As we can see from the SEM images with low magnification, the cell concentration with N 8.67% (Figure 5b,e) is significantly less than that with N 9.28% (Figure 5c,f), which is consistent with the results given by Figure 4 and Figure 5a,d. And, the adhered cells all spread flat with richer pseudopod and microvilli, as shown at a high magnification. These results add to growing evidence that the increase of nitrogen content
promoted cell adherence and growth. The ability of substrates to promote adhesion of cells depends on how well they adsorb proteins from the culture medium that interact with receptors on the cell surface [31]. Adsorption of proteins in an active conformation, in turn, is likely to be affected by the functional groups of the substrate. All proteins have NH2 and COOH groups at the ��-Nicotinamide solubility dmso ends, where the NH tends to be positively charged and the COOH negatively charged [32]. Thus, a surface with an organized arrangement of functional groups can act as a site for cell growth.
The formation of functional sp 2 C-N and sp 3 C-N bonds on the N+-bombarded MWCNTs by N ion beam bombardment induces polarization at Cediranib the surface due to the difference in electronegativity between carbon and nitrogen [33]. In addition, from the XPS results (Figure 1d,e,f), it is clear that with the increase of nitrogen concentration, the ratio of the sp 2 C-N bond decreases and the sp 3 C-N bond increases while the unsaturated degree of the N bond increases. Therefore, the number of protein attached on the material’s surface increases with increasing unsaturated degree of the N bond, and adhesion of cells are promoted. Blood platelets are anucleated cells that originate from bone marrow megakaryocytes and circulate in the blood as
sentinels for vascular integrity [34]. Platelets play a vital role in hemostasis; however, derangement of their functions can lead to thrombosis, which is a leading cause of death and disability in the developed world [35]. Figure 6 displays the statistical results of the platelets adhered on the surfaces of three N+-bombarded MWCNTs with different nitrogen content and the glass with and without methylsilicone oil. Each value represents the mean ± SD for five measurements. And, each experiment is performed three times. From the Isotretinoin average platelet adhesion rates, it is observed that the number of adherent platelets decreases with increasing nitrogen concentration. In addition, as shown in Figure 7c,d, the platelets show less pseudopodium as demonstrated by the isolated and nearly round state when the nitrogen concentration is higher. The morphology of the red blood cell (RBC) on N+-bombarded MWCNTs is perfect round. It is demonstrated that higher nitrogen concentration is contributive to the improvement of hemocompatibility. Figure 6 Platelet adhesion rates on the different materials. Figure 7 SEM images of platelet adhesion testing for N + -bombarded MWCNTs. Nitrogen contents are (a, b) 8.67% and (c, d) 9.28%.