Total protein contents [% (w/w)] (n = 3) derived from the conversion of the measured nitrogen content by the specific nitrogen-to-protein conversion factors for gelatin (derived from Jones (JF = Jones factor)), collagen (COL) type I, III, IV, fibronectin (FN), and laminin (LN) (derived from UniProt⁶⁰) as well as for human skin collagen (derived from Bornstein and Piez⁶¹ as well as Miyahara et al.⁶²).

	Jones factor	COL			FN	LN	Human infant skin
		I	III	IV			Bornstein and Piez61	Miyahara et al.62
ECM	56 ± 4	53 ± 4	54 ± 4	57 ± 4	59 ± 4	57 ± 4	55 ± 4	57 ± 4
clickECM	58 ± 4	54 ± 4	55 ± 4	59 ± 4	61 ± 4	59 ± 4	57 ± 4	59 ± 4