Publications 2011/2012

ACN PUBLICATIONS 2011/2012

Nature Communications (DOI: 10.1038/ncomms2273)

Sub-resolution lipid domains exist in the plasma membrane and regulate protein diffusion and distribution

Dylan M Owen,  David J Williamson, Astrid Magenau, Katharina Gaus

 

 Phasor plots of the order-sensitive membrane dye Laurdan in model bilayers.

Lipid microdomains are postulated to regulate many membrane-associated processes but have remained highly controversial. Here we provide the first direct evidence that the plasma membrane of intact, live cells is comprised of a sub-resolution mixture of approximately 76% ordered and 24% disordered lipid domains, which correspond to liquid-ordered and -disordered model membranes. These measurements were based on the unmixing of fluorescence lifetime decays (phasor analysis) obtained from environmentally sensitive membrane dyes that report the degree of lipid packing. Using the transmembrane protein Linker for Activation of T cells (LAT) as an example, we demonstrate that association with ordered domains retarded LAT diffusion and decreased clustering in meso-scaled protein domains as analysed by super-resolution microscopy. Our data therefore propose a membrane model in which the majority of the plasma membrane is covered by cholesterol-dependent, ordered lipid domains that contribute to the non-random distribution and diffusion of membrane constituents.

Centre for Vascular Research and Australian Centre for Nanomedicine, University of New South Wales, High Street Sydney New South Wales 2052 Australia

  

Australian Society for Biochemistry and Molecular Biology (Volume 43, No. 3, December 2012)

Nanotechnology in Therapeutics

2012december-cover.jpg 
  

Nature Immunology (DOI: 10.1038/ni.2488)

Conformational states of the kinase Lck regulate clustering in early T cell signaling

Jérémie Rossy, Dylan M Owen, David J Williamson, Zhengmin Yang, Katharina Gaus

TCR activation recruits Lck into pre-existing clusters. 
Phosphorylation of the T cell antigen receptor (TCR) by the tyrosine kinase Lck is an essential step in the activation of T cells. Because Lck is constitutively active, spatial organization may regulate TCR signaling. Here we found that Lck distributions on the molecular level were controlled by the conformational states of Lck, with the open, active conformation inducing clustering and the closed, inactive conformation preventing clustering. In contrast, association with lipid domains and protein networks were not sufficient or necessary for Lck clustering. Conformation-driven Lck clustering was highly dynamic, so that TCR triggering resulted in Lck clusters that contained phosphorylated TCRs but excluded the phosphatase CD45. Our data suggest that Lck conformational states represent an intrinsic mechanism for the intermolecular organization of early T cell signaling. 

1Centre for Vascular Research and Australian Centre for Nanomedicine, University of New South Wales Sydney Australia

  

Frontiers of Immunology (DOI: 10.3389/fimmu.2012.00352)

The integration of signaling and the spatial organization of the T cell synaps

Jérémie Rossy, David J Williamson, Carola Benzingand Katharina Gaus*

 www.frontiersin.org

Engagement of the T cell antigen receptor (TCR) triggers signaling pathways that lead to T cell selection, differentiation and clonal expansion. Superimposed onto the biochemical network is a spatial organization that describes individual receptor molecules, dimers, oligomers and higher order structures. Here we discuss recent findings and new concepts that may regulate TCR organization in naïve and memory T cells. A key question that has emerged is how antigen-TCR interactions encode spatial information to direct T cell activation and differentiation. Single molecule super-resolution microscopy may become an important tool in decoding receptor organization at the molecular level.

1Centre for Vascular Research and Australian Centre for NanoMedicine, University of New South Wales Sydney NSW Australia

  

Chemical Communications (DOI: 10.1039/C2CC37181B )

Intracellular nitric oxide delivery from stable NO-polymeric nanoparticle carriers

Hien T T Duong,a Zulkamal M Kamarudin,a Rafael B Erlich,ab Yang Li,a Mathew W Jones,a Maria Kavallaris,ab Cyrille Boyer*a, Thomas P Davis*a

 chemicalcommunicationsnov2012
The encapsulation of S-nitrosoglutathione into polymeric nanoparticles substantially improves NO stability in aqueous media without affecting the efficacy of intracellular delivery. The combination of nano-NO delivery and chemotherapy has been found to enhance antitumour activity of chemotherapeutics, as demonstrated using preliminary in vitro experiments with neuroblastoma cells.

