## 4 Antifungal Mechanism
### Raman Spectroscopy Analysis
#### 4.2.1 Raman Spectroscopy Analysis of PEI-AuNP@Van and Voriconazole- Treated _A. flavus_ Conidia  
The Raman spectra of the untreated PEI-AuNP@Van and voriconazole-treated conidia are shown in Figure 8, and the detailed spectrum assignments are shown in Table S1 (Supplementary File). The Raman spectrum of the untreated conidia of _A. flavus_ exhibited peaks at 335 cm\({}^{-1}\) (in-plane bending of CCO and torsion at COHO in galactomannan, an integral part of _A. flavus_ cell wall), 422 cm\({}^{-1}\) (in-plane bending of CCC, CCO, and OCO bonds), 559 cm\({}^{-1}\) (in-plane bending of CCC), 1059 cm\({}^{-1}\) (in-plane bending of COH/vibration of CO in ribose), 1250 cm\({}^{-1}\) (scissoring in CH\({}_{2}\)/amide III random), 1347 cm\({}^{-1}\) (D-fructose-6 phosphate), 1412 cm\({}^{-1}\) (wagging of C-H in myristic acid/galactomannan), 1526 cm\({}^{-1}\) (related to -C=C- stretching/vibration in the C-C bond of carotenoids), 1595 cm\({}^{-1}\) (NH\({}_{2}\) deformation/amide III protein), and 1712 cm\({}^{-1}\) (asymmetric vibration in CO\({}_{2}\) stretches) (Figure 8(ai)). These peaks were associated with a conidial cell wall composed of complex sugars and proteins such as mannoproteins, glucan, chitin, galactomannan, and ergosterol. The effect of voriconazole on the _A. flavus_ conidia was evaluated as a drug control. Voriconazole inhibits cytochrome P450-dependent 14\(\alpha\)-lanosterol demethylation, an important stage in fungal cell membrane ergosterol synthesis. This process ultimately destabilizes  
Figure 8: Raman spectrums of voriconazole and PEI-AuNP@Van-treated conidia of _A. flavus_ and _A. fumigatus_ along with an untreated control. (**ai**) Untreated conidia of _A. flavus_, (**ai**) treated with voriconazole, (**aiii**) treated with PEI-AuNP@Van, (**bi**) untreated conidia of _A. fumigatus_, (**bi**) treated with voriconazole, and (**biii**) treated with PEI-AuNP@Van. the cell membrane, leading to cellular fractures. The following peaks were observed in the Raman spectra (as shown in Figure 8(aiii)): 340, 412, 481, 534, 598, 734, 810, 916, 979, 1040, 1132, 1204, 1314, 1452, and 1610 cm\({}^{-1}\). The functional groups and chemical bonds of the spectral band were tentatively assigned as follows: plane bending of the OH in chitin (340 cm\({}^{-1}\)), amylopectin (412 cm\({}^{-1}\)), in-plane bending in the CCC skeletal mode/glucosyl ring deformation (534 cm\({}^{-1}\)), in-plane bending vibration of the pyranoid ring (598 cm\({}^{-1}\)), and thymidine (734 cm\({}^{-1}\)). In addition to the medium- and weak-intensity peaks, some firm peaks were observed (in contrast to the spectrum of untreated conidia) (Figure 8(aii)). These peaks can be assigned as follows: antisymmetric stretching in OPO phosphodiesterase (810 cm\({}^{-1}\)), indicating external cell wall damage; out-of-plane bending of the benzene ring in phenylalanine (916 cm\({}^{-1}\)); \(\beta\)(CCH) and \(\beta\)(CCO)/pyruvate (979 cm\({}^{-1}\)); C-C stretching in phospholipids/tetradoconic acid, carbohydrates (e.g., chi-tin), and C-N stretching (1040 cm\({}^{-1}\)); \(\
u\)(CO) mode in the COC (unsaturated fatty acids in lipids/galactomannan) (1132 cm\({}^{-1}\)); twisting in CH\({}_{2}\)/deformation mode in C-H of polysaccharide (1204 cm\({}^{-1}\)); vibration in CN/wagging in CH\({}_{2}\) of tyrosine (1314 cm\({}^{-1}\)); in-plane bending vibration of CH/wagging or deformation of CH\({}_{2}\)/in-plane bending vibration of OH (1452 cm\({}^{-1}\)); and in-plane bending of NH/amide III of protein (1610 cm\({}^{-1}\)). The Raman spectrum of the PEI-AuNP@Van-treated conidia was similar to that of the voriconazole-treated conidia, indicating the surface binding of functionalized nanoparticles and cell wall damage, which supports the fungistatic behavior of PEI-AuNP@Van. Figure 8(aiii) shows the Raman spectrum of the PEI-AuNP@Van-treated _A.