AFM study of morphology and mechanical properties of a chimeric 2 spider silk and bone sialoprotein protein for bone regeneration

Atomic force microscopy (AFM) was used to assess a new chimeric protein consisting of a fusion protein of the consensus repeat for Nephila clavipes spider dragline protein and bone sialoprotein (6merþBSP). The elastic modulus of this protein in film form was assessed through force curves, and film surface roughness was also determined. The results showed a significant difference among the elastic modulus of the chimeric silk protein, 6merþBSP, and control films consisting of only the silk component (6mer). The behavior of the 6merþBSP and 6mer proteins in aqueous solution in the presence of calcium (Ca) ions was also assessed to determine interactions between the inorganic and organic components related to bone interactions, anchoring, and biomaterial network formation. The results demonstrated the formation of protein networks in the presence of Ca2þ ions, characteristics that may be important in the context of controlling materials assembly and properties related to bone formation with this new chimeric silk-BSP protein.Silvia Games thanks the Foundation for Science and Technology (FCT) for supporting her Ph.D. grant, SFRH/BD/28603/2006. This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283), the Chimera project (PTDC/EBB-EBI/109093/2008) funded by the FCT agency, the NIH (P41 EB002520) Tissue Engineering Resource Center, and the NIH (EB003210 and DE017207)

Influence of Membrane Characteristics on Flux Decline and Retention in Nanofiltration (Invloed van membraaneigenschappen op vervuiling en retentie in nanofiltratie)

To study thorougly the flux decline in nanofiltration, a study of the influence of the membrane properties is necessary. Important properties are: the structure and the free volume of the polymer, the surface roughness and the surface charge. In this research, both comercial and self-made membranes will be used.Table of contents Abstract Nederlandstalige samenvatting 1 Membrane technology 1.1 Introduction 1.2 Pressure-driven membrane processes and nanofiltration 1.3 Principles and definitions 1.4 Flux decline and fouling 1.4.1 Mechanisms of flux decline 1.4.2 Fouling 1.5 Aim of this work and research approach 2 Methods and materials 2.1 Nanofiltration experiments 2.1.1 Filtration equipment 2.1.2 Selection of commercial membranes 2.2 Adsorption experiments 2.3 Synthesis of polyethersulfone membranes 2.4 Membrane characterization techniques 2.4.1 Atomic Force Microscopy 2.4.2 Contact angle measurements 2.4.3 Determination of cut-off 2.4.4 Measurements of the streaming potential 2.4.5 Positron Annihilation Spectroscopy 2.4.6 Attenuated Total Reflectance-Fourier Transform InfraRed 2.4.7 X-ray Photoelectron Spectroscopy 2.4.8 Scanning Electron Microscopy 2.4.9 Differential Scanning Calorimetry 2.4.10 Pre-treatment of membrane samples 2.5 Selection of feed components 2.5.1 Selection of organic components (uncharged and charged) 2.5.2 Selection and characterization of colloids 2.6 Chemical analysis of aqueous solutions 2.6.1 UV-VIS spectrophotometry 2.6.2 High Performance Liquid Chromatography 2.6.3 Determination of suspended and settleable solids, COD and BOD 2.7 Statistical methods: multiple linear regression 2.7.1 Principle of multiple linear regression 2.7.2 Selection of independent x variables 2.7.3 Diagnostics of the regression method 2.7.4 Experimental conditions 3 Synthesis of polyethersulfone membranes 3.1 Introduction 3.2 Preparation of membranes without support layer 3.2.1 Influence of the polymer concentration 3.2.2 Influence of the relative air humidity 3.2.3 Influence of additives to the polymer solution 3.2.4 Influence of additives to the non-solvent bath and the bath temperature 3.2.5 Influence of the solvent 3.2.6 Conclusion 3.3 Preparation of membranes on a support layer 3.3.1 Influence of the polymer concentration 3.3.2 Characterization of the membranes 3.3.3 Testing of the performance of the membranes 3.4 Conclusion 4 Physico-chemical characterization of nanofiltration membranes 4.1 Introduction 4.2 Chemical characterization of nanofiltration membranes 4.2.1 ATR-FTIR Spectroscopy 4.2.2 X-ray Photoelectron Spectroscopy 4.2.3 Conclusion 4.3 Physical characterization of nanofiltration membranes 4.3.1 Determination of the cut-off 4.3.2 Determination of the surface roughness 4.3.3 Determination of the surface hydrophobicity 4.3.4 Determination of the surface charge 4.3.5 Conclusion 4.4 Positron Annihilation Spectroscopy 4.4.1 S parameter 4.4.2 R parameter 4.4.3 Positron Annihilation Lifetime Spectroscopy 4.4.4 Comparison between cut-off and pore sizes obtained by PALS 4.5 Conclusion 5 Relation between characteristics and performance of nanofiltration membranes 5.1 Introduction 5.2 Nanofiltration performance during filtration of aqueous solutions containing dissolved organic components 5.2.1 Filtration of aqueous solutions containing dissolved uncharged organic components 5.2.2 Filtration of aqueous solutions containing dissolved charged organic components 5.3 Nanofiltration performance during filtration of colloidal dispersions 5.3.1 Introduction 5.3.2 Characterization of colloids 5.3.3 Influence of membrane characteristics on colloidal fouling 5.3.4 Influence of colloid characteristics on colloidal fouling 5.3.5 Influence of solution chemistry on colloidal fouling 5.3.6 Conclusion for colloidal dispersions 5.4 General conclusion 6 Regeneration of carwash wastewater by nanofiltration 6.1 Introduction 6.2 Surfactant fouling of nanofiltration membranes 6.2.1 Introduction 6.2.2 Effect of the type of surfactant 6.2.3 Effect of the surfactant concentration 6.2.4 Effect of the addition of salt 6.2.5 Effect of pH of the surfactant solution 6.2.6 Effect of a mixture of surfactants 6.2.7 Conclusion 6.3 Applicability of nanofiltration in the carwash industry 6.3.1 Description of the selected carwash 6.3.2 Analysis of the wastewaters 6.3.3 Filtration experiments of the different wastewaters 6.3.4 Cleaning procedure 6.4 Conclusion Summary and general conclusions References Appendix I: Chemical structure of uncharged organic components Appendix II: Chemical structure of charged organic components List of publications Curriculum vitaestatus: publishe

Investigation of nanopores in nanofiltration membranes using slow positron beam techniques

The pore distribution of the commercial nanofiltration membranes Desal 5DL, Desal 51HL, N30F, NTR 7450 and NF-PES-10 were analyzed by positron annihilation spectroscopy using slow positron beam analysis. From the depth selective 3 gamma/2 gamma analysis a dense nanoporous filtration layer could be determined. From the depth selective lifetime analysis the size and distribution of the nanopores could be extracted. The measurements indicate the presence of 2 pore sizes in the samples with a radius of 1.25-1.55 angstrom and 3.2-3.95 angstrom. These experimental values are compared with the molecular weight cut-off values of these membranes