aAustralian Centre for NanoMedicine, School of Chemical Engineering, University of New South Wales Sydney NSW 2052 Australia bChildren’s Cancer Institute Australia, Lowy Cancer Research Centre, University of New South Wales Sydney NSW 2052 Australia

  

Angiogenesis DOI 10.1007/s10456-012-9321-x

Concentration- and schedule-dependent effects of chemotherapy on the angiogenic potential and drug sensitivity of vascular endothelial cells

Eddy Pasquier12, Maria-Pia Tuset1, Janine Street1, Snega Sinnappan16, Karen L MacKenzie1, Diane Braguer3, Nicolas Andre234, Maria Kavallaris15

Angiogenesis 

The anti-angiogenic activity of chemotherapy is both dose- and schedule-dependent. While conventional maximum tolerated dose (MTD) chemotherapy exerts only mild and reversible anti-angiogenic effects, low-dose metronomic (LDM) chemotherapy was developed to specifically target tumour angiogenesis. However, the long-term effects of either MTD or LDM chemotherapy on vascular endothelial cells have never been investigated. Here, we demonstrated that repeated exposure to MTD and LDM chemotherapy differentially impact on the angiogenic potential and chemosensitivity of immortalized endothelial cells. Repeated MTD vinblastine treatment of vascular endothelial cells led to an increased proliferation rate and resistance to paclitaxel. In contrast, repeated LDM treatment with vinblastine or etoposide impaired the angiogenic potential of endothelial cells and increased their chemosensitivity. This effect was associated with a significant decrease in βII- and βIII-tubulin expression. Functional analysis using siRNA showed that silencing the expression of βIII-tubulin in endothelial cells significantly decreased their capacity to form vascular structures and increased their sensitivity to the anti-angiogenic and vascular-disrupting effects of chemotherapy, whereas silencing βII-tubulin expression had no effect. Collectively our results show that LDM chemotherapy impairs the angiogenic potential of endothelial cells while increasing their chemosensitivity—an effect at least in part mediated by the down-regulation of βIII-tubulin expression. Furthermore, our study suggests that βIII-tubulin represents an attractive therapeutic target to increase the anti-angiogenic effects of chemotherapy and overall anti-tumour efficacy.

1Children’s Cancer Institute Australia for Medical Research, Lowy Cancer Research Centre, UNSW PO Box 81 Randwick NSW 2031 Australia 2Metronomics Global Health Initiative, Marseille France 3Faculty of Pharmacy, INSERM UMR 911, Centre de Recherche en Oncologie biologique et Oncopharmacologie, Aix-Marseille University Marseille France 4Hematology and Pediatric Oncology Department, La Timone University Hospital of Marseille, Marseille France 5Australian Centre for Nanomedicine, University of New South Wales Kensington NSW 2051 Australia (6)Present address: Kolling Institute of Medical Research, Royal North Shore Hospital, St Leonards NSW 2065 Australia

  

Chemical Communications (DOI 10.1039/c2cc35954e)

One-pot synthesis of colloidal silicon quantum dots and surface functionalization via thiol–ene click chemistry

Xiaoyu Cheng,aRichard Gondosiswanto,aSimone Ciampi,aPeter J Reeceb, J Justin Gooding*a

cc48 

 A solution method for preparing surface functionalized colloidal silicon quantum dots (SiQDs) is presented. SiQDs prepared by this method are reasonably monodispersed and can be further functionalized via thiol–ene click reactions to introduce specific functionalities (i.e. –NH2, –COOH, –SO3, alkane, alkene).

aSchool of Chemistry and Australian Centre for NanoMedicine, University of New South Wales Sydney NSW 2052 Australia bSchool of Physics, University of New South Wales Sydney Australia

  

Langmuir 2012, 28(44), pp 15444–15449 DOI: 10.1021/la303649u

Depth-Resolved Chemical Modification of Porous Silicon by Wavelength-Tuned Irradiation

Bin Guan, Simone Ciampi, Erwann Luais, Michael James§, Peter J Reece, J Justin Gooding*†

 langd5 2012 28 issue-44 cover

The ability to impart discrete surface chemistry to the inside and outside of mesoporous silicon is of great importance for a range of biomedical applications, from selective (bio)sensing to tissue-specific drug delivery. Here we present a generic strategy toward achieving depth-resolved functionalization of the external and internal porous surfaces by a simple change in the wavelength of the light being used to promote surface chemical reactions. UV-assisted hydrosilylation, limited by the penetration depth of UV light, is used to decorate the outside of the mesoporous structure with carboxylic acid molecules, and white light illumination triggers the attachment of dialkyne molecules to the inner porous matrix.

