3D Printing of Bipolymers

Additive manufacturing (AM) techniques

• AM techniques include extrusion (FDM, 3D dispensing, 3D fiber deposition,

and 3D plotting), vat photopolymerization (stereolithography), powder

bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D

printing), sheet lamination (LOM) and 3D bioprinting

• FDM (fused deposition modeling): the most commonly used AM technique.

• While FDM is limited to extrusion of thermoplastics at elevated

temperature, 3D (micro) extrusion enables 3D deposition of many other

classes of materials including thermosets, rubbers, polyurethanes,

silicones, organic and inorganic pastes, polymer latex, plastisols,

biomaterials, hydrogels, various functional polymers, and even

biologically active ingredients and living cells.

(1) Samuel Clark Ligon , Robert Liska, Jürgen Stampfl, Matthias Gurr, and Rolf Mülhaupt, Polymers for

3D Printing and Customized Additive Manufacturing, Chem. Rev., 2017, 117 (15), pp 10212–10290

(http://pubs.acs.org.libproxy.aalto.fi/doi/10.1021/acs.chemrev.7b00074)

3

Technologies for 3D printing.

The basic principle of 3D printers is building objects layer by layer

Ad van Wijk & Iris van Wijk. 3d Printing With Biomaterials, Towards a Sustainable and

Circular Economy. (http://www.biobasedplastics.nl/wp-content/uploads/2015/02/3D-printing-

with-biomaterials.pdf)

4

http://ac.els-cdn.com.libproxy.aalto.fi/S0032386116310461/1-s2.0-S0032386116310461-main.pdf?_tid=618dab44-

dfc7-11e6-a358-00000aacb361&acdnat=1484995991_aadebf9826348d9e87927f36a595e69e

https://repositorio.unican.es/xmlui/bitstream/handle/10902/6694/376365.pdf?sequence=1

https://airwolf3d.com/product-category/3d-printers/

Fused Deposition Modelling (FDM):widely used cheap and convenient 3D-

manufacturing method.

Image of fused deposit modeling

http://www.custompartnet.com/wu/3d-printing

Powder bed and inkjet head 3D printing

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Synthesis of biodegradable photocrosslinkablepolymers for stereolithographybased 3Dfabrication of tissueengineering scaffolds

and hydrogels, (https://aaltodoc.aalto.fi/handle/123456789/18252 ) here (hyperlink)

• Polymer resin needs to be in liquid form

• In SLA the liquid polymer resin is

hardened with light.

• The structure and material properties

needed depends on the target product

Schematic picture of SLA apparatus (1)

Stereolithography, SLA

• Exposure time How fast the material solidifies • Layer thickness• liftoff distance How viscose the material is

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Biopolymers used

for 3-D printing

Polymers are by far the most utilized class of materials for AM.

The range of polymers used in AM encompasses thermoplastics, thermosets,

elastomers, hydrogels, functional polymers, polymer blends, composites,

and biological systems.

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(1) European Bioplastics (http://www.european-bioplastics.org/)

(2) Wijk, A. & Wijk, I. 3D PRINTING WITH BIOMATERIALS TOWARDS A SUSTAINABLE AND

CIRCULAR ECONOMY, IOS Press, Neatherland, 2015, 86p. DOI 10.3233/978-1-61499-486-2-i

(3) Material Data Center (https://www.materialdatacenter.com/bo/standard/)

Bioplastics in 3-D printing

Bioplastics can be (a) biodegradable or (b)

bio-based or belong to both categories.(1)(2)

Thermoplastics are commonly used in 3D

printing. The most used is polylactid acid

(PLA) which belongs to both of the

categories.(2)

Examples from other plastics for 3D printing:

(a) PCL,

(b) PA-11, TPC, TPS, and

(a)&(b) PLLA, PLGA.(1)(2)(3)

The division between biobased and biodegradable (1)

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Biodegradable PCL(polycaprolactone) -scaffolds for tissue engineering

PVOH (polyvinyl alcohol)- multilayer applications (e.g.

films)

PTT (poly(propylene fumarate) -scaffolds for tissue

engineering

Polycaprolactone (PCL), FDM and Stereolitography

(SLS)

PA 11, PA 12 (biodegradable?)

