Nano‐biotechnology in tumour and cancerous disease: A perspective review

Abstract In recent years, drug manufacturers and researchers have begun to consider the nanobiotechnology approach to improve the drug delivery system for tumour and cancer diseases. In this article, we review current strategies to improve tumour and cancer drug delivery, which mainly focuses on sustaining biocompatibility, biodistribution, and active targeting. The conventional therapy using cornerstone drugs such as fludarabine, cisplatin etoposide, and paclitaxel has its own challenges especially not being able to discriminate between tumour versus normal cells which eventually led to toxicity and side effects in the patients. In contrast to the conventional approach, nanoparticle‐based drug delivery provides target‐specific delivery and controlled release of the drug, which provides a better therapeutic window for treatment options by focusing on the eradication of diseased cells via active targeting and sparing normal cells via passive targeting. Additionally, treatment of tumours associated with the brain is hampered by the impermeability of the blood–brain barriers to the drugs, which eventually led to poor survival in the patients. Nanoparticle‐based therapy offers superior delivery of drugs to the target by breaching the blood–brain barriers. Herein, we provide an overview of the properties of nanoparticles that are crucial for nanotechnology applications. We address the potential future applications of nanobiotechnology targeting specific or desired areas. In particular, the use of nanomaterials, biostructures, and drug delivery methods for the targeted treatment of tumours and cancer are explored.


| INTRODUC TI ON
Despite the terms development and research were not yet very common, the American physicist Feynman pointed out the possibility of working at the nanoscale, and even at the smaller scale when he pronounced his famous conference "There is plenty of room at the bottom" in 1959. The inclusion of chemical, biological, and physical properties in the study of small particles, ranging from nanometres such as proteins, DNA, viruses to micrometeres, led to the concept of nanobiotechnology. Nanotechnology is a highly interdisciplinary field that combines biology and physics to produce multifunctional systems and devices that are more sensitive, specialized, and functional. [1][2][3] Surfaces and interfaces play a crucial role in the development of novel nanomaterials. As particles get smaller, the number of atoms on their surface grows in comparison to the number of atoms inside their volume. This means that nanoparticles can be more reactive, leading, for example, to the production of catalysts or fillers that are more effective in composites. Because of their increased surface energy, nanoparticles can interact and adhere to each other. If the building blocks of nanomaterials are synthesized so that parts of the surface are sticky whilst other parts are passive and nonsticky, then random Brownian motion in a liquid can cause the blocks to adhere to each other in predetermined patterns and form larger structures. 4 This is the basic idea behind the so-called "bottom-up" methods of self-organization.
Amorphous structures differ from crystalline structures in the absence of long-range atomic order and rotational and translational symmetry. Researchers have used nanocomposite materials to deliver drugs or genes to patients in the form of specific drugs to extend the half-life of the drug. The biocompatibility of the nanomaterial can be improved by folding in the amorphous side of the nanomaterial, which is transported to the appropriate site to treat the disease. 3 The liver, spleen and bone marrow are able to filter out nanoparticles larger than 200 nm efficiently; however, the particle size range of 10-200 nm is suitable for the circulation of spherical carriers. 5,6 Nanoparticles smaller than 10 nm can easily pass through the kidneys and enter the bloodstream by extravasation. 7 The relationship between the size and shape of nanoparticles is closely related to their beneficial properties.
Nanoparticles with large spherical shapes improve the flexibility of the required scaffold formed with drugs for treating specific diseases. A lot of credit goes to the advances in nanofabrication techniques, many nanoparticles with different physical, geometric and chemical properties have been produced in recent years. 8 The significance of nanobiotechnology in human life has been shown in Figure 1.
Nanobiotechnology can act as a shield for various biomedical applications, as shown in Figure 2, which in turn is very useful for the living organism against diseases such as tumours or cancer. 9 The use of various bio-nanoparticles and nanomaterial's for drug delivery at the site of action under controlled application of desired drugs can be used for the treatment of numerous diseases or syndromes. The biocompatibility and bio-adaptability of the nanomaterial's used are extremely important, and they pave the way for more precise medical research using nanotechnology and biotechnology. 10,11 In this review article, we provide a general overview of the aspects of nanoparticles that act as an essential component of nanotechnology. We discuss future aspects of nanobiotechnology to target desired or specific sites, in particular, the use of nanomaterials, biostructures, and drug delivery mechanisms for targeting tumours.

| NANOPARTICLE S -E SS ENTIAL COMP ONENTOFNANOTECHNOLOGY
Nanotechnology enables the development and use of structures and devices with organizational features ranging from single molecules to about 100 nm in size, a scale at which unique capabilities emerge compared to bulk materials. This refers to the ability to create yet another kind of nanostructures and devices capable of performing specific activities at the atomic and molecular levels. Nanotechnology is often considered the most promising emerging technology of the 21st century because it combines chemistry, biology, physics, materials science and engineering at the nanoscale. Other areas fighting for this distinction include biotechnology and information technology. [12][13][14] In virtually all of these technologies, the strategy of combining different domains to formulate new materials involves the control of matter at the nanoscale. Nanoparticle fabrication is a critical component of nanotechnology science. Nanoparticles are specifically produced in the form of nanocrystals or nanosheets and are most often used to create nanostructured materials. The assembly of precursor particles and associated structures also plays a crucial role. 15,16 Scientific, Technical Research and Innovation 2021-2023 from the Spanish Ministry of Science and Innovation, Grant/Award Number: ProjectPLEC2022-009507 of nanobiotechnology targeting specific or desired areas. In particular, the use of nanomaterials, biostructures, and drug delivery methods for the targeted treatment of tumours and cancer are explored.

