Michele J Writer

University College London, London, ENG, United Kingdom

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Publications (10)44.67 Total impact

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    ABSTRACT: Gadolinium-labelled nanocomplexes offer prospects for the development of real-time, non-invasive imaging strategies to visualise the location of gene delivery by MRI. In this study, targeted nanoparticle formulations were prepared comprising a cationic liposome (L) containing a Gd-chelated lipid at 10, 15 and 20% by weight of total lipid, a receptor-targeted, DNA-binding peptide (P) and plasmid DNA (D), which electrostatically self-assembled into LPD nanocomplexes. The LPD formulation containing the liposome with 15% Gd-chelated lipid displayed optimal peptide-targeted, transfection efficiency. MRI conspicuity peaked at 4h after incubation of the nanocomplexes with cells, suggesting enhancement by cellular uptake and trafficking. This was supported by time course confocal microscopy analysis of transfections with fluorescently-labelled LPD nanocomplexes. Gd-LPD nanocomplexes delivered to rat brains by convection-enhanced delivery were visible by MRI at 6h, 24h and 48h after administration. Histological brain sections analysed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) confirmed that the MRI signal was associated with the distribution of Gd(3+) moieties and differentiated MRI signals due to haemorrhage. The transfected brain cells near the injection site appeared to be mostly microglial. This study shows the potential of Gd-LPD nanocomplexes for simultaneous delivery of contrast agents and genes for real-time monitoring of gene therapy in the brain.
    Journal of Controlled Release 07/2012; 162(2):340-8. · 7.63 Impact Factor
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    ABSTRACT: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used to map the spatial distribution of magnetic resonance imaging (MRI) contrast agents (Gd-based) in histological sections in order to explore synergies with in vivo MRI. Images from respective techniques are presented for two separate studies namely (1) convection enhanced delivery of a Gd nanocomplex (developmental therapeutic) into rat brain and (2) convection enhanced delivery, with co-infusion of Magnevist (commercial Gd contrast agent) and Carboplatin (chemotherapy drug), into pig brain. The LA technique was shown to be a powerful compliment to MRI not only in offering improved sensitivity, spatial resolution and signal quantitation but also in giving added value regarding the fate of administered agents (Gd and Pt agents). Furthermore simultaneous measurement of Fe enabled assignment of an anomalous contrast enhancement region in rat brain to haemorrhage at the infusion site.
    Analytical and Bioanalytical Chemistry 04/2012; 403(6):1641-9. · 3.66 Impact Factor
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    ABSTRACT: A range of monocationic and dicationic dioxyalkylglycerol cytofectins have been synthesised possessing methylene and short n-ethylene glycol spacers. The monocationic compounds were found to be effective in transfections when formulated as lipopolyplexes with peptide and DNA components, in particular with shorter PEG head groups which may have less effect on peptide targeting in the ternary complex.
    Organic & Biomolecular Chemistry 08/2008; 6(14):2554-9. · 3.57 Impact Factor
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    ABSTRACT: Synthetic vectors for cystic fibrosis (CF) gene therapy are required that efficiently and safely transfect airway epithelial cells, rather than alveolar epithelial cells or macrophages, and that are nonimmunogenic, thus allowing for repeated delivery. We have compared several vector systems against these criteria including GL67, polyethylenimine (PEI) 22 and 25 kd and two new, synthetic vector formulations, comprising a cationic, receptor-targeting peptide K(16)GACSERSMNFCG (E), and the cationic liposomes (L) DHDTMA/DOPE or DOSEP3/DOPE. The lipid and peptide formulations self assemble into receptor-targeted nanocomplexes (RTNs) LED-1 and LED-2, respectively, on mixing with plasmid (D). LED-1 transfected airway epithelium efficiently, while LED-2 and GL67 preferentially transfected alveolar cells. PEI transfected airway epithelial cells with high efficiency, but was more toxic to the mice than the other formulations. On repeat dosing, LED-1 was equally as effective as the single dose, while GL67 was 30% less effective and PEI 22 kd displayed a 90% reduction of efficiency on repeated delivery. LED-1 thus was the only formulation that fulfilled the criteria for a CF gene therapy vector while GL67 and LED-2 may be appropriate for other respiratory diseases. Opportunities for PEI depend on a solution to its toxicity problems. LED-1 formulations were stable to nebulization, the most appropriate delivery method for CF.
