ISSN 1011 5528 | www.smltsa.org.za 13 Volume 29 No. 2 | December 2015 Medical Technology SA Peer reviewed REVIEW Biomedical applications and toxicity of nanosilver: a review KSB Naidu 1 PhD (Biochemistry) | P Govender 2 PhD (Biochemistry) | JK Adam 1 PhD (Clinical Technology) 1 Department of Biomedical & Clinical Technology, Durban University of Technology, South Africa 2 Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, South Africa Corresponding author: Jamila K Adam | tel: +27 31 3735291 | email: adamjk@dut.ac.za ABStRAct Nanotechnology is a promising arena for generating new applications in medicine. It is advancing rapidly due to the great progress achieved in various ileds including electronics, machanics, cosmetics, food, etc. In order to successfully bifunctionalise nanoparticles for a given biomedical application, a wide range of chemical, physical and biological factors have to be taken into account. Silver nanoparticles (AgNPs) exhibit strong antibacterial activity owing to their large surface to volume ratios and crystallographic surface structure. Nanosilver particles have been widely used in a range of biomedical applications including diagnosis, treatment, medical device coatings, drug delivery and personal health care products. With the growing application of nanosilver particles in medical contexts, it is becoming necessary for a better understanding the mechanisms of action, biological interactions and their potential toxicity on exposure. This review aims to provide critical assess- ment of the current understanding of antibacterial activity, biomedical applications and toxicity of silver nanoparticles. KEyWoRdS Antibacterial, antiviral , diagnosis, toxicity, therapeutics. INtRoductIoN Nanotechnology is deined as the design, characterization and application of structures, devices and systems by controlling shape and size at nanometer scale level (ranging from 1 to 100nm). [1, 2] A nanometer is one billionth of a meter (10 - 9m). Nano-size particles of less than 100nm in diameter are cur- rently attracting increasing attention for the wide range of new applications in various ields of industry. Silver nanoparticles (nanosilver or AgNPs) have attracted increasing interest due to their unique physical, chemical and biological properties com- pared to their macro-scaled counterparts. [3] AgNPs have distinc- tive physico-chemical properties, including a high electrical and thermal conductivity, surface-enhanced Raman scattering, chemical stability, catalytic activity and non linear optical be- haviour. [4, 5] These properties are made use in production of inks, microelectronics, and medical imaging devices. [6, 7] Also, silver nanoparticles exhibit broad spectrum bactericidal and fungi- cidal activity that has made them extremely popular in a diverse range of consumer products including plastics, soaps, pastes, food and textiles, increasing their market value. [8] Furthermore, silver nanoparticles are being used as antimicrobial agents in many public places such as railway stations and elevators in China, and they are said to show good antimicrobial action. [9] According to the Project on Emerging Nanotechnologies PEN, over 1628 manufacturer-identiied, nanotechnology-enabled products have entered the commercial market place around the world from 30 different countries. Among them, there are 383 products utilizing nanosilver (24% of products listed), this has made nanosilver the largest and fastest growing class of nano- particles (Fig 1) in consumer products applications (http://www. nanotechproject.org). The broadest deinition of an antibacterial is an agent that interferes with the growth and reproduction of bacteria and antibacterial activity is related to compounds that locally kill bacteria or slow down their growth without being in general toxic to target tissue. [10] In general, agents that can slow down bacterial growth are classiied as bactericidal or bacteriostatic. Antibacterial agents are paramount to ight infectious diseases. However, with their extensive use and abuse, the emergence of bacterial resistance to antibacterial drugs has become a common phenomenon, which is a major problem leading to drug resistance. [11] Resistance is an evolutionary process tak- ing place during, for example, antibiotic therapy, and leads to inheritable resistance. In addition, horizontal gene transfer by conjugation, transduction or transformation can be a possible way for resistance to build up. [12] Antibiotics represent one of the most successful forms of therapy in medicine. But the ef- iciency of antibiotics is compromised by a growing number of antibiotic-resistant pathogens. Antibiotic-resistant bacteria that are dificult or impossible to treat are becoming increasingly common and are causing a global health crisis. In addition, drawbacks for conventional antimicrobial agents are not only the development of multiple drug resistance, but also adverse side effects. Furthermore, drug resistance enforces high-dose administration of antibiotics, often generating intolerable toxic- ity. This has prompted the development of alternative strategies to treat bacterial diseases. Among them, nanoscale materials have emerged as novel antimicrobial agents. Especially, sev- eral classes of antimicrobial NPs and nanosized carriers for antibiotics delivery have proven their effectiveness for treating infectious diseases, including antibiotic-resistant ones, in vitro as well as in animal models. [13] This review in particular discuss the recent developments, current perceptive, biological actions and toxicity of silver nanoparticles. MEchANISMS of ActIoN of NANoSIlVER The utilization of silver as a disinfecting agent is not new, and