Naheed Ahmad

Bio: Naheed Ahmad is an academic researcher from Patna University. The author has contributed to research in topics: Silver nanoparticle & Nanoparticle. The author has an hindex of 11, co-authored 18 publications receiving 1616 citations.

Biosynthesis of Silver Nanoparticles from Desmodium triflorum: A Novel Approach Towards Weed Utilization

Abstract: A single-step environmental friendly approach is employed to synthesize silver nanoparticles. The biomolecules found in plants induce the reduction of Ag+ ions from silver nitrate to silver nanoparticles (AgNPs). UV-visible spectrum of the aqueous medium containing silver ions demonstrated a peak at 425 nm corresponding to the plasmon absorbance of silver nanoparticles. Transmission electron microscopy (TEM) showed the formation of well-dispersed silver nanoparticles in the range of 5–20 nm. X-ray diffraction (XRD) spectrum of the AgNPs exhibited 2θ values corresponding to the silver nanocrystal. The process of reduction is extracellular and fast which may lead to the development of easy biosynthesis of silver nanoparticles. Plants during glycolysis produce a large amount of H+ ions along with NAD which acts as a strong redoxing agent; this seems to be responsible for the formation of AgNPs. Water-soluble antioxidative agents like ascorbic acids further seem to be responsible for the reduction of AgNPs. These AgNPs produced show good antimicrobial activity against common pathogens.

Green Synthesis of Silver Nanoparticles Using Extracts of Ananas comosus

Abstract: The biosynthesis of nanoparticles has been proposed as a cost effective and environmental friendly alternative to chemical and physical methods. Plant mediated synthesis of nanoparticles is a green chemistry approach that intercom nects nanotechnology and plant biotechnology. In the present study, synthesis of silver nanoparticles (AgNPs) or (Green-Silver) has been demonstrated using extracts of Ananas comosus reducing aqueous silver nitrate. The AgNPs were characterized by Ultraviolet-Visible (UV-vis) Spectrometer, Energy Dispersive X-ray Analysis (EDAX), Selected Area Diffraction Pattern (SAED) and High Resolution Transmission Electron Microscopy (HRTEM). TEM micrographs showed spherical particles with an average size of 12 nm. The XRD pattern showed the characteristic Bragg peaks of (111), (200), (220) and (311) facets of the face center cubic (fcc) silver nanoparticles and confirmed that these nanoparticles are crystalline in nature. The different types of antioxidants presented in the pineapple juice synergistically reduce the Ag metal ions, as each antioxidant is unique in terms of its structure and antioxidant function. The re- action process was simple for formation of silver nanoparticles and AgNPs presented in the aqueous medium were quite stable, even up to 4 months of incubation. This work proved the capability of using biomaterial towards the synthesis of silver nanoparticle, by adopting the principles of green chemistry.

Rapid Green Synthesis Of Silver And Gold Nanoparticles Using Peels Of Punica Granatum

Abstract: We present a simple and eco-friendly biosynthesis of silver nanoparticles using Pomegranate peel extract as the reducing agent. Peel extract of Pomegranate was challenged with silver nitrate (AgNO3) and chloroauric acid (HAuCl4) solution for the production of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs), respectively. The reaction process was simple for the formation of highly stable silver and gold nanoparticles at room temperature by using the biowaste of the fruit. The morphology and crystalline phase of the NPs were determined from UV-Vis spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. TEM studies showed that the average particle size of silver nanoparticles were 5 ±1.5 nm whereas the gold nanoparticles were found to be 10 ±1.5 nm. An effort has been also been made to understand the possible involved mechanism for the biosynthesis of the NPs. Presumably biosynthetic products or reduced cofactors play an important role in the reduction of respective salts to nanoparticles. Copyright © 2012 VBRI press.

