFP‑N3 plasmid/nuclear localization sequence (PEI/DNA/NLS) complex gene delivery system, and evaluate the transfection efficiency of enhanced green fluorescent protein (EGFP) gene delivery to 293T cells using this system. The formation of PEI/DNA/NLS complexes and the protective effects of PEI/NLS were verified by gel electrophoresis. Solutions consisting of the plasmid alone, PEI/DNA complexes, PEI/DNA/NLS complexes, UTMD+DNA, UTMD+PEI/DNA complexes, and UTMD+PEI/DNA/NLS complexes were transduced into 293T cells via ultrasound irradiation. The expression of GFP was observed using an inverted microscope and transfection efficiency was detected by flow cytometry following 24 h incubation in vitro. Cell activity was detected using a Cell Counting kit (CCK)‑8 assay. Gel electrophoresis confirmed the formation of PEI/DNA/NLS complexes and demonstrated that PEI/NLS exhibited protective effects on plasmid integrity for a limited time. Inverted microscope observations revealed that a greater GFP signal was observed with the combined action of PEI/DNA/NLS complexes with UTMD, and flow cytometry analysis demonstrated the highest level of transfection efficiency in this group. In addition, the viability of the cells detected by CCK‑8 and treated with PEI/DNA/NLS complexes with UTMD was >80%. In conclusion, the combination of UTMD and PEI/DNA/NLS complexes was highly effective for the efficient transfection of 293T cells without causing excessive cell damage. This method may provide a novel and effective gene transduction system to be applied in clinical treatments.

Nonviral cancer gene therapy: Delivery cascade and vector nanoproperty integration

Gene therapy represents a promising cancer treatment featuring high efficacy and limited side effects, but it is stymied by a lack of safe and efficient gene-delivery vectors. Cationic polymers and lipid-based nonviral gene vectors have many advantages and have been extensively explored for cancer gene delivery, but their low gene-expression efficiencies relative to viral vectors limit their clinical translations. Great efforts have thus been devoted to developing new carrier materials and fabricating functional vectors aimed at improving gene expression, but the overall efficiencies are still more or less at the same level. This review analyzes the cancer gene-delivery cascade and the barriers, the needed nanoproperties and the current strategies for overcoming these barriers, and outlines PEGylation, surface-charge, size, and stability dilemmas in vector nanoproperties to efficiently accomplish the cancer gene-delivery cascade. Stability, surface, and size transitions (3S Transitions) are proposed to resolve those dilemmas and strategies to realize these transitions are comprehensively summarized. The review concludes with a discussion of the future research directions to design high-performance nonviral gene vectors.

Simultaneous delivery of anti-miR21 with doxorubicin prodrug by mimetic lipoprotein nanoparticles for synergistic effect against drug resistance in cancer cells

The development of drug resistance in cancer cells is one of the major obstacles to achieving effective chemotherapy. We hypothesized that the combination of a doxorubicin (Dox) prodrug and microRNA (miR)21 inhibitor might show synergistic antitumor effects on drug-resistant breast cancer cells. In this study, we aimed to develop new high-density lipoprotein-mimicking nanoparticles (HMNs) for coencapsulation and codelivery of this potential combination. Dox was coupled with a nuclear localization signal (NLS) peptide to construct a prodrug (NLS-Dox), thereby electrostatically condensing miR21 inhibitor (anti-miR21) to form cationic complexes. The HMNs were formulated by shielding these complexes with anionic lipids and Apo AI proteins. We have characterized that the coloaded HMNs had uniformly dispersed distribution, favorable negatively charged surface, and high coencapsulation efficiency. The HMN formulation effectively codelivered NLS-Dox and anti-miR21 into Dox-resistant breast cancer MCF7/ADR cells and wild-type MCF7 cells via a high-density-lipoprotein receptor-mediated pathway, which facilitated the escape of Pgp drug efflux. The coloaded HMNs consisting of NLS-Dox/anti-miR21 demonstrated greater cytotoxicity with enhanced intracellular accumulation in resistant MCF7/ADR cells compared with free Dox solution. The reversal of drug resistance by coloaded HMNs might be attributed to the suppression of miR21 expression and the related antiapoptosis network. Furthermore, the codelivery of anti-miR21 and NLS-Dox by HMNs showed synergistic antiproliferative effects in MCF7/ADR-bearing nude mice, and was more effective in tumor inhibition than other drug formulations. These data suggested that codelivery of anti-miR21 and chemotherapeutic agents by HMNs might be a promising strategy for antitumor therapy, and could restore the drug sensitivity of cancer cells, alter intracellular drug distribution, and ultimately enhance chemotherapeutic effects.

