Phycosynthesis of Silver Nanoparticles Using Chlorella vulgaris Metabolites: Its Antibacterial, Anti-Biofilm and In-Vitro Cytotoxicity Potential and Effect of Optimized Conditions on Biosynthesis.

Abstract

The adverse effects of multidrug resistant and biofilm forming microbes on human health is of major concern; therefore a search 
for potential alternative in nanoparticles is required. Green phycosynthesis of silver nanoparticles (SNP) using The Clear 
Supernatant (TCS) of blue-green algae, Chlorella vulgaris (Cv) was investigated. The greenly synthesized Chlorella vulgaris
TCS SNPs (CvTCSSNPs) were characterized using UV-Vis spectrophotometry, SEM, TGA, DLS, EDX and XRD. The 
antibacterial, antibiofilm and in vitro cytotoxicity against brine shrimp was evaluate. Colour change from light green to chocolate 
brown indicate CvTCSSNPs biosynthesis and surface Plasmon resonance peak was observed at 300 nm. CvTCSSNPs was 10 
µm in size, spherical in shape, and can withstand high temperature without totally losing its weight. DLS shows the particle 
diameter average of 82.19 nm and 505.3 nm with a polydispersity index of 0.505. The EDX analysis confirmed a strong signal 
of silver element. The CvTCSSNPs had strong antibacterial activity and profoundly antibiofilm activity against Citrobacter sp., 
S. aureus ATCC 29213, E. coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853. CvTCSSNPs toxicity to Artemia
salina (brine shrimp) LC50 was 1256. 69 µg/mL, it was observed to be insignificant with the highest mortality rate at 2000 µg/mL 
and the lethality was dose dependent. pH 10, 37˚C, 40 mL extract, 5 mM AgNO3 supported optimum CvTCSSNPs production. 
In conclusion, the phycosynthesized CvTCSSNPs had strong antibacterial and antibiofilm activity against the test pathogens. 
CvTCSSNPs may be used as safe and alternative to antibiotics against MDR biofilm producing pathogens.