School of Chemistry and the Australian Centre for Nanomedicine and  School of Physics, University of New South Wales Sydney 2052 Australia § Bragg Institute, Building 87, Australian Nuclear Science and Technology Organisation, Locked Bag 2001 Kirrawee DC 2232 Australia

  

Molecular Pharmaceutics (DOI: 10.1021/mp300144)

Functionalizing Biodegradable Dextran Scaffolds Using Living Radical Polymerization: New Versatile Nanoparticles for the Delivery of Therapeutic Molecules

Hien TT Duong, Felicity Hughes, Sharon Sagnella†‡, Maria Kavallaris†‡, Alexander Macmillan§, Renee Whan§, James Hook?, Thomas P Davis*†, Cyrille Boyer*†

 mp-2012-00144y 0016

Conferring biodegradability to nanoparticles is vitally important when nanomedicine applications are being targeted, as this prevents potential problems with bioaccumulation of byproducts after delivery. In this work, dextran has been modified (and rendered hydrophobic) by partial acetalation. A solid state NMR method was first developed to fully characterize the acetalated polymers. In a subsequent synthetic step, RAFT functionality was attached via residual unmodified hydroxyl groups. The RAFT groups were then used in a living free radical polymerization reaction to control the growth of hydrophilic PEG-methacrylate chains, thereby generating amphiphilic comblike polymers. The amphiphilic polymers were then self-assembled in water to form various morphologies, including small vesicles, wormlike rods, and micellar structures, with PEG at the periphery acting as a nonfouling biocompatible polymer layer. The acetalated dextran nanoparticles were designed for potential doxorubicin (DOX) delivery application based on the premise that in the cell compartments (endosome, lysozome) the acetalated dextran would hydrolyze, destroying the nanoparticle structure, releasing the encapsulated DOX. In-vitro studies confirmed minimal cytotoxicity of the (unloaded) nanoparticles, even after 3 days, proving that the hydrolysis products from the acetal groups (methanol and acetone) had no observable cytotoxic effect. An intriguing initial result is reported that in vitro studies of DOX-loaded dextran-nanoparticles (compared to free DOX) revealed an increased differential toxicity toward a cancer cell line when compared to a normal cell line. Efficient accumulation of DOX in a human neuroblastoma cell line (SY-5Y) was confirmed by both confocal microscopy and flow cytometry measurements. Furthermore, the time dependent release of DOX was monitored using fluorescence lifetime imaging microscopy (FLIM) in SY-5Y live cells. FLIM revealed bimodal lifetime distributions, showing the accumulation of both DOX-loaded dextran-nanoparticles and subsequent release of DOX in the living cells. From FLIM data analysis, the amount of DOX released in SY-5Y cells was found to increase from 35% to 55% when the incubation time increased from 3 h to 24 h.

Australian Centre for NanoMedicineChildren’s Cancer Institute Australia, Lowy Cancer Research Centre, §Biomedical Imaging Facility, Mark Wainwright Analytical Centre, ?Nuclear Magnetic Resonance Facility, Mark Wainwright Analytical Centre, University of New South Wales Sydney NSW 2052 Australia

  

Journal of Material Chemistry (Issue 2012 22 21382-21386)

Polymer–gold nanohybrids with potential use in bimodal MRI/CT: enhancing the relaxometric properties of Gd(III) complexes

Mariana Beija,a Yang Li,a Hien T Duong,a Sophie Laurent,bLuce Vander Elst,bRobert N Muller,bc Andrew B Lowe,*d Thomas P Davis*aand Cyrille Boyer*a

 coverissuejmc

We present a new synthetic strategy to produce Gd(III)-decorated gold nanoparticles (AuNPs) for potential use as bimodal contrast agents (CA) for computed X-ray tomography (CT) and magnetic resonance imaging (MRI). The hybrid AuNPs exhibit high molar relaxivities (>12000 mM−1 s−1 per particle), indicative of highly efficient CT/MRI CAs.

aAustralian Centre for NanoMedicine, School of Chemical Engineering, University of New South Wales Sydney NSW 2052 Australiadress is being protected from spambots. You need JavaScript enabled to view it   This e-mail address is being protected from spambots. You need JavaScript enabled to view it bNMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry, University of Mons 7000 Mons Belgium cCenter for Microscopy and Molecular Imaging, Rue Adrienne Bolland 8 6041 Charleroi Belgium dCentre for Advanced Macromolecular Design, University of New South Wales Sydney NSW 2052 Australia

