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Schmitt S, Nuhn L, Barz M, Butt HJ, Koynov K. Shining Light on Polymeric Drug Nanocarriers with Fluorescence Correlation Spectroscopy. Macromol Rapid Commun 2022; 43:e2100892. [PMID: 35174569 DOI: 10.1002/marc.202100892] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/04/2022] [Indexed: 11/07/2022]
Abstract
The use of nanoparticles as carriers is an extremely promising way for administration of therapeutic agents, such as drug molecules, proteins and nucleic acids. Such nanocarriers (NCs) can increase the solubility of hydrophobic compounds, protect their cargo from the environment, and if properly functionalized, deliver it to specific target cells and tissues. Polymer-based NCs are especially promising, because they offer high degree of versatility and tunability. However, in order to get a full advantage of this therapeutic approach and develop efficient delivery systems, a careful characterization of the NCs is needed. This Feature Article highlights the fluorescence correlation spectroscopy (FCS) technique as a powerful and versatile tool for NCs characterization at all stages of the drug delivery process. In particular, FCS can monitor and quantify the size of the NCs and the drug loading efficiency after preparation, the NCs stability and possible interactions with, e.g., plasma proteins in the blood stream and the kinetic of drug release in the cytoplasm of the target cells. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Sascha Schmitt
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| | - Lutz Nuhn
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| | - Matthias Barz
- Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Hans-Jürgen Butt
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
| | - Kaloian Koynov
- Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, 55128, Germany
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2
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Pereira S, Santos RS, Moreira L, Guimarães N, Gomes M, Zhang H, Remaut K, Braeckmans K, De Smedt S, Azevedo NF. Lipoplexes to Deliver Oligonucleotides in Gram-Positive and Gram-Negative Bacteria: Towards Treatment of Blood Infections. Pharmaceutics 2021; 13:pharmaceutics13070989. [PMID: 34210111 PMCID: PMC8309032 DOI: 10.3390/pharmaceutics13070989] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/25/2021] [Accepted: 06/26/2021] [Indexed: 11/16/2022] Open
Abstract
Bacterial resistance to antibiotics threatens the ability to treat life-threatening bloodstream infections. Oligonucleotides (ONs) composed of nucleic acid mimics (NAMs) able to inhibit essential genes can become an alternative to traditional antibiotics, as long as they are safely transported in human serum upon intravenous administration and they are carried across the multilayered bacterial envelopes, impermeable to ONs. In this study, fusogenic liposomes were considered to transport the ONs and promote their internalization in clinically relevant bacteria. Locked nucleic acids and 2′-OMethyl RNA were evaluated as model NAMs and formulated into DOTAP–DOPE liposomes followed by post-PEGylation. Our data showed a complexation stability between the post-PEGylated liposomes and the ONs of over 82%, during 24 h in native human serum, as determined by fluorescence correlation spectroscopy. Quantification by a lipid-mixing assay showed that liposomes, with and without post-PEGylation, fused with all bacteria tested. Such fusion promoted the delivery of a fraction of the ONs into the bacterial cytosol, as observed by fluorescence in situ hybridization and bacterial fractionation. In short, we demonstrated for the first time that liposomes can safely transport ONs in human serum and intracellularly deliver them in both Gram-negative and -positive bacteria, which holds promise towards the treatment of bloodstream infections.
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Affiliation(s)
- Sara Pereira
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
| | - Rita Sobral Santos
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
- Correspondence: ; Tel.: +351-225-08-48-71
| | - Luís Moreira
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
| | - Nuno Guimarães
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
| | - Mariana Gomes
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
| | - Heyang Zhang
- Ghent Research Group on Nanomedicine, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium; (H.Z.); (K.R.); (K.B.); (S.D.S.)
| | - Katrien Remaut
- Ghent Research Group on Nanomedicine, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium; (H.Z.); (K.R.); (K.B.); (S.D.S.)
| | - Kevin Braeckmans
- Ghent Research Group on Nanomedicine, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium; (H.Z.); (K.R.); (K.B.); (S.D.S.)
- Centre for Advanced Light Microscopy, Ghent University, 9000 Ghent, Belgium
| | - Stefaan De Smedt
- Ghent Research Group on Nanomedicine, Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium; (H.Z.); (K.R.); (K.B.); (S.D.S.)
