Particle bombardment: a universal approach for gene transfer to cells and tissues

Gene Therapy, A Potential Therapeutic Tool for Neurological and Neuropsychiatric Disorders: Applications, Challenges and Future Perspective

Neurological and neuropsychiatric disorders are the main risks for the health care system, exhibiting a huge socioeconomic load. The available range of pharmacotherapeutics mostly provides palliative consequences and fails to treat such conditions. The molecular etiology of various neurological and neuropsychiatric disorders is mostly associated with a change in genetic background, which can be inherited/triggered by other environmental factors. To address such conditions, gene therapy is considered a potential approach claiming a permanent cure of the disease primarily by deletion, silencing, or edition of faulty genes and by insertion of healthier genes. In gene therapy, vectors (viral/nonvial) play an important role in delivering the desired gene to a specific region of the brain. Targeted gene therapy has unraveled opportunities for the treatment of many neurological and neuropsychiatric disorders. For improved gene delivery, the current techniques mainly focus on designing a precise viral vector, plasmid transfection, nanotechnology, microRNA, and in vivo clustered regulatory interspaced short palindromic repeats (CRISPR)-based therapy. These latest techniques have great benefits in treating predominant neurological and neurodevelopmental disorders, including Parkinson's disease, Alzheimer's disease, and autism spectrum disorder, as well as rarer diseases. Nevertheless, all these delivery methods have their limitations, including immunogenic reactions, off-target effects, and a deficiency of effective biomarkers to appreciate the effectiveness of therapy. In this review, we present a summary of the current methods in targeted gene delivery, followed by the limitations and future direction of gene therapy for the cure of neurological and neuropsychiatric disorders.

Entanglement of polymer chains in hypertonic medium enhances the delivery of DNA and other biomacromolecules into cells

HYPOTHESIS

Most experimental procedures applied in modern biology involve cargo delivering into cells. One of the ways to cargo introduction is osmotic-mediated intracellular vesicle swelling. However, its widespread use was hindered due to cargo size (<10 nm) and cell-type-related restrictions. We addressed the issue of the composition of colloidal loading solution to enhance the efficiency of cellular delivery.

EXPERIMENTS

We examined the effectiveness of colloidal loading solutions of varied compositions, including various types and sizes of polymers building osmotic pressure. We used confocal imaging coupled with fluorescence correlation spectroscopy to evaluate the introduction of polymers, proteins, nanoparticles, and DNA plasmids (cargos of sizes 1-175 nm) to cells representing eight cell lines: cancer, normal, epithelial, and mesenchymal ones.

FINDINGS

We found that cellular delivery effectiveness strongly correlates with the size and concentration of osmotic pressure building polymers and not with the high value of the osmotic pressure itself. We show that polymer solutions at the entangled regime of concentrations enhance the delivery of large biomacromolecules even of size 200 nm (DNA plasmids) into cells, including MDA-MB-231 cells - so far resistant to the osmotic procedure. We show that the colloid loading medium based on entangled polymer chains is a versatile cargo delivery tool for molecular biology.

Microfluidic Based Physical Approaches towards Single-Cell Intracellular Delivery and Analysis

The ability to deliver foreign molecules into a single living cell with high transfection efficiency and high cell viability is of great interest in cell biology for applications in therapeutic development, diagnostics, and drug delivery towards personalized medicine. Various physical delivery methods have long demonstrated the ability to deliver cargo molecules directly to the cytoplasm or nucleus and the mechanisms underlying most of the approaches have been extensively investigated. However, most of these techniques are bulk approaches that are cell-specific and have low throughput delivery. In comparison to bulk measurements, single-cell measurement technologies can provide a better understanding of the interactions among molecules, organelles, cells, and the microenvironment, which can aid in the development of therapeutics and diagnostic tools. To elucidate distinct responses during cell genetic modification, methods to achieve transfection at the single-cell level are of great interest. In recent years, single-cell technologies have become increasingly robust and accessible, although limitations exist. This review article aims to cover various microfluidic-based physical methods for single-cell intracellular delivery such as electroporation, mechanoporation, microinjection, sonoporation, optoporation, magnetoporation, and thermoporation and their analysis. The mechanisms of various physical methods, their applications, limitations, and prospects are also elaborated.

