**6. Silver nanoparticles as antimicrobial agents**

Researches on the synthesis of silver nanoparticles using microbes and plant extract has become active due to its easy accessibility, non-toxicity, wide ranged applications, flexibility and essentially for its biodegradability, sustainability and cost effectivity. Various plants are being effectively used for the synthesis of metal nanoparticles. Various plant parts including fruit peels, leaves, barks, flowers, roots are used in synthesizing silver and other metal nanoparticles. Silver nanoparticles can serve as a medium for the delivery of antibiotics and disinfecting materials. Silver ions (Ag+ ) and their respective compounds are highly toxic to broad spectral microorganisms. As a biological approach, different plants.

## **7. Antibacterial**

Silver has been found in our traditional medicines and culinary for a long time. Silver is known to cause bacteriostatic (growth inhibition) and bactericidal (eradicate) properties, hence described as oligodynamic it is metals enclose ions that devastate

living cells, like fungi, bacteria, and viruses. Silver in ionic forms strongly interacts with thiol groups of vital enzymes in bacteria and inactivates them and thereby making it lose their ability to replicate their DNA. Silver compounds such as silver nitrate and silver sulfadiazine are being used to prevent bacterial growth in sterilization process of drinking water and also in burn care activities. Silver nanoparticles has been widely used as antibacterial agents for centuries that exerts bactericidal activity even at minimal concentration which has lead its use against antibiotic resistant bacteria and prevents against a broad range of pathogenic microorganisms. Silver nanoparticles have been found to destabilize the membrane potential and deplete the intracellular ATP (Adenosine tri-phosphate) levels by target resulting in death of the bacteria.

#### **8. Antifungal**

Silver displays multiple mode of inhibitory mechanisms against microorganisms. Silver nanoparticles can be actively applied in the field of plant protection following the emergence of various resistant fungal pathogens leading to the reduction in agricultural production.The antifungal potential of silver nanoparticles was tested against various human pathogens, plant pathogens, wood degrading fungi including *Aspergillusochraceus*, *Candidaalbicans*. *Macrophominaphaseolina*, *Fusariumoxysporum*, *Fusariumsolani*, *Trichoderma* sp., and *Alternariaalternate* [36], *Raffaelea* sp., *Alternariabrassicicola*, *Botrytiscinerea*, *Cladosporiumcucumerinum*, *Corynesporacassiicola*, *Cylindrocarpondestructans*, *Didymellabryoniae*, *Glomeirellacingulata*, *Monosporascuscannonballus*, *Pythiumaphanidermatum*, *Pythiumspinosum*, *Stemphyliumlycopersici* [37] commercially important fungal pathogens were tested to check the fungicidal properties of silver nanoparticles. The findings suggest that silver nanoparticles are capable of inhibiting the above mentioned pathogens with slight variations according to the silver nanoparticles applied. Most of the fungi showcased higher inhibition rate at low concentrations of silver nanoparticles. Though very little is known about the effects of silver nanoparticles on phytopathogenic fungi, certain studies carried out proved the efficiency of silver nanoparticle on inhibition of mycelial growth and conidial germination.

#### **9. Anticancer**

Cancer cells have abnormal metabolic behaviors and genomic expressions by causing various pathological and metabolic alterations in cellular surroundings developed by cell signaling, rapid proliferation, angiogenesis and metastasis. Many studies reported depicts that the use of silver nanoparticles enhances the chemotherapeutic efficacy against multidrug resistant cancer cells emphasized with specifications and combinations. Nanoparticles coated with specific binders can recognize particular surface receptors and targets only the cancerous cells or the anomalous cells. Many platinum nanoparticles and platinum based compounds were approved as anticancer agents. Though many cancer types are susceptible to platinum based drugs accompanied with toxic side effects. Consequently other metal nanoparticles are explored in search of a better anticancer agents, while silver with advantageous antimicrobial activity arose into interest as an effective anticancer agent. Cancer cells such as HepG2 (human liver cancer cells) [24], HCT (Human colon cancer cells), HeLa (Human cervical adenocarcinoma cells), MCF 7 (Human breast adenocarcinoma cells) [24] and various other cancer cells were used to study the cytotoxicity effect of silver nanoparticles. Silver nanoparticles synthesized using different plant extracts showed potentially high cytotoxicity and less

**87**

*Biomedical Applications of Silver Nanoparticles DOI: http://dx.doi.org/10.5772/intechopen.99367*

**10. Silver nanoparticles for drug-delivery systems**

**11. Silver nanoparticles for catheter modification**

efficacy and durability of the medical devices.

**12. Silver nanoparticles for dental applications**

cell viability against various cancer cells. Moreover, nanoparticles of 5-35 nm sizes effectively induced cell death through mitochondrial structure targeting [38].

Metallic nanoparticles had emerge as probable antimicrobial agents due to their

ultra-small size, high surface to volume ratio, novel physiochemical properties rooted from interaction with microbes including cellular uptake and aggregation leading to toxicity and death of the microbe [39]. Ligand dependent silver release with drug may offer potent synergistic antimicrobial activities not only for drug but also for AgNPs due to their short carbon chain and weak binding atom of oxygen. Therefore, the optimization of the surface ligands such as coordination atoms, carbon chain lengths and terminal groups is very important to prepare nanoparticles for commercial applications against infectious diseases [40]. Research evidences shows that modification of silver nanoparticles could be exploited for drug delivery and are used to modulate the toxic actions of drugs. It also accompanies that as the concentration increases, non-significant reduction in the cytotoxic actions for the

silver nanoparticle conjugates were relative to the cytotoxicity of the cells.

