Biomedical Engineering Theory And Practice/Biomaterials
Biomaterials science and engineering is a interdisciplinary field merging medicine, pharmaceuticals, biology, physics, chemistry, materials science, engineering, ethics and so on.
- 1 Introduction
- 2 Requirements for Biomaterials
- 3 Classes of Biomaterials
- 4 Summary
- 5 Further Reading
- 6 Practise
- 7 Reference
The United States National Institute of Health Consensus Development Conference defined a biomaterial as ‘‘Any substance (other than a drug) 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’’ (Boretos and Eden, 1984). Biomaterials area has grown over for 50 years. Biomaterils as a field uses ideas from medicine, biology, chemistry, materials science and engineering. In addition, biomaterials researchers should consider ethics,law and the health care delivery system.
Biomaterials can be divided into metals, ceramics, polymers, glasses, carbons, and composite materials. Table 1 shows a few applications for synthetic materials in the body. It contains many materials that are often classified as “biomaterials.” Metals,ceramics, polymers, glasses, carbons, and composite materials are listed in this table. Such materials are used as molded or machined parts, coatings, fibers, films, foams,fabrics,liquid and powder.
Table 1. Some Applications of Synthetic Materials and Modified Natural Materials in Medicine
|Application||Types of materials|
|Skeletal system||Joint replacements(hip, knee)||Titanium, Ti–Al–V alloy, stainless steel, polyethylene|
|Bone plate for fracture fixation||Stainless steel, cobalt–chromium alloy|
|Bone cement||Poly(methyl methacrylate)|
|Bony defect repair||Hydroxylapatite|
|Artificial tendon and ligament||Teflon, Dacron,biodegradable hydrogel|
|Dental implant for tooth fixation||Titanium, Ti–Al–V alloy, stainless steel, polyethylene
Titanium, alumina, calcium phosphate
|Cardiovascular system||Blood vessel prosthesis||Dacron, Teflon, polyurethane,polyglactin 910|
|Heart valve||Reprocessed tissue, stainless steel, carbon|
|Catheter||Silicone rubber, Teflon,polyurethane|
|Skin repair template||Silicone–collagen composite|
|Artificial kidney(hemodialyzer)||Cellulose, polyacrylonitrile|
|Heart–lung machine||Silicone rubber|
|Senses||Cochlear replacement||Platinum electrodes|
|Intraocular lens||Poly(methyl methacrylate), silicone rubber, hydrogel|
|Contact lens||Silicone-acrylate, hydrogel|
|Corneal bandage||Collagen, hydrogel|
Requirements for Biomaterials
Table 3. Biological Tissue:Mechanical Properties
|Tissue||Modulus(GPa)||Tensile Strength(MPa)||Strain at Break(%)|
|Cortical bone(longitudinal direction)||17.7||133||1-3|
|Cortical bone(transverse direction)||12.8||52||1-3|
|Tissue||Modulus(MPa)||Tensile Strength(MPa)||Strain at Break(%)|
Table 2.How to measure mechanical properties of engineering biomaterials 
According to Nancy J. Stark,there are commonly three stories in which manufacturers call on CDG for biocompatibility: a) FDA has brought up questions about the safety tests you performed, b) you can decide whether you need sensitization, genotoxicity, or carcinogenicity tests, or not, c) you have a new device and don't have a clue as to what tests to do. Can an expert opinion help?
