Collagen hydrogel microstructure depends on the protein solid content, incubation temperature, type and concentrations of ions as well as the pH. This paper will summarize our recent development of the multiphoton microscopy (MPM) optical imaging method to study the effect of these different physicochemical parameters on the micro-structural assembly of collagen within the three-dimensional (3D) hydrogels. The soft hydrated materials prepared have all been studied non-invasively and in situ. An interesting recent finding includes a strong potential of divalent anions to modulate the type of microstructure formed within collagen hydrogels. For example, in a phosphate-only buffer, when phosphate concentration is 30 mM, the fibers formed are about 1 �m in length as detected with second harmonic generation contrast (figure 1). Evidently, 60 mM phosphate induces an increase in the fibers' length concomitantly leading to a micro-structural heterogeneity within the collagen hydrogel. A complete shift to about 45 �m fiber takes place when phosphate concentration is 160 mM. The pore size also increases from about 5 �m in the hydrogels formed at 30 mM phosphate to over 24 �m in the hydrogels formed at 160 mM phosphate. Adding 150 mM sodium chloride in a 30 mM phosphate buffer to polymerize collagen into a hydrogel at 37 �C does not lengthen collagen fibers. Our methods developed and the data obtained remove guesswork from engineering collagen-based materials for various applications.Figure 1

Multiphoton microscopy optical imaging reveals many different structural features of fibrous collagen hydrogels in situ

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.