Silver Nanoparticles in Various New Applications

*Ainil Hawa Jasni, Azirah Akbar Ali, Suresh Sagadevan and Zaharah Wahid*

#### **Abstract**

The use of silver in antimicrobial management is very ancient. Silver-based materials have proven interesting, practical, and promising for various applications. Silver nanoparticles (AgNPs) have been one of the nanostructures most studied and investigated over the past several years. AgNPs have greater specific properties depending on their size and form. These noble synthesised metrics have numerous optical, electrical, catalytic, and optical characteristics. These properties are ideal for many fields, depending on their size and shape. The outbreak of multiple infectious diseases has been a major strain on global economies and the public health sector. Extensive treatments have been suggested for disease control in environments containing infectious diseases through advanced disinfectant nanomaterials. This chapter investigates the application and mechanism of silver nanoparticles in certain nanobiotechnology sectors as a useful nanomaterial. In the sense of the market statistical survey research, AgNPs are emerging as one of the fastest developing product groups in the nanotechnology industry, providing a wide variety of nanosilver products in various applications. Lastly, due to the massive use of AgNPs in products recently, there are many concerns about AgNPs toxicity and safety had also been discussed.

**Keywords:** nanotechnology, metal-nanoparticles, silver nanoparticles, nanomaterials and applications

#### **1. Introduction**

The phrase 'nanotechnology' was proposed in 1974 by Norio Taniguchi, a researcher at the University of Tokyo, who pointed to the possibilities of treating nanometric materials with dimensions between 1 and 100 nm. In this variety of sizes, particles show new physical and chemical properties that can be used in various fields of science, such as medicine, food, textiles, chemicals, and energy, to name a few. Nanotechnology is a dynamic interdisciplinary science consisting of nanochemistry, nanophysics, nanomaterials science, nanoelectronics, optoelectronics and nanoengineering, nanobionics and nanometrology, nanodevice-building and nano-craft [1].

Metal nanoparticles are currently starting to be used as silver (Ag), gold (Au), and copper (Cu) with biochemical, optical, and magnetic properties, of which AgNPs are the most studied because of their antimicrobial ability for microbes, viruses, and fungi [2]. AgNPs have been used in nanomedicine and also being

known as antimicrobial agents and disinfectants without adverse effects. AgNPs have been used against both aerobic and anaerobic microbes. As correlated with other compounds, great interest in AgNPs increased because it shows more efficacy [3]. Its antimicrobial properties can be linked to many internal systems such as communicating with the S–S disulfide bond of the metabolic enzymes, cleaving cells, and disrupting the respiratory chain [4]**.**

Antimicrobial resistance is a public health problem increasing day by day as it is caused by microorganisms that gradually became resistant to drug therapy. Population overcrowding, urbanisation, inadequate water supply, and lack of environmental hygiene are also the major factors of rapid disease outbreaks. Many scientists had developed new effective antimicrobial reagents against the increasing number of microbial resistances with various antibiotics, due to clinical limits on antibiotic prescription. The use of smaller-size AgNPs with a larger surface area to volume ratio as they can enter cell cytoplasm rapidly and kill microorganisms effectively was proven compared to larger AgNPs. At very low concentrations of 5 mg/ml only, AgNPs act as effective antimicrobial activity against both gram-positive and negative bacteria. Furthermore, it has been revealed that AgNPs solution showed an anti-fouling effect on certain bacteria strains [5].

Fungal infections are also very common in immunosuppressed patients. Overcoming fungal diseases is a boring process due to the small number of antifungal drugs available in the current scenario. There is a solution to the urgent and inevitable development of antifungal agents that would be non-toxic, biocompatible, and eco-friendly. At this part, AgNPs play an important role as antifungal agents against various fungal diseases. AgNPs were tested towards different phytopathogens like *Fusarium solani*, Curvularia lunata, and showed efficient antifungal activity [6].

Nowadays, the AgNPs synthesis process is cost-effective, economical, energyefficient, and offers healthy workplaces to societies. Hence, health and environmental safety surely leading to less waste and safer goods. The utilisation of the plant method can be useful in comparison to other biological processes. The plant-based method can shorten the time-consuming processes compared to microbes and retain their capacity during AgNPs synthesis.