Novel nanoplex-mediated plant transformation approach

Here, a rapid and easy transformation by electroporation technique for gene transfer in plants using cell penetrating amino nanocomplex (nanoplex) has been demonstrated in Nicotiana. Nanoplex was prepared using cell penetrating amino acids (CPAs) such as poly-L-lysine (PLL) and Argenine (Arg), in combination with the gold nanoparticles (AuNPs). PLLs-modified nanoplex with zeta potential of 34.2 ± 1.22 mV charge showed 63.3% efficiency for gene transformation in plant cells as compared to 60% when modified with Arg and the zeta potential was found to be 30.0 ± 0.83 mV; whereas, the transformation efficiency without nanoplex was found to be 6.6%. The findings indicate that the zeta potential of positively charged nanocomplex (AuNPs/CPAs/DNA/CPAs) increases the transformation efficiency because of their ability to protect the DNA from electroporation wave and endogenous enzyme damage. Transformation was confirmed by GUS assay and amplification of npt gene. This technique may open up new possibilities of gene transfer in plants, which will enable to produce large number of transgenic plants.

Intracellular Delivery by Membrane Disruption: Mechanisms, Strategies, and Concepts

Intracellular delivery is a key step in biological research and has enabled decades of biomedical discoveries. It is also becoming increasingly important in industrial and medical applications ranging from biomanufacture to cell-based therapies. Here, we review techniques for membrane disruption-based intracellular delivery from 1911 until the present. These methods achieve rapid, direct, and universal delivery of almost any cargo molecule or material that can be dispersed in solution. We start by covering the motivations for intracellular delivery and the challenges associated with the different cargo types-small molecules, proteins/peptides, nucleic acids, synthetic nanomaterials, and large cargo. The review then presents a broad comparison of delivery strategies followed by an analysis of membrane disruption mechanisms and the biology of the cell response. We cover mechanical, electrical, thermal, optical, and chemical strategies of membrane disruption with a particular emphasis on their applications and challenges to implementation. Throughout, we highlight specific mechanisms of membrane disruption and suggest areas in need of further experimentation. We hope the concepts discussed in our review inspire scientists and engineers with further ideas to improve intracellular delivery.

Edible Rabies Vaccines

Rabies has been one of the most feared diseases throughout history. Human rabies remains an important public health problem in many developing countries. The WHO reports that more than 55,000 people die of this disease every year. Most of these cases occur in developing countries. In most Latin American countries, the major reservoirs of rabies are the dog and the hematophagous bat (Desmodus rotundus), which is present in the tropical and subtropical areas from Northern Mexico to Northern Argentina and Chile and transmits the disease to cattle. One of the better options for controlling rabies is vaccination. The expression of rabies virus G protein in different plant systems for developing an oral rabies vaccine could reduce costs of production and distribution and would be convenient for developing countries where the disease is endemic.

A simple and efficient transient transformation for hybrid aspen (Populus tremula × P. tremuloides)

BACKGROUND

The genus Populus is accepted as a model system for molecular tree biology. To investigate gene functions in Populus spp. trees, generating stable transgenic lines is the common technique for functional genetic studies. However, a limited number of genes have been targeted due to the lengthy transgenic process. Transient transformation assays complementing stable transformation have significant advantages for rapid in vivo assessment of gene function. The aim of this study is to develop a simple and efficient transient transformation for hybrid aspen and to provide its potential applications for functional genomic approaches.

RESULTS

We developed an in planta transient transformation assay for young hybrid aspen cuttings using Agrobacterium-mediated vacuum infiltration. The transformation conditions such as the infiltration medium, the presence of a surfactant, the phase of bacterial growth and bacterial density were optimized to achieve a higher transformation efficiency in young aspen leaves. The Agrobacterium infiltration assay successfully transformed various cell types in leaf tissues. Intracellular localization of four aspen genes was confirmed in homologous Populus spp. using fusion constructs with the green fluorescent protein. Protein-protein interaction was detected in transiently co-transformed cells with bimolecular fluorescence complementation technique. In vivo promoter activity was monitored over a few days in aspen cuttings that were transformed with luciferase reporter gene driven by a circadian clock promoter.

