Table 1.

Pros and cons of physicochemical and biological methods for AuNP synthesis

Method	Pros	Cons
Top-down synthesis	Highly controlled particle size distribution and shape.	Extreme conditions, high tech facilities, high cost.
Bottom-up synthesis	Cost-effective. Highly controlled particle size distribution and shape.	Potentially hazardous capping ligands and residual toxins add to environmental toxicity.
Bacteria	Cost-effective and environmentally safe. Biological capping agents for AuNPs stabilization.	Large nanoparticles with broad particle size distribution. It is not possible to obtain pure nanoparticles without any organic components.
Fungi	Cost-effective and environmentally safe. High concentration of extracellular redox enzymes and capping agents for AuNPs stabilization. Smaller size than bacterial-synthesized nanoparticles. Easy scale up.	Broad particle size distribution, low repeatability. It is not possible to obtain pure nanoparticles without any organic components.