Biogenic synthesis of silver nanoparticles using guava (Psidium guajava) leaf extract and its antibacterial activity against Pseudomonas aeruginosa

While metal nanoparticles are being increasingly used in many sectors of the economy, there is growing interest in the biological and environmental safety of their production. The main methods for nanoparticle production are chemical and physical approaches that are often costly and potentially harmful to the environment. The present review is devoted to the possibility of metal nanoparticle synthesis using plant extracts. This approach has been actively pursued in recent years as an alternative, efficient, inexpensive, and environmentally safe method for producing nanoparticles with specified properties. This review provides a detailed analysis of the various factors affecting the morphology, size, and yield of metal nanoparticles. The main focus is on the role of the natural plant biomolecules involved in the bioreduction of metal salts during the nanoparticle synthesis. Examples of effective use of exogenous biomatrices (peptides, proteins, and viral particles) to obtain nanoparticles in plant extracts are discussed.

In the present Communication, a completely "green" synthetic method for producing silver nanoparticles is introduced. The process is simple, environmentally benign, and quite efficient. By gentle heating of an aqueous starch solution containing silver nitrate and glucose, we produce relatively monodisperse, starched silver nanoparticles. beta-d-Glucose serves as the green reducing agent, while starch serves as the stabilization agent.

Plants respond to heavy metal stress by metal complexation process like production of phytochelations or by other metal chelating peptides. In this paper we report the synthesis of silver nanoparticles (AgNPs) from the room dried stem and root of Ocimum sanctum. The broth of the plant is used as a reducing agent for the synthesis of Ag nanoparticles at room temperature. The reaction process was simple and was monitored by ultraviolet-visible spectroscopy (UV-vis). There was formation of highly stable silver nanoparticles in the solution. The morphology and crystalline phase of the NPs were determined from transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. Transmission Electron Microscopy studies showed that the silver nanoparticles obtained from roots and stem were of sizes 10+/-2 and 5+/-1.5 nm, respectively. The various phytochemicals present within the ocimum plant result in effective reduction of silver salts to nanoparticles but their chemical framework is also effective at wrapping around the nanoparticles to provide excellent robustness against agglomeration. Copyright (c) 2010 Elsevier B.V. All rights reserved.