Table 1: Traditional scaffolds available for bone tissue engineering.

Scaffold type	Example	Derivation	Main advantages	Limitations
Natural	Alginate	Polysaccharide (derived from seaweed)	Licensed for clinical use. Available as a hydrogel or microparticle . Easy functionalization with growth factors/peptides and conjugation with other scaffolds.	Rapid degradation Low mechanical strength
	Collagen	Main extracellular matrix component of bone	Easily modified through addition of growth factors. Licensed for clinical use. Easily combined with other scaffolds.
	Fibrin	Fibrous protein synthesized during the clotting cascade	Licensed for clinical use. Osteoinductive properties. Mass producible.
	Gelatin	Proteins and peptides derived from collagen	Available in many forms including hydrogels
	Silk	Protein polymer	Low immunogenicity. Controlled degradation.	No long term degradation studies
	Decellularised matrix	Fabricated through decellularisation of tissues	Frequently used in preclinical and clinical tissue engineering research. Low inflammation. Preserves extracellular architecture and components.	Lengthy fabrication protocols. Risk of immunogenicity. Not easily reproducible.
Synthetic	Polygcolic acid	Polyester porous scaffold	Biodegradable Mass producible. Easily modified to alter topography or functionalise with groups/motifs.	Degradation products induce inflammation
	Polyethylene glycol	Polyether compound	Licensed for clinical use. Mass producible. Low toxicity. Biodegradable.	Low mechanical strength Rapid degradation
	Polycaprolactone	Biodegradeable polymer	Mass producible. Easily modified to incorporate groups/motifs. Provides mechanical strength.	Unstable degradation
	Poly-l-lactic acid	Biodegradable polymer	Mass producible. Easy surface modification to alter topography. Provides mechanical strength.	Rapid degradation
Natural-Synthetic composite scaffolds	Alginate/O-carboxymethyl chitosan (O-CMC)	Biodegradable hydrogel	Mass producible. Mimics extracellular matrix. Easily injected into tissues.	Rapid degradation. Low mechanical strength.
	PLGA/hydrogel	Biodegradable hydrogel	Mass producible. Provides mechanical strength.	Rapid degradation.
	Alginate/poly vinyl alcohol (PVA)	Crosslinked biodegradable scaffold	Available as a hydrogel or porous scaffold. Mass producible. Provides mechanical strength. Mimics extracellular matrix.	Unstable degradation.