High-efficiency gene transfer into cells

Enhancement of biomolecule transport by electroporation: A review of theory and practical application to transformation ofCorynebacterium glutamicum

Selective and reversible permeabilization of the cell wall permeability barrier is the focus for many biotechnological applications. In this article, the basic principles for reversible membrane permeabilization, based on biological, chemical, and physical methods are reviewed. Emphasis is given to electroporation (electropermeabilization) which tends to be the most popular method for membrane permeabilization and for introduction of foreign molecules into the cells. The applications of this method in industrial processes as well as the critical factors and parameters which affect the success of this approach are discussed. The different strategies developed throughout the years for increased transformation efficiencies of the industrially important amino acid-overproducing bacterium Corynebacterium glutamicum, are also summarized.

Zwitterionic Latex Particles as an Effective Carrier for DNA

The ability of small particles to associate with DNA and to transport it to desired targets without being subjected to interferences can make them efficient vehicles for gene delivery. Keeping these requirements in mind, zwitterionic latex particles with two different functional tethers were chosen for studying their interaction with DNA as vehicle complexes. From adsorption and electrokinetic studies, it is evident that zwitterionic latex particles can have marked association with DNA. Moreover, DNA-latex complexation does not provoke undesired aggregation of latex particles. These characteristics are important for it to carry the DNA efficiently under changing media conditions.

Gene transfer by cationic surfactants is essentially limited by the trapping of the surfactant/DNA complexes onto the cell membrane: a fluorescence investigation

The interaction between complexes of plasmid DNA with cetyltrimethylammonium bromide (CTAB) and L929 fibroblasts was first examined using confocal microscopy. The complexes labeled with the DNA intercalator, YOYO-1, were found to be trapped onto the external face of the plasma membrane; a feature that may constitute a major limiting step in transfection. Moreover, since no cytotoxic effect appeared in these conditions, we further inferred that the CTAB molecules remained bound to the DNA. The interaction of the complexes with the membranes was best modeled with neutral vesicles. From anisotropy thermotropic curves of DPHpPC-labeled vesicles and fluorescence resonance energy transfer measurements between these vesicles and YOYO-labeled complexes, we evidenced that the binding of the complexes to the vesicle surface opened the micelle-like domains and unwound DNA. However, DNA was not released but remained stably bound via electrostatic interactions to the CTAB molecules incorporated in the external liposome leaflet. Consequently, the large diameter of the unwound plasmid DNA is likely the major factor that precludes its internalization into the cells by endocytosis. In contrast, anionic vesicles that mimic the cytoplasmic facing monolayer of the plasma membrane rapidly released DNA from the complex. This may explain the previously reported high transfection efficiency of DNA complexed with liposomes composed of neutral lipids and cationic surfactants, since the latter may destabilize the endosomal membrane and induce the release of DNA in the cytoplasm.

Breaking the barrier: methods for reversible permeabilization of cellular membranes

Plasma membrane constitutes a major barrier for the entry of hydrophilic molecules into the cell interior. Selective and reversible permeabilization of this barrier is a prerequisite for many biotechnological applications. This article reviews general principles of membrane permeabilization based on biological, chemical, and physical methods and mechanisms of the delivery of extrinsic substances to cell interior. The emphasis is given on the methods that have significantly contributed to our understanding of biological phenomena on membrane level or have been widely used in current biotechnology, such as delivery by membrane vehicles, electropermeabilization, microinjection, and biolistics. The mechanisms of the internalization of extrinsic substances and the advantages and drawbacks of individual techniques are discussed with respect to specific applications in biotechnology.

Gene therapy. Molecular medicine of the 1990s

In less than four years, the techniques of gene transfer have been taken from the laboratory and translated into numerous clinical trials. Although gene therapy was initially designed for the molecular repair of monogenic deficiency diseases, most of the current studies of gene therapy are targeting cancer.

Fusion-mediated transfer of plasmids into Spiroplasma floricola cells

We have developed and characterized a system for the transfer of plasmids encapsulated in large unilamellar vesicles (LUV) into Spiroplasma floricola BNR1 cells. The approach is based on the ability of S. floricola-derived LUV to fuse with S. floricola cells. The fusion was continuously monitored by an assay for lipid mixing based on the dequenching of the fluorescent probe octadecylrhodamine B (R18) that was incorporated into LUV at self-quenching concentrations. The fusion was also evaluated by fluorescence-activated cell sorter measurements and by sucrose density gradient analysis. LUV-cell fusion occurred only in the presence of low concentrations (5%) of polyethylene glycol (polyethylene glycol 8000) and depended on temperature, the LUV/cell ratio, and divalent cations in the incubation medium. Throughout the fusion process, spiroplasma cells remained intact and viable. Under optimal fusion conditions, the plasmid pACYC, encapsulated in LUV by reversed-phase evaporation, was transferred into live S. floricola cells and expressed chloramphenicol acetyltransferase activity. The expression was transient with maximal chloramphenicol acetyltransferase activity observed after 6 h of incubation of the transfected cells.

Liposomes for the transformation of eukaryotic cells

Gene therapy of human disease is a method of treatment under active development. DNA-loaded liposomes exhibit great promise for use in this field. Liposome-based transfection vectors have many inherent advantages that will likely lead to their wide in vivo use. Vectors with low toxicity and a high degree of targetability can now be easily prepared. These vectors are also free of the length constraints governing retroviral vectors. In this review we discuss recent developments in the use of liposomes for transfection of eukaryotic cells.