Heterogeneous cell mechanical properties: an atomic force microscopy study.

Atomic force microscopy (AFM) is a non-invasive microscopy to explore living biological systems like cells in liquid environment. Thus AFM is an appropriate tool to investigate surface chemical modification and its influence on biological systems. In particular, control over biomaterial surface chemistry can result in a regulated cell response. This report investigates the influence of adhesive and non-adhesive surfaces on the cell morphology and the influence of the cytoskeleton structure on the local mechanical properties. In this study, the main work concerns a thorough investigation of the height images obtained with an AFM as therecorded images provide the evolution of the mechanical properties of the cell as function of its local structure. Information on the cell elasticity due to the cytoskeleton organization is deduced when comparing the AFM tip indentation depth versus the distance between the cytoskeleton bundles for the different samples.

Characterization of dynamic cellular adhesion of osteoblasts using atomic force microscopy.

BACKGROUND: Atomic force microscopy (AFM) can be used to visualize the cell morphology in an aqueous environment and in real time. It also allows the investigation of mechanical properties such as cell compliance as a function of cell attachment. This study characterized and evaluated osteoblast adhesion by AFM. METHODS: Human bone marrow stromal cells were cultured on two types of surface to induce weak and strong cellular adhesions. RESULTS: Cells were considered as spreading if they had a flattened and lengthened shape and a cytoskeletal organization in the submembrane cytosolic region. Cell detachment demonstrated different adhesion states between adherent cells to be distinguished. The stability of the cytoskeletal fibers indicated that cells were adherent. The elastic modulus was estimated by two complementary approaches. The values deduced were between 3 x 10(2) and 2 x 10(5) Nm(-2) according to the state of cell adhesion and the approaches used to measure this elastic modulus. CONCLUSIONS: Although the results were qualitative, a relation may be deduced between the elasticity of living cells as demonstrated by cytoskeletal organization and the state of cell adhesion. The technique could be used to determine the adhesion state of an adherent osteoblast observed under AFM.

Study of two grafting methods for obtaining a 3-aminopropyltriethoxysilane monolayer on silica surface.

In order to establish a 3-aminopropyltriethoxysilane (APTES) grafting procedure with limited number of APTESs noncovalently linked to the silica surface, two different methods of grafting (in acid-aqueous solution and in anhydrous solution) were compared. The grafted surface state was investigated by atomic force microscopy (AFM). The stability of the grafting was checked at different temperatures by AFM. Continuous and plane APTES grafted surfaces were successfully prepared using both grafting preparations. The grafting in an anhydrous solution behaves homogeneously and stably compared to the grafting in an acid-aqueous solution. Moreover, with anhydrous solution, results showed that a unique monolayer of APTES was grafted.

Ti4+ to Ti3+ conversion of TiO2 uppermost layer by low-temperature vacuum annealing: interest for titanium biomedical applications.

Because of the Ti(3+) defects responsibility for dissociative adsorption of water onto TiO(2) surfaces and due to the hydroxyls influence on the biological behavior of titanium, controlling the Ti(3+) surface defects density by means of low-temperature vacuum annealing is proposed to improve the bone/implant interactions. Experiments have been carried out on Ti-6Al-4V alloys exhibiting a porous surface generated primarily by chemical treatment. XPS investigations have shown that low-temperature vacuum annealing can create a controlled number of Ti(3+) defects (up to 21% Ti(3+)/Ti(4+) at 573 K). High Ti(3+) defect concentration is linked to surface porosity. Such surfaces, exhibiting high hydrophilicity and microporosity, would confer to titanium biomaterials a great ability to interact with surrounding proteins and cells and hence would favor the bone anchorage of as-treated implants.