Công nghệ vật liệu trong y sinh học biom aterials chapter 2 phần 2 2

Chap.2. –

2.2. Silicone

1. Introduction to silicone
- 1824: tetrachlorosilane (SiCl4); 1863: tetraethylsilane; 1871:diethyldiethoxysilane
1901- 1931:foundation of organosilicon chemistry
1940s: became commercial
- Basic repeating units: siloxane; PDMS (polydimethylsiloxane): most common silicone

.c
om

R can be different

- Have unique properties, possible use as fluids, emulsions, compounds, resins, elastomer
- Widely used in a lot of application
. In aerospace industry (low- and high temperature performance)
. In electronic field: Electrical insulator, semi conductor

ng

. In construction: Sealants, adhesives, water proof coatings (due to long-term durability)

co

. Widely used in personal care, pharmaceutical, medical device application (excellent biocompatibility)

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

1

du
o

Chap.2. –

2.2. Sillicone

cu

u

Silicone Chemistry and nomenclature

M: Si connected with 1 oxygen atom
D: Si connected with 2 oxygen atoms
T: Si connected with 3 oxygen atoms
Q: Si connected with 3 oxygen atoms

Example: Trimethylsiloxy: most common

MDnM

2

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.2. Sillicone

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

3

du
o

Chap.2. –

2.2. Sillicone

2. Synthesis

cu

u

2.1. Silicone polymer

4

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.2. Sillicone

2.2.Silicone elastomer
•Cross-linking with radicals
- For high consistency silicone rubber (extrusion or injection)
- Initiator: peroxide (radicals forming)
•Cross-linking by condensation

- Mostly for silicone caulks, sealants, silicone adhesives for medical devices
- Catalyst needed
- By products
•Cross-linking by addition

.c
om

- Catalyst: Pt or Rh metal complexes
- No by products
- For molded parts
•Elastomer filler

- To enhance the strength and modify several properties of silicone elastomer

ng

- Fillers: titanium oxide, barium sulphate, pigments, fumed silica (most favorable) but needs
surface modification (with silane)

co

- Processing:: two roll mill, twin-screw extruder, Z-blade mixer

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

5

2.2. Sillicone

cu

u

du
o

Chap.2. –

6

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.2. Sillicone

3. Some properties
- Unusual combination between high surface tension (of inorganic back bone)
with low surface tension of organic side groups:

. Biocompatible elastomer (surface tension 20-30 mN/m)
. Capable to wetting themselves
. Silicone organic copolymers can be prepared with surfactant properties (e.g.
in silicone glycol copolymer
- Have week intermolecular interactions:

.c
om

. Very low glass temperature

. Have high permeability to oxygen, nitrogen, water vapor…

co

ng

. Viscosity id less dependent on temperature than hydrocarbon

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

7

du

o

Chap.2. –

2.3. Medical Fibers and Biotextiles

Medical textiles: medical products and devices for
-Wound dressing, bandages…

u

-Biotextiles, tissue engineering scaffolds, vascular implants…
* Medical fiber can be fabricated from monofilament, multifilament, staple…

cu

* Materials for medical textiles: synthetic polymers, natural polymers, or genetically engineered polymers and
the way to choose suitable fiber configuration and materials: based on the requirements of device design and
the manner in which fiber is to be used
- Non-absorbable synthetic polymers:
. PET (polyethylene terephthalate)- (Dacron): for most large-caliber textiles vacular grafts
. PVC copolymer (Vinyon), acrylic polymers, nylon, PTFE-polytetraflourethylene (Teflon)…: for vascular
grafts since 1950s.
.Today only PTFE & PET are still used for vascular grafts (inert, flexible, resilent, durable and resistant to
biological degradation
- Absorbable polymers: PVA- poly(vinyl alcohol), PLA- poly(lactic acid), PGA-polyglycolide…: for
absorbable sutures…
- Biopolymers and modified biopolymers (natural polymers:
. Collagen, polysacharides (alginates, biomimetic polymer synthesized by generic engineering of
peptide sequences from elastin, collagen and spider silk…): for absorbent wound dressing, wound

management, scaffolds for cell cultures, surgical hemostats…
. Cotton has been commonly used for bandages, surgical sponges, drapes, and surgical apparel, and in
surgical gowns.

8

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.3. Medical Fibers and Biotextiles

co

ng

.c
om

Important Note! for most synthetic
polymers: additive (dyes, stabilizer,
antioxidants, delustrants) problems
from commercial polymers

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

9

2.3. Medical Fibers and Biotextiles

cu

u

du
o

Chap.2. –

10

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.3. Medical Fibers and Biotextiles

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

11

cu

u

du
o

Chap.2. –

12

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

13

cu

u

du
o

Chap.2. –

2.3. Medical Fibers and Biotextiles

Preparation
•Melt Spinning
•Wet spinning
•Electrospinning
Melt spinning:
-Typically used with thermoplastics
-Yarn can be further processed
- Size of spun fiber: 10 µm (multifilaments) 500 µm or more (for monofilament)

Electrospinning:
- For very fine fiber
- Use electrostatic field and high voltage (5-30 kV)
- Fiber diameter: 1 µm-100 nm

14

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.3. Medical Fibers and Biotextiles

.c

om

Chap.2. –

Wet spinning

Low-temperature process

co

ng

(related to degradation proplems)