#### **1.1 New emerging applications of AgNPs**

The most promising nanomaterials for current commercial applications are AgNPs. They function as antibacterial agents and are used in textiles, electronics products, the medical industry, environmental applications, coatings, food preservation, and other applications. AgNPs are widely used for different uses from home appliances and are used as a disinfectant for sewage treatment and surgical equipment for sterilisation [7]. The most promising nanomaterials for current commercial applications are AgNPs are used as a coating for cardiovascular implants and central venous and neurosurgical catheters, in latex membranes where AGNPs are applied as a biomaterial for a skin regeneration treatment and monitor the delivery rate of the nanoparticle membranes [8].

AgNPs are used in biosensors, where the silver nanoparticles content is used for quantitative detection as biological tags. AgNPs are also incorporated in clothes, shoes, paints, wound dressings, appliances, cosmetics, and plastics. AgNPs are used to improve conductivity in conductive tinting and are incorporated into composite systems. AgNPs are used in opical applications for the effective collection and enhanced optical spectroscopy, including improved metal fluorescence (MEF) and superficial Raman dispersion (SERS). With regard to nanoelectronics, optoelectronics and nanoengineering, innovative technological processes, nanomotors,

**219**

**Figure 2.**

*The advantages and disadvantages of AgNPs utilisation.*

**Figure 1.**

*Various applications of silver nanoparticles.*

*Silver Nanoparticles in Various New Applications DOI: http://dx.doi.org/10.5772/intechopen.96105*

nanoactuators, nanodevices, micro-opto-electro-mechanical systems (MEMS, MOEMS), ultra-large integrated circuits (ULCI), nano-robots, etc. were the new applications. **Figure 1** is the various applications of AgNPs meanwhile **Figure 2** are

the listed advantages and disadvantages of AgNPs utilisation.

nanoactuators, nanodevices, micro-opto-electro-mechanical systems (MEMS, MOEMS), ultra-large integrated circuits (ULCI), nano-robots, etc. were the new applications. **Figure 1** is the various applications of AgNPs meanwhile **Figure 2** are the listed advantages and disadvantages of AgNPs utilisation.

**Figure 1.**

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

cells, and disrupting the respiratory chain [4]**.**

anti-fouling effect on certain bacteria strains [5].

retain their capacity during AgNPs synthesis.

**1.1 New emerging applications of AgNPs**

rate of the nanoparticle membranes [8].

known as antimicrobial agents and disinfectants without adverse effects. AgNPs have been used against both aerobic and anaerobic microbes. As correlated with other compounds, great interest in AgNPs increased because it shows more efficacy [3]. Its antimicrobial properties can be linked to many internal systems such as communicating with the S–S disulfide bond of the metabolic enzymes, cleaving

Antimicrobial resistance is a public health problem increasing day by day as it is caused by microorganisms that gradually became resistant to drug therapy. Population overcrowding, urbanisation, inadequate water supply, and lack of environmental hygiene are also the major factors of rapid disease outbreaks. Many scientists had developed new effective antimicrobial reagents against the increasing number of microbial resistances with various antibiotics, due to clinical limits on antibiotic prescription. The use of smaller-size AgNPs with a larger surface area to volume ratio as they can enter cell cytoplasm rapidly and kill microorganisms effectively was proven compared to larger AgNPs. At very low concentrations of 5 mg/ml only, AgNPs act as effective antimicrobial activity against both gram-positive and negative bacteria. Furthermore, it has been revealed that AgNPs solution showed an

Fungal infections are also very common in immunosuppressed patients. Overcoming fungal diseases is a boring process due to the small number of antifungal drugs available in the current scenario. There is a solution to the urgent and inevitable development of antifungal agents that would be non-toxic, biocompatible, and eco-friendly. At this part, AgNPs play an important role as antifungal agents against various fungal diseases. AgNPs were tested towards different phytopathogens like *Fusarium solani*, Curvularia lunata, and showed efficient antifungal

