Biomaterials and Devices Flashcards
What is a biomaterial?
Biomaterials are synthetic materials that are used to make devices to replace a part or a function of the body in a safe, reliable, economic and physiologically acceptable manner. They replace part of a living system or function in intimate contact with living tissue. Hearing aids and prosthetic limbs are not biomaterials as the skin is a barrier
What is a Biological material?
Biological materials are natural and formed or found within a biological environment. They entirely self-assemble and form at near ambient temperatures
Describe the case study - Alternative packaging for mushrooms
Non-polymer biodegradable alternate for single use plastics.
Particular properties of agricultural waste materials/co-products can be exploited. Mushroom materials such as damaged caps and stalks can be blended with Kraft pulp to produce mushroom punnets
- Waste materials (mushrooms and kraft pulp from end-of-life corrugated cardboard scrap) are juiced into pomace
- Pomace and CCF slurry are combined into MF/CCF slurry, heated at 85 degrees per minute
- This is vacuum filtered on punnet-shaped mesh moulds
- Wet moulded punnet is transferred to drying oven at 45 degrees
Describe the case study - Virus Velcro Masks
Electrospun fibres are proven technology compatible with large scale manufacturing. Entanglement is not needed for effective filtration due to the electrostatic attraction, and the material is biodegradable and sustainable in origin.
A face-covering is worn voluntarily, so there is no need to demonstrate efficacy but it must be comfortable.
PPE must have proven efficacy, as the user is obliged to use it.
Fucoidan as a virus adherent was originally proposed, as it improves filter efficiency without lowering permeability (allowing breath passage)
Describe a Hard-on-Soft Implant as a hip replacement
Early implants were made of ultra high molecular weight polyethylene - densely packed linear PE chains increased mechanical properties but decreased fracture toughness and ductility. Wear of cup occurs
Increasing cross-linking in PE reduces wear, thus components have a longer lifetime. Ceramics can be used for the head
Describe a Hard-on-Hard implant as a hip replacement
Cobalt chrome - wear produces particles which can have adverse effects on the body, especially for patients with poor kidney function. ball and cup must exactly fit each other or else chipping will occur
Some studies show metal-on-metal implants can cause high levels of metal ions in the bloodstream
Describe the parts of an Orthopaedic Hip replacement
Two main parts - femoral component and acetabular cup
The femoral component is inserted into the shaft of the femur (prepared by hollowing out a section) and replaces the ball of the ball-and-socket joint. The stem needs to match the strength and toughness of the natural bone as closely as possible. The head must fit exactly in the socket with a low coefficient of friction
The acetabular cup replaces the socket, it sits in the pelvis and replaces the worn cartilage. Must have a low wear rate and minimise wear of the femoral head component
Describe the properties Vascular Stents need to have
Usually made of metallic or polymeric wires that can be placed in the blood vessel as an internal scaffold to maintain the internal diameter (lumen). Primary treatment option of coronary artery disease
Need to be compressed and expanded when placed. Has to be flexible enough to cope with variable pressures but strong enough to keep the artery open. occasionally drug loaded to prevent re-stenosis
What are some Material requirements of implants that need to be considered?
Biological conditions - materials must operate for many years at about 37 degrees in a moist environment
Response - implant materials have to minimise adverse reactions from the immune system. Higher levels of certain metals in the bloodstream can lead to various issues
Materials properties - materials must replace natural tissue and perform the same functions.
Cost - suitable balance between performance and cost
What were the legislative drivers for the case study - Alternative packaging for Mushrooms?
- Introduction of plastic packaging tax from April 2022. UK manufacturers, plastic importers, costumers and consumers will be affected.
- The aim of the tax is to provide an incentive to use recycled plastics, lowering plastic waste in landfill or incineration
- The single-use plastics (SUP) directive. All EU member states and Norway are enforcing these guidelines.
- Aims to prevent and reduce impact of plastic pollution in aquatic environments and human health, and promote transition to circular economy and sustainable business models.
What is Electrospinning and what are the requirements for it?
Produces a strand from a polymer solution or a melt, and rapidly draws it out into a nanoscale fibre.
A 1m^2 mat of electrospun fibre has a surface area of about 40m^2, and may be composed of a single fibre
Requires high voltage source, spinnable materials and ideally an understanding of the theoretical principles of the process
What is biomimicry and why is it an important concept for the Virus Velcro Masks?
Chemical mimicry of mucosal surfaces in the human respiratory tract is used to attract and entrap the virus on the fibres. This means physical entrapment via a mesh of fibres with smaller pore sizes than the particle is not required