Versatile nuclear localization signal-based oligopeptide as a gene vector

To develop a versatile nuclear-targeted gene vector, nuclear localization signal (NLS) oligopeptides combining cysteine (C), histidine (H), and stearic acid (STR) were investigated in this study. The original SV40 sequence (SV40: Pro-Lys-Lys-Lys-Arg-Lys-Val) was selected as the NLS sequence, and physical characterizations of various NLS-based oligopeptides (CSV40C, STR-CSV40C, and STR-CH2SV40H2C), including mean diameter, zeta-potential, complex condensation, and decondensation, were evaluated. In addition, cellular and nuclear uptake of plasmid DNA (pDNA) and gene expression in COS7 and dendritic cells (JAWS II) were determined. As a result, C and STR enhanced formation of a smaller and more stable nano-complex with pDNA based on ionic interactions, the disulfide linkage and hydrophobic interactions. STR-CSV40C and STR-CH2SV40H2C had significantly higher cellular uptake ability and transfection efficiency than SV40 and CSV40C. In particular, STR-CH2SV40H2C had higher nuclear uptake and gene expression efficiency than STR-CSV40C. Furthermore, STR-CH2SV40H2C could deliver pDNA to the nuclei and had high gene expression efficiency in dendritic cells. Our results indicate that STR-CH2SV40H2C is a promising gene delivery system in non- or slow-dividing cells.

Poly(Amido Amine)s Containing Agmatine and Butanol Side Chains as Efficient Gene Carriers

A new type of bioreducible poly(amido amine) copolymer is synthesized by the Michael addition polymerization of cystamine bisacrylamide (CBA) with 4-aminobutylguanidine (agmatine, AGM) and 4-aminobutanol (ABOL). Since the positively charged guanidinium groups of AGM and the hydroxybutyl groups of ABOL in the side chains have shown to improve the overall transfection efficiency of poly(amido amine)s, it is hypothesized that poly(CBA-ABOL/AGM) synthesized at the optimal ratio of both components would result in high transfection efficiency and minimal toxicity. In this study, a series of the poly(CBA-ABOL/AGM) copolymers is synthesized as gene carriers. The polymers are characterized and luciferase transfection efficiencies of the polymers in various cell lines are investigated to select the ideal ratio between AGM and ABOL. The poly(CBA-ABOL/AGM) containing 80% AGM and 20% ABOL has shown the best transfection efficiency with the lowest cytotoxicity, indicating that this polymer is very promising as a potent and nontoxic gene carrier.

Delivery of nucleic acids and nanomaterials by cell-penetrating peptides: opportunities and challenges

Many viral and nonviral systems have been developed to aid delivery of biologically active molecules into cells. Among these, cell-penetrating peptides (CPPs) have received increasing attention in the past two decades for biomedical applications. In this review, we focus on opportunities and challenges associated with CPP delivery of nucleic acids and nanomaterials. We first describe the nature of versatile CPPs and their interactions with various types of cargoes. We then discuss in vivo and in vitro delivery of nucleic acids and nanomaterials by CPPs. Studies on the mechanisms of cellular entry and limitations in the methods used are detailed.

