Polymers and Biomedical Applications.ppt
- 1. SYNTHETIC BIOMATERIALS AND POLYMERS IN MEDICINE
- 4. Biomaterials • Biomaterials are materials that are designed for in-vivo use • The study of biomaterials focuses on controlling/understanding the performance and interaction of synthetic or modified biological materials in biological systems, especially at the interface between synthetic and biological materials (biocompatibility)
- 5. A biomaterial is "any substance (other than drugs) or combination of substances synthetic or natural in origin, which can be used for any period of time, as a whole or as a part of a system which treats, augments, or replaces any tissue, organ, or function of the body". Biocompatibility — The ability of a material to perform with an appropriate host response in a specific application Host Response — The response of the host organism (local and systemic) to the implanted material or device.
- 6. Definitions • Biomaterial - Material for in-vivo use • Biocompatible - No adverse affects on biological system • Bioinert - No interaction with biological system • Bioerodable - Dissolves in biological system over time
- 7. Keywords Metallic/glass/Polymeric/Ceramic/Composite Fracture/fatigue/creep/corrosion/degradation Tissue response/healing/biocompatibility/host response/carcinogenicity Hard/soft tissue implants Vascular/Breast/Urological/Art. Organ Mucosal contacting …
- 8. Biomaterial Selection Parameters Mechanical Thermal/Electrical Conductivity Diffusion Water Absorption Biostability Biocompatibility
- 9. Biomaterial Selection Criteria • Specific Surface Interactions • Blood Contact • Need to Bear a Load • Structural Applications • Degradation Propensity • Permeability Responsiveness • Solubility under Physiological Conditions • Transparency Need • Bioenvironmental Responsiveness
- 10. Some Commonly Used Biomaterials Material Applications Silicone rubber Catheters, tubing Dacron Vascular grafts Cellulose Dialysis membranes Poly(methyl methacrylate) Intraocular lenses, bone cement Polyurethanes Catheters, pacemaker leads Hydogels Opthalmological devices, Drug Delivery Stainless steel Orthopedic devices, stents Titanium Orthopedic and dental devices Alumina Orthopedic and dental devices Hydroxyapatite Orthopedic and dental devices Collagen (reprocessed) Opthalmologic applications, wound dressings
- 11. Journals Biomaterials Biomaterials World News Materials Today Nature Journal of Biomedical Materials Research Cells and Materials Journal of Biomaterials Science Artificial Organs ASAIO Transactions Tissue Engineering Annals of Biomedical Engineering Medical Device Link … see: http://www.biomat.net/biomatnet.asp?group=1_5
- 12. A Little History on Biomaterials • Chinese, Romans, and Aztecs used gold in dentistry over 2000 years ago, Cu not good. • Ivory & wood teeth • Aseptic surgery 1860 (Lister) • Bone plates 1900, joints 1930 • Turn of the century, synthetic plastics came into use – WWII, shards of PMMA unintentionally got lodged into eyes of aviators – Parachute cloth used for vascular prosthesis • 1960- Polyethylene (PE) and stainless steel being used for hip implants
- 13. Uses of Biomaterials • Replace diseased part – dialysis • Assist in healing – sutures • Improve function – contacts • Correct function – spinal rods • Correct cosmetic – nose, ear • Aid dx – probe • Aid tx – catheter • Replace rotten – amalgam • Replace dead - skin
- 14. Problems/test for w Biomaterials • Acute toxicity (cytotoxicity) arsenic • Sub chronic/chronic Pb • Sensitization Ni, Cu • Genotoxicity • Carcinogenicity • Reproductive &/or developmental Pb • Neurotoxicity • Immunotoxicity • Pyrogen, endotoxins
- 15. Evolution of Biomaterials Structural Functional Tissue Engineering Constructs Soft Tissue Replacements
- 16. Biomaterials for Tissue Replacements • Bioresorbable vascular graft • Biodegradable nerve guidance channel • Skin Grafts • Bone Replacements
- 17. Biomaterials - An Emerging Industry • Next generation of medical implants and therapeutic modalities • Interface of biotechnology and traditional engineering • Significant industrial growth in the next 15 years -- potential of a multi-billion dollar industry
