151
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Guo W, Lee RJ. Efficient gene delivery via non-covalent complexes of folic acid and polyethylenimine. J Control Release 2001; 77:131-8. [PMID: 11689266 DOI: 10.1016/s0168-3659(01)00456-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Polyethylenimine (PEI) is a cationic polymer capable of delivering DNA molecules into cultured mammalian cells as charge complexes. The application of PEI polyplexes in gene therapy, however, is hampered by the sensitivity of its transfection activity to the presence of serum. We found that folic acid, in a variety of cell lines, significantly enhanced PEI-mediated transfection activity in the presence of serum, whether the folic acid was added during or after PEI/DNA polyplex formation. The increase in activity could not be produced with other anionic compounds such as cholic acid, citric acid, EDTA, or glutamic acid. This novel formulation provides a reliable, low-cost, and highly efficient method for delivery of genes and may have applications in gene therapy.
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Affiliation(s)
- W Guo
- Division of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, Room 542, LM Parks Hall, The Ohio State University, 500 West 12th Ave., Columbus, OH 43210, USA
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152
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Gosselin MA, Guo W, Lee RJ. Efficient gene transfer using reversibly cross-linked low molecular weight polyethylenimine. Bioconjug Chem 2001; 12:989-94. [PMID: 11716690 DOI: 10.1021/bc0100455] [Citation(s) in RCA: 352] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polyethylenimine (PEI) is a polycation with potential application as a nonviral vector for gene delivery. Here we show that after conjugation with homobifunctional amine reactive reducible cross-linking reagents, low molecular weight polyethylenimine efficiently mediates in vitro gene delivery to Chinese hamster ovary (CHO) cells. Two cross-linking reagents, dithiobis(succinimidylpropionate) (DSP) and dimethyl.3,3'-dithiobispropionimidate*2HCl (DTBP), were utilized based on their reactivity and chemical properties. Both reagents react with primary amines to form reducible cross-links; however, unlike DSP, the DTBP cross-linker maintains net polymer charge through amidine bond formation. PEI with a reported weight-average molecular weight (M(w)) of 800 Da was reacted with either DSP or DTBP at PEI primary amine:cross-link reactive group ratios of 1:1 and 2:1. The transfection efficiencies of the resulting cross-linked products were evaluated in CHO cells using a luciferase reporter gene under a cytomegalovirus (CMV) promoter. Our results show that cross-linked polymers mediate variable levels of transfection depending on the cross-linking reagent, the extent of conjugation, and the N/P ratio. In general, we found conjugate size to be proportional to gene transfer efficiency. Using gel retardation analysis, we also evaluate the capacity of the cross-linked polymers to condense plasmid DNA before and after reduction with 45 mM dithiothreitol (DTT). DTT mediated reduction of intra-cross-link disulfide bonds and inhibited condensation of DNA by conjugates cross-linked with DSP at a ratio of 1:1, but had little effect on the remaining polymers. Analogous intracellular reduction of transfection complexes by reduced glutathione could facilitate uncoupling of PEI from DNA to enhance gene expression.
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Affiliation(s)
- M A Gosselin
- College of Pharmacy, Division of Pharmaceutics and Pharmaceutical Chemistry, The Ohio State University, Columbus, Ohio 43210, USA
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153
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Abstract
Many cells express surface membrane lectins that selectively bind and carry glycoconjugates into intracellular endosomes; in addition, various intracellular membrane and soluble lectins act as shuttles between different compartments. On this basis, we developed glycosylated polycations, now called glycofectins (glycosylated polylysine and polyethyleneimine). Recently, we set up a simple way to transform oligosaccharides into glycosynthons suitable to substitute proteins or polymers. Glycofectins bind plasmid DNA leading to compact glycoplexes. Glycoplexes prepared with glycofectins were found to be much more active than naked plasmid to transfer genes to various types of cells including human airway epithelial and serous cells. The gene transfer efficiency was found to depend on the nature of the sugars borne by glycofectins. It appeared that the sugar-dependent efficiency was not only related to the uptake but also to the intracellular traffic of glycoplexes.
