# Fungi-Templated Silver Nanoparticle Composite: Synthesis, Characterization, and Its Applications
## 3 Results and Discussion
### Antibacterial Studies  
AgNPs are known to possess a wide spectrum of antibacterial, antifungal, and antiviral properties. AgNPs can penetrate the bacterial cell wall, thereby changing the structural properties of the cell membrane, which results in cell death. The pronounced antibacterial effects of AgNPs can be attributed to the particle size and large surface-to-volume ratio. AgNPs efficiently increase the cell membrane's permeability, interrupt cell replication by hindering the replication of deoxyribonucleic acid, and produce reactive oxygen species. AgNPs, when integrated into a solid support, exhibit enhanced antibacterial activity due to the slow and steady release of silver ions that results in cell death. The silver ions released adhere to the cytoplasmic membrane and cell wall, which eventually increases cell permeability and thereby leads to disruption of the bacterial envelope. The uptake of silver ions deactivates the respiratory enzymes, thereby generating reactive oxygen species. Reactive oxygen species efficiently disrupt the cell membrane and manifest the denaturation of deoxyribonucleic acid (DNA). Silver ions specifically interact with the sulphur and phosphorous present in DNA, leading to problems in DNA replication, reproduction  
Figure 4: (**a**) Degradation studies using UV-visible spectroscopy. (**b**) Plot of percentage decomposition vs. time.  
of cells, or termination of microorganisms. Additionally, this interrupts the synthesis of proteins, leading to the denaturation of ribosomes in the cytoplasm of the cell (Figure 5) [17].  
The antibacterial property of FH-AgNPs was studied against _Escherichia coli_ and _Staphylococcus aureus_ using the agar gel diffusion technique [28]. The FH-AgNPs' activity was compared with the standard antibiotic ampicillin. The antibacterial activity of the composite with silver nanoparticles was close to that of ampicillin. In general, AgNP-based composites are found to possess higher antibacterial activity due to the combined effect of the counterpart and the slow silver release rate. Ag ions are gradually released from FH-AgNPs, which can increase the exposure time and result in better bacteriolysis. Ag ions can bind crucial biomolecules such as DNA, RNA, and proteins, inhibiting their function. Furthermore, the composite can induce oxidative stress in bacterial cells. As a result, these composites render an oligodynamic effect, wherein they exhibit a bacteriostatic or even a bactericidal impact. The compound was prepared in water (2 mg/mL) and the zone of inhibition was measured after 48 h. An amount of 200 \(\mu\)g of the composite exhibited a maximum antibacterial property against _E. coli_. The results are tabulated in Table 1. In presence of AgNPs in the composite induce oxidative stress releasing hydroxyl radicals that attack the bacterial cell wall, thereby disintegrating the same and leading to bacteriostatic/bactericidal effects.  
Figure 5: Mechanism of antibacterial action of AgNPs. (1) Ag\({}^{+}\) ions disrupt cell wall. AgNPs release Ag\({}^{+}\) ions which adhere to the bacterial cell wall and thereby pass through the cell wall and cytoplasmic membrane. (2) Denaturation of cell wall by AgNPs. AgNPs accumulate on the cell wall and cytoplasmic membrane and cause membrane denaturation. (3) Disruption of cell membrane by reactive oxygen species. The reactive oxygen species produced by AgNPs lead to disruption of cell membrane. (4) Denaturation of ribosomes. Silver ions, after moving into the cell cytoplasm, adhere to the ribosome and thereby hinder the synthesis of proteins. (5) Interruption in DNA replication. The process of DNA replication is hindered when AgNPs bind to various heteroatoms such as nitrogen and sulphur present in DNA.