Nanodispersions

Description

General introduction - Definition of nanodispersions (nanosuspensions, nanoemulsions, swollen micelles or microemulsions, liposomes and vesicles) and their size range. General description of their colloid stability. Main advantages of nanodispersions and their industrial applications. Preparation of nanosuspensions by top-up process - Nucleation and growth and control of particle size distribution. Factors determining the formation of narrow particle size distribution. Role of surfactants and polymers. Preparation of nano-polymer colloids (lattices) by emulsion and dispersion polymerization. Factors affects the stability of nanosuspensions. Preparation of nanosuspensions by bottom down process - Dispersion of preformed particles in liquids and the need of a wetting agent. Break-up of aggregates and agglomerates by application of high speed stirrers. Reduction of particle size by application of intense energy (microfluidization or bead milling). Maintenance of the colloid stability of the resulting particles. Reduction of Ostwald ripening. Industrial applications of nanosuspensions - Application in pharmacy to enhance bioavailability, Application in sunscreens for UV protection. Application in paints and coatings. Preparation of nanoemulsions by the use of high pressure homogenisers - Principles of emulsion formation and the role of the emulsifier. Selection of emulsifiers. Methods of emulsification and prevention of coalescence during emulsification. Origin of colloid stability of nanoemulsions. Prevention of Ostwald ripening Low energy methods for nanoemulsion preparation - The phase inversion composition method and the role of mixing the surfactant with oil and water. The phase inversion temperature method for preparation of nanoemulsions. Preparation of nanoemulsions by dilution of microemulsions. Practical examples of nanoemulsions and their industrial application - Nanoemulsions based on non-ionic surfactants and the role of the hydrophilic-lipophilic balance. Effect of oil solubility on the stabilityof nanoemulsions. Nanoemulsions based on polymeric surfactants. Applications in pharmacy and cosmetics. Swollen micelles or microemulsionsDefinition of microemulsions and their size range. Thermodynamic definition of microemulstions. Theories of microemulsion formation and stability. Characterisation of microemulsions using scattering, conductivity and NMR rechniques. Formulation of microemulsions and their industrial applications - Distinction between microemulsions and macroemulsions. Formulation of oil/water and water/oil microemulsions. Selection of emulsifiers for microemulsions. Application of microemulsions in tertiary oil recovery. Liposomes and vesicles - Formation of multilamellar lipid layers (liposomes) by dispersion of lipids in water. Formation of unilamellar vesicles by sonication of the liposomes. Factors responsible for stabilisation of liposomes and vesicles. Use of block copolymers to enhance the stability of vesicles. Applications of liposomes and vesicles in pharmacy and cosmetics. A concise and accessible overview of the nanodispersions (nanosuspensions, nanoemulsions and microemulsions). Highly practical in approach, introducing briefly the science, followed by industrial applications. Preface Contents 1 Nanodispersions – general introduction 1.1 Definition of colloids 1.2 Definition of nanodispersions 1.3 Main advantages of nanodispersions 1.4 General methods for preparation of nanodispersions 1.5 General stabilization mechanisms for nanodispersions 1.6 Ostwald ripening in nanodispersions 1.7 Industrial applications of nanodispersions 1.8 Outline of the book 2 Colloid stability of nanodispersions 2.1 Introduction 2.2 Electrostatic stabilization 2.3 Steric stabilization 3 Ostwald ripening in nanodispersions 3.1 Driving force for Ostwald ripening 3.2 Kinetics of Ostwald ripening 3.3 Reduction of Ostwald ripening 3.3.1 Reduction of Ostwald ripening in nanosuspensions 3.3.2 Reduction of Ostwald ripening in nanoemulsions 3.4 Influence of initial droplet size of nanoemulsions on the Ostwald ripening rate 4 Preparation of nanosuspensions by the bottom-up process 4.1 Introduction 4.2 Preparation of nanosuspensions by precipitation 4.2.1 Nucleation and growth 4.2.2 Precipitation kinetics 4.2.3 Seeded nucleation and growth 4.2.4 Surface modification 4.2.5 Other