Atomic Force Microscopy to Investigate Collagen Fibrils.

This chapter presents a comprehensive overview of the synthesis and atomic force microscopy (AFM) imaging of collagen fibers. Collagen, a key structural protein in the extracellular matrix, plays a crucial role in tissue strength and integrity. Synthetic and in vitro assembled collagen fibers are widely used in biomedical research and regenerative medicine. The chapter begins with a description of collagen's hierarchical structure and its self-assembly mechanisms under physiological conditions. Different synthesis methods are discussed, including extraction from biological sources and recombinant production. The influence of pH, ionic strength, and temperature on fibrillogenesis is examined. AFM is introduced as a powerful tool to characterize collagen morphology at the nanoscale. PFM is also presented as an emerging mode to characterize collagen fibrils. Techniques for sample preparation, imaging in air or liquid, and data interpretation are detailed. Typical AFM outputs, such as height profiles and phase contrast, provide insight into fibril diameter, periodicity, and surface topography. Case studies illustrate the impact of processing parameters on fiber structure. Finally, perspectives on future developments in collagen imaging are discussed. We also provide guidelines.