properties make them suitable candidates for the various biomedical applications discussed previously. On the other hand, sometimes the same properties become responsible for causing harmful effects in human beings. However, while focusing on the significant advantages of nanomaterials, their toxicological aspects are overlooked.
1.4.1 Advantages of Nanomaterials
There are many studies have been performed and some of them are already discussed above which proposed the potential role of various nanomaterials such as liposomes, SLN, polymeric nanoparticles, etc. in specialized drug delivery, in the development of biocompatible nanomaterial prosthetic implants, the metal‐containing engineered nanoparticles, etc. for both the imaging and treatment of various diseases including cancers (Wright et al. 2016). Moreover, such nano‐scale size materials usually encapsulate therapeutic and/or imaging compounds, popularly known as nanomedicine, in nano‐size systems typically with sizes smaller than eukaryotic or prokaryotic cells. They offer immense opportunity in patient‐specific, targeted, and regenerative medicine technology with applications such as: regeneration of tissue cell therapy; regeneration of tissue with help of nano‐scale biomaterials; active or passive drug release; diagnostic tests; in vitro tests with sensors for determination of molecules that react with particular disease (biomarkers); in vivo measurements of biomarkers by imaging techniques using nanoparticles as contrast media; and more (Sharma et al. 2018).
Also, nanomaterials on chips, nanorobotics, and magnetic nanoparticles attached to specific antibodies, nano‐size empty virus capsids, and magnetic immunoassay are new dimensions of their use in drug delivery. The benefit of nano‐scale drug delivery systems, like nanotubes, nanocrystals, fullerenes, nanosphere, nanoparticles, nanoliposomes, dendrimers, nanopores, nanoshells, quantum dots, nanocapsule, nano vaccines, etc., is that they increase the efficacy and efficiency of the loaded drug by delivering a notable array of medications to almost any organ or specific site in the body (Mukherjee et al. 2014). As well, they minimize accumulation in healthy body sites to reduce toxic effects of the drug, as they can reach the specific site through active or passive means providing targeted, controlled, and sustained therapeutic effects. These unique characteristics lead them to generally inaccessible areas such as cancer cells, inflamed tissues, etc., and also provide an opportunity for the peroral route of administration of genes and proteins on account of weakening lymphatic drainage.
Formulation scientists can modify the structure of materials to extremely small scales leading to an increase in surface area relative to volume, and large surface area allows for increased functionalities of these multifunctional nanosized molecules, which consecutively promote selective targeting to the desired sub‐cellular targets, avoid destruction by macrophages, effect permeation through barriers, and deliver its components in a controlled way once it gets to the target cells and tissues. They also facilitate passive targeting of actives to the macrophages of the liver and spleen through direct delivery to reticuloendothelial cells and thus permitting a natural system for treating intracellular infections. Their suitability for enhancing the efficacy of drugs with short half‐lives is attributable to the long‐time spent in circulation and can be used to examine drugs as sustained‐release formulations as well as for delivering DNA (Mukherjee et al. 2014; Sharma et al. 2018).
There is no denying the fact that articulating drugs at the nano‐scale provides potential advantages with the possibility to modify properties like solubility, drug release profiles, diffusivity, bioavailability, and immunogenicity. The dissolution rate of the drug can be enhanced with an increase in the onset of therapeutic action as well as the reduction in dose and dose‐dependent side effects (Patra et al. 2018). Furthermore, an amalgamation of drug therapy and diagnosis, termed “theranostics,” at the nano‐scale has exceptional applications and can help diagnose the disease, affirm the location, identify the stage of the disease, and provide information about the treatment response.
1.4.2 Challenges Associated with the Use of Nanomaterials
The distinctive behavior of nano‐scale materials, as compared to conventional chemicals or biological agents, in biological systems is mainly expected due to their minute size. The minuscule size allows them to enter not only organs, tissues, and cells, but also cell organelles, e.g. mitochondria and nuclei, by crossing various barriers (Auría‐Soro et al. 2019; Tang et al. 2019). However, this may drastically modulate the structures of macromolecules, thereby impeding critical biological functions (Patel et al. 2015). They can also initiate blood coagulation pathways and stimulate platelet aggregation resulting in thrombosis. Various mechanisms as proposed by research scientists after evaluating in vivo toxicity of the nanomaterials is mainly through the generation of oxidative responses via the formation of free radicals and reactive oxygen species which may cause oxidative stress, inflammation, and damage to DNA, proteins, and membranes, ultimately leading to toxicity. The clearance of these materials by the reticuloendothelial system protects other tissues but engenders oxidative stress in organs such as liver and spleen (Badar et al. 2019).
Several toxicological studies have demonstrated that the toxic effect of nanomaterials is also regulated by their route of entry into the body, such as oral, skin, respiratory route, site of injection, and digestive canal, and further translocation and distribution according to the size determine additional toxic manifestations. The reduction in size leads to an increase in a number of surface atoms and as the surface area increases, it confronts dose‐dependent increments in oxidation and DNA‐damaging abilities. This also brings about an increase in surface energy further initiating binding of proteins that send a signal to macrophages and in turn engulfs the nanosized particles (Werner et al. 2018). Apart from this, certain unpredictable reactions can also take place inside the body due to unanticipated interactions and behavior of these particles. The research fraternities believe that the toxicity of nanomaterials strongly depends on their physical and chemical properties, such as the shape, size, electric charge, solubility, presence of functional groups, and chemical compositions of the core and shell. Reckoning with these facts of the toxicity and safety of nanosized materials presents a challenge in its clinical translation for drug delivery, diagnosis, and treatment of diseases (Gatoo et al. 2014). In recent years, when nanomaterials are becoming a part of daily life, toxicity concerns should not be ignored and accurate methods must be established to evaluate both the short‐term and long‐term toxicity analysis of nanosized drug delivery systems. Other significant hurdles faced are various biological challenges, fate and behavior in the environment, biocompatibility, safety, large‐scale manufacturing, intellectual property, government regulations, and cost‐effectiveness as compared to traditional therapy (Hua et al. 2018).
Although nanomaterials hold great promise in medicine, their production, use, and disposal lead to discharges into air, soil, and aquatic systems. It thus becomes imperative to assess the impact of such material with unknown toxicological properties on environmental health in addition to various pre‐processing procedures investigated before disposal. The vagueness associated with the risks of using nanomedicine in living beings cannot be ignored and they cannot be regarded as an ideal form of therapy. The science of using nanosized materials in the field of medicine has dynamically developed in recent times, but the ambiguity surrounding their characterization about safety and toxicity, and the lack of effective regulation with necessary closer cooperation between regulatory agencies, put forward the utmost challenge to evaluate their real impact in the healthcare system.
1.5 Conclusion
Nanotechnology is a novel and emerging technology having enormous applications in the whole biomedical sector, particularly in diagnosis, drug delivery, and treatment of a wide range of diseases such as infectious diseases, neurological disorders, cardiovascular diseases, cancers, etc. Therefore, considering the huge potential of nanotechnology in these fields it is believed that nanotechnology will play a crucial role in revolutionizing the current scenario of biomedicine (diagnostic and therapeutic strategies) and start a new era of nanomedicine. Nanomaterials have attracted huge attention in their use for diagnosis and management of
