Diversity of Mycogenic Oxide and Chalcogenide Nanoparticles: A Review

Oxide and chalcogenide nanoparticles have great potential for use in biomedicine, engineering, agriculture, environmental protection, and other research fields. The myco-synthesis of nanoparticles with fungal cultures, their metabolites, culture liquids, and mycelial and fruit body extracts is simple, cheap and environmentally friendly. The characteristics of nanoparticles, including their size, shape, homogeneity, stability, physical properties and biological activity, can be tuned by changing the myco-synthesis conditions. This review summarizes the data on the diversity of oxide and chalcogenide nanoparticles produced by various fungal species under different experimental conditions.


Introduction
Nanotechnology and nanomaterials science are rapidly developing fields, which contribute greatly to the development of modern technology and biomedicine. An important challenge is the development of simple, effective, and cheap methods of producing highly monodispersed, stable, and biocompatible nanoparticles (NPs) with the required chemical composition, shape, size, biological activity, and other properties. The recent increase in attention to environmental safety, natural resource exhaustibility, and human health safety has led to the increasing development of green NP-producing technologies by biosynthesis methods [1][2][3][4]. Owing to its being environmentally benign and less resource-intensive than other methods, the synthesis of nontoxic and biocompatible NPs by using living organisms and a variety of biological materials derived from them is a promising alternative to physical and chemical fabrication methods.
The ability to biosynthesize NPs has been found in many organisms, including animals, plants, bacteria, fungi, actinomycetes, algae, lichens, and viruses [5]. Among this diversity of biological objects used for green NP synthesis, a special place is occupied by fungi [6][7][8]. Fungal cultures produce a wide range of proteins with high enzymatic activity, and due to that they can convert metals and other elements into less toxic forms. This includes the formation of NPs, which then accumulate in large quantities within the mycelium and/or extracellularly. As a result, micro-and macro-mycetes from different taxonomic groups can be successfully used to produce NPs and nanomaterials on an industrial scale. The applications of fungi in myco-nano-synthesis are also highly versatile. NPs with different characteristics can be obtained either by growing fungal cultures on media with precursors or by incubating these precursors with mycelial bio-mass, culture liquid filtrates, extracts from vegetative mycelium, fruiting bodies and other morpho-structures, and purified proteins and other metabolites isolated from fungi [5]. In addition, the properties of biogenic NPs depend on medium composition, chemical composition and concentration of the precursor, incubation time, stirring rate, temperature, pH and other conditions. By  135-320 nm in length) [33] 4 Hexagonal, partially spherical (12.82-48.86 nm) CuO nanospheres (average size 32.4 nm) with high antimicrobial and antitumor activities were obtained with Aspergillus flavus culture liquid [27]. CuO NPs synthesized with Aspergillus terreus culture liquid showed anticancer activity in a concentration-dependent manner [30]. Other works showed that CuO nanospheres synthesized with A. terreus culture liquid had potent antioxidant and antimicrobial activities [28,29].
Honary et al. studied copper oxide NP synthesis by three Penicillium species [35]. Penicillium aurantiogriseum, Penicillium citrinum, and Penicillium waksmanii culture liquids mediated the fabrication of copper oxide nanospheres of various diameters. The effect of several parameters on the particle size and the polydispersity index for the synthesis of NPs under ambient conditions was also investigated. It was concluded that there is a direct correlation among pH value, precursor concentration, polydispersity index, and particle size. Spherical CuO NPs were also obtained with a Penicillium chrysogenum culture liquid filtrate with the aid of gamma rays at various doses [31]. The NPs were an active antibacterial agent against fungal and bacterial crop pathogens.
Copper oxide NPs of various sizes and shapes were synthesized with Pleurotus florida bio-mass and two different precursor salts [36]. Spherical, partially spherical, and oval particles (22.55-60.09 nm) were formed after the incubation with CuCl 2 , whereas the use of CuSO 4 resulted in hexagonal and partially spherical NPs (12.82-48.86 nm).
