Table 1.

An overview of “Biomaterials” section, natural polymers.

Natural* , **		Pro	Contra
(Glyco)proteins	Fibrin	‐ Injectable ‐ Suitable for bioprinting ‐ High elasticity ‐ High stability ‐ Cell adhesive sequence***	Mechanically weak
	Silk fibroin	‐ Outlasts structural integrity of Fibrin and collagen ‐ Controllable mechanical properties ‐ Suitable for bioprinting, mixture with gelatin ‐ Stiffness comparable to brain tissue	Adhesive properties have to be added
	Fibronectin	‐ Cell adhesion properties *** ‐ Ability to sequester nutrients and growth factors ‐ Produced by patients own cells ‐ Used as a coating of synthetic polymers
	Laminin	‐ Injectable ‐ No need for gelation initiator ‐ Cell adhesive sequence both RGD and IKVAV***
	Collagen	‐ Injectable ‐ Cell adhesive sequence*** ‐ Successful in microfluidic systems	Harmful cell encapsulation conditions
Matrigel™		‐ Injectable ‐ Approved commercial product ‐ Several ECM proteins and growth factors present ‐ cell adhesion properties	Harmful cell encapsulation conditions
Polysaccharides	Hyaluronic acid	‐ Adds compression strength, lubrication, and hydration to ECM ‐ injectable ‐ Control of permeability by methacrylation ‐ Stiffness comparable to brain tissue ‐ Stimulates angiogenesis	No cell adhesion motifs
	Alginate	‐ Injectable ‐ Suitable for bioprinting	‐ No cell adhesion motifs ‐ Variable 3D structure ‐ Nonphysiological conditions during gelation
	Chitosan	‐ Antimicrobial anti‐inflammatory ‐ Physiological cell encapsulation conditions when modified	‐ No cell adhesion motifs ‐ Poor solubility

Background information is indicated by symbols.

^*In almost all natural polymers there is a potential risk of pathogen transmission, because most of them are derived from animal sources.

^**Most natural polymers are subject to batch‐to‐batch variation, inhomogeneity and they are easily degraded in a physiological environment.

^***RGD adhesive motif may not always be exposed for integrin binding, this depends on the protein conformation (Bellis, 2011).