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Nanotechnology is an evolving technology that has been researched for numerous uses, from material science to life science. A widely used description by National Nanotechnology Initiative, USA, defines nanotechnology as the designing, synthesis, and characterization of materials and structures smaller than 100 nanometers (nm in size or output limit), by controlling the shapes and sizes at the nanoscale (Parappurath et al. 2018; Bayda et al. 2020). The size of 100 nm, however, is not a rigid boundary; it varies depending on the application (McDonald et al. 2015). Recently, the design and manufacture of nanotechnology have risen, including nanoscience, nanomaterials, nanoparticles, nanomedicine, and nanotoxicology. The branch of science dedicated to the study of the peculiar properties of matter at the nanoscale is known as nanoscience (Bayda et al. 2020). The structures made up of aggregated or unbound nanoparticles apply to nanomaterials. As per the International Organization of Standardization, nanoparticles (NPs) are particles whose sizes in one, two, or three dimensions are within the range from 1 to 100 nm (Jeevanandam et al. 2018). Their measurements are equivalent to those of biomolecules such as proteins, DNA, hemoglobin, viruses, and cell membranes. Some of the significant and special characteristics of NPs are higher surface‐to‐mass ratios than the bulk material, altered quantum properties, and their ability to adsorb and hold other substances such as drugs, probes and proteins. They are both present in nature and can be produced by traditional industrial processes and techniques of nanomanufacturing (Shubhika 2013). The nanomaterials are classified based on diverse parameters such as dimensionality, morphology, composition, uniformity, agglomeration rate, and origin (Buzea and Pacheco 2017; Jeevanandam et al. 2018; Trotta and Mele 2019; Khan 2020) as tabulated in Table 1.1.

Nanotechnology employs novel, specific, and selective medicinal products at the nanoscale in the healthcare sector to develop nanomedicines. Nanomedicine is an emerging subdivision of nanotechnology that plays an important role in disease detection, surveillance, prevention, and remediation. The term nano means minuscule, extremely small; so, nanomedicine is concerned with drug formulations in the nano range of sizes (nanoformulations). The nanoformulations can be utilized for delivery of an impressive range of therapeutic drugs by encapsulation or attachment on the surface for a targeted, sustained, and controlled release to almost any tissue/organ/area of the body (Mukherjee et al. 2014; Krukemeyer et al. 2015; Ventola 2017; Fadeel and Alexiou 2020). Possible applications include: nanorobots, nanoscale medicines and targeted delivery of medicines, nanocarriers for drug delivery such as nanocrystal, polymeric NPs, magnetic NPs, mesoporous silica NPs, liposomes, micelles, dendrimers, quantum dots, iron oxide, carbon nanotubes, antimicrobial medical dressings, in vivo imaging techniques, bone and dental prostheses, tissue regeneration, etc. Nanotechnology also enables better identification and understanding of biomarkers. Further, benefits achieved are analysis of the disease stage, three‐dimensional (3D) nanomaterials for injury site, immobilized stem cells, blood glucose metering, delivery of insulin, guided implantation, etc. The financial implications of the use of nanotechnology in medicine were projected to rise to $528 billion by 2019 and will continue to grow dramatically in the coming years, according to recent industry forecasts. Further development in this field enables technology for patient‐specific, targeted, and regenerative medicine (Farjadian et al. 2019).

Table 1.1 An overview of the classification of nanomaterials based on various parameters with a few examples and applications.

Sources: Based on Buzea and Pacheco (2017), Jeevanandam et al. (2018), Trotta and Mele (2019) and Khan (2020).

