• Bionic cartilage acellular matrix microspheres as scaffold for engineering cartilage

      Liu, Jun; Yu, Cheng; Lu, Gonggong; Tang, James Zhenggui; Wang, Yonghui; Zhang, Boqing; Sun, Yong; Lin, Hai; Wang, Qiguang; Liang, Jie; et al. (Royal Society of Chemistry, 2018-12-12)
      Extracellular matrix (ECM) scaffolds made from decellularized natural cartilage have been successfully used in cartilage lesion repair, but allogeneic cartilage donors are always in shortage and xenogeneic cartilage tissues may have the risk of unknown disease transfer. In this study, we constructed artificial bionic cartilage microspheres by encapsulating MSCs in collagen microspheres and cultured in a chondrogenic-inducing medium. Then, acellular matrix microsphere (BCAMM) scaffolds were fabricated from the cultured microspheres at three different developmental stages. A novel technique was introduced to fabricate BCAMM scaffolds, which enabled the production and utilization of the scaffolds in a short time. Due to the differences in surface morphologies and biological compositions, the three BCAMM scaffolds showed different chondrogenic effects. The 10-day BCAMM (10-BCAMM) scaffold showed the best overall results, successfully inducing MSC chondrogenesis without any additional fetal bovine serum or induction components (TGF-β or dexamethasone). In comparison, the 5-day BCAMM (5-BCAMM) scaffold showed potential osteogenic effects. The advantages of micron-sized BCAMMs are outlined, specifically in the easier decellularization process without grinding, homogeneous cell seeding and infiltration, chondrogenic induction and better fitting to the irregular lesion shape.
    • A cooperative water effect in proazaphosphatranecatalysed heterocycle synthesis

      Honey, Mark A.; Yamashita, Yasuhiro; Kobayashi, Shū (Royal Society of Chemistry, 2014-01-31)
      The synthesis of oxazolines and imidazolines was achieved by activation of isocyanides with water. Mechanistic studies show that the organosuperbase proazaphosphatrane is tolerant of water within the reaction medium, with a beneficial and cooperative effect being observed.
    • Effect of the Z- and Macro-R-Group on the thermal desulfurization of polymers synthesized with acid/base "switchable" dithiocarbamate RAFT agents

      Stace, Sarah J; Fellows, Christopher M; Moad, Graeme; Keddie, Daniel J (Royal Society of Chemistry, 2018-05-11)
      Thermolysis is examined as a method for complete desulfurization of reversible addition-fragmentation chain transfer (RAFT)-synthesized polymers prepared with acid/base "switchable" N-methyl-N-pyridyldithiocarbamates [RS2 CZ or RS2 CZH+ ]. Macro-RAFT agents from more activated monomers (MAMs) (i.e., styrene (St), N-isopropylacrylamide (NIPAm), and methyl methacrylate (MMA)) with RS2 CZH+ and less activated monomers (LAMs) (i.e., vinyl acetate (VAc) and N-vinylpyrolidone (NVP)) with RS2 CZ are prepared by RAFT polymerization and analyzed by thermogravimetric analysis. In all cases, a mass loss consistent with loss of the end group (ZCS2 H) is observed at temperatures lower than, and largely discrete from, that required for further degradation of the polymer. The temperatures for end group loss and the new end groups formed are strongly dependent on the identity of the R(P)n and the state of the pyridyl Z group; increasing in the series poly(MMA) < poly(St) ∼ poly(NIPAm) << poly(VAc) ∼ poly(NVP) for S2 CZ and poly(MMA) < poly(St) ∼ poly(NIPAm) for S2 CZH+ . Clean end group removal is possible for poly(St) and poly(NVP). For poly(NIPAm), the thiocarbonyl chain end is removed, but the end group identity is less certain. For poly(MMA) and poly(VAc), some degradation of the polymer accompanies end group loss under the conditions used and further refinement of the process is required.
    • Effects of synthetic iron and aluminium oxide surface charge and hydrophobicity on the formation of bacterial biofilm