Spherical copper oxide NPs with a size of 10 to 190 nm and an average diameter of 110 nm were synthesized with a cell-free extract of Trichoderma asperellum [32]. These NPs induced photo-thermolysis of human lung cancer cells. CuO NPs with a rare morphology were obtained by Consolo and colleagues with a Trichoderma harzianum extract [33]. These particles were in the shape of elongated fibers 38-77 nm in width and 135-320 nm in length, and were inhibitory to fungal phytopathogens.
A Stereum hirsutum mycelial extract was found to be effective at synthesizing copper NPs [34]. Copper/copper oxide NP fabrication was studied under different pH conditions and in the presence of three copper salts (CuCl 2 , CuSO 4 , and Cu(NO 3 ) 2 ). Greater NP formation was shown with 5 mM CuCl 2 under alkaline conditions. The resulting NPs were mainly spherical and had sizes of 5 to 20 nm.

Myco-Synthesis of Iron Oxide Nanoparticles
Iron oxide is a mineral compound that exists in various polymorphic forms, the main of which are hematite (α-Fe 2 O 3 ), maghemite (γ-Fe 2 O 3 ), and magnetite (Fe 3 O 4 ) [15]. Mycogenic NPs of iron oxides (III) and (IV) obtained by different researchers with different biological objects and precursors differ greatly in both size and shape (Table 2). Spherical, cubic, irregular, octahedral, and flakelike iron oxide nanoparticles were obtained with mushroom cultures.  [38]. These NPs were effective biocatalysts for the decolorization and degradation of textile and tanning wastewater effluents in a dose-and time-dependent manner. Spherical hematite (α-Fe 2 O 3 ) NPs with a mean size of 207 nm, fabricated with a T. harzianum extract, enhanced T. harzianum biocontrol activity against the phytopathogen Sclerotinia sclerotiorum [37]. Small cubic Fe 2 O 3 NPs with an average size of 9 nm, active against Gram-positive and Gram-negative bacteria, were obtained with an Alternaria alternata mycelial extract [39]. Synthesis of Fe 2 O 3 nanospheres was also achieved with culture liquids of the manglicolous fungi T. asperellum, Phialemoniopsis ocularis, Fusarium incarnatum, and Penicillium pimiteouiense [41,42]. Their size varied depending on the species of fungus used for myco-synthesis. Manglicolous fungi-derived Fe 2 O 3 NPs were effective in removing Cr (VI) from synthetic wastewater [42].
The fungi Fusarium oxysporum and Verticillium sp. formed iron oxide NPs predominantly in the magnetite (Fe 3 O 4 ) phase [45]. Incubation of F. oxysporum bio-mass with precursors yielded quasi-spherical NPs, whereas Verticillium sp. produced cubo-octahedral particles. Superparamagnetic Fe 3 O 4 nanoflakes 20-40 nm in width were fabricated with an Aspergillus niger mycelial extract [43]. The NPs were successfully used for Cr (VI) removal from an aqueous solution, which provides an eco-friendly, sustainable, and effective route to heavy metal remediation and wastewater treatment. Fe 3 O 4 NPs obtained with lyophilized bio-mass of Fusarium solani were mostly cubic and spherical, with a mean size of 55.3-84.2 nm [46]. They had bactericidal activity against various bacteria, although it was weaker in comparison with that of silver NPs synthesized by F. solani in the same study. Mousa et al. fabricated Fe 3 O 4 nanospheres with A. terreus culture liquid and deter-mined optimal conditions for the maximal NP yield [28,29]. These NPs showed promising antioxidant activity and a potent effect against several plant and human pathogens.
Abdeen et al. used a combined method to produce magnetic Fe 3 O 4 NPs [40]. A. niger bio-mass was used for the decomposition of FeSO 4 and FeCl 3 to FeS and Fe 2 O 3 , respectively. Then, the FeS and Fe 2 O 3 NPs were used to produce pure iron and Fe 3 O 4 nanospheres by a physical method.