Development and Challenges of Nanovectors in Gene Therapy

In recent years, hundreds of genes have been linked to a variety of human diseases, and the field of gene therapy has emerged as a way to treat this wide range of diseases. The main goal of gene therapy is to find a gene delivery vehicle that can successfully target diseased cells and deliver therapeutic genes directly to their cellular compartment. The two main types of gene delivery vectors currently being investigated in clinical trials are recombinant viral vectors and synthetic nonviral vectors. Recombinant viral vectors take advantage of the evolutionarily optimized viral mechanisms to deliver genes, but they can be hard to specifically target in vivo and are also associated with serious side effects. Synthetic nonviral vectors are made out of highly biocompatible lipids or polymers, but they are much less efficient at delivering their genetic payload due to the lack of any active delivery mechanism. This mini review will introduce the current state of gene delivery in clinical trials, and discuss the specific challenges associated with each of these vectors. It will also highlight some specific gaps in knowledge that are limiting the advancement of this field and touch on the current areas of research being explored to overcome them.

Multifunctional non-viral gene vectors with enhanced stability, improved cellular and nuclear uptake capability, and increased transfection efficiency

We have developed a new multifunctional, non-viral gene delivery platform consisting of cationic poly(amine-co-ester) (PPMS) for DNA condensation, PEG shell for nanoparticle stabilization, poly(γ-glutamic acid) (γ-PGA) and mTAT (a cell-penetrating peptide) for accelerated cellular uptake, and a nuclear localization signal peptide (NLS) for enhanced intracellular transport of DNA to the nucleus. In vitro study showed that coating of the binary PPMS/DNA polyplex with γ-PGA promotes cellular uptake of the polyplex particles, particularly by γ-glutamyl transpeptidase (GGT)-positive cells through the GGT-mediated endocytosis pathway. Conjugating PEG to the γ-PGA led to the formation of a ternary PPMS/DNA/PGA-g-PEG polyplex with decreased positive charges on the surface of the polyplex particles and substantially higher stability in serum-containing aqueous medium. The cellular uptake rate was further improved by incorporating mTAT into the ternary polyplex system. Addition of the NLS peptide was designed to facilitate intracellular delivery of the plasmid to the nucleus--a rate-limiting step in the gene transfection process. As a result, compared with the binary PPMS/LucDNA polyplex, the new mTAT-quaternary PPMS/LucDNA/NLS/PGA-g-PEG-mTAT system exhibited reduced cytotoxicity, remarkably faster cellular uptake rate, and enhanced transport of DNA to the nucleus. All these advantageous functionalities contribute to the remarkable gene transfection efficiency of the mTAT-quaternary polyplex both in vitro and in vivo, which exceeds that of the binary polyplex and commercial Lipofectamine™ 2000/DNA lipoplex. The multifunctional mTAT-quaternary polyplex system with improved efficiency and reduced cytotoxicity represents a new type of promising non-viral vectors for the delivery of therapeutic genes to treat tumors.

Contrasting effects of cysteine modification on the transfection efficiency of amphipathic peptides

Delivery of DNA to cells remains a key challenge towards development of gene therapy. A better understanding of the properties involved in stability and transfection efficiency of the vector could critically contribute to the improvement of delivery vehicles. In the present work we have chosen two peptides differing only in amphipathicity and explored how presence of cysteine affects DNA uptake and transfection efficiency. We report an unusual observation that addition of cysteine selectively increases transfection efficiency of secondary amphipathic peptide (Mgpe-9) and causes a drop in the primary amphipathic peptide (Mgpe-10). Our results point the effect of cysteine is dictated by the importance of physicochemical properties of the carrier peptide. We also report a DNA delivery agent Mgpe-9 exhibiting high transfection efficiency in multiple cell lines (including hard-to-transfect cell lines) with minimal cytotoxicity which can be further explored for in vivo applications.

