however many others are making excellent progress toward clinical translation. Some of the important organic and inorganic nanomaterials commonly used in diagnosis, drug delivery, and treatment of a wide range of diseases are briefly discussed here.
1.2.1 Inorganic Nanomaterials
Different inorganic nanomaterials discussed in the chapter have been successfully exploited directly or indirectly in the diagnosis and management of various diseases.
1.2.1.1 Colloidal Metal Nanoparticles
Different colloidal metal nanoparticles (Figure 1.1a) have been reported as having potential applications in diagnosis, drug delivery, and treatment of many diseases. However, among the colloidal metal nanoparticles, colloidal gold nanoparticles (GNPs) are recognized as suitable nanocarriers for biomedicine, i.e. for the intracellular and in vivo delivery of genes, drugs, and as contrast agents because of their easy synthesis, large surface area, and flexible surface chemistry (Lewinski et al. 2008; Jeong et al. 2019). Moreover, these nanoparticles can be easily modified by conjugating smart polymers in order to develop novel drug delivery systems that have the ability to release their payload in response to outside stimuli (Yavuz et al. 2009; An et al. 2010). Furthermore, due to the above‐mentioned novel properties and their high molar absorption coefficient, GNPs can be directly or indirectly used for the diagnosis and management of various diseases including photothermal agents in cancer photothermal therapy (Liang et al. 2014). In addition, there are other metal nanoparticles like silver, copper, etc., that were potentially used as novel antimicrobial agents due to their promising antimicrobial properties.
Figure 1.1 Schematic illustration of various inorganic nanomaterials.
1.2.1.2 Mesoporous Silica Nanoparticles
Mesoporous silica nanoparticles (MSNPs) are another important group of inorganic nanomaterials (Figure 1.1b). These nanoparticles are also considered ideal candidates for biomedical applications due to their controllable morphologies, mesostructures with biocompatibility, and easy functionalization ability (Dykman and Khlebtsov 2012; Liu and Xu 2019). The presence of numerous silanol groups on the surface of MSNPs make them hydrophilic; moreover, their functionalization using a variety of groups helps to achieve controlled holding/release of cargo molecules. In addition, the large internal surface area and pore capacity of mesoporous materials allow a high loading of cargo molecules and also prevent them from escaping into water easily by dissolving in an aqueous environment (Jafari et al. 2019). These advantages enhance the effectiveness of the MSNP‐based delivery system and allow a specific amount of drugs to reach their therapeutic target (Li et al. 2012).
1.2.1.3 Superparamagnetic Nanoparticles
Among the inorganic nanoparticles, superparamagnetic nanoparticles (Figure 1.1c) are considered the most unique nanoparticles due to their strong magnetic properties. These nanoparticles were for the first time used in the late 1980s for biomedical applications (Stark et al. 1988). Usually, the core of these nanoparticles consists of metal molecules of nickel, cobalt, or iron oxide (Fe3O4 magnetite, which is the most commonly used metal). As mentioned above, superparamagnetic nanoparticles are considered most unique because the surface of these nanoparticles can be easily modified by coating the core with various organic polymers like dextran, starch, alginate, inorganic metals, oxides (silica, alumina), etc. (Núñez et al. 2018).
Superparamagnetic nanoparticles can be promisingly used for the diagnosis of various diseases including cancer (tumors) by conjugating with various bioactive ligands (Anderson et al. 2019). To date, a number of approaches have been developed for the fabrication of superparamagnetic nanoparticles which have the potential ability to distinguish cancerous tissue from healthy tissue. In addition, these nanoparticles can be used for magnetic resonance imaging (MRI) of tumor tissue, cell labeling, and drug delivery in different diseases (Núñez et al. 2018; Anderson et al. 2019).
1.2.1.4 Quantum Dots
Quantum dots (Figure 1.1d) are the class of semiconductor nanoparticles with unique photo‐physical properties. Usually, quantum dots have a core/shell structure composed of molecules of various metals like technetium, cadmium selenide, zinc, indium, tantalum, etc. (Medintz et al. 2005; Wang et al. 2019). The most commonly used, commercially available quantum dots contain a cadmium selenide core covered with a zinc‐sulfide shell. The core‐shell complex is generally encapsulated in a coordinating ligand and an amphiphilic polymer (Gao et al. 2004). Due to unique optical properties, quantum dots have been used as dominant classes of fluorescent imaging probes for various biomedical applications (Núñez et al. 2018).
1.2.1.5 Graphene
Graphene is an atom‐thick monolayer of carbon atoms arranged in a two‐dimensional honeycomb structure (Figure 1.1e) (Novoselov et al. 2004). Generally, graphene has been extensively used for a wide array of applications in many fields such as quantum physics, nanoelectronic devices, transparent conductors, energy research, catalysis, etc. (Wang et al. 2011; Huang et al. 2012). However, according to recent technological advancements graphene, graphene oxide, and reduced graphene oxide have shown promising applications in the biomedical field and hence have attracted significant interest worldwide (Gonzalez‐Rodriguez et al. 2019; Yang et al. 2019). Due to its excellent physicochemical and mechanical properties, single‐layered graphene has been widely utilized as a novel nanocarrier for drug and gene delivery in different diseases (Núñez et al. 2018).
1.2.1.6 Carbon Nanotubes (CNTs)
CNTs are cylindrical nanomaterials that consist of rolled‐up sheets of graphene (single‐layer carbon atoms). Depending on their structure CNTs can be divided into two types, namely single‐walled carbon nanotubes (SWCNTs) (Figure 1.1f), which usually have diameter of less than 1 nm, and multi‐walled carbon nanotubes (MWCNTs) (Figure 1.1g), which are composed of many concentrically interlinked nanotubes, usually having a diameter size of more than 100 nm (Hsu and Luo 2019). CNTs are considered as one of the stiffest and strongest fibers having novel exceptional characteristics and a unique physicochemical framework, which makes them suitable candidates for efficient delivery of different therapeutic drugs/molecules for various biomedical applications (Vengurlekar and Chaturvedi 2019). Figure 1.1 represents the schematic illustration of various inorganic nanomaterials.
1.2.2 Organic Nanomaterials
1.2.2.1 Polymeric Nanoparticles
Polymeric nanoparticles (Figure 1.2a,b) are colloidal solid particles having a size in the range of
