Table 2.

Advantages and limitations of using biological agents for NPs synthesis.

Biological Material	Advantages	Ref.	Limitations	Ref.
Plants	natural source of antioxidant compounds	[95]	the amount of material depends on seasonality of plants the quality of NPs depends on the growth, harvesting conditions and geographical distribution of plants	[130]
	easy to grow and safe to handle	[100]
	biocompatibility	[96]
	wide range of applications in different industries and medicine	[98]	specific process conditions such as temperature, pressure, reaction time, chemical reagents additions variation in NPs quality due to irregular shape and size	[59]
	small particle size and zeta potential indicate good stability enhanced biodistribution, efficacy and safety for NPs compared to raw extracts	[130]
	biodegradable post-materials non-toxic products, safer solvents and reaction conditions	[97]
	waste prevention	[100]	possible neurotoxicity, tissue toxicity only a few are approved by EMA and FDA, thus needing further analyses.	[131]
	good antifungal activity and promising antibacterial activity on both Gram-positive and Gram-negative strains	[99]
	promising results in cancer therapy.	[100]
Microorganisms	very good yield due to faster processes environmental safety	[132]	tedious purification steps poor/lack of understanding of the competitive antimicrobial mechanisms challenges in translating the production of NPs to industrial scale potentially diminished yield caused by the growth rate of bacteria, enzymatic activity, biochemical pathways and purification processes.	[133]
	cost effectiveness the preferred material consists of bacteria/fungi due to their capacity for producing higher concentrations of reductase enzyme	[134]
	ease of cultivation and adjustment of size, shape and morphology of NPs effective penetration through matrix biofilm produced by pathogenic agents, NPs play the role of a “Trojan horse” for bacterial cells.	[134]
Algae	renewable and sustainable natural resources natural products and biodegradable post-materials	[135]	limited applicability, low biocompatibility and, in some cases, elevated toxicity no clear reaction mechanism during NPs formation	[136]
	biocompatibility cost-effectiveness versatility	[137]
	scalability reduced negative environmental impact.	[138]	irregular shapes and sizes depending on solvents, vehicle, pH, exposure time and age of algal extract.	[59]