Incorporation of histone derived recombinant protein for enhanced disassembly of core-membrane structured liposomal nanoparticles for efficient siRNA delivery

A novel recombinant protein tetra-H2A (TH) derived from histone H2A has been developed to replace protamine as a conditionally reversible, nucleic acid condensing agent. The novel protein will address the insufficient release of nucleic acid therapeutics, which is captured by protamine for siRNA delivery. TH is composed of 4 tandem repeats of the histone H2A N-terminal sequence, intervened by the cathepsin D cleavage site. The repeating H2A sequence enhances the binding affinity to anionic nucleic acids, forming more stable condensates, as demonstrated by the binding affinity assay. The TH/siRNA condensates are formulated into a core-membrane structured liposomal nanoparticle (NP). The endosomes of cancer cells are rich in cathepsin D, allowing on-site degradation of TH and facilitating the intracellular release of siRNA. The NPs assembled with TH produced a higher silencing efficiency of target genes in vitro and in vivo than the NPs assembled with protamine as the nucleic acid condensing agent. The exploitation of TH in the NP formulation exhibited a biocompatibility profile similar to that of protamine, with minimal immunostimulating and systemic toxicity observed after repeated administration.

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.

Enhancement of gene transfer efficiency in the Bcap-37 cell line by dimethyl sulphoxide and menthol

Simple and efficient gene transfer into the nucleus would facilitate non-viral gene delivery. One promising method of non-viral gene delivery is to apply penetration enhancers. Chemicals, such as dimethyl sulfoxide (DMSO) and menthol, may have promise as non-toxic vehicles in improving gene transfer efficiency. In this study, the cytotoxic effects of DMSO and menthol were evaluated using MTT assays. Gene delivery efficiency in a human breast cancer cell line (Bcap-37) was investigated by quantitative PCR, fluorescence microscopy and flow cytometry. Non-toxic concentrations of DMSO (2%) and menthol (12.5 µM) enhanced the efficiency of liposome-mediated gene delivery in Bcap-37 cells. Quantitative PCR results showed that growth hormone (GH) mRNA expression in the post-menthol and pre-DMSO treatment groups was 10-fold higher compared to that in the liposome group, while in the pre-menthol and post-DMSO treatment groups, a 30-fold increase in GH mRNA expression was observed. Both DMSO and menthol treatments increased green fluorescent protein (GFP) expression efficiency as shown by fluorescence microscopy experiments. Compared to the liposome group, the number of positive cells in the pre-menthol and post-DMSO treatment groups was significantly increased by 15%. Furthermore, cell cycle analysis demonstrated that there were significant differences among the DMSO-treated group, the menthol-treated group and the normal group, which implied different effects of DMSO and menthol treatments. In conclusion, both non-toxic and harmless DMSO (2%) and menthol (12.5 µM) treatments improve gene transfer efficiency, while post-DMSO treatment may be the most effective protocol in increasing transgene expression efficiency.

Non-viral gene therapy for spinal cord regeneration

Spinal cord injury (SCI) normally results in life-long disabilities and a broad range of secondary complications. Advances in therapeutic delivery during the past few decades offer hope for such victims. However, the limited functional improvement shown in in vivo studies hinders effective therapeutic application in clinical practice. Recent studies showed that gene vectors can transfect cells present in the lesion of an injured spinal cord (endogenous cells) and thereby produce therapeutic molecules with long-lasting biological effects that promote neural tissue regeneration. In this article we review recent advances in non-viral gene delivery into neural cells and their use for gene therapy in SCI.

DNA nuclear targeting sequences for non-viral gene delivery

Purpose

To evaluate if introduction of DNA nuclear Targeting Sequences (DTS; i.e. recognition sequences for endogenous DNA-binding proteins) in plasmid DNA (pDNA) leads to increased transfection efficiency of non-viral gene delivery by virtue of enhanced nuclear import of the pDNA.