CONCLUSIONS

The Agrobacterium infiltration assay developed here is a simple and enhanced throughput method that requires minimum handling and short transgenic process. This method will facilitate functional analyses of Populus genes in a homologous plant system.

Transformation and conjugal transfer of foreign genes into the filamentous multicellular cyanobacteria (subsection V) Fischerella and Chlorogloeopsis

Cyanobacteria of subsection V grow as filaments with asymmetrical cell divisions that can generate a true-branching phenotype. Members of the genera Fischerella and Chlorogloeopsis furthermore differentiate akinetes (spore-like resting stages), heterocysts (specialized in nitrogen fixation) and hormogonia (cell aggregates with gliding motility for colonization and dispersal). Genetic approaches to studying the complex morphology and differentiations of these prokaryotes require transformation techniques. For Fischerella and Chlorogloeopsis reliable protocols for introducing foreign genes are lacking. Here, we explored conjugation, electroporation, and biolistic DNA transfer methods in Fischerella and Chlorogloeopsis, using the cyanobacterial replicon pRL25C as a marker. We successfully transformed Fischerella muscicola PCC 7414 and Chlorogloeopsis fritschii PCC 6912 and were able to express the GFP reporter protein under two different promoters: the nitrogen regulated (p) glnA and the strong E. coli hybrid (p) trc. For Fischerella all methods worked, for Chlorogloeopsis electroporation was unsuccessful. For both strains conjugation delivered the most reproducible results, whereby partial removal of the exopolysaccharide sheath by salt washing was a critical step.

Biofortification of essential nutritional compounds and trace elements in rice and cassava

Plant biotechnology can make important contributions to food security and nutritional improvement. For example, the development of 'Golden Rice' by Professor Ingo Potrykus was a milestone in the application of gene technology to deliver both increased nutritional qualities and health improvement to wide sections of the human population. Mineral nutrient and protein deficiency as well as food security remain the most important challenges for developing countries. Current projects are addressing these issues in two major staple crops, cassava (Manihot esculenta Crantz) and rice. The tropical root crop cassava is a major source of food for approximately 600 million of the population worldwide. In sub-Saharan Africa >200 million of the population rely on cassava as their major source of dietary energy. The nutritional quality of the cassava root is not sufficient to meet all dietary needs. Rice is the staple food for half the world population, providing approximately 20% of the per capita energy and 13% of the protein for human consumption worldwide. In many developing countries the dietary contributions of rice are substantially greater (29.3% dietary energy and 29.1% dietary protein). The current six most popular 'mega' rice varieties (in terms of popularity and acreage), including Chinese hybrid rice, have an incomplete amino acid profile and contain limited amounts of essential micronutrients. Rice lines with improved Fe contents have been developed using genes that have functions in Fe absorption, translocation and accumulation in the plant, as well as improved Fe bioavailability in the human intestine. Current developments in biotechnology-assisted plant improvement are reviewed and the potential of the technology in addressing human nutrition and health are discussed.

Contribution of somatic mutations in the mitochondrial genome to the development of cancer and tolerance against anticancer drugs

Mitochondrial defects have long been suspected to play an important role in the development of cancer. Although most cancer cells harbor somatic mutations in mitochondrial DNA (mtDNA), the question of whether such mutations positively contribute to the development of cancer remained unclear. To clarify the role of mutant mtDNA excluding effects by the nuclear background, we focus on a method of transmitochondrial cybrids. Tumors were formed by transplanting cybrids with or without mutant mtDNA into nude mice and compared each size, revealing that mutant cybrids enhanced tumorigenesis. Next, we discuss a method for excluding the possibility of secondary nuclear mutations that may affect tumorigenesis. Mitochondrial genes that had been converted from mitochondrial to nuclear codons and equipped with a mitochondrial-targeting sequence were introduced into the nucleus of mutant cybrids. The gene products complemented the dysfunction, and reduced the promotion of tumors. By these methods, we concluded that mutant mitochondria positively and directly contribute to tumorigenesis. Since apoptosis occurred less frequently in the mutant versus wild-type cybrids in tumors, pathogenic mtDNA mutations contribute to the promotion of tumors by preventing apoptosis. Finally, we discuss the role of mutant mtDNA in conferring tolerance against anticancer drugs.

