## 4 Discussion  
Although the use of silver and silver salts as antibacterial agents is an ancient method, silver nanoparticle (AgNP) fabrication has only recently been developed. Silver nanoparticles are well known for their antimicrobial activity, and there are also reports of their acute and chronic toxicity [36; 37]. With this in mind, nanoparticles were obtained via green synthesis with the addition of compounds/peptides/chemical groups on their surfaces. This method is able to reduce toxicity to allow the application of nanoparticles in the treatment of human infectious diseases. Among the possible coatings, chitosan-coated silver nanoparticles have attracted significant attention in the biomedical field because of their unique biodegradable, biocompatible, nontoxic, and antimicrobial nature [38]. Many scientists have reported that chitosan has a strong affinity for metal ions as a result of a large number of amino and hydroxyl groups. In a study conducted by [PERSON] et al. (2018), the role of the chitosan amino group was defined as being crucial for metal ion release and the formation of CH-AgNPs [39]. Plants represent the main source for NP synthesis. Several studies have demonstrated that the polyphenols present in plant extracts play a major role in the reduction of Ag\({}^{+}\) ions [40]. In the present study, the antibacterial effect of CH-AgNPs prepared using _Prunus cerasus_ leaf extract was assessed. The multitude of bioactive compounds present in _Prunus cerasus_ makes it an excellent candidate for the synthesis of nanoparticles [41]. Moreover, the synthesis of metal nanoparticles using _Prunus cerasus_ has not been explored to any great extent. The results of UV-visible spectroscopy obtained in our study revealed a difference in size between AgNPs and CH-AgNPs. The CH-AgNPs were larger than uncoated AgNPs since layers of chitosan were observed to be wrapped around AgNPs, as in the work described by [PERSON] et al. (2013) [42]. The zeta potential on the surface of nanoparticles indicates the particles are stable. Nanoparticles possessing higher negative or positive zeta potentials will tend to repel each other and do not form aggregates [43; 44]. Our synthesized nanoparticles were found to be more stable than those previously reported in studies [45]. In the current study, the FT-IR analysis showed that numerous amino groups act as capping  
Figure 7: Antibacterial activity of nanoparticles against (**A**) a panel of Gram-negative bacteria: _E. coli_ ATCC, _E. coli_ MS, _E. coli_ MDR, _K. pneumoniae_ ATCC, _K. pneumoniae_ MS, and _K. pneumoniae_ MDR; (**B**) _S. aureus_ ATCC, _S. aureus_ MS, _S. aureus_ MDR, _E. faecalis_ ATCC, _E. faecalis_ MS, and _E. faecalis_ MDR. \({}^{*}p<0.05\). agents. The results clearly indicate that these identified amino groups are responsible for the interaction with the metal surface, acting as capping sites for AgNP stabilization [46]. From the results, it can be concluded that capping agents allow proteins to bind to AgNPs by the electrostatic attraction of negatively charged carboxylate groups present in the protein secreted by plants [47]. Many of the peaks observed in the IR spectra of AgNPs and CH-AgNPs are closely associated with flavonoids and terpenoids, suggesting the adsorption of these molecules on the nanoparticle surface. The presence of several functional groups can influence the reduction of metal ions into corresponding metal nanoparticles. Using TEM analysis, we observed the presence of polydisperse nanoparticles [45]. The TEM images clearly indicated a difference in average size, which were 32 and 50 nm for AgNPs and CH-AgNPs, respectively. The cytotoxicity of synthesized AgNPs and CH-AgNPs was screened in order to define the optimal concentrations for antimicrobial assays. The results reveal that CH-AgNPs did not show any relevant cytotoxicity against the Vero cell line for each tested concentration. We observed that CS-AgNPs at 312.5 ug/mL did not exhibit any cytotoxicity against L-929 fibroblast cells as has been previously reported [48].