- Centre for Advanced Light Microscopy, Ghent University, 9000 Ghent, Belgium
| | - Nuno Filipe Azevedo
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE), Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal; (S.P.); (L.M.); (N.G.); (M.G.); (N.F.A.)
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3
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Ediriweera GR, Chen L, Yerbury JJ, Thurecht KJ, Vine KL. Non-Viral Vector-Mediated Gene Therapy for ALS: Challenges and Future Perspectives. Mol Pharm 2021; 18:2142-2160. [PMID: 34010004 DOI: 10.1021/acs.molpharmaceut.1c00297] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease, for which no effective treatment is yet available to either slow or terminate it. Recent advances in gene therapy renew hope for developing an effective approach to control this disease. Non-viral vectors, such as lipid- and polymer-based nanoparticles, cationic polymers, and exosomes, can effectively transfer genes into primary neurons. The resulting gene expression can be long-term, stable, and without immunological complications, which is essential for the effective management of neurological disorders. This Review will first describe the current research and clinical stage of novel therapies for ALS. It will then touch on the journey of non-viral vector use in ALS, subsequently highlighting the application of non-viral vector-mediated gene therapy. The bottlenecks in the translation of non-viral vectors for ALS treatment are also discussed, including the biological barriers of systemic administration and the issues of "when, where, and how much?" for effective gene delivery. The prospect of employing emerging techniques, such as CRISPR-Cas9 gene editing, stem cell methodology, and low-intensity focused ultrasound for fueling the transport of non-viral vectors to the central nervous system for personalized gene therapy, is briefly discussed in the context of ALS. Despite the challenging road that lies ahead, with the current expansion in interest and technological advancement in non-viral vector-delivered gene therapy for ALS, we hold hope that the field is headed toward a positive future.
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Affiliation(s)
- Gayathri R Ediriweera
- Centre for Advanced Imaging and Australian Institute for Bioengineering & Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Liyu Chen
- Queensland Brain Institute (QBI), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Justin J Yerbury
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia.,School of Chemistry and Molecular Bioscience, Molecular Horizons, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Kristofer J Thurecht
- Centre for Advanced Imaging and Australian Institute for Bioengineering & Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Kara L Vine
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia.,School of Chemistry and Molecular Bioscience, Molecular Horizons, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, NSW 2522, Australia
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Li T, Yang C, Wei Z, Pei D, Jiang G. <p>Recent Advances of Magnetic Nanomaterials in the Field of Oncology</p>. Onco Targets Ther 2020; 13:4825-4832. [PMID: 32547109 PMCID: PMC7266512 DOI: 10.2147/ott.s243256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Nanomagnetic devices, such as nano-field effect transistor biosensors and radio frequency magnetic induction therapies, came into being with the development of medical nanomaterials. The application of nanomagnetic materials in the treatment of cancers is rapidly becoming increasingly important because of its ability to target therapy and diagnose early. In this review, an untechnical overview of the fundamental of magnetism in nanomaterials and an illustration of how these materials are applied are presented. The applications of nano-field effect transistor biosensors for the detection of tumor biomarker nanomaterials in the therapy and diagnosis of cancers and nanomagnetic materials are summarized in this paper. A systemic summary of the use of nanomagnetic materials and nano-filed effect transistor biosensors for the treatment and diagnosis of tumors is also provided in the review.
