Vibrational circular dichroism spectroscopy as a probe for the detection of collagen fibril and fibrillation in solution

Abstract

The detection of collagen fibrils and fibrillation is crucial for tissue regeneration, biomedical applications of collagen, and for studying the interaction of small molecules with the collagen fibrils in the development of therapeutics for collagen-based diseases. At present, collagen fibrillation is probed by high-value microscopic techniques, which limits real-time monitoring of collagen fibril growth and measurement only in dry form. In this context, a quick sensing method is necessary for detecting these fibrils, especially monitoring fibril growth in solution. Herein, we show that vibrational circular dichroism (VCD), a growing spectroscopic technique, can probe collagen fibrils in aqueous solutions by generating an enhanced amide I VCD signal (intensity) compared to monomer. Unlike regular protein VCD measurements, VCD of collagen fibrils require a very low concentration (5 mg/mL) of collagen and can be probed in a very short time (∼10 min). Moreover, VCD responds to the diameter and height of collagen fibrils as evidenced by an increased VCD intensity (close to 103) with pH and NaCl, making VCD a sensitive tool for monitoring the growth of the fibril diameter and height. VCD was also found to be suitable for detecting the time-dependent increase in fibril diameter under fibrillation conditions. Because no other probe is presently available for rapid detection of collagen fibrils in solution form, the ability of VCD to rapidly probe collagen fibrillation in solution and in real-time opens a new way of studying collagen fibrillation in different fields and applications.