      Pouran, Hamid M.; Banwart, Steve A.; Romero-Gonzalez, Maria; LMEI; School of Earth and Environment; Department of Geography (Royal Society of Chemistry, 2017-03-08)
      In this research, bacterial cell attachments to hematite, goethite and aluminium hydroxide were investigated. The aim was to study the effects of these minerals' hydrophobicity and pH-dependent surface charge on the extent of biofilm formation using six genetically diverse bacterial strains: Rhodococcus spp. (RC92 & RC291), Pseudomonas spp. (Pse1 & Pse2) and Sphingomonas spp. (Sph1 & Sph2), which had been previously isolated from contaminated environments. The surfaces were prepared in a way that was compatible with the naturally occurring coating process in aquifers: deposition of colloidal particles from the aqueous phase. The biofilms were evaluated using a novel, in situ and non-invasive technique developed for this purpose. A manufactured polystyrene 12-well plate was used as the reference surface to be coated with synthesized minerals by deposition of their suspended particles through evaporation. Planktonic phase growth indicates that it is independent of the surface charge and hydrophobicity of the studied surfaces. The hydrophobic similarities failed to predict biofilm proliferation. Two of the three hydrophilic strains formed extensive biofilms on the minerals. The third one, Sph2, showed anomalies in contrast to the expected electrostatic attraction between the minerals and the cell surface. Further research showed how the solution's ionic strength affects Sph2 surface potential and shapes the extent of its biofilm formation; reducing the ionic strength from ≈200 mM to ≈20 mM led to a tenfold increase in the number of cells attached to hematite. This study provides a technique to evaluate biofilm formation on metal-oxide surfaces, under well-controlled conditions, using a simple yet reliable method. The findings also highlight that cell numbers in the planktonic phase do not necessarily show the extent of cell attachment, and thorough physicochemical characterization of bacterial strains, substrata and the aquifer medium is fundamental to successfully implementing any bioremediation projects.
    • Efficient methane/nitrogen separation with low-sodium clinoptilolite.

      Guest, Jodie E.; Williams, Craig D. (Royal Society of Chemistry, 2002)
      The presence of sodium is shown to have a highly detrimental effect on the gas separation ability of clinoptilolite towards methane and nitrogen.
    • Functionalisation of MWCNTs with poly(lauryl acrylate) polymerised by Cu(0)-mediated and RAFT methods

      Gupta, Jaipal; Wan, Chaoying; Haddleton, David M.; McNally, Tony; Keddie, Daniel (Royal Society of Chemistry, 2016-05-12)
      Poly(lauryl acrylate) P[LA] of various molar masses were prepared via reversible addition–fragmentation chain transfer (RAFT) polymerisation and Cu(0)-mediated radical polymerisation, for the purpose of improving the dispersion and interfacial adhesion of MWCNTs with polymers such as isotactic poly(propylene) (iPP). Lauryl acrylate (LA) was polymerised via RAFT to high conversion (95%), furnished polymers in good agreement with theoretical Mn with dispersity increasing with increasing Mn. LA polymerised via the Cu(0)-mediated method to full conversion (>98%), gave polymers in good agreement with theoretical Mn and low dispersity (Đ ≈ 1.2) for lower molar mass polymers. Low molar mass tailing was also observed for P[LA] via Cu(0)-mediated polymerisation for higher molar mass polymers. Thermogravimetric analysis (TGA) of P[LA] via RAFT showed an onset of degradation occurred at ≈340–350 °C, however, this decreased to ≈250–260 °C for lower molar mass polymers. TGA of the RAFT agent revealed an onset of degradation of ≈200–250 °C. Free radicals generated from thermal degradation of end groups did not influence the thermal stability of the P[LA] backbone and ‘unzipping’ commonly seen with methacrylates was not observed. TGA analysis of P[LA] via the Cu(0)-mediated method revealed a similar degradation profile to that of P[LA] via RAFT. The thermal stability of P[LA] is sufficient to allow for melt processing with iPP. P[LA] via RAFT mixed with MWCNTs showed an adsorption of ≈10–25 wt% P[LA] on to the MWCNTs. The onset of thermal degradation of the P[LA] remained unchanged after adsorption on to the MWCNTs. P[LA] via the Cu(0)-mediated method adsorbed up to 85 wt% and an increase in thermal stability of ≈50 °C was recorded. Increasing P[LA] and MWCNT concentration independently also resulted in an increase in the level of adsorption, possibility due to increased CH–π interaction. The difference in thermal stability could possibly be due to heat transfer from the P[LA] to the MWCNTs, resulting in delayed pyrolysis of P[LA]. Size exclusion chromatography (SEC) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) of P[LA] after heating to 200 °C for 30 min in air showed loss of end groups but, the P[LA] backbone remained preserved for both polymer types. Evidence from transmission electron micrographs (TEM) shows the P[LA] adsorbing onto the MWCNT surface. Melt processing composites of P[LA] via Cu(0)-mediated with MWCNTs and iPP was possible as the P[LA] was thermally stable during the both extrusion and in the TGA when studied post melt mixing.
    • Hybrid QSPR models for the prediction of the free energy of solvation of organic solute/solvent pairs