Methods

A set of DTS was identified and cloned into EGFP-reporter plasmids controlled by the CMV-promoter. These pDNA constructs were delivered into A431 and HeLa cells using standard electroporation, pEI-based polyfection or lipofection methods. The amount of pDNA delivered into the nucleus was determined by qPCR; transfection efficiency was determined by flow cytometry.

Results

Neither of these DTS increased transgene expression. We varied several parameters (mitotic activity, applied dose and delivery strategy), but without effect. Although upregulated transgene expression was observed after stimulation with TNF-α, this effect could be ascribed to non-specific upregulation of transcription rather than enhanced nuclear import. Nuclear copy numbers of plasmids containing or lacking a DTS did not differ significantly after lipofectamine-based transfection in dividing and non-dividing cells.

Conclusion

No beneficial effects of DTS on gene expression or nuclear uptake were observed in this study.

Construction of cell penetrating peptide vectors with N-terminal stearylated nuclear localization signal for targeted delivery of DNA into the cell nuclei

Cellular uptake and nuclear localization are two barriers to gene delivery. Here, we designed new gene delivery carriers with an N-terminal stearylated (STR) nuclear localization signal (NLS), PKKKRKV, present in the Simian Virus 40 large T antigen with the aim to overcome limitations, such as cell membrane and nuclear pores, offering attractive possibilities to enhance gene delivery. Four vectors with different structures of N-stearylated nuclear localization signal-octaarginine peptide (STR-PKKKRKV-R(8) or STR-NLS-R(8), STR-VKRKKKP-R(8) or STR-reverse NLS-R(8), PKKKRKV-R(8) or NLS-R(8), and VKRKKKP-R(8) or reverse NLS-R(8)) were compared. The gene expression mediated by these vectors in dividing and non-dividing cells (both in 293T and HeLa cell lines) was investigated. The most efficient N/P ratio was 4 for STR-PKKKRKV-R(8,) STR-VKRKKKP-R(8,) and 0.25 for PKKKRKV-R(8), VKRKKKP-R(8.) The maximum transfection activity of these vehicles (VKRKKKP-R(8)) was up to 80% as effective as jetPEI™ and the vehicles did not exhibit cytotoxicity. Interestingly, N-stearylated peptides presented lower transfection activity compared to peptides without N-stearylation at lower N/P ratios (0.25 to 1). Confocal study showed that the vectors could effectively promote the nuclear translocation.

Efficient intracellular gene delivery using the formulation composed of poly (L-glutamic acid) grafted polyethylenimine and histone

PURPOSE

Inefficient endosomal escape and poor nuclear import are thought to contribute to low gene transfer efficiency of polycations. To overcome these drawbacks, we prepared multiple gene delivery formulations including low cytotoxic polycation, histone containing NLSs and chloroquine as the endosomolytic agent.

METHODS

Comb-shaped poly (L-glutamic acid) grafted low-molecular-weight polyethylenimine (PLGE) copolymer was synthesized by aminolysis of poly-γ-benzyl-L-glutamate using low-molecular-weight polyethylenimine (800 Da). The formation of DNA/histone/PLGE terplex was observed by atomic force microscope and gel retardation assay. The particle size and zeta potential of DNA complexes with varying content of histone were also measured to confirm the terplex formation. Cytotoxicity of vectors was assayed by MTT. Multiple gene delivery formulations were optimized to their best transfection efficiency that was monitored by fluorescence microscope and flow cytometry. In vivo gene delivery of the optimal formulation was evaluated by the GFP-expression levels in drosophila melanogaster.

RESULTS

The DNA/histone/PLGE terplex was successfully formed. The PLGE and histone together condensed DNA into small, discrete particles (less than 200 nm in diameter) in isotonic solution. Cytotoxicity of PLGE and histone were much lower than that of PEI 25 K. Either histone or chloroquine contributed to enhancing the levels of transfection activity of PLGE polymer. However, chloroquine and histone did not show a synergistic effect on the improvement of transfection efficiency. The optimal formulation was the DNA/histone/PLGE terplex at the N/P ratio of 15 and histone/ DNA weight ratio of 0.8. Compared with Lipofectamine 2000 and PEI 25 K, the optimal formulation showed significantly increased levels of GFP-expression both in vitro and in vivo.

