Atomic-level surface characterization of organic and inorganic materials

Abstract

Type I collagen is a major extracellular matrix component and its hierarchical structure plays an essential role in the regulation of cellular behavior. Here, I have analyzed the changes in the morphological, chemical, and mechanical properties of collagen fibrils induced by acidic and thermal treatments and the influence on the cellu-lar response of MC3T3-E1 cells. Morphological changes induced by the disintegration of the fibrillar structure of collagen were observed using atomic force microscopy. The changes in the surface chemistry due to the disas-sembly of native collagen fibrils were observed using time-of-flight secondary ion mass spectroscopy (ToF-SIMS). ToF-SIMS spectra were very sensitive to changes in the molecular configuration of the collagen fibrils induced by acidic and thermal treatments due to the extreme surface specificity. In addition, ToF-SIMS showed clear and reproducible changes in the surface amino acid composition corresponding to the acidic and thermal treatments of collagen fibrils. Based on the quantitative map of surface elastic modulus measured by contact-resonance force microscopy, acid and thermally treated collagen showed a lower elastic modulus than native collagen fibrils. Compared with native collagen fibrils, reduced cell spreading and decreased viability of MC3T3-E1 cells were observed on both the acid and thermally treated collagen. Bone is a hierarchically organized biocomposite of organic (collagen) and inorganic (calcium phosphate, mostly hydroxyapatite) materials. The precise structural dependence and chemical correlation between mineral and collagen fibril are critical to unique characteristics of bone such as resilience and strength. Therefore, in ad-dition to the study of structural, chemical, and mechanical properties of collagen fibril, initial growth stages of hydroxyapatite was investigated using medium energy ion scattering spectroscopy (MEIS) for the understanding of bone formation mechanism. The quantitativ...