K E Y W O R D S
dendrimers, drug delivery, gold nanoparticles, nano-biotechnology, silver nanoparticles, tumour

| Whynanoparticles?
In the production of nanoparticles, crystals, and nanosheets, three types of properties are sought that offer different advantages: a. Size scaling, such as size confinement of certain flow structures, particle interfaces, and crystallizations, offers new physical, chemical, or biological properties. To distinguish smaller particles from larger interfaces, researchers have studied properties based on optical, electronic or quantum electromagnetic interactions. 17,18 b. The magnetic and optoelectronic properties of the fabricated nanomaterials. The particle size and the incorporation of various artificial substances into the cells can be monitored, for example, on the basis of the colour changes in the suspensions. 19,20 c. The molecular, atomic and microstructural structures. For example, various methods can be used to generate materials, including chemical self-assembly, nanofabrication (3-D structural manipulation), chemical generation of surface nanostructures, 3-D molecular folding, bio-templating, and various revolutionary approaches. 21,22 3 | NANOMATERIAL S The physical and chemical properties of nanomaterials are determined by their particular composition, shape and size. The effects of nanomaterials on health and the environment also depend on their size, shape, etc. It is difficult to find a single, universally accepted definition of nanoparticles, and the scientific community is currently F I G U R E 1 Representation of the significance and requirement of nanobiotechnology in different field related to human life. As an interdisciplinary field of science, nanobiotechnology holds potential to develop improved drug delivery, formulation and packaging systems.

F I G U R E 2
Diagram showing the involvement of nanotechnology along with biotechnology. The application of the amalgamation of nanotechnology and biotechnology is widespread as it involves other field's involvement such as structural and genetic engineering as well. The applications of nanotechnology are enormous in making nano biosensors, in target-specific delivery of drugs and even in tumour/disease-specific identification of targets as well.
debating a strict definition of nanomaterials. According to the EU Commission's definition, a nanomaterial is "a man-made or natural material containing unbound, aggregated or agglomerated particles with an external diameter between 1 and 100 nm". There are four types of nanomaterials: (1) carbon-based nanomaterials, (2) organicbased nanomaterials, (3) composite-based nanomaterials and (4) inorganic-based nanomaterials. Inorganic-based nanomaterials include various metal and metal oxide nanomaterials. 23 The synthesis of inorganic nanomaterials such as metals and metal oxides using the "green synthesis technique" has gained popularity due to its sustainability, reliability, low cost, simple procedure, large-scale production and harmlessness. In this method, inorganic nanomaterials can be produced by using a plant or plant extract as a reducing agent to reduce the metal precursor to its elemental form at the nanoscale. 24 31 Examples of organic nanomaterials that do not contain carbon include dendrimers, cyclodextrin, liposomes, and micelles. 32 Composite nanomaterials consist of any combination of metalbased, metal oxide-based, carbon-based, and/or organic-based nanomaterials. These nanomaterials have complicated structures, such as a metal-organic framework.
In the top-down method, the materials are crushed by milling or grinding ( Figure 1). This method is not suitable for the synthesis of symmetrically structured nanomaterials because the generation of microscopic particles requires a lot of energy. The fundamental disadvantage of this method is that the surface structure is not perfect, which directly affects the physical and surface properties of the materials produced. This strategy involves a variety of physical processes, including pyrolysis, atomization, electrospinning, laser ablation, sputtering, lithography, radiation-induced chemical etching, and lithography. 33,34 Nanomaterials can be synthesized by bottom-up and top-down techniques, depending on the chemical and physical properties of the nanomaterials. Different size-volume ratios can be achieved to perform desired functions with variable morphological properties. 35,36 In the bottom-up technique, materials are synthesized atom by atom, cluster by cluster, or molecule by molecule. As a result of atom-by-atom deposition, nanoscale materials or nanomaterials are formed (see Figure 1). This strategy provides homogeneous morphology, size, shape, and distribution, making it more advantageous than the previous strategy. Bottom-up approaches for nanomaterials fabrication include hydrothermal, solvothermal, chemical vapour deposition, chemical reduction, template-assisted, sol-gel, organic ligand-assisted, biological, and polyol techniques. 37,38 The various materials produced by nanotechnology are the results of colloidal science and interfacial science and contain nanorods, fullerenes, graphene, carbon nanotubes and various other nanoparticles.
Fullerene is a family of nanomaterials with a size of 1/10 or even less in one of the three dimensions. 39

| Carbon-basednanomaterials
Carbon has a variety of forms, including allotropes, which are structures with different dimensions. The bonds of carbon vary from sp3 of diamond, with a cubic face structure, to sp2 of graphite, with a hexagonal structure and fullerenes. In addition, the states of carbon vary depending on whether the carbon is amorphous or crystalline. This directly indicates whether or not the thermal, mechanical, and electrical performance of carbon lattice structures improves. 40,41 Diamond, for example, has a face-centred cubic structure with a bond length of 1.54 Å and a lattice constant of 3.54 Å. Due to its extremely rigid lattice structure, diamond has the highest weight fraction and thermal conductivity of all bulk materials. 42 The highly stable form of carbon is graphene, which is thermodynamically stable under standard conditions. Graphene consists of a layered, planar organization with a hexagonal structure arranged in a honeycomb lattice with a bond length of 1.42 Å. 43 Fullerene is the smallest arrangement consisting of hexagonal and pentagonal rings known as Buckminsterfullerene. It was discovered in 1985 after the name of Buckminsterfullerene. These buckminsterfullerene molecules are used in a variety of studies and fields, such as drug delivery, solar cells, contrast agents for X-ray imaging, superconductors, etc. One of the advantages is that it can be made in different shapes and sizes, varying from 30 to 3000 atoms of carbon. 44,45