      Borhani, Tohid N; García-Muñoz, Salvador; Vanesa Luciani, Carla; Galindo, Amparo; Adjiman, Claire S (Royal Society of Chemistry, 2019-06-17)
      Due to the importance of the Gibbs free energy of solvation in understanding many physicochemical phenomena, including lipophilicity, phase equilibria and liquid-phase reaction equilibrium and kinetics, there is a need for predictive models that can be applied across large sets of solvents and solutes. In this paper, we propose two quantitative structure property relationships (QSPRs) to predict the Gibbs free energy of solvation, developed using partial least squares (PLS) and multivariate linear regression (MLR) methods for 295 solutes in 210 solvents with total number of data points of 1777. Unlike other QSPR models, the proposed models are not restricted to a specific solvent or solute. Furthermore, while most QSPR models include either experimental or quantum mechanical descriptors, the proposed models combine both, using experimental descriptors to represent the solvent and quantum mechanical descriptors to represent the solute. Up to twelve experimental descriptors and nine quantum mechanical descriptors are considered in the proposed models. Extensive internal and external validation is undertaken to assess model accuracy in predicting the Gibbs free energy of solvation for a large number of solute/solvent pairs. The best MLR model, which includes three solute descriptors and two solvent properties, yields a coefficient of determination (R2) of 0.88 and a root mean squared error (RMSE) of 0.59 kcal mol−1 for the training set. The best PLS model includes six latent variables, and has an R2 value of 0.91 and a RMSE of 0.52 kcal mol−1. The proposed models are compared to selected results based on continuum solvation quantum chemistry calculations. They enable the fast prediction of the Gibbs free energy of solvation of a wide range of solutes in different solvents.
    • Influence of the tetraalkoxysilane crosslinker on the properties of polysiloxane-based elastomers prepared by the Lewis acid-catalysed Piers-Rubinsztajn reaction