Nowadays, the AgNPs synthesis process is cost-effective, economical, energyefficient, and offers healthy workplaces to societies. Hence, health and environmental safety surely leading to less waste and safer goods. The utilisation of the plant method can be useful in comparison to other biological processes. The plant-based method can shorten the time-consuming processes compared to microbes and

The most promising nanomaterials for current commercial applications are AgNPs. They function as antibacterial agents and are used in textiles, electronics products, the medical industry, environmental applications, coatings, food preservation, and other applications. AgNPs are widely used for different uses from home appliances and are used as a disinfectant for sewage treatment and surgical equipment for sterilisation [7]. The most promising nanomaterials for current commercial applications are AgNPs are used as a coating for cardiovascular implants and central venous and neurosurgical catheters, in latex membranes where AGNPs are applied as a biomaterial for a skin regeneration treatment and monitor the delivery

AgNPs are used in biosensors, where the silver nanoparticles content is used for quantitative detection as biological tags. AgNPs are also incorporated in clothes, shoes, paints, wound dressings, appliances, cosmetics, and plastics. AgNPs are used to improve conductivity in conductive tinting and are incorporated into composite systems. AgNPs are used in opical applications for the effective collection and enhanced optical spectroscopy, including improved metal fluorescence (MEF) and superficial Raman dispersion (SERS). With regard to nanoelectronics, optoelectronics and nanoengineering, innovative technological processes, nanomotors,

**218**

activity [6].

*Various applications of silver nanoparticles.*

**Figure 2.** *The advantages and disadvantages of AgNPs utilisation.*

## **2. Nanobiotechnology related applications**

Many research techniques are introduced in various physical and chemical methods by scientists to develop metal nanoparticles. However, these approaches for various synthetic compounds are costly. They may result in the presence on the surface of nanoparticles of toxic chemical organisms, which have potentially harmful impacts in diverse biological and biomedical uses [9]. The need to develop environmentally sustainable methods for synthesising nanoparticles by "green synthesis" is increasing.

AgNPs are among the most thoroughly studied nanomaterials and the most common target of the above listed 'green' methods, which fascinate scientists. The research fields of research and the development of nanoparticles with plant extract are emerging. Intracellularly and extracellularly, the plant structures can be used to manufacture various metal nanoparticles [10]. Intracellular processes in nanoparticles' processing include seed plants in high-metal media and hydroponic solutions, such as metal-rich soils. While extract leaves, prepared by boiling or moulding leaves in water or ethanol, are an extracellular processing nanoparticles method [11]. *Medicago sativa* is a plant that can synthesise silver and gold nanoparticles by exploiting its biomolecule which is the first plant recorded used for the extracellular synthesis of a nanoparticle [12]. Since then, plants have gained considerable attention as a medium for the synthesis of nanoparticles. AgNPs have been identified for use in the treatment of wounds, burns, in the development of nano-containing materials for bone implants, dental materials, and antibacterial, antifungal, antiviral, anti-protozoans, anti-arthropods, anti-larvicidal anti-cancerous agents. AgNO3 was used clinically as an important antibacterial agent until the invention of AgNPs [13]. The use of nanostructured materials in nanotechnology has been growing quite rapidly in the last few years. It is used for promising biomedical applications to detect and prevent different forms of diseases. AgNPs can be easily coated with titanium or titanium alloys and are used for dental titanium implants [14].

#### **2.1 Wound healing**

Wound healing is a complex biochemical pathway, including several cells that work to regenerate functional skin, including skin cells and immune cells. The use of silver in wound management is very ancient. Pharmaceutical companies and scientists are searching for new antibacterial due to infectious disease attacks and the development of antibiotic resistance. Silver-based products with more complex shapes and increased effectiveness than conventional dressings have been patented and commercialised in wound dressing applications. In wound care, biopolymers combined with a bioactive antimicrobial, antibacterial and anti-inflammatory nanoparticles have great potential to promote wound healing, particularly in the management of diabetic foot ulcers (DFUs), which still pose a huge problem and are associated with high amputation rates and clinical costs [15].