| Organic-basednanomaterials
Nanoparticles possess all three dimensions but have properties that differ from those of bulk substances. The use of nanocarriers can be directly applied in biomedicine and as scaffolds for targeted drug delivery. Nanostructures have numerous applications and advantages, including surface reactivity, colloidal stability, and dispersion. The important functions of nanoparticles include active drug delivery and controlled release; nanoparticles are used together with tiny drugs, DNA and proteins to actively treat various diseases.
According to the FDA and EMA (European Medicines Agency), biocompatible nanomaterials made of silk fibroin and chitosan are used in various biological applications. 46,47 Fibres with a diameter on the nanometre scale are called nanofibers. In the textile industry, this category is often expanded to include microfibers, which are fibres with a diameter of 1000 nm or less. In general, there are several ways to produce fibres, including melting, interfacial polymerization, electrospinning, antisolventinduced polymer precipitation, and electrostatic spinning. Carbon nanofibers, on the other hand, are fibres that have been graphitized by catalytic synthesis. 48 The diameters of nanofibers depend on the type of polymer and the manufacturing technique. Compared to microfibers, all polymer nanofibers are characterized by their large surface-to-volume ratio, high porosity, high mechanical strength, and flexibility in functionalization. Nanofibers have found significant utility as scaffolds for biodegradable polymers in tissue engineering. 49

| Composite-basednanomaterials
Various materials, such as composite nanoparticles, have emerged as a result of technological and scientific innovations. Optical sensors, specific catalysts, metal-semiconductor junctions, and packaging through film modification are some of the applications of these nanoparticles. For example, anatase titanium dioxide nanoparticles can be synthesized using a new sol-gel process and then analysed using a variety of methods. 50 The main advantage of using egg white proteins as gelling agents is that they provide long-term stability to the nanoparticles by preventing aggregation of the particles. 51 It has been reported that the egg white solution is reliable, whilst the green gelling agent is inexpensive, and that this matrix can be useful in the sol-gel process for the synthesis of small-size nanoparticles. 51,52

| Inorganic-basednanomaterials
An inorganic nanomaterial (NM) may be composed of a metal or a non-metal element and may take the form of an oxide, hydroxide, chalcogenide or phosphate molecule. Applications of these materials in modern society include electronics, photonics, chemical sensors and biosensors, and biomedical devices. For example, quantum dots, polystyrene, magnetic, ceramic and metallic nanoparticles that have a central core of inorganic materials and exhibit fluorescent, magnetic, electrical, and optical properties. 53,54 The term "quantum dots" refers to man-made, nanoscale semiconducting crystals capable of transporting electrons. UV light causes them to emit coloured light. Microwave-assisted colloidal synthesis is one method that can be used to produce these compounds. Their applications include photovoltaic cells, biological applications, LED displays, photodetectors, and photocatalysts. 55 4 | ME TALINORG ANICNANOPARTICLE S Nanoparticles (NPs) of metals such as silver, gold, and platinum are usually very small (less than 50 nm) and have a large exposed surface area. Because of their small size, they are able to penetrate the capillaries of tissues and cells. Because they have a large surface area and their chemistry can be altered (tunable surface chemistry), they can accommodate a variety of drugs. 56 Metallic nanoparticles have been used for the controlled release of drugs in the treatment of cancer. 57,58 The surface properties of NPs also affect the duration of blood circulation. After administration, NPs can bind to serum proteins known as opsonins. These include immunoglobulins and complement proteins that help macrophages recognize NPs.
Thus, opsonization is a critical factor in whether NPs remain in the bloodstream or are phagocytosed by macrophages. Therefore, altering their surface is an effective technique to increase or decrease their retention time in the blood. 59 Despite the goal that these metals should remain inert, bioaccumulation and toxicity may occur. 60 Metallic NPs can be synthesized and provided with a variety of chemical functional groups so that they can be coupled with antibodies, ligands, and desired drugs. 61 This results in a wide range of potential biotechnological applications, including magnetic separation, pre-concentration of target analytes, delivery of target drugs, and carriers for gene therapy. 62 One of the major advantages of metal NPs is their ability to absorb light energy and convert it efficiently into heat. Therefore, some of them can be used in hyperthermic tumour therapy, in which thermal energy is generated by light stimulation to improve the specificity of this therapy. 58 Understanding the physical and chemical properties of inorganic nanoparticles is a critical component for their use. Characterization of inorganic nanomaterials is performed using a variety of methods and instruments, including UV-Vis spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), scanning electron microscope (SEM), high-resolution transmission microscope (HRTEM) and transmission electron microscope (TEM). Powder X-ray diffraction (PXRD) is used to identify the crystalline phase and crystal structure. The fraction of elements present is determined by energy dispersive spectroscopy (EDS). The particle size can be determined by X-ray powder diffraction (PXRD) and dynamic light scattering (DLS).
X-ray photoelectron spectroscopy, often referred to as XPS, can be used to determine the oxidation state of the elements present and their elemental composition. The surface area of nanoparticles can be determined using the Brunauer-Emmett-Teller method (BET). 63 In addition, various imaging techniques such as MRI, computed tomography, positron emission tomography, ULTS, surface-enhanced Raman spectroscopy, and optical imaging have been developed to detect a variety of diseases, including cancer. 64,65 In recent years, oncology has paid much attention to inorganic nanoparticles (INPs) because of their enormous potential for drug delivery, gene therapy, photodynamic treatment (PDT), photothermal therapy (PTT), bioimaging, motion control and so on. [66][67][68] Recently, attempts have been made to modify naked INPs to overcome their natural limitations, such as rapid elimination by the immune system, low accumulation at tumour sites and significant toxicity to the organism. 69  Although the results of many CCM-INPs systems are promising, there are still some obstacles to overcome before these technologies can be commercialized. People may have concerns about injecting cancer cell-derived compounds into their bodies. This is especially true for people who are at risk for certain cancers and could use this technique as a preventive vaccine. As long as there is a hope of eliminating even a single malignancy through therapy or vaccination, many different research strategies will remain active towards CCM-INPs. 70 The INPs can overcome the limitations of platelets in tumour treatment by stably taking over the functions of platelets, such as immunological evasion and aggregation of inflammatory foci. The encapsulation of platelet-derived membranes (PLTMs) has the advantage that they can be delivered directly to the site of inflammation or tumour growth, unlike the membranes of red blood cells. Researchers have taken advantage of this property to deliver drugs and INPs to the tumour site. NPs encapsulated in platelets use both passive and active targeting mechanisms to exert their therapeutic effects. 74,75 Platelet membrane-camouflaged NPs (PNPs) use autologous antigens produced by PLTM, such as CD47, on their surface ligands to bypass clearance by the immune system and deliver more drugs to sites of inflammation. 76

