الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Nanotechnology is one of the most intensely studied area of the early 21st century. The development of nanotechnology signifies a revolutionary change in modern science and engineering that promise to redesign the world that we live in.
Nanotechnology involves the creation and manipulation of materials at nanoscale levels (1–100 nm) to create products that exhibit novel properties (Hussain et al., 2005). It is rapidly growing that nanoparticles are produced and utilized in a wide range of commercial products throughout the world (Ahamed et al., 2010).
Nanotechnology has gained a great deal of public interest due to increasing applications of nanomaterials in many areas of human endeavors such as industry, agriculture, business, medicine, public health etc (Shang et al., 2014).
1.2. Nanomaterials and nanoparticles (NPs)
Nanomaterials and nanoparticles (NPs) are particulate dispersions or solid particles defined by their small size (≤ 100 nm) and their novel physicochemical properties, including a large specific surface area and high reaction activity (Yan et al., 2012).
Due to these unique characteristics, nanomaterial’s and nanotechnologies are receiving intensively increasing interest in the related research and industrial applications (Nel et al., 2006); food and cosmetic products (Calzolai et al., 2012); gene delivery (Li et al., 2012; Sanz et al., 2012); cancer treatment and diagnostic tools (Xu et al., 2012a; Gao et al., 2012).
The first studies in 1970s used nanoscale drug carriers, such as liposome entrapping antitumor pharmaceuticals. Also, they have a great potential in biology, in medicine, as well as they have been used as pharmaceutical carriers to enhance the in vivo antitumor efficacy of drugs (Felice et al., 2014; Fernandes et al., 2015). Caputo et al. (2014) declared that the NPs may act on the tumor environment such as blood vessels or stroma to reduce the development of tumor mass and progression as a consequence of their antioxidant capacities.
1. 3. Physicochemical properties of nanomaterials
The key factors in hazard evaluation after exposure to bulk materials are chemical composition, dose and exposure route. It is well known that most of the novel properties of nanomaterials are related to their size. Also, additional factors are added, including nanoscale; nano surface, dissolution, self-assembled, quantum effects, nanostructures, concentration and aggregation (Yan et al., 2011).
The surface properties of NPs can be adjusted via the functionalization of NPs with functional molecules (Lu et al., 2007). These functionalized NPs have better dispersity in aqueous solutions, which prevents the loss of most of the size dependent effects. If surface properties cannot be controlled, NPs might quickly agglomerate into larger particles and easily interact with biomolecules and organs, possibly resulting in toxicity (Ge et al., 2011).
Introduction
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1. 4. Benefits of nanotechnology
Based on its broad sectors of applications, nanotechnology has numerous benefits globally both in developed and undeveloping countries. These include:
• Creation of new products and improvement on existing products.
• Availability of stronger, tougher and lighter materials for construction and engineering.
• Cleaner drinking water due to the creation of filters that can entrap organisms and toxins.
• Cleaner environment through remediation to remove pollutants from the environment
• Improved healthcare by fabrication of devices and drug delivery systems for better monitoring, diagnosis and treatment of chronic diseases.
• Improvement on transport systems
• Cheaper and clean energy
1. 5. Nanotoxicology
The rising commercial use and large-scale production of engineered NPs may result in unintended exposure to human beings and the environment. Therefore, it is of great importance to understand how these factors affect nanomaterial toxicity.
The industrial applications as well as the unintended exposure of the occupational workers to the nanomaterials via inhalation, dermal absorption or gastrointestinal tract absorption may increase risk of these nanomaterials (Huang et al., 2010).
The nanoparticles when ingested into the body can be distributed to different regions because of their small size. They can cross small intestine and further distribute into the blood, brain, lung, heart, kidney, spleen, liver, intestine and stomach (Hillyer and Albrecht, 2001).
Toxicological studies suggest that nanomaterials may cause adverse health effects. Thus, the interaction of them with the biological systems including living cells has become one of the most urgent areas of collaborative research in materials science and biology (Nel et al., 2006; Medina et al., 2007).
Size is one of the key factors influencing the toxic effect of NPs. Several studies have reported that nano sized particles always showed more serious toxicity than bulks (Kasemets et al., 2009). Size of the nanoparticles is directly correlated to many essential properties, such as surface property, solubility and chemical reactivity (Fig. 1). Some of them have effects on the interactions between nanomaterilas and biomolecules that subsequently affect the nanotoxicological behaviors of the NPs in vivo (Zhao et al., 2007). For example, decreasing size results in an increasing nanoparticle’s specific surface area. This promotes not only the accumulation of NPs, but also an increase of reactivity and enhanced interactions between NPs and biomolecules (Peng et al., 2011).