  

Polymer Chemistry (DOI: 10.1039/C2PY20112G)

Synthesis, self-assembly and stimuli responsive properties of cholesterol conjugated polymers

Sema Sevimli,a Sharon Sagnella,a Maria Kavallaris,ac Volga Bulmusb, Thomas P Davis*a

 Journal cover: Polymer Chemistry

Reversible addition–fragmentation chain transfer (RAFT) polymerization was used to generate well-defined pH-responsive biofunctional polymers as potential ‘smart’ gene delivery systems. A series of five poly(dimethylamino ethyl methacrylate-co-cholesteryl methacrylate) P(DMAEMA-co-CMA) statistical copolymers, with similar molecular weights and varying cholesterol content, were prepared. The syntheses, compositions and molecular weight distributions for P(DMAEMA-co-CMA) were monitored by nuclear magnetic resonance (NMR), solid-state NMR and gel permeation chromatography (GPC) evidencing well-defined polymeric structures with narrow polydispersities. Aqueous solution properties of the copolymers were investigated using turbidimetry and light scattering to determine hydrodynamic diameters and zeta potentials associated with the phase transition behaviour of P(DMAEMA-co-CMA) copolymers. UV-Visible spectroscopy was used to investigate the pH-responsive behaviour of copolymers. Hydrodynamic radii were measured in the range 10–30 nm (pH, temperature dependent) by dynamic light scattering (DLS). Charge studies indicated that P(DMAEMA-co-CMA) polymers have an overall cationic charge, mediated by pH. Potentiometric studies revealed that the buffering capacity and pKa values of polymers were dependent on cholesterol content as well as on cationic charge. The buffering capacity increased with increasing charge ratio, overall demonstrating transitions in the pH endosomal region for all five copolymeric structures. Cell viability assay showed that the copolymers displayed increasing cytotoxicity with decreasing number of cholesterol moieties. These preliminary results show the potential of these well-defined P(DMAEMA-co-CMA) polymers as in vitro siRNA delivery agents.

aAustralian Centre for Nanomedicine, University of New South Wales Sydney NSW 2052 Australia This e-mail address is being protected from spambots. You need JavaScript enabled to view it bDepartment of Chemical Engineering, Izmir Institute of Technology, Gulbahce I_zmir 35430 Turkey cChildren’s Cancer Institute Australia, Lowy Cancer Research Centre, University of New South Wales Sydney NSW 2052 Australia

  

Communitative and Integrative Biology (DOI: 10.4161/cib.20348)

Fluorescence localization microscopy: The transition from concept to biological research tool

Dylan M Owen, Markus Sauer*, Katharina Gaus*

 communitativeintegrativebiologyimage.jpg
  
Localization microscopy techniques are super-resolution fluorescence imaging methods based on the detection of individual molecules. Despite the relative simplicity of the microscope setups and the availability of commercial instruments, localization microscopy faces unique challenges. While achieving super-resolution is now routine, issues concerning data analysis and interpretation mean that revealing novel biological insights is not. Here, we outline why data analysis and the design of robust test samples may hold the key to harness the full potential of localization microscopy.
 

Dylan M Owen, Centre for Vascular Research and the Australian Centre for NanoMedicine; University of New South Wales Sydney NSW Australia; Markus Sauer,Department of Biotechnology & Biophysics; Julius-Maximilians-University Würzburg; Würzburg, Germany; Katharina Gaus, Centre for Vascular Research and the Australian Centre for NanoMedicine; University of New South Wales Sydney NSW Australia

  

Angewandte Chemie DOI: 10.1002/anie.201202118

Using an Electrical Potential to Reversibly Switch Surfaces between Two States for Dynamically Controlling Cell Adhesion

Cheuk Chi Albert Ng1, Astrid Magenau2, Siti Hawa Ngalim2, Simone Ciampi1, Muthukumar Chockalingham1, Jason Brian Harper1, Katharina Gaus2, John Justin Gooding1,*

Angewandte Chemie International Edition 
Smart surfaces presenting both antifouling molecules with a charged functional group at their distal end, and molecules that are terminated by RGD peptides for cell adhesion, were fabricated and characterized (see picture). By applying potentials of +300 or −300 mV, the surfaces could be dynamically switched to make the peptide accessible or inaccessible to cells.

