Table 1.

Summary of photo-crosslinking conditions of silk fibroin and other proteins.

Proteins	Crosslinking Sites	Solution/Ink (mg/mL)	Photoinitiators	Light Source	Exposure Distance	Exposure Time	Refs
Silk fibroin	Tyrosine (~5.3 mol%) a	75 (+100 Resilin)	Ru(II), 5 mM APS, 28 mM	250 W white	N/A	120 + 60 s (Two sides)	[59]
		~300	Ru (II), 0.16–10 mM APS, 20, 28, 100 mM	250 W white	N/A	120 + 60 s (Two sides)	[58]
		~20	Ru(II), 0.5 mM APS, 5 mM	400–450 nm 30 mW/cm2	N/A	3 min	[51]
		10–50	Riboflavin (0.1 mM) HRP (10 U/mL)	365 nm 300 W/m2	N/A	30 min	[79]
		50	Riboflavin 5′-monophosphate, 2 mM	450 nm (×3 leds) 18.7 mW/cm2	N/A	~60 min	[54]
	Methacryloyl	100–300	LAP, 0.2%	365 nm 30 mW/cm2	N/A	N/A	[49]
		100–300	LAP, 0.2%	365 nm 3.5 mW/cm2	N/A	~5 s (each layer)	[80]
		100–300	LAP, 0.6%	365 nm	N/A	~5 s (each layer)	[81]
Gelatin/Collage	Tyrosine (~0.9%) a	10, Gel-MA/ 0.6, Collagen	Ru(II), 0.2–2 mM APS, 2–20 mM	400–450 nm 3–100 mW/cm2	N/A	15 min	[82]
		100–175, gelatin	Ru(II), 1 mM SPS, 20 mM	600 W white	150 mm	30 s	[65]
Fibrin	Tyrosine (4.9%, β-chain; 5.6%, γ-chain; 0.65%, α-chain)	3	Ru(II), 2 mM SPS, 43 mM	458 nm 28 mW/cm2	30 mm	10 s	[67]
		100, 150	Ru(II), 2 mM SPS, 20 mM	600 W white	150 mm	20 s	[69]
GB1-resilin polyprotein	Tyrosine (~6%) a	200	Ru(II), 0.2 mM APS, 50 mM	200 W white	N/A	30 s	[64]
Rec1-resilin	Tyrosine (~6%) a	200	Ru(II), 0.2–2 mM APS, 10 mM	600 W white	150 mm	20 s	[62]
Mussel adhesive proteins	Tyrosine (~20%) a	100–300	Ru(II), 2 mM SPS, 10–30 mM	460 nm 1200 mW/cm2	20 mm	60 s	[83]

Ru(II), tris(2,2-bipyridyl)dichlororuthenium(II) hexahydrate; LAP, lithium phenyl (2,4,6-trimethylbenzoyl) phosphinate; SPS, sodium persulfate; APS, ammonia persulfate; Gel-MA, methacryloyl gelatin; HA, hyaluronic acid; HRP, horseradish peroxidase; N/A, not applicable; ^a molar ratio of amino acid residues.