Table 1.

Comparison of natural and synthetic biomaterials for 3D printing.

	Crosslinking process	Advantages	Disadvantages	Ref.
Silk fibroin (SF)	Enzymatic Photo-crosslinking Physical (sonication, solvent removal, heat, pH)	FDA approved1 Low cost Abundant Aqueous processability Controllable degradability Self-assembly Several gelation processes Cell-friendly behavior Ease of modification in vivo biocompatibility Tunable mechanical properties	Low viscosity if printed individually (high concentrations required) Lack of RGD sequences	[5,16,67]
Alginate	Ionotropic gelation (Ca ions) Photo-crosslinking	Highly hydrophilic Aqueous processability Cytocompatible	Low cell adhesion Weak mechanical properties Rapid dissolution	[33,37,50]
Hyaluronic acid (HA)	Enzymatic Photo-crosslinking Non-covalent crosslinking	Important ECM component Highly hydrophilic Different inflammatory in vivo response according to molecular weight Ease of modification Cytocompatible	Poor cell adhesion Weak mechanical Rapid degradation in vivo	[33,94,95]
Gelatin	Enzymatic Photo-crosslinking Chemical reactions Non-covalent (temperature, pH)	Good cell adhesion Tunable mechanica properties withl chemical modification Ease of processability	High concentration required (from 10 mg/mL) Poor mechanical properties Rapid degradation	[58,67,96]
Polyethylene glycol (PEG)	Photo-crosslinking Chemical reactions	Synthetic material Cytocompatible Highly hydrophilic FDA approved2	Non-biodegradable Poor cell adhesion	[50,67,97]
Pluronic F127	Physical (thermoreversible) Photo-crosslinking	Synthetic material Used as sacrificial material Water soluble	Non-biodegradable Poor cell adhesion Cytotoxic in term culture time	[36,98]
Polycaprolac tone (PCL)	Physical (thermoreversible) Photo-crosslinking	Synthetic material Biocompatible Hydrophobic Inexpensive Good mechanical strength FDA approved	Very slow degradation Low water absorption capacity Requires thermal or solvent deposition	[98,99]

¹Medical devices: surgical sutures

²Pharmaceutical field