14 biomaterials

• 1. Liu Nanobionics Lab Biomaterials Tissue Engineering Nanotechnology

2. Biomaterials Biomaterials encompasses aspects ofmedicine, biology, chemistry,engineering and materials science. Biomaterials are : Non-viablematerials used in a medical devicesintended to interact with biologicalsystems [D.F. Williams, 1987] 3. Human Tissue Damage Disease (e.g cancer, infection, degenerativediseaes). 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 ordisease, in an increasing ageingpopulation, provides reduced qualityof life for many at significantsocioeconomic cost. Thus a shift is needed from tissuereplacement to tissue regeneration bystimulation the bodys naturalregenerative mechanisms. 5. Biomaterials: Examples Joint replacements Bone plates Bone cement Hip Joint Artificial ligamentsand tendons Dental implants forHeart valve Hip jointtooth fixation Blood vesselprostheses Heart valves Skin repair devices Cochlearreplacements Knee joint Skin Contact lenses 6. Biomaterials Prostheses have significantlyimproved the quality of life formany ( Joint replacement, Cartilagemeniscal repair, Large diameterblood vessels, dental) However, incompatibility due toelastic mismatch leads tobiomaterials failure. 7. Tissue Engineering National Science Foundation first definedtissue engineering in 1987 as aninterdisciplinary field that applies theprinciples of engineering and the lifesciences towards the development ofbiological substitutes that restore,maintain or improve tissue function 8. Tissue engineering Potential advantages:unlimitedsupplyno rejection issuescost-effective 9. Tissue EngineeringExpand number in culture Remove cells from the body.Seed onto an appropriatescaffold with suitable growthfactors and cytokines Re-implant engineered tissue repair damaged sitePlace into culture 10. SCAFFOLDS 11. Synthetic polymers More controllable from acompositional and materialsprocessing viewpoint. Scaffold architecture are widelyrecognized as important parameterswhen designing a scaffold They may not be recognized by cellsdue to the absence of biologicalsignals. 12. Natural polymers Natural materials are readilyrecognized by cells. Interactions between cells andbiological materials are catalysts tomany critical functions in tissues These materials have poormechanical properties. 13. Tissue engineering scaffold:Self-assembly Self-aggregation ofhydrophilic, lipophilicgroups First layer createstemplate for growth ofsecond layer Ions can be deposited oncharged sites This kind of self-aggregation leads toordered, heirarchicalstructures 14. Supramolecular Chemistryhttp://www.chm.bris.ac.uk/webprojects2003/lee/supra1.jpg 15. Tissue engineering scaffold:controlled architectureFeatured with:Pre-defined channels;with highly porousstructured matrix;With suitable chemistryfor tissue growth Collagen or HANo 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 acollagen matrix Arrangement of platelets inpreferred orientations makesbiocomposites intrinsicallyanisotropic Under an applied tensile stress,the mineral platelets carry mostof the tensile load Protein matrix transfers the loadbetween mineral crystals viashear Biocomposites can be describedthrough tension-shear modeldescribed by Ji et. al. 17. Tissue engineering scaffold:Electrospinning This process involves the ejection of a charged polymer fluid onto an oppositelycharged 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 ForceMicroscopy :Surfaceirregularities Scanning TunnelingMicroscopy:Conducting Surfaces Adhesion ForceMicroscopy:Functionalised tips 20. Surface Modification of Biomaterials 21. Enhanced intrinsic biomechanical properties of osteoblasticmineralized tissue on roughened titanium surface Nano-indentation Acid-etched vs. Machinedsurfaces culturing osteoblasts onrougher titanium surfacesenhances hardness andelastic modulus of themineralized tissue 22. Surface modification of SPU Segmented Polyurethane common biocompatibleelastomer 2-methacryloyloxyethylphosphorylcholine addedto create nano-domainson surface Nano-scale domainsreduce platelet adhesionto biomaterial surfaceNano-scale surface modification of a segmented polyurethane with a phospholipid polymer, Biomaterials 25 (2004) 53535361 23. Protecting Bionic Implants 24. Immunoisolation for Cell-encapsulation therapy Liver Dysfunction: Encapsulation ofHepatic Cells Pancreas Dysfunction: Encapsulation ofIslets of Langerham Disorders of the CNS: Parkinsons,Alzheimers 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 biocapsulesserves as Artificial Pancreas(Desai etal. 2001) What are the drawbacks of such anartificial pancreas? 25. Nanoengineering Bio-analogousStructures Bone-cartilagecomposite ? Muscle ? Brain-machineInterface ? 26. An Ink-Jet Printer for Tissue Engineering?