Current progress in gene delivery technology based on chemical methods and nano-carriers

Poly(ester amine) constructed from polyethylenimine and pluronic for gene delivery in vitro and in vivo

A series of poly (ester amines) (PEAs) constructed from low molecular weight polyethyleneimine (LPEI, Mw: 0.8k, 1.2k Da) and Pluronic (different molecular weight (Mw) and hydrophilic-lipophilic-balance (HLB)) components were synthesized, and evaluated in vitro and in vivo as gene delivery carriers. Most PEA polymers were able to bind and condense plasmid DNA effectively into particles of approximately 150 nm in solution at the polymer/DNA ratio of 5 and above. Transfection efficiency of the PEA polymers depends on particle size of the polymer/DNA complex, molecular weight and HLB of the Pluronics and the size of PEI within PEA composition, as well as the cell type. Significant improvement in gene delivery efficacy was achieved with PEA01/04/05 composed of Pluronic size (Mw: 3000-5000 Da), and HLB (12-18) in CHO, C2C12 and HSkM cell lines; and the effective transfection was reflected with PEA 01/04/07 composed of Pluronics with size (2000-5000 Da) and HLB (12-23) in mdx mice. The best formulation for pDNA delivery was obtained with PEA 01 producing transgene expression efficiency 5, 19-folds of that of PEI 25k in vitro and in vivo, respectively. These results potent some of these PEA polymers as attractive vehicles for gene or oligonucleotide delivery.

Bioreducible Fluorinated Peptide Dendrimers Capable of Circumventing Various Physiological Barriers for Highly Efficient and Safe Gene Delivery

Polymeric vectors have shown great promise in the development of safe and efficient gene delivery systems; however, only a few have been developed in clinical settings due to poor transport across multiple physiological barriers. To address this issue and promote clinical translocation of polymeric vectors, a new type of polymeric vector, bioreducible fluorinated peptide dendrimers (BFPDs), was designed and synthesized by reversible cross-linking of fluorinated low generation peptide dendrimers. Through masterly integration all of the features of reversible cross-linking, fluorination, and polyhedral oligomeric silsesquioxane (POSS) core-based peptide dendrimers, this novel vector exhibited lots of unique features, including (i) inactive surface to resist protein interactions; (ii) virus-mimicking surface topography to augment cellular uptake; (iii) fluorination-mediated efficient cellular uptake, endosome escape, cytoplasm trafficking, and nuclear entry, and (iv) disulfide-cleavage-mediated polyplex disassembly and DNA release that allows efficient DNA transcription. Noteworthy, all of these features are functionally important and can synergistically facilitate DNA transport from solution to the nucleus. As a consequences, BFPDs showed excellent gene transfection efficiency in several cell lines (∼95% in HEK293 cells) and superior biocompatibility compared with polyethylenimine (PEI). Meanwhile BFPDs provided excellent serum resistance in gene delivery. More importantly, BFPDs offer considerable in vivo gene transfection efficiency (in muscular tissues and in HepG2 tumor xenografts), which was approximately 77-fold higher than that of PEI in luciferase activity. These results suggest bioreducible fluorinated peptide dendrimers are a new class of highly efficient and safe gene delivery vectors and should be used in clinical settings.

Polyethyleneimine-modified calcium carbonate nanoparticles for p53 gene delivery

In this study, calcium carbonate (CaCO3) nanoparticles with spherical structure were regulated by arginine and successfully synthesized via a facile co-precipitation method. The average particle size of as-prepared CaCO3 was about 900 nm. The properties of nanostructured CaCO3 particles were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction and size distribution. After modified with polyethyleneimine (PEI), the ability of PEI-CaCO3 nanoparticles to carry GFP-marked p53 gene (pEGFP-C1-p53) into cancer cells to express P53 protein were studied. Meanwhile, the cytotoxicity, transfection efficiency, cells growth inhibition and the ability to induce apoptosis by expressed P53 protein were conducted to evaluate the performances of PEI-CaCO3 nanoparticles. The results show that prepared PEI-CaCO3 nanoparticles had good biocompatibility and low cytotoxicity in a certain concentration range. PEI-CaCO3 effectively transfected pEGFP-C1 gene into epithelial-like cancer cells. And with the expression of GFP-P53 fusion protein, pEGFP-C1-p53-gene-loaded PEI-CaCO3 particles significantly reduced the proliferation of cancer cells. These findings indicate that our PEI-modified CaCO3 nanoparticles are potential to be successfully used as carriers for gene therapy.

[Effect of MT01/PEN complexes on the expression of osteoprotegerin and receptor activator of nuclear factor κB ligand in human osteoblast-like cell line MG63]

OBJECTIVE

This study aims to synthesize MTO1 (a kind of oligodeoxynucleotides) and N-isopropylacrylamide-modified polyethylenimines (PEN) complexes (MT01/PEN) as well as to investigate the effect of the complexes on the expression of osteoprotegerin (OPG) and the receptor activator of nuclear factor κB ligand (RANKL) in the human osteoblast-like cell line MG63.

