## 3 Results and Discussions
### Antiviral Activity  
To examine the inhibitory properties of gold nanostructured particles and PVP-gold nanostructured composites in the pre-entry stages of the influenza virus life cycle, we tested the tendency of these nanostructured particles to inhibit hemagglutination by the method referenced by [PERSON] and [PERSON] [42]. In a typical HA test, the comparison of the Influenza H9N2 virus' tendency to agglutinate chicken Red Blood Cells (RBCs) and the gold nano-structured particles' property of inhibiting virus agglutination was  
Figure 7: UV-VIS absorption spectra (a) Au-20 (solid line). (b) Au-PVP-20 (dotted line). studied. Our findings based on the observations on the HA protocol evidenced that gold nano-structured particles synthesized by the atmospheric pressure microplasma technique showed an inhibition of the H9N2 influenza virus activity of agglutinating Chicken RBCs, as has already been shown in Figure 3 in Section 2.2 (HA). In our present investigations, the concentration of nanostructured gold particles, which attenuated the infectivity of the H9N2 Influenza virus strain in the HA protocol, was evaluated to be 1.96 \(\upmu\)g/mL by using the relation [43]. \[Weight=Molarity\times Molecular\ Weight\times Volume \tag{2}\]  
Recently, porous gold nanoparticles synthesized by the surfactant-free emulsion method have been investigated against the H1N1, H3N2, and H9N2 influenza virus strains in the HA protocol using MDCK cells as a culture medium [9]. In their findings, the concentration of porous gold cabable to disable these multiple avian influenza viruses was 0.2 mg/mL. More recently, gold NPs synthesized by the chemical method using citrate as a reducing agent demonstrated a convincing inhibitory effect against the H1N1 virus in MDCK cells with medium-size gold nanoparticles [44]. Similar kinds of investigations were carried out by a previous research group with silver nanoparticles synthesized by biological roots. AgNPs with a concentration range of 12.5 \(\upmu\)g/mL to 100 \(\upmu\)g/mL exhibited a potential tendency of inhibiting H1N1 influenza A virus activity [6]. To study the inhibitory role of gold particles in the hybrid nanostructure, we investigated the antiviral activity of gold-PVP nanostructured composites. Quite interestingly, gold nanostructured in the composite form disabled the Avian virus activity of agglutination with more dilution, and hence less concentration, as compared to bare gold nanoparticles, as evidenced in Figure 3. We separately investigated the antiviral activities of Povidone (PVP) with the same concentration mixed with distilled water, where no antiviral activity was observed against AIV/H9N2 influenza viruses. This confirmed that the antiviral activity was only due to the presence of AuNPs in composites. Thus, we argue that the PVP attachment to the gold nanostructured particles boosted their antiviral activities. This strong inhibitory role of AuNPs in a hybrid nanostructure against the AIV/H9N2 influenza virus is due to the supporting role of PVP in Au-PVP nanostructured composites. PVP, due to its shape-directing, regulating, and controlling character [30,32], as evidenced by our morphological studies in the FESEM analysis, boosted the biocompatibility and, hence, improved the antiviral tendencies. The supporting antiviral behavior of other polymers, such as polyethylene glycol (PEG) and chitosan, with other metal nanostructured particles has also been investigated by previous research groups. Recently, ZnO NPs and ZnO-PEG NPs synthesized by the mechanical ball milling method [45] have been investigated to test their antiviral activity  
Figure 8: Optical band gap using the Tauc Plot for (a) Au-20 and (b) Au-PVP-20. against the H1N1 influenza virus in the MDCK cell as a culture medium. PEGylated ZnO NPs showed an enhanced antiviral activity compared to bare ZnO NPs [18]. In another research activity, small silver NPs in chitosan were found to possess a greater capability of inhibiting the H1N1 virus [19].