An Atomic Force Microscopy Study of Ordered Molecular Assemblies and Concentric Ring Patterns from Evaporating Droplets of Collagen Solutions

Abstract

Ordered molecular assemblies spontaneously appeared from evaporating droplets of collagen solutions on glass substrates. Nanoscopic structures of the assemblies were examined using an atomic force microscope; well aligned collagen molecules oriented their ends toward the assembly surface and formed layered structures for concentrations >0.05 mg/mL, while the molecules, mostly curved, lay for concentrations 5 mg/mL, concentric ring patterns additionally appeared in the assemblies; each ring consisted of multilayers of well-aligned tilting collagen molecules. The color of the rings alternatingly changed from blue to orange when using a color-sensitive plate. The ring width increased from 3 to 120 μm with increasing collagen concentration and also increased toward the center of the patterns. The observations of temporal and spatial evolution of ...