METHODS

MG63 cells were transfected by MT01/PEN complexes formed with three different mass ratios (1:2, 1:4, 1:6) of MT01 to PEN. MT01 and MT01-s were used as positive control. Enzyme-linked immunosorbent assay and real-time polymerase chain reaction were performed to estimate the amount of OPG and RANKL released into the culture media and in MG63 at 24, 48, 72 h.

RESULTS

MG63 responded to the MT01/PEN complexes by significantly upregulating the OPG on the protein and mRNA levels (P < 0.05). The protein and mRNA levels of RANKL were lower in most of the groups with complexes, and the OPG/RANKL ratio were higher (P < 0.05). MG63 were affected by the MT01/PEN complexes with different mass ratios, particularly when the ratio was 1:6.

CONCLUSION

MT01 can enhance the promotion of ossification by establishing the delivery system with PEN.

Vectors and strategies for nonviral cancer gene therapy

INTRODUCTION

This review presents recent developments in the use of nonviral vectors and transfer technologies in cancer gene therapy. Tremendous progress has been made in developing cancer gene therapy in ways that could be applicable to treatments. Numerous efforts are focused on methods of attacking known and novel targets more efficiently and specifically. In parallel to progress in nonviral vector design and delivery technologies, important achievements have been accomplished for suicide, gene replacement, gene suppression and immunostimulatory therapies. New nonviral cancer gene therapies have been developed based on emerging RNAi (si/shRNA-, miRNA) or ODN.

AREAS COVERED

This review provides an overview of recent gene therapeutic strategies in which nonviral vectors have been used experimentally and in clinical trials. Furthermore, we present current developments in nonviral vector systems in association with important chemical and physical gene delivery technologies and their potential for the future.

EXPERT OPINION

Nonviral gene therapy has maintained its position as an approach for treating cancer. This is reflected by the fact that more than 17% of all gene therapy trials employ nonviral approaches. Thus, nonviral vectors have emerged as a clinical alternative to viral vectors for the appropriate expression and delivery of therapeutic genes.

Chitosan-based core-shell structured particles for in vivo sustainable gene transfection

A core-shell structured chitosan (CS)-based gene vector with a sustainable gene transfection effect was designed and successfully prepared in this study. The pEGFP was first combined with the thiolated and N-alkylated chitosan (TACS). Then, hydroxybutyl chitosan grafted with poly(ethylene glycol) (EG-HBC) was coated on the pEGFP-loaded TACS particles. The prepared pEGFP-loaded TACS@EG-HBC particles have a size of about 200 nm and little cytotoxicity. The in vitro and in vivo gene transfection experiments indicate that the pEGFP-loaded TACS@EG-HBC particles possess a better sustainable gene transfection capacity and a high transfection efficiency, which should be attributed to the biodegradation of the CS-based shell, the thiolation and N-alkylation modification on CS cores, and the grafted PEG chains with better biocompatibility. The in vivo gene expression of the loaded pEGFP can persist up to 60 days. This novel gene vector has a theoretical and practical significance for gene therapy with sustained transfection effect.

Histone-inspired biomimetic polymeric gene vehicles with excellent biocompatibility and enhanced transfection efficacy

Histone-inspired biomimetic polymeric gene vectors show great biocompatibility and enhanced transfection efficacy.

Synthesis, characterization and evaluation of diglycidyl-1,2-cyclohexanedicarboxylate crosslinked polyethylenimine nanoparticles as efficient carriers of DNA

Crosslinked PEI nanoparticles were synthesized, which efficiently transported DNA inside the cells with minimal cytotoxicity.

Synthesis of amine-polyglycidol functionalised Fe3O4@SiO2nanocomposites for magnetic hyperthermia, pH-responsive drug delivery, and bioimaging applications

We report the biocompatible Fe₃O₄@SiO₂@APG-F nanocomposite for drug delivery and hyperthermia applications. The Fe₃O₄@SiO₂@APG-F nanocomposite could serve as a good hyperthermia agent, drug delivery carrier, and fluorescent contrast agent.

Engineered non-toxic cationic nanocarriers with photo-triggered slow-release properties

A simple and versatile strategy using cationic amphiphilic diblock copolymers synthesized by a combination of ATRP and post-polymerization quaternization to prepare photo-responsive nanocarriers showing slow-release properties and low cytotoxicity was reported.

Tri-membrane nanoparticles produced by combining liposome fusion and a novel patchwork of bicelles to overcome endosomal and nuclear membrane barriers to cargo delivery

Tri-membrane PD-MEND deliver cargo by sophisticated membrane fusions.

