Photosynthetic Electron Transport System Promotes Synthesis of Au-Nanoparticles

Abstract

In this communication, a novel, green, efficient and economically viable light mediated protocol for generation of Au-nanoparticles using most vital organelle, chloroplasts, of the plant system is portrayed. Thylakoids/chloroplasts isolated from Potamogeton nodosus (an aquatic plant) and Spinacia oleracea (a terrestrial plant) turned Au3+ solutions purple in presence of light of 600 µmol m−2 s−1 photon flux density (PFD) and the purple coloration intensified with time. UV-Vis spectra of these purple colored solutions showed absorption peak at ∼545 nm which is known to arise due to surface plasmon oscillations specific to Au-nanoparticles. However, thylakoids/chloroplasts did not alter color of Au3+ solutions in dark. These results clearly demonstrated that photosynthetic electron transport can reduce Au3+ to Au0 which nucleate to form Au-nanoparticles in presence of light. Transmission electron microscopic studies revealed that Au-nanoparticles generated by light driven photosynthetic electron transport system of thylakoids/chloroplasts were in range of 5–20 nm. Selected area electron diffraction and powder X-ray diffraction indicated crystalline nature of these nanoparticles. Energy dispersive X-ray confirmed that these nanoparticles were composed of Au. To confirm the potential of light driven photosynthetic electron transport in generation of Au-nanoparticles, thylakoids/chloroplasts were tested for their efficacy to generate Au-nanoparticles in presence of light of PFD ranging from 60 to 600 µmol m−2 s−1. The capacity of thylakoids/chloroplasts to generate Au-nanoparticles increased remarkably with increase in PFD, which further clearly demonstrated potential of light driven photosynthetic electron transport in reduction of Au3+ to Au0 to form nanoparticles. The light driven donation of electrons to metal ions by thylakoids/chloroplasts can be exploited for large scale production of nanoparticles.

Mitochondrial electron transport protects floating leaves of long leaf pondweed (Potamogeton nodosus Poir) against photoinhibition: comparison with submerged leaves

“…1). Sensitivity of PS II-mediated photoreactions in terrestrial/aquatic plant species to high PFD is well known (Demmig and Björkman 1987;Pardha-Saradhi et al 2000;Sharmila et al 2009;Shabnam and Pardha-Saradhi 2013). The potential of floating leaves to withstand photodamage is also evident from data on Chl a fluorescence transients.…”

Light Mediated Generation of Silver Nanoparticles by Spinach Thylakoids/Chloroplasts

“…The filtered extract was centrifuged at 5000 xg at 4°C for 10 min and the resultant pellet containing thylakoids/chloroplast was suspended in distilled water instead of phosphate buffer as AgNO 3 forms white precipitate with phosphate buffer. Thylakoids/Chloroplasts were washed 4 times with distilled water, through repeated suspension and centrifugation, to remove biomolecules like phenolics, sugars, free amino acids etc., which are known to promote generation of NPs [6,7,9]. The levels of chlorophyll, phenolics, sugars and amino acids were determined as described earlier [8,10].…”

“…Although extracts of various plants/microbes are effective in generation of Ag-NPs, their use has been limited due to vast heterogeneity (in terms of size, shape and composition) of NPs generated. The vast heterogeneity results due to the presence of wide variety/range of biomolecules such as sugars, organic acids including amino acids, phenolics, soluble proteins etc., most of which have potential to generate metal nanoparticles [1–7]. …”

“…It is well established that light-harvesting photosynthetic machinery has immense potential to extract, energize and transport electrons from water to reduce various entities, which include NO 2 - , SO 4 2- and O 2 , besides the key terminal acceptor, NADP + [7,8]. This prompted us to evaluate if this potential of light-harvesting photosynthetic machinery to extract, energize and donate electrons can be exploited for reduction of Ag + .…”

Phytosynthesis of gold nanoparticles using Mappia foetida leaves extract and their conjugation with folic acid for delivery of doxorubicin to cancer cells

“…Metal nanoparticles (MNPs) in general find widespread applications in engineering, medicine, environment and agricultural sectors owing to their unique physical and chemical properties [1][2][3]. The biocompatible gold nanoparticles (AuNPs) have been studied as biosensors, diagnostic agents, cell targeting vectors, heating mediators for cancer thermotherapy and drug delivery vehicles [4][5][6].…”