A model of organotypic rat spinal slice culture and biolistic transfection to elucidate factors that drive the preprotachykinin-A promoter

The tachykinin substance P (SP) is a neuropeptide that is expressed in some nociceptive primary sensory afferents and in discrete populations of spinal cord neurons. Expression of spinal SP and the preprotachykinin-A (PPT-A) gene that encodes SP exhibits plasticity in response to conditions such as peripheral inflammation but the mechanisms that regulate expression are poorly understood. We have developed a spinal cord organotypic culture system that is suitable for the analysis of PPT-A gene promoter activity following biolistic transfection of recombinant DNA constructs. Spinal cord organotypic slices showed good viability over a 7-day culture period. Immunostaining for phenotypic markers such as NeuN and beta-III tubulin demonstrated preservation of neurons and their structure, although there was evidence of axotomy-induced down-regulation of NeuN in certain neuronal populations. Neurokinin-1 receptor (NK-1R) immunostaining in laminae I and III was similar to that seen in acute slices. Biolistic transfection was used to introduce DNA constructs into neurons of these organotypic cultures. Following transfection with a construct in which expression of enhanced green fluorescent protein (EGFP) is controlled by the PPT-A promoter, we showed that induction of neuronal activity by administration of a forskolin analogue/high K(+) (10 microM/10 mM) for 24 h resulted in a fourfold increase in the number of EGFP-positive cells. Similarly, a twofold increase was obtained after treatment with the NK-1R-specific agonist [Sar(9),Met (O(2))(11)]-substance P (10 microM). These data demonstrate the usefulness of this model to study physiological and pharmacological factors relevant to nociceptive processing that can modulate PPT-A promoter activity.

Transposon-mediated enhancer trapping in medaka

We tested the Sleeping Beauty transposable element for its ability to efficiently insert transgenes into the genome of medaka (Oryzias latipes), an important model system for vertebrate development. We show that the SB transposon efficiently mediates integration of a reporter gene into the fish germ line. In pilot experiments, we established 174 transgenic lines with a transgenesis efficiency of 32%. Transgenes are stably transmitted to, and expressed in, subsequent generations. Interestingly, the transgenic lines show novel expression patterns with temporal and spatial specificity at a rate of 12% (21/174), likely due to both, enhancing and silencing position effects. Furthermore, promoter-dependent GFP expression in injected fish embryos is tightly correlated with germ line transmission, facilitating easy selection of founder fish. Thus, the SB transposon/transposase system provides a highly efficient tool for transgenesis in general and for the generation of novel reporter gene expression patterns in particular.

Delivery of genes and fluorescent dyes into cells of the intact lens by particle bombardment

The authors report the use of a particle bombardment technique to deliver exogenous genes and fluorescent dyes into living fibre cells in the intact lens. Gold particles were coated with plasmid DNA encoding green fluorescent protein (GFP) or the lipophilic fluorescent probes DiI and DiO. The particles were introduced into embryonic chicken or neonatal mouse lenses using a pressurized helium charge. A significant fraction of particles penetrated the capsule and came to rest in the superficial lens cortex. Over the range tested, varying the particle size or the pressure of the helium charge had little effect on the final distribution of particles within the lens. Particle bombardment was used initially to deliver DiI and DiO into the lens. Within a few hours, bombarded lenses exhibited multicolored membranous labelling of individual, elongating fibre cells. The particle bombardment technique was also used to introduce a plasmid encoding GFP. After overnight incubation, many fibre cells in the bow region expressed GFP. On close examination by confocal reflectance microscopy, each expressing cell was found to contain a gold particle lodged in its nucleus. The authors examined the fate of GFP-expressing fibre cells over a period of 1 week in organ culture. In the embryonic chicken lens, transfected fibres showed modest (approximately two-fold) elongation. In contrast, GFP-expressing mouse lens fibres underwent dramatic elongation, reaching the anterior and posterior sutures after 7 days in culture. These species differences may reflect the fact that mitosis continued at a near normal rate in the cultured mouse lens but declined precipitously in the cultured chicken lens. These results suggest that particle bombardment, in conjunction with appropriate cell culture conditions, may prove useful in visualizing the behaviour of differentiating fibre cells in the living intact lens in vitro.