Screening PEGylated polyethylenimine derivatives for safe and efficient delivery of gene materials

PEG–Et 1 : 1 was screened out for the safe and efficient gene delivery by precise design of PEGylated polymeric nanomaterials.

Interaction Of Calcium Phosphate Nanoparticles With Human Chorionic Gonadotropin Modifies Secondary And Tertiary Protein Structure

Calcium phosphate nanoparticles (CaPNP) have good biocompatibility and bioactivity inside human body. In this study, the interaction between CaPNP and human chorionic gonadotropin (hCG) was analyzed to determine the changes in the protein structure in the presence of CaPNP and the quantity of protein adsorbed on the CaPNP surface. The results showed a significant adsorption of hCG on the CaPNP nanoparticle surface. The optimal fit was achieved using the Sips isotherm equation with a maximum adsorption capacity of 68.23 µg/mg. The thermodynamic parameters, including ∆H° and ∆G°, of the adsorption process are positive, whereas ∆S° is negative. The circular dichroism results of the adsorption of hCG on CaPNP showed the changes in its secondary structure; such changes include the decomposition of α-helix strand and the increase in β-pleated sheet and random coil percentages. Fluorescence study indicated minimal changes in the tertiary structure near the microenvironment of the aromatic amino acids such as tyrosine and phenyl alanine caused by the interaction forces between the CaPNP and hCG protein. The desorption process showed that the quantity of the hCG desorbed significantly increases as temperature increases, which indicates the weak forces between hCG and the surface.

Chlorotoxin-Conjugated Multifunctional Dendrimers Labeled with Radionuclide 131I for Single Photon Emission Computed Tomography Imaging and Radiotherapy of Gliomas

Chlorotoxin-conjugated multifunctional dendrimers labeled with radionuclide 131I were synthesized and utilized for targeted single photon emission computed tomography (SPECT) imaging and radiotherapy of cancer. In this study, generation five amine-terminated poly(amidoamine) dendrimers were used as a platform to be sequentially conjugated with polyethylene glycol (PEG), targeting agent chlorotoxin (CTX), and 3-(4'-hydroxyphenyl)propionic acid-OSu (HPAO). This was followed by acetylation of the remaining dendrimer terminal amines and radiolabeling with 131I to form the targeted theranostic dendrimeric nanoplatform. We show that the dendrimer platform possessing approximately 7.7 CTX and 21.1 HPAO moieties on each dendrimer displays excellent cytocompatibility in a given concentration range (0-20 μM) and can specifically target cancer cells overexpressing matrix metallopeptidase 2 (MMP2) due to the attached CTX. With the attached HPAO moiety having the phenol group, the dendrimer platform can be effectively labeled with radioactive 131I with good stability and high radiochemical purity. Importantly, the 131I labeling renders the dendrimer platform with an ability to be used for targeted SPECT imaging and radiotherapy of an MMP2-overexpressing glioma model in vivo. The developed radiolabeled multifunctional dendrimeric nanoplatform may hold great promise to be used for targeted theranostics of human gliomas.

Synthesis of efficient gene delivery systems by grafting pegylated alkylcarboxylate chains to PAMAM dendrimers: Evaluation of transfection efficiency and cytotoxicity in cancerous and mesenchymal stem cells

The applications of polyamidoamine (PAMAM) dendrimers have attracted much attention in biomedicine specially non-viral gene delivery because of thier unique characteristics including hyperbranching, multivalency, and well-defined uniform globular three-dimensional structures. In the current study, in order to enhance the transfection efficiency and reduce the cytotoxicity of PAMAMs, bromoalkylcarboxylates with different chain length (2-bromoacetic, 6-bromohexanoic, 10-bromodecanoic and 16-bromohexadecanoic acids) were covalently conjugated with 10% and 30% of primary amines of generation 4 and 5 (G4 and G5) of PAMAM dendrimers to increase the hydrophobicity of the carrier. At the next stage, the alkylcarboxylate-PAMAMs were pegylaed to further modify the PAMAM structures for biological applications. Obtained results demonstrated that the prepared PAMAM derivatives had particle size around 140 nm with net-positive surface charge. None of the prepared PAMAM-based non-viral vactors exhibited significant hemolytic activity and also cytotoxicity. Meanwhile decahexanoate–PAMAM G4 [G4(16C-10%)] and decanoate–PAMAM G4 conjugated to polyethylene glycol (PEG) (G4[(10C-30%)(10C-PEG)]) showed highest transfection efficiency in murine neuroblastoma (Neuro-2a) cell line, interestingly only the latter had improved transfection efficiency in mesenchymal stem cells (MSCs). This study proved the potential utility of alkylcarboxylate-grafted PAMAM dendrimers (G4 and G5) with or without PEG modification for efficient gene transfer into cancerous cells as well as MSCs.