| Goldnanoparticles
Most nanoparticle-based carriers are theoretically tagged with probes for tumour targeting. This is done with the goal of increasing the therapeutic efficacy of anticancer drugs whilst improving their targeting of the tumor. 83 Gold nanoparticles (GNPs) range in size from 2 to 100 nm, with particles 20-50 nm in size having the highest cellular absorptive capacity. 40-50 nm-sized particles have been shown to have specific cytotoxicity. GNPs are characterized by the fact that they promote drug efficacy, can be loaded with drugs, are biocompatible and can easily reach the target site with the bloodstream, are not cytotoxic to normal cells, and can be produced by various methods. 84 Due to the advantages of functionalized GNPs, their use has expanded and they could be used in a variety of applications, from the manufacturing of photonic devices to the detection of organic and biomolecules to charge storage systems. 85 There are numerous types of GNPs, including gold nanorods, gold nanocages and gold nanospheres. 86 Previous research has suggested that the ideal size of nanocarriers for tumour targeting should be between 10 nm and 200 nm, with surface-modified caution charges. 84 These nanoscale carriers would be immediately removed from the reticuloendothelial system if there were no positively or negatively charged changes on the envelope surface. 86 Therefore, the decoration of the surface of a nanocarrier with polyethylene glycol is the most commonly used surface coating agent to prevent and reduce clearance mediated by the reticuloendothelial system (PEG). 83 GNPs can serve as contrast agents and dose enhancers in image-guided nanoparticle-enhanced radiotherapy using kilovoltage cone-beam computed tomography for biomedical and cancer therapy applications. 84 Since N-oxyamide-modified molecules are metabolically stable, coating GNPs with an N-oxyamide-linked glycoglycerolipid improves drug delivery to target tissues. 87 Recently, researchers coated gold nanorods with a modified low molecular weight hyaluronic acid coupled with pH-sensitive groups. The generated gold nanorods accumulated accumulate in tumour areas with acidic environments. 88,89 To increase the specificity of drug delivery, certain antibodies can be applied to the surface of GNPs. Cellular absorption of GNPs can be enhanced by coating them with hydrophilic polymers such as mercapto-undecanesulfonate (MUS) or both MUS and octanethiol. 90

Jia et al synthesized 'bio-friendly virus'-like GNPs by scattering
GNPs on the surface of polymeric substances, thereby changing the shape of the GNP complex to a virus-like form and thereby increasing its uptake by human cervical cancer cells (HeLa), monkey renal fibroblast cells (COS7), human hepatoma cells (HepG2), and mouse fibroblasts (3T3). 91 By incorporating molecules into the monolayer, such as antibodies (and their fragments), lectins, proteins, hormones or charged molecules, the nanoparticles can be targeted at the cell, tissue or organ level. Using an ultrasensitive electrochemical cytosensing platform, Zhang et al. produced GNP-coated carbon nanospheres with an antibody for the carcinoembryonic antigen to diagnose non-small cell lung cancer (NSCLC). In A549 lung cancer cells, the GNP complex showed no toxicity. This in vitro study provides evidence that the GNPs used may be able to detect NSCLC at an early stage. 92,93 Researchers have shown that they can identify and image cancer cells by conjugating anti-EGFR to the surface of gold nanoparticles.
The work by Patra et al showed that a multifunctional GNP labelled with C225 and gemcitabine, a drug commonly used in clinics to treat various cancers, can be effective. 94 The proliferation of pancreatic cancer cells was slowed down with this treatment thanks to the GNPs. 95 This approach has the potential to be used as a therapeutic cancer treatment against tumours in which EGFR is overexpressed. This highly vascularized area is notoriously leaky, creating a situation of increased permeability and retention. The hyperpermeability of solid tumours is exploited to develop nanoparticles for passive uptake. 99 The angiogenic blood channels of this tissue may contain 600 nm gaps between endothelial cells through which carriers can extravasate. This results in a concentration of carrier at the tumour that is up to ten times higher than that of the same amount of free drug administered intravenously. 100 It has been shown that intravenous injection of GNPs containing tumour necrosis factor (TNF) results in TNF being transported to a tumour in the colon in vivo. 101 TNF bound to nanoparticles was less dangerous and more effective than native TNF. 102 Surface plasmon resonance gives gold nanoparticles their optical properties. These properties can be used to treat diseased tissue with photodynamic therapy (PDT). 103 showed that 95% of CD8-expressing lymphocytes were destroyed after treatment with GNPs and immunoglobulin (IgG). 106 Using GNPs labelled with prostate cancer-specific bombesin peptide analogues that generate beta radiation, it is possible to achieve a higher therapeutic dose. This design could potentially also be used for breast and small cell lung cancer cells, as the peptide analogue has a strong affinity for cell surface receptors. 107 An important property of gold nanoparticles is that they do not oxidize or degrade in living organisms. These desirable properties are critical for the development of nanomaterials as drugs and diagnostics in the medical field. Radioactive GA -198 gold nanoparticles were administered to SCID mice in a single dose. After 3 weeks, researchers observed a remarkable 82% reduction in tumour size between the treatment and control groups. The high tolerability of  GNPs was also demonstrated by the fact that only 2% of the radioactivity reached non-target organs and that blood levels returned to normal in the treatment group. 108 When injected subcutaneously, intramuscularly, or topically, nanoparticles used as drug carriers usually have a longer residence time, typically in local lymph nodes, than the free drug. The biological distribution of nanoparticles strongly depends on the hydrodynamic radius and surface charge of the nanoparticles. Gold nanoparticles with a size of 10 nm were found in many organs, whilst those with a size of 15 nm or 50 nm were able to cross the blood-brain barrier. Citrate-capped gold nanoparticles with a size of 15 nm had the highest penetration coefficient. The 100 nm and 200 nm particles remained on the surface of the skin, whilst the smaller particles were able to penetrate deeper into the dermis and subdermis of the skin. 109 Understanding the basic mechanisms of interactions between nanoparticles and cells is critical for the application of nanotechnology in cancer therapies, screening, and diagnostics.