A biolistic process for in vitro gene transfer into chicken embryos

Chicken embryos kept in culture medium were bombarded using a high helium gas pressure biolistic device. To optimize the factors that affect transformation efficiency, the lacZ gene under control of the human cytomegalovirus immediate early enhancer/promoter was used as a reporter gene. There was an inverse relationship between survival rate and transformation efficiency. The best conditions obtained for high embryo survival and high transformation efficiency were achieved with 800 psi helium gas pressure, 500 mmHg vacuum, gold particles, an 8 cm DNA-coated microparticle flying distance to the embryo and embryo placement 0.5 cm from the center of the particle dispersion cone. Under these conditions, transformation efficiency was 100%, survival rate 25% and the number of expression units in the embryo body cells ranged from 100 to 1,000. Expression of green fluorescent protein was also detected in embryos bombarded under optimal conditions. Based on the results obtained, the biolistic process can be considered an efficient method for the transformation of chicken embryos and therefore can be used as a model system to study transient gene expression and tissue-specific promoters.

Gene therapy: principles and applications to hematopoietic cells

Ever since the development of technology allowing the transfer of new genes into eukaryotic cells, the hematopoietic system has been an obvious and desirable target for gene therapy. The last 10 years have witnessed an explosion of interest in this approach to treat human disease, both inherited and acquired, with the initiation of multiple clinical protocols. All gene therapy strategies have two essential technical requirements. These are: (1) the efficient introduction of the relevant genetic material into the target cell and (2) the expression of the transgene at therapeutic levels. Conceptual and technical hurdles involved with these requirements are still the objects of active research. To date, the most widely used and best understood vectors for gene transfer in hematopoietic cells are derived from retroviruses, although they suffer from several limitations. However, as gene transfer mechanisms become more efficient and long-term gene expression is enhanced, the variety of diseases that can be tackled by gene therapy will continue to expand. However, until the problem of delivery and subsequent expression is adequately resolved, gene therapy will not realize its full potential. The first part of this review gives an overview of the gene delivery technology available at present to transfer genetic sequences in human somatic cells. The relevance of the hematopoietic system to the development of gene therapy strategies as well as hematopoietic cell-based gene therapy is discussed in the second part.

Construction of a stable and highly infectious intron-containing cDNA clone of plum pox potyvirus and its use to infect plants by particle bombardment

An infectious plum pox potyvirus cDNA clone was constructed placing a copy of the full-length sequence of the virus genome between an enhanced cauliflower mosaic virus 35S promoter and a nopaline synthase termination signal. Stabilization of the clone and faster growth of bacteria, in addition to higher plasmid yield, followed a modification consisting of the insertion of an intron which interrupted the viral open reading frame at the P3 region. This intron-containing clone was infectious when inoculated into plants after undergoing in vivo transcription and splicing. Particle bombardment delivery of the cDNA greatly increased the efficiency of plant infection.

In situ DNA transfer to chicken embryos by biolistics

Fertilized chicken eggs were bombarded with a biolistic device. Transient expression of the lacZ gene under the control of a human cytomegalovirus (CMV) promoter was assessed after in situ gene transfer using this approach. The influence of different pressures, vacuum levels and particles was tested. Survival rate improved as particle velocity decreased, but resulted in lower levels of expression. The best survival and expression were obtained with gold particles, a helium gas pressure of 600 psi and a vacuum of 600 mmHg. Under these conditions, all bombarded embryos showed <FONT FACE="Symbol">b</FONT>-galactosidase activity, indicating that this was an effective method for transformation of chicken embryos.