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Affiliation(s)
- Tianyang Li
- Department of Dermatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou221002, People’s Republic of China
| | - Chunsheng Yang
- Department of Dermatology, The Affiliated Huai’an Hospital of Xuzhou Medical University, The Second People’s Hospital of Huai’an, Huai’an223002, People’s Republic of China
| | - Zhiping Wei
- Department of Dermatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou221002, People’s Republic of China
| | - Dongsheng Pei
- Department of Dermatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou221002, People’s Republic of China
| | - Guan Jiang
- Department of Dermatology, Affiliated Hospital of Xuzhou Medical University, Xuzhou221002, People’s Republic of China
- Correspondence: Guan Jiang Email
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Zhang H, De Smedt SC, Remaut K. Fluorescence Correlation Spectroscopy to find the critical balance between extracellular association and intracellular dissociation of mRNA complexes. Acta Biomater 2018; 75:358-370. [PMID: 29753914 DOI: 10.1016/j.actbio.2018.05.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/13/2018] [Accepted: 05/09/2018] [Indexed: 12/20/2022]
Abstract
Fluorescence Correlation Spectroscopy (FCS) is a promising tool to study interactions on a single molecule level. The diffusion of fluorescent molecules in and out of the excitation volume of a confocal microscope leads to the fluorescence fluctuations that give information on the average number of fluorescent molecules present in the excitation volume and their diffusion coefficients. In this context, we complexed mRNA into lipoplexes and polyplexes and explored the association/dissociation degree of complexes by using gel electrophoresis and FCS. FCS enabled us to measure the association and dissociation degree of mRNA-based complexes both in buffer and protein-rich biological fluids such as human serum and ascitic fluid, which is a clear advantage over gel electrophoresis that was only applicable in protein-free buffer solutions. Furthermore, following the complex stability in buffer and biological fluids by FCS assisted to understand how complex characteristics, such as charge ratio and strength of mRNA binding, correlated to the transfection efficiency. We found that linear polyethyleneimine prevented efficient translation of mRNA, most likely due to a too strong mRNA binding, whereas the lipid based carrier Lipofectamine® messengerMAX did succeed in efficient release and subsequent translation of mRNA in the cytoplasm of the cells. Overall, FCS is a reliable tool for the in depth characterization of mRNA complexes and can help us to find the critical balance keeping mRNA bound in complexes in the extracellular environment and efficient intracellular mRNA release leading to protein production. STATEMENT OF SIGNIFICANCE The delivery of messenger RNA (mRNA) to cells is promising to treat a variety of diseases. Therefore, the mRNA is typically packed in small lipid particles or polymer particles that help the mRNA to reach the cytoplasm of the cells. These particles should bind and carry the mRNA in the extracellular environment (e.g. blood, peritoneal fluid, …), but should release the mRNA again in the intracellular environment. In this paper, we evaluated a method (Fluorescence Correlation Spectroscopy) that allows for the in depth characterization of mRNA complexes and can help us to find the critical balance keeping mRNA bound in complexes in the extracellular environment and efficient intracellular mRNA release leading to protein production.
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Zagato E, Vermeulen L, Dewitte H, Van Imschoot G, Vandenbroucke RE, Demeester J, De Smedt SC, Neyts K, Remaut K, Braeckmans K. Quantifying the Average Number of Nucleic Acid Therapeutics per Nanocarrier by Single Particle Tracking Microscopy. Mol Pharm 2018; 15:1142-1149. [DOI: 10.1021/acs.molpharmaceut.7b00999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Elisa Zagato
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Lotte Vermeulen
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Heleen Dewitte
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Griet Van Imschoot
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Roosmarijn E. Vandenbroucke
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Jo Demeester
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Stefaan C. De Smedt
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Kristiaan Neyts
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Katrien Remaut
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
| | - Kevin Braeckmans
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University Ottergemsesteenweg 460, 9000 Ghent, Belgium
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7
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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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8
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Furst T, Dakwar GR, Zagato E, Lechanteur A, Remaut K, Evrard B, Braeckmans K, Piel G. Freeze-dried mucoadhesive polymeric system containing pegylated lipoplexes: Towards a vaginal sustained released system for siRNA. J Control Release 2016; 236:68-78. [PMID: 27329774 DOI: 10.1016/j.jconrel.2016.06.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/15/2016] [Accepted: 06/17/2016] [Indexed: 11/26/2022]
Abstract
Topical vaginal sustained delivery of siRNA presents a significant challenge due to the short residence time of formulations. Therefore, a drug delivery system capable to adhere to the vaginal mucosa is desirable, as it could allow a prolonged delivery and increase the effectiveness of the therapy. The aim of this project is to develop a polymeric solid mucoadhesive system, loaded with lipoplexes, able to be progressively rehydrated by the vaginal fluids to form a hydrogel and to deliver siRNA to vaginal tissues. To minimize adhesive interactions with vaginal mucus components, lipoplexes were coated with different derivatives of polyethylene glycol: DPSE-PEG2000, DPSE-PEG750 and ceramide-PEG2000. Based on stability and diffusion properties in simulated vaginal fluids, lipoplexes containing DSPE-PEG2000 were selected and incorporated in hydroxyethyl cellulose (HEC) hydrogels. Solid systems, called sponges, were then obtained by freeze-drying. Sponges meet acceptable mechanical characteristics and their hardness, deformability and mucoadhesive properties are not influenced by the presence of lipoplexes. Finally, mobility and stability of lipoplexes inside sponges rehydrated with vaginal mucus, mimicking in situ conditions, were evaluated by advanced fluorescence microscopy. The release rate was found to be influenced by the HEC concentration and consequently by the viscosity after rehydration. This study demonstrates the feasibility of entrapping pegylated lipoplexes into a solid matrix system for a prolonged delivery of siRNA into the vagina.