Silver plays an important function in wound healing and, along with its distinctive role in avoiding infection, AgNPs may also facilitate the transformation of fibroblasts into myofibroblasts, which in turn facilitates wound contracting, accelerates the pace of healing, and induces keratinocyte proliferation and relocation [16]. As reported by [17], the effect of nanosilver was tested in vitro and in vivo, and the result showed that, at a concentration of 10 ppm, AgNPs facilitated fibroblast migration, which also demonstrated higher levels of the alpha-smooth muscle actin (alpha-SMA) marker, signalling silver's capacity to turn fibroblasts into myofibroblasts and speed up the healing phase. Several laboratory animal models, such as rat (*Rattus norvegicus*), rabbit (*Oryctolagus cuniculus*), and pig (*Sus scrofa*),

**221**

*Silver Nanoparticles in Various New Applications DOI: http://dx.doi.org/10.5772/intechopen.96105*

cals on tissue regeneration and wound healing.

**2.2 Antimicrobial applications**

ganisms of the targets [27].

are used to test AgNP antibacterial effectiveness in wound healing [18, 19]. Studies in the Sprague–Dawley rat and pathogen-free domestic pigs found that AgNPloaded dressing speeds up excisional wound healing, while after treatment, the wounds suffer from bacterial infection [18]. Pig explant culture model and mouse experiments have reported that AgNP dressing prevents epidermal cells' proliferation and re-epithelialisation of wounds [20]. The caudal fin of Zebrafish, including the epidermis, blood vessels, nerves, pigment cells, and fibroblast-like cells, has a relatively basic but symmetric structure [21]. The major wound healing mechanisms in mammals include the regenerative adult zebrafish fins [22]. Furthermore, the fin regeneration of adult zebrafish is an ideal model for studying the effects of chemi-

The interest and understanding of the antibacterial potency of AgNPs have been highlighted with the advancement of nanotechnology. A comparative study of AgNPs, AgNO3, and AgCl find that the antibacterial efficacy of AgNPs is greater than that of free silver ions [23]. The AgNPs have known to be an active bactericide against several bacteria, both Gram-negatives and Gram-positives, including several highly pathogenic bacterial strains [13]. As reported by [24], an experiment was carried out using a model of both Gram-positive (*Staphylococcus aureus*) and Gramnegative (*Escherichia coli*) bacteria to explore the antibacterial properties of AgNPs. *E. coli* development is inhibited at a very low concentration of AgNPs (3.3 nM), which is ten times lower than the minimum inhibitory concentration (MIC) of *S. aureus* (33 nM). The robust antibacterial efficacy and improved stability of AgNPs (10–15 nm) against various drug-resistant bacterial strains were recorded in another study. There are several records that the dose-dependent antibacterial activity of AgNPs is more prevalent against Gram-negative than Gram-positive bacteria [25]. Furthermore, the AgNPs also found potential antibacterial activity against multidrug-resistant gram-negative such as *Klebsiella pneumonia* and *E. coli* and for gram-positive bacteria *like S. aureus*, which isolated from human pathogens. Different parameters impact antibacterial behaviour AgNPs including size and shape, time of exposure [26]. Silver concentration, compound forms, and microor-

Silver reagent (AgNO3, AgCl) has to be high enough to inhibit bacterial cell growth. In the case of aquaculture, one of the greatest problems was preventing diseases caused by viruses, microbes, fungi, and parasites. Traditionally, antimicrobials have been used to eliminate bacterial infections in aquaculture. However, excessive application of these chemicals has caused resistant strains, rendering the treatments not so effective. A previous study by [28] analysed resistant strains in fish farmers in 25 countries showed that tetracycline was the antibiotic most widely used. The isolated tilapia bacteria show a wide variety of antibiotic resistance, such as tetracycline, erythromycin, and streptomycin. Resistant strains were *Aeromonas salmonicida, Photobacterium damselae, Yersinia ruckeri, Listeria sp, Vibrio sp, Pseudomonas s*p, and *Edwardsiella sp.* AgNPs were synthesised to control Vibrio harveyi by *Camellia sinensis* in infected *Feneropenaeus indicus* organisms. In vivo tests have shown that the concentration of 10 μg mL-1 inhibited 70 percent bacterial growth [29]. *Bacillus subtilis*, a non-pathogenic organism used to synthesise nano compounds, was evaluated for its antimicrobial effect on *V. parahaemolyticus* and *V. harveyi* in infected *Litopenaeus vannamei*. The results showed a survival rate of 1% in the control group, but a survival rate of 90% with nano compounds [30]. AgNPs encapsulated with starch and applied in immersion baths (20 minutes) at 10 ng of nanoparticles' concentrations, infected by *Ichthyophthirius multifiliis*

