Surface coating and functionalization of metal and metal oxide nanoparticles for biomedical applications

As a research area, biomedical science is growing at a fast pace and promises to provide solutions for early diagnosis, targeted therapy, and personalized medicine. Most nanomaterials have limited uses in biomedical applications due to their toxicity and poor physicochemical properties. Medicines rely on drugs which are not inherently effective, with the action of drugs directly dependent on the route of delivery and feasibility of reaching the site of action. Bare metals (gold, silver, noble metals) and metal oxides (iron oxide, aluminum oxide, zinc oxide, and titanium oxide) are limited by their inability to reach the site of interest. One of the best techniques to overcome this limitation is surface modification through coating or functionalization of metal and metal oxide nanoparticles. Functionalization further allows for the introduction of stimuli-responsive behavior which increases the therapeutic action and effective biomedical applications. The major objective of this chapter is the functionalization of metals and metal oxides. Metal and metal oxide functionalization strategies for biomedical applications are discussed. Especially, the widely used coating materials such as polymers and silica on metal and metal oxide nanoparticles are described. The authors also comprehensively discuss the promising and widely studied metal nanoparticles such as gold and metal oxide nanoparticles such as iron oxide, aluminum oxide, and zinc oxide. They conclude that the physicochemical properties of metal oxides need to be considered for functionalization and depend on the functional group and preparation method. However, chemistries and materials need to be understood for successful functionalization.