Several researchers have used fungal cultures to obtain iron oxide nanocomposite materials with enhanced properties. Fe 3 O 4 NPs with spherical morphology and size varying from 5 to 22 nm were myco-synthesized with an Aspergillus tamarii culture filtrate [44]. The conditions for NP production were optimized, including incubation period, stirring speed and time, temperature, and pH. The resulting Fe 3 O 4 NPs were impregnated into chitosan beads to produce magnetic nanocomposite for textile wastewater treatment. The modified beads showed a good removal capability with improved stability and regeneration, as compared with the control chitosan beads. Another iron oxide NP-based biomaterial was obtained with a spent substrate for Agrocybe cylindracea [49]. The Fe 3 O 4 NP-coated biomaterial described in that study was effective at Cr (VI) removal from wastewater. Ince et al. developed fungal bio-nanocomposite Fe 3 O 4 materials effective at metal removal from drinks and wastewater. They synthesized chitosan-coated magnetic Fe 3 O 4 NPs with an Agaricus campestris fruit body extract [50] and alginate-coated superparamagnetic Fe 3 O 4 NPs with an Amanita vaginata fruit body extract [51]. Ultrasmall iron oxide NPs were fabricated with an Amanita muscaria fruit body extract [47]. Using these NPs, Ivashchenko and colleagues developed a gel formulation for local anticancer therapy, containing A. muscaria-derived iron oxide and silver NPs.

Titanium Oxide NPs
Titanium oxide (TiO 2 ) NPs are yet another important NPs with outstanding properties. Three mineral forms of TiO 2 that are known to occur naturally are anatase, rutile, and brookite. TiO 2 NPs have a wide range of applications owing to their chemical stability, low toxicity, biocompatibility, and good corrosion resistance [52]. Thanks to their high antibacterial, antifungal, antiviral, and anticancer activity, they are important tools in diagnostics, therapeutics, and drug delivery [53]. Various micro-and macro-mycetes can produce TiO 2 NPs with their living cultures, extracts, bio-mass, and even spores (Table 3). The ability to synthesize TiO 2 NPs was found in various Aspergillus species. Spherical and oval 62-74-nm TiO 2 NPs with antibacterial properties were fabricated with A. flavus bio-mass [55]. TiO 2 NPs of 12-15 nm synthesized with an A. flavus mycelial extract demonstrated a strong growth-enhancing effect on mung beans and thus can be used as a plant nutrient fertilizer [56]. TiO 2 nanospheres (73.58-106.9 nm) generated with an A. niger extract were found a potent mosquito larvicidal agent [57]. TiO 2 NPs produced with an Aspergillus tubingensis mycelial extract were cubic and pentameric, with a size of 1.5-30 nm [58]. Bansal et al. showed that spherical titania particles (6-13 nm) can be produced with F. oxysporum bio-mass and K 2 TiF 6 as a precursor [61]. Al-Timini and Sermon showed that NPs can be synthesized on the surfaces of Portobello mushroom spores [54]. Using this approach, they prepared TiO x , Ag-TiO x , and Au-TiO x NPs. Nanohybrids of these NPs with mushroom spores showed antibacterial and/or antifungal activity.
Small mesoporous TiO 2 NPs (10-12 nm) with outstanding photocatalytic performance were formed when Sachharomyces cerevisae yeast cells were cultivated with TiCl 4 [67]. By incubating an S. cerevisae culture with TiO(OH) 2 , nanospheres with an average size of 12.57 nm were fabricated [66]. In another study, baker's yeast was incubated with TiCl 3 to produce anatase TiO 2 nanospheres (average size 6.7 nm) [68]. These mycogenic NPs had prominent antibacterial and antifungal properties and were highly photocatalytic in comparison to commercially available 21-nm TiO 2 NPs. TiO 2 NPs obtained with Trichoderma viride culture liquid were spherical, with a size of 60-86.67 nm [70]. Their larvicidal, antifeedant and pupicidal activities against the cultivated crop pest Helicoverpa armigera can help in eco-friendly pest management. With a Tricoderma citrinoviride mycelial extract, irregular, triangular, pentagonal, spherical, and rod-shaped TiO 2 NPs were synthesized, whose sizes ranged between 10 and 400 nm [69]. They showed excellent antioxidant potential and antibacterial activity against extremely drug-resistant Pseudomonas aeruginosa clinical isolates.

