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MAT308 > Exam > Flashcards

Exam Flashcards

1
Q

Name a type of collagen used for sutures

Positives and negatives

A

Catgut Sutures- sheep or goat intestine which is cleaned, split into ribbons, crossed linked and then polished
These are absoorbable and inexpensive
They do have weak points and can fray

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2
Q

Advantages of collagen (11)

A

Lots available
Easily purified
non antigenic so no antigen reaction stimulated
Bidegradable
Bioresorbable
Biocompatable
Non-toxic
Synergic (cooperative) with bioactive componenent
Haemostatic so promotes good coagulation
Easily modified to produce materials with dfferent properties
Compatable with synthetic polymers

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3
Q

Disadvantages of collagen (6)

A

Pure type 1 collagen is expensive
The source of the collagen impacts the amount of regulation it has to undergo
Processing produces variability in the collagen
It is hydrophilic which leads to swelling and more rapid degredation
Complex handling properties
Variability is enzymatic degredation rate

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4
Q

What is denatured collagen

A

Gelatine

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5
Q

How do you make collagen into geletin

What is its structure now

A

Denatured
Using Heat or pH
No triple helixes- it is randomly coiled and breaks down easily in the body
The tangled fibres absorb water and create a gel

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6
Q

Polysacharide based biological materials- main source?

A

Chickens , though other sources include bovine vitreous fluids, sharks and bacterial fermentation

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7
Q

GAGs meaning

What are they?

A

Glucos- amino- glycans

Repeating disaccharide units that attach to a core protein which makes proteoglycans

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8
Q

Largest GAG

What is it good for

A

The largest is hyaluronic acid- this attracts water which is good at making gels. These can be esterified and cross linked to make it more viscous for sponges and fibres
These are mostly used as injections for joint lubrication/ synovial fluid, improving bladder linings or skin injections
When made into a film they can be used for eye surgery
Can also be made into scaffolds

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9
Q

Alginate

A

This is a polysacharide co polymer
Extracted from SeaWeed. The ratio between Mannuronic acid guluronic acid depends on the type of seaweed
This is biocompatable but we are not yet sure if it is biodegradable
Currently used for wound dressings as has good absorbtion but stays moist and doesnt inhibit contraction. However it can dry out the wound so there is need for an additional dressing

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10
Q

Chitosan
Source?
Treatment?
Forms?

A

Chitin is a polysaccharide found in crustacean exoskeletons
Chitosan is deacylated (removing the acyl group) chitin . Determines when >50% N-glucosamine units are deacylated
Soluble below pH6–> here is forms a gel which is one of the preferred materials to work with
Films and fibres can be formed by cross linking

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11
Q

Stages of extracting Chitosan

A

Prawns–> Decalcification –> Deproteination –> Decolourisation( now chitin) —> Deacetylation (now Chitonsan)

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12
Q

Applications of Chitosan (4)

A

Contact lenses
Drug delivery
Good wound healing, absorption and antibacterial properties
Bandages made from electrospinning

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13
Q

Bone as a biological material
Source?
Treatment?

A

Animal (Bovine spongy bone) bone is defatted and deproteinated using sodium hydroxide, hydrazine and heat

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14
Q

Coral as a biological material
Is it good?
Uses?

A

Has a high dissolution rate so not normally a good biomaterial but can be converted into hydroxyapaptite using a hydothermal process. The properties can be further improved by coating. This has an interconnected pourous structure as similar to cortical bone which leaves room for growth. This offers a strong natural foundation for new bone ingrowth. When healed the bone and the coral have similar strength.
There is no risk of implant rejection

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15
Q

PHAs- PolyHydrocyalkanoates

A

Polymers synthesised by bacteria
Can create a very diverse set of materials–> the most simple of which is PHB
Long degredation times
Good biocompatability

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16
Q

Commercial examples of Bone used as a biomaterial (2)

A

Endonbon- Osteoconductive hydroxyapatite ceramic which is used as a bone graph substitute. Used as a perminant filling and reconstuction material for bone defects in trauma surgery and orthapeadics. Used after fractures and benign bone tumors
Bio-Oss - Can osseointegrate wil newly formed bone.