| Synthesis of GNPs
GNPs can be produced using numerous technologies, including chemical and physical methods that encompass various physical and chemical methods, including the template approach, sonolysis, electrochemical method, green biosynthesis method, solvent-free photochemical method, γ-irradiation method, and hot injection technique. 110,111 In most cases, the preparation of gold nanoparticles involves the use of reducing agents in conjunction with the chemical reduction of chloroauric acid (HAuCl 4 ). 112 Figure 3 shows the stages for the synthesis of GNPs. (a) Beginning of the process as a bottomup method, leading to the (b) nucleation phase, i.e., the formation of a new phase or structure by self-assembly methods, leading to the (c) growth phase, where surface development occurs, leading to the (d) synthesis of GNPs.

| Silvernanoparticles(SNPs)
Before the development of nanotechnology, silver was thought to be just a metal. Later, it was found that it could be produced on a nanoscale. Modern engineering techniques for metallic silver resulted in ultrafine particles with distinct shapes and properties in the nanometre (nm) range. In the medical field, SNPs are used for their antifungal, antibacterial, anti-inflammatory, antiviral, and osteoinductive properties. They can be synthesized by a variety of techniques, have optical properties, and accelerate the wound-healing process. SNPs have great potential for cancer treatment. Several types of human cancer cells, including breast cancer cells, have been tested for the anti-cancer effects of SNPs. 113,114 In recent times, some scientific studies have focused on the use of SNPs in combination with anticancer drugs to enhance antineoplastic efficacy, especially when used synergistically with the natural anticancer drugs used in their preparation. 114 The chemical approaches are based on the chemical reduction of Ag+ ions by agents such as sodium borohydride, sodium citrate, sodium ascorbate, N,N-dimethylformamide, and polymers, to name a few. The reducing agent produces metallic silver (Ag0) that aggregates into oligomeric aggregates. Colloidal metallic silver

F I G U R E 3
Steps showing the synthesis of gold nanoparticles (Au = Gold). (1) Bottom-up approach or self-assembly use forces like physical or chemical one at nanoscale to muster small units into larger one in case of the gold atoms and/ or clusters, leading to the (2) nucleation phase to form a new structure by selfassembly, leading to the (3) growth phase, where surface development occurs, leading to the (4) synthesis of GNPs.
particles are formed in this manner. Chitosan, cellulose, and other polymers (polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and polymethacrylic acid (PMAA)) can be used as capping agents and surfactants as stabilizers to prevent the SNPs from aggregating to an undesirable size. 115 Most plant extracts are used to synthesize SNPs offering therapeutic properties (anti-inflammatory, anti-cancer, etc.) that can be used in conjunction with the biological activity of SNPs. Some researchers have also suggested green-synthesized SNPs as an antiangiogenic agent. 116 The anti-cancer activity of green-synthesized SNPs is enhanced by the production of phytochemicals in response to the acidic environment of malignant cells. 117 Excessive release of silver ions is observed at acidic pH. Selective death of cancer cells at acidic pH has been demonstrated by incubating SNPs in buffers at pH 5 and pH 7.4. Silver ions are also affected by how normal cells and cancer cells interact electrostatically. Extensive electrostatic interactions between normal and cancer cells are also required for the selective destruction of cancer cells. Another mechanism that has been described for the anticancer potential of SNPs is autophagyinduced cell degradation leading to cell death. Autophagy is stimulated by green-synthesized SNPs because the number of autophagolysosomes is increased, leading to the self-destruction of cancer cells. 117,118 There are numerous methods for the conjugation of anticancer drugs with SNPs, including encapsulation, entrapment, and attachment to the surface of nanoparticles. For example, the incorporation of SNPs into the structure of liposomes improves stability, biocompatibility, and toxicity. 119 Rozalen et al. 120  and MTX, which has pharmacological activity against cancer. 121 The anticancer drugs alendronate and doxorubicin were identified for coupling to SNPs 115 and showed a significant synergistic effect against the HeLa cell line. Given the similarities between epirubicin and doxorubicin, it is reasonable to assume that the drug molecules formed coordinated covalent bonds with the SNPs. The synthesis of SNPs associated with doxorubicin. had a lower toxic effect on non-cancer cells. 115 SNPs modified with polyethylenimine (PEI) and functionalized with paclitaxel (PTX) reduced the growth of HepG2 cells and showed minimal cytotoxicity towards LO2 cells. 122 SNPs were also used as nanocarriers for the anticancer drug gemcitabine. Cytotoxicity tests using silver and gold nanoparticles on breast cancer cell lines MDA-MB-453 showed that SNPs did not cause significant cytotoxicity in the breast cancer cell line. 123 In the coming years, this area of research is expected to expand with a broader range of anticancer drugs and deeper information on the in vivo absorption, distribution, metabolism, excretion and toxicity of the silver nanosystems. 124