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Affiliation(s)
- I Fajac
- Laboratoire de Physiologie Respiratoire, CHU Cochin, AP-HP-Université Paris V, Paris, France
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154
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Köping-Höggård M, Tubulekas I, Guan H, Edwards K, Nilsson M, Vårum KM, Artursson P. Chitosan as a nonviral gene delivery system. Structure-property relationships and characteristics compared with polyethylenimine in vitro and after lung administration in vivo. Gene Ther 2001; 8:1108-21. [PMID: 11526458 DOI: 10.1038/sj.gt.3301492] [Citation(s) in RCA: 435] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2000] [Accepted: 04/19/2001] [Indexed: 12/16/2022]
Abstract
Chitosan is a natural cationic linear polymer that has recently emerged as an alternative nonviral gene delivery system. We have established the relationships between the structure and the properties of chitosan-pDNA polyplexes in vitro. Further, we have compared polyplexes of ultrapure chitosan (UPC) of preferred molecular structure with those of optimised polyethylenimine (PEI) polyplexes in vitro and after intratracheal administration to mice in vivo. Chitosans in which over two out of three monomer units carried a primary amino group formed stable colloidal polyplexes with pDNA. Optimized UPC and PEI polyplexes protected the pDNA from serum degradation to approximately the same degree, and they gave a comparable maximal transgene expression in 293 cells. In contrast to PEI, UPC was non toxic at escalating doses. After intratracheal administration, both polyplexes distributed to the mid-airways, where transgene expression was observed in virtually every epithelial cell, using a sensitive pLacZ reporter containing a translational enhancer element. However, the kinetics of gene expression differed - PEI polyplexes induced a more rapid onset of gene expression than UPC. This was attributed to a more rapid endosomal escape of the PEI polyplexes. Although this resulted in a more efficient gene expression with PEI polyplexes, UPC had an efficiency comparable to that of commonly used cationic lipids. In conclusion, this study provides insights into the use of chitosan as a gene delivery system. It emphasises that chitosan is a nontoxic alternative to other cationic polymers and it forms a platform for further studies of chitosan-based gene delivery systems.
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Affiliation(s)
- M Köping-Höggård
- Department of Pharmacy, Division of Pharmaceutics, Uppsala University, Uppsala, Sweden
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155
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Blessing T, Kursa M, Holzhauser R, Kircheis R, Wagner E. Different strategies for formation of pegylated EGF-conjugated PEI/DNA complexes for targeted gene delivery. Bioconjug Chem 2001; 12:529-37. [PMID: 11459457 DOI: 10.1021/bc0001488] [Citation(s) in RCA: 197] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
With the aim of generating gene delivery systems for tumor targeting, we have synthesized a conjugate consisting of polyethylenimine (PEI) covalently modified with epidermal growth factor (EGF) peptides. Transfection efficiency of the conjugate was evaluated and compared to native PEI in three tumor cell lines: KB epidermoid carcinoma cells, CMT-93 rectum carcinoma cells, and Renca-EGFR renal carcinoma cells. Depending on the tumor cell line, incorporation of EGF resulted in an up to 300-fold increased transfection efficiency. This ligand-mediated enhancement and competition with free EGF strongly suggested uptake of the complexes through the EGF receptor-mediated endocytosis pathway. Shielded particles being crucial for systemic gene delivery, we studied the effect of covalent surface modification of EGF-PEI/DNA complexes with a poly(ethylene glycol) (PEG) derivative. An alternative way for the formation of PEGylated EGF-containing complexes was also evaluated where EGF was projected away from PEI/DNA core complexes through a PEG linker. Both strategies led to shielded particles still able to efficiently transfect tumor cells in a receptor-dependent fashion. These PEGylated EGF-containing complexes were 10- to 100-fold more efficient than PEGylated complexes without EGF.
