Tentafrågor 2023

Question 1

What are the five main types of chemical bonds? Give examples of one compund for each bond.

Answer 1

Ionic-NaCl, covalent-CO2, Metallic-iron, van der waal-methane, hydrogen-water

Question 2

Describe the three types of cartilage, their composition and where you find them in the body

Answer 2

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

Question 3

Principal functions of ECM

Answer 3

Mechanical support for cells, control of cell growth, determination of cell orientation, scaffold for tissue renewal

Question 4

Main structural components of bone tissue

Answer 4

Osteoblasts(creation), osteocytes and osteoclasts (reabsorption of bone tissue)

Question 5

Mechanical properties you obtain using a traditional tensile test by drawing a stress strain curve for a ductile material

Answer 5

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)

Question 6

Define biocompatibility

Answer 6

The ability of a material to perform with an appropriate host response in a specific application

Question 7

Describe a technique that is used to determine a material’s Toughness

Answer 7

Charpy test. Pendulum swing into the material and see how much energy is absorbed

Question 8

Draw a droplet on a surface and label the different interfaces and the contact angle. Write youngs eq.

Answer 8

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)

Question 9

Source of illumination in ESCA/XPS? What is detected?

Answer 9

Fires photons. Measures binding energies of core electrons.

Question 10

Two main modes AFM can be operated in? What information can they provide?

Answer 10

Static mode and dynamic mode.

They provide a mapping of a surface on the atomic scale

Question 11

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

Answer 11

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

Question 12

Describe why titanium does not corrode to a high extent.

Answer 12

When in contact with air and water, a dense oxide layer is formed on surface which provides chemical protection

Question 13

What is the problem associated with stress shielding?

Answer 13

Bone density decreases as bone tissue reabsorbs after an implant takes on a higher share of load than the bone originally did.

Question 14

What happens to bacteria when adsorbing onto an implant and why does such bacteria form hard to treat infections?

Answer 14

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.

Question 15

What material properties affect bacterial attachement?

Answer 15

Charge, roughness, hydroaffinity, mechanical properties. Superhydrophobic and superhydrophillic surfaces can both prevent biofilm formation

Question 16

Give two strategies for the development of an implant surface to aviod biomaterial associated infection

Answer 16

Tissue integrating surface (binds to tissue before bacteria), none adhesive surface, drug releasing surface, contact-killing surfaces

Question 17

Describe the differences between a medical device and a drug, and how these are regulated differently.

Answer 17

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.

Question 18

What is a 510(k)

Answer 18

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.

Question 19

What are the roles of a notified body?

Answer 19

Surveillance and regulation of medical devices. Advising on classification of devices.

Question 20

Define ceramics and give two examples of ceramics used as biomaterials and in what applications they are used.

Answer 20

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.

Question 21

Define nearly inert, boiactive and bioresorbable ceramics and give and example of each category.

Answer 21

Nearly inert= Encapsulated by tissue. Zirconia, Alumina, Titania

Bioactive=biological interfacial bonding. Bioglass, Hydroxyapatite

Resorbable=Replaced by tissue. TCP, CaCO3

Question 22

What is sintering of ceramics?

Answer 22

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.

Question 23

Give the three commonly used naturally derived polymers for making hydrogels for bio applications. Also give the origin for each polymer.

Answer 23

Chitosan, Alginate, Hyaluronic acid
Chitosan, found in crustacean creatures. Alginate found in seaweed. Hyaluronic acid can be found in rooster combs.

Question 24

In what different ways can you crosslink hydrogels?

Answer 24

Covalent crosslink (chemical), physically crosslink(hydrophbic folding, hydrogen bonds, van der waal), entangle(stiffness of polymer).

Question 25

How are the material properties of a gel affected by the corsslinking density?

Answer 25

The higher the density, higher modulus & stiffness and lower permeability/diffusitivity & water content/swelling

Question 26

Give the chemical formula for poly(vinyl chloride)(PVC) and Polydimethylsilocane PDMS.

Answer 26

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.

Question 27

Define the glass transition temperature (T_g)and the crystalline melting temperature (T_m)

Answer 27

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

Question 28

Give the two main mechanisms for degradation in vivo for degradable polymers.

Answer 28

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

Question 29

What are the three major fabric forming processes for textiles?

Answer 29

Weaving, Knitting and non-woven

Question 30

What are smart textiles?

Answer 30

Example: IQ-sock to prevent VTE. Smart textiles uses electrodes to measure things like ECG, EEG, gait analysis and pulse continuously

Question 31

Describe the three mainly used sterillisation methods, include both advantages and disadvantages.

Answer 31

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