Green chemistry and bio-nanotechnology: design of polyphenols in biocatalysis, functionalized nanomaterials and bio-based product
Author(s)
Piccinino, Davide
Date Issued
May 31, 2019
Type
Doctoral Thesis
Abstract
Each project that was carried out during the doctoral period is in the field of green chemistry and circular economy. The projects were divided into two strands: nanotechnology and bio- nanomimetic systems.
In the projects included in nanotechnologies, polyphenols have been designed and applied in various fields. In a first project the polyphenols were successfully used as an eco-sustainable protection coating with galvanic gold coatings.
Microcapsules and nanocapsules based on the contemporary presence of sulfonate lignin and tannic acid have been prepared by the layer-by-layer procedure, using MnCO3 or organosolv lignin as core templates, and polydiallyldimethylammonium chloride or chitosan as positive charged supporting layers. Nanocapsules and microcapsules of mixed polyphenols showed antioxidant activity, UV- shielding properties, and electrochemical responsiveness, higher than that in homo-polymer nanocapsules counterparts and of the native polyphenols, suggesting the presence of synergistic effects between the two components. The presence of UV-visible bathochromic shift suggested the formation of J-aggregates characterized by an orientation of the adjacent phenolic rings parallel to the longitudinal direction of the layer, with a head-to-tail like arrangement. Moreover, nanocapsules of mixed polyphenols showed an aggregation state higher than that observed in references, the specific morphology of their surface being dependent on the structural arrangement of the different components.
Sustainable catalysts for the oxidation of phenol derivatives under environmentally friendly conditions were prepared by the functionalization of lignin nanoparticles with tyrosinase. Lignin, the most abundant polyphenol in nature, is the main byproduct in the pulp and paper manufacturing industry and biorefinery. Tyrosinase has been immobilized by direct adsorption, encapsulation, and layer-by-layer deposition, with or without glutaraldehyde reticulation. Lignin nanoparticles were found to be stable to the tyrosinase activity. After the enzyme immobilization, they showed a moderate to high catalytic effect in the synthesis of catechol derivatives, with the efficacy of the catalyst being dependent on the specific immobilization procedures.
Laccase from Trametes versicolor has been immobilized on lignin nanoparticles following different approaches: i) encapsulation; ii) direct physical absorption; iii) layer by layer coating; and iv) layer by layer coating followed by chemical cross-linking. Different activity and kinetic properties emerged depending on the immobilization procedure, laccase showing a direct electron transfer mechanism toward lignin when adsorbed or coated on the surface of the nanoparticles. The novel catalysts were active in the oxidation of alcohol derivatives to corresponding aldehydes.
The preparation of novel wrapped carbon nanotubes poly(4-vinylpyridine)/methyl trioxorhenium (MTO) based heterogeneous catalysts has been reported by two different procedures: a) the wrapping by grinding of multiwalled carbon nanotubes (CNTs) with pre-formed adducts (PVP/MTO and PVPN/MTO) and, b) the loading of MTO on previously wrapped CNTs with PVP and PVPN resins. The novel catalysts were characterized by SEM, TEM, ICP-MS and XPS analyses. Both types of catalysts were efficient systems in the oxidation of recalcitrant aromatic sulfur derivatives with H2O2, as representative models of ODS processes. The performance of novel catalysts was found to be dependent on the specific procedure applied for the immobilization of the active species.
DOPA peptidomimetics are an attractive therapeutic tool for the treatment of Parkinson’s disease. Compounds with unusual O-C and N-C covalent bonds between amino acids have been prepared by selective oxidative functionalization of tyrosine residues with tyrosinase from Agaricus bisporus. The reaction proceeded through Michael-like nucleophilic addition of amino acids on the DOPA quinone intermediate initially produced by tyrosinase oxidation. The reaction was effective under heterogeneous conditions by immobilization of tyrosinase on multi walled carbon nanotubes (MWCNTs). The anti-Parkinson activity of novel DOPA peptidomimetics was evaluated by electrophysiological techniques on individual dopaminergic neurons in rat ex vivo midbrain slices. Gly-N-C-Dopa and Val-N-C-Dopa peptidomimetics inhibited neuronal firing and evoked outward currents via activation of the D2 receptors in most dopamine-sensitive neurons. In a subset of neurons which displayed low dopamine sensitivity, Gly-N-C-Dopa also caused significative effects.
Additional information
Dottorato di ricerca in Ecologia e gestione sostenibile delle risorse ambientali
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