CONCLUSION

This formulation provided a versatile approach for preparing high efficiency of the polycation-based gene vectors. It also reinforced the finding of earlier studies that nuclear import and endosomal escape were rate-limiting steps for nonviral gene delivery.

Multifunctional peptide-PEG intercalating conjugates: programmatic of gene delivery to the blood-brain barrier

PURPOSE

To enhance transfection efficacy of pDNA through the application of multifunctional peptide-PEG-tris-acridine conjugates (pPAC) and the formation of biodegradable core-shell polyplexes for gene delivery to the blood-brain barrier (BBB).

METHODS

pPAC-mediated transfection was compositionally optimized in mouse BBB cells (bEnd.3). Cellular uptake and trafficking, and brain accumulation of pDNA was evaluated by fluorescent imaging and histochemistry. We constructed anti-MRP4 siRNA-producing vectors and evaluated the efficacy of MRP4 down-regulation of MRP4 by Western blot and qPCR, and its effect on the uptake of (3)H-AZT, an MRP4 substrate.

RESULTS

A core-shell gene delivery system (GDS) was assembled from pDNA and pPAC, carrying multifunctional peptides with NLS, TAT, and brain-specific BH, or ApoE sequences, and biodegradable pLPEI polyamine. This GDS demonstrated better cellular and nuclear accumulation, and a 25-fold higher transfection efficacy in slow-dividing bEnd.3 cells compared to ExGen500. Inclusion of brain-targeting pPAC enhanced in vivo accumulation of functional pDNA in brain capillaries. Treatment by encapsulated anti-MRP4 siRNA-producing pDNA caused transient down-regulation of MRP4, and, after intravenous injection in Balb/c mice, enhanced AZT uptake in the brain by 230-270%.

CONCLUSIONS

The pPAC represent novel efficient components of GDS that could find various gene therapy applications, including genetic modulation of the BBB.

Polycation-induced cell membrane permeability does not enhance cellular uptake or expression efficiency of delivered DNA

Polycationic materials commonly used to delivery DNA to cells are known to induce cell membrane porosity in a charge-density dependent manner. It has been suggested that these pores may provide a mode of entry of the polymer-DNA complexes (polyplexes) into cells. To examine the correlation between membrane permeability and biological activity, we used two-color flow cytometry on two mammalian cell lines to simultaneously measure gene expression of a plasmid DNA delivered with four common nonviral vectors and cellular uptake of normally excluded fluorescent dye molecules of two different sizes, 668 Da and 2 MDa. We also followed gene expression in cells sorted based on the retention of endogenous fluorescein. We have found that cell membrane porosity caused by polycationic vectors does not enhance internalization or gene expression. Based on this single-cell study, membrane permeability is found to be an unwanted side effect that limits transfection efficiency, possibly through leakage of the delivered nucleic acid through the pores prior to transcription and translation and/or activation of cell defense mechanisms that restrict transgene expression.

Advances with the use of bio-inspired vectors towards creation of artificial viruses

IMPORTANCE OF THE FIELD

In recent years, there has been a great deal of interest in the development of recombinant vectors based on biological motifs with potential applications in gene therapy. Several such vectors have been genetically engineered, resulting in biomacromolecules with new properties that are not present in nature.

AREAS COVERED IN THIS REVIEW

This review briefly discusses the advantages and disadvantages of the current state-of-the-art gene delivery systems (viral and non-viral) and then provides an overview on the application of various biological motifs in vector development for gene delivery. Finally, it highlights some of the most advanced bio-inspired vectors that are designed to perform several self-guided functions.