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Affiliation(s)
- Tania Furst
- Laboratory of Pharmaceutical Technology and Biopharmacy, CIRM, University of Liege, 4000, Belgium.
| | - George R Dakwar
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Ghent University, 9000, Belgium
| | - Elisa Zagato
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Ghent University, 9000, Belgium
| | - Anna Lechanteur
- Laboratory of Pharmaceutical Technology and Biopharmacy, CIRM, University of Liege, 4000, Belgium
| | - Katrien Remaut
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Ghent University, 9000, Belgium
| | - Brigitte Evrard
- Laboratory of Pharmaceutical Technology and Biopharmacy, CIRM, University of Liege, 4000, Belgium
| | - Kevin Braeckmans
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent Research Group on Nanomedicines, Ghent University, 9000, Belgium
| | - Geraldine Piel
- Laboratory of Pharmaceutical Technology and Biopharmacy, CIRM, University of Liege, 4000, Belgium
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9
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The intracellular trafficking mechanism of Lipofectamine-based transfection reagents and its implication for gene delivery. Sci Rep 2016; 6:25879. [PMID: 27165510 PMCID: PMC4863168 DOI: 10.1038/srep25879] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 04/25/2016] [Indexed: 12/23/2022] Open
Abstract
Lipofectamine reagents are widely accepted as "gold-standard" for the safe delivery of exogenous DNA or RNA into cells. Despite this, a satisfactory mechanism-based explanation of their superior efficacy has remained mostly elusive thus far. Here we apply a straightforward combination of live cell imaging, single-particle tracking microscopy, and quantitative transfection-efficiency assays on live cells to unveil the intracellular trafficking mechanism of Lipofectamine/DNA complexes. We find that Lipofectamine, contrary to alternative formulations, is able to efficiently avoid active intracellular transport along microtubules, and the subsequent entrapment and degradation of the payload within acidic/digestive lysosomal compartments. This result is achieved by random Brownian motion of Lipofectamine-containing vesicles within the cytoplasm. We demonstrate here that Brownian diffusion is an efficient route for Lipofectamine/DNA complexes to avoid metabolic degradation, thus leading to optimal transfection. By contrast, active transport along microtubules results in DNA degradation and subsequent poor transfection. Intracellular trafficking, endosomal escape and lysosomal degradation appear therefore as highly interdependent phenomena, in such a way that they should be viewed as a single barrier on the route for efficient transfection. As a matter of fact, they should be evaluated in their entirety for the development of optimized non-viral gene delivery vectors.
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10
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Rombouts K, Braeckmans K, Remaut K. Fluorescent Labeling of Plasmid DNA and mRNA: Gains and Losses of Current Labeling Strategies. Bioconjug Chem 2015; 27:280-97. [PMID: 26670733 DOI: 10.1021/acs.bioconjchem.5b00579] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Live-cell imaging has provided the life sciences with insights into the cell biology and dynamics. Fluorescent labeling of target molecules proves to be indispensable in this regard. In this Review, we focus on the current fluorescent labeling strategies for nucleic acids, and in particular mRNA (mRNA) and plasmid DNA (pDNA), which are of interest to a broad range of scientific fields. By giving a background of the available techniques and an evaluation of the pros and cons, we try to supply scientists with all the information needed to come to an informed choice of nucleic acid labeling strategy aimed at their particular needs.
