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Zhang H, Vandesompele J, Braeckmans K, De Smedt SC, Remaut K. Nucleic acid degradation as barrier to gene delivery: a guide to understand and overcome nuclease activity. Chem Soc Rev 2024; 53:317-360. [PMID: 38073448 DOI: 10.1039/d3cs00194f] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Gene therapy is on its way to revolutionize the treatment of both inherited and acquired diseases, by transferring nucleic acids to correct a disease-causing gene in the target cells of patients. In the fight against infectious diseases, mRNA-based therapeutics have proven to be a viable strategy in the recent Covid-19 pandemic. Although a growing number of gene therapies have been approved, the success rate is limited when compared to the large number of preclinical and clinical trials that have been/are being performed. In this review, we highlight some of the hurdles which gene therapies encounter after administration into the human body, with a focus on nucleic acid degradation by nucleases that are extremely abundant in mammalian organs, biological fluids as well as in subcellular compartments. We overview the available strategies to reduce the biodegradation of gene therapeutics after administration, including chemical modifications of the nucleic acids, encapsulation into vectors and co-administration with nuclease inhibitors and discuss which strategies are applied for clinically approved nucleic acid therapeutics. In the final part, we discuss the currently available methods and techniques to qualify and quantify the integrity of nucleic acids, with their own strengths and limitations.
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Affiliation(s)
- Heyang Zhang
- Laboratory for General Biochemistry and Physical Pharmacy, Department of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium.
- Leiden Academic Centre for Drug Research, Leiden University, 2333 CC Leiden, The Netherlands
| | - Jo Vandesompele
- Department of Biomolecular Medicine, Ghent University, 9000 Ghent, Belgium
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
| | - Kevin Braeckmans
- Laboratory for General Biochemistry and Physical Pharmacy, Department of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium.
- Centre for Nano- and Biophotonics, Ghent University, 9000 Ghent, Belgium
| | - Stefaan C De Smedt
- Laboratory for General Biochemistry and Physical Pharmacy, Department of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium.
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
- Centre for Nano- and Biophotonics, Ghent University, 9000 Ghent, Belgium
| | - Katrien Remaut
- Laboratory for General Biochemistry and Physical Pharmacy, Department of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium.
- Cancer Research Institute Ghent (CRIG), Ghent, Belgium
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2
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Lin Y, Wagner E, Lächelt U. Non-viral delivery of the CRISPR/Cas system: DNA versus RNA versus RNP. Biomater Sci 2022; 10:1166-1192. [DOI: 10.1039/d1bm01658j] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Since its discovery, the CRISPR/Cas technology has rapidly become an essential tool in modern biomedical research. The opportunities to specifically modify and correct genomic DNA has also raised big hope...
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3
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Nilsson JR, Baladi T, Gallud A, Baždarević D, Lemurell M, Esbjörner EK, Wilhelmsson LM, Dahlén A. Fluorescent base analogues in gapmers enable stealth labeling of antisense oligonucleotide therapeutics. Sci Rep 2021; 11:11365. [PMID: 34059711 PMCID: PMC8166847 DOI: 10.1038/s41598-021-90629-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 05/13/2021] [Indexed: 01/28/2023] Open
Abstract
To expand the antisense oligonucleotide (ASO) fluorescence labeling toolbox beyond covalent conjugation of external dyes (e.g. ATTO-, Alexa Fluor-, or cyanine dyes), we herein explore fluorescent base analogues (FBAs) as a novel approach to endow fluorescent properties to ASOs. Both cytosine and adenine analogues (tC, tCO, 2CNqA, and pA) were incorporated into a 16mer ASO sequence with a 3-10-3 cEt-DNA-cEt (cEt = constrained ethyl) gapmer design. In addition to a comprehensive photophysical characterization, we assess the label-induced effects on the gapmers' RNA affinities, RNA-hybridized secondary structures, and knockdown efficiencies. Importantly, we find practically no perturbing effects for gapmers with single FBA incorporations in the biologically critical gap region and, except for pA, the FBAs do not affect the knockdown efficiencies. Incorporating two cytosine FBAs in the gap is equally well tolerated, while two adenine analogues give rise to slightly reduced knockdown efficiencies and what could be perturbed secondary structures. We furthermore show that the FBAs can be used to visualize gapmers inside live cells using fluorescence microscopy and flow cytometry, enabling comparative assessment of their uptake. This altogether shows that FBAs are functional ASO probes that provide a minimally perturbing in-sequence labeling option for this highly relevant drug modality.