    Molecular Therapy 06/2008; 16(5):907-15. · 7.04 Impact Factor
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    ABSTRACT: Improving the buffer and serum stability of non-viral gene delivery vectors, and increasing their circulation time in vivo, is an important focus of current research in gene therapy. The most successful strategies to date have involved shielding the complexes with large polydisperse PEG adducts. However, this approach is accompanied by a fall in transfection efficiency. In this paper we describe the solid-phase synthesis of a series of bifunctional peptides bearing short PEG spacers of defined structure as components of lipopolyplex gene delivery vectors. Short, high-yielding routes to a series of PEG-amino acids are described: these PEG-amino acids can be used in varying combinations to afford bifunctional peptides with varying lengths of PEG spacers by using standard solid-phase synthesis techniques. A series of lipopolyplexes were formulated using these bifunctional peptides, and their transfection properties assessed. Dynamic light scattering measurements on the complex with the best transfection properties showed that in phosphate-buffered saline this complex was considerably more stable, and aggregated more slowly, than a complex formulated using a similar peptide lacking the short PEG spacer.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
    Annalen der Chemie und Pharmacie 01/2008; 2008(17):2900-2914. · 3.10 Impact Factor
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    ABSTRACT: Nonviral gene delivery vectors now show good therapeutic potential: however, detailed characterization of the composition and macromolecular organization of such particles remains a challenge. This paper describes experiments to elucidate the structure of a ternary, targeted, lipopolyplex synthetic vector, the LID complex. This consists of a lipid component, Lipofectin (L) (1:1 DOTMA:DOPE), plasmid DNA (D), and a dual-function, cationic peptide component (I) containing DNA condensation and integrin-targeting sequences. Fluorophore-labeled lipid, peptide, and DNA components were used to formulate the vector, and the stoichiometry of the particles was established by fluorescence correlation spectroscopy (FCS). The size of the complex was measured by FCS, and the sizes of LID, L, LD, and ID complexes were measured by dynamic light scattering (DLS). Fluorescence quenching experiments and freeze-fracture electron microscopy were then used to demonstrate the arrangement of the lipid, peptide, and DNA components within the complex. These experiments showed that the cationic portion of the peptide, I, interacts with the plasmid DNA, resulting in a tightly condensed DNA-peptide inner core; this is surrounded by a disordered lipid layer, from which the integrin-targeting sequence of the peptide partially protrudes.
    Biochemistry 12/2007; 46(45):12930-44. · 3.38 Impact Factor
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    ABSTRACT: We have developed efficient synthetic routes to two hydrophobic amino acids, suitably protected for solid-phase peptide synthesis, and have successfully synthesized peptides containing these or other hydrophobic amino acids as spacers between a Lys16 moiety and an integrin-targeting motif. These peptides have in turn been used to formulate a range of lipopolyplex vectors with Lipofectin and plasmid DNA. The transfection efficiencies of these vectors and their aggregation behavior in buffers and in serum have been studied. We have shown that vectors containing peptides incorporating long linkers that are entirely hydrophobic are less efficient transfection agents. However, linkers of equivalent length that are in part hydrophobic show improved transfection properties, which is probably due to the improved accessibility of the integrin-binding motif.
    Bioconjugate Chemistry 10/2007; 18(6):1800-10. · 4.58 Impact Factor
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    ABSTRACT: Molecular Therapy (2006) 13, S269|[ndash]|S270; doi: 10.1016/j.ymthe.2006.08.774 696. Development of Lipid/Peptide (Lip/Tide) Vectors for Respiratory Gene Transfer Stephen L. Hart1,|[ast]|, Aris Tagalakis1, Michele J. Writer1, James Devaney1, Helen C. Hailes2, Alethea B. Tabor2, John B. Wong2, Steve Bottoms3, Robin J. McAnulty3, Ron Scheule4, Seng Cheng4 and Adam Jaffe11Molecular Immunology Unit, UCL Institute of Child Health, London, United Kingdom2Department of Chemistry, University College London, London, United Kingdom3Centre for Respiratory Research, University College London, London, United Kingdom4Genetic Diseases Science, Genzyme Corporation, Framingham, MA|[ast]|SH has equity in Genex Biosystems Ltd, a company set up to commercially exploit Lip/Tide vector technology.