1A Ng, S Ciampi, M Chockalingham, J Harper, J Gooding School of Chemistry and Australian Centre for NanoMedicine, University of New South Wales Sydney NSW 2052 Australiacted from spambots. You need JavaScript enabled to view it  his e-mail address is being protected from spambots. You need JavaScript enabled to view it 2A Magenau, S Ngalim, K Gaus Centre for Vascular Research and Australian Centre for NanoMedicine University of New South Wales Sydney NSW 2052 Australia

  

BioEssays (DI: 10.1002/bies.201200044)

The lipid raft hypothesis revisited – New insights on raft composition and function from super-resolution fluorescence microscopy

Dylan M. Owen*, Astrid Magenau, David Williamson, Katharina Gaus

BioEssays

Recently developed super-resolution microscopy techniques are changing our understanding of lipid rafts and membrane organisation in general. The lipid raft hypothesis postulates that cholesterol can drive the formation of ordered domains within the plasma membrane of cells, which may serve as platforms for cell signalling and membrane trafficking. There is now a wealth of evidence for these domains. However, their study has hitherto been hampered by the resolution limit of optical microscopy, making the definition of their properties problematic and contentious. New microscopy techniques circumvent the resolution limit and, for the first time, allow the fluorescence imaging of structures on length scales below 200 nm. This review describes such techniques, particularly as applied to the study of membrane organisation, synthesising newly emerging facets of lipid raft biology into a state-of-the art model.

1Centre for Vascular Research and Australian Centre for NanoMedicine, University of New South Wales Sydney Australia

  

Book: Maria Kavallaris (Editor) Cytoskeleton and Human Disease.

The cytoskeleton is made up of a large variety of specialized proteins and is a highly dynamic system that is involved in the majority of key cellular events. It is now clear that the cytoskeleton is often associated, and has diverse roles in human disease. Emerging understanding of the molecular and cellular events that drive cytoskeletal mediated disease including cancer, heart disease, myopathies, neurodegenerative diseases and skin disorders, are also helping shape targeted therapeutic approaches to treat these diseases.

Cytoskeleton and Human Disease Book Summary reviews the key components, mechanisms and clinical implications of cytoskeletal defects in disease. Contributed by leading investigators in their respective fields, the chapters include topics associated with the basics of the cytoskeleton, actin-associated disease states, microtubule-associated disease states and intermediate filament-associated disease states.

This authoritative volume is intended for a wide audience of clinicians, researchers and students with an interest in the application of biomedical research to the understanding and management of disease states associated with the cytoskeleton.

 Cytoskeleton and Human Disease
  

Angewandte Chemie: DOI: 10.1002/anie.201202350

The Biochemiresistor: An Ultrasensitive Biosensor for Small Organic Molecules

Leo M H Lai1, Ian Y Goon2, Kyloon Chuah1, May Lim2, Filip Braet3, Rose Amal2, J Justin Gooding1,*

 Angewandte Chemie International Edition

New sensation: A resistance-based biosensor uses gold-coated magnetic nanoparticles (Au@MNPs) functionalized with the antibiotic enrofloxin (see picture; purple), which bind to anti-enrofloxin as analyte (blue). The Au@MNPs can be magnetically assembled between electrodes, and the measured resistance R is a function of analyte concentration.

*L M H Lai, K Chuah, J J Gooding School of Chemistry and the Australian Centre for NanoMedicine University of New South Wales, Sydney NSW 2052 Australia; mail address is being protected from spambots. You need JavaScript enabled to view it  I Y Goon, M Lim, R Amal ARC Centre of Excellence for Functional Nanomaterials School of Chemical Engineering University of New South Wales, Sydney NSW 2052 Australia; F Braet Australian Centre for Microscopy & Microanalysis and School of Medical Sciences (Discipline of Anatomy and Histology) The Bosch Institute, University of Sydney Sydney NSW 2006 Australia

  

Polymer Chemistry 2012 Advanced Articles (DOI: 10.1039/C2PY20112G)

Synthesis, self-assembly and stimuli responsive properties of cholesterol conjugated polymers

Sema Sevimli,a Sharon Sagnella,a Maria Kavallaris,ac Volga Bulmusb, Thomas P. Davis*a

 