- 18. Synthetic Biomaterial Classes • METALS: Co-Cr alloys, Stainless steels, Gold, Titanium alloys, Vitallium, Nitinol (shape memory alloys) Uses: orthopedics, fracture fixation,dental and facial reconstruction,stents • CERAMICS: Alumina, Zirconia, Calcium Phosphate, Pyrolitic Carbon Uses: orthopedics, heart valves, dental reconstruction • COATINGS: Bioglasses, Hydroxyapatite, Diamond-like carbon Uses: orthopedics, in-growth
- 19. Synthetic Biomaterial Classes cont. • POLYMERS: Silicones, Gore-tex (ePTFE), Polyethylenes(LDPE,HDPE,UHMWPE,) Polyurethanes, Polymethylmethacrylate,Polysulfone, Delrin Uses:orthopedics, artificial tendons,catheters, vascular grafts, facial and soft tissue reconstruction • COMPOSITES: CFRC, self reinforced, hybrids Uses:orthopedics, scaffolds • HYDROGELS: Cellulose, Acrylic co-polymers Uses:drug delivery, vitreous implants,wound healing • RESORBABLES: Polyglycolic Acid, Polylactic acid, polyesters Uses: sutures,drug delivery, in-growth, tissue engineering
- 20. Metals • Metals are (mostly) crystalline solids composed of elemental, positively charged ions in a cloud of electrons – Properties are a function of grain size, imperfections in crystal structure – Metals comprised of more than one element are alloys – The surface of metals are often oxides, if inert leads to protection, if active is corrosion • Typical metal properties include: – High melting points – High stiffness and strength – High conductivities – isotropic properties
- 21. Why Use Metals as Biomaterials • Properties and fabrication well known • Stiff and strong • Bioinert • Joining technologies known • Metals commonly used – Titanium – Stainless steel
- 22. Figure 4.1 These titanium-alloy joint replacements are an example of the many applications for metal biomaterials for implantations. (from http://www.spirebiomedical.com)
- 23. Ceramics • Ceramics are compounds characterized by ionic or covalent bonding • Ceramics are generally crystalline, crystalline SiO2 is quartz • Glasses are the amorphous “ceramics” common glass is amorphous SiO2 • Properties – Properties function of grain size, imperfections in crystal structure – Many ceramics comprised of more than one compound – Low conductivities (semi-conductors, insulators) – Stiff and Brittle
- 24. Why Use Ceramics as Biomaterials • Properties and fabrication well known • Stiff and strong • Bioinert • Obvious fix for teeth and bones
- 28. Metals Semiconductor Materials Ceramics Polymers Synthetic BIOMATERIALS Orthopedic screws/fixation Dental Implants Dental Implants Heart valves Bone replacements Biosensors Implantable Microelectrodes Skin/cartilage Drug Delivery Devices Ocular implants
- 29. Issues • Understanding and controlling performance – Physical – Chemical – Biological • Relevant material performance is under biological conditions – 37 C, aqueous, saline, extracelluar matrix (ECM) – Material properties as a function of time • Initial negative biological response - toxicity • Long term biological response – rejection • Biology is a science of surfaces and interfaces – Seldom (never) at equilibrium
- 30. Materials Lessons from Biology • Polymer based • Nanoscaled • Energy efficient • Self-healing • Ecologically sound • Self-improving • Smart! Biology represents a material/ part/system strategy that works
- 33. A Brief Introduction of Polymer A polymer is generally named based on the monomer it is synthesized from. For example, ethylene is used to produce poly(ethylene) (PE). For both glycolic acid and lactic acid, an intermediate cyclic dimer is prepared and purified, prior to polymerization. These dimers are called glycolide and lactide, respectively. Although most references in the literature refer to polyglycolide or poly(lactide), you will also find references to poly(glycolic acid) and poly(lactic acid). Poly(lactide) exists in two stereo forms, signified by d or l for dexorotary or levorotary, or by dl for the racemic mix. HOMOPOLYMER (one monomer)
