Introduction to Biomaterials Flashcards
Define Biomaterial
- A biomaterial is a nonviable material used in a medical device, intended to interact with biological systems
- Defined by their application NOT chemical make-up.
What are physical characteristics of Biomaterials?
- Hard Materials
- Soft Materials
What are Chemical requirements of Biomaterials?
- Must NOT react with any tissue in the body
- Must be non-toxic to the body
- Long-term replacement must not be biodegradable
What do ALL biomaterials have in common?
- They must have intimate contact with patient’s tissue or body fluid
- Providing a real physical interface
What are polymers?
High molecular weight molecule made up of a small repeat unit (monomer)
What are monomers?
Low molecular weight compound that can be connected together to give a polymer
What are oligomers?
Short polymer chain
What are Copolymers
- Polymer made up of 2 or more monomers
- Ex: Random copolymer: A-A-B-B-A-B-B-A-A-A-A-B-B-A-B-A
- Ex.) Alternating copolymer: A-B-A-B-A-B
- Ex.) Block copolymer: A-A-A-A-A-A-B-B-B-B-B
What is the most produced plastic in the world?
Polyethylene (PE)
What are the Top Plastic Products?
- Packaging: 33%
- Consumer Products: 20%
- Construction: 17%
- Medical: 10%
What was the FIRST thermoplastic?
- Celluloid (Nitric acid+sulfuric acid+camphor)
What was the FIRST synthetic plastic?
Bakelite (phenol formaldehyde resin)
What was the FIRST petroleum plastic?
Nylon (polyamides)
What is Teflon?
Synthetic fluoropolymer of tetrafluoroethylene
What are some concerns with plastic products?
- Polyvinyl Chloride: dioxin
- Plasticized PVC: food container
- Phthalate, DEHP, BPA, DES, PET: Environmental hormones associated with asthma, diabetes, bipolar, infertilities, developmental defects
What constitutes Biocompatibility?
- Good biocompatibility is achieved when the material exists within a living body without adversely or significantly affecting it or being affected by it.
- The material should have adequate mechanical strength, chemical and physical properties
- Must be compatible with body tissues mechanically, chemically as well as pharmacologically
What are the 4 types of Synthetic Biomaterials?
- Polymers
- Ceramics
- Semiconductor Materials
- Metals
What are examples of Polymers?
- Drug Delivery Devices
- Skin/Cartilage
- Ocular implants
What are examples of Ceramics?
- Bone replacement
- Heart valves
- Dental Implants
What are examples of Semiconductor Materials?
- Biosensors
- Implantable Microelectrodes
What are examples of Metals?
- Orthopedic screws/fixation
- Dental Implants
I don’t think this is important, but there is 1st, 2nd, and 3rd generations of implants
- 1st: successes were accidental
- 2nd: built on 1st gen experiences. Used common/borrowed materials, collab of physicians and engineers
- 3rd: under development, bioengineered material, few examples on market
Success and Failures of Heart Valves
- Once diagnosed with diseased aortic heart valve, patient has 50% chance of dying within 3 years
- Surgical replacement of the diseased valve leads to an expected survival of 10 years in 70% of the cases
- Patients whose longevity and quality of life have clearly been enhanced, approx. 60% will suffer a serious heart valve-related complication within 10 years after the operation
- Other problems include: degeneration of Tissue. Mechanical Failure (crush RBCs and cause clots), Postoperative infection, and Induction of Blood clots
What does Osseointegration?
Capability of bonding to bone such as a Dental Implant made of titanium
What does Bioinert mean?
No reaction with tissue and no rejection/allergic reactions
What material is described in the slides for Dental implants?
Pure titanium screw-shaped cylinders that act as roots for crowns and bridges, or as supports for dentures
What is an important/special requirement for Dental Implants?
The ability to form a tight seal against bacterial invasion where the implant transverses the gingival (gum)
What is the MOST COMMON medical practice using biomaterials? Describe them!
- Joint Replacement
- Corrosion resistant high-strength metal alloys
- Very high molecular weight polymers
- Thermoset plastics
Describe Hip Replacements
- Subject to HIGH mechanical stress and undergoes considerable abuse
- Fabricated by specific high-strength alloy, ceramics, composites, and ultrahigh molecular weight polyethylene
- After 10-15 years, implant may loosen
What are Intraocular Lenses made of?
- Made of Polymer Modified Masterseal (PMM), silicone elastomer, and other material
- Typically, due to cataracts and cloudy vision
Describe Vascular Grafts
- Must be flexible
- Designed with open porous structure
- Often recognized by body as foreign
- Achieve and maintain homeostasis
- Biostable
- High Fatigue Resistance
- Permeable
What are the 3 main types of vascular grafts permeability?
- Braids
- Knits
- Weaves
What is Lithography?
- Most complicated, expensive, and critical process of micro/nano scale manufacturing
- Transforms complex circuit diagrams into pattern which are define on the wafer in a succession to exposure and processing steps to form a number of superimposed layers of insulator, conductor, and semiconductors materials
Successes and Failures of Lithography
- No manmade construct is perfect
- All manufactured devices have a failure rate
- Also, all humans are different with differing genetics, gender, body chemistries, living environment, and degrees of physical activity.
What is Soft Lithography?
- Greek for “to write in stone”
- Called “soft” because it is typically used on elastomeric materials such as PDMS (polydimethylsiloxane)
- Uses photolithography to make a mold for PDMS, which gets permanently bonded onto glass to make a microfluidic device
- Fast and cheap prototyping method
Compare the 2 Types of Lithography
- Photolithography: Making a mold on a silicon wafer using UV light to etch a design
- Soft Lithography: Using the mold to make a chip from PDMS polymer
What is PDMS?
- stiffness and density can be controlled via adjustment of curing agent
- Presence of an inorganic siloxane backbone and organic methyl groups attached to silicon
- Very LOW glass transition temperatures and hence fluids at room temp.
- Easily converted to solid elastomers by cross-linking
- Mostly bioinert and Hydrophobic surface
Benefits of PDMS
- Optical: transparent for eye lenses
- Mechanical: elastomeric and conform to surface when not polymerized + reversible deformation
- Electrical: Insulating, breakdown, and voltage. Intentional breakdown to open connections
- Thermal: Can be used to insulate heated solutions
The light sensitive material utilized in the photolithography process is
Photoresist
Look at slides for Lithography Process!
Look at slides! pg 12
Advantages/ Disadvantages of PDMS
Advantages:
- Low cost
- Fast Production
- Easily accessible
- Does well with small details
Disadvantages
- PDMS is a soft structure (limited mechanical strength)
- PDMS has a high thermal expansion ( Inc. Heat or Inc. Friction = EXPAND!)
What is Toxicology?
- Deals with substances that migrate out of biomaterials
- Ex.) For polymers, many low-molecular-weight “leachables” exhibit some level of physiologic activity and cell toxicity
- Note: Biomaterial should not give off anything from its mass unless it is specifically designed to do so.
What else can be said about Biocompatibility besides its OG definition?
- We do NOT have a precise definition or accurate measurements of biocompatibility
- Defined in terms of performance or success at a specific task
- For instance, what environment are you considering? Lenses should be transparent and flexible for instance.
- Also, everyone’s immune system is different
Describe Healing and the Foreign Body Reaction
- Injury to tissue will stimulate the well define inflammatory reaction sequence that lead to healing
- When a foreign body is involved that is the “Foreign Body Reaction”
- Normal body response varies in intensity and duration depending on anatomical sites involved
What are the 3 categories for the Mechanical and Performance Requirements?
- Mechanical Performance
- Mechanical durability
- Physical Properties (functional)