      Hickman, Andrew M.; Chmel, Nikola; Cameron, Neil R.; Keddie, Daniel J.; Schiller, Tara L. (Royal Society of Chemistry, 2021-07-21)
      We investigate the preparation of polysiloxane-based networks under solvent-free, ambient conditions using the Lewis acid catalysed Piers-Rubinsztajn (PR) reaction of hydride-terminated siloxanes with various tetrafunctional alkoxysilanes (tetraethoxysilane, tetrapropoxysilane, tetra-n-buxoxysilane, tetra-s-butoxysilane, tetra-s-butoxysilane, and tetrakis(2- ethylbutoxy)silane) as crosslinkers. We explore the effects of polysiloxane chain length and crosslinker alkyl group on the rheological performance of the elastomers. By analysing the reaction progress by grazing angle Fourier-transform infrared spectroscopy (FTIR) and determining the rheological properties of the resulting materials, we show that the use of linear or branched alkoxysilanes strongly influences the morphology and properties of these network polymers. We have shown the PR process is can be tailored to reliably produce homogeneous, polysiloxane network materials. This work provides information on the relative rates of network formation under ambient conditions with an emphasis on the impact of crosslinker alkyl chain length. Our results show that electronics and s terics both play critical roles in influencing the the rate of the curing reaction. Crucially, we newly demonstrate the benefit of a having tertiary carbon α to the SiO reaction centre, as is the case for the tetra-s-butoxysilane crosslinker, for delivering exceptionally rapid network cure and a concomitant enhancement in storage modulus of the resultant materials.
    • Slight ligand modifications within multitopic linear hydroxamates promotes connectivity differences in Cu(II) 1-D coordination polymers

      Mohammed, Baba Fugu; Coley, Joe; Dickinson, Isabella F.; Orton, James B.; Klooster, Wim; Gleeson, M. Paul; Jones, Leigh F. (Royal Society of Chemistry, 2021-07-23)
      The novel multitopic ligands N-hydroxy-4-((2-hydroxy-3-methoxybenzyl)amino)benzamide (L3H3) and N-hydroxy-4-((2- hydroxybenzyl)amino)benzamide (L4H3) have been synthesised through the Schiff base coupling and subsequent reduction of 4-aminophenylhydroxamic acid and either o-vanillin (to give L3H3) or 2-hydroxybenzaldehyde (to give L4H3). These linear multitopic ligands bind Cu(II) centres at both the hydroxamate and phenol ends to form the 1-D coordination polymers [Cu(II)(L3H2)2]n (1) and {[Cu(II)(L4H2)2].2MeOH}n (2). Slight differences in the structures of L3H3 and L4H3 lead to significant extended connectivity changes upon Cu(II) metalation that are exampled by a 27% decrease in intra-chain Cu(II)…Cu(II) distance upon moving from 1 to 2. The significant conformation and metal binding differences shown by L3H2 and L4H2 in 1 and 2 respectively have been rationalised using density functional theory (DFT) calculations. Hirschfeld surface analysis has been employed to assess and visualise the intra- and intermolecular interactions in both complexes.
    • Synthesis of high silicon content SAPO(4)-5 using anionic surfactants in a hexanol/aqueous two phase media.

      Han, Xue S.; Williams, Craig D.; Lee, Darren F.; Round, Catherine I. (Royal Society of Chemistry, 2002)
      High silicon content SAPO(4)-5 (up to 0.511 atoms per unit cell) has been synthesised, using sodium 3-bromopropanesulfonate, sodium 1-butanesulfonate, sodium naphthalene-1-sulfonate or sodium n-decyl sulfate as surfactants; the SiO2 in the reaction gels ranged up to 3.0 (molar ratio), silicon incorporation was confirmed by XRD, XRF, TG-DTA, FT-IR and SEM techniques.
    • The cytotoxic mechanisms of disulfiram and copper(ii) in cancer cells

      Tawari, Patricia Erebi; Wang, Zhipeng; Najlah, Mohammad; Tsang, Chi Wai; Kannappan, Vinodh; Liu, Peng; McConville, Christopher; He, Bin; Armesilla, Angel L.; Wang, Weiguang; et al. (Royal Society of Chemistry, 2015-09-10)
      The anticancer activity of disulfiram (DS) is copper(II) (Cu)-dependent. This study investigated the anticancer mechanisms of DS/Cu using in vitro cytotoxicity and metabolic kinetic analysis. Our study indicates that DS/Cu targets cancer cells by the combination of two types of actions: (1) instant killing executed by DS/Cu reaction generated reactive oxygen species; (2) delayed cytotoxicity introduced by the end product, DDC-Cu. Nanoencapsulation of DS might shed light on repositioning of DS into cancer treatment