 

 gav3
 Reversible addition–fragmentation chain transfer (RAFT) polymerization was used to generate well-defined pH-responsive biofunctional polymers as potential ‘smart’ gene delivery systems. A series of five poly(dimethylamino ethyl methacrylate-co-cholesteryl methacrylate) P(DMAEMA-co-CMA) statistical copolymers, with similar molecular weights and varying cholesterol content, were prepared. The syntheses, compositions and molecular weight distributions for P(DMAEMA-co-CMA) were monitored by nuclear magnetic resonance (NMR), solid-state NMR and gel permeation chromatography (GPC) evidencing well-defined polymeric structures with narrow polydispersities. Aqueous solution properties of the copolymers were investigated using turbidimetry and light scattering to determine hydrodynamic diameters and zeta potentials associated with the phase transition behaviour of P(DMAEMA-co-CMA) copolymers. UV-Visible spectroscopy was used to investigate the pH-responsive behaviour of copolymers. Hydrodynamic radii were measured in the range 10–30 nm (pH, temperature dependent) by dynamic light scattering (DLS). Charge studies indicated that P(DMAEMA-co-CMA) polymers have an overall cationic charge, mediated by pH. Potentiometric studies revealed that the buffering capacity and pKa values of polymers were dependent on cholesterol content as well as on cationic charge. The buffering capacity increased with increasing charge ratio, overall demonstrating transitions in the pH endosomal region for all five copolymeric structures. Cell viability assay showed that the copolymers displayed increasing cytotoxicity with decreasing number of cholesterol moieties. These preliminary results show the potential of these well-defined P(DMAEMA-co-CMA) polymers as in vitro siRNA delivery agents.

aAustralian Centre for Nanomedicine (ACN), The University of New South Wales, Sydney, NSW 2052, Australia. E-mail: t.davis@unsw.edu.au This e-mail address is being protected from spambots. You need JavaScript enabled to view it bDepartment of Chemical Engineering, Izmir Institute of Technology, Gulbahce, I_zmir, 35430, Turkey cChildren’s Cancer Institute Australia (CCIA), Lowy Cancer Research Centre, The University of New South Wales, Sydney,NSW 2052, Australia 

  

Macromolecules (DOI: 10.1021/ma300521c)

Macromolecular Ligands for Gadolinium MRI Contrast Agents

Yang Li†, Mariana Beija†, Sophie Laurent‡, Luce vander Elst‡, Robert N Muller‡, Hien T T Duong†, Andrew B Lowe*§, Thomas P Davis*†, Cyrille Boyer*†§

 mamobx_2012_45_issue-9_largecover

Macromolecular ligands for gadolinium contrast agents (CAs) were prepared via a “grafting to” strategy. Copolymers of oligoethylene glycol methyl ether acrylate (OEGA) and an activated ester monomer, pentafluorophenyl acrylate (PFPA), were synthesized and modified with the 1-(5-amino-3-aza-2-oxypentyl)-4,7,10-tris(tert-butoxycarbonylmethyl)-1,4,7,10-tetraazacyclododecane (DO3A-tBu-NH2) chelate for the complexation of Gd3+. The relaxivity properties of the ligated Gd3+ agents were then studied to evaluate the effect of macromolecular architecture on their behavior as magnetic resonance imaging (MRI) CAs. Ligands made from linear and hyperbranched macromolecules showed a substantially increased relaxivity in comparison to existing commercial Gd3+ MRI contrast agents. In contrast, star nanogel polymers exhibited a slightly lower relaxivity per Gd3+ ion (but still substantially higher relaxivity than existing low molecular weight commercial CAs). This work shows that macromolecular ligands have the potential to serve as components of Gd MRI agents as there are enhanced effects on relaxivity, allowing for lower Gd concentrations to achieve contrast, while potentially imparting control over pharmacokinetics.

Australian Centre for Nanomedicine, School of Chemical Engineering, University of New South Wales Sydney NSW 2052 Australia NMR and Molecular Imaging Laboratory, Department of General, Organic and Biomedical Chemistry, University of Mons 7000 Mons Belgium §Centre for Advanced Macromolecular Design, School of Chemical Engineering, University of New South Wales Sydney NSW 2052 Australia
  

Macromolecular Rapid Communications (DOI: 10.1002/marc.201200029 Vol 33 Issue 8)

Synthesis of Functional Core, Star Polymers via RAFT Polymerization for Drug Delivery Applications

