The AuNPs synthesized by mushroom extract yielded strong bands at 602, 1096, 1201, 1388, and 1636 cm-1 (Figure  3). These bands correspond to the amide I, II, and III bands of polypeptides/proteins, and are consistent with previous reports [51, 52]. As suggested by Sastry et al., the polypeptides found in the mushroom extracts served as capping agents in AuNPs, particularly glutathione, which is known to be produced by yeast cells [53]. Figure 3 FTIR spectra of AuNPs. It is well known that proteins can bind to AuNPs either through free amine groups or cysteine residues in the proteins [54]; therefore, stabilization of the AuNPs by surface-bound proteins is a possibility selleck chemicals llc in the case of AuNPs synthesized

by Ganoderma spp. Additionally, the bands at 1,636 cm-1 can be assigned to the vibrational modes of C=C double bonds of these molecules. The large peak between 1,500 and 1,700 cm-1 falls in the region of C=O stretching frequency, and the bands at 3,492 cm-1 correspond to carbonyl and hydroxyl functional groups in alcohols and phenol derivatives [11, 16, 55]. The FTIR results show that the surface capping of AuNPs

synthesized by the mushroom selleck kinase inhibitor extract is predominantly by proteins. Moreover, our results are consistent with those reported earlier for biosynthesized nanoparticles [11, 16, 50, 51, 55]. AuNP synthesis by the Ganoderma spp. extract was confirmed using EDS and spectra, as represented in Figure  4. The EDS profile shows a strong gold signal along with weak oxygen and carbon peaks, which may have originated from the biomolecules of the mushroom extract that bound to the AuNP surfaces. Figure 4 EDX spectra of AuNPs. Particle size analysis Further characterization

was carried out to determine the particle size distributions using dynamic light scattering (DLS) technique, which reveals the average hydrodynamic diameter of particles in a liquid suspension. These particle sizes are well within the range reported for photoluminescence of AuNPs [15]. Figure  5 shows the DLS analysis of mushroom ioxilan extract-mediated synthesis of AuNPs; the average size (20 nm) is within the expected range of particle sizes between 15 to 30 nm and is very similar to the size that was observed in TEM (20 nm). However, for particle sizes larger than 25 nm, the bandwidth increases with the increase in particle size [42], and nanoparticles such as gold and silver have also been shown to exhibit size-dependent optical properties. Husseiny et al. [28] observed the absorption spectra of AuNPs using three different strains of P. aeruginosa ATCC 90271, P. aeruginosa, and P. aeruginosa, and the maximum absorption peaks observed were 543, 540, and 531 nm corresponding to particle sizes of 30 ± 10, 25 ± 15, and 15 ± 5 nm, respectively. Figure 5 Size distribution analysis of AuNPs by DLS. The particle-size distribution revealed that the average particle size was 20 nm.