Production of recombinant subunit vaccines: protein immunogens, live delivery systems and nucleic acid vaccines

The first scientific attempts to control an infectious disease can be attributed to Edward Jenner, who, in 1796 inoculated an 8-year-old boy with cowpox (vaccinia), giving the boy protection against subsequent challenge with virulent smallpox. Thanks to the successful development of vaccines, many major diseases, such as diphtheria, poliomyelitis and measles, are nowadays kept under control, and in the case of smallpox, the dream of eradication has been fulfilled. Yet, there is a growing need for improvements of existing vaccines in terms of increased efficacy and improved safety, besides the development of completely new vaccines. Better technological possibilities, combined with increased knowledge in related fields, such as immunology and molecular biology, allow for new vaccination strategies. Besides the classical whole-cell vaccines, consisting of killed or attenuated pathogens, new vaccines based on the subunit principle, have been developed, e.g. the Hepatitis B surface protein vaccine and the Haemophilus influenzae type b vaccine. Recombinant techniques are now dominating in the strive for an ideal vaccine, being safe and cheap, heat-stable and easy to administer, preferably single-dose, and capable of inducing broad immune response with life-long memory both in adults and in infants. This review will describe different recombinant approaches used in the development of novel subunit vaccines, including design and production of protein immunogens, the development of live delivery systems and the state-of-the-art for nucleic acids vaccines.

Transient expression of DNA and RNA in parasitic helminths by using particle bombardment

Parasitic helminths (worms belonging to several metazoan phyla) cause considerable morbidity and mortality in humans. They are an important veterinary problem, and they result in significant economic losses in animal grazing and agriculture. Experimental studies on parasitic helminths have been limited by a lack of parasite cell lines and methods for molecular genetic analyses. We evaluated particle bombardment (biolistics) as a strategy to introduce and express nucleic acids in these multicellular parasites. By using embryos of the parasitic nematode Ascaris as a model, we developed methods to introduce and express both DNA and RNA during several stages of Ascaris embryogenesis. Biolistic transfection will facilitate experimental strategies in Ascaris embryos complementing other biochemical tools available (e.g., in vitro whole-cell embryo extracts for transcription, RNA processing, and translation). Transfection experiments with adult schistosomes further suggest that the biolistic strategy should be applicable to a variety of other parasitic helminths. The development of these methods provides molecular genetic tools to study gene expression and the biology of a variety of types and developmental stages of important helminth parasites.

The challenge of vector development in gene therapy

Gene therapy is the treatment of diseases based on the transfer of genetic information. Agents that carry or deliver DNA to target cells are called vectors (Latin vector: carrier, deliverer). Ideally, a vector should accommodate an unlimited amount of inserted DNA, lack the ability of autonomous replication of its own DNA, be easily manufactured, and be available in concentrated form. Secondly, it should have the ability to target specific cell types or to limit its gene expression to specific cell types, and to achieve sustained gene expression in the long term or in a controlled fashion. Finally, it should not be toxic or immunogenic. Such a vector does not exist and none of the DNA delivery systems so far available for in vivo gene transfer is perfect with respect to any of these points. Gene therapy and the means to promote it depend heavily on the development and improvement of new gene vector systems.

Use of EBV-based Vector/HVJ-liposome complex vector for targeted gene therapy of EBV-associated neoplasms

Targeted suicide gene therapy for Epstein-Barr virus (EBV)-associated neoplasms was attempted by using EBV-based plasmid vectors coupled with hemagglutinating virus of Japan (HVJ)-liposome in vitro. Expression of EBV nuclear antigen (EBNA)1 is a common feature of the neoplasms associated with EBV. When various leukemic cell lines were transduced with a vector carrying a marker gene and EBV replication origin of plasmid (oriP), the marker gene product was exclusively detected in cells expressing EBNA1. Transduction of herpes simplex virus (HSV)-1 thymidine kinase (Tk) gene resulted in a marked reduction in viable cell number by ganciclovir (GCV) specifically in EBNA1 positive cells. The results demonstrate that this virus-free system may be applicable to gene therapy of EBV-associated neoplasms.

Gene transfer by biolistic process

Gene transfer into somatic tissues is a tool for both the study of gene function in the basic science laboratory and for gene therapy and genetic immunization in the clinic. Biolistic processes can be used to deliver both viral and nonviral vectors into somatic tissues. This review discusses the advantages and disadvantages of three biolistic processes: jet injection, microparticle bombardment, and needle and syringe injection. Jet injection and needle and syringe injection can be used to deliver both viral and nonviral vectors. Both jet injection and microparticle bombardment can be used to target a broad range of tissues. Needle and syringe injection has been most widely used in muscle tissue. The choice of which biolistic process to use is dependent on the specific application.