Poly(glycolic acid) (PGA)

Gelatin methacrylate

Polypropylene fumarate (PPF), SLS

Polyethylene Glicol (PEG)

Polybutylene terephthalate (PBT), FDM

PGA (Polyglykol acid) -absorbable sutures

PCL (Polycaprolactone)-long term implants

PA (Polyanhydride) -drug delivery

PPF (polypropylene fumarate), POE (polyorthoesters),

PU (polyurethanes), PPy (polypyrroles), PDS

(polydioxanones),

Acrylated polyglycerol sebacate (Acr-PGS)

Acrylic-based resin (FullCure®720).

Bio-based• PHB (poly(3-hydroxybutyrate))-porous structures

• PLA (polylactic acid) -e.g. in biomedical devices,

laboratory equipment, FDM

• Poly (D,L-lactide) (PDLLA), SLS

• Hydrogels: Alginate, Agar, Gelatin,

Nanocellulose, Fibrinogen, Agarose, Alginate, K-

Carrageenan, Chitosan, Chondroitin Sulfate,

Dextran, Elastin, Fibrin, Gellan Gum,

Hyaluronan, Methylcellulose, Hyaluronic Acid,

Starch.

• Lignin

• Soy protein, Collagen, Gelatin,

• Poly(lactate/butanediol/sebacate/itaconate)

(PLBSI)

• Poly (lactic) acid (PLA) used in FDM-scaffolds

• Poly (D,L-lactide) (PDLLA) used in SLS

Natural polymers

• Hydrogel-forming biopolymers are

suitable for 3D printing

• Natural polymers in combination with

water-based binders has shown to

be promising for use in direct 3D

printing

• Solidification upon extrusion is a

challenge when natural biopolymers

are 3D printed

• Biopolymers are often 3D printed in

liquid media (electrostatic

interactions between the biopolymer

and the liquid media may be a

problem)

Important polymer properties

• Processing

• Rheology (1)

• Transition temperatures (e.g.

melting) (1,2)

• Product

• Mechanical properties (3)

• Biodegradation (2)

• Biocompatibility (2)

3D-printing often for medical

applications

• Customisable, personal products (1)

• Biodegradability enables temporary

use (2)

• Regrowth of tissue

(3) Patricio, T. et al. 2014 (http://www.emeraldinsight.com.libproxy.aalto.fi/doi/full/10.1108/RPJ-04-2012-0037)

(4) Dávila, J.L. et al. 2015 (http://onlinelibrary.wiley.com.libproxy.aalto.fi/doi/10.1002/app.43031/full)

(5) Yao, Q. et al. 2015 (http://link.springer.com.libproxy.aalto.fi/article/10.1007%2Fs10856-014-5360-8)

PLA (Polylactid acid)

https://ultimaker.com

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Poly(lactic acid) or polylactide (PLA), aliphatic polyester

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Structure/Production method:

• Bio-based monomer (lactic acid) by fermentation, followed by polymerisation

Current bulk producers

• Cargill Dow (Nature Works)

• ADM

• PURAC

• GalacticSelling price:

• 1,50‒2,00 €/kg

• 15 years ago: >10 €/kg

Poly(lactic acid) and polylactide (PLA) Source: Niaounakis M. (2014)

(6) Wolf O. et al. (2005): Techno-economic Feasibility of Large-scale

Production of Bio-based Polymers in Europe [6]

(7) Niaounakis M. (2014): Biopolymers: Processing and Products ([7])

Production:

• Fermentation to lactic acid monomers

• Polymerization to poly lactic acid

Pro:• Good biocompatibility• Good process ability • Biodegradable &

Biobased• Exact 3D-printability (2)

Con:• Brittleness• Hardness• Odure• Expensive (3)

(1) Siegma Aldrich, (2018). (Link)

(2) Wolf O. et al. (2005): Techno-economic Feasibility of Large-scale (Link)

(3) Winter et al., (2017): Residual wood polymers facilitate compounding of microfibrillated cellulose with poly(lactic acid) for 3D printer filaments (Link)

• PLA can be used in many applications and

modified with different compounds,

copolymerizations and blends.

