Melone Pietro, Vitiello Giuseppe, Di Napoli Michela, Zanfardino Anna, Caso Maria Federica, Silvestri Brigida, Varcamonti Mario, D'Errico Gerardino, Luciani Giuseppina
Department of Chemical, Materials and Production Engineering, University of Naples "Federico II", p.le V. Tecchio 80, 80125 Naples, Italy.
CSGI, Center for Colloid and Surface Science, via della Lastruccia 3, 50019, Sesto Fiorentino (FI), Italy.
Biomimetics (Basel). 2019 May 30;4(2):40. doi: 10.3390/biomimetics4020040.
Nature has provided a valuable source of inspiration for developing high performance multifunctional materials. Particularly, catechol-containing amino acid l-3,4-dihydroxyphenylalanine (l-DOPA) has aroused the interest to design hybrid multifunctional materials with superior adhesive ability. DOPA oxidative polymerization mediated by either melanogenic enzymes or an alkaline environment involving catechol intermolecular cross-linking, ultimately leads to melanin oligomers. Recently, relevant studies disclosed the ability of Ti-based nanostructures to tune melanin's supramolecular structure during its formation, starting from melanogenic precursors, thus improving both antioxidant and antimicrobial properties. In this work, we propose a novel biomimetic approach to design hybrid DOPA melanin-like nanostructures through a hydrothermal synthesis opportunely modified by using citric acid to control hydrolysis and condensation reactions of titanium alkoxide precursors. UV-Vis and Electron paramagnetic resonance (EPR) spectroscopic evidences highlighted the key role of citrate-Ti(IV) and DOPA-Ti(IV) complexes in controlling DOPA polymerization, which specifically occurred during the hydrothermal step, mediating and tuning its conversion to melanin-like oligomers. Trasmission electron microscopy (TEM) images proved the efficacy of the proposed synthesis approach in tuning the formation of nanosized globular nanostructures, with high biocide performances. The obtained findings could provide strategic guidelines to set up biomimetic processes, exploiting the catechol-metal complex to obtain hybrid melanin-like nanosystems with optimized multifunctional behavior.
大自然为开发高性能多功能材料提供了宝贵的灵感来源。特别是，含儿茶酚的氨基酸L-3,4-二羟基苯丙氨酸（L-DOPA）引发了人们设计具有卓越粘附能力的杂化多功能材料的兴趣。由黑色素生成酶或涉及儿茶酚分子间交联的碱性环境介导的DOPA氧化聚合最终会生成黑色素低聚物。最近，相关研究揭示了钛基纳米结构在黑色素形成过程中从黑色素生成前体开始调节其超分子结构的能力，从而改善抗氧化和抗菌性能。在这项工作中，我们提出了一种新颖的仿生方法，通过水热合成来设计杂化DOPA黑色素样纳米结构，该合成方法通过使用柠檬酸进行适当修饰，以控制钛醇盐前体的水解和缩合反应。紫外可见光谱和电子顺磁共振（EPR）光谱证据突出了柠檬酸盐-Ti(IV)和DOPA-Ti(IV)配合物在控制DOPA聚合中的关键作用，这种聚合具体发生在水热步骤中，介导并调节其向黑色素样低聚物的转化。透射电子显微镜（TEM）图像证明了所提出的合成方法在调节纳米级球状纳米结构形成方面的有效性，这些结构具有高杀菌性能。所获得的研究结果可为建立仿生过程提供战略指导，利用儿茶酚-金属配合物来获得具有优化多功能行为的杂化黑色素样纳米系统。