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Affiliation(s)
- K Rombouts
- Laboratory of general biochemistry and physical pharmacy, Faculty of pharmacy and ‡Centre for Nano- and Biophotonics, Ghent University , Ghent 9000, Belgium
| | - K Braeckmans
- Laboratory of general biochemistry and physical pharmacy, Faculty of pharmacy and ‡Centre for Nano- and Biophotonics, Ghent University , Ghent 9000, Belgium
| | - K Remaut
- Laboratory of general biochemistry and physical pharmacy, Faculty of pharmacy and ‡Centre for Nano- and Biophotonics, Ghent University , Ghent 9000, Belgium
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11
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Hamoudi MC, Henry E, Zerrouk N, Scherman D, Arnaud P, Deprez E, Escriou V. Enhancement of siRNA lipid-based vector stability and siRNA integrity in human serum with addition of anionic polymer adjuvant. J Drug Deliv Sci Technol 2015. [DOI: 10.1016/j.jddst.2015.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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12
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Colombo S, Cun D, Remaut K, Bunker M, Zhang J, Martin-Bertelsen B, Yaghmur A, Braeckmans K, Nielsen HM, Foged C. Mechanistic profiling of the siRNA delivery dynamics of lipid-polymer hybrid nanoparticles. J Control Release 2014; 201:22-31. [PMID: 25540904 DOI: 10.1016/j.jconrel.2014.12.026] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/19/2014] [Accepted: 12/20/2014] [Indexed: 01/05/2023]
Abstract
Understanding the delivery dynamics of nucleic acid nanocarriers is fundamental to improve their design for therapeutic applications. We investigated the carrier structure-function relationship of lipid-polymer hybrid nanoparticles (LPNs) consisting of poly(DL-lactic-co-glycolic acid) (PLGA) nanocarriers modified with the cationic lipid dioleoyltrimethyl-ammoniumpropane (DOTAP). A library of siRNA-loaded LPNs was prepared by systematically varying the nitrogen-to-phosphate (N/P) ratio. Atomic force microscopy (AFM) and cryo-transmission electron microscopy (cryo-TEM) combined with small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM) studies suggested that the siRNA-loaded LPNs are characterized by a core-shell structure consisting of a PLGA matrix core coated with lamellar DOTAP structures with siRNA localized both in the core and in the shell. Release studies in buffer and serum-containing medium combined with in vitro gene silencing and quantification of intracellular siRNA suggested that this self-assembling core-shell structure influences the siRNA release kinetics and the delivery dynamics. A main delivery mechanism appears to be mediated via the release of transfection-competent siRNA-DOTAP lipoplexes from the LPNs. Based on these results, we suggest a model for the nanostructural characteristics of the LPNs, in which the siRNA is organized in lamellar superficial assemblies and/or as complexes entrapped in the polymeric matrix.
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Affiliation(s)
- Stefano Colombo
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen O, Denmark
| | - Dongmei Cun
- Department of Pharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang, Wenhua Road 103, 110016, China.
| | - Katrien Remaut
- Biophotonic Imaging Group, Lab of General Biochemistry and Physical Pharmacy, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Matt Bunker
- Molecular Profiles Ltd, 8 Orchard Place, Nottingham Business Park, Nottingham NG8 6PX, UK
| | - Jianxin Zhang
- Molecular Profiles Ltd, 8 Orchard Place, Nottingham Business Park, Nottingham NG8 6PX, UK
| | - Birte Martin-Bertelsen
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen O, Denmark
| | - Anan Yaghmur
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen O, Denmark
| | - Kevin Braeckmans
- Biophotonic Imaging Group, Lab of General Biochemistry and Physical Pharmacy, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium; Centre for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Hanne M Nielsen
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen O, Denmark.
| | - Camilla Foged
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen O, Denmark
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13
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Dakwar GR, Zagato E, Delanghe J, Hobel S, Aigner A, Denys H, Braeckmans K, Ceelen W, De Smedt SC, Remaut K. Colloidal stability of nano-sized particles in the peritoneal fluid: towards optimizing drug delivery systems for intraperitoneal therapy. Acta Biomater 2014; 10:2965-75. [PMID: 24657672 DOI: 10.1016/j.actbio.2014.03.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 03/05/2014] [Accepted: 03/11/2014] [Indexed: 02/05/2023]
Abstract
Intraperitoneal (IP) administration of nano-sized delivery vehicles containing small interfering RNA (siRNA) has recently gained attention as an alternative route for the efficient treatment of peritoneal carcinomatosis. The colloidal stability of nanomatter following IP administration has, however, not been thoroughly investigated yet. Here, enabled by advanced microscopy methods such as single particle tracking and fluorescence correlation spectroscopy, we follow the aggregation and cargo release of nano-scaled systems directly in peritoneal fluids from healthy mice and ascites fluid from a patient diagnosed with peritoneal carcinomatosis. The colloidal stability in the peritoneal fluids was systematically studied as a function of the charge (positive or negative) and poly(ethylene glycol) (PEG) degree of liposomes and polystyrene nanoparticles, and compared to human serum. Our data demonstrate strong aggregation of cationic and anionic nanoparticles in the peritoneal fluids, while only slight aggregation was observed for the PEGylated ones. PEGylated liposomes, however, lead to a fast and premature release of siRNA cargo in the peritoneal fluids. Based on our observations, we reflect on how to tailor improved delivery systems for IP therapy.
