5,6-Dihydroxyindole-2-carboxylic Acid–TiO2 Charge Transfer Complexes in the Radical Polymerization of Melanogenic Precursor(s)

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• 作者：Giuseppe Vitiello ; Alessandro Pezzella ; Vincenzo Calcagno ; Brigida Silvestri ; Luca Raiola ; Gerardino D’Errico ; Aniello Costantini ; Francesco Branda ; Giuseppina Luciani
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：March 24, 2016
• 年：2016
• 卷：120
• 期：11
• 页码：6262-6268
• 全文大小：370K
• ISSN：1932-7455

文摘

A combination of biomedical and technological applications is generating, over the past decades, the well-established interest toward melanins and melanogenesis. Several compounds have been explored to promote/catalyze oxidative polymerization of melanogenic precursors, such as 5,6-dihydroxyindole-2-carboxylic acid (DHICA), to melanin-like biopolymers in vitro. TiO<sub>2sub> has shown a photocatalytic activity driving DHICA polymerization and leading to the formation of melanin–TiO<sub>2sub> hybrid nanostructures with unique biocide behavior even under visible light. However, the mechanism of melanin formation in those hybrids is not yet well understood although a ligand to metal charge transfer (LMCT) process involving DHICA and Ti<sup>4+sup> ions was hypothesized. Here, we focus on melanin formation and apply a complementary analysis, by using photoluminescence (PL), UV–vis, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopy to reveal the mechanism of DHICA polymerization in the presence of a TiO<sub>2sub>-sol. This study discloses TiO<sub>2sub> potentialities to drive and template DHICA polymerization to melanin via LMCT-based photo-oxidative process.