Abstract
Background: Numerous cyanobacteria have the potential to reduce metallic ions to form pure metal nanoparticles in a green biosynthesis process. Aim: To investigate the production capacity of silver nanoparticles by the cyanobacterium
Cyanothece
sp. and to examine the effect of five different phytohormones, indole acetic acid, kinetin; gibberellic acid; abscisic acid; and methyl jasmonate, on this capacity. Methods: The cyanobacterial strain was grown for 60 days and the harvested cyanobacterium biomass was incubated with 0.1 mM of AgNO
3
. Percentage conversion of Ag
+
to Ag
0
was calculated to indicate the AgNPs’ production capacity. Different concentrations of the five phytohormones were added to cultures and the AgNP production was monitored throughout different time intervals. Results:
Cyanothece
sp. biosynthesized spherical AgNPs (diameter range 70 to 140 nm, average diameter 84.37 nm). The addition of indole acetic acid and kinetin provoked the maximum conversion (87.29% and 55.16%, respectively) of Ag
+
to Ag
0
, exceeding or slightly below that of the control (56%). Gibberellic and abscisic acids failed to elevate the Ag
+
to Ag
0
conversion rate (45.23% and 47.95%, respectively) above that of the control. Methyl jasmonate increased the Ag
+
to Ag
0
conversion rate to 90.29%, although nearly all the cyanobacterial cultures died at the end. Conclusion: Phytohormones could be used to induce or inhibit the green production of AgNPs with the cyanobacterium
Cyanothece
sp. This novel manipulation technique may have several applications in agriculture or biomedicine.