• 3D printing can reduce the manufacturing cost

of smaller batches when no molds are needed.

• The possibilities in the medical field are

endles.

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Properties of PLA required for FDM

• Thermoplastic

• Tg: 55-65 [C] (rel. low)

• Melting point: 120-170 [C]

• Nozzle temperature around 180 C, lower than ABS

• Printing Temp.190-240 [C]

• Melt flow rate: 2.2 g/10 min.

• Density 1.25 [g/cm3] (PET: 1.34)

Further Properties

• Native biocompatibility

• Bio-based

• Biodegradable

• Blends: PLA/PCL, PLA/PHA, PLA/starch…

• Technical substitution potential: PMMA, PA, PET, PP

Fused deposition modelling schematic

Source: Chia H.N. et al. (2015)

(6) Wolf O. et al. (2005): Techno-economic Feasibility of Large-scale Production of Bio-based Polymers in Europe [6]

(7) Niaounakis M. (2014): Biopolymers: Processing and Products ([7])

(8) Song Y. et al. (2017): Measurements of the mechanical response of unidirectional 3D-printed PLA [8]

(9) Chia N. H., Wu M. B. (2015): Recent advances in 3D printing of biomaterials [9]

(11) Serra T. et al. (2012): High-resolution PLA-based composite scaffolds via 3-D printing technology [11]

(12) Wang Z. et al. (2017): Preparation of 3D printable micro/nanocellulose-polylactic acid (MNC/PLA) composite wire rods with high MNC constitution [12]

(14) Bose S. et al. (2017): Additive manufacturing of biomaterials [14]

Poly(ε-caprolactone)

• Biodegradable polyester

• Semicrystalline polymer

• Melting temperature is higher

than body temperature, high

toughness

• Degrades slowly (among

polyesters)

• Useful for biomedical matierials

due to phisycal and biological

properties

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M. Abedalwafa, F. Wang, L. Wang, C. Li Biodegradable

PCL for tissue engineering applications: A review

Polycaprolactone

• Synthetic: Homogeneity, quality and

purity

• Thermoplastic & good rheological

properties(1)

• Relatively low melting point (~60 C)(1,2)

= easier processing (melt extrusion)

• Biodegradable and biocompatible(2)

• Good mechanical properties(3)

(1) Patricio, T. et al. 2014 (http://www.emeraldinsight.com.libproxy.aalto.fi/doi/full/10.1108/RPJ-04-2012-0037)

(2) Dávila, J.L. et al. 2015 (http://onlinelibrary.wiley.com.libproxy.aalto.fi/doi/10.1002/app.43031/full)

(3) Yao, Q. et al. 2015 (http://link.springer.com.libproxy.aalto.fi/article/10.1007%2Fs10856-014-5360-8)

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(1) 3D Printing of Polycaprolactone Scaffolds

(2) In vivo biocompatibility and biodegradation of 3D-printed porous scaffolds based on a hydroxyl-functionalized

poly(ε-caprolactone

(3) 3D Printing Polymers with Supramolecular Functionality for Biological Applications

(4) 3D Printing Polymers with Supramolecular Functionality for Biological Applications

Low melting point allows for ease of 3d-Printing.

