Collagen Obtained from Leather Production Waste Provides Suitable Gels for Biomedical Applications

Abstract

Collagen and its derivates are typically obtained by extracting them from fresh animal tissues. Lately, however, there has been an increased interest in obtaining collagen from other sources, such as waste material, because of the growing trend to replace synthetic materials with sustainable, natural counterparts in various industries, as well as to ensure a rational waste revalorization. In this paper, collagen was obtained from non-tanned waste of leather production, taken at different stages of the production process: limed pelt, delimed pelt, and fleshings. A stepwise extraction through acid hydrolysis in 0.5 M acetic acid and subsequent precipitation with NaCl lead to collagen-containing protein extracts. The highest collagen yield was achieved in extracts based on delimed pelt (2.3% m/m after a first extraction round, and an additional 1.4% m/m after the second round). Hyp/Hyl molar ratios of 10.91 in these extracts suggest the presence of type I collagen. Moreover, gels based on these collagen extracts promote adhesion and spreading of HEK293 cells, with cells grown on collagen from delimed pelt showing a larger nuclear and cell expansion than cells grown on traditional bovine tendon atelocollagen. This suggests that these collagen gels are promising natural biomedical carriers and could be used in a wide range of medical and cosmetic applications.

Keywords: cell culture; collagen; collagen extraction; leather production wastes.

Figure 1

Hydroxyproline yield from different types of waste, expressed as a % (mass ratio) of the initial waste mass.

Figure 2

Collagen gels obtained after dialysis: (A)—limed pelt (group I), (B)—delimed pelt (group IV).

Figure 3

HEK293 cells adhesion and morphology on (A) synthetic (polystyrene) and biomimetic (B) bovine atelocollagen, (C) bovine collagen (limed pelt), and (D) bovine collagen (delimed pelt) treated surfaces. Pappenheim staining. Bar 20 µm.

Figure 4

Morphometric parameters of the HEK293 cell line. (A) Nuclear area (Sn). p values were calculated by ANOVA with Tukey’s test. * p < 0.05—positive control vs. collagen from delimed pelt. (B) Cell area. p values were calculated by ANOVA with Tukey’s test. * p < 0.05—negative control vs. positive control, ## p < 0.05—positive control vs. collagen from delimed pelt. (C) p values were calculated by ANOVA with Tukey’s test. * p < 0.05—negative control vs. positive control, # p < 0.05—positive control vs. collagen from limed pelt. For all graphs: white bar: negative control; grey bar: positive control; diagonally striped bar: collagen from limed pelt; vertically striped bar: collagen from delimed pelt.