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Affiliation(s)
- Jesper R Nilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Tom Baladi
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden.,Medicinal Chemistry, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden.,Oligonucleotide Discovery, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Audrey Gallud
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden.,Advanced Drug Delivery, Pharmaceutical Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Dženita Baždarević
- Bioscience, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Malin Lemurell
- Medicinal Chemistry, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Elin K Esbjörner
- Department of Biology and Biological Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden
| | - L Marcus Wilhelmsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Anders Dahlén
- Oligonucleotide Discovery, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden.
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4
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Pretto C, Tang M, Chen M, Xu H, Subrizi A, Urtti A, van Hest JCM. Cowpea Chlorotic Mottle Virus-Like Particles as Potential Platform for Antisense Oligonucleotide Delivery in Posterior Segment Ocular Diseases. Macromol Biosci 2021; 21:e2100095. [PMID: 34031995 DOI: 10.1002/mabi.202100095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 05/06/2021] [Indexed: 01/08/2023]
Abstract
Due to its small size, easy accessibility and immune privileged environment, the eye represents an ideal target for therapeutic nucleic acids in the treatment of posterior segment ocular diseases, such as age-related macular degeneration (AMD). Among nanocarriers that can be used to achieve nucleic acid delivery, virus-like particles (VLPs) obtained from the Cowpea chlorotic mottle virus (CCMV) are an appealing platform, because of their loading capacity, ease of manufacture and amenability for functionalization. Herein, antisense oligonucleotide-loaded CCMV nanoparticles, intended for intravitreal injection, are evaluated for selective silencing of miR-23, an important target in AMD. CCMV nanoparticles loaded with anti-miR-23 locked nucleic acid and stabilized using the 3,3'-dithiobis(sulfosuccinimidyl propionate) (DTSSP) cross-linker, are assembled in vitro with a loading efficiency up to 80%. VLPs are found to be stable at 37 °C in the vitreous humor up to 24 hours. Nanoparticle cytotoxicity, cellular uptake and transfection efficacy are evaluated in endothelial cells. Selective miRNA down-regulation is achieved by the loaded CCMV VLPs both in absence and presence of Lipofectamine, with efficacies of ≈40% and more than 80%, respectively. The authors' findings pave the way for the future development of CCMV nanoparticles as oligonucleotide delivery platform to treat posterior segment ocular diseases.
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Affiliation(s)
- Chiara Pretto
- Department of Biomedical Engineering, Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, Eindhoven, 5600 MB, The Netherlands
| | - Miao Tang
- The Welcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Mei Chen
- The Welcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Heping Xu
- The Welcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Astrid Subrizi
- School of Pharmacy, University of Eastern Finland, Kuopio, 70210, Finland
| | - Arto Urtti
- School of Pharmacy, University of Eastern Finland, Kuopio, 70210, Finland
| | - Jan C M van Hest
- Department of Biomedical Engineering, Institute for Complex Molecular Systems, Eindhoven University of Technology, PO Box 513, Eindhoven, 5600 MB, The Netherlands
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5
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Hirata R, Hirakawa K, Shimada N, Watanabe K, Ohtsuki T. Fluorescence lifetime probes for detection of RNA degradation. Analyst 2021; 146:277-282. [PMID: 33135018 DOI: 10.1039/d0an01230k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
To investigate RNA degradation in live cells, detection methods that do not require RNA extraction from cells are necessary. In this study, we examined the utility of fluorescence lifetime measurements using a probe attached to the end of an RNA molecule for detecting RNA degradation. We optimized a short fluorescein-labeled RNA sequence whose fluorescence lifetime varied significantly before and after degradation. The selected HHG-fluorescein sequence (H = U, C, or A) is a promising RNA labeling unit (fluorescence lifetime probe) for live cell imaging of RNA degradation.
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Affiliation(s)
- Riku Hirata
- Department of Interdisciplinary Science and Engineering in Health Systems, Okayama University, Okayama, Japan.
