## 5 Coating Materials with Embedded Antibiotics and Other Antibofilm Agents
### Silver Nanoparticles and Silver Ions
#### 5.6.4. Denaturation of Bacterial Proteins and DNA Molecules
The ecotoxicity of prepared SA-AgNPs was assessed on _Ceriodaphnia corntua_, a freshwater crustacean, in comparison with sodium alginate and silver nitrate. The SA-AgNPs were considerably less toxic than AgNO\({}_{3}\). Silver nitrate caused 100% mortality of _C. corntua_ neonates at a concentration of 10 \(\mu\)g/L, while a four-fold increase in concentration was necessary to attain the same mortality when SA-AgNPs were used in place of AgNO\({}_{3}\). The estimated LC\({}_{50}\) values were 7.94 and 3.2 mg L\({}^{-1}\) for SA-AgNPs and AgNO\({}_{3}\), respectively [105]. Although being less toxic than AgNO\({}_{3}\), SA-AgNPs still induced physiological abnormalities (reduced swimming, heart rate, and thoracic limb movement) in _C. corntua_. The antibioticfilm activity of SA-AgNPs was tested against Grampositive (_Listeria monocytogenes_) and Gram negative (_Vibrio parahaemolyticus_) bacteria. The authors reported biofilm inhibition of 98% for _L. monocytogenes_ and of 84% for _V. parahaemolyticus_ at 75 ug/L SA-AgNPs concentration [112]. [PERSON] et al. [114] succeeded in their attempt to achieve silver nanoparticles biosynthesis by using the functional groups of biomolecules present in a _Heliotropium crispum_ (HC) plant extract as both reducing and stabilizing/capping agents. In brief, HC-AgNPs have been prepared by simply mixing the plant extract at a certain concentration with a solution of AgNO\({}_{3}\) in deionized water for 3 h at 37 \({}^{\circ}\)C. The antibiofilm properties of HC-AgNPs were evaluated on clinical isolates of MRSA, _P. aeruginosa_, and _A. baumannii_ using SEM imaging. All tested strains were found to be susceptible to HC-AgNPs. As compared to untreated controls, the SEM micrographs of bacterial strains samples incubated with silver nanocomposites treated media clearly showed biofilm disruption, changes in the morphology of bacteria, and destruction of the extracellular polymeric substances (EPS) that play an important role in cell aggregation, cell adhesion, and biofilm formation [114]. [PERSON] and [PERSON] [115] prepared new hybrid inorganic-organic nanocomposite coatings by incorporating silver ions doped TiO\({}_{2}\) into a polymeric epoxy matrix. This material has the advantage of combining the magnificent biocidal properties of silver ions and the photocatalytic antibacterial activity of nano-TiO\({}_{2}\) (anatase) [116]. The nanocrystalline anatase TiO\({}_{2}\) was prepared by the acid-catalyzed hydrolysis of titanium butoxide. The doping agent (AgNO\({}_{3}\)) was dissolved in aqueous acetic acid, and the resulting solution was added dropwise to an ethanolic solution of titanium butoxide. The so-prepared Ag-TiO\({}_{2}\) nanocomposite contained about 1.5% wt. of Ag\({}^{+}\). Incorporation of Ag-TiO\({}_{2}\) into the epoxy resin polymer matrix was achieved in three steps as follows: (i) Preparation of the resin mixture containing the commercially available resin Lapox(r) L-12 (liquid epoxy resin based on bisphenol-A) and the reactive diluent, Lapox(r) XR-19 (poly(propylene glycol) diglyidyl ether), (ii) decrease the viscosity of the resin mixture by diluting it with ethanol at 1:5 ratio, and (iii) addition of corresponding amounts of the previously prepared Ag-TiO\({}_{2}\) nanocomposite followed by sonication eventually yielding epoxy polymeric nanocomposites with 0.5, 1.0, 1.5, and 2.0 wt% Ag-TiO\({}_{2}\) loading [115]. The antibiofilm activity was indirectly evaluated through the crystal violet staining assay by the measurement of crystal violet absorbance at 600 nm, using a destaining solution. The results were given as inhibition percentages of biofilm development of the tested bacteria (_E. coli_ and _S. aureus_). The antibiofilm activity was directly proportional to Ag-TiO\({}_{2}\) loading. Under UV irradiation for 24 h, the polymer nanocomposite containing 1.5 wt% Ag-TiO\({}_{2}\) completely inhibited (100%) biofilm formation of both _E. coli_ and _S. aureus_[115].