Lutein, a carotenoid found in numerous plants and the human eye, demonstrates the capacity to bundle collagen fibrils.

Collagen fibrils serve as the building blocks of the extracellular matrix, providing a resilient and structural framework for tissues. However, the bundling of collagen fibrils is of paramount importance in maintaining the structural integrity and functionality of various tissues in the human body. In this scenario, there is limited exploration of molecules that promote the bundling of collagen fibrils. Investigating the interactions of well-known carotenoids, commonly associated with ocular health, particularly in the retina, with collagen presents a novel and significant area of study. Here, we studied the influence of lutein, a well-known carotenoid present in many plant tissues and has several biological properties, on the structure, thermal stability, self-assembly, and fibrillation of collagen. Fibrillation kinetics and electron microscopic analyses indicated that lutein did not interfere with fibrillation process of collagen, whereas it enhances the lateral fusion of collagen fibrils leading to the formation of compact bundles of thick fibrils under physiological conditions. The hydrophobic and hydrogen bonding interactions between lutein and collagen fibrils are most likely the cause of the bundling of the fibrils. This study establishes the first investigation of collagen-carotenoid interactions, showcasing the unique property of lutein in bundling collagen fibrils, which may find potential application in tissue engineering.