Myco-Synthesis of Zinc Oxide Nanoparticles
Zinc oxide (ZnO) NPs have caught the attention of researchers owing to their extensive biological properties, including antibacterial, antifungal, anticancer, anti-inflammatory, antidiabetic, antioxidant, antiviral, wound healing, and cardioprotective activity [71,72]. Their exceptional optical, electrical, and physiochemical properties make ZnO NPs an excellent option for electronics, optoelectronics, bioimaging, biosensors, drug and gene delivery [72,73]. To date, these NPs have been the most commonly studied of all mycogenic oxide NPs (Table 4). Mycogenic ZnO NPs are mostly spherical or hexagonal. The formation of ZnO nanospheres with sizes ranging between 13 and 15 nm was studied by using an Acremonium potronii mycelial extract [74]. The obtained ZnO NPs showed high photocatalytic activity for the degradation of methylene blue dye. ZnO nanospheres with an average size of 14.48 nm were fabricated with an aqueous extract of Agarius bisporus as a reducing agent [75]. These NPs were effective inhibitors of microbially influenced corrosion.
The correlation between the zinc tolerance of soil fungi and their potential for the synthesis of ZnO NPs was examined with 19 fungal isolates from the rhizo-spheric soil of plants naturally growing at a zinc mine area [76]. The Aspergillus aeneus isolate had a high zinc tolerance and potential for the extracellular synthesis of ZnO NPs. The result was the synthesis of spherical NPs (100-140 nm) coated with proteins, which served as stabilizers.
Spherical 60-80-nm ZnO NPs synthesized with Aspergillus fumigatus culture liquid were an effective antimicrobial agent against Gram-negative and Gram-positive bacteria [77]. An A. fumigatus mycelial extract induced the formation of oblate spherical and hexagonal ZnO NPs (1.2-6.8 nm) with plant-growth-promoting properties [78]. Hexagonal ZnO NPs with an average size of 66 nm were synthesized by using crushed powder of A. niger [80]. Protein-capped ZnO nanospheres with a particle size of about 10-45 nm, possessing antibacterial activity, were obtained with an A. terreus mycelial extract [82]. Incubation of A. terreus culture liquid with ZnSO 4 yielded spherical ZnO NPs (28-63 nm) [81]. ZnO NPs with antioxidant and antimicrobial activities were also synthesized with the culture liquid of A. terreus and with ZnC 4 H 6 O 4 as a precursor [28,29].
Aqueous mycelial extracts of two fungi, A. niger and Fusarium keratoplasticum, were used to prepare ZnO NPs of different shapes [79]. A. niger synthesized ZnO nanorods (8-38 nm), and F. keratoplasticum synthesized hexagonal NPs (10-42 nm). The shape of the NPs greatly affected their multifunctional properties. Nanorods showed an enhanced antibacterial activity against pathogenic bacteria and a greater UV-protection index, as compared with hexagonal ZnO NPs. Treatment of textile fabrics with a safe dose of green ZnO NPs was potentially active against pathogenic bacteria and improved UV protection, as compared with untreated fabrics.
ZnO NPs obtained with an extract from the zinc-tolerant endophytic fungus Cochliobolus geniculatus were polydisperse, non-agglomerated quasi-spherical particles with a narrow range distribution (2-6 nm) [83]. Extracellular proteins involved in the synthesis of ZnO NPs and their capping were also characterized.
A fruit body extract from the medicinal mushroom Cordyceps militaris mediated the fabrication of ZnO NPs with an average size of 1.83 nm and with high antimicrobial, antidiabetic, and antioxidant potential [84]. ZnO NPs were also synthesized with a Daedalea sp. extract [85]. The NPs were irregularly shaped, had an average size of 14.58 nm, and showed a strong antibacterial and antifungal effect. A Lentinula edodes extract was used as a reducing agent involved in the myco-synthesis of ZnO NPs, coated with chitosan, which functions as a stabilizer [86]. The NPs were cubic and hexagonal and had dye-degrading and antibacterial properties.
