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ABSTRACT: The increasing use of drug combinations to treat disease states, such as cancer, calls for improved delivery systems that are able to deliver multiple agents. Herein, we report a series of novel Janus dendrimers with potential for use in combination therapy. Different generations (first and second) of PEG-based dendrons containing two different 'model drugs', benzyl alcohol (BA) and 3-phenylpropionic acid (PPA) were synthesised. BA and PPA were attached via two different linkers (carbonate and ester, respectively) to promote differential drug release. The four dendrons were then coupled together via (3+2) cycloaddition chemistries to afford four Janus dendrimers, which contained varying amounts and different ratios of BA and PPA, namely: (BA)2-G1-G1-(PPA)2, (BA)4-G2-G1-(PPA)2, (BA)2-G1-G2-(PPA)4, (BA)4-G2-G2-(PPA)4. Release studies in plasma showed that the dendrimers provided sequential release of the two model drugs, with BA being released faster than PPA from all of the dendrons. The different dendrimers allowed delivery of increasing amounts (0.15-.0.30 mM) and in exact molecular ratios (1:2; 2:1; 1:2; 2:2) of the two model drug compounds. The dendrimers were non-cytotoxic (100 % viability at 1 mg/mL) towards human umbilical vein endothelial cells (HUVEC) and non-toxic towards red blood cells as confirmed by haemolysis studies. These studies demonstrate that these Janus PEG-based dendrimers offer great potential for the delivery of drugs via combination therapy.
Biomacromolecules 01/2013; · 5.48 Impact Factor
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ABSTRACT: Insulin-degrading enzyme (IDE) is a neutral Zn(2+) peptidase that degrades short peptides based on substrate conformation, size and charge. Some of these substrates, including amyloid β (Aβ) are capable of self-assembling into cytotoxic oligomers. Based on IDE recognition mechanism and our previous report of the formation of a stable complex between IDE and intact Aβ in vitro and in vivo, we analyzed the possibility of a chaperone-like function of IDE. A proteolytically inactive recombinant IDE with Glu111 replaced by Gln (IDEQ) was used. IDEQ blocked the amyloidogenic pathway of Aβ yielding non-fibrillar structures as assessed by electron microscopy. Measurements of the kinetics of Aβ aggregation by light scattering showed that 1) IDEQ effect was promoted by ATP independent of its hydrolysis, 2) end products of Aβ-IDEQ co-incubation were incapable of "seeding" the assembly of monomeric Aβ and 3) IDEQ was ineffective in reversing Aβ aggregation. Moreover, Aβ aggregates formed in the presence of IDEQ were non-neurotoxic. IDEQ had no conformational effects upon insulin (a non-amyloidogenic protein under physiological conditions) and did not disturb insulin receptor activation in cultured cells. Our results suggest that IDE has a chaperone-like activity upon amyloid-forming peptides. It remains to be explored whether other highly conserved metallopeptidases have a dual protease-chaperone function to prevent the formation of toxic peptide oligomers from bacteria to mammals.
PLoS ONE 01/2013; 8(4):e59113. · 4.09 Impact Factor
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ABSTRACT: A chiral bisurea-based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mM is reported. This soft material has been characterized by thermal studies, rheology, X-ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy-driven self-assembly process. These particular thermal characteristics make these materials easy to handle for soft-application technologies.
Chemistry 09/2012; · 5.93 Impact Factor
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ABSTRACT: A novel combination of site-specific isotope labelling, polarised infrared spectroscopy and molecular combing reveals local orientational ordering in the fibril-forming peptide YTIAALLSPYSGGRADS. Use of (13)C-(18)O labelled alanine residues demonstrates that the N-terminal end of the peptide is incorporated into the cross-beta structure, while the C-terminal end shows orientational disorder.
Chemical Communications 09/2012; · 6.17 Impact Factor
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ABSTRACT: We report on the formation of hydrogel monoliths formed by functionalized peptide Fmoc-RGD (Fmoc: fluorenylmethoxycarbonyl) containing the RGD cell adhesion tripeptide motif. The monolith is stable in water for nearly 40 days. The gel monoliths present a rigid porous structure consisting of a network of peptide fibers. The RGD-decorated peptide fibers have a β-sheet secondary structure. We prove that Fmoc-RGD monoliths can be used to release and encapsulate material, including model hydrophilic dyes and drug compounds. We provide the first insight into the correlation between the absorption and release kinetics of this new material and show that both processes take place over similar time scales.