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Affiliation(s)
- George R Dakwar
- Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent Research Group on Nanomedicines, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Elisa Zagato
- Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent Research Group on Nanomedicines, Harelbekestraat 72, 9000 Ghent, Belgium; Centre for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Joris Delanghe
- Laboratory for Clinical Biology, Department of Clinical Chemistry, Microbiology and Immunology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - Sabrina Hobel
- Rudolf Boehm Institute of Pharmacology and Toxicology, Clinical Pharmacology, University Leipzig, 04107 Leipzig, Germany
| | - Achim Aigner
- Rudolf Boehm Institute of Pharmacology and Toxicology, Clinical Pharmacology, University Leipzig, 04107 Leipzig, Germany
| | - Hannelore Denys
- Department of Medical Oncology, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - Kevin Braeckmans
- Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent Research Group on Nanomedicines, Harelbekestraat 72, 9000 Ghent, Belgium; Centre for Nano- and Biophotonics, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium
| | - Wim Ceelen
- Department of Surgery, Ghent University Hospital, De Pintelaan 185, 9000 Ghent, Belgium
| | - Stefaan C De Smedt
- Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent Research Group on Nanomedicines, Harelbekestraat 72, 9000 Ghent, Belgium.
| | - Katrien Remaut
- Laboratory for General Biochemistry and Physical Pharmacy, Faculty of Pharmacy, Ghent University, Ghent Research Group on Nanomedicines, Harelbekestraat 72, 9000 Ghent, Belgium.
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14
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Rombouts K, Martens TF, Zagato E, Demeester J, De Smedt SC, Braeckmans K, Remaut K. Effect of Covalent Fluorescence Labeling of Plasmid DNA on Its Intracellular Processing and Transfection with Lipid-Based Carriers. Mol Pharm 2014; 11:1359-68. [DOI: 10.1021/mp4003078] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Koen Rombouts
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
- Centre
for Nano- and Biophotonics, Ghent University, Ghent 9000, Belgium
| | - Thomas F. Martens
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
- Centre
for Nano- and Biophotonics, Ghent University, Ghent 9000, Belgium
| | - Elisa Zagato
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
- Centre
for Nano- and Biophotonics, Ghent University, Ghent 9000, Belgium
| | - Jo Demeester
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
| | - Stefaan C. De Smedt
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
| | - Kevin Braeckmans
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
- Centre
for Nano- and Biophotonics, Ghent University, Ghent 9000, Belgium
| | - Katrien Remaut
- Laboratory
for General Biochemistry and Physical Pharmacy, Ghent University, Ghent 9000, Belgium
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15
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Symens N, Rejman J, Lucas B, Demeester J, De Smedt SC, Remaut K. Noncoding DNA in lipofection of HeLa cells-a few insights. Mol Pharm 2013; 10:1070-9. [PMID: 23421924 DOI: 10.1021/mp300569j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In cationic carrier-mediated gene delivery, the disproportional relationship between the quantity of delivered DNA and the amount of encoded protein produced is a well-known phenomenon. The numerous intracellular barriers which need to be overcome by pDNA to reach the nucleoplasm play a major role in it. In contrast to what one would expect, a partial replacement of coding pDNA by noncoding DNA does not lead to a decrease in transfection efficiency. The mechanism underlying this observation is still unclear. Therefore, we investigated which constituents of the transfection process might contribute to this phenomenon. Our data reveal that the topology of the noncoding plasmid DNA plays a major role. Noncoding pDNA can be used only in a supercoiled form to replace coding pDNA in Lipofectamine lipoplexes, without a loss in transfection levels. When noncoding pDNA is linearized or partly digested, it diminishes the transfection potential of coding pDNA, as does noncoding salmon DNA. The difference in transfection efficiencies could not be attributed to diverse physicochemical characteristics of the Lipofectamine lipoplexes containing different types of noncoding DNA or to the extent of their internalization. At the level of endosomal release, however, nucleic acid release from the endosomal compartment proceeds faster when lipoplexes contain noncoding salmon DNA. Since the half-life of pDNA in the cytosol hardly exceeds 90 min, it is conceivable that prolonged release of coding pDNA from complexes carrying supercoiled noncoding pDNA may explain its positive effect on transfection, while this depot effect does not exist when noncoding salmon DNA is used.