*Silver Nanoparticles in Various New Applications DOI: http://dx.doi.org/10.5772/intechopen.96105*

*Silver Micro-Nanoparticles - Properties, Synthesis, Characterization, and Applications*

Many research techniques are introduced in various physical and chemical methods by scientists to develop metal nanoparticles. However, these approaches for various synthetic compounds are costly. They may result in the presence on the surface of nanoparticles of toxic chemical organisms, which have potentially harmful impacts in diverse biological and biomedical uses [9]. The need to develop environmentally sustainable methods for synthesising nanoparticles by "green

AgNPs are among the most thoroughly studied nanomaterials and the most common target of the above listed 'green' methods, which fascinate scientists. The research fields of research and the development of nanoparticles with plant extract are emerging. Intracellularly and extracellularly, the plant structures can be used to manufacture various metal nanoparticles [10]. Intracellular processes in nanoparticles' processing include seed plants in high-metal media and hydroponic solutions, such as metal-rich soils. While extract leaves, prepared by boiling or moulding leaves in water or ethanol, are an extracellular processing nanoparticles method [11]. *Medicago sativa* is a plant that can synthesise silver and gold nanoparticles by exploiting its biomolecule which is the first plant recorded used for the extracellular synthesis of a nanoparticle [12]. Since then, plants have gained considerable attention as a medium for the synthesis of nanoparticles. AgNPs have been identified for use in the treatment of wounds, burns, in the development of nano-containing materials for bone implants, dental materials, and antibacterial, antifungal, antiviral, anti-protozoans, anti-arthropods, anti-larvicidal anti-cancerous agents. AgNO3 was used clinically as an important antibacterial agent until the invention of AgNPs [13]. The use of nanostructured materials in nanotechnology has been growing quite rapidly in the last few years. It is used for promising biomedical applications to detect and prevent different forms of diseases. AgNPs can be easily coated with

titanium or titanium alloys and are used for dental titanium implants [14].

are associated with high amputation rates and clinical costs [15].

Wound healing is a complex biochemical pathway, including several cells that work to regenerate functional skin, including skin cells and immune cells. The use of silver in wound management is very ancient. Pharmaceutical companies and scientists are searching for new antibacterial due to infectious disease attacks and the development of antibiotic resistance. Silver-based products with more complex shapes and increased effectiveness than conventional dressings have been patented and commercialised in wound dressing applications. In wound care, biopolymers combined with a bioactive antimicrobial, antibacterial and anti-inflammatory nanoparticles have great potential to promote wound healing, particularly in the management of diabetic foot ulcers (DFUs), which still pose a huge problem and

Silver plays an important function in wound healing and, along with its distinctive role in avoiding infection, AgNPs may also facilitate the transformation of fibroblasts into myofibroblasts, which in turn facilitates wound contracting, accelerates the pace of healing, and induces keratinocyte proliferation and relocation [16]. As reported by [17], the effect of nanosilver was tested in vitro and in vivo, and the result showed that, at a concentration of 10 ppm, AgNPs facilitated fibroblast migration, which also demonstrated higher levels of the alpha-smooth muscle actin (alpha-SMA) marker, signalling silver's capacity to turn fibroblasts into myofibroblasts and speed up the healing phase. Several laboratory animal models, such as rat (*Rattus norvegicus*), rabbit (*Oryctolagus cuniculus*), and pig (*Sus scrofa*),

**2. Nanobiotechnology related applications**

synthesis" is increasing.

