Nanoscience and Nanotechnology 2015, 5(3): 45-56 DOI: 10.5923/j.nn.20150503.01 Evaluation of Callus Responses of Solanum nigrum L. Exposed to Biologically Synthesized Silver Nanoparticles Emad A. Ewais 1,* , Said A. Desouky 2 , Ezzat H. Elshazly 2 1 Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Cairo, Egypt 2 Department of Botany, Faculty of Science, Al-Azhar University, Assiut, Egypt Abstract Effect of biosynthesized silver nanoparticles (AgNPs) on growth, anatomy, and protein and DNA of Solanum nigrum callus was investigated in vitro. Three concentrations of aqueous silver nanoparticles conjugated with camel milk were used in the present study. Murashige and Skoog (MS) nutrient media supplemented with different concentrations of AgNPs, 0, 2, 4 and 8 mg/l, were evaluated for their effects on the callus induction from the leaf explants of Solanum nigrum. Compact calli with white and greenish colour were obtained after 10 days upon control culture (no AgNPs), whereas friable watery calli with white, greenish or yellowish colour were observed after 10-13 days upon culture supplemented with AgNPs. Interestingly, it was found that exposure to AgNPs increased callus fresh weight and the intensity of callus formation. These were associated with the deformity of callus morphology. Light microscopy observations showed that the nanoparticles damaged cell wall. This was clear with the high concentration of AgNPs. Variation in protein pattern were recorded between callus control (no AgNPs) and callus exposure to AgNPs. Genetic stability between callus control and callus under AgNPs exposure was interrelated. Keywords Solanum nigrum, Silver nanoparticles, Callus anatomy, Protein and genetic stability 1. Introduction The field of nanotechnology is one of the most active areas of research in modern material science. Nanoparticles are being considered to be the fundamental building blocks of nanotechnology. Nanotechnology is interdisciplinary which includes physics, chemistry, biology, material science and medicine. Instead of using toxic chemicals for the reduction and stabilisation of metallic nanoparticles, the use of various biological entities has received considerable attention in the field of nanobiotechnology [1]. Biological methods are regarded as safe, cost-effective, sustainable and environment friendly processes for the synthesis of nanoparticles [2]. Silver nanoparticles have been successfully synthesized using various bacteria [3], fungi [4] and plants [5]. Nanoparticles are becoming an area of research interest due to their unique properties, such as having increased electrical conductivity, ductility, toughness, and formability of ceramics, increasing the hardness and strength of metals and alloys, and by increasing the luminescent efficiency of semiconductors [6]. Plants are an essential base component of all ecosystems and play a critical role in the fate and transport of AgNPs in the environment through plant uptake * Corresponding author: ewais_e@yahoo.com (Emad A. Ewais) Published online at http://journal.sapub.org/nn Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved and bioaccumulation [7]. Silver nanoparticles (AgNPs) are currently one of the most widely commercially used nanomaterials [8]. The risk of nanomaterials usage represents their possible accumulation in the environment with subsequent entry into the food chain, which is closely connected with their accumulation in organisms [9]. Plants represent an important trophic level [10]. However, there are only limited studies focused on the effect of nanomaterials on plants. The first point of possible phytotoxicity consists in interactions between nanomaterials and soil components and microorganisms, which significantly modify uptake of nutrients by plants [11]. The second point is closely connected with the uptake of nanomaterials (root, foliar), and their accumulation and transport within plant body with subsequent interactions with biomolecules, such as nucleic acids, proteins including enzymes, and cell structures, such as cell walls and biomembranes [12]. In particular the cell wall of plant cells represents a crucial structure in nanoparticle uptake compared to animal cells [13]. Both positive and negative effects on plants have been demonstrated. Lu et al. demonstrated both positive and negative effects of nano-SiO 2 and nano-TiO 2 on nitrate reductase in soybean [14]. Enhancement of biomass production in spinach (Spinacia oleracea) after application of TiO 2 nanoparticles has been recorded in a study by Gao et al., [15]. An understanding of the interactions between nanoparticles and biological systems is of significant interest.