An improved method for the quantification of soluble collagen in biological samples, cultured cells and foodstuff.

Collagen is one of the most abundant proteins in connective tissues and internal organs of mammals. Collagen provides the tensile strength of the extracellular matrix, and is classified into several structurally and genetically distinct types. All collagens consists of molecules with three polypeptide chains, arranged in a triple helical conformation.

Current methods for collagen quantification involve drastic hydrolysis protocols using acids or bases, based on quantification of hydroxyproline, an amino acid typically found in collagen. However, these strategies suffer from safety issues, a long and laborious workflow, and/or lack of specificity. Other methods take advantage of dye binding to specific amino acids of collagen, but these assays are less sensitive and selective.

We recently developed a soluble collagen quantification assay, which is based on an enzymatic reaction, where collagen is specifically digested into peptides. Subsequently, the collagen peptides are labeled with a fluorescent probe. The fluorescence intensity is proportional to the amount of soluble collagen in the sample. This method provides a simple, safe and sensitive way for measuring soluble collagen in various sample types. Our assay does not require the use of strong acids or bases and thus safer than current methods.

We show that our method is useful for the quantification of soluble collagen extracted from soft tissues, cultured cells, serum samples, collagen in food, and purified collagens of various sources. The assay is capable of detecting purified collagen types I-V.