11. Nanostructured Functional Materials: Silver Nanoparticles in Polymer for the Generation of Antimicrobial Characteristics

The application of nanosized and nanostructured materials in ordinary life is the other side of the coin that emerged from the scientific progress. It established a new interdisciplinary point of view about the behavior of atoms and molecules at a very small scale, leading to an unprecedented understanding over several aspects of the matter and a whole knowledge on its fundamental properties never imagined before. These nanomaterials provide innovative solutions in technological and environmental fields related to solar energy conversion, catalysis, medicine, and water treatment. Usually, these novel and enhanced characteristics that are easily found in metallic nanoparticles are related to their high surface-to-volume ratio. In this sense, silver nanoparticles have been the subject of substantial research especially for medical and health applications. For decades, people have been using colloidal silver for their own health benefits, but detailed studies on its effects in the environment have only recently begun. Initial studies demonstrated that cells and microbes are primarily affected by low levels of silver ion (Ag⁺) released from the nanoparticle. Due to the increasing use of silver nanoparticles in products for daily use, such as in shampoos, soaps, detergents, cosmetics, toothpastes, and medical and pharmaceutical products, there has been a major effort worldwide to assess the safety of using silver nanoparticles and to understand how these nanoparticles effectively kill several microorganisms. Silver has been considered as a potential disinfectant in many investigations due to its intense antimicrobial activity and low toxicity to mammalian cells and tissues. It is one of the most powerful natural disinfectants known, reason by which its deposition onto prosthetic device surfaces (e.g., catheters, heart valves, etc.) would be an attractive approach for preventing bacterial attachment and biofilm formation, which can lead to serious infections. Another potential application could be in food processing equipment and packaging materials, where the presence of undesirable bacteria can cause food spoilage and foodborne diseases. For this reason, an increasingly common application is the use of silver nanoparticles for antimicrobial coatings, many textiles, polymer, and biomedical devices that contain silver nanoparticles to provide protection against bacteria and fungi. Silver nanoparticles coated in the polymer matrix increase the efficiency of antimicrobial action with a controlled release of Ag⁺. The combination of silver with polymeric material reduces the transmission of the infectious agent. This chapter will describe nanostructured functional polymer materials containing silver nanoparticles for the generation of antimicrobial characteristics.