Jinna Liu, Hien Duong, Michael R Whittaker, Thomas P Davis*, Cyrille Boyer*-

Macromolecular Rapid Communications 

Poly(oligoethylene glycol) methyl ether acrylate was polymerized via reversible addition fragmentation transfer polymerization (RAFT), and then chain extended in the presence of both a cross-linker and vinyl benzaldehyde (VBA), yielding monodisperse star polymers. The presence of aldehyde groups in the core was exploited to attach doxorubicin. The drug loading was controlled by the amount of VBA incorporated (until 28 wt% in drug). The doxorubicin release was studied at pH = 5.5 and 7.4; conditions representative of endosomal and extra cellular environments. In vitro studies revealed that the doxorubicin-conjugated star polymers had a level of cytotoxicity comparable to that found for free doxorubicin. Confocal microscopy and flow cytometry studies confirmed efficient cell uptake of the star polymers.

Australian Centre for NanoMedicine,School of Chemical Engineering, University of New South Wales, Sydney NSW 2052 Australia

  

The Chemical Record (Vol 12 Issue 1, 2012 DOI 10.1002/tcr.201100013)

The Rise of Self-Assembled Monolayers for Fabricating Electrochemical Biosensors—An Interfacial Perspective.

1J Justin Gooding and Nadim Darwish

 The Chemical Record

Electrochemical biosensors have witnessed a tremendous growth in nanotechnology and in depth characterisation over the last two decades. In particular, modification of surfaces with self-assembled monolayers (SAMs) has provided a molecular control of the interfaces, which has paved the way to fabricate improved biosensing devices. Here we focus on the important advances of using SAMs in enzyme electrodes and affinity biosensors such as for peptides, DNA and antibodies.

1J Justin Gooding and Nadim Darwish, The School of Chemistry and the Australian Centre for Nanomedicine. University of New South Wales Sydney NSW 2052 Australia
  

ChemCom (DOI: 10.1039/c2cc30512g) February 2012

Ultrasensitive electrochemical detection of prostate-specific antigen (PSA) using gold-coated magnetic nanoparticles as ‘dispersible electrodes.

Kyloon Chuah,a Leo M H Lai,a Ian Y Goon,b Stephen G Parker,a Rose Amalb, J Justin Goodinga

 coverissue

Herein, we demonstrate the use of modified gold-coated magnetic nanoparticles as ‘dispersible electrodes’ which act as selective capture vehicles for electrochemical detection of prostate-specific antigen (PSA). A key advantage of this system is the ability to quantify non-electrochemical active analytes such as proteins with unprecedented detection limits and fast response times.

aSchool of Chemistry and The Australian Centre for NanoMdicine, University of New South Wales Sydney NSW 2052 AustraliaThis e-mail address is being protected from spambots. You need JavaScript enabled to view it ; bARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering, University of New South Wales Sydney NSW 2052 Australia

  

PLOSOne (doi:10.1371/journal.pone.0030734)

Evolution of Resistance to Aurora Kinase B Inhibitors in Leukaemia Cells

Timothy W Failes1, Gorjana Mitic1, Heba Abdel-Halim2, Sela T Po'uha1, Marjorie Liu1, David E Hibbs2, Maria Kavallaris1,3*

 

 one_web_icon_simple

Aurora kinase inhibitors are new mitosis-targeting drugs currently in clinical trials for the treatment of haematological and solid malignancies. However, knowledge of the molecular factors that influence sensitivity and resistance remains limited. Herein, we developed and characterised an in vitro leukaemia model of resistance to the Aurora B inhibitor ZM447439. Human T-cell acute lymphoblastic leukaemia cells, CCRF-CEM, were selected for resistance in 4 µM ZM447439. CEM/AKB4 cells showed no cross-resistance to tubulin-targeted and DNA-damaging agents, but were hypersensitive to an Aurora kinase A inhibitor. Sequencing revealed a mutation in the Aurora B kinase domain corresponding to a G160E amino acid substitution. Molecular modelling of drug binding in Aurora B containing this mutation suggested that resistance is mediated by the glutamate substitution preventing formation of an active drug-binding motif. Progression of resistance in the more highly selected CEM/AKB8 and CEM/AKB16 cells, derived sequentially from CEM/AKB4 in 8 and 16 µM ZM447439 respectively, was mediated by additional defects. These defects were independent of Aurora B and multi-drug resistance pathways and are associated with reduced apoptosis mostly likely due to reduced inhibition of the catalytic activity of aurora kinase B in the presence of drug. Our findings are important in the context of the use of these new targeted agents in treatment regimes against leukaemia and suggest resistance to therapy may arise through multiple independent mechanisms.