A Disposable Microfluidic Device for Controlled Drug Release from Thermal-Sensitive Liposomes by High Intensity Focused Ultrasound

The drug release triggered thermally by high intensity focused ultrasound (HIFU) has been considered a promising drug delivery strategy due to its localized energy and non-invasive characters. However, the mechanism underlying the HIFU-mediated drug delivery remains unclear due to its complexity at the cellular level. In this paper, micro-HIFU (MHIFU) generated by a microfluidic device is introduced which is able to control the drug release from temperature-sensitive liposomes (TSL) and evaluate the thermal and mechanical effects of ultrasound on the cellular drug uptake and apoptosis. By simply adjusting the input electrical signal to the device, the temperature of sample can be maintained at 37 °C, 42 °C and 50 °C with the deviation of ± 0.3 °C as desired. The flow cytometry results show that the drug delivery under MHIFU sonication leads to a significant increase in apoptosis compared to the drug release by incubation alone at elevated temperature of 42 °C. Furthermore, increased squamous and protruding structures on the surface membrane of cells were detected by atomic force microscopy (AFM) after MHIFU irradiation of TSL. We demonstrate that compared to the routine HIFU treatment, MHIFU enables monitoring of in situ interactions between the ultrasound and cell in real time. Furthermore, it can quantitatively analyze and characterize the alterations of the cell membrane as a function of the treatment time.

Specific in vivo knockdown of protein function by intrabodies

Intracellular antibodies (intrabodies) are recombinant antibody fragments that bind to target proteins expressed inside of the same living cell producing the antibodies. The molecules are commonly used to study the function of the target proteins (i.e., their antigens). The intrabody technology is an attractive alternative to the generation of gene-targeted knockout animals, and complements knockdown techniques such as RNAi, miRNA and small molecule inhibitors, by-passing various limitations and disadvantages of these methods. The advantages of intrabodies include very high specificity for the target, the possibility to knock down several protein isoforms by one intrabody and targeting of specific splice variants or even post-translational modifications. Different types of intrabodies must be designed to target proteins at different locations, typically either in the cytoplasm, in the nucleus or in the endoplasmic reticulum (ER). Most straightforward is the use of intrabodies retained in the ER (ER intrabodies) to knock down the function of proteins passing the ER, which disturbs the function of members of the membrane or plasma proteomes. More effort is needed to functionally knock down cytoplasmic or nuclear proteins because in this case antibodies need to provide an inhibitory effect and must be able to fold in the reducing milieu of the cytoplasm. In this review, we present a broad overview of intrabody technology, as well as applications both of ER and cytoplasmic intrabodies, which have yielded valuable insights in the biology of many targets relevant for drug development, including α-synuclein, TAU, BCR-ABL, ErbB-2, EGFR, HIV gp120, CCR5, IL-2, IL-6, β-amyloid protein and p75NTR. Strategies for the generation of intrabodies and various designs of their applications are also reviewed.

Cardiac gene therapy: Recent advances and future directions

Gene therapy has the potential to serve as an adaptable platform technology for treating various diseases. Cardiovascular disease is a major cause of mortality in the developed world and genetic modification is steadily becoming a more plausible method to repair and regenerate heart tissue. Recently, new gene targets to treat cardiovascular disease have been identified and developed into therapies that have shown promise in animal models. Some of these therapies have advanced to clinical testing. Despite these recent successes, several barriers must be overcome for gene therapy to become a widely used treatment of cardiovascular diseases. In this review, we evaluate specific genetic targets that can be exploited to treat cardiovascular diseases, list the important delivery barriers for the gene carriers, assess the most promising methods of delivering the genetic information, and discuss the current status of clinical trials involving gene therapies targeted to the heart.

Independent effect of polymeric nanoparticle zeta potential/surface charge, on their cytotoxicity and affinity to cells

OBJECTIVES

Up to now, little research has been focussed on discovering how zeta potential independently affects polymeric nanoparticle (NP) cytotoxicity.

METHODS

Polymeric nanoparticles of gradient zeta potential ranging from -30 mv to +40 mv were fabricated using the same poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHHx) biopolymer. Interaction forces between nanoparticles and cells were measured by atomic force microscopy (AFM). Cytotoxicity of the nanoparticles to cells was investigated by using MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay.

RESULTS

Four kinds of nanoparticle with similar sizes and gradient zeta potentials, were fabricated. Those with positive surface charges were found to be more toxic than those with negative surface charges. Positively charged nanoparticles or nanoparticles with higher 'like' charges, offered higher interaction force with cells.

CONCLUSION

This work proposes a novel approach for investigating interaction between NPs and cells, and discloses the importance of controlling zeta potential in developing NPs-based formulations in the future.