Is biocompatible, no toxic effects in the body and

is degraded slowly in the body allowing natural

tissue to replace it

Flexibility of material makes it ideal for structures

such as blood vessels and ligaments.(1)

One disadvantage is the high hydrophobicity limits

cell adhesion and degradation. Treatment to

cause hydroxylation of the PCL backbone can

mitigate this issue.(2)

High molecular weight means only extrusion 3D-

printing possible(3)

PCL as a biocompatible polymer in 3D-printing

Material properties of PCL

PCL scaffold transplanted in the gap

between the heads of ulna bone. [4]

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(1) Small Diameter Blood Vessels Bioengineered From Human Adipose-derived Stem Cells

(2) Polymer structure-property requirements for stereolithographic 3D printing of soft tissue engineering scaffolds

(3) In vivo biocompatibility and biodegradation of 3D-printed porous scaffolds based on a hydroxyl-functionalized

poly(ε-caprolactone

(4) 3D Printing Polymers with Supramolecular Functionality for Biological Applications

3D printing of biopolymers allows the creation of

personalized tissue scaffolds.

Allows for creation of structures specific for the

injury/condition the patient has.

Cells are implanted then infiltrate and adhere to

the porous PCL structure created.(2)(4)

PCL is slowly broken down over time by

macrophages, replaced with implanted cells.(3)

Breakdown is non toxic over the timescale it

occurs.(2)

3d printed PCL based blood vessel

(top) and antibody stains showing

integration of vascular tissue

below.(1)

PCL based tissue scaffolds

Nanocellulose

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Direct Ink Write (DIW) 3D Printed Cellulose Nanocrystal Aerogel Structures6

Polymer properties

High elastic modulus (110-220GPa), high strength

due to crystallinity, light weight, low density,

sustainability, biocompatibility, biodegradability,

recyclability, abundance in nature7

Flexibility allows to construct custom structures

which hold their form due to high Young’s

modulus.6

Challenges

o Increased concentration of CNCs leads to

higher viscosity which increases pressure

during the gel deposition through direct ink

write.

o Material brittleness can lead to structure

collapse during cell incorporation and growth.

(can be fixed with cross-linking with Kymene)

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(6) https://doi.org/10.1038/s41598-017-07771-y

(7) https://doi.org/10.1039/c0cs00108b

http://cellulosefromfinland.fi/3d-printing-of-cellulose-based-materials/

(5) M.I Santos. I. Pashkuleva. C.M. Alves. M.E. Gomes. S. Fuchs. R. E. Unger. J. Mater. Chem., 2009,19, 4091-

4101 (http://pubs.rsc.org.libproxy.aalto.fi/en/Content/ArticleLanding/2009/JM/b819089e#!divAbstract)

(6) Filipa A M M Gonçalves, Biofabrication 6 (2014) 035024 (14pp)

(http://iopscience.iop.org.libproxy.aalto.fi/article/10.1088/1758-5082/6/3/035024/meta)

• The main application of 3D bioprinting is human cartilage

tissue, for instance, the human ears.

• The nanofibrilar cellulose reinforced alginate provides the

material enough viscosity. And crosslinking provides less

shape deformation.

• To improve the shape fidelity of the alginate, NFC could be

involved as the main component.

Small grid printed with

(C1) 3% alginate

and (C2) 2.5% NFC.

(C3) Small grid of

printed and cross-

linked. [10]

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Figure 1. CNC gel structures at (a) 11.8, (b) 15, (c) 20, and (d) 30wt%. https://doi.org/10.1038/s41598-017-07771-y

Producing CNC aerogels with controllable porosity allows for its application in

tissue engineering because of the open cell type porous structures. Solvent

absorption, cell seeding medium infusion, oxygen permeation, nutrient transport,

cell growth, or metabolic waste removal is thus possible.

Great potential for 3D printing, especially when combined with strength additives.

