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1、Biomaterials,Biomaterials,Non-viable material used in a medical device intended to interact with biological systemsMaterial intended to interact with biological systems,Biomaterials Science,Physical and biological study of materials and their interaction with the biological environmentSynthesisOptim
2、izationTestingBiology of host-material interactions,Ratner(1993)characterized body response to these materials as“blah”Non specificSluggish kineticsBroad spectrum of active processes occurringProteins 200+to choose fromCells(neutrophils,macrophages,platelets)well adapted to respond to these proteins
3、,What we get,What we really want,Development of engineered surfaces that elicit rapid and highly precise reactions with cells and proteinsTailored to specific applicationResistance to blood clottingResistance to bacterial infectionNormal uncomplicated healing,Biomaterials History,“Hero surgeons”Ridl
4、ey and IOLsHip and knee prostheses Canadian connectionKidney dialysisBreast implantsVascular graftsStents,The Terylene,Orlon or nylon cloth is bought from a drapers shop and cut with pinking shears to the required shape.It is then sewn with thread of similar material into a tube and sterilized by au
5、toclaving before use.,The Current State of Affairs,Medical devices are regulated by the FDASome devices are grandfathered based on being available prior to the legislation introductionClassified based on safety and potential impact to human health,Materials Commonly Used in Biomaterials Applications
6、,Synthetic PolymersHydrogelsPolyurethanesSilicone based materialsTeflonDacronPoly(ethylene oxide)Degradable materialsNatural Polymers and Other Natural Materials,MetalsCeramics,glasses and glass-ceramicsPyrolitic CarbonComposite,Materials and Medical Uses,The Biomaterials Scientist:A Jack of All Tra
7、des,Computational chemistryMolecular biologySurface physics/chemistryNanofabricationMaterials science,Materials Properties,BulkSurface,Mechanical Properties of Materials,Elastic Behaviour of Materials,Solid material subjected to tensile force will extend in the direction of traction by an amount pro
8、portional to the load,Stress and Strain,Extension for a given load varies with geometry and compositionNormalization of load and deformation to allow comparison of different materialsNormalized load(force/area)is stress(s),normalized deformation is strain(e)Stress strain curve is generated from this
9、 data,Typical Stress Strain Curve,Other Properties,Tension and compressionArea supporting the load is perpendicular to the loading direction,change in length is parallel to original lengthShearApplied load is parallel to the area supporting it,Tensile and Shear Modulus,Mechanical Testing,Other Bulk
10、Properties,PorosityPermeability,Surface Properties,Concerned with function(related to design),durability(related to bulk properties)and biocompatibility(related to surface properties),Biocompatibility,Overused termDefined asThe ability of a material to perform with an appropriate host response in a
11、specific applicationThe exploitation by materials of the proteins and cells of the body to meet a specific performance requirement,Surface properties direct the biological responseNot toxicologyMechanical and functional design,while critical,are not central to biocompatibility,The Surface,Surface of
12、 a material is invariably different from its bulkThere is not much total mass on a surfaceMicroelectronics example:1 cm3 cube of Ti contains a 100 layer of oxide.This can be compared to a 5 m wide beach on each coast of the USSurfaces readily contaminate with components from the vapour phase,Figure
13、2:Changes to PHEMA,Figure 3 Ratner,So,We need to control the surfaceCreate a surface that mimics the native biology in order to develop materials that are“biocompatible”Need to characterize the surface,Biomimetics,Approaches that mimic or replicate the natural function of tissues are often the most
14、successfulComplexity of natural tissues and organs is still far beyond the ability of science for replicationPrecise function of every aspect of the tissue or organ is not knownGeneral concepts have emerged from study of structural biology that provide design strategies and guidance,Cells are geneti
15、cally programmed to build organs and tissuesCells produce proteins,polysaccharides,glycoproteins,lipids that assemble into composite extracellular matricesCells communicate via growth factors and their recruitmentBlood vessels play a crucial role in tissue growth by providing nutrients,a means for w
16、aste removal and a supply of additional cellsNervous system is responsible for the integration and control of all of the bodies functions,We therefore have some understanding ofCell processesProtein adsorptionWound healingSuccessful treatment of medical conditionBut lacking understanding of the rela
17、tionship between the events that occur at the surface and the final successful outcome,The Future,Biomaterials will not fight biology but will integrate into the biological systemBiomaterials science versus biomaterials engineeringMaterials and biology working together,Self-assembled materialsSurfac
18、e modified materials for promotion of cell interactionsPhotonic materialsMaterials which mimic the ECM,A New Definition of Biocompatibility,Biostable materials which pass routine toxicological tests heal indistinguishably when implanted in soft tissueIntegration rather than isolation of a biocompatible materialMaintenance of the ability to heal complex wounds,Elimination of long term macrophage responseBetter understanding of the nature of the fibrotic responseMaintenance of normal wound healing,
