Surface energy of implant material is one of the important factors in the process of osseointegration. How surface energy regulates the signaling pathway of osteoblasts, however, is not well understood. Cell adhesion is one of the first steps essential to subsequent proliferation and differentiation of bone cells before tissue formation. Our present study was designed to investigate how surface energy may influence the early adhesion of human alveolar osteoblasts (AOBs). Substrates applied were two groups of titanium disks: (1) hydrophobic sandblasted and acid-etched (SLA) surfaces; (2) chemically modified hydrophilic SLA (modSLA) ones. Cell morphology and cell attachment were examined by scanning electron microscopy (SEM). Defined cytoskeletal actin organization was immunohistochemically examined using confocal laser scanning microscopy. RT-PCR was applied to detect and to compare the expression of focal adhesion kinase (FAK) of osteoblasts cultured on the two groups of substrates. The attachment rates of AOBs cultured on modSLA substrates were significantly higher than the cells on SLA ones within 3 h. AOBs on modSLA developed more defined actin stress fibers after 6 h of attachment. FAK expression was comparably higher on modSLA after 6 h. Within the limitation of the current study, higher surface energy of titanium surfaces enhanced the cell adhesion in the early stage of cell response and may work through influencing the expression of adhesion-associated molecules.

In this study, the propagation mechanism of plasma jet and some bio-medical applications are investigated by two-dimensional numerical model. The key equations of plasma physics and chemistry related with plasma jet are firstly introduced. The simulation results suggest that the sheath forms near the dielectric tube inner surface, which results in the plasma channel to shrink in the radial direction inside the dielectric tube. The photoionisation of air species plays a crucial role in the transition from the localised discharge to streamer. The Penning ionisation increases the electric conductivity of the plasma channel and facilitates the formation of ring-shaped plasma bullet. For the plasma jet in the open air, electronimpact dissociation of H 2 O, electron neutralisation of H 2 O + , as well as dissociation of H 2 O by O(1D) are found to be the main reactions to produce OH. For micro plasma jet, the higher ignition voltage as the tube diameter decreased is attributed to the deceasing pre-avalanche electron density inside the tube. The simulation of plasma treatment of bacteria biofilm indicates that the mean free path of charged species in µm scale permitted the plasma penetrate into the cavity of the biofilm, and the structure of the biofilm results in the non-uniform distribution of ROS and RNS. The simulation of plasma treatment of cells immersed in liquid suggests that the HO 2 generated by plasma aqueous species is the only way for superoxide to penetrate cell membrane and damage cytosolic fumarase B.

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