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6
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Deprey K, Batistatou N, Kritzer JA. A critical analysis of methods used to investigate the cellular uptake and subcellular localization of RNA therapeutics. Nucleic Acids Res 2020; 48:7623-7639. [PMID: 32644123 PMCID: PMC7430645 DOI: 10.1093/nar/gkaa576] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/17/2020] [Accepted: 06/24/2020] [Indexed: 12/21/2022] Open
Abstract
RNA therapeutics are a promising strategy to treat genetic diseases caused by the overexpression or aberrant splicing of a specific protein. The field has seen major strides in the clinical efficacy of this class of molecules, largely due to chemical modifications and delivery strategies that improve nuclease resistance and enhance cell penetration. However, a major obstacle in the development of RNA therapeutics continues to be the imprecise, difficult, and often problematic nature of most methods used to measure cell penetration. Here, we review these methods and clearly distinguish between those that measure total cellular uptake of RNA therapeutics, which includes both productive and non-productive uptake, and those that measure cytosolic/nuclear penetration, which represents only productive uptake. We critically analyze the benefits and drawbacks of each method. Finally, we use key examples to illustrate how, despite rigorous experimentation and proper controls, our understanding of the mechanism of gymnotic uptake of RNA therapeutics remains limited by the methods commonly used to analyze RNA delivery.
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Affiliation(s)
- Kirsten Deprey
- Department of Chemistry, Tufts University, 62 Talbot Ave, Medford, MA 02155, USA
| | - Nefeli Batistatou
- Department of Chemistry, Tufts University, 62 Talbot Ave, Medford, MA 02155, USA
| | - Joshua A Kritzer
- Department of Chemistry, Tufts University, 62 Talbot Ave, Medford, MA 02155, USA
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7
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Saneyoshi H, Yamamoto Y, Ohta T, Akai S, Ono A. Thiol-responsive pro-fluorophore labeling: Synthesis of a pro-fluorescent labeled oligonucleotide for monitoring cellular uptake. Bioorg Med Chem Lett 2020; 30:127222. [PMID: 32386978 DOI: 10.1016/j.bmcl.2020.127222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 04/21/2020] [Accepted: 04/25/2020] [Indexed: 10/24/2022]
Abstract
Pro-fluorescent labeled oligonucleotides are potential alternative tools to classical fluorescently labeled oligonucleotides for monitoring cellular uptake. Here, we report the design and synthesis of a thiol-responsive pro-fluorophore labeled oligonucleotide, and its fluorescence responsivity to glutathione in the test tube and live cells.
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Affiliation(s)
- Hisao Saneyoshi
- Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan; Department of Chemistry, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu, Shiga 520-2192, Japan.
| | - Yuta Yamamoto
- Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
| | - Takayuki Ohta
- Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
| | - Shoji Akai
- Laboratory of Synthetic Organic Chemistry, Kagawa Nutrition University, 3-9-21 Chiyoda, Sakado, Saitama 350-0288, Japan
| | - Akira Ono
- Department of Material and Life Chemistry, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan.
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8
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Zhang H, Rombouts K, Raes L, Xiong R, De Smedt SC, Braeckmans K, Remaut K. Fluorescence-Based Quantification of Messenger RNA and Plasmid DNA Decay Kinetics in Extracellular Biological Fluids and Cell Extracts. ACTA ACUST UNITED AC 2020; 4:e2000057. [PMID: 32402121 DOI: 10.1002/adbi.202000057] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 02/26/2020] [Indexed: 12/22/2022]
Abstract
Extracellular and intracellular degradation of nucleic acids remains an issue in non-viral gene therapy. Understanding biodegradation is critical for the rational design of gene therapeutics in order to maintain stability and functionality at the target site. However, there are only limited methods available that allow determining the stability of genetic materials in biological environments. In this context, the decay kinetics of fluorescently labeled plasmid DNA (pDNA) and messenger RNA (mRNA) in undiluted biological samples (i.e., human serum, human ascites, bovine vitreous) and cell extracts is studied using fluorescence correlation spectroscopy (FCS) and single particle tracking (SPT). It is demonstrated that FCS is suitable to follow mRNA degradation, while SPT is better suited to investigate pDNA integrity. The half-life of mRNA and pDNA is ≈1-2 min and 1-4 h in biological samples, respectively. The resistance against biodegradation drastically improves by complexation with lipid-based carriers. Taken together, FCS and SPT are able to quantify the integrity of mRNA and pDNA, respectively, as a function of time, both in the extracellular biological fluids and cell extracts. This in turn allows to focus on the important but less understood issue of nucleic acids degradation in more detail and to rationally optimize gene delivery system as therapeutics.
