镁合金腐蚀研究进展(26)—镁合金表面层层组装DNA涂层耐蚀性能

    脱氧核糖核酸（deoxyribonucleic acid, DNA）是一种由核苷酸重复排列组成的长链聚合物。所谓核苷酸，是指一个核苷加上一个或多个磷酸基团；核苷则是指一个碱基加上一个糖类分子。DNA骨架是由磷酸与糖类基团交互排列而成的一种长链聚合物。

    本文首次利用DNA和聚乙烯吡咯烷酮（polyvinylpyrrolidone, PVP）在镁合金表面通过层层组装技术(layer-by-layer (LbL) assembly)构建聚电解质多层膜(PVP/DNA)_n。该涂层表现出良好的耐蚀性能和生物相容性。特别地，该涂层在浸泡模拟体液中还表现出良好的类生物矿化效果。矿化产物有助于镁合金用于骨植入材料。

    究其原因，主要可以归因于三点：（1）DNA分子中的磷酸基团可以作为钙磷产物形核生长的诱导剂；（2）DNA与PVP的静电吸引作用可以有效地将钙离子吸附于分子层间；（3）PVP可以络合钙离子形成配合物。基于以上三点构建的层层组装多层膜在骨植入材料领域有一定的应用前景。

    该项成果“In vitro corrosion resistance of a layer-by-layer assembled DNA coating on magnesium alloy（Share link）”

In vitro corrosion resistance of a layer-by-layer assembled DNA coating on.pdf

发表在国际期刊Applied Surface Science (IF4.439) (457, 2018: 49–58）。第一作者为博士生崔蓝月，通讯作者为曾荣昌教授和李硕琦博士。

Fig. 1 The schematic construction of the (PVP/DNA)_n/Mg via LbL assembly.

Fig. 2 (a–h) SEM images of the (PVP/DNA)₂₀/Mg soaked in SBF for 6, 12, 24, 48, 72, 96, 120 and 432 h; (i) EDS spectra and (j) corresponding Ca/P molar ratio of the (PVP/DNA)₂₀/Mg immersed in SBF for 0 (Fig. 2 dI), 6, 12, 24, 48, 72, 96, 120 and 432 h.

Fig. 3 a) XPS overview spectra and the evolution of (b) P_2p, (c) C_1s, (d) N_1s and (e) O_1s signals of (PVP/DNA)_n/Mg surfaces.

Fig. 4 EIS and the fitted results for the (I) AZ31 substrate, (PVP/DNA)_n/Mg, n = (II) 5, (III) 10, (IV) 20 and (V) 40: (a) Nyquist plots, (b) Bode plots of |Z| vs. frequency, (c) Bode plots of phase angle vs. frequency in SBF and (d) equivalent circuits.

Fig. 5 EIS curves and the fitted results for the (PVP/DNA)₂₀/Mg: (a) Nyquist plots, (b) Bode plots of |Z| vs. frequency, (c) Bode plots of phase angle vs. frequency in SBF and (d) R_ct values vs. immersion time and corresponding equivalent circuits.

Fig. 6 Schematic representation of the degradation mechanism of the (PVP/DNA)₂₀ coating: (a and b) Ca-P nucleation and growth, (c) electrochemical corrosion of the substrate.