Table 1.

Applications of additive bioprinting methods for collagen-based inks.

Bioprinting Method	Collagen-Based Ink Formulation	Outcome	Ref.
Extrusion	Methacrylated type I collagen; Sodium alginate	Fabrication of structures that resembles native human corneal stroma with cell-laden bioink via extrusion bioprinting.	[116]
Extrusion	Collagen Type I; Alginic acid sodium salt from brown algae; CaCl2 solution	Core-sheath coaxial extrusion of alginate/collagen bioink with CaCl2 allows creation of scaffolds with low collagen centration despite its low viscosity.	[114]
Extrusion	Rat tail type I collagen; Gelatin (type A); Sodium alginate	Extrusion bioprinting of collagen scaffold via gelatin/alginate system with controllable degradation time based on amount of sodium citrate during incubation.	[113]
Extrusion	Type I collagen was extracted from tendons obtained from rat tails	Identified storage modulus as the best predictor of collagen bioink printability during deposition.	[117]
Extrusion	PureCol Purified Bovine Collagen Solution; Soldium alginate (low viscosity)	Fabrication of interwoven hard (PLLA) and soft (bioink) scaffolds which support cell attachment and proliferation using a modified desktop 3D printer.	[135]
Extrusion	Methacrylated COL I; Heprasil; Photoinitiator	Successful bioprinting of liver model. Printed primary hepatocytes retained function over 2 weeks exhibiting appropriate response to toxic drugs.	[41]
Extrusion	Lyophilized Atelo-collagen, Matrixen-PSP	Pre-set extrusion bioprinting technique is able to create heterogeneous, multicellular and multi-material structures which perform better than traditional bioprinting.	[112]
Extrusion	Collagen Type I extracted from rat tails; Pluronic® F127	Fabrication of 3D constructs without chemical or photocrosslinking before and after printing via thermally-controlled extrusion.	[115]
Extrusion	Lyophilized sterile collagen, Viscoll	Formation of scaffolds which support spatial arrangement of tissue spheroids as well as support cell adhesion and proliferation.	[47]
Extrusion	Type-I collagen, Matrixen-PSP; Tannic acid	Fabrication of 3D porous structures which support cell migration and proliferation for long periods of culture. Determined optimal tannic acid crosslinking.	[67]
Extrusion	Collagen Type I; Sodium Alginate	Improved mechanical strength and bioactivity via the addition of collagen. Higher cartilage gene markers expressed, preservation of chondrocyte phenotype.	[42]
Extrusion	Type-1 collagen, Matrixen-PSP	Established a crosslinking process using tannic acid. High printed preosteoblast viability and well-defined pore size and strut dimensions for bone regeneration.	[68]
Extrusion	Type-I collagen, Matrixen-PSP; Decellularised extracellular matrix (dECM); Silk Fibroin(SF)	Hybrid collagen/dECM/SF scaffold with enhanced cellular activity and mechanical properties. Enhanced cell differentiation, mechanical properties, amenable for hard tissue regeneration.	[59]
Extrusion	Atelocollagen Type I powder	Novel self-assembly induced 3D printing to produce macro/nano porous collagen scaffolds with reasonable mechanical properties, excellent biocompatibility and mimicking native ECM.	[58]
Extrusion	Type-I collagen, Matrixen-PSP; Polycaprolactone (PCL); Hydroxyapatite (HA)/β-tricalcium-phosphate (TCP); Platelet-rich plasma(PRP)	Fabrication of collagen/PCL biocomposites loaded with bio-additives via 3D extrusion printing. Collagen/PCL biocomposites allow controlled release of HA/TCP bio-additives, which promote osteogenesis. PRP biocomposites demonstrate increased mineralisation.	[46]
Extrusion	Type-I collagen, Matrixen-PSP	Genipin crosslinking allowed fabrication of 3D cell-laden porous scaffold (Cellblock) with mechanical stability, pore size and osteogenic (bone tissue regeneration) potential.	[70]
Extrusion/Inkjet	Lyophilized collagen type 1 sponge derived from porcine skin	Development of a one-step process to produce a 3D human skin model with functional transwell system. Cost-effective compared to traditional transwell cultures.	[118]
Inkjet	Type I rat tail collagen; poly-d-lysine	Fabrication of neuron-adhesive patterns by printing cell-adhesive layers onto cell-repulsive substrates.	[123]
Inkjet	Collagen (Calf skin)	Cell aggregates printed between layers of collagen gels suitable for tissue engineering.	[125]
Inkjet	Collagen (rat-tail); collagen (calf skin)	Low-cost, high-throughput surface patterning with collagen and potentially, other proteins.	[122]
Inkjet	Collagen Type I	Fabrication of in vitro cancer microtissues via collagen inkjet printing. Four individual microtissues within one 96-well plate well, maintained for up to seven days.	[124]
Inkjet	Collagen: Type I rat tail collagen; Fibrinogen; Thrombin	Collagen bioinks and Fibrin/Collagen bioinks unsuitable for in situ inkjet bioprinting.	[136]
Inkjet	Type I acidic collagen; Agarose (low gelling temperature)	Fabrication of 3D corneal stromal structure with optically properties similar to native corneal stroma. Potential as a clinical or experimental model.	[120]
Inkjet	Acidic collagen solution; Agarose (low gelling temperature)	MSC branching, spreading and osteogenic differentiation controlled by collagen concentration; Osteogenic potential (bone tissue engineering).	[121]
Laser-assisted	Collagen Type I (Rat-tail)	Fabrication of cell-laden skin tissue using laser-assisted bioprinting, in vivo potential. Skin tissues consist of: a base matriderm layer, 20 layers of fibroblast and 20 layers of keratinocytes.	[130]
Laser-assisted	Collagen (Rat-tail)	Multicellular collagen skin tissue constructs printed using laser-assisted bioprinting. Keratinocyte and fibroblast layers did not intermix after 10 days. Mimics tissue-specific functions (e.g., gap-junction).	[129]
Laser-assisted	Type I collagen (rat) solution; Nano hydroxyapatite (nHA)	In situ printing of cell-laden collagen-based ink via laser assisted bioprinting allow bone regeneration (mouse calvaria defect model). Contact free printing method is sterile with clinical potential.	[126]
Laser-assisted	OptiCol™ human Col I; Ethylenediaminetetraacetic acid (EDTA) human female AB blood plasma; Thrombin from human plasma	Fabrication of 3D cornea tissue using novel human protein bioinks via laser assisted bioprinting. Novel bioink is biocompatible, without requiring additional crosslinking. First study to demonstrate laser-assisted bioprinting for corneal applications using human stem cells.	[131]
Stereolithography (SLA)	Collagen methacrylamide(CMA) synthesized using Type-I collagen; Irgacure (I2959)	Free-form photolithographic fabrication; photopatterned hydrogels retain structure after 24 h. CMA retains native collagen self-assembling properties; hydrogels biocompatible in vivo.	[134]