In plant-based green synthesis, we use phytochemicals from plant extracts as reducing and/or capping agents. It helps to minimize or avoid the use of hazardous precursor reagents. Do phytochemicals help in reducing the toxicity of the prepared NMs too?
If yes, how do they change their toxicity profile?
Arpita Dey
In general, plant extracts are not controlled, are of doubtful composition, and contain different quantities of reducing and stabilizing agents (often depending on the time of harvest and extraction). This leads to difficulties in trying to prepare known (metal) colloids of controlled size (and shape).
The answer to your last question (Do phytochemicals help in reducing the toxicity of the prepared NMs too?) is 'No'. The implication here is that 'nature is good' and 'chemicals are bad' even though all the compounds in plants are chemicals. Further, the toxic chemicals employed in the synthesis of metal nanoparticles are provided by the inorganic metal precursors needed to produce those metal nanoparticles - for example, AgNO3 (and NH3 used in the standard preparations), H2PtCl6.xH2O, HAuCl4.yH2O etc... The latter fact is usually disregarded or conveniently ignored when 'green synthesis' is discussed.
Hi!
Article Plant-mediated green synthesis of metal-based nanoparticles ...
Arpita Dey
In general, plant extracts are not controlled, are of doubtful composition, and contain different quantities of reducing and stabilizing agents (often depending on the time of harvest and extraction). This leads to difficulties in trying to prepare known (metal) colloids of controlled size (and shape).
The answer to your last question (Do phytochemicals help in reducing the toxicity of the prepared NMs too?) is 'No'. The implication here is that 'nature is good' and 'chemicals are bad' even though all the compounds in plants are chemicals. Further, the toxic chemicals employed in the synthesis of metal nanoparticles are provided by the inorganic metal precursors needed to produce those metal nanoparticles - for example, AgNO3 (and NH3 used in the standard preparations), H2PtCl6.xH2O, HAuCl4.yH2O etc... The latter fact is usually disregarded or conveniently ignored when 'green synthesis' is discussed.
Please check the folowing document:
DOI: 10.1007/s11101-017-9490-8
Regards !
Alan F Rawle
Yes, Sir, it is very complex to regulate the size and shape of the NMs through the plant-based synthesis method. Even though we could control somewhat the broader range of size distribution, but we were not able to synthesize NMs of uniform size.
Replacing chemical reagents with phytochemicals as reducing agents helps in minimizing the use of harmful precursors, but there are the metal salt precursors, most of them have a more or less toxic nature, as you highlighted.
In regard to their biocompatibility, when these secondary metabolites from the plants are also acting as capping/stabilizing agents, can they, to some extent, make these NMs biologically safe compared to the inorganic NMs prepared by chemical/physical method?
Best Regards
Miguel Pereira-Silva Fatma Zohra Benabid
Thank you for the articles. I am going through those.
Best Regards
Arpita Dey Many inorganic reducing agents are innocuous - for example the citrates used in the Turkevich route for Au colloid synthesis. Belladonna is natural but highly toxic. Snake venom is natural too. Generalizations always have difficulties...
Alan F Rawle
Thank you so much for this insight.
As we are experimenting with medical applications, we are focusing on means to reduce the toxicity of NMs as much as possible and to make them more biocompatible.
Arpita Dey
You say 'we are experimenting with medical applications'...
Even more reason to control the ingredients that go into any recipe...
It has been stated that all medicines are controlled toxins or poisons - you take the drug in order to kill something else (be it a headache or a bacterium).
Alan F Rawle Thank you.
The discussion will help me in better evaluation of the properties of the prepared nanomaterials.
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