- 34. Polymers • Terminology (contn): – copolymer: polymers of two mer types • random · · ·-B-A-B-A-B-B-A-· · · • alternating· · ·-A-B-A-B-A-B-A-· · · • block · · ·-A-A-A-A-B-B-B-· · · – heteropolymer: polymers of many mer types COPOLYMER
- 37. Polyurethanes A urethane has an ester group and amide group bonded to the same carbon. Urethanes can be prepare by treating an isocyanate with an alcohol. RN C O ROH RNH C O OR + an isocyanate an alcohol a urethane Polyurethanes are polymers that contain urethane groups. O C N CH3 N C O toluene-2,6-diisocyanate + HOCH2CH2OH ethylene glycol C O NH CH3 NH C O OCH2CH2O C O NH NH C O OCH2CH2O C O CH3 n a polyurethane
- 39. I. Biodegradable Polymers O O n O O n O O O O n m PGA Tm= 225C Tg = 36C PPL Tm= 80C Tg = -24C PCL Tm= 61C Tg = -60C PLA Tm= 180C Tg = 60C PLGA Tg ~ 50 C O O n O O n
- 41. Synthetic Polymers Biodegradable Synthetic Polymers • Poly(alkylene ester)s • PLA, PCL, PLGA • Poly(aromatic/aliphatic ester)s • Poly(amide-ester)s • Poly(ester-urethane)s • Polyanhydrides • Polyphosphazenes Biostable Polymers • Polyamides • Polyurethanes • Polyethylene • Poly(vinylchloride) • Poly(hydroxyethylmethacrylate) • Poly(methylmethacrylate) • Poly(tetrafluoroethylene) • Poly(dimethyl siloxane) • Poly(vinylalcohol) • Poly(ethylenglycol) Stimuli Responsive Poly(ethylene oxide-co-propilene oxide) Poly(methylvinylether) Poly(N-alkyl acrylamide)s Poly(phosphazone)s
- 52. Polymers: Biomedical Applications • Polyethylene (PE) – five density grades: ultrahigh, high, low, linear low and very low density – UHMWPE and HDPE more crystalline – UHMWPE has better mechanical properties, stability and lower cost – UHMWPE can be sterilized
- 53. Polymers: Biomedical Applications • UHMWPE: acetabular caps in hip implants and patellar surface of knee joints • HDPE used as pharmaceutical bottles, fabrics • Others used as bags, pouches, tubes etc.
- 54. Artificial Hip Joints (UHMWPE) http://www.totaljoints.info/Hip.jpg
- 55. Polymers: Biomedical Applications • Polymethylmethacrylate (PMMA, lucite, acrylic,plexiglas) – acrylics – transparency – tough – biocompatible • Used in dental restorations, membrane for dialysis, ocular lenses, contact lenses, bone cements
- 56. Intraocular Lens 3 basic materials - PMMA, acrylic, silicone
- 57. Polymers: Biomedical Applications • Polyamides (PA, nylon) – high degree of crystallinity – interchain hydrogen bonds provide superior mechanical strength (Kevlar fibers stronger than metals) – plasticized by water, not good in physiological environment • Used as sutures
- 58. Polymers: Biomedical Applications • Polyvinylchloride (PVC) (monomer residue must be very low) – Cl side chains – amorphous, hard and brittle due to Cl – metallic additives prevent thermal degradation • Used as blood and solution bags, packaging, IV sets, dialysis devices, catheter, bottles, cannulae
- 59. Polymers: Biomedical Applications • Polypropylene (PP) – properties similar to HDPE – good fatigue resistance • Used as syringes, oxygenator membranes, sutures, fabrics, vascular grafts • Polyesters (PET) – hydrophobic (beverage container PET) – molded into complex shapes • Used as vascular grafts, sutures, heart valves, catheter housings
- 60. Polymers: Biomedical Applications • Polytetrafluoroethylene (PTFE, teflon) – low coefficient of friction (low interfacial forces between its surface and another material) – very low surface energy – high crystallinity – low modulus and strength – difficult to process • catheters, artificial vascular grafts
- 61. Synthetic vascular grafts from W.L.Gore
- 62. Polymers: Biomedical Applications • Rubbers – latex, silicone – good biocompatibility • Used as maxillofacial prosthetics
- 63. Figure 4.3 This artificial heart valve is coated with Silizone, a biocompatible material that allows the body to accept the implant. (from http://www.sjm.com/devices/).
- 64. Polymers: Biomedical Applications • Polyurethanes – block copolymer structure – good mechanical properties – good biocompatibility • tubing, vascular grafts, pacemaker lead insulation, heart assist balloon pumps
- 66. Polymers in the body