Parameter	Classes	Examples	Applications
Dimensionality	Zero‐dimensional (0D)	Quantum dots Dendrimers Fullerenes	Cell marker, emulsifier in solution, reinforcement filler within a solid matrix
	One‐dimensional (1D)	Nanowires Nanotubes Nanofibers Nanorods	Electronics, magnetism, optics, and catalysis
	Two‐dimensional (2D)	Thin films Nanocoatings Nanoplates	Optoelectronics, catalysts, sensors, solar cells, energy storage facilities
	Three‐dimensional (3D)	Nanocomposites (nanofillers in bulk matrix composed of ceramics, metals, or polymers) Nanostructured materials (nanoporous structures as aerogels, block polymers, nanostructured metals and alloys)	Packaging materials, shape‐memory materials, coatings with nanoprotrusions, catalysts
Morphology	Low aspect ratio	Nanospheres, nanocubes, nanopyramids	Biomedical applications, plasmonic sensing platform (silver nanocube), optical applications
	High aspect ratio	Nanowires, nanotubes, nanobelts, nanofibres	Separation and isolation of specific analyte from complex mixtures, targeted delivery, magnetic resonance imaging
Chemical compositiona	Metal and metal alloys	Silver	Medical diagnostic, antibacterial, conductive, and optical applications
	Copper	Catalyst, lubricant additive, electrical and thermal conductor, antibacterial agent
	Gold	Drug delivery, medical testing, cancer detection, electronics
	Iron	Bactericide in water treatment, superparamagnetic in drug delivery, data recording, and magnetic detection
	Aluminum–magnesium/titanium–aluminum alloys	Aerospace and high‐temperature applications
Metal oxides	Titanium dioxide	Filter for cosmetics, chemical catalyst for cleaning product and wall paint, antibacterial agents for filtration devices
	Zinc oxide	Catalytic, antibacterial, antistatic agent
	Nanosilica	Hollow carrier for drug delivery
	Iron oxides	Biomedical and electronic applications
Semiconductors	Nanosilicon, gallium nitride, nanoflowers, nanocolumns	Photovoltaic and optoelectronic applications
Silicates, carbonates and nitrides	Clay, calcium carbonate, Silicon nitride	Filler in composites
Carbon nano‐objects	Graphene Carbon nanotubes Carbon nanofibers Fullerenes Carbon black	Biosensors, Scaffolds for bone growth, Scanning electron microscope tips, Antiaging cosmetics, contrasting agents for medical imaging, Heat and electricity conductor, antistatic agent
Polymers	Nanospheres Nanofibers Nanoporous membranes	Barrier membranes, membrane for fuel cells, antibacterial textiles, optical components, filtration membranes, reinforcement of structural composites
State	Uniformity	Isometric and inhomogeneous	—
Agglomeration	Agglomerates and dispersed	—
Origin	Natural	Natural nanostructures present in microorganisms like bacteria, viruses and algae; complex organisms like plants, insects, birds, animals, and humans	Nanomaterials in insects helps them to stay alive in adverse environmental conditions, Plant‐based nanomaterials acts as a source of cellular biocomposites, Nanomaterials in the human body help to perform normal physiological functions
Incidental	Natural nanoparticles produced by photochemical reactions, volcanic eruptions, and forest fires	—
	Engineered	Metals, quantum dots, sunscreen pigments, nanocapsules	Cosmetic products, personal care products, nutraceuticals, health supplements, medical imaging
Applications in medicine	Solid‐drug nanoparticles	Nanocrystals Nanosuspensions	Delivery of immunosuppressant drug sirolimus (Rapamune®), antiemetic aprepitant (Emend®), antihyperlipidemic fenofibrate (Tricor®)
Polymer therapeutics	Polymer‐protein conjugates Polymer‐drug conjugates Polyplexes	Delivery of asparaginase in treatment of leukemia, non‐Hodgkin’s lymphoma, acute lymphoblastic leukemia (Oncaspar®) Delivery of glatiramer acetate for treating relapsing multiple sclerosis (Copaxone®) Delivery of methoxy polyethylene glycol‐epoetin beta in treatment of anemia I associated with chronic kidney disease (Mircera®)
Nanocarriers	Polymer nanoparticles (solid polymer nanoparticles and nanogels)	Delivery of paclitaxel as albumin polymer nanoparticle (Abraxane®)
Metal nanoparticles (gold nanoparticles, iron nanoparticles, and silver nanoparticles)	Gold, iron, and silver nanoparticles have diagnostic (biosensors), conductive (inks and composites) and optical (metal enhanced fluorescence and surface‐enhanced Raman scattering) applications (especially iron oxide nanoparticles are favored to obtain enhanced contrast in MRI imaging)
Solid lipid nanoparticles Nanostructured lipid carriers Nanoemulsions Self‐assembled structures (polymer micelle, liposome)	Delivery of estradiol hemihydrate as nanoemulsion in treatment of some symptoms of menopause (Estrasorb®) Delivery of doxorubicin as PEGylated liposomal injection (Doxil®)
	Others (nanomaterial itself act as a therapeutic agent)	Dendrimers Virusomes Silver nanoparticles	VivaGel® antibacterial and antiviral dendrimer, Delivery of vaccine (influenza vaccine Inflex V®; Hepatitis vaccine Epaxal®), Antibacterial silver nanoparticles (wound dressing)
Potential toxicity level	Rigid and biopersistent	Fiber‐like nanoparticles: carbon nanotubes with and without asbestos like effects, fiber‐like metal oxides	—
	Granular and biopersistent	Titanium dioxide, silica, zinc oxide, nanoclay, fullerenes, dendrimers, aluminum oxide	—
	CMAR (carcinogenic, mutagenic, asthmagenic, reproductive toxin)	Nickel, cadmium containing quantum dots, arsenic, zinc chromate	—