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

15

du
o

Chap.2. –

2.3. Medical Fibers and Biotextiles

Construction

u

•Nonwovens

-Is a textile structure produced directly from fibers without the intermediate step of yarn production

cu

-Fibers: bond or interlocked together by chemical, or thermal action or by using adhesive or solvent;
oriented random or in one or more directions
•Woven fabrics:
-Textile configuration where the primary structural yarns are oriented at 90o to each other
- Plain, twill, satin weaves
-Water permeability should be controlled (50-350 ml .cm-2.min-1)
•Knits
-Made by interloping yarn in horizontal row and vertical columns of stitches
•Braids

16

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.3. Medical Fibers and Biotextiles

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

17

2.3. Medical Fibers and Biotextiles

cu

u

du
o

Chap.2. –

18

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.3. Medical Fibers and Biotextiles

co

ng

.c
om

Finishing

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

19

2.3. Medical Fibers and Biotextiles

Testing

cu

u

du
o

Chap.2. –

20

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.4. Hydrogels

Hydrogel: Polymer that can adsorb water 30% or more of its weight
- Are water-swollen, cross-linked structure
- Containing ether covalent bonds produced by simple reaction of one or more comonomers

- Containing physical cross-linked from entanglements, association bond such as hydrogen bonds or
strong Van der Waal interaction between chains
- Have received significant attention for biomedical applications
- Classification:
. Based on preparation: homopolymer hydrogels, copolymer hydrogels, multipolymer hydrogels,
interpenetrating polymeric hydrogels

.c
om

. Based on ionic charge: neutral, anionic, cationic or ampholytic hydrogels
. Based on physical structural feature: amorphous (chain are arranged randomly), semicrystalline
(charcterized by dense regions of crystallites) hydrogels, hydrogen- bonded or cpmplexation structure
(may be responsible for the three-dimetional structure formed) hydrogels
-Structure:

. Connection points of several chains: junction (tetrafunctional cross-linked), multifunctional junction,
physical molecular entanglements

co

ng

. Possible a junction is an association of polymer chains caused by van der Waal forces

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

21

2.4. Hydrogels

cu

u

du
o

Chap.2. –

22

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.4. Hydrogels

Preparation: swelling cross-linked structure in water or in biological fluids
. Chemical cross-linking: direct reaction of linear or branched polymer with at least one crss-linking

agents (difunctional, small molecular weight) or copolymerization cross-linking reaction, or cross-linking a
combination of monomer and linear polymeric chains by interlinking agents
. Photopolymerization or irradiation cross-linking
Important biomedical hydrogels
- PHEMA (poly(2-hydroxylethyl methacrylate): most widely used, inert to normal biological processes,
resistant to degradation, not absorb by the body, biocompatible, withstand heat sterilization wothour
damage, can easily prepared in several shapes and forms, used for blood-compatible applications,
artifical tendon materials

.c
om

-Polyacryamide
-MAA (methacrylic acid), MMA, MAH (maleic anhydride): useful monomer for preparation of hydrogels
-PVA:hydrophilic, nontoxic, good mucoadhesive properties
-PEO and PEG
Applications:

ng

-Used for blood-compatible applications, artificial tendon materials, wound healing bioadhesive, artificial
kidney membranes, artificial skin, articular cartilage (PHEMA, PVA, Polyacryamide)

co

-Very popular in pharmaceutical application: swelling-controlled release system (for bioactive agents),
such as drug release system (PHEMA, PVA

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

23

du
o

Chap.2. –

2.5. Smart polymers

Smart polymers (Stimulus-responsive, interlligent polymers)

u

-Are polymers that respond with sharp, large property change to small change in
physical or chemical conditions

cu

-Other names: environmentally sensitive polymer
-Can take many forms
-May be dissolved in aqueous solution (convert from solution to a gel): polymers with
alcohol groups: poly(hydropropyl acrylate), PVA derivates…
- May be absorbed or grafted on aqueous-solid interfaces (converting interface fron
hydrophilic to hydrophobic):PNIPAAm

- May be cross-linked in the form of hydrogels: PNIPAAm

24

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.5. Smart polymers

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

25

2.5. Smart polymers

cu

u

du
o

Chap.2. –

26

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.6. Biodegradable polymers

co

ng

.c
om

Examples of
Biodegradable Polymers

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

27

2.5. Smart polymers

cu

u

du
o

Chap.2. –

28

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.6. Biodegradable polymers

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

29

du
o

Chap.2. –

2.6. Biodegradable polymers

cu

u

Mechanism of
chemical degradation

30

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.7. Natural polymers

co

ng

.c
om

Examples of natural polymers

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

31

du
o

Chap.2. –

2.7. Natural materials

cu

u

Structure of protein

32

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.7. Natural materials

co

ng

.c
om

Collagen

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

33

2.7. Natural materials

cu

u

du

o

Chap.2. –

34

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

Chap.2. –

2.7. Natural materials

co

ng

.c
om

Elastin

Advanced Program Biomedical Engineering – HUST, Vietnam

ng

th

an

35

du
o

Chap.2. –

2.7. Natural materials

cu

u

Glucosaminoglycans

36

CuuDuongThanCong.com

Advanced Program Biomedical Engineering – HUST, Vietnam

/>

2.7. Natural materials

co

ng

.c
om

Chap.2. –

Advanced Program Biomedical Engineering – HUST, Vietnam

cu

u

du
o

ng

th

an

37

CuuDuongThanCong.com

/>