| Synthesis of SNPs
Chemical, physical and biological methods have been used to produce silver nanoparticles. 125 The common procedure for the preparation of silver nanoparticles is shown in Figure 4. The nanoparticle solution is prepared by adding sodium citrate and sodium borohydride solution, heated for 30 min and then centrifuged for 30 min to separate the solution mixture into pellet and supernatant, discarding the supernatant. The pellet is then dispersed in an aqueous solution to form the silver. The chemical and physical methods used to prepare SNPs are listed in Table 1.

| Polymericnanoparticles
Nanoparticles in their polymeric form must be absorbed by the body's circulatory system before they reach their target in the body, which may be malignant or healthy tissue. The mobility of nanoparticles is often influenced by their surface properties and dimensions.
Often, the mononuclear phagocyte system (MPS) absorbs most of the injected nanomaterials, preventing them from reaching the disease target sites. In this case, this shortcoming is exploited by administering nano-antioxidants that are preferentially absorbed by the liver to avert hepatic ischemia-reperfusion injury (IRI), a disease caused by reactive oxygen species (ROS). 128 To prevent macrophages from ingesting the nanoparticles, a coating of polymers-including hydrophilic polymers-is applied to the surface of the particles. To prevent the nanoparticles from being degraded by enzymes, the biocompatibility of the particles can be increased by making them more water-soluble and less susceptible to enzymes. 129 126 In water, they form vesicles in which anticancer drugs can dissolve and remain stable once loaded into their structure. They can encapsulate both hydrophobic and hydrophilic substances. In addition to phospholipids, other substances such as cholesterol can be added to their formulations, which decreases the fluidity of the nanoparticles and increases the permeability of the hydrophobic drugs through the bilayer membrane, which improves the stability of these nanoparticles in the blood. 134 Several researches have been conducted to make these types of anticancer drugs more suitable and tolerable for active targeted treatment.
For example, liposomal formulations have been shown to improve the pharmacokinetics and pharmacodynamics of related drugs, such as doxorubicin. 135 There are a few different methods by which liposomes can be successfully produced. These methods include the use of mechanical processes, the use of organic solvents, and the elimination of detergents from phospholipid/detergent-micellar

F I G U R E 4
Step-wise flowchart showing the synthesis of silver nanoparticles. The nanoparticle solution is prepared by adding sodium citrate and sodium borohydride, heated for 30 min, and then centrifuged for 30 min to separate the solution mixture into pellet and supernatant. The supernatant is discarded, whereas the pellet is dispersed in an aqueous solution to form the silver nanoparticles (SNPs).

Chemical methods Physical methods Bio-based methods
Tollens method 241 Arc-discharge method 242 From bacteria, fungi, yeast, algae and plant 125 This paper highlights the gaps and limitations in nanotechnology for the precise study and analysis of nanotechnology domains. 247 2

Materials for endodontic regeneration
Teeth Aesthetic Materials Dendrimers and dendritic copolymers Dendrimers Nanocomposites Whilst studying the nano-dentistry, a nanostructured material used is sapphire, which is a type of composite material that increases durability and appearances. Sapphire is also used for the replacement of the upper enamel layer by artificial materials due to the material property which shows the property as 200-300 hardness than the ceramic.
The most suitable method for treatment as aesthetic dentistry procedure, dentition re-naturalization is the most popular procedure in the dental practice.
The involvement of nanotechnology in the dentistry gives rise to new ideas for the oral health care remedies by preventing the cause rather than restoration or prevention. 248 3 Organic dendrimers Hollow polymer capsules Nano-shells Drug delivery is one of the potential applications against the application towards the treatment and remedy of several illnesses. Several diseases do not have cure nowadays but found the cure with help of nanotechnology and its future study will lead the potential benefit in medicine.
The nano-formulations provide protection against several disease-causing organisms by denaturation and degradation when exposed under extreme pH. It also increases half-life of the drug due to its retention ability and only targeted release of drug at specific site. The mechanical, optical, and rheological properties of cellulose nanocrystals are described, as well as their chemical structure, sources, chemical and physical separation processes.
To attain higher productivity and quality, the new industrial extraction procedures for obtaining cellulose nanocrystals in large quantities must be optimized.

