Design and physico-chemical characterization of metal-containing nanoparticles for antimicrobial coatings

Abstract

Uudsete omadustega nanomaterjale (läbimõõt vähemalt ühes suunas alla 100 nm) rakendatakse arvukates tarbekaupades ning tootearenduses. Paljude selliste tarbekaupade eesmärk on piirata mikroobide levikut. Tarbekaupades enimkasutatud nanomaterjal on hõbe (edaspidi Ag) ning peamiselt tuleneb Ag nanoosakeste antimikroobne toime osakestest eralduvatest Ag+ ioonidest. Antimikroobsete toodete eesmärk on valdavalt bakterite tapmine või nende kasvu pärssimine kahjustamata nn mitte-sihtorganisme (sh inimesi) ning seepärast sisaldab käesolev teadustöö uurimusi erineva suuruse, kuju ja pinnalaenguga Ag nanoosakeste antimikroobsusest, mürgisusest ja mürgisuse mehhanismidest tõvestavatele mikroobidele ja imetajarakkudele. Tulemustest selgub, et positiivse pinnalaenguga Ag nanoosakeste kasutamist tuleks vältida toodetes, millega inimene vahetult kokku puutub, sest sellised osakesed olid imetajarakkudele märkimisväärselt mürgisemad. Ag nanoosakesi otsustati rakendada antimikroobsetes katetes, kuna viimaste väljatöötamine on tänu multiresistentsete mikroobitüvede järjest suurenevale osakaalule kasvava potentsiaaliga. Käesoleva töö varasemad tulemused näitasid, et fotokatalüütilised pinnad on võimelised orgaanilisi jäänuseid sh mikroobirakke lagundama, seepärast kombineeriti Ag osakesed fotokatalüütiliste nanoosakestega. Fotokatalüütiliseks pinnakatte komponendiks valiti osaliselt lahustuvad ZnO nanoosakesed. Ag nanoosakeste kombineerimine ZnO osakestega suurendas fotokatalüüsi aktiivsust ning antimikroobsuse efektiivsust ning seepärast on Ag sobilik materjal efektiivsete fotokatalüüsil põhinevate antimikroobsete katete arendamisel. Väljatöötatud pinnakatete korduvkasutatavuse hindamine näitas, et pinnakatete antibakteriaalne aktiivsus ja fotokatalüütilise lagundamise võime ei vähenenud märkimisväärselt ka pärast kümmet kasutustsüklit. Meile teadaolevalt oli meie uurimus esimene, mis näitas ZnO/Ag pindade korduvkasutatavust antimikroobses rakenduses.

Novel properties of engineered nanomaterials (NMs) (less than 100 nm in at least one dimension) are exploited in numerous consumer products and in product development. Many consumer products aim to prevent the spread of microbes. Silver (Ag) is known for its Ag+ ion-based antimicrobial properties and therefore Ag nanoparticles (NPs) are one of the most used NMs in consumer products. Antimicrobial products are meant to kill or inhibit the growth of predominantly bacteria without causing harm to so-called non-target organisms (including humans) and therefore, the current research includes studies about the antimicrobial efficacy and toxicity to mammalian cells, including the mechanisms behind it, of a library of Ag NPs with different sizes, shapes and surface charges. The results suggest avoiding the use of positively charged Ag NPs in human directed products as those particles presented notably higher toxic effect to mammalian cells. Based on those results, the study made suggestions for using Ag NPs in antimicrobial coatings: the development of which is difficult to underestimate due to the increasing spread of multidrug resistant microbes. Along with Ag NPs, this study suggested including a photocatalytic component to the surface coatings as according to our previous results, photocatalytic coatings have the potential to degrade organic material on their surface. Partially soluble ZnO NPs were chosen as the photocatalytic component. ZnO NPs were supplemented with Ag NPs (ZnO/Ag composite NPs) to prepare efficient antimicrobial coatings with a combined effect from photocatalysis and antimicrobial metal ions (Ag+, Zn2+). The addition of Ag NPs increased photocatalytic effect and antimicrobial efficiency and therefore Ag can be considered a suitable material in the development of efficient photocatalytic material-based antimicrobial coatings. Reusability of the prepared coatings was tested and no significant decrease in neither antibacterial activity nor photodegradation capability was observed after 10 usage cycles. According to our best knowledge, our study was the first to demonstrate the reusability of ZnO/Ag surfaces for antimicrobial applications.