Table 2.

Photopolymerizable Biomaterials Used in Light-Based 3D Printing

biomaterial	strengths	weaknesses	ref
Natural
gelatin methacrylate (GelMA)	biocompatible biodegradable cell adhesive properties (i.e., RGD motifs)	oxygen inhibited heterogeneous polymer networks due to chain growth photopolymerization	305
Thiol–ene gelatin	biocompatible biodegradable cell adhesive properties (i.e., RGD motifs) not oxygen inhibited hmogeneous polymer network highly efficient step growth photopolymerization	thiol moieties may spontaneously form disulfide bonds poor storage stability	306,307
collagen methacrylate	biocompatible biodegradable cell adhesive properties (i.e., RGD motifs)	oxygen inhibited heterogeneous polymer networks due to chain growth photopolymerization	308
hyaluronic acid (HA) and derivatives	biocompatible biodegradable high water affinity	oxygen inhibited heterogeneous polymer networks due to chain growth photopolymerization does not support cell adhesion	141,144,159
decellularized extracellular matrix (dECM)	recapitulates complexity of biochemical constituents within native ECM biocompatible biodegradable cell adhesive properties	improper decellularization can introduce immunogenicity inherently mechanically weak and lacks structural integrity thus requires combination with other biomaterials to maintain structural fidelity batch-to-batch variability	146,148,152
alginate	biocompatible biodegradable low cytotoxicity minimal foreign body reaction	does not support cell adhesion ion leaching can lead to instability	153,161
Synthetic
polyethylene glycol (PEG) derivatives (e.g., PEDGA, PEGMA, multiarmed PEG)	biocompatible biodegradable low cytotoxicity tunable mechanical strength	does not support cell adhesion low degradation rate lacks biochemical composition of native tissue	170,309
pol(glycerol-co-sebacate) (PGS) derivatives (e.g., PGSA, PGSM)	biocompatible biodegradable elastic nature can withstand dynamic tissue environments	limited range of mechanical properties potential cytotoxicity due to acid degradation rapid degradation kinetics	181,217,310
polyurethane (PU)	excellent mechanical properties and biocompatibility low immune response in vivo can form interpenetrating polymer networks (IPN) with other polymers such as epoxy and acrylates without bulk phase separation polycarbonate-based and polyolefm-based PUs demonstrate better hydrolytic resistance and oxidative stability	polyester-based PUs are prone to attacks from hydrolytic enzymes, thus limiting its applications in long-term devices polyether-based PUs were fragile against stress cracking after implantation	240,241
Composite
organic nanomaterials in hydrogels (e.g., carbon nanotubes, graphene oxide)	enhanced stiffness electroconductive cytocompatible in some applications	brittle prepolymer opacity increases due to nanofiller addition, which affects printability	265–271
metallic nanomaterials in hydrogels (e.g., gold, silver, iron nanoparticles)	electroconductivity for sensors magnetic properties for spatial control drug delivery MRI contrast agents	some MNP variants may affect cell viability and function little if any improvement on mechanical properties	272,277–282
inorganic nanomaterials in hydrogels (e.g., hydroxyapatite, silicate, glass, silica)	increase hydrogel toughness hydroxyapatite is bioactive for promoting osteogenesis reduces hydrogel swelling	little to no effect on the compressive modulus inorganic NPs tend to aggregate as concentration increases increases opacity with increased nanofiller concentration	283–286
polymeric nanomaterials in hydrogels (e.g., dendrimers, liposomes, polymeric micelles)	controlled drug release site-specific drug delivery detoxification	can require organic synthesis (i.e., not off-the-shelf) generally no improvement on mechanical properties	265,266,287,289
composite natural hydrogels (e.g., GelMA–AlgMA, GelMA–CMCMA, GelMA–HAMA)	expression of multiple bioactive binding domains dual cross-linking mechanisms when incorporating with alginate/AlgMA tunable mechanical and physical properties	batch-to-batch variability limited upper range of mechanical properties	297,299
composite synthetic-natural hydrogels (e.g., PEGDA–GelMA)	improved and wider tunable range of mechanical properties over natural hydrogels alone tunable degradation time	synthetic components generally cannot be remodeled by cells limited MWs and concentrations of synthetic components are cytocompatible	162,297
interpenetrating polymer network (IPN) hydrogels (e.g., thiol—yne and methacrylate systems)	exceptional increase in toughness as well as other mechanical properties very compatible with light-based printing techniques	limited in material choices as it requires two different cross-linking mechanisms and miscible (bio)polymers	301,302,304,311