List of the standards in the 10993 series for biocompatibility evaluation
- ISO 10993-1:2009 Biological evaluation of medical devices Part 1: Evaluation and testing in the risk management process
- ISO 10993-2:2006 Biological evaluation of medical devices Part 2: Animal welfare requirements
- ISO 10993-3:2014 Biological evaluation of medical devices Part 3: Tests for genotoxicity, carcinogenicity and reproductive toxicity
- ISO 10993-4:2002/Amd 1:2006 Biological evaluation of medical devices Part 4: Selection of tests for interactions with blood
- ISO 10993-5:2009 Biological evaluation of medical devices Part 5: Tests for in vitro cytotoxicity
- ISO 10993-6:2007 Biological evaluation of medical devices Part 6: Tests for local effects after implantation
- ISO 10993-7:2008 Biological evaluation of medical devices Part 7: Ethylene oxide sterilization residuals
- ISO 10993-8:2001 Biological evaluation of medical devices Part 8: Selection of reference materials (withdrawn)
- ISO 10993-9:1999 Biological evaluation of medical devices Part 9: Framework for identification and quantification of potential degradation products
- ISO 10993-10:2010 Biological evaluation of medical devices Part 10: Tests for irritation and delayed-type hypersensitivity
- ISO 10993-11:2006 Biological evaluation of medical devices Part 11: Tests for systemic toxicity
- ISO 10993-12:2012 Biological evaluation of medical devices Part 12: Sample preparation and reference materials (available in English only)
- ISO 10993-13:1998 Biological evaluation of medical devices Part 13: Identification and quantification of degradation products from polymeric medical devices
- ISO 10993-14:2001 Biological evaluation of medical devices Part 14: Identification and quantification of degradation products from ceramics
- ISO 10993-15:2000 Biological evaluation of medical devices Part 15: Identification and quantification of degradation products from metals and alloys
- ISO 10993-16:1997 Biological evaluation of medical devices Part 16: Toxicokinetic study design for degradation products and leachables
- ISO 10993-17:2002 Biological evaluation of medical devices Part 17: Establishment of allowable limits for leachable substances
- ISO 10993-18:2005 Biological evaluation of medical devices Part 18: Chemical characterization of materials
- ISO/TS 10993-19:2006 Biological evaluation of medical devices Part 19: Physico-chemical, morphological and topographical characterization of materials
TABLE 5. Ethical Concerns Relevant to Biomaterials Science
|Is the use of animals justified? Specifically, is the experiment well designed and important so that the data obtained will justify the suffering and
sacrifice of the life of a living creature?
|How should research using humans be conducted to minimize risk to the patient and offer a reasonable risk-to-benefit ratio? How can we best ensure informed consent?|
|Companies fund much biomaterials research and own proprietary biomaterials. How can the needs of the patient be best balanced with the financial goals of a company? Consider that someone must manufacture devices—these would not be available if a company did not choose to manufacture them.|
|Since researchers often stand to benefit financially from a successful biomedical device and sometimes even have devices named after them, how can investigator bias be minimized in biomaterials research?|
|For life-sustaining devices, what is the trade-off between sustaining life and the quality of life with the device for the patient? Should the patient be permitted to “pull the plug” if the quality of life is not satisfactory?|
|With so many unanswered questions about the basic science of biomaterials, do government regulatory agencies have sufficient information to define adequate tests for materials and devices and to properly regulate biomaterials?|
|Should the government or other “third-party payors” of medical costs pay for the health care of patients receiving devices that have not yet been
formally approved for general use by the FDA and other regulatory bodies?
|Should the CEO of a successful multimillion dollar company that is the sole manufacturer a polymer material (that is a minor but crucial
component of the sewing ring of nearly all heart valves) yield to the stockholders’ demands that he/she terminate the sale of this material because of litigation concerning one model of heart valve with a large cohort of failures? The company sells 32 pounds of this material annually, yielding revenue of approximately $40,000?
|Should an orthopedic appliance company manufacture two models of hip joint prostheses: one with an expected “lifetime” of 20 years (for young,
active recipients) and another that costs one-fourth as much with an expected lifetime of 7 years (for elderly individuals), with the goal of saving resources so that more individuals can receive the appropriate care?
Classes of Biomaterials
Metals as biomaterials
Ceramics as biomaterials
Table Biomedical Applications of Bioceramics
|Artificial total hip, knee,shoulder, elbow, wrist||Reconstruct arthritic or fractured joints||High-density alumina, metal bioglass coatings|
|Bone plates, screws, wires||Repair fractures||Bioglass-metal fiber composite,Polysulfone-carbon fiber composite|
|Intramedullary nails||Align fractures||Bioglass-metal fiber composite,Polysulfone-carbon fiber composite|
from T. V. Thamaraiselvi et al(2004)
Polymers as biomaterials
Composite as biomaterials
Biodegradable Polymers as Biomaterials
Generally, biodegradable polymers is composed of ester, amide, or ether bonds. These biodegradable polymers can be categorized into two groups based on their structure and synthesis. One of these groups is agro-polymers, or those derived from biomass. The other consists of biopolyesters, derived from microorganisms or synthetically made from either naturally or synthetic monomers.
Biopolyesters as Biomaterials
Agro-polymers as Biomaterials
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A Brief review: Biomaterials and their application, Amogh Tathe et al,Int J Pharm Pharm Sci, Vol 2, Suppl 4, 1923
Biomaterials by Joon B. Park, Roderic S. Lakes