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17
Q

Uses of PHAs

A

Sutures
Artificial skin
Drug delivery
Implant Materials

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18
Q

What is the definition of Silk?

A

Structural protein spun into fibres for use outside the body. Has to deliver its functions in all sorts of environments so is often hardeir thn other biological materials

19
Q

What materials are silks made from

A

High proportions of glycine and alanine

20
Q

What happens when silk gets wet

A

Changes properties, becomes more tense

21
Q

What is the structure of silk like and how is it influenced

A

They are a multiscale hierarchical non structured biopolymers
They’re Hard:Soft ratio also known as the order:disorder ratio is the secondary structure and is determined by the processing

22
Q

what defines the mechanical properties of silk

A

The environment and spinning conditions influence the silk fibres mechanical properties

23
Q

Usually how long at silk and what does this make difficult

A

100kDa
It is difficult to determine their full length sequence due to the high degree of repetition of the internal structures. This makes it hard to find the centre of the chain.

24
Q

What type of polymer is silk

what elements

A

Bio Polymer

Protein hydration and hydrogen bonding is key

25
Q

Best model for silk structure

A

Beads on a string model
We don’t know if it is a single protein or a mix of proteins as we have not been able to follow it from one end to another.

26
Q

What does the fact that silk is a polyamide mean for its properties

A

It means it can coordinate with other chains meaning the chaisn can interact and create larger scale structures

27
Q

Name the components of silks hierarchal structures

A

nanofibril, microfibril, core, skin

28
Q

The environment and spinning conditions influence the silk made. what does this mean for the promise of artificial silk

A

If the base material could be harnessed, many different materials could be made for many different uses

29
Q

What is flow induced crystalisation

A

The silk is made by applying energy
This changes the state of the material as the build up of energy causes the material to heat up which in turn strips the water from the protein which changes its conformation
SILK HAS EVOLVED TO BE DENATURED

30
Q

Rheology

A

The study of flow and deformation of matter

31
Q

Strongets fibre in nature

A

Golden orb weaving spider

32
Q

Commercial silk

A

Produced by chinese silk worms

33
Q

What are the silk gold standards and what are they used for ?
What is compared ?

A

These are parallels between polymers and natural materials that are used as a gold standard for design criteria comparison

  • Shear sensitivity
  • flow properties are convergent
    -akin to polymer melts
    Artificial silks that have been made are different in kind not in degree, this may be due to artificial spinning
34
Q

Applications of silk: Textiles

A

thread created by spinning together multiple fibres

35
Q

Applications of silk: Medical

A

Sutures and implants- implants made of hardened fibre can replace diseased sections of clogged arteries

36
Q

Applications of silk: Sponges and mats

A

Can be used as scaffolds for bone implants

37
Q

Applications of silk: Films

A

These can contain silicone circuits which can lie beneath the skins surface and measure oxygen levels

38
Q

Applications of silk: Fibres

A

silk can be drawn into fibres and used as optical wave guides which can be used to shine light into the body

39
Q

Applications of silk: Coating and gels

A

Flexible electrodes can be printed on silk substrates and put on the cortex of the brain- can be used to imput electrical signals.

40
Q

Three real life applications of silk and what they do

A

Neurotex: peripheral nerve repair
Oxford biomaterials: Vascular repair
Fibrofix by orthodox: orthopedic implants

41
Q

Neurotex: peripheral nerve repair

A

A resorbable and biocompatable nerve conduit

42
Q

Oxford biomaterials: Vascular repair

A

vascular graft for heamodyalysis access which has improved integration

43
Q

Fibrofix by orthodox: orthopedic implants

A

Treatment for menisci and cartilage damage in the knee- matches the performance of the natural material

MAT308 (7 decks)

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