Polycation-mediated integrated cell death processes

One of the major challenges in the field of nucleic acid delivery is the design of delivery vehicles with attributes that render them safe as well as efficient in transfection. To this end, polycationic vectors have been intensely investigated with native polyethylenimines (PEIs) being the gold standard. PEIs are highly efficient transfectants, but depending on their architecture and size they induce cytotoxicity through different modes of cell death pathways. Here, we briefly review dynamic and integrated cell death processes and pathways, and discuss considerations in cell death assay design and their interpretation in relation to PEIs and PEI-based engineered vectors, which are also translatable for the design and studying the safety of other transfectants.

Azobenzene-aminoglycoside: Self-assembled smart amphiphilic nanostructures for drug delivery

Here, we have designed and synthesized a novel cationic amphiphilic stimuli-responsive azobenzene-aminoglycoside (a small molecule) conjugate, Azo-AG 5, and characterized it by UV and FTIR. Light responsive nature of Azo-AG 5 was assessed under UV-vis light. Self- assembly of Azo-AG 5 in aqueous solutions into nanostructures and their ability to act as drug carrier were also investigated. The nanostructures of Azo-AG 5 showed average hydrodynamic diameter of ∼ 255 nm with aminoglycoside moiety (neomycin) and 4-dimethylaminoazobenzene forming hydrophilic shell and hydrophobic core, respectively. In the hydrophobic core, eosin and aspirin were successfully encapsulated. Dynamic light scattering (DLS) measurements demonstrated that the nanoassemblies showed expansion and contraction on successive UV and visible light irradiations exhibiting reversible on-off switch for controlling the drug release behavior. Similar behavior was observed when these nanostructures were subjected to pH-change. In vitro drug release studies showed a difference in UV and visible light-mediated release pattern. It was observed that the release rate under UV irradiation was comparatively higher than that observed under visible light. Further, azoreductase-mediated cleavage of the azo moiety in Azo-AG 5 nanoassemblies resulted in the dismantling of the structures into aggregated microstructures. Azo-AG 5 nanostructures having positive surface charge (+9.74 mV) successfully interacted with pDNA and retarded its mobility on agarose gel. Stimuli responsiveness of nanostructures and their on-off switch like behavior ensure the great potential as controlled drug delivery systems and in other biomedical applications such as colon-specific delivery and gene delivery.

Liver-targeted gene therapy: Approaches and challenges

The liver plays a major role in many inherited and acquired genetic disorders. It is also the site for the treatment of certain inborn errors of metabolism that do not directly cause injury to the liver. The advancement of nucleic acid-based therapies for liver maladies has been severely limited because of the myriad untoward side effects and methodological limitations. To address these issues, research efforts in recent years have been intensified toward the development of targeted gene approaches using novel genetic tools, such as zinc-finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats as well as various nonviral vectors such as Sleeping Beauty transposons, PiggyBac transposons, and PhiC31 integrase. Although each of these methods uses a distinct mechanism of gene modification, all of them are dependent on the efficient delivery of DNA and RNA molecules into the cell. This review provides an overview of current and emerging therapeutic strategies for liver-targeted gene therapy and gene repair.

Arginine-rich polyplexes for gene delivery to neuronal cells

Neuronal gene therapy potentially offers an effective therapeutic intervention to cure or slow the progression of neurological diseases. However, neuronal cells are difficult to transfect with nonviral vectors, and in vivo their transport across the blood-brain barrier (BBB) is inefficient. We synthesized a series of arginine-rich oligopeptides, grafted with polyethyleneimine (PEI) and modified with a short-chain polyethylene glycol (PEG). We hypothesized that the arginine would enhance cellular uptake and transport of these polyplexes across the BBB, with PEG imparting biocompatibility and "stealth" properties and PEI facilitating DNA condensation and gene transfection. The optimized composition of the polyplexes demonstrated hemocompatibility with red blood cells, causing no lysis or aggregation, and showed significantly better cytocompatibility than PEI in vitro. Polyplexes formulated with luciferase-expressing plasmid DNA could transfect rat primary astrocytes and neurons in vitro. Confocal imaging data showed efficient cellular uptake of DNA and its sustained intracellular retention and nuclear localization with polyplexes. Intravenous administration of the optimized polyplexes in mice led to gene expression in the brain, which upon further immunohistochemical analysis demonstrated gene expression in neurons. In conclusion, we have successfully designed a nonviral vector for in vitro and in vivo neuronal gene delivery.

Toward an effective strategy in glioblastoma treatment. Part II: RNA interference as a promising way to sensitize glioblastomas to temozolomide

RNA interference (RNAi) is a strategy of gene regulation that has opened up many opportunities for the treatment of cancers, especially glioblastoma multiforme (GBM). This strategy reduced the expression of many proteins involved in the resistance of these tumors to anticancer drugs, particularly to temozolomide (TMZ). A significant research effort has gone into RNAi delivery and target selection for clinical application of this new discovery in the treatment of GBMs. However, some limitations must be resolved to enhance the safety of RNAi-based therapeutics and to reduce their immune response. In this review, the mechanism of RNAi will be described. Moreover, the opportunities offered by RNAi strategy to reverse the phenotype of these tumor cells as well as prospects and challenges ahead in the RNAi-based therapy will be discussed.