251
(Continues) A systematic programme is necessary to expose the relationships between experimental parameters (method, model, doses) and particle parameters (shape, size and with different molecular probes).  Hydrogel, dendrimer and DNA nanoflower are three new but potential cancer theragnostic concepts. Individual formats' utility and promise in biomedical science, particularly in cancer therapy, will be examined.
The ability to easily assemble DNA structures into well-defined designs susceptible of traversing physiological barriers and remaining stable in biological fluids inside the body, as well as the possibility for bio-sensing and nanoscale precision tasks on target cells. If effective, it could provide a never-beforeseen potential for early cancer identification and treatment at the level of a single cell. 255 11

Liposomes
Polymeric nanoparticles Nanorods The most commonly explored nanotechnologies in this field are polymeric nanoparticles, gold nanoshells and liposomes with chemotherapy and PDT/PTT being the most widely used therapeutic methods. The many types of nanotechnology employed in the treatment of oral cancer, as well as a summary of nanodrug administration routes.
Furthermore, because most researches are performed in animal models, overall safety of nanotechnologybased medication delivery systems is uncertain. 256 12 Nanoparticles Nanocarriers Apoptosis-induced gene therapy Vector stability and transfection efficiency have been improved (SK-BR3) and growth has decreased (MCF-7). The method of nanoparticle-targeted drug delivery, as well as recent advancements in nanoparticlebased carriers for microRNA, gene augmentation therapy and small interfering RNA in breast cancer.
However, despite ethical and safety problems, nanodevices remain a promising tool to fight over illness.

TA B L E 2 (Continued)
combinations. The final liposome structure is influenced by the preparation method, the amount and type of phospholipid used, the ionic and charge properties of the aqueous medium, and the duration of hydration of the lipids. 136 There are two general approaches to nanocarrier vectorization. 137 One is passive targeting, in which liposomes enter tumour cells exclusively through the cell membrane.
The other is active targeting, in which liposomes are used together with antibodies that can find tumour cells altered in their structure.
Third, stimulus-sensitive liposomes can be used. Using an external trigger, parameters such as temperature, pH or magnetic fields can be changed to control the release of an anticancer drug. 138 To increase the stability of the anticancer drug docetaxel, lipo- Encapsulation of Doxorubicin (DOX) in a liposome has been shown to increase release and efficacy in vivo whilst reducing citoxicity in vitro. 143 DOX has also been encapsulated with curcumin (CUR) in a liposome designed for a long circulation time. 144 146,147 The incorporation of active anticancer drugs into SLN formulations has been extensively explored because SLNs have the potential to increase oral drug bioavailability, preserve labile anticancer drugs, and reduce the dose without compromising efficacy. 147,148 For example, niclosamide-loaded SLNs were developed to increased cell uptake and anticancer activity against triplenegative breast cancer (TNBC) cells. 149 Talazoparib loaded on SLNs was also developed, which increased the therapeutic index of the drug against TNBC cells. This improvement resulted from the reduction of toxicity and the overcoming of homologous recombinationmediated resistance (HR). 150,151 SLNs containing resveratrol has been used to cure human breast cancer cells. Compared with free resveratrol, the authors of this study discovered that resveratrol SLNs had a significantly higher capacity to suppress cell growth. In addition, resveratrol SLNs showed a much more robust inhibitory effect on cell invasion and migration, suggesting a promising therapeutic potential in breast cancer (BreC). 152 Another study showed that SLNs can be used as carriers

| Nanostructuredlipidcarriers(NLC)
The second generation of lipid-based nanocarriers, known as NLCs, Fluvastatin, when coupled with lipoic acid and ellagic acid in a non-liposomal formulation (NLC), could be used as a candidate for the treatment of prostate cancer because the combination promotes cell death compared to free drugs. 157 NLC was used to enhance the bioavailability of lipophilic drugs such as thymoquinone (TQ). In this study, the anticancer effect of TQ-NLC, a colloidal drug carrier, was demonstrated in Hep3B liver cancer cells. 158 The case of artesunate nanoparticles modified with hyaluronic acid and cell-penetrating peptides was particularly interesting because it showed that these nanoparticles were able to effectively identify and penetrate the tumour cell membrane, leading to very effective results against HepG2 cancer cells.
NLC loaded with orcinol glycoside and coated with PEG, a nanoformulation with oral delivery capability, showed anticancer activity against gastrointestinal cancer cell lines and hepatomas. 159 NLCs loaded with 6-gingerol were developed to increase the water solubility and oral bioavailability of bioactive 6-gingerol, which is poorly soluble in water. 160

| TARG E TEDDELIVERYOF THER APEUTICNANOPARTICLE S
New discoveries in biomedical sciences have led to the development of more effective therapeutic drugs. However, a key challenge that must be overcome before the efficacy of treating various diseases can be maximized is the transport of therapeutic chemicals to the target site. Non-selectivity, undesirable side effects, limited efficacy and poor biodistribution are just some of the problems encountered when using conventional drugs. Therefore, researchers are focusing on developing systems that are both highly regulated and can serve multiple functions. The use of nanoparticles with tailored physicochemical and biological properties to deliver different chemicals to specific sites in the body is an exciting prospect. When a drug is successfully directed to a desired site and accumulates mainly there, it is called 'targeted delivery'. For efficient targeted delivery, the drug-loaded system should remain in the physiological system for an optimal period of time, escape the immunological system, target a specific cell/tissue and release the loaded therapeutic agent. 161 There are two types of targeted delivery of therapeutic nanoparticles, namely passive and active targeting.

| Passivetargeting
The term 'passive targeting' refers to a method that takes advan-

| Peptidestructure
Peptides have the ability to discretely assemble into suitable nanomaterials and actively respond to the tumour microenvironment. This ability can be achieved by modifying the conditions of synthesis and non-covalent interactions of peptides, 167 which can be designed to have a high degree of reactivity to the environment in the tumor. 168 Self-assembling peptide nanostructures, for example, can dissolve in a mildly acidic environment by protonation and disulfide bond breaking and by interaction with glutathione (GSH).
Self-assembling peptides have the potential to be used as smart nanoplatforms in cancer treatment because they are very sensitive to pH and GSH. 169,170 On

