## 4 Discussion
Previous studies also evaluated the integration of TSNPs into BC supplemented with curcumin [53], as well as their integration into pure PCL and PLA using a solvent casting method, resulting in improved properties of BC and biocompatible materials [55]. BC/PHB blends with TSNPs (Figure 6a) showed significant decrease in microbial growth for both tested bacterial strains; this is attributed to the higher amount of absorbed TSNPs compared to the PCL and PLA blends (Figure 8). These results come in accordance with previous work on the incorporation of AgNPs into polymeric materials, where a higher antimicrobial response is exhibited on the materials that are able to maintain a higher rate of silver and Ag+ ions release [58]. Contrary to the previously reported study for evaluation of the antimicrobial activity of TSNPs incorporated into polymeric materials through solvent casting [55], the BC/PHB blend exhibited a higher antimicrobial response towards the Gram-negative strain under the examined conditions. Proteins are known to easily bind to gold and silver nanoparticles spontaneously. It occurs through ionic or hydrophobic interactions [59]. Nanoparticles may be pre-functionalized with specific proteins, which will determine which new protein will attach to the newly formed NP-protein system [60]. According to [PERSON] et al., line widths of the LSPR are reduced as the nanoplate volume increases, which improves sensitivity of the nanoplates. Furthermore, a blue shift in the LSPR can be observed (from 600 to 530 nm) upon silver seed volume adjustment, resulting in a size reduction of the nanoplates [50]. This can be advantageous for the use of TSNPs in biosensing, since it allows for a higher range in which shifts in the spectrum can be easily detected within the UV-Vis range (Figures 4 and 5). Unprotected TSNPs can be highly susceptible to degradation or etching by catalytic oxidation in the presence of chlorine or other reactive ions. This can lead to alterations of the geometry and structure of the TSNP, normally resulting in a substantial blue shift in their spectrum and impairing their LSPR properties [38]. Different coatings can be used to protect the TSNP structure; nonetheless, most coatings will also affect the plasmonic response of the nanoparticles. A method used by [38] proved to successfully coat TSNP edges with a layer of gold, providing the nanoparticles with protection from etching while allowing them to maintain their plasmonic response and refractive index sensitivity. Results of this study are in accordance to the results reported by the [38] deposition of a thin layer of gold in the triangular nanoplate edges at low Ag:Au ratios, successfully protecting the nanoplates without causing any structural damages associated with galvanic replacement (Figure 9). Moreover, no major changes in the nanoplates' optical properties occurred besides an enhancement of its optical sensitivity. The LSPR spectrum at pH 4 was redshifted by 10 nm upon Fn extension due to a higher refractive index surrounding the nanoplates. The presence of the compact protein strand on top of the nanoparticlesurface occupies a larger surface area; however, it does not bulge from the surface more than an elongated Fn strand, which can explain the shift in the spectrum. As presented in Figure 10, sucrose sensitivity assay confirmed that LSPR\({}_{\lambda\text{max}}\) of the spectra directly correlates to sucrose concentration [54,56]. In order to minimize any potential impact on the protein's conformational behavior, AuTSNPs were coated with PEG in order to avoid any direct interaction between the nanoplates' surface and the protein, thus reducing the likelihood of any influence on its conformation. Conformational changes of the protein were monitored by suspending the Fn-PEGAuTSNP in two phosphate buffers at pH 7.2 and pH 4.1 since Fn is known to change its structure upon pH variations (Figure 11).