Delivery of episomal vectors into primary cells by means of commercial transfection reagents

Although episomal vectors are commonly transported into cells by electroporation, a number of electroporation-derived problems have led to the search for alternative transfection protocols, such as the use of transfection reagents, which are inexpensive and easy to handle. Polyplex-mediated transport of episomal vectors into the cytoplasm has been conducted successfully in immortalized cell lines, but no report exists of successful transfection of primary cells using this method. Accordingly, we sought to optimize the conditions for polyplex-mediated transfection for effective delivery of episomal vectors into the cytoplasm of primary mouse embryonic fibroblasts. Episomal vectors were complexed with the commercially available transfection reagents Lipofectamine 2000, FuGEND HD and jetPEI. The ratio of transfection reagent to episomal vectors was varied, and the subsequent transfection efficiency and cytotoxicity of the complexes were analyzed using flow cytometry and trypan blue exclusion assay, respectively. No cytotoxicity and the highest transfection yield were observed when the ratio of transfection reagent to episomal vector was 4 (v/wt) in the cases of Lipofectamine 2000 and FuGENE HD, and 2 in the case of jetPEI. Of the three transfection reagents tested, jetPEI showed the highest transfection efficiency without any cytotoxicity. Thus, we confirmed that the transfection reagent jetPEI could be used to effectively deliver episomal vectors into primary cells without electroporation.

Novel cholesterol-based cationic lipids as transfecting agents of DNA for efficient gene delivery

The design, synthesis and biological evaluation of the cationic lipid gene delivery vectors based on cholesterol and natural amino acids lysine or histidine are described. Cationic liposomes composed of the newly synthesized cationic lipids 1a or 1b and neutral lipid DOPE (1,2-dioleoyl-l-α-glycero-3-phosphatidyl-ethanolamine) exhibited good transfection efficiency. pEGFP-N₁ plasmid DNA was transferred into 293T cells by cationic liposomes formed from cationic lipids 1a and 1b, and the transfection activity of the cationic lipids was superior (1a) or parallel (1b) to that of the commercially available 3β-[N-(N',N'-dimethylaminoethyl)-carbamoyl] cholesterol (DC-Chol) derived from the same cholesterol backbone with different head groups. Combined with the results of agarose gel electrophoresis, transfection experiments with various molar ratios of the cationic lipids and DOPE and N/P (+/−) molar charge ratios, a more effective formulation was formed, which could lead to relatively high transfection efficiency. Cationic lipid 1a represents a potential agent for the liposome used in gene delivery due to low cytotoxicity and impressive gene transfection activity.

Gene therapeutic approaches to inhibit hepatitis B virus replication

Acute and chronic hepatitis B virus (HBV) infections remain to present a major global health problem. The infection can be associated with acute symptomatic or asymptomatic hepatitis which can cause chronic inflammation of the liver and over years this can lead to cirrhosis and the development of hepatocellular carcinomas. Currently available therapeutics for chronically infected individuals aim at reducing viral replication and to slow down or stop the progression of the disease. Therefore, novel treatment options are needed to efficiently combat and eradicate this disease. Here we provide a state of the art overview of gene therapeutic approaches to inhibit HBV replication. We discuss non-viral and viral approaches which were explored to deliver therapeutic nucleic acids aiming at reducing HBV replication. Types of delivered therapeutic nucleic acids which were studied since many years include antisense oligodeoxynucleotides and antisense RNA, ribozymes and DNAzymes, RNA interference, and external guide sequences. More recently designer nucleases gained increased attention and were exploited to destroy the HBV genome. In addition we mention other strategies to reduce HBV replication based on delivery of DNA encoding dominant negative mutants and DNA vaccination. In combination with available cell culture and animal models for HBV infection, in vitro and in vivo studies can be performed to test efficacy of gene therapeutic approaches. Recent progress but also challenges will be specified and future perspectives will be discussed. This is an exciting time to explore such approaches because recent successes of gene therapeutic strategies in the clinic to treat genetic diseases raise hope to find alternative treatment options for patients chronically infected with HBV.

Bioreducible polyethylenimine nanoparticles for the efficient delivery of nucleic acids

Electrostatically crosslinked bioreducible nanoparticles of polyethylenimine (DP NPs) have been prepared and evaluated for their cytotoxicity and capability to transport nucleic acids inside the cells.

Multi-arm carriers composed of an antioxidant lignin core and poly(glycidyl methacrylate-co-poly(ethylene glycol)methacrylate) derivative arms for highly efficient gene delivery

A lignin-based copolymer with good biocompability was successfully prepared via atom transfer radical polymerization (ATRP) for efficient gene delivery.