In generalmicrobes adhere on the surface of the catheters and growsrapidly forming biofilmsin such environmental conditions leading to bloodstream infections, even worse. Silver impregnated catheters have already been used in clinical fields and silver nanoparticles are applied in number of biomedical devices. Methods like solvent casting, electrospinning, electrospraying, and silver iontophoretic technology were being used for the synthesis of silver impregnated catheters. The nature of silver nanoparticles and the coating incorporation will determine the

Silver has been proven to be less toxic and a good biocompatible with human cells [41]. Silver nanoparticles are used as endodontics, several areas of dentistry such as implantology, restorative dentistry and dental prostheses. Use of silver nanoparticles in dentistry is mainly to inhibit or decrease the growth of microbial colonization over the dental materials to improve and maintain oral health. Other advantage being the penetration possibility of silver nanoparticles through cell membranes resulting in higher antimicrobial activity especially for biofilm forming microbes. Silver nanoparticles incorporated in dental materials through distinct methods depending on the type of materials. For dental implants titanium samples are immersed in silver nitrate solution and irradiated with UV(Ultraviolet) light after wash and dried [42]. Whereas, for adhesive/resin composite a monomer preferably 2-tert-butylaminoethyl-methacrylate is added to improve the silver solubility [43]. In order to improve quality and durability of polymeric restorative materials many studies are being performed. Rather than notable advancements, restoration composite materials accumulate more biofilms. Actually an imperfect sealing between the restoration composite material and the cavity wall leads to the colonization of oral microbes resulting in secondary caries leading to replacements. To avoid such complications,

restorative materials with antimicrobial property has to be incorporated.

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

living cells, like fungi, bacteria, and viruses. Silver in ionic forms strongly interacts with thiol groups of vital enzymes in bacteria and inactivates them and thereby making it lose their ability to replicate their DNA. Silver compounds such as silver nitrate and silver sulfadiazine are being used to prevent bacterial growth in sterilization process of drinking water and also in burn care activities. Silver nanoparticles has been widely used as antibacterial agents for centuries that exerts bactericidal activity even at minimal concentration which has lead its use against antibiotic resistant bacteria and prevents against a broad range of pathogenic microorganisms. Silver nanoparticles have been found to destabilize the membrane potential and deplete the intracellular ATP (Adenosine tri-phosphate) levels by target resulting in death of the bacteria.

Silver displays multiple mode of inhibitory mechanisms against microorganisms. Silver nanoparticles can be actively applied in the field of plant protection following the emergence of various resistant fungal pathogens leading to the reduction in agricultural production.The antifungal potential of silver nanoparticles was tested against various human pathogens, plant pathogens, wood degrading fungi including *Aspergillusochraceus*, *Candidaalbicans*. *Macrophominaphaseolina*, *Fusariumoxysporum*, *Fusariumsolani*, *Trichoderma* sp., and *Alternariaalternate* [36], *Raffaelea* sp., *Alternariabrassicicola*, *Botrytiscinerea*, *Cladosporiumcucumerinum*, *Corynesporacassiicola*, *Cylindrocarpondestructans*, *Didymellabryoniae*, *Glomeir-*

*ellacingulata*, *Monosporascuscannonballus*, *Pythiumaphanidermatum*, *Pythiumspinosum*, *Stemphyliumlycopersici* [37] commercially important fungal pathogens were tested to check the fungicidal properties of silver nanoparticles. The findings suggest that silver nanoparticles are capable of inhibiting the above mentioned pathogens with slight variations according to the silver nanoparticles applied. Most of the fungi showcased higher inhibition rate at low concentrations of silver nanoparticles. Though very little is known about the effects of silver nanoparticles on phytopathogenic fungi, certain studies carried out proved the efficiency of silver nanoparticle on inhibition of

Cancer cells have abnormal metabolic behaviors and genomic expressions by causing various pathological and metabolic alterations in cellular surroundings developed by cell signaling, rapid proliferation, angiogenesis and metastasis. Many studies reported depicts that the use of silver nanoparticles enhances the chemotherapeutic efficacy against multidrug resistant cancer cells emphasized with specifications and combinations. Nanoparticles coated with specific binders can recognize particular surface receptors and targets only the cancerous cells or the anomalous cells. Many platinum nanoparticles and platinum based compounds were approved as anticancer agents. Though many cancer types are susceptible to platinum based drugs accompanied with toxic side effects. Consequently other metal nanoparticles are explored in search of a better anticancer agents, while silver with advantageous antimicrobial activity arose into interest as an effective anticancer agent. Cancer cells such as HepG2 (human liver cancer cells) [24], HCT (Human colon cancer cells), HeLa (Human cervical adenocarcinoma cells), MCF 7 (Human breast adenocarcinoma cells) [24] and various other cancer cells were used to study the cytotoxicity effect of silver nanoparticles. Silver nanoparticles synthesized using different plant extracts showed potentially high cytotoxicity and less

**86**

**8. Antifungal**

**9. Anticancer**

mycelial growth and conidial germination.

cell viability against various cancer cells. Moreover, nanoparticles of 5-35 nm sizes effectively induced cell death through mitochondrial structure targeting [38].
