Double-strand cleavage of DNA by a polyamide-phenazine-di-N-oxide conjugate.

Phenazine and its derivatives have been widely applied as nucleic acid cleavage agents due to active oxygen activating the C-H bond of the substrate. However, diffusion of oxygen radicals limits their potential applications in the DNA-targeted metal-free drug. Introduction of groove binder moiety such as polyamide enhanced the regional stability of radical molecules and reduced cytotoxicity of the drugs. In this work, we described the design and synthesis of a polyamide-modified phenazine-di-N-oxide as a DNA double-strand cleavage agent. The gel assays showed the hybrid conjugates can effectively break DNA double strands in a non-random manner under physiological conditions. The probable binding mode to DNA was investigated by sufficient spectral experiments, revealing weak interaction between hybrid ligand and nucleic acid molecules. The results of our study have implications on the design of groove-binding hybrid molecules as new artificial nucleases and may provide a strategy for developing efficient and safe DNA cleavage reagents.

Effects of ethanol-wet bonding technique on root dentine adhesion.

OBJECTIVE: To investigate the effects of ethanol-wet bonding on the adhesion of experimental hydrophobic and commercial hydrophilic adhesives to root dentine. METHODS: A total of 43 single-rooted integrated human premolars were selected and sectioned. Of the 86 initially obtained specimens, 66 were randomly and equally divided into water-wet bonding and ethanol-wet bonding groups (n = 33). The specimens of each group were subdivided into three subgroups (n = 11) based on different adhesives: two experimental hydrophobic adhesives (Bis-GMA/TEGDMA, BT; and UDMA/TEGDMA, UT) and one commercial hydrophilic adhesive (Adper™ Single Bond 2, SB). The root surfaces were ground, acid-etched and rinsed and resin composite applied. After storing in distilled water for 24 h at 37°C, the shear bond strength (SBS) of each specimen was measured. A sample from each subgroup was randomly selected and prepared for scanning electron microscopy (SEM) analysis. The remaining 20 specimens were used in the contact angle (CA) experiment, and the values of CA were measured. SBS was analysed with two-way ANOVA/Tukey's multiple comparison test and CA with independent sample t test. RESULTS: A significant increase in SBS to root dentine was observed in the ethanol-wet bonding group compared with the traditional water-wet bonding group. The experimental hydrophobic adhesives (UT group) with ethanol-wet bonding presented the highest SBS (22.44 ± 3.32 MPa). CA increased significantly after the dentine surfaces were dried, especially for the water-saturated group. CONCLUSION: The adhesion to root dentine surfaces with ethanol-wet bonding may be superior to water-wet bonding.