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Affiliation(s)
- Heyang Zhang
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Koen Rombouts
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Laurens Raes
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Ranhua Xiong
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Stefaan C De Smedt
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Kevin Braeckmans
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
| | - Katrien Remaut
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, Ghent, 9000, Belgium
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9
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Negwer I, Best A, Schinnerer M, Schäfer O, Capeloa L, Wagner M, Schmidt M, Mailänder V, Helm M, Barz M, Butt HJ, Koynov K. Monitoring drug nanocarriers in human blood by near-infrared fluorescence correlation spectroscopy. Nat Commun 2018; 9:5306. [PMID: 30546066 PMCID: PMC6294246 DOI: 10.1038/s41467-018-07755-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 11/19/2018] [Indexed: 12/16/2022] Open
Abstract
Nanocarrier-based drug delivery is a promising therapeutic approach that offers unique possibilities for the treatment of various diseases. However, inside the blood stream, nanocarriers' properties may change significantly due to interactions with proteins, aggregation, decomposition or premature loss of cargo. Thus, a method for precise, in situ characterization of drug nanocarriers in blood is needed. Here we show how the fluorescence correlation spectroscopy that is a well-established method for measuring the size, loading efficiency and stability of drug nanocarriers in aqueous solutions can be used to directly characterize drug nanocarriers in flowing blood. As the blood is not transparent for visible light and densely crowded with cells, we label the nanocarriers or their cargo with near-infrared fluorescent dyes and fit the experimental autocorrelation functions with an analytical model accounting for the presence of blood cells. The developed methodology contributes towards quantitative understanding of the in vivo behavior of nanocarrier-based therapeutics.
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Affiliation(s)
- Inka Negwer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Pharmaceutical Chemistry, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Staudinger Weg 5, 55128, Mainz, Germany
| | - Andreas Best
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Meike Schinnerer
- Institute of Physical Chemistry, Johannes Gutenberg University, Jakob Welder Weg 11, 55128, Mainz, Germany
- Institute of Organic Chemistry, Johannes Gutenberg University, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Olga Schäfer
- Institute of Organic Chemistry, Johannes Gutenberg University, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Leon Capeloa
- Institute of Organic Chemistry, Johannes Gutenberg University, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Manfred Wagner
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Manfred Schmidt
- Institute of Physical Chemistry, Johannes Gutenberg University, Jakob Welder Weg 11, 55128, Mainz, Germany
| | - Volker Mailänder
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Department of Dermatology, University Medical Center of the Johannes Gutenberg University, Langenbeckstr. 1, 55131, Mainz, Germany
| | - Mark Helm
- Pharmaceutical Chemistry, Institute of Pharmacy and Biochemistry, Johannes Gutenberg University, Staudinger Weg 5, 55128, Mainz, Germany
| | - Matthias Barz
- Institute of Organic Chemistry, Johannes Gutenberg University, Duesbergweg 10-14, 55128, Mainz, Germany
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551, Japan.
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
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Krhac Levacic A, Morys S, Wagner E. Solid-phase supported design of carriers for therapeutic nucleic acid delivery. Biosci Rep 2017; 37:BSR20160617. [PMID: 28963371 PMCID: PMC5662914 DOI: 10.1042/bsr20160617] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/26/2017] [Accepted: 09/27/2017] [Indexed: 12/21/2022] Open
Abstract
Nucleic acid molecules are important therapeutic agents in the field of antisense oligonucleotide, RNA interference, and gene therapies. Since nucleic acids are not able to cross cell membranes and enter efficiently into cells on their own, the development of efficient, safe, and precise delivery systems is the crucial challenge for development of nucleic acid therapeutics. For the delivery of nucleic acids to their intracellular site of action, either the cytosol or the nucleus, several extracellular and intracellular barriers have to be overcome. Multifunctional carriers may handle the different special requirements of each barrier. The complexity of such macromolecules however poses a new hurdle in medical translation, which is the chemical production in reproducible and well-defined form. Solid-phase assisted synthesis (SPS) presents a solution for this challenge. The current review provides an overview on the design and SPS of precise sequence-defined synthetic carriers for nucleic acid cargos.
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Affiliation(s)
- Ana Krhac Levacic
- Pharmaceutical Biotechnology, Center for System-Based Drug Research, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Stephan Morys
- Pharmaceutical Biotechnology, Center for System-Based Drug Research, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 Munich, Germany
| | - Ernst Wagner
- Pharmaceutical Biotechnology, Center for System-Based Drug Research, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, D-81377 Munich, Germany
- Nanosystems Initiative Munich, Schellingstrasse 4, D-80799 Munich, Germany
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