## 3 Results and Discussion
Comparing the results obtained from the AgNPs-S and AgNPs-C samples, it can be seen that nanoparticles synthesized with _Sargassum_ are more efficient in all the conditions evaluated. The percentage and the rate of degradation are higher when using the AgNPs-S sample. These results demonstrate the ability of nanoparticles synthesized with _Sargassum_ extracts to degrade organic dyes quickly and effectively. Recent advances have been made in green methods to synthesize antimicrobial systems based on nanomaterials [48; 49; 50], which aim to benefit the use of natural resources obtained from seaweed. In this regard, the antibacterial activity assays (AA) of AgNPs-S obtained from _Sargassum_ by the green method (Figure 9a,c) and their comparison with the conventional chemical method (Figure 9b,d) were evaluated after 1 and 24 h of interaction in liquid media against _S. aureus_ (Figure 9a,b) and _P. aeruginosa_ (Figure 9c,d). It can be  
Figure 8: Curves of methylene blue degradation at different concentrations using: (**a**) AgNPs-S, and (**b**) AgNPs-C; the nanoparticle concentration in both samples was 2.23 mg/mL. Figure 7: FTIR analysis of the _Sargassum_ extract and AgNPs-S.  
seen that the AA of AgNPs-S is higher than AgNPs-C in both microorganisms evaluated. This may be associated with the size of the nanoparticles and their stability in the PBS aqueous media. It has been reported [51] that the stability of AgNPs in a PBS buffer is not affected in the early stages of contact (1 and 24 h). In this work, no apparent color changes of AgNPs-S and AgNPs-C solutions in the PBS buffer were observed during the antibacterial test, indicating the stability of the nanoparticles. After 1 h of contact, the AA of AgNPs in contact with gram-positive bacteria (Figure 9a,b) is directly proportional to the number of nanoparticles. However, after 24 h of contact, all the evaluated AgNPs showed complete bacterial inhibition for different concentrations, demonstrating their potential antibacterial properties. High susceptibility of gram-negative _P. aeruginosa_ was determined in contact with AgNPs-S, with an AA of over 80% in all the concentrations evaluated. This behavior is associated with the differences in the bacterial wall composition of the microorganisms, where gram-negative bacteria have a higher susceptibility when in contact with metal nanoparticles by the complex formation between nanoparticles and peptidoglycan presenting on the surface of bacteria [52]. Finally, a statistical analysis, using one-way ANOVA followed by [PERSON]'s comparison test, was carried out. All experiments were carried out in triplicate. The data obtained from the statistical analysis are shown in the Table 1. The results presented are the average measurements (mean) of the runs (\(n=3\)) with standard deviation (SD) with a \(p>0.05\). Figure 9: The impact of AgNPs on the antibacterial activity (AA) percentage after 1 h (lighter) and 24 h (darker) of contact against gram-positive _S. aureus_ and gram-negative _P. aeruginosa_. **(a)** AgNPs-S against _S. aureus_, **(b)** AgNPs-C against _S. aureus_, **(c)** AgNPs-S against _P. aeruginosa_, and **(d)** AgNPs-C against _P. aeruginosa_. Error bars represent statistical differences at \(p\leq 0.05\) calculated by the Tukey–Kramer test. The impact of AgNPs on antibacterial activity obtained from different _Sargassum_ species has been reported previously [50,53]. In both studies, AA is attributed to the size of the nanoparticles (20-100 nm) and the qualitative inhibition zone against several microorganisms. According to our results, stable AgNPs ranging around ca. 20 nm can be produced from Mexican _Sargassum_ using a green method and result in obtaining high antibacterial properties at various nanoparticle concentrations. The antibacterial mechanisms of AgNPs have been attributed to the imbalance generated by the contact of nanoparticles and microorganisms, which produce irreversible changes in permeability, oxidative stress, and cell wall rupture [54, 55, 56]. According to [PERSON] et al.