Sustainable Nanotechnology - Группа авторов

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will reach a “limit to growth” prompted policy‐makers to urgently seek solutions for global sustainability, a concept that is so vast that it is subject to various interpretations. The vastness of the topic, however, still generates three aspects that global sustainability can affect. There is a global consensus that is agreed upon by the general public and the business community at large that environmental responsibility, economic efficiency, and social equity are necessary conditions for attaining global sustainability. Environmental responsibility, as the name suggests, is concerned with the conservation of resources – i.e. food, water, energy, etc. and safe methods of disposal of waste products of all forms. Likewise, economic efficiency focuses on resource production and meeting the demands of the market place. It is concerned with open trade and no inhibition in terms of the allocation of resources for production. Social equity, on the other hand, is concerned with the distribution of resources based on the productivity of an individual or an organization. In other words, social equity allows people to make decisions and ensures that the rewards that they get are based upon their efforts [1]. So, why address sustainability? Today, concerns for maintaining sustainability have increased, especially among the younger generation. Concerns about the availability of natural resources and the safe and efficient disposal of the by‐products of our production and consumption practices have added urgency to transitioning to a sustainable future. Consequently, finding solutions to these concerns have focused on using innovative science and technology applications. Therefore, applying nanotechnological research to maintain global sustainability has become a priority [2].

      Nanotechnology refers to understanding and control of the material at the nanoscale. For reference, a nanometer is one billionth of a meter. The field was introduced almost half a century ago and, over time, it has established itself as an active research area [3]. It incorporates nanoscale science, engineering, and technology – three very useful fields with various applications. At the nanoscale, materials show unusual biological, physical, and chemical properties. In fact, according to quantum theory, nanomaterials, with size being within the range of 1 and 250 nm, lie between the quantum effects of atoms, molecules, and the bulk properties of materials. This nanoscale is known as the “no‐man’s‐land” where their properties are controlled by the phenomenon that has its own critical dimensions. The structure of nanoparticles can be manipulated to produce materials with desired properties. Using nanomaterials with these unusual properties gives us an opportunity to enhance existing technology with profound features that have technical, economic, and societal implications [4]. Advocates of nanotechnology claim that the combinations of nanotechnology with various fields such as information technology, biotechnology, and cognitive sciences produce far‐reaching advances. In terms of global sustainability, nanotechnology’s influence in various areas can change the future of our efforts for sustainability [5].

      Medicine and nanotechnology, for the most part, go hand in hand. Whether it is the field of surgery or drug delivery, nanotechnological research has been very much involved in revolutionizing medicine. The growing interest in medical applications of nanotechnology has resulted in the emergence of the field popularly known as nanomedicine. Nanomedicine refers to applying nanoscale biotechnology to medicine. It allows us to use nanotechnology to improve the human biological system as well as create powerful tools for treating human diseases. In terms of sustainability, nanomedicine’s aim is to improve the overall quality of life by working at a molecular level to target diseases and formulate treatments [6].

      1.2.1 Nano Oncology

      Cancer is the result of uncontrolled cell division and has the tendency to spread to other regions of the body. Healthy cells can be converted to tumor cells with the right combination, or in this case, the wrong combination of genes and environmental factors. According to the statistics published by the Global Cancer Observatory (GLOBOCAN), in 2018, there were 18.1 million new cancer cases and 9.6 million cancer deaths, the leading cause being lung, bowel, prostate, and female breast cancer [7].

      Over the past several decades, nanotechnology has made magnificent contributions to oncology, not just in terms of diagnosis but also regarding drug delivery for treatment. Specifically, in cancer therapy, the use of nanomaterials has allowed the development of targeted drug delivery, enhanced the properties of therapeutic molecules, and developed a sustainable or stimulus‐triggered drug delivery [8]. There are a lot of factors involved in the effective management of cancer treatment, one of which is early detection. In order to detect uncontrolled growth, pathologists use cancer biomarkers. According to the US Food and Drug Administration (FDA), biomarkers are “any measurable diagnostic indicator that is used to assess the risk or presence of disease” [9]. Every cell type in the body has unique molecular features and characteristics.

      Cancer cells, or other cells in response to the presence of abnormal growth in the body, release biomolecules that are different from the biomolecules released from healthy cells. These biomolecules are defined as biomarkers and can be used to define the molecular definition of cancer [10]. Examples of biomarkers include genes; gene products; specific cells; enzymes; hormones present in blood, urine, tissues, and other bodily fluids; proteins or protein fragments; and DNA‐ or RNA‐based fragments [11, 12].

      There are several existing methods of detection available including:

      1 the Papanicolaou test to detect cervical cancer and mammography for breast cancer detection for women,

      2 prostate‐specific antigen (PSA) test for a blood sample of men to detect prostate cancer,

      3 occult blood test for colon cancer detection, and

      4 endoscopy, X‐rays, ultrasound imaging, CT scans, and MRI are used for various detection purposes.

      However, there are many limitations to the current methods. Furthermost, these methods are not always successful at detecting cancer at early stages. In addition, they are neither affordable nor available to many people who require them. The priority should be to discover new methods of detections that are accessible when needed. For detection, nanomaterials’ physical, optical, and electrical properties are quite useful. Over the years, the development of nanomaterials such as quantum dots, gold nanoparticles (GNPs), carbon nanotubes (CNTs), magnetic nanoparticles, gold nanowires, and many others works to lessen the limits of the standard methods of detection and increase the precision of detection [12].

      1.2.1.1 Gold Nanoparticles

      In comparison with other nanomaterials, the nanostructure of metallic nanoparticles is most flexible due to the synthetic control of their shape, size, structure, composition, assembly, and encapsulation, along with the tenability of their optical properties. Within these metals, GNPs are extremely useful in biomedical applications because their preparation time is shorter and the process is simpler than the others. Gold nanospheres can be prepared by reducing auric acid with different concentrations of sodium citrate for size variation. In addition, the citrate capping on the gold particles can be replaced with biomolecules such as DNA, peptides, and antibodies; they form covalent and noncovalent bonds with GNPs [13].

      With regard to treatment, photothermal therapy (PTT) using GNPs can initiate a hyperthermic physiological response in the tumor [16, 17]. The GNPs are able to convert light into heat, which can “melt”

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