. 2021 Mar 17;10(9):2002026. doi: 10.1002/adhm.202002026

Table 2.

Overview of PGS used in 3D printing approaches. Printing techniques are separated into extrusion‐based and laser‐based methods

Printing technique		Material combination	Mechanical properties	Cell response	Special features	Proposed application	Ref.
Extrusion‐based	commercially available 3D filament printer (Revolution XL, Quintessential Universal Building Devices) modified for syringe extrusion	Photocurable PGSA combining a ratio of 10:90 of Low molecular weight PGS, M _n = 5.78 kDa High molecular weight PGS, M _n = 6.32 kDa	Depending on printing density ^a) : Low density E‐modulus: 310 kPa Tensile strength: 120 kPa Failure strain: 40% Medium density E‐modulus: 350 kPa Tensile strength: 210 kPa Failure strain: 67% High density E‐modulus: 480 kPa Tensile strength: 330 kPa Failure strain: 70%	No cytotoxic response in contact with NIH 3T3 fibroblasts, increased cell proliferation within 4 d of culture	Rapid fabrication of spatially complex, elastomeric scaffolds Multiscale structures, supporting cell cultures, replicating native tissue shapes	Complex biocompatible, elastomeric tissue replacements (Soft TE)	^[ ²³¹ ^]
		Specific functionalized photocurable Nor‐PGS with thiol–ene click chemistry	Depending on thiol/norbornene ratios (N): N = 0.5 E‐modulus: 110 kPa Tensile strength: 260 kPa Failure strain: 240% N = 0.75 E‐modulus: 340 kPa Tensile strength: 690 kPa Failure strain: 200% N = 1 E‐modulus: 400 kPa Tensile strength: 790 kPa Failure strain: 170%	No cytotoxic response in contact with NIH 3T3 fibroblasts, increased cell proliferation within 8 d of culture	Tunable mechanical properties and degradation rates Fast cross‐linking (< 1 min) under UV‐light	Elastomeric, biodegradable and cytocompatible scaffolds for soft tissue applications	^[ ⁵⁸ ^]
	Commercially available fused depositioning system (HTS‐400; Fochif Mechatronics Technology)	Neat PGS with NaCl (NaCl‐PGS) at a ratio of PGS:NaCl = 1:2	Depending on used needle gauge (G): G = 21 (Ø = 500 µm) E‐modulus: 150.7 kPa Tensile strength: ≈80 kPa Failure strain: ≈40% G = 23 (Ø = 300 µm) E‐modulus: 239.4 kPa Tensile strength: ≈90 kPa Failure strain: ≈30%	Cytocompatible, biocompatible and biodegradable in vivo after subcutaneous and epicardial implantation in male Sprague Dawley rats Thickening of the LV wall and attenuated LV dilatation after 28 d postimplantation of 3D‐printed PGS patches	Similar mechanical properties to those of native myocardium Carrier material (salt) can be easily replaced by or combined with other additive materials (nanoclays, graphene, carbon nanotubes) to fabricate thermosetting composites	Used in a vapo‐mechanical sensor and soft actuator or as a myocardial patch	^[ ³¹ ^]
		PGS:PCL combination in a ratio of 9:1 mixed with NaCl (NaCl‐PGS/PCL) at a 1:2 weight ratio (PGS/PCL : NaCl)	Neat PGS E‐modulus: 190.1 kPa Tensile strength: 62.2 MPa Failure strain: 28.9% Neat PCL E‐modulus: 31.5 MPa Tensile strength: 3.3 MPa Failure strain: 475.0% PGS/PCL E‐modulus: 748.5 kPa Tensile strength: 302.7 kPa Failure strain: 57.3%	Epicardial implantation in male Sprague Dawley rats showed preserved heart function, increased LV wall thickness, reduced infarct size, promoted vascularization, induced tissue repair by recruiting M2 macrophages, and inhibited myocardial apoptosis	3D‐printed PGS–PCL scaffold is responsive to rolling, folding, and compression, making it suitable for minimally invasive delivery via a catheter or mini‐thoracotomy	Potential for treating multiple cardiovascular diseases (CTE)	^[ ³⁷ ^]
