# Biogenic Nanoparticles: Synthesis, Characterisation and Applications
## 2 Biogenic Synthesis of Nanoparticles
### Fungi  
Nanoparticle synthesis using fungi offers certain advantages in comparison to bacteria; thus, research in this area has seen an increasing interest over the last decade. Some of the advantages of mycelium include easy to scale up and downstream the process, economically feasible and ecologically friendly so they can cover a large surface [57]. Fungi contain enzymes in the cytoplasm and cell wall, which transform metal ions into nanoparticles [58]. The metal ions have a positive charge, which is attracted by the fungi and triggers the biosynthesis. Certain proteins are also induced by metal ions, and these hydrolyse the ions. Fungi are able to secrete high amounts of protein, thus increase nanoparticle synthesis. See Table 2 for some of the recent studies conducted on nanoparticles synthesis using fungi. There are an increased number of studies on silver nanoparticle synthesis using fungi, where their applications include antimicrobials, antioxidants, electronics and other biomedical applications. Despite the increased research into the microbial synthesis of gold nanoparticles, there are fewer studies on using fungi. Many of the studies have focused on silver and metal oxides. [PERSON] et al. synthesised gold nanoparticles using the fungus _Cladosporium cladosporioides_ obtained from seaweed _Sargassum wightii_[65]. The study examined the mechanism of nanoparticle synthesis and concluded that the NADPH-dependent reductase enzymes and the phenolic compounds were responsible for the synthesis of nanoparticles. \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Nanoparticle** & **Fungus** & **Application** & **Intra/Extra** & **Reference** \\ \hline Iron oxide & _Aspergillus niger_ BSC-\(1\) & Wastewater treatment & Extra & [59] \\ \hline Silver & _Aspergillus terreus_ & Antibacterial, anticancer & Extra & [60] \\ \hline Silver & _Cladosporium cladosporioides_ & Antioxidant, antimicrobial & Extra & [61] \\ \hline Copper & _Aspergillus niger_ & Antidiabetic and Antibacterial & Extra & [62] \\ \hline Selenium & _Marianunaa_ sp. HJ & Medicinal and electronics & Both & [63] \\ \hline Cobalt oxide & _Aspergillus nidulans_ & Energy storage & Extra & [64] \\ \hline Gold & _Cladosporium cladosporioides_ & Antioxidant, antimicrobial & Extra & [65] \\ \hline Gold & _Cladosporium oxysporum_ & Catalysis & Extra & [66] \\ \hline Platinum & _Fusarium oxysporum_ & Nano medicine & Extra & [58] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Examples of recent studies on nanoparticle synthesis using fungi. There are several experiments on using _Fusarium oxysporum_ fungus to synthesise nanoparticles in several experiments, including many studies on AgNPs. [PERSON] et al. synthesised AgNPs (10-15 nm in size) using fungus _Fusarium oxysporum_[67], and demonstrated promising antibacterial effects on _Escherichia coli_ and _Pseudomonas aeruginosa_. Other examples of nanoparticles produced using _F. oxysporum_ include copper [68], gold [69] and magnesium oxide [70]. Like other microbes, fungi produce nanoparticles intra/extracellular. Many of the nanoparticles produced within the organism are smaller than the ones that are created externally. The size limit is related to the nucleation of the particles within the species. Intracellular formation also offers many beneficial advantages. Depleted metals including platinum and copper must be eliminated from the environment to repair effects of environmental pollution. Fungi that produce intracellularly would be ideal to use because of the ease to extract the contamination from the sample [71]. Extracellular synthesis of NPs often has many applicable uses as the material is devoid of unwanted cellular constituents. Fungi are commonly known to be extracellular species since they secrete several secreted molecules to assist in the sequestration of nanoparticles. Extracellular synthesis provides greater simplicity and is relatively low cost. [PERSON] and [PERSON] found that _Cidasporium cladasporionides_ could be used in producing AgNPs in sizes ranging from 30 to 60 nm [61].