Langmuir 08/2012; 28(34):12575-80. · 4.19 Impact Factor
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ABSTRACT: The self-assembly of the peptide amphiphile (PA) hexadecyl-(β-alanine-histidine) is examined in aqueous solution, along with its mixtures with multilamellar vesicles formed by DPPC (dipalmitoyl phosphatidylcholine). This PA, denoted C(16)-βAH, contains a dipeptide headgroup corresponding to the bioactive molecule L-carnosine. It is found to self-assemble into nanotapes based on stacked layers of molecules. Bilayers are found to coexist with monolayers in which the PA molecules pack with alternating up-down arrangement so that the headgroups decorate both surfaces. The bilayers become dehydrated as PA concentration increases and the number of layers in the stack decreases to produce ultrathin nanotapes comprised of 2-3 bilayers. Addition of the PA to DPPC multilamellar vesicles leads to a transition to well-defined unilamellar vesicles. The unique ability to modulate the stacking of this PA as a function of concentration, combined with its ability to induce a multilamellar to unilamellar thinning of DPPC vesicles, may be useful in biomaterials applications where the presentation of the peptide function at the surface of self-assembled nanostructures is crucial.
Langmuir 07/2012; 28(31):11599-608. · 4.19 Impact Factor
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ABSTRACT: A strategy is presented that exploits the ability of synthetic polymers of different nature to disturb the strong self-assembly capabilities of amyloid based β-sheet forming peptides. Following a convergent approach, the peptides of interest were synthesized via solid-phase peptide synthesis (SPPS) and the polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by a copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) to generate the desired peptide-polymer conjugates. This study focuses on a modified version of the core sequence of the β-amyloid peptide (Aβ), Aβ(16-20) (KLVFF). The influence of attaching short poly(N-isopropylacrylamide) and poly(hydroxyethylacrylate) to the peptide sequences on the self-assembly properties of the hybrid materials were studied via infrared spectroscopy, TEM, circular dichroism and SAXS. The findings indicate that attaching these polymers disturbs the strong self-assembly properties of the biomolecules to a certain degree and permits to influence the aggregation of the peptides based on their β-sheets forming abilities. This study presents an innovative route toward targeted and controlled assembly of amyloid-like fibers to drive the formation of polymeric nanomaterials.
Biomacromolecules 07/2012; 13(9):2739-47. · 5.48 Impact Factor
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ABSTRACT: We report the investigation of the mechanical properties of different types of amyloid fibrils by the peak force quantitative nanomechanical (PF-QNM) technique. We demonstrate that this technique correctly measures the Young's modulus independent of the polymorphic state and the cross-sectional structural details of the fibrils, and we show that values for amyloid fibrils assembled from heptapeptides, α-synuclein, Aβ(1-42), insulin, β-lactoglobulin, lysozyme, ovalbumin, Tau protein and bovine serum albumin all fall in the range of 2-4 GPa.
Nanoscale 06/2012; 4(15):4426-9. · 5.91 Impact Factor
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ABSTRACT: Ring-closing olefin metathesis reactions are used to create intra-molecularly ring closed peptides or inter-molecularly ring-closed peptide dimers based on a designed amyloid peptide sequence. The uncrosslinked peptide self-assembles into high aspect ratio nanotubes, however ring-closing leads to the formation of fibrillar and twisted/helical ribbon structures.
Chemical Communications 04/2012; 48(31):3757-9. · 6.17 Impact Factor
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ABSTRACT: A focused library of potential hydrogelators each containing two substituted aromatic residues separated by a urea or thiourea linkage have been synthesised and characterized. Six of these novel compounds are highly efficient hydrogelators, forming gels in aqueous solution at low concentrations (0.03-0.60 wt%). Gels were formed through a pH switching methodology, by acidification of a basic solution (pH 14 to ≈ 4) either by addition of HCl or via the slow hydrolysis of glucono-δ-lactone. Frequently, gelation was accompanied by a dramatic switch in the absorption spectra of the gelators, resulting in a significant change in colour, typically from a vibrant orange to pale yellow. Each of the gels was capable of sequestering significant quantities of the aromatic cationic dye, methylene blue, from aqueous solution (up to 1.02 g of dye per gram of dry gelator). Cryo-transmission electron microscopy of two of the gels revealed an extensive network of high aspect ratio fibers. The structure of the fibers altered dramatically upon addition of 20 wt% of the dye, resulting in aggregation and significant shortening of the fibrils. This study demonstrates the feasibility for these novel gels finding application as inexpensive and effective water purification platforms.
