Developing gold nanoparticle mycelial composites: Effect of nanoparticle surface functionality on Aspergillus niger viability and cell wall biochemistry

Functionalized biomaterials are important structures for wide array of applications due to their tunability, low cost of synthesis, and ease of use. The present study explores the quantitative deposition of coated Au nanoparticles (coating agents: cefaclor, glucose, citrate and NaBH₄) on the mycelium of A. niger as well as exploring the consequences of particle adsorption on the biochemistry (MTT assay, melanin, biofilm and glucan levels) of the fungus. Glucose and NaBH₄ coated Au nanoparticles were found to be denser on the mycelium as compared to cefaclor and citrate coated Au nanoparticles as evidenced by SEM-EDX and ICP-MS analysis. Although all fungal samples remained viable after growth in the presence of (10–20 µg/ml) coated gold nanoparticles stress indicators (production of melanin and biofilm formation) varied with the identity of the coated particles. Citrate coated was found to be highest stress inducing with maximum melanin and biofilm levels followed by cefaclor whereas glucose and NaBH₄ had the least effect on the fungus. This study suggests that though the fungus experiences stress under the effect of nanoparticles, it can still survive and grow in their presence to generate a mycelium with the deposited nanoparticles that could be used for various biosensing and environmental applications.