**2.1 Wound healing**

**220**

are used to test AgNP antibacterial effectiveness in wound healing [18, 19]. Studies in the Sprague–Dawley rat and pathogen-free domestic pigs found that AgNPloaded dressing speeds up excisional wound healing, while after treatment, the wounds suffer from bacterial infection [18]. Pig explant culture model and mouse experiments have reported that AgNP dressing prevents epidermal cells' proliferation and re-epithelialisation of wounds [20]. The caudal fin of Zebrafish, including the epidermis, blood vessels, nerves, pigment cells, and fibroblast-like cells, has a relatively basic but symmetric structure [21]. The major wound healing mechanisms in mammals include the regenerative adult zebrafish fins [22]. Furthermore, the fin regeneration of adult zebrafish is an ideal model for studying the effects of chemicals on tissue regeneration and wound healing.

#### **2.2 Antimicrobial applications**

The interest and understanding of the antibacterial potency of AgNPs have been highlighted with the advancement of nanotechnology. A comparative study of AgNPs, AgNO3, and AgCl find that the antibacterial efficacy of AgNPs is greater than that of free silver ions [23]. The AgNPs have known to be an active bactericide against several bacteria, both Gram-negatives and Gram-positives, including several highly pathogenic bacterial strains [13]. As reported by [24], an experiment was carried out using a model of both Gram-positive (*Staphylococcus aureus*) and Gramnegative (*Escherichia coli*) bacteria to explore the antibacterial properties of AgNPs. *E. coli* development is inhibited at a very low concentration of AgNPs (3.3 nM), which is ten times lower than the minimum inhibitory concentration (MIC) of *S. aureus* (33 nM). The robust antibacterial efficacy and improved stability of AgNPs (10–15 nm) against various drug-resistant bacterial strains were recorded in another study. There are several records that the dose-dependent antibacterial activity of AgNPs is more prevalent against Gram-negative than Gram-positive bacteria [25]. Furthermore, the AgNPs also found potential antibacterial activity against multidrug-resistant gram-negative such as *Klebsiella pneumonia* and *E. coli* and for gram-positive bacteria *like S. aureus*, which isolated from human pathogens. Different parameters impact antibacterial behaviour AgNPs including size and shape, time of exposure [26]. Silver concentration, compound forms, and microorganisms of the targets [27].

Silver reagent (AgNO3, AgCl) has to be high enough to inhibit bacterial cell growth. In the case of aquaculture, one of the greatest problems was preventing diseases caused by viruses, microbes, fungi, and parasites. Traditionally, antimicrobials have been used to eliminate bacterial infections in aquaculture. However, excessive application of these chemicals has caused resistant strains, rendering the treatments not so effective. A previous study by [28] analysed resistant strains in fish farmers in 25 countries showed that tetracycline was the antibiotic most widely used. The isolated tilapia bacteria show a wide variety of antibiotic resistance, such as tetracycline, erythromycin, and streptomycin. Resistant strains were *Aeromonas salmonicida, Photobacterium damselae, Yersinia ruckeri, Listeria sp, Vibrio sp, Pseudomonas s*p, and *Edwardsiella sp.* AgNPs were synthesised to control Vibrio harveyi by *Camellia sinensis* in infected *Feneropenaeus indicus* organisms. In vivo tests have shown that the concentration of 10 μg mL-1 inhibited 70 percent bacterial growth [29]. *Bacillus subtilis*, a non-pathogenic organism used to synthesise nano compounds, was evaluated for its antimicrobial effect on *V. parahaemolyticus* and *V. harveyi* in infected *Litopenaeus vannamei*. The results showed a survival rate of 1% in the control group, but a survival rate of 90% with nano compounds [30]. AgNPs encapsulated with starch and applied in immersion baths (20 minutes) at 10 ng of nanoparticles' concentrations, infected by *Ichthyophthirius multifiliis*

and *Aphanomyces* parasites, anti-parasitic and antifungal impact. The findings revealed that the fish recovered after three days without any toxic impact on the use of AgNPs [31]. Much research has been done to prove the effectiveness of silver nanoparticles as disease control in aquaculture (**Table 1**).
