Fig. 5. The viability of C. reinhardtii upon incubation at pH 5.5 with aqueous solutions of different concentrations of (A) free BRB and (B) BRB-loaded shellac NPs (non-coated with ODTAB) at room temperature up to 6 hours incubation time at pH 5.5. (C)–(H) SEM images of C. reinhardtii whereby (C) and (D) represent the control sample of the microalgae cells. (E) and (F) C. reinhardtii incubated with 0.01 wt% free BRB after 4 hours incubation, (G) and (H) C. reinhardtii incubated with 0.01 wt% BRB-loaded in shellac NPs up to 4 hours. Note that the free BRB is more effective anti-algal agent than the non-coated shellac NPs with the same concentration of shellac NP-loaded BRB.