Quasi-spherical ZnO NPs (16-78 nm) synthesized with a Periconium sp. mycelial extract showed good antioxidant properties, as well as excellent antimicrobial effect against fungi, Gram-positive and Gram-negative bacteria [87]. The ability of the yeast Pichia kudriavzevii to synthesize ZnO NPs was explored with a fungal extract [88]. The resulting NPs were found to have a hexagonal wurtzite structure with an average crystallite size of 10-61 nm, and displayed antioxidant and antibacterial properties. The time of the reaction was found to play a critical part in the size, shape, and distribution of NPs. The ability to produce ZnO NPs was also reported for Pichia fermentans culture liquid [93].
ZnO NPs synthesized with a P. djamor fruit body extract were rod-and cluster-shaped with an average size of 70-80 nm and showed a wide range of biological activities, including larvicidal, antibacterial, antioxidant, and anticancer properties [64]. Semispherical ZnO NPs fabricated with P. florida bio-mass varied in size, depending on the precursors [36]. With ZnCl 2 , their size was 21.27-118.36 nm, and with ZnSO 4 , it was 9.36-58.13 nm. In another work, the culture liquid of Pleurotus floridanus was used for the synthesis of ZnO nanospheres, and the process parameters were optimized [89]. A Pleurotus ostreatus fruit body extract was used to synthesize small (average size of 7.50 nm), spherical, highly stable, agglomerated ZnO NPs with antibacterial and anticancer properties [90].
ZnO NPs with an unusual morphology (fan-and bouquetlike structures 27-40 nm in width and 134-200 nm in length) were fabricated with a T. harzianum mycelial extract [33]. In another study, ZnO nanospheres (average size of 30.34 nm) with antioxidant and antibacterial properties were produced with an extract from T. harzianum mycelium [91]. T. viride culture liquid was also used to synthesize ZnO NPs [92]. These NPs were hexagonal, had an average particle size of about 63.3 nm, and possessed dose-dependent antioxidant activity and appreciable antimicrobial effect against multidrug-resistant microorganisms.

Myco-Synthesis of Nanoparticles of Other Elements
Fungal cultures can form oxides of many elements other than copper, iron, titanium, and zinc. These include magnesium, manganese, cobalt, nickel, zirconium, selenium, tellurium, silicon, cerium, silver, aluminium, bismuth, antimony, gadolinium, and ruthenium ( Table 5). Many of these elements remain barely explored in terms of NP myco-synthesis, and their formation by fungal cultures has so far been described only in a few reports. Several research groups were able to prepare mycogenic NPs of cerium oxide. CeO 2 nanospheres (5-20 nm) have been successfully obtained with an A. niger culture liquid filtrate [97]. The NPs showed a high antibacterial activity against pathogenic bacteria and larvicidal and pupicidal activity against mosquito vectors. Spherical 20-30-nm CeO 2 NPs obtained with F. solani culture liquid showed a good antibacterial and antibiofilm activity against Psedomonas aeriginosa, Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus [99].
Electrochemical analysis shows that mycogenic NPs can be used in applications such as sensors, batteries, and supercapacitors. The bio-mass of the fungus Humicola sp. was able to extracellularly form highly stable, water-dispersible, and highly fluorescent CeO 2 NPs [100]. These NPs were spherical, were 12-20 nm in diameter, and were naturally capped by proteins secreted by the fungus. Komal et al. synthesized morphologically different CeO 2 NPs with mycelial extracts from two fungi, A. terreus and Talaromyces prupureogenus [98]. Pure CeO 2 NPs synthesized with A. terreus were spherical, with an average size of 28.5 nm. CeO 2 NPs formed by T. pupureogenus had a unique nano-sponge morphology and an average size of 21.4 nm. The nano-sponges were more active against Candida albicans than were spherical CeO 2 NPs.