Chitosan

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(1) (http://www.sciencedirect.com/science/article/pii/S0734975011000061)

(2) (https://pdfs.semanticscholar.org/af57/fa5a2b237174301b9b2740adbbe531a4a527.pdf)

(3) (http://www.sciencedirect.com/science/article/pii/S0734975009001852)

(4) (http://www.sciencedirect.com/science/article/pii/S0144861710003589)

(5) (http://www.mdpi.com/1660-3397/13/8/5156/htm)

Chitosan

Properties• Derative of Chitin,

• Abundant natural polymer next to

cellulose

• Linear,Reactive mino group,

• Crystalline,

• Insoluble in water,

• Renewable,

• Cationic nature

• Found in Insect, Shrimps, Crabs, Fungi,

Oysters, Shellfish,

• Biocompatible,Biodegradable,Non-

toxcic

Pros

• Minimal foreign body reaction.

• Antibacterial nature.

• Molded in different structures.

• Excellent bioestimulation.

• Good degradation rate.

Cons

• Chitosan decompose (>220ºC). May

not give the desired mechanical

properties when trying to print stable

composite structures.

Challenges in processing• High viscosity

• Poor/low solubility

9.2.2019

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(1) (http://www.sciencedirect.com/science/article/pii/S0734975011000061)

(2) (https://pdfs.semanticscholar.org/af57/fa5a2b237174301b9b2740adbbe531a4a527.pdf)

(3) (http://www.sciencedirect.com/science/article/pii/S0734975009001852)

(4) (http://www.sciencedirect.com/science/article/pii/S0144861710003589)

(5) (http://www.mdpi.com/1660-3397/13/8/5156/htm)

Main application and its performance

Application:• Tissue enegineering,wound dressing,

• durg delivery,organ regeneration,

• Water treatment-waste separation membrane,

• Biosensor

• Cosmotics

Performance: Example-wound dressing1

• Promot tissue growth,

• Anti-fungal, anti-bacterial, permeable to oxygen,

• Facilitate cell attachment and maintain,

• Helps in blood clotting,

• Reduce pain, accelerate wound healing and scar prevent

• Accelerate repair of different tissue, regulate secretion of inflammatory

Figure 3. Wound dressing 1

Alginate

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Alginate Hydrogels

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Alginate worms

Cross-linked calcium alginate hydrogel (http://people.clarkson.edu/~amelman/alginate_hydrogels.html)

Poly(Glycolic Acid), PGA

(1) 海藻酸鈉＿百度百科(https://baike.baidu.com/item/海藻酸钠)

(2) 3D-Printed Biopolymers for Tissue

Engineering Application

（https://www.hindawi.com/journals/i

jps/2014/829145/

(3) https://biomeder.com/3d-printing-

strand-bioink/）(4) 聚乙醇酸＿百度百科

(https://baike.baidu.com/item/聚乙醇酸)

Low molecular weight PGA was already

synthesized 40 years ago, by ring- opening

polymerization of DL-Lactide and glycolide.

However, the Mechanical strength of it wasn’t

enough to create more solid structure, nor

materials for 3D printing, thus, low molecular

PGAs are normally used in sutures.

Fortunately, when molecular weight of PGA is

up to 20000 ~ 145000, the polymer can be pull

into fibrous status, and can make the

arrangement of the molecules inside be

directional, which increase the strength of the

polymer, and allows it to form into different

shapes.

PGA

(5) Structure-Processing-Property Relationship of Poly(Glycolic

Acid) for Drug Delivery Systems 1:Synthesis and

Catalysis(https://www.hindawi.com/journals/ijps/2010/65271

9/)

(6) http://china.chemnet.com/product/pclist--

%BE%DB%D2%D2%B4%BC%CB%E1--0.html

Although low molecular weight PGAs has

a lower mechanical strength and is also

easy to degrade, which cannot be used

in 3D printing, there is still a lot of ways

to increase the mechanical strength, for

example self-reinforcement.

Due to the low mechanical strength,

PGAs are normally used as Sutures in

surgeries, but not as 3D printing material,

however, with the immensely increased

property, it become a possible option for

PGA to be apply as 3D printing.

