In this chapter, the authors explore the discovery and use of nanocompostite metal oxides in medicine. I was fortunate enough to work on Pt/TiO2 for the U.S. Department of Energy and The Japanese National Institute of Technology and Science during the early 21st Century. Part of our work was cited and then quoted in this chapter. I want to thank the authors for doing so.
Chapter 16 – Metal Oxide–Based Nanocomposites as Antimicrobial and Biomedical Agents
SHESAN JOHN OWONUBI • NYEMAGA MASANJE MALIMA • NEERISH REVAPRASADU
The spread of infectious diseases, the advent of multidrug-resistant microbes, and antibiotic-resistant diseases are threats to the global population, subject of considerable interest, and tremendous scientific chal- lenge to the pharmaceutical and biomedical industry. The magnitude of antibiotic resistance may stir concern about the outgrowth and recurrence of microbial infec- tions that are resistant to more than one drug . It is noteworthy to mention that, in most cases, people infected with multidrug-resistant microbes do not recover easily as they are mostly confined to hospitals requiring several treatments with different types of anti- biotics that are more expensive, less effective, and toxic . Hence, great demand exists to develop or modify antimicrobial agents to improve their performance in this era of advanced science and technology . Against the backdrop of many technologies available for the development or modification of antimicrobial agents, nanotechnology is highly attractive as it affords re- searchers of today a worthy platform to maneuver the vital properties of materials, for example, metal oxides, by transforming them into nanoparticles or related nanocomposites. The materials at nanoscale possess promising practical applications, and this has been proven to be useful in different treatment modalities including cell labeling diagnostics, biomarkers, targeted drug-delivery systems, nanodrugs for treatment of various diseases, antimicrobial agents, and contrast agents for biological imaging [4,5], tumor detection, and prognostic visual monitoring of therapy [6,7].
The search for sustainable methods to modernize medicine by the application of nanotechnology and the increase in demand for nanotechnology-derived products for improving human health has prompted researchers in the health industry to explore nanomate- rials with superior flexibility, strength, performance,
durability, and in some cases unique physicochemical properties. Recently, interest in the design of antimicro- bial metal oxideebased nanocomposites (MOBNCs) has been on the rise. This is because the incorporation of metal oxide nanoparticles in composites has shown to yield advantages of being higher in performance, an unusual combination of properties as well as unique design possibilities . MOBNCs have been shown to be beneficial in biomedicine; in gene therapy; DNA sequencing; diagnosis and screening of diseases; for delivery of drugs and imaging; tissue culturing and in cancer treatment [9,10].
The major highlight of this chapter is to present a general idea on MOBNCs, their synthetic and character- ization protocols as well as their antimicrobial potential. The development of consumer and healthcare products that possess antimicrobial properties can be achieved through the fabrication of products that encompass these metal oxide nanocomposites with potential to inactivate microbes. Finally, we present the antimicro- bial and biomedical applications of these MOBNCs.
2 METAL OXIDES
Inorganic metal oxides are among the many groups of nanomaterials that have been proven to be of great in- terest both scientifically and technologically . Metal oxides can be insulators, semiconductors, or metallic, dependent on the electronic structure nature. The trans- formation of metal oxides from bulk into nanometre size significantly improves their hybrid properties compared to the original forms. Their peculiar features permit them to become multifaceted materials, possess- ing distinct electrical, catalytic, photoelectronic, optical, and magnetic properties covering practically all facets of materials science and solid-state physics, thus finding applications in superconductors, catalysis, gas sensing,
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electroceramics, and energy conversions . Over the years, a number of metal oxides, zinc oxide (ZnO), titanium (IV) oxide (TiO2), nickel oxide (NiO), copper (I) oxide (Cu2O), copper (II) oxide (CuO), manganese (IV) oxide (MnO2), Iron (III) oxide (Fe2O3), tungsten trioxide (WO3), and cerium oxide (CeO2) have been used in the architecture of nanomaterials and nano- composites [8,13e15].
Nanocomposites refer to solid materials with two or more phase domains having distinguishable physical and chemical properties wherein at least one of these domains has a nanoscale structure that ranges in sizes from 1 to 100 nm [16,17]. The physicochemical properties of these nanomaterials are dependent on the interfacial characteristics and morphology of the constituent materials. In contrast to the individual ma- terials, composites have extraordinarily good practical applications because of their improved toughness, high thermal insulation, low density, corrosion to resistance, stiffness, and strength . The design of nanocomposites was encouraged by the quest for com- posite materials with enhanced properties and having filler sizes that are smaller.
Recently, the development of nanocomposites has received considerable attention making them important materials, both to academia and industry because they normally inherit the behavior of the constituent materials, and in some cases even yield multifunctional materials with surprisingly enhanced characteristics. Nanocomposites can be synthesized from a combina- tion of three main precursor materials that are classified into metals, ceramics, and polymers. The nanocompo- site could differ in properties from its parent component materials in optical, thermal, catalytic, electrical, electro- chemical, and mechanical properties [16,17,19e21].
Nanocomposite materials can be in the form of mixed oxides wherein there is a solid solution made from mixed oxides, examples of such are titania (TiO2)/tin oxide (SnO2) nanocomposites; mixed oxides that form distinctive chemical compounds like zinc cobaltite (ZnCo2O4) and zinc stannate (ZnSn2O4); systems that do form solid solutions such as TiO2/ WO3 nanocomposites; and those that form core/shell…”
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