Influence of telopeptides on the structural and physical properties of polymeric and monomeric acid-soluble type I collagen

Currently two factors hinder the use of collagen as building block of regenerative devices: the potential antigenicity, and limited mechanical strength in aqueous environment. Polymeric collagen is naturally found in the cross-linked state and is mechanically tougher than the monomeric, cross-link-free (acid-soluble) collagen ex vivo. The antigenicity of collagen, on the other hand, is mainly ascribed to inter-species variations in amino acid sequences, which are primarily located in the non-helical terminal telopeptides. Although these can be removed through enzymatic treatment to produce atelocollagen, the effect of telopeptide removal on triple helix organization, amino acidic composition and thermal properties is often disregarded. Here, we compare the structural, chemical and physical properties of polymeric and monomeric type I collagen with and without telopeptides, in an effort to elucidate the influence that either covalent crosslinks or telopeptides possess. Circular dichroism (CD) was used to examine the triple helical conformation and quantify the denaturation temperature (Td) of both monomeric collagen (36.5 {\deg}C) and monomeric atelocollagen (35.5 {\deg}C). CD measurements were combined with differential scanning calorimetry (DSC) in order to gain insight into the triple helix-to-coil thermal transition and shrinkage temperature (Ts) of polymeric atelo collagen (44.8 {\deg}C), polymeric collagen (62.7 {\deg}C), monomeric atelo collagen (51.4 {\deg}C) and monomeric collagen (66.5 {\deg}C). Structural and thermal analyses were combined with high pressure liquid chromatography (HPLC) to determine the content of specific collagen amino acidic residues used as markers for the presence of telopeptides and mature crosslinks.