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Affiliation(s)
- T Blessing
- Institute of Medical Biochemistry, University of Vienna, Dr. Bohrgasse 9/3, A-1030 Vienna and Boehringer Ingelheim Austria, Dr. Boehringer Gasse 5-11, A-1121 Vienna, Austria.
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156
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Abstract
Development of an efficient method for introducing a therapeutic gene into target cells in vivo is the key issue in treating genetic and acquired diseases by gene therapy. To this end, various nonviral vectors have been designed and developed, and some of them are in clinical trials. The simplest approach is naked DNA injection into local tissues or systemic circulation. Physical (gene gun, electroporation) and chemical (cationic lipid or polymer) approaches have also been utilized to improve the efficiency and target cell specificity of gene transfer by plasmid DNA. After administration, however, nonviral vectors encounter many hurdles that result in diminished gene transfer in target cells. Cationic vectors sometimes attract serum proteins and blood cells when entering into blood circulation, which results in dynamic changes in their physicochemical properties. To reach target cells, nonviral vectors should pass through the capillaries, avoid recognition by mononuclear phagocytes, emerge from the blood vessels to the interstitium, and bind to the surface of the target cells. They then need to be internalized, escape from endosomes, and then find a way to the nucleus, avoiding cytoplasmic degradation. Successful clinical applications of nonviral vectors will rely on a better understanding of barriers in gene transfer and development of vectors that can overcome these barriers.
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Affiliation(s)
- M Nishikawa
- Center for Pharmacogenetics, University of Pittsburgh School of Pharmacy, Pittsburgh, PA 15213, USA
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157
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Abstract
The delivery of genetic material into cells is a field that is expanding very rapidly. Non-viral delivery methods, especially ones that focus on the use of chemical agents complexed with genetic material, are the focus of this mini-review. More-recent uses of known transfection agents such as poly(ethylenimine), poly(L-lysine), and various liposomes are discussed, and some novel approaches (both chemical and methodical) are reviewed as well. A very brief look at how non-viral gene delivery research is being aimed at the clinic is also included.
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Affiliation(s)
- W T Godbey
- Department of Bioengineering, Rice University, P.O. Box 1892, MS 142, Houston, TX 77251-1892, USA
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158
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Abstract
This review focuses on the use of synthetic (non-viral) delivery systems for cancer gene therapy. Therapeutic strategies such as gene replacement/mutation correction, immune modulation and molecular therapy/'suicide' gene therapy type approaches potentially offer unique and novel ways of fighting cancer, some of which have already shown promise in early clinical trials. However, the specific and efficient delivery of the genetic material to remote tumors/metastases remains a challenge, which is being addressed using a variety of viral and non-viral systems. Each of these disparate systems has distinct advantages and disadvantages, which need to be taken into account when a specific therapeutic gene is being used. The review concentrates on particulate gene delivery systems, which are formed through non-covalent complexation of cationic carrier molecules (e.g. lipids or polymers) and the negatively charged plasmid DNA. Such systems tend to be comparatively less efficient than viral systems, but have the inherent advantage of flexibility and safety. The DNA-carrier complex acts as a protective package, and needs to be inert and stable while in circulation. Once the remote site has been reached the complex needs to efficiently transfect the targeted (tumor) cells. In order to improve overall transfection specificity and efficiency it is necessary to optimize intracellular trafficking of the DNA complex as well as the performance after systemic administration. Common principles and specific advantages or disadvantages of the individual synthetic gene delivery systems are discussed, and their interaction with tumor-specific and generic biological barriers are examined in order to identify potential strategies to overcome them.
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Affiliation(s)
- A G Schatzlein
- CRC Department of Medical Oncology, Beatson Laboratories, University of Glasgow, Switchback Road, Glasgow G61 1BD, UK.
