| Chiral molecules are referring to, a group of molecules which have the same composition but the different space configuration. They have the same physical properties, Also chemical properties are similar, due to the different spatial configuration, while its biological performance might be quite different. In this paper, two systems were designed to immobilized different chiral sodium cystine on the surface of TiO2 films,thus to observe the effects on nitric oxide released and blood compatibility.First:The TiO2 films were first deposited on silicon (100) wafers using an unbalanced magnetron sputtering system, then, polydopamine was deposited on the surface, and finally chiral sodium cystine was immobilized. Contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to characterization the modified samples, Biological properties of the modified samples were evaluated by detecting albumin adsorption, catalytic release of NO and platelet adhesion experiment in vitro, Morphology of the surfaces were observed by SEM, It shows lots of granular protuberance on the surface, and the size of granular protuberance increased with the layer of deposited polydopamine, While the surface morphology keeps similar after sodium cystine was immobilized. XPS results show that the N element was introduced on the surface of polydopamine, S element was introduced by sodium cystine immobilization. The surface contents of S element were 1.4% and 1.3% respectively on the surface of L-sodium cystine and D-sodium cystine immobilized surface, indicating surface S content is almost the same on both samples. The results of water contact angle show that the hydrophilicity increases after polydopamine deposition, and it is reduced after sodium cystine immobilized. The water contact angle of L-sodium cystine and D-sodium cystine immobilized surface is nearly the same. The above results show that the samples were built by system 1 successfully. Although the physical properties of different chiral sodium cystine immobilized surface are similar, there is an obvious difference in hydrophobicity between the surfaces after BSA adsorption. The reasons might be the different adsorption amount of BSA, or the conformational change of BSA. The results of NO catalyzed by both samples show that both can catalyze NO releasing steadily, while NO release rate catalyzed by the L-samples is significantly higher than that of the D-samples. Whether L-samples or D-samples have no ability to resist platelet activation in the absence of endogenous donor exist. However, when endogenous donor exists, both have the ability to inhibit platelet activation and adhesion. And the inhibition effect of the L-samples is better than that of the D-samples which suggests surfaces modified by cystine sodium with different chirality showing different biological properties.Second:Polydopamine and cystamine/dopamine crosslinking layer were alternately deposited onto the TiO2, the mole ratio of cystamine/dopamine in crosslinking is set by 1:3 and 1:5, then L- or D-cystine sodium was immobilized on the surface, thus NO generation by catalytic decomposing of GSNO combined with platelet adhesion were investigated. The results show higher NO release catalyzed by samples built by system 2 than that built by system 1, mainly because of the increase of the amount of disulfide groups by introduction of crosslinking layer, Within the same system 2, There is also a higher NO release catalyzed by L-samples than that by D samples, and the difference value increases with the amount of disulfide groups. All the above studies show that L-samples have better catalytic activities than that of D-samples. Results of in vitro platelet adhesion also confirmed that platelet activation and adhesion decrease obviously within the same condition. |
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