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Affiliation(s)
- Nathalie Symens
- Laboratory of General Biochemistry and Physical Pharmacy, Ghent University , Harelbekestraat 72, Ghent, B-9000, Belgium
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16
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17
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Koynov K, Butt HJ. Fluorescence correlation spectroscopy in colloid and interface science. Curr Opin Colloid Interface Sci 2012. [DOI: 10.1016/j.cocis.2012.09.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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18
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Troiber C, Kasper JC, Milani S, Scheible M, Martin I, Schaubhut F, Küchler S, Rädler J, Simmel FC, Friess W, Wagner E. Comparison of four different particle sizing methods for siRNA polyplex characterization. Eur J Pharm Biopharm 2012; 84:255-64. [PMID: 23079135 DOI: 10.1016/j.ejpb.2012.08.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 08/02/2012] [Accepted: 08/22/2012] [Indexed: 10/27/2022]
Abstract
The ability to reliably determine the size of siRNA polyplexes is the key for the rational design of particles and their formulation, as well as, their safe application in vivo. At the moment, no standard technique for size measurements is available. Each method has different underlying principles and hence may give different results. Here, four different analytical methods were evaluated for their suitability to analyze the characteristics of homogeneous and heterogeneous siRNA polyplexes: dynamic light scattering (DLS), atomic force microscopy (AFM), nanoparticle trafficking analysis (NTA), and fluorescence correlation spectroscopy (FCS). Three different siRNA polyplex compositions generated with different, precise, and hydrophobically modified oligoaminoamides were used in this study. All of the evaluated methods were suitable for analysis of medium sized, homogeneous siRNA polyplexes (~120 nm). Small particles (<40 nm) could not be tracked with NTA, but with the other three methods. Heterogeneous polyplexes were generally difficult to analyze. Only by visualization with AFM, the heterogeneity of those polyplexes was observable. FCS was the only method suitable for measuring polyplex stability in 90% fetal bovine serum. Physico-chemical characteristics of polyplexes are important quality criterions for successful in vivo application and future formulation development. Therefore, a comprehensive analysis by more than one method is of particular importance.
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Affiliation(s)
- Christina Troiber
- Department of Pharmacy, Pharmaceutical Biotechnology, Ludwig-Maximilians-University, Munich, Germany.
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19
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Vatansever F, Chandran R, Sadasivam M, Chiang LY, Hamblin MR. Multi-Functionality in Theranostic Nanoparticles: is more Always Better? JOURNAL OF NANOMEDICINE & NANOTECHNOLOGY 2012; 3:120. [PMID: 23565346 PMCID: PMC3615455 DOI: 10.4172/2157-7439.1000e120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Fatma Vatansever
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St., Boston, MA 02114, USA
- Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA
| | - Rakkiyappan Chandran
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St., Boston, MA 02114, USA
- Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA
- Amity Institute of Nanotechnology, Amity University Uttar Pradesh, Noida, India
| | - Magesh Sadasivam
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St., Boston, MA 02114, USA
- Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA
- Amity Institute of Nanotechnology, Amity University Uttar Pradesh, Noida, India
| | - Long Y Chiang
- Department of Chemistry, Institute of Nanoscience and Engineering Technology, University of Massachusetts, Lowell, MA 01854, USA
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Michael R. Hamblin
- Wellman Center for Photomedicine, Massachusetts General Hospital, 40 Blossom St., Boston, MA 02114, USA
- Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA
- Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA
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20
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Hyvönen Z, Hämäläinen V, Ruponen M, Lucas B, Rejman J, Vercauteren D, Demeester J, De Smedt S, Braeckmans K. Elucidating the pre- and post-nuclear intracellular processing of 1,4-dihydropyridine based gene delivery carriers. J Control Release 2012; 162:167-75. [DOI: 10.1016/j.jconrel.2012.06.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Revised: 06/01/2012] [Accepted: 06/09/2012] [Indexed: 01/20/2023]
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21
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Abstract
Employing theranostic nanoparticles, which combine both therapeutic and diagnostic capabilities in one dose, has promise to propel the biomedical field toward personalized medicine. This review presents an overview of different theranostic strategies developed for the diagnosis and treatment of disease, with an emphasis on cancer. Herein, therapeutic strategies such as nucleic acid delivery, chemotherapy, hyperthermia (photothermal ablation), photodynamic, and radiation therapy are combined with one or more imaging functionalities for both in vitro and in vivo studies. Different imaging probes, such as MRI contrast agents (T(1) and T(2) agents), fluorescent markers (organic dyes and inorganic quantum dots), and nuclear imaging agents (PET/SPECT agents), can be decorated onto therapeutic agents or therapeutic delivery vehicles in order to facilitate their imaging and, in so doing, gain information about the trafficking pathway, kinetics of delivery, and therapeutic efficacy; several such strategies are outlined. The creative approaches being developed for these classes of therapies and imaging modalities are discussed, and the recent developments in this field along with examples of technologies that hold promise for the future of cancer medicine are highlighted.
