Bioinspired Catechol-Based Systems: Chemistry and Applications

Catechols are widely found in nature taking part in a variety of biological functions, ranging from the aqueous adhesion of marine organisms to the storage of transition metal ions [...

Studi modello sul meccanismo dell’attività antinitrosante di polifenoli di origine naturale

Composti polifenolici di origine naturale comunemente assunti con la dieta sono stati oggetto di notevole interesse negli ultimi anni per la loro azione preventiva nei confronti di patologie cardiovascolari e degenerative, in particolare i tumori dell’apparato gastrointestinale.1 Tali effetti sono stati attribuiti principalmente alla capacità di questi composti di fungere da antiossidanti e/o antinitrosanti, inibendo ad esempio i processi mutagenici indotti da ioni nitrito nell’ambiente acido dello stomaco.2 In questa comunicazione verranno riportati i risultati di studi volti a chiarire le basi chimiche del meccanismo di azione di alcuni tra i principali agenti antinitrosanti di origine naturale, quali acido caffeico e acido clorogenico, idrossitirosolo , epigallocatechingallato , resveratrolo e piceatannolo. Verrà inoltre discusso l’effetto della coniugazione con il glutatione, un tripeptide tiolico endogeno con funzioni antiossidanti e detossificanti, sulle proprietà antinitrosanti di tali polifenoli

Ceramic templated melanin nanostructures: a biomimetic synthesis approach to bio-functional hybrid materials

Organo-inorganic hybrids provide the opportunity to invent a huge set of new multifunctional materials with a large spectrum of known and as yet unknown properties. Melanins, hydrophobic natural pigments have been emerging as a powerful organic component for developing biologically active materials because of their numerous biological functions, such as photo-protection, photosensitization, free radical quenching, metal ion chelation and even intrinsic antimicrobial behavior. Furthermore, due to their semiconductor behavior and electrical properties they hold great promise for next-generation photovoltaics and bioelectronics. Melanins are produced in-vivo by oxidative polymerization of phenolic or indolic compounds within melanosomes that template melanin formation. Following a bioinspired approach, herein we propose a novel synthesis approach towards hybrid materials, that exploits inorganic ceramic systems as catalysts and structure directing agents in melanin biopolymers building up. In this route we disclosed TiO2 ability to drive 5,6-dihydroxyindole-2-carboxylic acid (DHICA) polymerization via complex mediated electron transfer (LMCTC) from DHICA to the TiO2 lattice, that enables photo-activation under visible light [1]. This strategy led to eco-friendly, non-cytotoxic, melanin-TiO2 hybrid nanostructures with unique antimicrobial activity even higher than bare melanin under visible light and peculiar antimicrobial mechanism (Fig.1A-B) [2,3]. This synthesis approach was successfully extended to the design of melanin-silica hybrid nanoparticles, integrating the potent antioxidant properties of DHICA melanin into a stable, bioactive and biocompatible silica scaffold with high antioxidant\u2028and cytoprotective effects associated with a specific subcellular\u2028localization (Fig.1C-D) [4]. Both systems prove that melanin’s biofunctional and physical-chemical properties can be markedly enhanced through its templated polymerization in the presence of a ceramic phase, disclosing the manifold potentialities of this approach, that can ultimately lead to cutting-edge functional hybrid materials featuring relevant biological properties, such as antimicrobial activity, selective cell interaction and signaling, as well as ionic- and electronic-based charge transport

Understanding the Polymerization Process of Eumelanin by Computer Simulations

We present and discuss a computational setup aimed at modeling the polymerization process of eumelanin by combining together molecular dynamics simulations and ab initio total-energy calculations. By simulating the oxidative polymerization process of eumelanin in methanol, we provide evidence that “in silico” synthesized samples are mostly composed of low-molecular-weight structures: an exponential distribution of the molecular weights is found, yielding an average weight less than 10. Adopting the scheme of chemical disorder, we also perform a statistical analysis on the variety of molecules formed, focusing on both their structural and electronic features. In particular, we identify the most frequent structural patterns within the molecules by analyzing the occurrence of the single chemical bonds. Moreover, we show how most of the molecules have a large number of nonterminated oxygen atoms, highlighting the pivotal role of =O groups in the eumelanin molecular stability.We acknowledge the Regione Sardegna basic research Project no. CRP78744 “Energy Applications with Porous Silicon (ENAPSi).” E.C. acknowledges support from MINECO (Spain) (Grant FIS2015-64886-C5-4-P), the Severo Ochoa Centers of Excellence Program (Grant SEV-2015-0496), and Generalitat de Catalunya (2017SGR1506).Peer reviewe