Chemistry 02/2012; 18(9):2692-9. · 5.93 Impact Factor
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ABSTRACT: A series of heptapeptides comprising the core sequence Aβ(16-20), KLVFF, of the amyloid β peptide coupled with paired N-terminal γ-amino acids are investigated in terms of cytotoxicity reduction and binding to the full Aβ peptide, both pointing to inhibition of fibrillisation for selected compounds. This is related to the self-assembly capacity of the heptapeptides.
Chemical Communications 12/2011; 47(46):12470-2. · 6.17 Impact Factor
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Nágila M P S Ricardo,
Nadja M P S Ricardo,
Flávia de M L L Costa,
Francisco W A Bezerra,
Chiraphon Chaibundit,
Daniel Hermida-Merino,
Barnaby W Greenland,
Stefano Burattini, Ian W Hamley,
S Keith Nixon,
Stephen G Yeates
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ABSTRACT: The micellization of F127 (E(98)P(67)E(98)) in dilute aqueous solutions of polyethylene glycol (PEG6000 and PEG35000) and poly(vinylpyrrolidone) (PVP K30 and PVP K90) is studied. The average hydrodynamic radius (r(h,app)) obtained from the dynamic light scattering technique increased with increase in PEG concentration but decreased on addition of PVP, results which are consistent with interaction of the micelles with PEG and the formation of micelles clusters, but no such interaction occurs with PVP. Tube inversion was used to determine the onset of gelation. The critical concentration of F127 for gelation increased on addition of PEG and of PVP K30 but decreased on addition of PVP K90. Small-angle X-ray scattering (SAXS) was used to show that the 30 wt% F127 gel structure (fcc) was independent of polymer type and concentration, as was the d-spacing and so the micelle hard-sphere radius. The maximum elastic modulus (G(max)(')) of 30 wt% F127 decreased from its value for water alone as PEG was added, but was little changed by adding PVP. These results are consistent with the packed-micelles in the 30 wt% F127 gel being effectively isolated from the polymer solution on the microscale while, especially for the PEG, being mixed on the macroscale.
Journal of Colloid and Interface Science 11/2011; 368(1):336-41. · 3.07 Impact Factor
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ABSTRACT: The aim of this study was to construct an artificial fetal membrane (FM) by combination of human amniotic epithelial stem cells (hAESCs) and a mechanically enhanced collagen scaffold containing encapsulated human amniotic stromal fibroblasts (hASFs). Such a tissue-engineered FM may have the potential to plug structural defects in the amniotic sac after antenatal interventions, or to prevent preterm premature rupture of the FM. The hAESCs and hASFs were isolated from human fetal amniotic membrane (AM). Magnetic cell sorting was used to enrich the hAESCs by positive ATP-binding cassette G2 selection. We investigated the use of a laminin/fibronectin (1:1)-coated compressed collagen gel as a novel scaffold to support the growth of hAESCs. A type I collagen gel was dehydrated to form a material mimicking the mechanical properties and ultra-structure of human AM. hAESCs successfully adhered to and formed a monolayer upon the biomimetic collagen scaffold. The resulting artificial membrane shared a high degree of similarity in cell morphology, protein expression profiles, and structure to normal fetal AM. This study provides the first line of evidence that a compacted collagen gel containing hASFs could adequately support hAESCs adhesion and differentiation to a degree that is comparable to the normal human fetal AM in terms of structure and maintenance of cell phenotype.
Tissue Engineering Part A 09/2011; 18(3-4):373-81. · 4.64 Impact Factor
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Journal of Polymer Science Part B Polymer Physics 08/2011; 49(19):1397 - 1409. · 1.53 Impact Factor
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Angewandte Chemie International Edition 06/2011; 50(24):5495-8. · 13.45 Impact Factor
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ABSTRACT: The self-assembly in aqueous solution of PEG (1500 Da) telechelically end-capped with hydrophobic dipeptides has been investigated using spectroscopic, microscopic, scattering, and rheological methods. A self-assembled β-sheet fibril-based hydrogel has been identified (containing dityrosine end groups), which exhibits a gel-sol transition near body temperature. This thermo-responsive PEG-based biofunctional hydrogel is expected to have diverse potential uses in delivery or diagnostics for biomedical applications.
