Effect of size, shape and surface structure of silver nanoparticles on their interaction with model proteins

Zbog svojstava na nano razini, primjena nanosrebra (AgNP) u potrošačkim i medicinskim proizvodima je u stalnom porastu što nužno zahtijeva stalnu procjenu njihovih učinaka na ljudsko zdravlje. Cilj ovog doktorskog rada bio je utvrditi kako različita fizikalno-kemijska svojstva AgNP određuju njihovo ponašanje, stabilnost i interakcije u različitim biološkim medijima. U tu svrhu je sintetizirano šesnaest vrsta AgNP različitih oblika i površinske stabilizacije u veličinama od 10 nm i 50 nm. Sve AgNP vrste su pažljivo karakterizirane obzirom na raspodjelu veličina, površinski naboj, topljivost i ponašanje u vodi, u ultra čistoj vodi, pri različitim pH i ionskim jakostima, uz dodatak površinski aktivnih tvari, u fiziološkoj otopini, fosfatnom puferu i fosfatnom puferu uz dodataka 0.9% NaCl. AgNP vrstama određen je antibakterijski učinak na sojevima E. coli i S. aureus. Nano-bio interakcije istraživane su koristeći dva modelna proteina: albumin i α-1-kiseli glikoprotein. U tu je svrhu određeno kako različita fizikalnokemijska svojstva AgNP utječu na konstante vezanja ta dva proteina na površinu nanočestica, te što se događa sa sekundarnom strukturom proteina uslijed vezanja na AgNP. Utvrđeno je da osim naboja površinskog stabilizatora, značajnu ulogu u nano-bio interakcijama ima nominalni promjer AgNP. S porastom ionske jakosti ili značajnom promjenom pH medija mijenja se površinski naboj, a AgNP se destabiliziraju. Ukoliko u mediju nema biomolekula kao što su proteini, AgNP su nestabilne i podložne aglomeraciji i otapanju. Proteini se vežu na AgNP površinu čim se AgNP izlože mediju koji sadrže proteine, a konstante vezanja proteina na površinu AgNP slične su vezanju tih proteina s nekim lijekovima. Promjena sastava medija ne uzrokuje značajne promjene u tim nano-bio interakcijama. Vezanje albumina s AgNP rezultira većom i raznolikijom promjene sekundarne/tercijarne strukture proteina u odnosu na onu koja se događa s α-1-kiselim glikoproteinom.Due to properties of silver at a nano level, silver nanoparticles (AgNP) are currently being used in an increasing number of consumer and medical products, which necessitate their safety assessment for human health. The aim of this doctoral work is to determine how different physico-chemical properties of AgNP affect their behaviour and interaction in different biological media. For this purpose, sixteen types of AgNP of different shape, size (10 and 50 nm) and surface stabilization were prepared. Careful characterization of their size distribution, surface charge, dissolution, and behaviour in water, at different pH and ionic strength, in the presence of surface active agents, in phosphate buffer, in 0.9 % NaCl solution, and in phosphate buffer with addition of 0.9 % NaCl was carried out. Antimicrobial efficacy of AgNP were tested using two bacterial strains, E. coli i S. aureus. Nano-bio interactions were investigated using two model proteins: albumin and α-1-acid glycoprotein. For this purpose, effect of various physical-chemical properties of AgNP on the binding constants of these two proteins on the AgNPs surface was evaluated, as well as the changes in the secondary protein structure due to binding to AgNP. Obtained results demonstrated that the surface charge and nominal diameter of AgNP both have a significant role in nano-bio interactions. The surface charge and AgNP changes upon increase in ionic strength or significant changes in pH of the inclusion media, which lead to AgNP destabilization. In media without biomolecules like proteins, AgNP are unstable and susceptible to agglomeration and dissolution. Proteins present in the media bind to the AgNP surface as soon as AgNP are suspended in these media. Binding constants of proteins to AgNP surface are similar to binding between these proteins and some drugs. Changing the media composition does not cause significant changes in these nano-bio interactions. Binding of albumin to AgNP results in a greater and more varied alteration of the secondary / tertiary protein structure compared to α-1-acid glycoprotein