Synthesis of Silver Nanoparticles in Bean (Phaseolus vulgaris L.)

The present work shows a brief review of some natural sources used to produce metallic
nanoparticles and leaves the issue open for further discussion and new investigations. The use of
nanoparticles has gained an increased attention due to its potential application as a drug delivery
medium. The nanoparticle drug delivery characteristics can be engineered to obtain a certain rate or
localization, increase the drug load per particle, among others. Some plants have biomolcules for
specific functions as reduction and stabilization of the particles formed inside. These biomolecules are
for example polyphenolic compounds, hydroxyflavons, oxalic acid, terpenoids and many more. Even
the exact nature of the bioreduction of metal ions is not completely understood, the production and
investigation of metallic nanoparticles formed in plants have been increased on last 10 years. A wide
variety of sizes, 5-150 nm, and shapes, spherical, triangular, rods, hexagonal, have been obtained in
plants and fruit extracts. The plant Phaseolus vulgaris (beans) was used to form silver nanoparticles
through bioreduction of Ag (I) to Ag (0) in the living plant. Two groups of plants were used. One group
of plants grew at garden soil and the other in cotton. To determine the nanoparticles formed in plants,
they have been analyzed by using X-ray absorption spectroscopy (XAS). In both cases, a solution of
AgNO3 was added initially in a concentration of 0.01M then the concentration was changed to 0.1
mM.). In stem and leaves silver were found as Ag (0). The XAS spectra were adjusted for more
accurate results. Plants may reduce the valence of silver and form nanoparticles. The TEM images
show that the average particle size is 18 nm, showing in various forms and a greater number of them
in the leaves of plants grown in soil. Results also indicate that nanoparticles obtained from the stem
and leaves have different forms and they can affect the soil pH.