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14 biomaterials


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  • 1. Liu Nanobionics Lab Biomaterials Tissue Engineering Nanotechnology
  • 2. Biomaterials Biomaterials encompasses aspects of medicine, biology, chemistry, engineering and materials science. Biomaterials are : “Non-viable materials used in a medical devices intended to interact with biological systems” [D.F. Williams, 1987]
  • 3. Human Tissue Damage Disease (e.g cancer, infection, degenerative diseaes). Trauma (e.g accidental, surgery). Congenital abnormalities (e.g birth defects). Current clinical treatment based on: Grafts and TransplantsArtificial Biomaterials
  • 4.  Tissue loss as a result of injury or disease, in an increasing ageing population, provides reduced quality of life for many at significant socioeconomic cost. Thus a shift is needed from tissue replacement to tissue regeneration by stimulation the body’s natural regenerative mechanisms.
  • 5. Biomaterials: Examples Joint replacements Bone plates Bone cement Hip Joint Artificial ligaments and tendons Dental implants for Heart valve Hip joint tooth fixation Blood vessel prostheses Heart valves Skin repair devices Cochlear replacements Knee joint Skin Contact lenses
  • 6. Biomaterials Prostheses have significantly improved the quality of life for many ( Joint replacement, Cartilage meniscal repair, Large diameter blood vessels, dental) However, incompatibility due to elastic mismatch leads to biomaterials failure.
  • 7. Tissue Engineering National Science Foundation first defined tissue engineering in 1987 as “ an interdisciplinary field that applies the principles of engineering and the life sciences towards the development of biological substitutes that restore, maintain or improve tissue function”
  • 8. Tissue engineering Potential advantages: unlimited supply no rejection issues cost-effective
  • 9. Tissue Engineering Expand number in culture Remove cells from the body.Seed onto an appropriatescaffold with suitable growthfactors and cytokines Re-implant engineered tissue repair damaged site Place into culture
  • 10.  SCAFFOLDS
  • 11. Synthetic polymers More controllable from a compositional and materials processing viewpoint. Scaffold architecture are widely recognized as important parameters when designing a scaffold They may not be recognized by cells due to the absence of biological signals.
  • 12. Natural polymers Natural materials are readily recognized by cells. Interactions between cells and biological materials are catalysts to many critical functions in tissues These materials have poor mechanical properties.
  • 13. Tissue engineering scaffold:Self-assembly Self-aggregation of hydrophilic, lipophilic groups First layer creates template for growth of second layer Ions can be deposited on charged sites This kind of self- aggregation leads to ordered, heirarchical structures
  • 14. Supramolecular Chemistry
  • 15. Tissue engineering scaffold: controlled architectureFeatured with:Pre-defined channels;with highly porousstructured matrix;With suitable chemistryfor tissue growth –Collagen or HANo toxic solvent involved,it offers a strong potentialto integrate cells/growthfactors with the scaffoldfabrication process.
  • 16. Architecture of Hard Tissue Staggered mineral platelets (hydroxyapataite) embedded in a collagen matrix Arrangement of platelets in preferred orientations makes biocomposites intrinsically anisotropic Under an applied tensile stress, the mineral platelets carry most of the tensile load Protein matrix transfers the load between mineral crystals via shear Biocomposites can be described through tension-shear model described by Ji et. al.
  • 17. Tissue engineering scaffold: Electrospinning This process involves the ejection of a charged polymer fluid onto an oppositely charged surface. Multiple polymers can be combined Control over fiber diameter and scaffold architecture
  • 18. Printing Techniques for Tissue Engineering
  • 19. Techniques to study scaffolds: Scanning Probe Microscopy Atomic Force Microscopy :Surface irregularities Scanning Tunneling Microscopy: Conducting Surfaces Adhesion Force Microscopy: Functionalised tips
  • 20. Surface Modification of Biomaterials
  • 21. Enhanced intrinsic biomechanical properties of osteoblastic mineralized tissue on roughened titanium surface  Nano-indentation  Acid-etched vs. Machined surfaces  culturing osteoblasts on rougher titanium surfaces enhances hardness and elastic modulus of the mineralized tissue
  • 22. Surface modification of SPU  Segmented Polyurethane – common biocompatible elastomer  2-methacryloyloxyethyl phosphorylcholine added to create nano-domains on surface  Nano-scale domains reduce platelet adhesion to biomaterial surfaceNano-scale surface modification of a segmented polyurethane with a phospholipid polymer, Biomaterials 25 (2004) 5353–5361
  • 23. Protecting Bionic Implants
  • 24. Immunoisolation for Cell-encapsulation therapy Liver Dysfunction: Encapsulation of Hepatic Cells Pancreas Dysfunction: Encapsulation of Islets of Langerham Disorders of the CNS: Parkinson’s, Alzheimer’s Pre-requisites for cell encapsulation  continued and optimal tissue/cell supply  maintenance of cell viability and function  successful prevention of immune rejection Nanoporous Silicone-based biocapsules serves as Artificial Pancreas(Desai et al. 2001) What are the drawbacks of such an artificial pancreas?
  • 25. Nanoengineering Bio-analogousStructures Bone-cartilage composite ? Muscle ? Brain-machine Interface ?
  • 26. An Ink-Jet Printer for Tissue Engineering?