The cag Pathogenicity Island of Helicobacter pylori Is Disrupted in the Majority of Patient Isolates from Different Human Populations

Abstract: The cag pathogenicity island (cag-PAI) is one of the major virulence determinants of Helicobacter pylori. The chromosomal integrity of this island or the lack thereof is speculated to play an important role in the progress of the gastroduodenal pathology caused by H. pylori. We determined the integrity of the cag-PAI by using specific flanking and internally anchored PCR primers to know the biogeographical distribution of strains carrying fully integral cag-PAI with proinflammatory behavior in vivo. Genotypes based on eight selected loci were studied in 335 isolates obtained from eight different geographic regions. The cag-PAI appeared to be disrupted in the majority of patient isolates throughout the world. Conservation of cag-PAI was highest in Japanese isolates (57.1%). However, only 18.6% of the Peruvian and 12% of the Indian isolates carried an intact cag-PAI. The integrity of cag-PAI in European and African strains was minimal. All 10 strains from Costa Rica had rearrangements. Overall, a majority of the strains of East Asian ancestry were found to have intact cag-PAI compared to strains of other descent. We also found that the cagE and cagT genes were less often rearranged (18%) than the cagA gene (27%). We attempted to relate cag-PAI rearrangement patterns to disease outcome. Deletion frequencies of cagA, cagE, and cagT genes were higher in benign cases than in isolates from severe ulcers and gastric cancer. Conversely, the cagA promoter and the left end of the cag-PAI were frequently rearranged or deleted in isolates linked to severe pathology. Analysis of the cag-PAI genotypes with a different biogeoclimatic history will contribute to our understanding of the pathogen-host interaction in health and disease.

Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects

Abstract: Silver nanoparticles are nanoparticles of silver which are in the range of 1 and 100 nm in size. Silver nanoparticles have unique properties which help in molecular diagnostics, in therapies, as well as in devices that are used in several medical procedures. The major methods used for silver nanoparticle synthesis are the physical and chemical methods. The problem with the chemical and physical methods is that the synthesis is expensive and can also have toxic substances absorbed onto them. To overcome this, the biological method provides a feasible alternative. The major biological systems involved in this are bacteria, fungi, and plant extracts. The major applications of silver nanoparticles in the medical field include diagnostic applications and therapeutic applications. In most of the therapeutic applications, it is the antimicrobial property that is being majorly explored, though the anti-inflammatory property has its fair share of applications. Though silver nanoparticles are rampantly used in many medical procedures and devices as well as in various biological fields, they have their drawbacks due to nanotoxicity. This review provides a comprehensive view on the mechanism of action, production, applications in the medical field, and the health and environmental concerns that are allegedly caused due to these nanoparticles. The focus is on effective and efficient synthesis of silver nanoparticles while exploring their various prospective applications besides trying to understand the current scenario in the debates on the toxicity concerns these nanoparticles pose.

‘Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation

Abstract: In materials science, “green” synthesis has gained extensive attention as a reliable, sustainable, and eco-friendly protocol for synthesizing a wide range of materials/nanomaterials including metal/metal oxides nanomaterials, hybrid materials, and bioinspired materials. As such, green synthesis is regarded as an important tool to reduce the destructive effects associated with the traditional methods of synthesis for nanoparticles commonly utilized in laboratory and industry. In this review, we summarized the fundamental processes and mechanisms of “green” synthesis approaches, especially for metal and metal oxide [e.g., gold (Au), silver (Ag), copper oxide (CuO), and zinc oxide (ZnO)] nanoparticles using natural extracts. Importantly, we explored the role of biological components, essential phytochemicals (e.g., flavonoids, alkaloids, terpenoids, amides, and aldehydes) as reducing agents and solvent systems. The stability/toxicity of nanoparticles and the associated surface engineering techniques for achieving biocompatibility are also discussed. Finally, we covered applications of such synthesized products to environmental remediation in terms of antimicrobial activity, catalytic activity, removal of pollutants dyes, and heavy metal ion sensing.

"Green" nanotechnologies: synthesis of metal nanoparticles using plants

Abstract: 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.