Tentafrågor 2023 Flashcards
What are the five main types of chemical bonds? Give examples of one compund for each bond.
Ionic-NaCl, covalent-CO2, Metallic-iron, van der waal-methane, hydrogen-water
Describe the three types of cartilage, their composition and where you find them in the body
Hyaline, elastic and fibrous
Hyaline - Smooth and shiny. Found in joints, ribs, larynx, trachea
Elastic - Bendable and flexible. Found in outer ear, epiglottis
Fibrous - A blend of hyaline cartilage and dense fibrous tissue. Found where tendons and ligaments attach to the bone in the knww, hip shoulder
Principal functions of ECM
Mechanical support for cells, control of cell growth, determination of cell orientation, scaffold for tissue renewal
Main structural components of bone tissue
Osteoblasts(creation), osteocytes and osteoclasts (reabsorption of bone tissue)
Mechanical properties you obtain using a traditional tensile test by drawing a stress strain curve for a ductile material
1 - linear phase=Youngs modulus (E) is the slope, reversible deformation
2 - End of linear phase=Irreversible deformation after this point
3 - Ultimate tensile strength=Top of graph, maximum stress a material can withstand
4 - Fracture point= Lower stress level due to reduced cross-sectional area due to deformation
The regions under the curve give the resilience ( 0-2, Elastic energy storage), and toughness (0-4, Breaking energy)
Define biocompatibility
The ability of a material to perform with an appropriate host response in a specific application
Describe a technique that is used to determine a material’s Toughness
Charpy test. Pendulum swing into the material and see how much energy is absorbed
Draw a droplet on a surface and label the different interfaces and the contact angle. Write youngs eq.
Y_(SV)= Interfacial tension between surface and air
Y_(SL)=Interfacial tension between the surface and the liquid
Y_(LV)=Surface tension of liquid
Theta=contact angle
Young: Y_(SV)=Y_(SL)+Y_(LV)*cos(theta)
Source of illumination in ESCA/XPS? What is detected?
Fires photons. Measures binding energies of core electrons.
Two main modes AFM can be operated in? What information can they provide?
Static mode and dynamic mode.
They provide a mapping of a surface on the atomic scale
Three most often used metals in load bearing implants are titanium, stainless steel, and cobalt chromium. Describe good and bad properties and what implants each metal is used in
Titanium: + High strength, corrosion resistant, biocompatible. - Poor friction properties. Bone implants, heartvalves etc.
Stainless steel: +Tough, permits plastic deformation.-Moderate corrosion resistance. Bone implants, dental prosthesis
Cobalt-chromium:+ High strength, high hardness.- Prone to fatigue. Heart valves, dental prosthesis
Describe why titanium does not corrode to a high extent.
When in contact with air and water, a dense oxide layer is formed on surface which provides chemical protection
What is the problem associated with stress shielding?
Bone density decreases as bone tissue reabsorbs after an implant takes on a higher share of load than the bone originally did.
What happens to bacteria when adsorbing onto an implant and why does such bacteria form hard to treat infections?
They form communities and produce biofilms or extra cellular polymeric substance (EPS) matrices. Withstands 1000x concentration of antibiotics than “free” bacteria. The bacterial cell division halts and since that is what many antibiotics target the’re rendered useless.
What material properties affect bacterial attachement?
Charge, roughness, hydroaffinity, mechanical properties. Superhydrophobic and superhydrophillic surfaces can both prevent biofilm formation
Give two strategies for the development of an implant surface to aviod biomaterial associated infection
Tissue integrating surface (binds to tissue before bacteria), none adhesive surface, drug releasing surface, contact-killing surfaces
Describe the differences between a medical device and a drug, and how these are regulated differently.
Medical device=Items or instruments used for medical purposes. Pacemaker
Drug=Substances or compunds used to treat, prevent or diagnose a disease. Vaccine.
Devices are put in risk categories (Class I, II, III). Drugs are put through rigorous testing for approval.
What is a 510(k)
Pre market notification needed for most class II devices. Compares a new device with a similar already existing device. If the company can prove they are similar enough, some of the saftey tests can be skipped.
What are the roles of a notified body?
Surveillance and regulation of medical devices. Advising on classification of devices.
Define ceramics and give two examples of ceramics used as biomaterials and in what applications they are used.
Ceramics are inorganic non-metallic materials. Nearly inert aluminum oxide is used as knee & hip joints. Bioactive hydroxyaoatite is used as coating and non loaded implants.
Define nearly inert, boiactive and bioresorbable ceramics and give and example of each category.
Nearly inert= Encapsulated by tissue. Zirconia, Alumina, Titania
Bioactive=biological interfacial bonding. Bioglass, Hydroxyapatite
Resorbable=Replaced by tissue. TCP, CaCO3
What is sintering of ceramics?
All the gaps of air in the material is taken away using high temperatures and vacuum, and your left with a solid block of ceramics with very little gaps.
Give the three commonly used naturally derived polymers for making hydrogels for bio applications. Also give the origin for each polymer.
Chitosan, Alginate, Hyaluronic acid
Chitosan, found in crustacean creatures. Alginate found in seaweed. Hyaluronic acid can be found in rooster combs.
In what different ways can you crosslink hydrogels?
Covalent crosslink (chemical), physically crosslink(hydrophbic folding, hydrogen bonds, van der waal), entangle(stiffness of polymer).
How are the material properties of a gel affected by the corsslinking density?
The higher the density, higher modulus & stiffness and lower permeability/diffusitivity & water content/swelling
Give the chemical formula for poly(vinyl chloride)(PVC) and Polydimethylsilocane PDMS.
PVC=(C2H3Cl)_n, PDMS=(CH3SiO)_n
PVC can be used in construction materials, medical devices. Durable and low cost.
PDMS can be used for implants and skincare products. Biocompatible and transparent.
Define the glass transition temperature (T_g)and the crystalline melting temperature (T_m)
T_g= Temperature when amorphous regions of a polymer turn from a glassy & brittle solid to a viscous & leathery liquid
T_m= Temperature where crystalline regions in a polymer transitions from a solid to a viscous liquid
Give the two main mechanisms for degradation in vivo for degradable polymers.
Hydrolysis and Enzymatic. Enzymatic activity may vary widely! Water content is more or less constant –> Hydrolytic cleavage is more predictable and preferred in medical decvices
What are the three major fabric forming processes for textiles?
Weaving, Knitting and non-woven
What are smart textiles?
Example: IQ-sock to prevent VTE. Smart textiles uses electrodes to measure things like ECG, EEG, gait analysis and pulse continuously
Describe the three mainly used sterillisation methods, include both advantages and disadvantages.
Radiation, Ethylene oxide, Thermal
Radiation: Gamma, e-beam, x-ray.+Temperature/chemical independent, safe, quick and effective. Could potentially alter the structure of polymers negatively
Ethylene oxide: Sprayed on the material. Kills microorganisms. Otherwise it sucks. toxic, carcinous, flammable.
Thermal: Steam the materials. Quite quick. Must only be used on thermostable materials and packaging
