The purpose of the thesis work is to study the oxidation reaction of silver nanoparticles in the presence of cysteamine, in order to evaluate the possibility of using this reagent in the future as a disposal agent for AgNPs left in a scar tissue as a result of wound healing process. The progress of the reaction under various conditions was observed by means of spectrophotometric kinetics: absence of oxygen; various stoichiometries Ag: Cys; various pH values including physiological pH. The dissolution effect was also evaluated on AgNPs of different nature: AgNPs immobilized on a glass surface; pectin-AGNPS; PEG-AGNPS. From spectrophotometric titrations of silver nitrate and cysteamine hydrochloride information has been deduced regarding the product of the oxidation reaction, that is, stability and stoichiometry and the competition between the complex species and the precipitation of the AgCl salt. From experiments in cyclic voltammetry we observed the variation of the redox potential of silver in solution when it is complexed by cysteamine, the dependence of the latter on concentration of binder and pH. It was also possible to hypothesize the AgNPs aggregation model using data collected from stopped flow and DLS measurements (hydrodynamic radius and Z potential) based on the presence of intermolecular hydrogen bonds between cysteamine molecules on different AgNPs.
Lo scopo del lavoro di tesi è di studiare la reazione di ossidazione di nanoparticelle dargento in presenza di cisteamina, al fine di valutare la possibilità di utilizzo di questo reagente in futuro come agente di smaltimento di AgNPs rimaste in un tessuto cicatriziale come conseguenza del processo di wound Healing. Si è osservato, mediante cinetiche spettrofotometriche, landamento della reazione in varie condizioni: assenza di ossigeno; varie stechiometrie Ag:Cys; vari valori di pH tra i quali pH fisiologico. Si è valutato leffetto di dissoluzione anche su AgNPs di diversa natura: AgNPs immobilizzate su una superficie vetrosa; pectina-AgNPs; PEG-AgNPs. Da titolazioni spettrofotometriche di argento nitrato e cisteamina idrocloruro sono state dedotte informazioni riguardanti il prodotto della reazione di ossidazione, ovvero, stabilità e stechiometria e la competizione tra la specie complesso e la precipitazione del sale di AgCl. Da esperimenti in voltammetria ciclica si è osservata la variazione del potenziale redox dellargento in soluzione quando viene complessato dalla cisteamina, la dipendenza di questultimo da concentrazione di legante e pH. È stato possibile ipotizzare inoltre il modello di aggregazione delle AgNPs mediante dati raccolti da misure stopped flow e DLS (raggio idrodinamico e potenziale Z) che si basa sulla presenza di legami idrogeno intermolecolari tra molecole di cisteamina su AgNPs diverse.
Studio di metodi per ottenere la rapida dissoluzione di nanoparticelle d'argento a pH fisiologico
PRETI, LUCA
2018/2019
Abstract
The purpose of the thesis work is to study the oxidation reaction of silver nanoparticles in the presence of cysteamine, in order to evaluate the possibility of using this reagent in the future as a disposal agent for AgNPs left in a scar tissue as a result of wound healing process. The progress of the reaction under various conditions was observed by means of spectrophotometric kinetics: absence of oxygen; various stoichiometries Ag: Cys; various pH values including physiological pH. The dissolution effect was also evaluated on AgNPs of different nature: AgNPs immobilized on a glass surface; pectin-AGNPS; PEG-AGNPS. From spectrophotometric titrations of silver nitrate and cysteamine hydrochloride information has been deduced regarding the product of the oxidation reaction, that is, stability and stoichiometry and the competition between the complex species and the precipitation of the AgCl salt. From experiments in cyclic voltammetry we observed the variation of the redox potential of silver in solution when it is complexed by cysteamine, the dependence of the latter on concentration of binder and pH. It was also possible to hypothesize the AgNPs aggregation model using data collected from stopped flow and DLS measurements (hydrodynamic radius and Z potential) based on the presence of intermolecular hydrogen bonds between cysteamine molecules on different AgNPs.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
Per maggiori informazioni e per verifiche sull'eventuale disponibilità del file scrivere a: unitesi@unipv.it.
https://hdl.handle.net/20.500.14239/19108