Modelling of the enzymatic synthesis of silver nanoparticles

Nanotehnologija je jedna od najpopularnijih tema istraživanja u modernoj znanosti materijala te se naziva i područjem sljedeće industrijske revolucije. Nanočestice srebra (Ag NPs) najčešće su korištena vrsta metalnih nanočestica te se, s obzirom na baktericidna svojstva, primjenjuju uglavnom u području medicine za liječenje teških opeklina, razne dijagnostičke postupke i kao nosioci lijekova, ali i u tekstilnoj i prehrambenoj industriji gdje se ugrađuju u materijale u svrhu poboljšanja svojstava. Kao alternativa tradicionalnoj kemijskoj sintezi Ag NPs, danas se često koristi njihova enzimska sinteza kojom se smanjuje upotreba reaktanata štetnih za ljude i okoliš. U ovom radu, u svrhu sinteze Ag NPs, korišten je enzim celobioza dehidrogenaza (Mt CDH) koji katalizira reakciju oksidacije celobioze te djeluje kao reducens iona srebra (Ag+ u Ag0). Ispitana je kinetika enzima kao i utjecaj iona srebra na reakcijsku brzinu u acetatnom i citratnom puferu. Kinetika je u oba slučaja opisana jednosupstratnom Michaelis - Menteničinom kinetikom uz kompetitivnu inhibiciju ionima srebra. Na temelju procijenjenih kinetičkih parametara zaključeno je kako je reakcija povoljnija u acetatnom puferu, s obzirom na znatno manju inhibiciju reakcije i deaktivaciju enzima ionima srebra u tom mediju. Postavljeni matematički model validiran je provođenjem reakcija sinteze Ag NPs u kotlastom reaktoru.Nanotechnology is one of the most popular research topics in modern materials science and is also called the area of the next industrial revolution. Silver nanoparticles (Ag NPs) are the most commonly used type of metal nanoparticles mainly in medicine for the treatment of severe burns due to their bactericidal properties, various diagnostic procedures and as drug carriers, but also in the textile and food industry where they are incorporated into materials to improve their properties. As an alternative to the traditional chemical synthesis of Ag NPs, the enzymatic synthesis is often used to reduce the use of reactants harmful to humans and the environment. In this work, the enzyme cellobiose dehydrogenase (Mt CDH) that catalyzes the oxidation reaction of cellobiose and acts as a reducing agent of silver ions (Ag+ in Ag0) was used. The kinetics of the enzyme as well as the influence of silver ions on reaction rate in acetate and citrate buffer were investigated and, in both cases, described by single-substrate Michaelis - Menten kinetics with competitive inhibition by silver ions. Based on the estimated kinetic parameters, it was concluded that the reaction is more favorable in acetate buffer, given the significantly lower inhibition of the reaction and inactivation of the enzyme by silver ions in that medium. The set mathematical model was validated by conducting Ag NPs synthesis reactions in a batch reactor