methods for preparation of nanosuspensions by the bottom-up process 4.3 Characterization of nanoparticles 4.3.1 Visual observations and microscopy 4.3.2 Electron microscopy 4.3.3 Scattering techniques 4.3.4 Measurement of charge and zeta potential 5 Preparation of nanosuspensions using the top-down process 5.1 Wetting of the bulk powder 5.2 Breaking of aggregates and agglomerates into individual units 5.3 Wet milling or comminution 5.4 Stabilization of the suspension during dispersion and milling and the resulting nanosuspension 5.5 Prevention of Ostwald ripening (crystal growth) 6 Industrial application of nanosuspensions 6.1 Introduction 6.2 Application of nanosuspensions for drug delivery 6.2.1 Preparation of drug nanosuspensions using the top-down process 6.2.2 Optimization of wetting/dispersant agent using PVP-SDS as model 6.2.3 Protocol for preparation of nanosuspensions of water insoluble drugs 6.3 Application of nanosuspensions in cosmetics 6.3.1 Adsorption isotherms 6.3.2 Dispersant demand 6.3.3 Quality of dispersion UV-vis attenuation 6.3.4 Solids loading 6.3.5 SPF Performance in emulsion preparations 6.3.6 Criteria for preparation of a stable sunscreen dispersion 6.3.7 Competitive interactions in formulations 6.4 Application of nanosuspensions in paints and coatings 7 Nanoparticles as drug carriers 7.1 Introduction 7.2 Liposomes as drug carriers 7.3 Polymeric nanoparticles 7.3.1 Surface modified polystyrene latex particles as model drug carriers 7.3.2 Biodegradable polymeric carriers 7.3.3 The action mechanism of the stabilizing PEG chain 7.3.4 Synthesis and characterization of PLA-PEG block copolymers 7.3.5 Preparation and characterization of PLA-PEG nanoparticles 7.3.6 Rheology of PLA-PEG dispersions 7.3.7 Small angle neutron scattering (SANS) of PLA-PEG nanoparticles 7.3.8 Biological performance of PLA-PEG nanoparticles 8 Preparation of nanoemulsion using high pressure homogenizers 8.1 Introduction 8.2 Thermodynamics of emulsion formation and breakdown 8.3 Adsorption of surfactants at the liquid/liquid interface 8.4 Mechanism of emulsification 8.5 Methods of emulsification 8.6 Role of surfactants in emulsion formation 8.7 Role of surfactants in droplet deformation 8.8 Selection of emulsifiers 8.8.1 The hydrophilic-lipophile balance (HLB) concept 8.8.2 The phase inversion temperature (PIT) concept 8.8.3 The cohesive energy ratio (CER) concept 8.8.4 The critical packing parameter (CPP) for emulsion selection 8.9 Preparation of nanoemulsions using high energy methods 8.10 Emulsification process functions 8.11 Enhancing of the process of forming nanoemulsions 9 Low energy methods for preparation of nanoemulsions and practical examples of nanoemulsions 9.1 Introduction 9.2 Phase inversion composition (PIC) Principle 9.3 Phase inversion temperature (PIT) Principle 9.4 Preparation of nanoemulsions by dilution of microemulsions 9.5 Steric stabilization and the role of the adsorbed layer thickness 9.6 Ostwald ripening in nanoemulsions 9.7 Practical examples of nanoemulsions 9.8 Nanoemulsions based on polymeric surfactants 10 Swollen micelles or microemulsions and their industrial applications 10.1 Introduction 10.2 Thermodynamic definition of microemulsions 10.3 Mixed film and solubilization theories of microemulsions 10.3.1 Mixed film theories [4] 10.3.2 Solubilization theories 10.4 Thermodynamic theory of microemulsion formation 10.4.1 Reason for combining two surfactants 10.4.2 Free energy of formation of a microemulsion 10.4.3 Factors determining W/O versus O/W microemulsions 10.5 Characterization of microemulsions using scattering techniques 10.5.1 Time average (static) light scattering 10.5.2 Calculation of droplet size from interfacial area 10.5.3 Dynamic light scattering (photon correlation spectroscopy, PCS) 10.5.4 Neutron scattering 10.5.5 Contrast matching for determining the structure of microemulsions 10.6 Characterization of microemulsions using conductivity 10.7 NMR measurements 10.8 Formulation of microemulsions 10.9 Industrial applications of microemulsions 10.9.1 Microemulsions in pharmaceuticals 10.9.2 Applications of microemulsions in cosmetics 10.9.3 Applications in agrochemicals 10.9.4 Applications in the food industry 10.9.5 Microemulsions in biotechnology 10.9.6 Microemulsions in enhanced oil recovery (EOR) 10.9.7 Microemulsions as nanosize reactors for synthesis of nanoparticles Index