	Combination of a DIW‐3D printer (HTS‐400; Fochif Mechatronics Technology) and a rotary receiver	Neat PGS with NaCl (NaCl–PGS) at a ratio of PGS:NaCl = 1:2 combined with an electrospun gelatin fiber mesh post‐printing	Mechanical properties after 12 weeks in vivo implantation with and without cells: Without cells E‐modulus: ≈2.40 MPa With cells E‐modulus: ≈8.00 MPa Native trachea cartilage E‐modulus: ≈11.5 MPa	Chondrocytes from auricular cartilage of New Zealand white rabbits showed excellent cell proliferation without noticeable apoptosis within 4 d of culture; In vivo results in nude mice showed an increased DNA, GAG as well as collagen content after 12 weeks of implantation	Four‐axis printing system for hierarchical tubular structures Controllable mesh structure, radial elasticity, good flexibility, as well as luminal patency	Potential for tracheal cartilage reconstruction	^[ ¹³⁸ ^]
	Commercially available 3D‐Bioplotter Developer Series (EnvisionTec)	PGS/PCL combination in a ratio of PGS:PCL = 1:1 combined with BG particles and an electrospun PGS/PCL fiber mat postprinting	Depending on the amount of incorporated BG particles: PGS/PCL + fiber mat E‐modulus: 250 MPa Maximum load: 6 N Failure length: 1.5 mm PGS/PCL/5wt%BG + fiber mat E‐modulus: 241 MPa Maximum load: ≈4 N Failure length: ≈1.4 mm PGS/PCL/10wt%BG + fiber mat E‐modulus: 311 MPa Maximum load: ≈3.5 N Failure length: ≈0.6 mm	NIH 3T3 fibroblasts showed no cytotoxic response with an improved cell proliferation within 7 d of culture	Combination of 3D printing and electrospinning Multiscale 3D porosity Control over degradation and mechanical properties via BG incorporation	Potential for tendon and ligament TE applications	^[ ⁴⁶ ^]
	Commercially available 3D‐Bioplotter Allevi 2	Photocurable PGSA with chemically sintered Zn powder in various ratios	Depending on the amount of incorporated Zn powder: Conductivity: up to 11.8 mS m^‐1 Compression modulus: up to 1179.5 kPa E‐modulus: up to 1099.9 kPa	No cytotoxic response in contact with C2C12 myoblasts as well as in in vivo studies using Wistar rat models	Highly elastic as well as bendable and electrically conductive Biocompatible	Bio‐integrated electronics in wearable electronics, electronic skin, robotics, implantable electronics and human–machine interfacing	^[ ¹⁶¹ ^]
Laser‐based	DLP‐AM system developed by the Cheng lab at the National Taiwan University of Science and Technology	Photocurable PGSA with an altered degree of acrylation (30, 15, and 7%) combined with PCLDA (PGSA: PCLDA = 2:1) or PEGDA (PGSA: PEGDA = 1:1)	Depending on the degree of acrylation and mixing ratio: PGSA7 E‐modulus: 0.12 MPa Tensile strength: 0.10 MPa Failure strain: 121.23% PGSA15 E‐modulus: 1.55 MPa Tensile strength: 0.63 MPa Failure strain: 46.95% PGSA30 E‐modulus: 5.10 MPa Tensile strength: 1.36 MPa Failure strain: 28.43% PEDGA E‐modulus: 18.98 MPa Tensile strength: 3.19 MPa Failure strain: 21.50% PGSA7‐PEGDA E‐modulus: 4.25 MPa Tensile strength: 0.80 MPa Failure strain: 21.29% PGSA15‐PEGDA E‐modulus: 7.58 MPa Tensile strength: 0.91 MPa Failure strain: 13.63% PGSA30–PEGDA E‐modulus: 10.54 MPa Tensile strength: 1.10 MPa Failure strain: 12.96%	Not conducted in this study	Printing of polymers with similar composition, but quite different mechanical and degradation properties, in a continuous motion via the instantaneous blending of the polymers at various ratios	Potential for multiple TE applications	^[ ⁶² ^]
			PCLDA E‐modulus: 4.35 MPa Tensile strength: 0.58 MPa Failure strain: 15.34% PGSA7‐PCLDA E‐modulus: 1.42 MPa Tensile strength: 0.19 MPa Failure strain: 22.39% PGSA15‐PCLDA E‐modulus: 2.85 MPa Tensile strength: 0.20 MPa Failure strain: 11.28% PGSA30‐PCLDA E‐modulus: 7.00 MPa Tensile strength: 0.69 MPa Failure strain: 14.08%