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Affiliation(s)
- Sneha S Kelkar
- Department of Chemistry and Macromolecular and Interfaces Institute Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, United States
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22
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Košovan P, Uhlík F, Kuldová J, Štěpánek M, Limpouchová Z, Procházka K, Benda A, Humpolíčková J, Hof M. Monte Carlo simulation of fluorescence correlation spectroscopy data. ACTA ACUST UNITED AC 2011. [DOI: 10.1135/cccc2009526] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We employed the Monte Carlo simulation methodology to emulate the diffusion of fluorescently labeled particles and understand the source of differences between values of diffusion coefficients (and consequently hydrodynamic radii) of fluorescently labeled nanoparticles measured by fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). We used the simulation program developed in our laboratory and studied the diffusion of spherical particles of different sizes, which are labeled on their surface. In this study, we focused on two complicating effects: (i) multiple labeling and (ii) rotational diffusion which affect the fluorescence signal from large particles and hinder the analysis of autocorrelation functions according to simple analytical models. We have shown that the fluorescence fluctuations can be well fitted using the analytical model for small point-like particles, but the obtained parameters deviate in some cases significantly from the real ones. It means that the current data treatment yields apparent values of diffusion coefficients and other parameters only and the interpretation of experimental results for systems of particles with sizes comparable to the size of the active illuminated volume requires great care and precaution.
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23
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Fluorescence Spectroscopy as a Tool for Investigating the Self-Organized Polyelectrolyte Systems. SELF ORGANIZED NANOSTRUCTURES OF AMPHIPHILIC BLOCK COPOLYMERS I 2010. [DOI: 10.1007/12_2010_56] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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24
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Grigsby CL, Leong KW. Balancing protection and release of DNA: tools to address a bottleneck of non-viral gene delivery. J R Soc Interface 2009; 7 Suppl 1:S67-82. [PMID: 19734186 DOI: 10.1098/rsif.2009.0260] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Engineering polymeric gene-delivery vectors to release an intact DNA payload at the optimal time and subcellular compartment remains a formidable challenge. An ideal vector would provide total protection of complexed DNA from degradation prior to releasing it efficiently near or within the nucleus of a target cell. While optimization of polymer properties, such as molecular weight and charge density, has proved largely inadequate in addressing this challenge, applying polymeric carriers that respond to temperature, light, pH and redox environment to trigger a switch from a tight, protective complex to a more relaxed interaction favouring release at the appropriate time and place has shown promise. Currently, a paucity of gene carriers able to satisfy the contrary requirements of adequate DNA protection and efficient release contributes to the slow progression of non-viral gene therapy towards clinical translation. This review highlights the promising carrier designs that may achieve an optimal balance of DNA protection and release. It also discusses the imaging techniques and three-dimensional in vitro models that can help study these two barriers in the non-viral gene transfer process. Ultimately, efficacious non-viral gene therapy will depend on the combination of intelligent material design, innovative imaging techniques and sophisticated in vitro model systems to facilitate the rational design of polymeric gene-delivery vectors.
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Affiliation(s)
- Christopher L Grigsby
- Department of Biomedical Engineering, Duke University, 136 Hudson Hall, Box 90281, Durham, NC 27708, USA
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25
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Braeckmans K, Vercauteren D, Demeester J, De Smedt SC. Measuring Molecular Dynamics. ACTA ACUST UNITED AC 2009. [DOI: 10.1002/imic.200990033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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26
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Li SD, Huang L. Non-viral is superior to viral gene delivery. J Control Release 2007; 123:181-3. [DOI: 10.1016/j.jconrel.2007.09.004] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2007] [Revised: 09/04/2007] [Accepted: 09/06/2007] [Indexed: 10/22/2022]
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