Influence of Chemical Composition and Surface Topography of Nanostructured Epoxy Resin DER-331 on Combined Biofilm Formation in Modelling of Biofouling

In the context of greening science and technology, the need to develop safe composite nanomaterials to protect the surfaces of ships and structures is becoming increasingly important and is one of the main economic priorities of the European Green Deal. This article analyzes the results of research on composite material based on epoxy oligomer DER - 331 with biocidal fillers (nanosilver and oxytetracycline), which are recommended for protecting metal surfaces. The proposed two-stage approach in the study of protective composite coatings involves the study of the ecotoxicity of nanomaterials with different contents and combinations of fillers. The study of the ecotoxicity of metal samples with nanostructured epoxy coatings was conducted in vitro model systems using the indicator microorganism Bifidobacterium bifidum. Confirmation of the environmental safety of the nanocomposite determined the feasibility of conducting the second stage of research, which evaluated the effectiveness of composite surfaces for protection against biofouling. Estimating the dynamics of changes in the formation of a two-component biofilm on the composite surfaces of metal test plates using strains of Escherichia coli and Klebsiella pneumonia was the basis of studies in the second stage of research on the protective characteristics of epoxy resin DER-331 with fillers. The formation of a two-component bacterial biofilm on the surfaces of experimental samples was studied in vitro model system. Considering the prolonged terms of biofilm formation under natural conditions, two reference time points for fixing the results (120 and 240 hours) were chosen to study the biofilm formation process. The obtained data show that the components of the composite surface of the test samples for 240 hours inhibit the formation of biofilm in the later stages. There is a significant (p≤0.05) decrease in the total volume of the formed combined biofilm in the test with the results for 120 hours of the experiment. The reduction in the total volume of the formed biofilm by 240 hours of the investigation may be due to the presence of fillers (nanosilver and/or oxytetracycline) and topographic features of the surface. The presence of a porous surface structure of samples based on epoxy resin DER-331 along with the biocidal properties of nanosilver and oxytetracycline fillers (q = 0.050 parts by weight and q = 0.075 parts by weight) changes the dynamics of biofilm formation, inhibiting its maturation. The combination of topographic features of the study samples and the chemical composition of nanostructured surfaces of the epoxy oligomer DER-331 works in favour of synergy in braking the formation of biofilms, which initiate the overall process of biofouling of surfaces.