    Molecular Therapy 04/2006; · 7.04 Impact Factor
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    ABSTRACT: We have previously described a lipopolyplex formulation comprising a mixture of a cationic peptide with an integrin-targeting motif (K16GACRRETAWACG) and Lipofectin, a liposome consisting of DOTMA and DOPE in a 1:1 ratio. The high transfection efficiency of the mixture involved a synergistic interaction between the lipid/peptide components. The aim of this study was to substitute the lipid component of the lipopolyplex to optimize transfection further and to seek information on the structure-activity relationship of the lipids in the lipopolyplex. Symmetrical cationic lipids with diether linkages that varied in alkyl chain length were formulated into liposomes and then incorporated into a lipopolyplex by mixing with an integrin-targeting peptide and plasmid DNA. Luciferase transfections were performed of airway epithelial cells and fibroblasts in vitro and murine lung airways in vivo. The biophysical properties of lipid structures and liposome formulations and their potential effects on bilayer membrane fluidity were determined by differential scanning calorimetry and calcein-release assays. Shortening the alkyl tail from C18 to C16 or C14 enhanced lipopolyplex and lipoplex transfection in vitro but with differing effects. The addition of DOPE enhanced transfection when formulated into liposomes with saturated lipids but was more variable in its effects with unsaturated lipids. A substantial improvement in transfection efficacy was seen in murine lung transfection with unsaturated lipids with 16 carbon alkyl tails. The optimal liposome components of lipopolyplex and lipoplex vary and represent a likely compromise between their differing structural and functional requirements for complex formation and endosomal membrane destabilization.
    Journal of Liposome Research 02/2006; 16(4):373-89. · 1.91 Impact Factor
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    ABSTRACT: Human airway epithelial cell targeting peptides were identified by biopanning on 1HAEo-cells, a well characterised epithelial cell line. Bound phage were recovered after three rounds of binding, high stringency washing and elution, leading to the production of an enriched phage peptide population. DNA sequencing of 56 clones revealed 14 unique sequences. Subsequent binding analysis revealed that 13 of these peptides bound 1HAEo-cells with high affinity. Three peptides, SERSMNF, YGLPHKF and PSGAARA were represented at high frequency. Three clearly defined families of peptide were identified on the basis of sequence motifs including (R/K)SM, L(P/Q)HK and PSG(A/T)ARA. Two peptides, LPHKSMP and LQHKSMP contained two motifs. Further detailed sequence analysis by comparison of peptide sequences with the SWISSPROT protein database revealed that some of the peptides closely resembled the cell binding proteins of viral and bacterial pathogens including Herpes Simplex Virus, rotavirus, Mycoplasma pneumoniae and rhinovirus, the latter two being respiratory pathogens, as well as peptide YGLPHKF having similarity to a protein of unknown function from the respiratory pathogen Legionella pneumophila. Peptides were incorporated into gene delivery formulations with the cationic lipid Lipofectin and plasmid DNA and shown to confer a high degree of transfection efficiency and specificity in 1HAEo-cells. Improved transfection efficiency and specificity was also observed in human endothelial cells, fibroblasts and keratinocytes. Therefore, on the basis of clone frequency after biopanning, cell binding affinity, peptide sequence conservation and pathogenic similarity, we have identified 3 novel peptide families and 5 specific peptides that have the potential for gene transfer to respiratory epithelium in vivo as well as providing useful in vitro transfection reagents for primary human cell types of scientific and commercial interest.
    Journal of Drug Targeting 06/2004; 12(4):185-93. · 2.77 Impact Factor