1Childrens Cancer Institute Australia, Lowy Cancer Research Centregh, University of New South Wales Randwick Australia 2 Faculty of Pharmacy, University of Sydney, Sydney Australia, 3 Australian Centre for NanoMedicine, University of New South Wales Sydney Australia

  

Analyst (137, 2012)

Development of an electrochemical immunosensor for the detection of HbA1c in serum.

†‡Guozhen Liu,a Sook Mei Khor,a Sridhar G Iyengarb, J Justin Gooding*a

 coverissue137

An electrochemical immuno-biosensor for detecting glycosylated haemoglobin (HbA1c) is reported based on glassy carbon (GC) electrodes with a mixed layer of an oligo(phenylethynylene) molecular wire (MW) and an oligo(ethylene glycol) (OEG). The mixed layer is formed from in situ-generated aryl diazonium cations. To the distal end of the MW, a redox probe 1,1'-di(aminomethyl)ferrocene (FDMA) was attached followed by the covalent attachment of an epitope N-glycosylated pentapeptide (GPP), an analogon to HbA1c, to which an anti-HbA1c monocolonal antibody IgG can selectively bind. HbA1c was detected by a competitive inhibition assay based on the competition for binding to anti-HbA1c IgG antibodies between the analyte in solution, HbA1c, and the surface bound epitope GPP. Exposure of the GPP modified sensing interface to the mixture of anti-HbA1c IgG antibody and HbA1c results in the attenuation of ferrocene electrochemistry due to free antibody binding to the interface. Higher concentrations of analyte led to higher Faradaic currents as less anti-HbA1c IgG is available to bind to the electrode surface. It was observed that there is a good linear relationship between the relative Faradaic current of FDMA and the concentration of HbA1c from 4.5% to 15.1% of total haemoglobin in serum without the need for washing or rinsing steps.

aSchool of Chemistry and The Australian Centre for NanoMedicine, University of New South Wales, Sydney NSW 2052 Australia bAgaMatrix, Inc 10 Manor Parkway Salem NH 03079 USA

  

Biomacromolecules (doi.org/10.1021/bm201199c)

Dicer-Labile PEG Conjugates for siRNA Delivery

Siew Ching Kow,1 Josh McCarroll,2,4 David Valade,3 Cyrille Boyer,2,3 Tanya Dwarte,4 Thomas P Davis,2,3 Maria Kavallaris,2,3  Volga Bulmus1,3,5

 bomaf6_2011_12_issue-12_cover

Poly(ethylene glycol) (PEG) conjugates of Dicer-substrate small interfering RNA (DsiRNA) have been prepared to investigate a new siRNA release strategy. 3'-sense or 5'-antisense thiol-modified, blunt-ended DsiRNAs, inhibiting enhanced green fluorescent protein (eGFP) expression, were covalently conjugated to PEG with varying molecular weights (2, 10, and 20 kg/mol) through a stable thioether bond using a Michael addition reaction. The DsiRNA conjugates with 2 kg/mol PEG (both 3'-sense or 5'-antisense strand conjugated) and the 10 kg/mol PEG conjugated to the 3'-sense strand of DsiRNA were efficiently cleaved by recombinant human Dicer to 21-mer siRNA, as determined by gel electrophoresis. Importantly, 2 and 10 kg/mol PEG conjugated to the 3'-sense strand of DsiRNA showed potent gene silencing activity in human neuroblastoma (SH-EP) cells, stably expressing eGFP, at both the mRNA and protein levels. Moreover, the 10 kg/mol PEG conjugates of the 3'-sense strand of DsiRNA were less immunogenic when compared with the unmodified DsiRNA, determined via an immune stimulation assay on human peripheral blood mononuclear cells.

1School of Biotechnology and Biomolecular Sciences, 2Australian Centre for Nanomedicine, School of Chemical Sciences & Engineering, and 3Centre for Advanced Macromolecular Design, School of Chemical Sciences & Engineering, University of New South Wales Sydney NSW 2052 Australia 4Children's Cancer Institute Australia, Lowy Cancer Research Centre, Randwick University of New South Wales Australia 5Department of Chemical Engineering, Biotechnology and Bioengineering Graduate Program, Izmir Institute of Technology, Urla Izmir 35430 Turkey

  

Molecular and Cellular Proteomics

Identification of Glycan Structure Alterations on Cell Membrane Proteins in Desoxyepothilone B Resistant Leukemia Cells

Miyako Nakano‡