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Preface ix 1 Polyurethane Chemistry 1 Introduction 1 The Chemistry 2 The Isocyanates 3 The Polyol 5 Cross–Linking 5 The Water Reaction 6 Process 8 The One–Shot Process 8 The Prepolymer Process 10 Post Processing 12 Architecture of Polyurethane Foam 14 Grafting to the Polyurethane Foam 16 Biodegradable PUR 19 Mechanism of Biodegradation 23 More Examples 24 Conclusion 25 References 26 2 Laboratory Practice 29 Introduction 29 Prepolymers 30 Preparation of an Elastomer 30 Preparation of Foam 32 Hydrophobic Foams 32 Hydrophilic Foams 34 Custom Prepolymers, Foams, and Scaffolds 40 Examples 43 Structure–Property Relationships 48 The Special Case of Hydrophilic Polyurethane Foams 50 Physical and Chemical Testing 50 Physical Testing 52 Biocompatibility Testing 54 Process Equipment 54 Metering Pump 55 Mixing Head 55 Tank/Material Retaining Container 55 Machine Manufacturers 56 References 56 3 Scaffolds 59 Introduction 59 Bioscaffolds 61 Examples of Biofilter 65 Elimination of Tobacco Odor from a Cigarette–Manufacturing Plant 67 Treatment of VOCs from an Industrial Plant 68 The Liver as Biofilter 68 Scaffolds for Medical Applications (In Vivo and Extracorporeal) 70 The Liver Model 71 The Extracellular Matrix as Scaffold 72 The Physical Scaffold 73 Design of an Ideal Scaffold 74 Drug Discovery 75 Materials of Construction 77 Ceramics 77 Metals 80 Polymer Scaffolds 82 Poly(lactic Acid) 82 Poly(glycolic Acid) 82 Polycaprolactone 83 Polyurethanes 83 The “Ideal” Scaffold 87 Pore Size and Distribution 89 Void Volume 91 Interconnectedness 96 Surface Area 98 Mechanical Properties 100 Surface Chemistry 100 Specifications of the Ideal Scaffold 101 References 105 4 Immobilization 109 Introduction 109 Methods of Immobilization 111 Immobilization by Adsorption 113 Biofiltration 113 Biotrickling Filter Setup and Operating Conditions 115 The Toluene Reactor 116 The H2S Reactor 120 Biological Treatment of Aquarium Tanks 123 Protein Adsorption 125 The Avidin–Biotin System 126 Application of the Avidin–Biotin System to Cell Adhesion to a Scaffold 128 Adsorption to a Tricalcium Phosphate (TCP) Scaffold Using the Avidin–Biotin System 128 Hepatic Cells on a Fabricated Polycaprolactone Scaffold 131 Summary of Immobilization by Adsorption 132 Immobilization by Extraction 133 Extraction of Pesticides 138 Summary 144 Immobilization by Entrapment 145 Alginate Encapsulation 146 Encapsulation of Pancreatic Islet Cells 148 Encapsulation of Osteoblasts 148 Introduction to the Pancreas Model 149 The Pancreas Model 150 Summary of Encapsulation 154 Immobilization by Covalent Bonding 154 Overview of Covalent Immobilization 156 Substrates Used for Immobilization 157 Alginates 158 Albumin 159 Collagen 159 Synthetic Polymers as Supports 159 Polyethylene 159 Poly l–Lactic Acid 160 Immobilization to Polyvinyl Chloride 161 Ceramics 163 Summary 163 Polyurethane Immobilization 164 Fundamental Principles 164 Prepolymer Chemistry 168 The Immobilization Chemistry 169 Structure and Chemistry of Biomolecules 170 Preparation of Immobilized Biomolecules 171 Notable Uses of Polyurethane for Immobilization 174 Organophosphates 174 Lipases 177 Fibroblasts 178 Collagen 180 Amyloglucosidase 182 Novel Reactor System 184 Endothelialization 185 Creatinine 186 Conclusion to Immobilization 187 References 189 5 Controlled Release from a Hydrogel Scaffold 195 Introduction 195 Release Rates 198 Examples of Hydrogels Used for Controlled Release 198 Polysaccharides 199 Pectin 199 Alginates 200 Carrageenan 200 Agar 200 Starch 200 Proteins 200 Gelatin 200 Casein 201 Other Proteins 201 Controlled Release by Diffusion 201 Reservoir Layer 202 Diffusion Experiments 206 Islet Encapsulation 208 Other Controlled Release Examples 211 Targeted Delivery 211 Stomach 212 Small Intestines 212 Colon 212 Summary and Conclusions 213 References 213 Index 215