Non viral vectors in gene therapy- an overview

Non-viral vectors are simple in theory but complex in practice. Apart from intra cellular and extracellular barriers, number of other challenges also needs to be overcome in order to increase the effectiveness of non-viral gene transfer. These barriers are categorized as production, formulation and storage. No one-size-fits-all solution to gene delivery, which is why in spite of various developments in liposome, polymer formulation and optimization, new compounds are constantly being proposed and investigated. In this review, we will see in detail about various types of non-viral vectors highlighting promising development and recent advances that had improved the non-viral gene transfer efficiency of translating from "Bench to bedside".

Gene therapy and imaging in preclinical and clinical oncology: recent developments in therapy and theranostics

In the case of disseminated cancer, current treatment options reach their limit. Gene theranostics emerge as an innovative route in the treatment and diagnosis of cancer and might pave the way towards development of an efficacious treatment of currently incurable cancer. Various gene vectors have been developed to realize tumor-specific nucleic acid delivery and are considered crucial for the successful application of cancer gene therapy. By adding reporter genes and imaging agents, these systems gain an additional diagnostic function, thereby advancing the theranostic paradigm into cancer gene therapy. Numerous preclinical studies have demonstrated the feasibility of combined tumor gene therapy and diagnostic imaging, and clinical trials in human and veterinary oncology have been executed with partly encouraging results.

State-of-the-art human gene therapy: part I. Gene delivery technologies

Safe and effective gene delivery is a prerequisite for successful gene therapy. In the early age of human gene therapy, setbacks due to problematic gene delivery vehicles plagued the exciting therapeutic outcome. However, gene delivery technologies rapidly evolved ever since. With the advancement of gene delivery techniques, gene therapy clinical trials surged during the past decade. As the first gene therapy product (Glybera) has obtained regulatory approval and reached clinic, human gene therapy finally realized the promise that genes can be medicines. The diverse gene delivery techniques available today have laid the foundation for gene therapy applications in treating a wide range of human diseases. Some of the most urgent unmet medical needs, such as cancer and pandemic infectious diseases, have been tackled by gene therapy strategies with promising results. Furthermore, combining gene transfer with other breakthroughs in biomedical research and novel biotechnologies opened new avenues for gene therapy. Such innovative therapeutic strategies are unthinkable until now, and are expected to be revolutionary. In part I of this review, we introduced recent development of non-viral and viral gene delivery technology platforms. As cell-based gene therapy blossomed, we also summarized the diverse types of cells and vectors employed in ex vivo gene transfer. Finally, challenges in current gene delivery technologies for human use were discussed.

HAI-178 antibody-conjugated fluorescent magnetic nanoparticles for targeted imaging and simultaneous therapy of gastric cancer

The successful development of safe and highly effective nanoprobes for targeted imaging and simultaneous therapy of in vivo gastric cancer is a great challenge. Herein we reported for the first time that anti-α-subunit of ATP synthase antibody, HAI-178 monoclonal antibody-conjugated fluorescent magnetic nanoparticles, was successfully used for targeted imaging and simultaneous therapy of in vivo gastric cancer. A total of 172 specimens of gastric cancer tissues were collected, and the expression of α-subunit of ATP synthase in gastric cancer tissues was investigated by immunohistochemistry method. Fluorescent magnetic nanoparticles were prepared and conjugated with HAI-178 monoclonal antibody, and the resultant HAI-178 antibody-conjugated fluorescent magnetic nanoparticles (HAI-178-FMNPs) were co-incubated with gastric cancer MGC803 cells and gastric mucous GES-1 cells. Gastric cancer-bearing nude mice models were established, were injected with prepared HAI-178-FMNPs via tail vein, and were imaged by magnetic resonance imaging and small animal fluorescent imaging system. The results showed that the α-subunit of ATP synthase exhibited high expression in 94.7% of the gastric cancer tissues. The prepared HAI-178-FMNPs could target actively MGC803 cells, realized fluorescent imaging and magnetic resonance imaging of in vivo gastric cancer, and actively inhibited growth of gastric cancer cells. In conclusion, HAI-178 antibody-conjugated fluorescent magnetic nanoparticles have a great potential in applications such as targeted imaging and simultaneous therapy of in vivo early gastric cancer cells in the near future.

Exploitation of viral properties for intracellular delivery

Nanotechnology is an expanding area of study with potentially pivotal applications in a discipline as medicine where new biomedical active molecules or strategies are continuously developing. One of the principal drawbacks for the application of new therapies is the difficulty to cross membranes that represent the main physiological barrier in our body and in all living cells. Membranes are selectively permeable and allow the selective internalization of substances; generally, they form a highly impermeable barrier to most polar and charged molecules, and represent an obstacle for drug delivery, limiting absorption to specific routes and mechanisms. Viruses provide attracting suggestions for the development of targeted drug carriers as they have evolved naturally to deliver their genomes to host cells with high fidelity.

