Antifouling and anti-algal effects of chitosan nanocomposite (TiO2/Ag) and pristine (TiO2 and Ag) films on marine microalgae Dunaliella salina

Biofouling is the main problem for marine water systems such as the immersed leisure vessels, oceanographic sensors, heat exchangers, and ship hulls. The obstacle of biofouling created by barnacles, mussels, bacteria, and micro and/or macro algal species. To overcome this problem, some metal nanoparticles incorporated films and membranes were employed to control the biofouling. In this study, metal nanoparticles (Ag NPs and TiO2) of different concentrations (0.25, 0.5, 0.75 wt %) were incorporated with chitosan polymer to fabricate nanocomposite and pristine films. The biofouling inhibition was examined using the marine microalgal species Dunaliella salina. The higher performance in algal viability (45.42 +/- 0.36%) was observed by TiO2 and concentration maintained Ag NPs incorporated chitosan nanocomposite (0.5 wt% Ag/ 0.75 wt% TiO2) films under UV-C condition, in comparison with other nanocomposite and pristine concentrations. The same concentration showed higher activity in the slime formation (Glycocalyx test), mass assessment, exo-polymeric substances (EPS), and membrane damages (LPO) under UV-C condition. The release of silver ions (Ag+) and uptake of Ag showed good performance of Ag NPs incorporated nanocomposite film at higher concentration (0.5 wt% TiO2/0.75 wt% Ag). The surface morphology of nanocomposite were characterized using SEM, and AFM, and the surface modifications of chitosan nanocomposites were examined by XRD, and FTIR. TiO2 and Ag NPs being photoactive induce more ROS that damage the cell membrane leading to algal cell death and control of biofouling formation.