^a As per chemical composition, nanomaterials are also classified as organic (liposomes, micelle, polymeric nanoparticles, dendrimer); inorganic (quantum dot, mesoporous silica nanoparticle, gold nanoparticle, silver nanoparticles); carbon‐based (carbon nanotube, graphene, fullerene, graphene); composite‐based (polymer/ceramic nanocomposites, metal/metal nanocomposites, carbon/metal nanocomposites).

More than 30 years of research work has been conducted and a vast number of scientific research articles published about nanomedicine, but only a handful of nanoformulations have received marketing approval or been identified to enter clinical trials for different applications, including the diagnosis and treatment of multiple cancers and the treatment of infections and other noncancerous diseases (McGoron 2020). Thus, this represents the fundamentally high degree of regression of nanomedicine's path from laboratory to market due to the unique properties of nanomaterials, lack of safety knowledge, risk control methods, and their effective management. Consequently, any nanomedicine that enters the market must be of high quality, healthy, and efficient. Without activating any undesired reaction, in particular populations, NPs and other nanomaterials in the field of nanomedicine are supposed to exhibit an acceptable response. Unfortunately, the properties which make NPs appealing for the development of nanomedicine may also prove extremely harmful in cell interaction (Mukherjee et al. 2014). Nanotoxicology is an evolving toxicology specialty which accesses the toxicological properties of nanomaterials through various in vitro and in vivo tests using cell‐ or animal‐based models and provides evidence for the safety evaluation of this nanomaterial and its applications. The entire life cycle of nanomedicines, including the production, disposal, and environmental impact, should be considered when weighing the benefits and risks; for example, the estimation of various disposal pathways. A thorough biosafety evaluation of therapeutic nanomaterials will make a major contribution to risk control for the continuing growth of nanomedical technology, which is so urgently needed to ensure that they are produced carefully, fully exploited, and then disposed of safely. In deliberate partnership with nanomedicine, nanotoxicology will help advance the field of nanomedicine by offering information on its harmful properties and methods of preventing them (Sharma et al. 2018).

This chapter will include insights into emerging nanomedicines, numerous diagnostics, drug delivery, and tissue engineering and regenerative medicine applications of nanomedicine. Finally, it would also discuss the nanotoxicological characteristics that impede nanomedicine's clinical transformation from bench to bedside, and expect that nanomedicine will progress to the next stage, and through rationally organized and systematic methods, deliver practical and substantial benefits to human medicine and healthcare.