PGA

Starches and other polysachharides(Gellan Gum)

[2] Li, Xiaoming, et al. "3D-printed biopolymers for tissue engineering application." International Journal of Polymer

Science 2014 (2014).

6] Lam, Christopher Xu Fu, et al. "Scaffold development using 3D printing with a starch-based polymer." Materials

Science and Engineering: C 20.1 (2002): 49-56.

Plastarch material (PSM)• Plastarch material is composed of PLA grafted onto

starch nanoparticles. It has the basic processability of

PLA but increased mechanical strength and is no

longer hydrophobic like mere PLA. [4]

• Plastarch can be manufactured with the same

equipment as more common plastics. [4]

• Being starch-based, the production of PSM competes

with food production. [5]

(4) García, Lamanna, D’Accorso, Dufresne, Aranguren & Goyanes: Biodegradable materials from grafting of modified PLA onto starch

nanocrystals; Polymer Degradation and Stability;

Volume 97, Issue 10, October 2012;

(http://www.sciencedirect.com/science/article/pii/S0141391012001103)

(5) Barker & Safford: Industrial uses for crops: markets for bioplastics (https://cereals.ahdb.org.uk/media/408426/pr450-final-project-

report.pdf)

[6] Lam, Christopher Xu Fu, et al. "Scaffold development using 3D printing with a starch-based polymer." Materials Science and

Engineering: C 20.1 (2002): 49-56.

(7) ECO Products: PSM Cutlery (https://www.ecoproductsstore.com/plant_starch_cutlery.html)

Although usually biodegradable,

PSM items are not recyclable. [7]

34

(1) Kirchmajer, D. M. et al. An Overview of the Sustainability of Hydrogen-forming Polymers for Extrusion-based 3d-printing. 2015.

(http://pubs.rsc.org.libproxy.aalto.fi/en/content/articlepdf/2015/tb/c5tb00393h)

(2) In het Panhuis, M. et al. Inkjet Printed Water Sensitive Transparent Films for Natural Gum-carbon Nanotube Composites. 2007.

(http://pubs.rsc.org.libproxy.aalto.fi/en/content/articlepdf/2007/sm/b704368f)

(3) Pidcock, G. C. & in het Panhuis, M. Extrusion Printing of Flexible Electrically Conducting Carbon Nanotube Networks. 2012.

(http://onlinelibrary.wiley.com.libproxy.aalto.fi/doi/10.1002/adfm.201200724/full)

(4) Image (http://www.ciaoimports.com/assets/images/willpowder/gellanlow.jpg)

Gellan Gum

• Anionic, polysaccharide biopolymer

• Hydrogel formation mechanism:

ionotrophic gel formation with cations

• Produced by Sphingomonas elodea

bacteria

• Used as a gelling, stablishing and

suspending agent

• In 3d printing used as a thickener

Commercial gellan gum

Proteins

(4) Inzana, Jason A.; Olvera, Diana; Fuller, Seth M.; Kelly, James P.; Graeve, Olivia A.; Schwarz, Edward M. et al. (2014): 3D printing of composite calcium

phosphate and collagen scaffolds for bone regeneration. In: Biomaterials 35 (13), S. 4026–4034. DOI: 10.1016/j.biomaterials.2014.01.064. (hyperlink4)

(5) Wu, Zhengjie; Su, Xin; Xu, Yuanyuan; Kong, Bin; Sun, Wei; Mi, Shengli (2016): Bioprinting three-dimensional cell-laden tissue constructs with

controllable degradation. In: Scientific Reports 6, S. 24474. DOI: 10.1038/srep24474. (hyperlink5)

(6) Wikipedia (Hg.) (2017): Collagentriplehelix - Collagen - Wikipedia. Online verfügbar unter https://en.wikipedia.org/w/index.php?oldid=759139140, zuletzt

aktualisiert am 16.01.2017, zuletzt geprüft am 20.01.2017.

