Silver content analysis and change of nanoparticles stability in tobacco seedlings (Nicotiana tabacum L.)

Nanočestice srebra (AgNP) se koriste zbog protubakterijskog djelovanja u mnogim komercijalno dostupnim proizvodima, uključujući pesticide, ali predstavljaju potencijalnu opasnost za okoliš zbog svoje toksičnosti, reaktivnosti i akumuliranja u biljkama. Zbog svoje velike površine u odnosu na volumen, AgNP su vrlo reaktivne i podložne otpuštanju iona srebra, što potencijalno povećava njihovu toksičnost. Također, pokazano je da AgNP nisu stabilne u eksperimentalnom mediju i da su sklone interakciji s komponentama u otopini, što može utjecati na njihovu toksičnost i upotrebljivost. U svom diplomskom radu analizirala sam sadržaj srebra (Ag) u tkivu klijanaca duhana (Nicotiana tabacum L.), u zaostalom talogu MS medija i otopini u kojoj su klijale sjemenke te promjenu stabilnosti AgNP u MS mediju. Sjemenke duhana isklijavala sam deset dana u tekućem MS mediju s dodatkom AgNP stabiliziranih različitim omotačima (citrat, bPEI, PEG) ili srebrovog nitrata (AgNO3) pri koncentracijama od 25, 50, 75, 100, 125 i 150 μM, a u slučaju kontrole bez dodatka Ag. Desetog dana tretmana sa svim tipovima AgNP najviša koncentracija Ag izmjerena je u tkivu klijanaca, zatim u zaostalom talogu te najniža u otopini. Nakon tretmana s AgNO3 koncentracija Ag u tkivu bila je niža u odnosu na tretmane s AgNP, dok su koncentracije Ag u otopini bile ujednačene. Koncentracija Ag u talogu bila je najniža nakon tretmana s AgNP-bPEI. Snimke dobivene transmisijskom elektronskom mikroskopijom pokazuju da su AgNP bile sferične i jednakih veličina te pojedinačne ili u nakupinama u matičnim otopinama kao i u eksperimentalnim otopinama neposredno nakon miješanja AgNP i MS medija (prije dodatka sjemenki). Desetog dana tretmana u talogu MS medija, čestice Ag uglavnom su bile sfernog oblika, ali različitih veličina, pojavljivale su se pojedinačno ili u nakupinama te agregirale.Silver nanoparticles (AgNP) are used for their antimicrobial properties in many available commercial products, including pesticides, but they can pose a risk to the environment due to their toxicity, reactivity and accumulation in plants. Because of their large surface area to volume ratio, AgNPs are highly reactive and subjected to silver ions release which potentially increases their toxicity. Moreover, it has been shown that AgNPs are not stable in the experimental medium and they react with components in the solution which may affect the toxicity and usability. In this graduation thesis, I analysed the silver (Ag) content in tobacco (Nicotiana tabacum L.) seedlings tissue, in the residual precipitate of MS medium and in the solution in which seeds germinated. The change in the stability of AgNPs in the MS medium was also examined. Tobacco seeds were germinated for ten days in liquid MS medium containing either AgNPs stabilized with different coatings (citrat, bPEI, PEG) or silver nitrate (AgNO3) at concentrations of 25, 50, 75, 100, 125 and 150 μM. In the case of control, no Ag was added. On the 10th day of the treatment with all types of AgNPs, the highest concentration of Ag was measured in the seedlings tissue, then in the residual precipitate, while the lowest values was obtained in the solution. After the treatment with AgNO3, the concentration of Ag in the tissue was lower than in the AgNP treatments, while the Ag concentrations in the solution were equal for all treatments. Concentration of Ag in the residual precipitate was the lowest after the treatment with AgNP-bPEI. Transmission electron microscopy images showed that the AgNPs were spherical, of the same size and individually dispersed or in the clusters in the stock solutions as well as in experimental solutions immediately after mixing AgNPs and MS medium (before seeds were added). On the 10th day of the treatment, in the residual precipitate of MS medium AgNPs were mostly spherical but of different sizes, individually dispersed or clustered and they aggregated