Nanocomposites and nanomaterials
The release of ZnO nanoparticles from Portland cement nanocomposites and its effects on model microorganisms
Sikora P.1,2, Augustyniak A.2,3,4, Jablonska J.4, Cendrowski K.3
1 Faculty of Civil Engineering and Architecture, West Pomeranian University of Technology, Szczecin, Al. Piastow 50, Szczecin 70-311, Poland
E-mail: pawel.sikora@zut.edu.pl
2 Technische Universität Berlin, Department of Civil Engineering, Gustav-Meyer-Allee 25, 13355 Berlin, Germany
3 Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Szczecin, Al. Piastów 42, Szczecin  71-065, Poland
4 Faculty of Biotechnology and Animal Husbandry, West Pomeranian University of Technology, Szczecin, ul. Klemensa Janickiego 29, Szczecin, 71-270, Poland

The study aimed to assess the release of ZnO nanoparticles from cement mortar blocks that were leached for 72 hours in ultrapure water. For this purpose 3 types of cementitious composites were prepared: reference (R), containing 1% (D1) and 3% (D3) of dispersed ZnO NPs. Samples tested included leachates of 7- and 28-days-old blocks, pulverized and comminuted blocks and blocks treated with 600°C and 800°C. In presented research Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus (bacteria) and Candida albicans (yeast) have been chosen as model microorganisms. In order to assess the effects of ZnO nanoparticles on model microbes the growth kinetics, 4- and 24-hour toxicity, and biofilm formation were tested. Both spectroscopic methods (AAS and ICP-MS) confirmed the release of ZnO NPs from comminuted 1% block and all samples containing 3% of nanomaterial (excluding 28-days-old sample). Obtained toxicity results have shown various microbial responses to tested leachates. Two Gram-negative bacteria, P.aeruginosa and E. coli, demonstrated the different effects of incubation with leachates of temperature-treated, pulverized and comminuted blocks. Presented research shows rather the effect of cement mortar blocks than ZnO NPs on model microorganisms. Obtained results do not indicate the pronounced toxicity of tested nanomaterial to microbes.

Acknowledgments: This research was supported by the National Science Centre (Poland) within project No. 2016/21/N/ST8/00095 (PRELUDIUM 11). P.S. is supported by the Foundation for Polish Science (FNP)