Macromolecular Bioscience 05/2011; 11(8):1068-78. · 3.89 Impact Factor
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ABSTRACT: We report the use of molecular combing as an alignment method to obtain macroscopically oriented amyloid fibrils on planar surfaces. The aligned fibrils are studied by polarized infrared spectroscopy. This gives structural information that cannot be definitively obtained from standard infrared experiments on isotropic samples, for example, confirmation of the characteristic cross-β amyloid core structure, the side-chain orientation from specific amino acids, and the arrangement of the strands within the fibrils, as we demonstrate here. We employed amyloid fibrils from hen egg white lysozyme (HEWL) and from a model octapeptide. Our results demonstrate molecular combing as a straightforward method to align amyloid fibrils, producing highly anisotropic infrared linear dichroism (IRLD) spectra.
Biomacromolecules 03/2011; 12(5):1810-21. · 5.48 Impact Factor
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ABSTRACT: The influence of charge and aromatic stacking interactions on the self-assembly of a series of four model amyloid peptides has been examined. The four model peptides are based on the KLVFF motif from the amyloid β peptide, Aβ(16−20) extended at the N terminus with two β-alanine residues. We have studied NH2-βAβAKLVFF-COOH (FF), NH2-βAβAKLVF-COOH (F), CH3CONH-βAβAKLVFF-CONH2 (CapF), and CH3CONH-βAβAKLVFF-CONH2 (CapFF). The former two are uncapped (net charge +2) and differ by one hydrophobic phenylalanine residue; the latter two are the analogous capped peptides (net charge +1). The self-assembly characteristics of these peptides are remarkably different and strongly dependent on concentration. NMR shows a shift from carboxylate to carboxylic acid forms upon increasing concentration. Saturation transfer measurements of solvent molecules indicate selective involvement of phenylalanine residues in driving the self-assembly process of CapFF due presumably to the effect of aromatic stacking interactions. FTIR spectroscopy reveals β-sheet features for the two peptides containing two phenylalanine residues but not the single phenylalanine residue, pointing again to the driving force for self-assembly. Circular dichroism (CD) in dilute solution reveals the polyproline II conformation, except for F which is disordered. We discuss the relationship of this observation to the significant pH shift observed for this peptide when compared the calculated value. Atomic force microscopy and cryogenic-TEM reveals the formation of twisted fibrils for CapFF, as previously also observed for FF. The influence of salt on the self-assembly of the model β-sheet forming capped peptide CapFF was investigated by FTIR. Cryo-TEM reveals that the extent of twisting decreases with increased salt concentration, leading to the formation of flat ribbon structures. These results highlight the important role of aggregation-induced pKa shifts in the self-assembly of model β-sheet peptides.
02/2011;
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ABSTRACT: The influence of charge and aromatic stacking interactions on the self-assembly of a series of four model amyloid peptides has been examined. The four model peptides are based on the KLVFF motif from the amyloid β peptide, Aβ(16-20) extended at the N terminus with two β-alanine residues. We have studied NH(2)-βAβAKLVFF-COOH (FF), NH(2)-βAβAKLVF-COOH (F), CH(3)CONH-βAβAKLVFF-CONH(2) (CapF), and CH(3)CONH-βAβAKLVFF-CONH(2) (CapFF). The former two are uncapped (net charge +2) and differ by one hydrophobic phenylalanine residue; the latter two are the analogous capped peptides (net charge +1). The self-assembly characteristics of these peptides are remarkably different and strongly dependent on concentration. NMR shows a shift from carboxylate to carboxylic acid forms upon increasing concentration. Saturation transfer measurements of solvent molecules indicate selective involvement of phenylalanine residues in driving the self-assembly process of CapFF due presumably to the effect of aromatic stacking interactions. FTIR spectroscopy reveals β-sheet features for the two peptides containing two phenylalanine residues but not the single phenylalanine residue, pointing again to the driving force for self-assembly. Circular dichroism (CD) in dilute solution reveals the polyproline II conformation, except for F which is disordered. We discuss the relationship of this observation to the significant pH shift observed for this peptide when compared the calculated value. Atomic force microscopy and cryogenic-TEM reveals the formation of twisted fibrils for CapFF, as previously also observed for FF. The influence of salt on the self-assembly of the model β-sheet forming capped peptide CapFF was investigated by FTIR. Cryo-TEM reveals that the extent of twisting decreases with increased salt concentration, leading to the formation of flat ribbon structures. These results highlight the important role of aggregation-induced pK(a) shifts in the self-assembly of model β-sheet peptides.
The Journal of Physical Chemistry B 02/2011; 115(9):2107-16. · 3.70 Impact Factor
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ABSTRACT: A structurally simple low molecular weight hydrogelator derived from isophthalic acid forms robust pH-responsive hydrogels capable of highly efficient and selective dye adsorption.
Chemical Communications 11/2010; 46(42):7960-2. · 6.17 Impact Factor