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159
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Diebold SS, Cotten M, Koch N, Zenke M. MHC class II presentation of endogenously expressed antigens by transfected dendritic cells. Gene Ther 2001; 8:487-93. [PMID: 11313828 DOI: 10.1038/sj.gt.3301433] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2000] [Accepted: 01/15/2001] [Indexed: 11/08/2022]
Abstract
Dendritic cells (DC) present immunogenic epitopes of antigens in the context of MHC class I and class II molecules in association with costimulatory molecules, and efficiently activate both cytotoxic T cells and T helper cells. Gene modified DC expressing antigen encoding cDNA represent a particularly attractive approach for the immunotherapy of disease. We previously described a gene delivery system for DC based on receptor-mediated endocytosis of ligand/polyethylenimine (PEI) DNA transfer complexes that target cell surface receptors which are abundantly expressed on DC. Employing this gene delivery system, DC were generated that express chicken ovalbumin (OVA) cDNA as a model antigen and introduce antigen into the MHC class I presentation pathway. We demonstrate here that modification of OVA cDNA as transferrin receptor (TfR) or invariant chain (Ii) fusions effectively generate MHC class II specific immune responses in addition to MHC class I responses. TfR-OVA contains the membrane anchoring region of transferrin receptor and represents a membrane-bound form of OVA for access to the MHC class II compartment. Ii-OVA fusions directly target the MHC class II processing pathway. Thus, modification of antigen encoding cDNA represents a convenient and effective means to direct antigens to MHC class II presentation and thus to generate T cell help.
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Affiliation(s)
- S S Diebold
- Max-Delbrück-Center for Molecular Medicine, MDC, Berlin, Germany
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160
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Horbinski C, Stachowiak MK, Higgins D, Finnegan SG. Polyethyleneimine-mediated transfection of cultured postmitotic neurons from rat sympathetic ganglia and adult human retina. BMC Neurosci 2001; 2:2. [PMID: 11231879 PMCID: PMC29102 DOI: 10.1186/1471-2202-2-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2000] [Accepted: 02/16/2001] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Chemical methods of transfection that have proven successful with cell lines often do not work with primary cultures of neurons. Recent data, however, suggest that linear polymers of the cation polyethyleneimine (PEI) can facilitate the uptake of nucleic acids by neurons. Consequently, we examined the ability of a commercial PEI preparation to allow the introduction of foreign genes into postmitotic mammalian neurons. Sympathetic neurons were obtained from perinatal rat pups and maintained for 5 days in vitro in the absence of nonneuronal cells. Cultures were then transfected with varying amounts of a plasmid encoding either E. coli beta-galactosidase or enhanced green fluorescence protein (EGFP) using PEI. RESULTS Optimal transfection efficiency was observed with 1 microg/ml of plasmid DNA and 5 microg/ml PEI. Expression of beta-galactosidase was both rapid and stable, beginning within 6 hours and lasting for at least 21 days. A maximum yield was obtained within 72 hours with approximately 9% of the neurons expressing beta-galactosidase, as assessed by both histochemistry and antibody staining. Cotransfection of two plasmids encoding reporter genes was achieved. Postmitotic neurons from adult human retinal cultures also demonstrated an ability to take up and express foreign DNA using PEI as a vector. CONCLUSIONS These data suggest that PEI is a useful agent for the stable expression of plasmid-encoded genes in neuronal cultures.