(3) Chia, Helena N.; Wu, Benjamin M. (2015): Recent advances in 3D printing of biomaterials. In: Journal of

biological engineering 9, S. 4. DOI: 10.1186/s13036-015-0001-4. (hyperlink3)

(4) Inzana, Jason A.; Olvera, Diana; Fuller, Seth M.; Kelly, James P.; Graeve, Olivia A.; Schwarz, Edward M. et

al. (2014): 3D printing of composite calcium phosphate and collagen scaffolds for bone regeneration. In:

Biomaterials 35 (13), S. 4026–4034. DOI: 10.1016/j.biomaterials.2014.01.064. (hyperlink4)

38

3D-printing of gelatinmethacrylate:

• The material is a hydrogel of

polymers that are crosslinked

• The thermoresponsive behaviour

of the material allows for 3D-

printing

• Collapse of internal pores is a

challenge in processing, but can

be tackled by using stabilizing

co-polymers

(1) Li et. al. (2014) (https://www.hindawi.com/journals/ijps/2014/829145/abs/)

(2) Cruz et. al. (2010) (http://cdn.intechweb.org/pdfs/12148.pdf)

(3) Bose et. al. (2013) (http://www.sciencedirect.com/science/article/pii/S136970211300401X)

(4) Billiet et. al. (2014) (http://www.sciencedirect.com.libproxy.aalto.fi/science/article/pii/S0142961213011782)

(5) Schuurman et. al. (2013) (http://onlinelibrary.wiley.com.libproxy.aalto.fi/doi/10.1002/mabi.201200471/abstract)

Figure 2. The workflow related to the use of

3D-printing in tissue engineering [4]

39

• Gelatin methacrylate can be used in

tissue engineering

• The hydrogel is used as a cell 3D

scaffold, it is porous and these pores can

be cell laden for tissue growth

• The material is highly biocompatible and

can be precisely designed

• Cells can be grown without changes in

phenotype and the flow of water, oxygen

and nutrients is steady in the hydrogel

(1) Li et. al. (2014) (https://www.hindawi.com/journals/ijps/2014/829145/abs/)

(2) Cruz et. al. (2010) (http://cdn.intechweb.org/pdfs/12148.pdf)

(3) Bose et. al. (2013) (http://www.sciencedirect.com/science/article/pii/S136970211300401X)

(4) Billiet et. al. (2014) (http://www.sciencedirect.com.libproxy.aalto.fi/science/article/pii/S0142961213011782)

(5) Schuurman et. al. (2013) (http://onlinelibrary.wiley.com.libproxy.aalto.fi/doi/10.1002/mabi.201200471/abstract)

Figure 3. The material

architecture and pore

network [4]

Poly(3-hydroxybutyrate) PHB

41

[6] https://www.hindawi.com/journals/ijps/2014/829145/

[7] http://onlinelibrary.wiley.com/doi/10.1002/masy.201100237/full

[8] http://www.nature.com/articles/srep31140

[9] http://previews.123rf.com/images/molekuul/molekuul1204/molekuul120400071/13373407-Chemical-

composition-of-polyhydroxybutyrate-bioplastic-a-sustainable-alternative-to-oil-based-plasti-Stock-Photo.jpg

Poly(3-hydroxybutyrate) (PHB) :

• Natural polyester produced by microorganisms [6]

• Thermoplastic polymer - does not require additives such as

plasticizers [6]

• Biocompatible and biodegradable: Good for biomedical

applications [6]

• Non-toxic [6]

• Resistant to handling without presenting any visible damage

[7]

• Can be re-utilized to print additional structures without

affecting the reproducibility of the process [7]

• Drawbacks: hydrophobicity, surface chemical inactivity and

the lack of functional groups

• PHB can be used to produce scaffolds for tissue engineering

[6] (via Selective Laser Sintering from powder form) Chemical composition of poly(3-

hydroxybutyrate) [9]

Properties

• PHB presents mechanical properties

close to polypropylene and and other

biodegradable polyesters such as

polylactides.