A detailed understanding of virus structure and their mechanisms of entry into mammalian cells will facilitate the development and analysis of virus‐based materials for medical applications. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.

A sight on the current nanoparticle-based gene delivery vectors

Nowadays, gene delivery for therapeutic objects is considered one of the most promising strategies to cure both the genetic and acquired diseases of human. The design of efficient gene delivery vectors possessing the high transfection efficiencies and low cytotoxicity is considered the major challenge for delivering a target gene to specific tissues or cells. On this base, the investigations on non-viral gene vectors with the ability to overcome physiological barriers are increasing. Among the non-viral vectors, nanoparticles showed remarkable properties regarding gene delivery such as the ability to target the specific tissue or cells, protect target gene against nuclease degradation, improve DNA stability, and increase the transformation efficiency or safety. This review attempts to represent a current nanoparticle based on its lipid, polymer, hybrid, and inorganic properties. Among them, hybrids, as efficient vectors, are utilized in gene delivery in terms of materials (synthetic or natural), design, and in vitro/in vivo transformation efficiency.

Novel serum-tolerant lipoplexes target the folate receptor efficiently

Gene transfer using non-viral vectors is a promising approach for the safe delivery of nucleic acid therapeutics. In this study, we investigate a lipid-based system for targeted gene delivery to malignant cells overexpressing the folate receptor (FR). Cationic liposomes were formulated with and without the targeting ligand folate conjugated to distearoylphosphatidyl ethanolamine polyethylene glycol 2000 (DSPE-PEG2000), the novel cytofectin 3β[N(N(1),N(1)-dimethlaminopropylsuccinamidoethane)-carbamoyl]cholesterol (SGO4), which contains a 13atom, 15Å spacer element, and the helper lipid, dioleoylphosphatidylethanolamine (DOPE). Physicochemical parameters of the liposomes and lipoplexes were obtained by zeta sizing, zeta potential measurement and cryo-TEM. DNA-binding and protection capabilities of liposomes were confirmed by gel retardation assays, EtBr intercalation and nuclease protection assays. The complexes were assessed in an in vitro system for their effect on cell viability using the MTT assay, and gene transfection activity using the luciferase assay in three cell lines; HEK293 (FR-negative), HeLa (FR(+)-positive), KB (FR(++)-positive). Low cytotoxicities were observed in all cell lines, while transgene activity promoted by folate-tagged lipoplexes in FR-positive lines was tenfold greater than that by untargeted constructs and cell entry by folate complexes was demonstrably by FR mediation. These liposome formulations have the design capacity for in vivo application and may therefore be promising candidates for further development.

Synthesis and evaluation of tetramethylguanidinium-polyethylenimine polymers as efficient gene delivery vectors

Previously, we demonstrated that 6-(N,N,N',N'-tetramethylguanidinium chloride)-hexanoyl-polyethylenimine (THP) polymers exhibited significantly enhanced transfection efficiency and cell viability. Here, in the present study, we have synthesized a series of N,N,N',N'-tetramethylguanidinium-polyethylenimine (TP1-TP5) polymers via a single-step reaction involving peripheral primary amines of bPEI and varying amounts of 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU). These polymers were found to interact efficiently with negatively charged pDNA and formed stable complexes in the size range of ~240-450 nm. Acid-base titration profiles revealed improved buffering capacity of TP polymers as compared to bPEI. Transfection and cytotoxicity assays performed with TP/pDNA complexes on HEK293, CHO, and HeLa cells showed significantly higher transfection efficiency and cell viability with one of the complexes, TP2/pDNA complex, exhibited the highest transfection efficiency (~1.4-2.3-fold) outcompeting native bPEI and the commercially available transfection reagent, Lipofectamine 2000. Compared to previously reported THP polymers, the transfection efficiency of TP/pDNA complexes was found to be lower, as examined by flow cytometry. These results highlight the importance of the hydrophobic C-6 linker in THP polymers in forming compact nanostructures with pDNA, which might lead to efficient uptake and internalization of the complexes; however, the projected TP polymers offer an advantage of their rapid and economical one-step synthesis.

Multifunctional self-assembled cationic peptide nanostructures efficiently carry plasmid DNA in vitro and exhibit antimicrobial activity with minimal toxicity

An amphiphilic peptide–aminoglycoside (Pep–Neo) conjugate has been synthesized, self-assembled into nanostructures and evaluated for its multifunctional properties.

Oligoamine-tethered low generation polyamidoamine dendrimers as potential nucleic acid carriers

Oligoamine-tethered low generation PAMAM dendrimers (mG2–mG4) have been synthesized, which showed significantly higher transfection efficiency with minimal cytotoxicity in vitro.