Application of Atomic Force Microscope: A Comprehensive Approach for Determining Nanomechanical Characteristics of Biomaterials Using as Scaffolds in Tissue Engineering

Due to the fact that mechanical properties in macroscale cannot respond to that of cell wall features, it has become important to investigate nanomechanical characteristics of scaffold materials and make suitable modifications if needed. Conventional methods of mechanical testing cannot characterize the spatial distribution of material, with non-uniform stiffness, at nanoscale. One of the important methods of nanoscale testing is the force mapping using the atomic force microscope. In the present study, A comprehensive approach was developed to determine and characterize surface distribution of elastic modulus for soft biomaterials at nanoscale. Elastic modulus has been determined for collagen fibers, modified with different percentage of bio-glass nonoparticles, 0%, 30% and 60%, by applying tiny forces (1 nN). The experiments are carried out in phosphate buffer saline (PBS) pH ~ 7, to mimic the physiological environment. The scanning was performed at two different spots for each sample and three different scan sizes to investigate the large scale and short scale heterogeneity, respectively. Deep-lying structures have been sensed by varying applied load (2 nN). Our results are in agreement with previous reports. The results show increasing elasticity with increase of bioglass in collagen samples. Yet adding more bioglass decreases the stiffness of collagen fibers to the point where they become difficult to handle. Samples appear to be strongly heterogeneous with increasing the scan size. The depth sensing measurements manifest higher elasticity which reflects the lower degree of freedom in the deep-lying structures.