Biomaterials - Introduction (wk. 1)

Christine Luk
Flashcards by , created over 2 years ago

BME32105 Lecture 1 Credit to Professor Mo Yang at the Hong Kong Polytechnic University

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Christine Luk
Created by Christine Luk over 2 years ago
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Question Answer
Fingerjoint Silicone rubber
Breast Implant Silicones
Heart Valve Polyester Stainless Steel
Hip Joint Titanium
Artificial Heart Polyurethane Metal
Intraocular Lens (IOL) Poly(methyl methacrylate)
Applications of Biomaterials: Sutures Name 5 advantages AMAGE (town in France) - Any tissue - Minimal tissue reaction - Absorbable - Good knot security - Easy to handle
Intraocular Lens - name a) materials b) 3 properties a) Poly(methyl methacrylate) PMMA b) 1) high refractive index (n) 2) easily processed 3) environmentally stable (relatively inert)
Name as many medical device examples as you can. There are 12 on the slides Sutures, Catheters, Blood Bags Contact Lenses, IOL, Knee & Hip, Breast Prostheses Dental implants, Renal dialyzers Oxygenators, CPB (cardiopulmonary bypass system) Vascular grafts, pacemakers
Which are Biomaterials? why? a) contact lens b) splinter c) vascular graft d) clutches a) & c) A biomaterial must interface with the biological system directly. When used, nothing between the device and person using it. The splinter and clutches can be held through gloves or other things.
Biomaterial material interface w biological system to treat/evaluate/augment/replace tissues/organs/bodily functions
Biomaterials Science study of biomaterials and their interactions with biological environment, includes 1) Materials Science 2) Biological topics: immunology, toxicology, wound healing process
biocompatibility ability of a material to perform w an apropriate host response in a specific application
Reasoning Biocompatibility Protein & cellular response to material which determines overall success of the implant. Arises from differences between living and non-living materials
Biocompatibility responses: 1) temporal 2) other temporal response: redness, swelling, warmth, pain around implant other: activation of immune system, localized blood clotting, infection, tumor formation
Bioimplants trigger.... Inflammation & Foreign body response(FBR)
biocompatibility testing in vitro: lab environment in vivo: biomaterial implantation in a living system (animal, rat)
biocompatibility testing agencies ASTM International International Organisation for Standardization (ISO)
biocompatibility testing steps Not all products all steps 1) in vitro 2) in vivo healthy 3) in vivo sick (inject disease, then drug) 4) controlled clinical trials
New testing required for a) new devices b) new materials c) both new devices and materials a) new devices FDA approves Devices not Materials.
amount of testing depends on perceived danger intended use (device class)
Types of biomaterials eec6471a-6789-433a-84b4-b70c8a92d4e5.PNG (image/PNG)
Cobalt-chromium alloys: Co-Cr Applications (3) artificial heart valves dental prostheses artificial joint components
Au, Pt Gold & Platinum Dental fillings, electrodes for cochlear implants
Silver-tin-copper alloys Ag-Sn-Cu dental amalgrams
Stainless steel dental prosthesis vascular stents
Titanium alloys artificial heart valve artificial joint components pacemaker cases
Ceramics: aluminum oxide Al2O3 Orthopedic joint replacement components
Ceramics: Bioactive glasses Bone graft substitute materials, dental implants
Ceramics: Calcium Phosphates bone graft substitute materials, dental implants, bone cements
Natural Polymers Can be derived from sources w/in body (collagen, fibrin) or outside the body (chitosan [from seafood shells], alginate) Collagen: Collagen type I & II Fibrin: protein-based, blood clotting factors = fibrinogen + thrombin chitosan = chitin derived from the shells of crabs, shrimps
Collagen long, fibrous, extremely strong protein inside connective tissue. keeps skin elastic
Fibrin repairs cartilage defects, other orthopedic applications
Chitosan commonly sold as tablet "fat attracter" - attract fat and expel from body for weight loss.
Synthetic polymers Elastomers: -highly elastic, w/stand large deformation at low stress and rebound. - good for cardiovascular applications, wherever tissue elasticity is requried - EXAMPLE: polydimethylsiloxane (PDMS) Hydrogels: -swell in water, retain water in structure - suitable for soft tissue applications - polyethylene glycol (PEG)
Natural vs. Synthetic Polymers 06d6c414-5db0-4cc9-a540-cc44ff00d652.PNG (image/PNG)
Which class(es) of biomaterials for an artificial tendon? why? [hint: a tissue that must sustain substantial deformation at low forces and return rapidly to its original dimensions upon release of stress] a) metals b) ceramics c) polymers C) Polymers especially elastomers because of elasticity (ability to withstand large deformations at low stress and rebound)
Important properties of biomaterials: The selection of biomaterials for a given application is determined by: (3) 1) degradative 2) surface properties 3) bulk properties
Biodegradable ability to break down safely, reliable, and relatively quickly can be undesired/desired, time before failure important to check biocompatibility during degradation too
Medical Applications of Biodegradable Poolymers 04cdf5de-0e68-4343-8492-a481b83c3d4b.PNG (image/PNG)
What are the 4 layers of a biomaterial interfacing with a biological system? ca1d8a08-9704-4fc3-9968-3ce81a4f3379.PNG (image/PNG)
Importance: Surface properties - a few atomic layers of the exterior - determines biological response - determines protein absorption - surface properties can be different from the bulk properties (due to surface modification/special surface processing)
chemical vs physical characteristics (surface property) chemical: hydophobicity/hydrophilicity physical: surface roughness (increases cell adhesion)
Would a hydrophobic or hydrophilic polymer be more appropriate for a contact lens application? Why? Would a melting temperature of the polymer above or below 37 degrees be better? why? Hydrophilic - eye is a watery environment above - you don't want it to melt
importance: Bulk properties smaller role than surface characteristics but have a long term impact
mechanical, physical, chemical properties (bulk property) mechanical properties: - strength, stiffness -anisotropy: different mechanical properties in different directions fatigue physical: crystallinity, thermal transitions chemical: hdyrophobicity
spectroscopy measures how compounds absorb different types of energy
chromatography physically separates molecules based on chemical characteristics (i.e., charge or size)