Table 1.

Some extraction procedures used for collagen type I from different sources.

Animal Class	Source and Tissue Type	Pre-Treatment Method	Extraction and Purification Method	Scaffold Comparisons	Reference
Mammalian	Human-placenta	Alkaline; 0.1 M NaOH in 1:10 (w/v) ratio; 6 h stir	Acid; 0.06 M acetic acid 1:25 (w/v) overnight; NaCl 3 M pH 7 to collect supernatant; dialysis against distilled water 5 days	-Cost effective (human waste) -Safe and fast extraction method	Karami et al., 2019 [91]
	Bovine skin, bone, pericardium	Alkaline; 300 mL of 0.1 M NaOH at 4 °C 48 h; filtered 3X	Acid–enzyme; 300 mL 10 mM HCl with pepsin to solution ratio of 1:20; pH 2.0 4 °C 12 h; urea and NaCl to collect supernatant; 1 M Tris for pepsin deactivation; dialysis against 1 M phosphate buffer 4 °C 16 h	-Collagen in the purified form -Can be a substitute/replaced from the commercial collagen -Simple extraction method	Santos et al., 2013 [92]
	Rat tail	Salt; 10% NaCl 4 °C 24 h	Acid–enzyme; 0.5 M HCl and pepsin 1:50 4 °C 24 h; NaCl to collect supernatant and washed with phosphate buffer pH 7.4, 0.02 M	-Biocompatible -Induce contraction effect in in vitro model -Excellent for dental application	Techatanawat et al., 2011 [93]
	Goat tendon	Acid; 1% (v/v) acetic acid 4 °C 72 h	Acid; 1% v/v after cotton mesh filtration and dialysis against 10 mM PBS 48 h, then further dialysed against 0.05 M Na2 HPO4	-In vitro and in vivo study towards HUVEC cells showed prominent result -Good for future angiogenesis study	Banerjee et al., 2012 [94]
	Sheep tendon	Acid; 0.35 M acetic acid 4 °C 24–48 h	Acid; 0.35 M acetic acid; NaCl salting-out 4 °C 24–48 h; supernatant undergoes dialysis against Na2HPO4 and PBS 14 kDa 4 °C 72 h	-Biocompatible toward human dermal fibroblasts (HDFs) -Greater availability and wider acceptability (religious views) -Can be fabricated into porous scaffolds	Fauzi et al., 2016 [71]
Fish	Freshwater fish scales	Salt; 1.0 M NaCl, 0.05 M Tris HCl, 20.0 mM EDTA 48 h (pH7.5); demineralisation 0.5 M EDTA 48 h (pH 7.4)	Acid; 0.5 M acetic acid (pH 2.5) 48 h; NaCl (0.9 M) salting-out 24 h; resolubilised supernatant undergoes dialysis against 0.1 M acetic acid and deionised water 24 h	-Cost effective -Alternative to other collagen sources -Highly biocompatible	Pati et al., 2012 [95]
	Bighead carp fins, scales, skin, bones, and swim bladders	Alkaline; 0.1 M NaOH 1:10 (w/v) ratio; 4 °C 36 h	Acid–enzyme; 0.5 M acetic acid 0.1% (w/v) pepsin 1:10 (w/v days; NaCl to collect supernatant 2 M; dialysis against distilled water 7 kda	-Alternative to other sources of collagen -Pepsin-solubilized collagen (PSC) can be extracted	Liu et al., 2012 [96]
	Loach skin	Alkaline–salt; 10% NaCl 1:5 (w/v) 4 °C 1 h. 0.1 mol/L NaOH 1:10(w/v) 4 °C 24 h	Acid–enzyme; 0.5 mol/L acetic acid 1:30(w/v) 4 °C 24 h 5% (w/v) pepsin 2X; NaCl 0.9 mol/L to collect supernatant; dialysis against distilled water 8 kDa	-Alternative to other sources of collagen -Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) can be extracted	Wang et al., 2018 [97]
	Clown featherback skin	Alkaline; 0.1 M NaOH 1:15 (w/v) 4 °C 8 h	Acid–ultrasound; 0.5 M acetic acid 4 °C 48 h; in 30 min ultrasonication (20–80% between 10–30 min); NaCl to collect supernatant to 2.6 M; dialysis against distilled water for 2 days	-Ultrasonic application improves the extraction efficiency -Higher yield production, alternative to other collagen sources	Petcharat et al., 2020 [89]
Marine	Jumbo squid mantles	Acid; 6 M urea in sodium acetate (pH 6.8) and neutral buffer 24 h	Acid; 0.5 M acetic acid 24 h; supernatant collected for acid soluble collagen	-Acid-soluble collagen (ASC) can be extracted -Have some similar characteristics to bovine collagen	Uriarte-Montoya et al., 2010 [98]
	Jellyfish tissues	Acid; 0.5 M acetic acid	Acid–enzyme; 0.5 M acetic acid centrifuged and added pepsin (1–15 mg/mg tissue) overnight; NaCl (0.9 M) used to collect supernatant and dialysed against 0.1 M acetic acid	-Alternative to other sources of collagen -Biocompatible in in vitro testing	Addad et al., 2011 [99]
	Jellyfish and squid	Acid; 0.5 M acetic acid 1:15 (w/v) 4 °C 3 days	Acid; 0.5 M acetic acid 1:15 (w/v) 4 °C 3 days after filtration through cheesecloth; NaCl (0.9 M) and 0.05 M Tris and used to collect supernatant and dialysed against 0.1 M acetic acid 3 days and distilled water another 3 days	-Alternative to other sources of collagen -Pepsin-soluble collagen (PSC) can be extracted	Jankangram et al., 2016 [100]
Amphibian	Bullfrog fallopian tubes	Alkali; 0.1 M NaOH 4 °C 1 day	Acid–enzyme; 0.5 M acetic acid with 10% pepsin 4 °C 2 days; NaCl (0.7 M) to collect supernatant; resolubilised acid solution dialysed against 0.1 M acetic acid 1 day; distilled water 2 days	-Pepsin-soluble collagen (PSC) can be extracted -Potential alternative and supplements from other sources of collagen	Wang et al., 2011 [101]
Avian	Skin, skin dermis	Acid (acetic acid)	Acid-based extraction (acetic acid); enzymatic method (pepsin)	-Non-immunogenic and non-allergenic -Biocompatible -Can be fabricated into porous scaffolds	Peng et al., 2010, Parenteau-Bareil et al. 2011 [102,103]
	Chicken cartilage	Acid (EDTA)	Salting-out (NaCl) + ultrasound	-Increased yield production through ultrasound -Pepsin-soluble collagen (PSC) can be extracted	Akram and Zhang, 2020 [88]
	Chicken lungs	Acid salt (sodium carbonate)	Acid extraction (acetic acid) + salting-out (NaCl) + enzymatic method (pepsin) + ultrasound	-Increased yield production through ultrasound -Alternative source to mammalian collagen -Higher thermal stability	Zou et al., 2020 [87]