There is an interaction between the negative groups of sodium tripolyphosphate (TPP) and the positively charged amino groups of chitosan (if we prepared by ionotropic gelation method). Due to its cationic charge, biocompatibility and low toxicity, chitosan is used as a vehicle system for delivery of drugs.

Since the plant extract contains various secondary metabolites, it acts as reducing and stabilizing agents for the bioreduction reaction to synthesized novel metallic nanoparticles. Natural bioactives present in plant extracts are responsible for the creation of coating on nanoparticles and thus, rendering the nanoparticles stable against agglomeration. There is a significant variation in chemical compositions of plant extract of same species when it collected from different parts of the world and may lead to different results in different laboratories. This is the major drawback of synthesis of nanoparticles using plant extracts as reducing and stabilizing agents and there is need to resolve this problem. On identifying biomolecules present in the plant which are responsible for mediating the nanoparticles production can give a new facelift towards green syntheses of nanoparticles.

http://www.sciencedirect.com/science/article/pii/S2090123215000314