| Nano-biomedicine
Nanobiotechnology is poised to revolutionize biomedical potential worldwide in areas ranging from drug delivery to immune sensor applications. Virtually every area of medicine can benefit. Examples include cancer (nano-oncology), neurological diseases (nanoneurology), cardiovascular diseases (nano-cardiology), bone and joint diseases (nano-orthopaedics), eye diseases (nano-ophthalmology), and infectious diseases. 179 In terms of treatment, diagnosis, and monitoring, nanomedicine can regulate the biological system. This control includes the refinement of therapeutic agents and tools for pharmacological and therapeutic targeting. The advances that nanobiotechnology will bring in the areas of diagnosis, prognosis, treatment and prevention are just the beginning of the development of a wide range of applications for this technology. 180

| Nano-biomaterials
The dimensions of nanoscale materials have been reduced as they have evolved. This is currently one of the most critical areas of research to be decided upon to evaluate the performance of these materials and their specific properties. Key properties include optical properties, capillary forces, conductivity, melting temperature, electron affinity, ionization potential, reactivity and surface energy.
Nanoscience provides important opportunities for theory and computation to play a leading role in the discovery process, as experi- cartilage, skin or dental tissue. 184 The use of organic nanostructures, whether natural or artificial, has several advantages in a number of dental disciplines such as implantology, endodontics, periodontology, regenerative dentistry, and wound healing. The nanostructures offer a number of advantages, including increased colloidal stability, improved dispersibility, and enhanced surface reactivity. 185

| Drugdelivery
Currently, there is a great interest in the application of nanobiotechnology as a means to develop new drug delivery systems and tools. 186,187 A diagram of the drug delivery system is shown in Figure 5. For example, many nanoparticles represent a promising class of drug-delivery devices because they can be used in a controlled and targeted manner. The solubility and bioavailability of poorly soluble drugs can be improved by using nanosuspensions.
Many problems in the formulation and administration of poorly water-and lipid-soluble drugs can be solved by nanosuspensions.
Paclitaxel/chitosan (PTX/CS) nanosuspensions have been proposed as a potential strategy for nanodrug delivery for cancer treatment. 188 Research in nanobiotechnology also focuses on the application of magnetic properties in devices and the manufacture of materials. 189 This field of research has a wide range of applications in medicine, the best known of which is magnetic separation and magnetic resonance imaging. 189 Impedance biosensors are most commonly used to monitor markers of bone remodelling in osteoporosis, cytokinesis in cancer and to better understand neurological degenerative diseases. [190][191][192][193]

| Therapeuticdiagnosisandtreatment
Clinical diagnosis and treatment of a wide range of diseases could benefit from the application of materials that have been modified through the use of nanobiotechnology. Currently, a number of research initiatives are underway to develop a variety of innovative applications of nanoparticles that have amazing potential for drug uptake, release and therapy. 194 Doxorubicin hydrochloride (DOX) was used as a model drug to evaluate the potential of Fe 3 O 4 aqueous colloidal magnetic nanoparticles as a carrier system. 195 To improve DOX accumulation, stimuli-responsive (redox-, light-, enzyme-and pH-sensitive) graphene oxide (GO) nanostructures were developed for DOX delivery. 196 When comparing normal and malignant tissue, it should be noted that the activity of nanopolymer capsules helps to limit the release of drugs in an acidic environment. 197

| Nano-biodevicesandelectronics
The new technology and scientific field known as nano-bio de-

| Nano-filters
The separation of molecules such as proteins and DNA is a possibility for nanoscale genomics-based filtering research. It also protects against numerous biological perturbations, such as viruses up to 30 nm in diameter. 224

| Nanobeads
These are polymer beads with a diameter of 0.1 to 10 micrometres. The approach is to impregnate fluorescent crystal chips in nanobeads to make the move and establish the next level of disease therapy and diagnostics by enabling 1000 of biological interactions to jointly improve clinical diagnosis and drug development.

| Biopharmaceuticals
Nanobiotechnology has the potential to develop therapies for diseases that cannot be treated with conventional drugs. Throughout its history, the pharmaceutical industry has focused on the discovery and development of new drugs to treat more than 500 different diseases. However, between 70% and 80% of drug de- Numerous studies in the emerging field of nanomedicine are investigating its potential for use in the early stages of biomedicine.
Biomaterials and pharmaceutical formulations are the main research topics here. Animal studies and transdisciplinary investigations, which take a lot of time and resources, could provide valuable data that can be used for future applications such as diagnostic and pharmacological trials. As there is currently a global trend towards more accurate diagnoses and therapies, the development of nanodrug delivery systems and nanomedicine seems to have a promising future. However, no significant progress has been made in developing a controlled release of drugs at specific sites, technologies to assess these events, pharmacological effects at the tissue/cell level or theoretical mathematical prediction models. These are all issues that need to be improved in the future. 238,239 Whilst nanomedicine has many potential benefits, its potential hazards to humans and the environment must also be thoroughly The challenge with using metal-based nanoparticles for drug delivery, such as gold and silver nanoparticles, is that they must be biocompatible, bioadaptable and site-specific. Another challenge is the ability to penetrate the bloodstream barrier without affecting other body organs and to target infected body sites.
There is no single person, group or intellectual field capable of providing answers to the questions that nanotechnology will raise.
Developing devices to assess human exposure to engineered nanomaterials in air and water is amongst the top five problems. Due to their potential importance in regenerative and diagnostic medical applications, there is a great need for research in this area. If diseased cells could be detected more quickly, perhaps even at the level of a single diseased cell, then urgent treatment could be given to the diseased cells, preventing the disease from spreading to other regions of the body and causing further damage.

CO N FLI C TO FI NTE R E S TS TATE M E NT
The authors confirm that there are no conflicts of interest. They have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.

DATAAVA I L A B I L I T YS TAT E M E N T
All data generated or analysed during this study are included in this manuscript.