• PHB is thermoplastic, which enables

fabrication. It becomes moldable

above a specific temperature and

solidifies upon cooling.

• Properties can be modified by

copolymerization.

• PHB is fabricated into a porous

structure, which effects its mechanical

properties that are important to the

fabricated object.

9.2.2019

42(1) 3D rinting of PHB porous structures Using Selective Laser Sintering (hyperlink)

(2) Synthesis, Structure and properties of PHAs: biological polyesters (hyperlink)

• Porous structure• Studies showed that the porous structure

of the printed model showed some

variation to the digital model.

• Challenge in processing is that

PHB might undergo thermal

degradation• Studies show that processing

does not have a major effect on the

thermal degradation

Chondroitin Sulphate(CS)

44

(5) Abbadessa, A., Blokzijl, M. M., Mouser, V. H. M., Marica, P., Malda, J., Hennink, W. E., & Vermonden, T. A thermo-responsive and photo-polymerizable chondroitin sulfate-

based hydrogel for 3D printing applications. Carbohydrate Polymers, 149, 163–174, 2016 http://doi.org/10.1016/j.carbpol.2016.04.080

(6) Silva, J. M., Georgi, N., Costa, R., Sher, P., Reis, R. L., van Blitterswijk, C. A., Mano, J. F. Nanostructured 3D Constructs Based on Chitosan and Chondroitin Sulphate

Multilayers for Cartilage Tissue Engineering. PLoS ONE, 8(2), 2013 http://doi.org/10.1371/journal.pone.0055451

Image from http://www.webmd.com/first-aid/cartilage

Chondroitin Sulphate (CS)

• The main glycosaminoglycan (GAG)

• component of cartilage.

• Responsible for providing compressive

loading

• resistance and maintenance of

cartilage.

• High negative charge density and

lipophilic nature

• lead to retention of water in extra-

cellular matrix.

• Fluctuation in water content provides

the compression resistance.

• Crucial components in the CNS,

capable of modulating nervous tissue.

• High load and stress resistance.

• Natural component of cartilage (removing

most toxicity issues.)

• Capable of high cell binding, partially due

to it’s high negative charge allowing it to

react with cell surface proteins.

• Control of factors such as porosity allows

modification of reaction.

• Natural presence in CNS allows for uses

in nervous tissue repair.

9.2.2019

45

Chondroitin Sulphate (CS)• Uses of products primarily in cartilage tissue engineering.

• Multi-layered support structures produced with chitosan.

• Cells readily attach, proliferate and remain metabolically active.

• In other studies, hydrogels of CS and large co-polymers have been

produced.

• These show good stress resistance, tunable porosity and cell binding

ability.

Photographs of CS involved hydrogel produced

3D structures with 2mm strand spacing

SEM Micrograph of chitosan and CS

structures on glass coverslips after 1 (top)

and 21 (bottom) days

(5) Abbadessa, A., Blokzijl, M. M., Mouser, V. H. M., Marica, P., Malda, J., Hennink, W. E., & Vermonden, T. A thermo-responsive and photo-polymerizable chondroitin sulfate-

based hydrogel for 3D printing applications. Carbohydrate Polymers, 149, 163–174, 2016 http://doi.org/10.1016/j.carbpol.2016.04.080

(6) Silva, J. M., Georgi, N., Costa, R., Sher, P., Reis, R. L., van Blitterswijk, C. A., Mano, J. F. Nanostructured 3D Constructs Based on Chitosan and Chondroitin Sulphate

Multilayers for Cartilage Tissue Engineering. PLoS ONE, 8(2), 2013 http://doi.org/10.1371/journal.pone.0055451

• Scaffolds can also be produced from CS and carbon nanotubes.

• Can produce a viable and neuron-rich network for use in nervous

tissue lesions.

• Possible uses in nerve regeneration, particularly when used soon after

injury.