	Femtosecond DLW using 2PP with a PHAROS femtosecond Yb:KGW laser (Light Conversion Ltd)	Photocurable mAcr‐PGS of Low molecular weight PGS, M _w = 5,420 g mol^‐1 High molecular weight PGS, M _w = 17,340 g mol^‐1	Depending on the degree of methacrylation (N) and molecular weight: N = 30% Low M _w E‐modulus: ≈0.50 MPa Tensile strength: ≈0.80 MPa High M _w E‐modulus: ≈0.90 MPa Tensile strength: ≈0.60 MPa N = 50% Low M _w E‐modulus: ≈1.50 MPa Tensile strength: ≈0.90 MPa High M _w E‐modulus: ≈1.50 MPa Tensile strength: ≈0.90 MPa N = 80% Low M _w E‐modulus: ≈6.80 MPa Tensile strength: ≈3.80 MPa	Cytocompatible with human dermal fibroblasts, human adipose‐derived stem cells (ADSCs) and human coronary artery SMCs, enhanced cell proliferation during the 7 and 14 d of culture, respectively	Minimum feature sizes of ≈10 µm Tunable physical properties and compatible with diverse cell types	Potential for multiple TE applications both in vitro and in vivo	^[ ¹⁶⁵ ^]
	In house designed micro SLA set‐up	Photocurable mAcr‐PGS with altered degree of methacrylation (N = 0.22–1.00)	Mechanical compression testing of a produced NGC (N = 0.75^b): Max compression: 0.57 mm Compression at break: 11.4% Stiffness: 3.2 MPa Suture retention strength: 12.3 MPa	Neuronal NG108‐15 cells as well as primary SCs from male Wistar rats showed improved neuronal and glial cell growth in vitro	High conduit flexibility, resistance to kinking and ability to withstand suturing Intricate micro‐and macroscopic structure	Potential for nerve conduit guidance (nerve TE)	^[ ¹⁶² ^]
				In vivo: an increased regeneration of axons, oriented axonal growth without an increase of neuropathic pain in comparison to native nerve grafts
	DLP‐based 3D printing using a DMD chip (Texas Instruments)	Photocurable PGSA combined with altered amounts of PEDGA (1%, 5% and 10%)	Depending on light exposure time (in s) and printed structure (single or double network): Single network 30s E‐modulus: 11.91 kPa Tensile strength: 5.92 kPa Tensile strain: 62.58% Single network 60s E‐modulus: 47.66 kPa Tensile strength: 14.11 kPa Tensile strain: 43.31% Double network E‐modulus: 32.09 kPa Tensile strength: 15.08 kPa Tensile strain: 64.18%	HUVECs showed excellent viability (>90%) within 7 d of culture	Enhanced toughness by introducing soft sacrificial beams to absorb the energy during tensile testing while the hard segments maintained the overall shape of the structure	Specifically optimizable for different biomedical applications (soft TE)	^[ ¹⁶⁶ ^]
	DLP‐based 3D printing using an Ember desktop 3D printer (Autodesk) with a built‐in light‐emitting diode projector	Photocurable PGSA with different degrees of acrylation mixed with 1wt% dipehyl (2,4,6‐trimethylbenzoyl) phosphine oxide photoinitiator	Mechanical tensile testing on films: Degree of acrylation 16.7% E‐modulus: 192.3 kPa Tensile strength: 460.2 kPa Tensile strain: 239% Degree of acrylation 35.2% E‐modulus: 859.0 kPa Tensile strength: 326.8 kPa Tensile strain: 39% Degree of acrylation 35.2% E‐modulus: 3668.7 kPa Tensile strength: 919.1 kPa Tensile strain: 26% After 4 min UV cross‐linking E‐modulus: 226.8 kPa Tensile strength: 556.9 kPa Tensile strain: 244% After 24 h thermal cross‐linking E‐modulus: 3097.6 kPa Tensile strength: 1273.3 kPa Tensile Strain: 42%	Not conducted in this study	Elastomeric properties and limited swelling Thermal postprocessing provided predictable control of mechanical properties and degradation behavior	Potential for multiple TE applications	^[ ¹⁶⁷ ^]

^{^a)}

Printing density referred to as the amount of interior volume designated to be occupied by material (fill density setting, in Slic3r), including 30% for low density, 45% for medium density, and 60% for high density; ^b)NGC = nerve guidance conduit, Hounslow mechanical analysis was conducted along the axial direction of the NGC.