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agents (e.g. superparamagnetic iron oxide nanoparticles [SPIONs]) (Greish et al. 2018). A substantial effort has been made to develop NPs conjugated with paramagnetic ions, such as Gd3+, Mn2+, and Fe3+, as contrast agents for MRI in an attempt to minimize toxicity, improve chemical stability, longer circulation periods, higher contrast, more regulated functionalization, and additional imaging methods. The paramagnetic NPs offer flexibility in size and shape, boost magnetic properties, and control over pharmacokinetics, potentially leading to an improvement in blood circulation time compared to conventional coordination complexes. These NPs are created either by integration into the nanostructured matrix or the post‐functionalization with the lanthanide coordination complex particles. The examples of nanoparticulate MRI contrast agents that have shown enhanced contrasting in various investigations are Gd‐doped silica NPs, Gd‐cerium NPs, Gd‐nanodiamond conjugates, Gd2O3 NPs; manganese (Mn) NPs like Mn3O4 NPs, Mn‐based double‐layered hydroxide NPs, MnO nanocomposites functionalized with porous AuNCs; dysprosium(Dy)‐modified NPs such as mesoporous silica NPs with Dy‐DOTA(1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) chelate in the outer pore channel, Dy2O3 and DyF3 NPs, Dy(OH)3 nanorods, etc. (Pellico et al. 2019).
NP‐based radiolabels are now being developed rapidly to allow researchers to carry out and monitor quantitative biodistribution studies on systemic administration, and to investigate the basic in vivo mechanism of NPs. They are hybrid structures consisting of an organic surface coating for colloidal stabilization and targeting functionality, the operative component i.e. imaging contrast as well as the adsorbed protein layer. However, since various marking techniques and radioisotopes are used to mark NPs in order to research their fate, it is important to ensure that radioisotopes are integrated into NPs with no effect on their initial biological behavior. Picomolar amounts of nano‐size radiolabeled gold nanoshells and polymeric NPs are investigated for positron emission tomography and single‐photon emission tomography (Koziorowski et al. 2017). The richness of fluorophores makes fluorescence imaging ideal for different applications. The emission of excitation probes in this procedure can be visualized by the human eye or by optical microscopy at higher resolution. Quantum dots, rare earth‐based nanophosphors, carbon dots, nanodiamonds, etc. are the fluorescent NPs researched as contrast labels for imaging (Pratiwi et al. 2019).
The potential of designed NPs that concurrently diagnose, administer, and even control therapeutic effectiveness has increased the hopes and aspirations of diagnostic nanomedicine. NPs have a high aspect ratio, can accommodate a high drug load and can be tuned to allow combination with drugs so that a targeted, imaging‐based diagnosis can be accompanied by simultaneous therapy unique to that condition known as theranostics. It is an interesting field of research, as many diverse variations of diagnostic and therapeutic methods can be incorporated into NPs. Diagnostic application of NPs to mark cancerous cells, distinctly tumor boundaries and minor metastatic areas, can be used to direct the surgeon in the eventual removal of the tumors surgically (McDonald et al. 2015). These diagnostic NPs may also be filled with post‐surgery therapeutic agents. Additional fascinating use of nano theranostics agents for tracking, and noninvasive in vivo imaging of transporter and drug, could allow for early evaluation of the treatment response. Carbon dots, quantum dots, Gd‐DOTA, AuNPs, magnetic iron oxide NPs, ferrimagnetic nanoclusters, and nanodiamonds have high in vivo stability and are materialized as valuable tools for amalgamated diagnostic imaging and therapy. Multicompartment capsules as nanomedicine vehicles composed of smaller nanocapsules or NPs assembled under bigger particles are also investigated as an efficient mode of theranostic delivery. However, after major advances in this field, therapeutic NPs are still at an early stage of growth (Sangtani et al. 2017).
Nanotechnology provides a potential for early identification of diseases and genetic make‐up with the assistance of modest, rapid, accessible, and affordable in vitro diagnostic testing of high sensitivity. In the near future, it is predicted to have instruments that are compact and decentralized, and that need only the smallest sample size for measurement and diagnosis. Such miniaturized lab‐on‐a‐chip technique is an inexpensive boon to patients and can be used in clinics and hospitals for preventing the spread of infectious diseases (Krukemeyer et al. 2015). The overall diagnostic process is improvised using NPs having the ability to detect molecules, cells, and tissues outside the human body. For instance, modified AuNPs in combination with ligand can directly bind to a complementary protein that induces controlled agglomeration owing to the cross‐linking of the NPs by the proteins. This can be identified colorimetrically by the change of color. These AuNP‐based diagnostic concepts are refined, for example in fast colorimetric DNA sensing, and are now used in the clinic for testing of patients’ samples (Khan et al. 2020). NPs encompassing organic and inorganic polymers are also applied as handy units for intracellular sensing purposes. The rationale behind using NPs in diagnostic applications is to identify the unique biological molecules in patients’ biological liquids allied to their health. They also offer sequential detection using quantum dot‐containing microbeads to produce barcodes with special optical emission. NP‐based chemical nose sensors are also gaining interest in sera sensing, cancer cell genotyping, and the distinction between cell surface‐based bacteria. Nanomedicine in diagnostics can generate a multiplexed platform that can exploit the ability of nanomaterials to easily detect minute changes in the cell surface that enable high‐throughput screening.
1.3.2 Drug Delivery
Nanotechnology offers various nanostructures/nanoformulations in the field of nanomedicine with exceptional physical, chemical, mechanical, electrical, magnetic, and biologic properties. Nanomaterials as a key component of nanomedicine extend many benefits due to their nanoscale properties as shown in Figure 1.1. Medical developments in cancer are among the most promising treatment methods in nanomedicine. So, the additional emphasis on cardiovascular, autoimmune, psychiatric, viral, and genetic and rare diseases is a positive development within the scientific community in nanomedicine. Another new field of high promise for nanomedicine is RNA‐based synthetic vaccines (De Jong and Borm 2008; Utreja et al. 2020).
In recent years, nanomedicines have been well known because nanostructures can be used as delivery agents by encapsulating or adding medicinal drugs and distributing them more specifically with a controlled release to target tissues. More than 50 nanoformulations have been approved by the FDA since 1995 and are currently on the market for a variety of indications. The commonly approved nanoformulations are liposomes, nanocrystals, iron colloids, protein‐based NPs, nanoemulsions, and metal oxide NPs. The recent acceptance of three primary nanomedicine drugs (e.g. Onpattro®, Vyxeos®, and Hensify®) by the FDA has demonstrated that the field of nanomedicine is specifically capable of developing products that transcend crucial obstacles in conventional medicine in a special manner (Martins et al. 2020). It also offers new drug‐free clinical effects through the use of pure physical modes of action within the cells, which thereby allows a difference in the lives of patients. In addition, new clinical applications are introduced commercially owing to nanomedicine formulations currently in clinical trials (above 400) unaided or jointly with foremost technologies including microfluidics, biotechnology, photonics, information and communication technology, advanced materials, biomaterials, smart systems, and robotics. Colloidal particles composed of macromolecular compounds in the 1–500 nm size range are NPs that are carriers in which either the active material is dissolved, encapsulated, or adsorbed into the matrix uniformly (Germain et al. 2020).
Figure 1.1 Nanoscale properties and allied benefits of nanomaterials in nanotherapy.
Liposomes are one of the most studied advanced nanoformulations, first described in 1965 for medical applications. They are biocompatible bilayered structures (single or multiple) of 50–500 nm size range composed of either or both synthetic and natural lipids that imitate cell membranes