WHAT THE READER WILL GAIN

This review helps the readers get a better understanding about the history and evolution of bio-inspired fusion vectors with the potential to merge the strengths of both viral and non-viral vectors in order to create efficient, safe and cost-effective gene delivery systems.

TAKE HOME MESSAGE

With the emergence of new technologies such as recombinant bio-inspired vectors, it may not take long before non-viral vectors are observed that are not just safe and tissue-specific, but even more efficient than viral vectors.

Enhanced lipoplex-mediated gene expression in mesenchymal stem cells using reiterated nuclear localization sequence peptides

BACKGROUND

Mesenchymal stem cells (MSC) are widely regarded as a promising tool for cellular therapy applications, and genetic modification by safe, liposome-based vectors may enhance their therapeutic potential.

METHODS

The present study describes the use of a cationic lipid vector (Lipofectamine 2000) to deliver genes to MSC isolated from a number of species in vitro and determined the characteristics of this vector system in terms of dose, toxicity and the time course of expression. In addition, the optimal use of a nuclear localization sequence (NLS) to enhance gene expression was explored.

RESULTS

Lipofection of human MSC did not adversely affect their ability to differentiate into osteogenic- and adipogenic lineages. Although human and rat MSC were found to take up lipoplexes with relative efficiency, lower levels of gene expression were detected in rabbit MSC, demonstrating a crucial effect of species. Peptides containing reiterated motifs of NLS were found to significantly improve on the level of transgene expression. Optimal gene delivery was observed when a three-fold reiterated NLS sequence was included in the liposome formulation.

CONCLUSIONS

Thus, nonviral gene delivery to MSC is feasible with efficiency being species dependent and can be enhanced by use of a three-fold reiterated NLS.

Reducible poly(oligo-D-arginine) for enhanced gene expression in mouse lung by intratracheal injection

Nonarginine (D-R9) has been reported to be one of the most efficacious protein transduction domains (PTDs) for the intracellular cargo delivery such as DNA, RNA, proteins, and particles. Although oligoarginines are capable of forming polyplex with DNA by electrostatic interaction, the length of oligoarginine can affect the toxicity and gene expression. The reducible poly(oligo-D-arginine) (rPOA) composed of the Cys-(D-R9)-Cys repeating unit forming disulfide bonds between terminal cysteinyl-thiol groups of short peptides was hypothesized to show efficient gene transfection without toxicity. The reducible high molecular weight poly(oligo-D-arginine) may fragment into the Cys-(D-R9)-Cys in cellular environments such as cytosol, cell surface, endosomes, and lysosomes, and enhance DNA transfection efficiency. In the present study, in vitro stability, cytotoxicity, and transfection efficiency of DNA/poly(oligo-D-arginine) polyplex were evaluated. In addition, in vivo delivery of DNA into the lung was performed by intratracheal injection of DNA/poly(oligo-D-arginine) polyplex. The in vivo study with rPOA showed higher level of gene expression than PEI, sustaining for 1 week without toxicity. Reducible high molecular weight poly(oligo-D-arginine) based on R9 PTD is a very promising nonviral gene carrier for lung diseases by efficiently condensing, stabilizing, and transfecting DNA.

Nanotechnology approaches for gene transfer

In both basic research as well as experimental gene therapy the need to transfer genetic material into a cell is of vital importance. The cellular compartment, which is the target for the genetic material, depends upon application. An siRNA that mediates silencing is preferably delivered to the cytosol while a transgene would need to end up in the nucleus for successful transcription to occur. Furthermore the ability to regulate gene expression has grown substantially since the discovery of RNA interference. In such diverse fields as medical research and agricultural pest control, the capability to alter the genetic output has been a useful tool for pushing the scientific frontiers. This review is focused on nanotechnological approaches to assemble optimised structures of nucleic acid derivatives to facilitate gene delivery as well as promoting down regulation of endogenous genes.