Open Access

ARTICLE

AFM and Nanoindentation Studies of Bone Nodules on Chitosan-Polygalacturonic Acid-Hydroxyapatite Nanocomposites

R. Khanna^1,2, D. R. Katti¹, K. S. Katti¹

1 Department of Civil Engineering, North Dakota State University, Fargo ND 58105
2 work performed at NDSU, Currently at Department of Biomedical Sciences College of Life and Health Sciences JSPS fellow, Chubu University

Computer Modeling in Engineering & Sciences 2012, 87(6), 530-556. https://doi.org/10.3970/cmes.2012.087.530

Abstract

Here we report a new in situ nanoindentation technique developed to evaluate the composite mechanical behavior of cell-biomaterial construct under physiological conditions over the time scale of bone nodule generation. Using this technique, mechanical behavior of osteoblast cell-substrate interfaces on tissue engineered materials (chitosan-polygalacturonic acid-nanohydroxyapatite (CPH) films) is investigated. Mechanical behavior of cells in the elastic regime over the time scale of cell adhesion (1 day), proliferation (4 days), development (8 days) and maturation (22 days) of bone nodules is evaluated. Our results indicate that the elastic properties of flat cells are higher (indicating stiffer response, after 4 days, as compared to the round cells after 1 day and oriented cells after 8 days. Elastic properties of cells ( ~ 5-12 MPa), soaked CPH films ( ~ 10-20 MPa) and that of cell-CPH composites ( ~ 3-9 MPa) fall in the same order of magnitude. A similar range of elastic properties of cell-CPH composites are measured over time, implying that unique interactions between cells and CPH films are maintained that may provide a favorable mechanical environment to growing cells and bone nodules. Atomic Force Microscopy (AFM) imaging studies on individual cells reveal that the cells respond to local changes in substrate topography (as a result of substrate swelling) by modulating their shapes and various focal adhesions. Overall, CPH films provide a favorable microenvironment for cell organization and bone nodule regeneration that regulates the mechanical behavior of cell-substrate interactions.

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