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Affiliation(s)
- Craig Horbinski
- Dept. of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, New York, USA
| | - Michal K Stachowiak
- Molecular and Structural Neurobiology and Gene Therapy Program, Department of Anatomy and Cell Biology, State University of New York at Buffalo, Buffalo, New York USA
| | - Dennis Higgins
- Dept. of Pharmacology and Toxicology, State University of New York at Buffalo, Buffalo, New York, USA
| | - Sarah G Finnegan
- Dept. of Neurology, State University of New York at Buffalo, Buffalo, New York, USA
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161
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Yamazaki N, Kojima S, Bovin NV, André S, Gabius S, Gabius HJ. Endogenous lectins as targets for drug delivery. Adv Drug Deliv Rev 2000; 43:225-44. [PMID: 10967228 DOI: 10.1016/s0169-409x(00)00071-5] [Citation(s) in RCA: 163] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To minimize side effects of drugs it would be ideal to target them exclusively to those cell types which require treatment. As a means to this end prototypical cellular recognition systems pique our interest to devise biomimetic strategies. Since oligosaccharides of glycoconjugates outmatch other information-carrying biomolecules (proteins, nucleic acids) in theoretical storage capacity by far, work on the sugar code can spark off development of effective targeting devices. Conjugation of custom-made glycan epitopes to proteins or biocompatible non-immunogenic polymeric scaffolds produces neoglycoconjugates with purpose-adaptable properties. In the interplay with endogenous receptors such as lectins, suitable oligosaccharides such as histo-blood group trisaccharides as parts of neoglycoconjugates have already proven their practical applications in histopathology. Elucidation of the structure of cell lectins with currently five main families aids to tailor ligand characteristics rationally. They include the types of functional groups and their topological presentation to optimize the bimolecular binding as well as the optimal spatial clustering and spacer characteristics to exploit cooperativity. Indeed, the potent trivalent cluster glycosides designed for the C-type asialoglycoprotein receptors furnish an instructive example how to turn the theoretical guideline on ligand modification into nM-affinity. By placing emphasis on tissue lectins as targets of neoglycoconjugate-mediated drug delivery, the long-term perspective is opened to likewise test members of these families themselves for routing of therapeutic payloads, aiming at cell addressins. This review illustrates the conceivable potential which work on the sugar code with custom-made neoglycoconjugates and tissue lectins can have in store for drug delivery.
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Affiliation(s)
- N Yamazaki
- Materials Design Laboratory, Department of Organic Materials, National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba-City, 305, Ibaraki, Japan.
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162
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Abstract
Dendritic cells (DCs) are potent antigen-presenting cells capable of priming activation of naive T cells. Because of their immunostimulatory capacity, immunization with DCs presenting tumor antigens has been proposed as a treatment regimen for cancer. The results from translational research studies and early clinical trials point to the need for improvement of DC-based tumor vaccines before they become a more broadly applicable treatment modality. In this regard, studies suggest that genetic modification of DCs to express tumor antigens and/or immunomodulatory proteins may improve their capacity to promote an antitumor response. Because the DC phenotype is relatively unstable, nonperturbing methods of gene transfer must be employed that do not compromise viability or immunostimulatory capacity. DCs expressing transgenes encoding tumor antigens have been shown to be more potent primers of antitumor immunity both in vitro and in animal models of disease; in some measures of immune priming, gene-modified DCs exceeded their soluble antigen-pulsed counterparts. Cytokine gene modification of DCs has improved their capacity to prime tumor antigen-specific T cell responses and promote antitumor immunity in vivo. Here, we review the current status of gene-modified DCs in both human and murine studies. Although successful results have been obtained to date in experimental systems, we discuss potential problems that have already arisen and may yet be encountered before gene-modified DCs are more widely applicable for use in human clinical trials.
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Affiliation(s)
- C J Kirk
- Department of Surgery, Tumor Immunology Program of the Comprehensive Cancer Center, University of Michigan Medical Center, Ann Arbor 48109-0666, USA.
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163
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Abstract
The ability to safely and efficiently transfer foreign DNA into cells is a fundamental goal in biotechnology. Toward this end, rapid advances have recently been made in our understanding of mechanisms for DNA stability and transport within cells. Current synthetic DNA delivery systems are versatile and safe, but substantially less efficient than viruses. Indeed, most current systems address only one of the obstacles to DNA delivery by enhancing DNA uptake. In fact, the effectiveness of gene expression is also dependent on several additional factors, including the release of intracellular DNA, stability of DNA in the cytoplasm, unpackaging of the DNA-vector complex, and the targeting of DNA to the nucleus. Delivery systems of the future must fully accommodate all these processes to effectively shepherd DNA across the plasma membrane, through the hostile intracellular environment, and into the nucleus.
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Affiliation(s)
- D Luo
- School of Chemical Engineering, Cornell University, Ithaca, NY 14850, USA
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