Cobalt oxide NPs have so far been synthesized with several Aspergillus species. A cellfree mycelial extract of Aspergillus brasiliensis was used to make quasi-spherical monodispersed Co 3 O 4 NPs of 20-27-nm [101]. The NPs have excellent magnetic properties and show good antimicrobial activity against pathogenic microorganisms. Four fungi were tested by Vijayanandan and colleagues to find a fungus suitable for the synthesis of cobalt oxide NPs [102]. Fluorescent Co 3 O 4 nanospheres capped with sulfur-bearing proteins were successfully synthesized with Aspergillus nidulans bio-mass. Optimization of the fermentation conditions for the enhanced production of Co 3 O 4 and other NPs with A. terreus culture liquid was studied by El-Sayed et al. [29]. Al 2 O 3 nano-speres with an average size of 30 nm were synthesized with a Colletotrichum sp. mycelial extract [94]. Al 2 O 3 NPs showed a strong antimicrobial activity against food-borne pathogens. Nano-functionalized oil was formulated by combining essential oils from the leaves of Eucalyptus globulus and Citrus medica with NPs. The combination showed higher antimicrobial activity than did NPs and the essential oils tested separately. Moreover, the activity of commercially available antibiotics increased in combination with mycogenic Al 2 O 3 NPs.
Recently, an effective method was described for the fungi-mediated production of fluorescent ruthenium oxide (RuO 2 ) QDs by F. oxysporum bio-mass [112]. The biosynthesis was conducted under ambient pressure at room temperature, which offers advantages over the previously used chemical and physical methods for RuO 2 synthesis, requiring highly elevated temperature and pressure. The QDs were monodisperse, non-flocculating, protein capped, and highly stable even months after synthesis. Biosynthesis of antimony trioxide (Sb 2 O 3 ) NPs mediated by S. cerevisiae was reported by Jha et al. [113].
MgO NPs synthesized with A. niger culture liquid were nanospheres of 40-95 nm [105]. Their antibacterial activity was stronger against Gram-positive bacteria then it was against Gram-negative ones. Small MgO nanospheres with an average size of 5.8 nm were prepared with an A. tubingensis mycelial extract [106]. Larger NPs, of 45.12-95.37 nm, were synthesized with T. viride culture liquid and were found to be an effective antibacterial agent [107]. A white button mushroom extract was used to make MgO NPs with an average size of 29.6-38.6 nm [104]. The researchers showed that 16.5-and 15-nm MgO NPs may promote root development in peanut plants.
Quasi-spherical Mn 5 O 8 NPs of 8-13 nm were obtained with F. oxysporum bio-mass [109]. These particles were highly stable, water dispersible, and naturally capped by the fungussecreted proteins. The Mn-oxidizing fungus Cladosporium halotolerans with a strong ability to remove and oxidize Mn (II) was studied by Wang et al. [108]. The C. halotolerans culture formed particles with a needlelike or wrinkle-like morphology in the cross section, 2-6 nm in diameter, and 0.1-1 µm in length. The obtained nanowires showed excellent Cd (II) adsorption and had potential anti-pollutant application prospects.
NiO NP synthesis with A. terreus culture liquid was optimized for higher NP yield by El-Sayed et al. [29]. The dead bio-mass of the fungus Hypocrea lixii was also successfully used to convert nickel ions into NiO NPs in aqueous solution [111]. H. lixii-mediated NPs were predominantly spherical and were formed extra-and intracellularly. The NPs formed inside the fungal cells were smaller than those produced extracellularly. The average particle sizes were 3.8 nm for extracellular NPs and 1.25 nm for intracellular NPs. The dead bio-mass of Aspergillus aculeatus synthesized spherical NiO NPs in film form [110]. The NPs had a size of about 5.89 nm and were involved in a protein matrix, which probably permitted their organization in film form.
Liang et al. studied the formation of Se-and Te-containing NPs by several fungal species during growth on Se-and Te-containing media [114]. Besides the formation of elementary selenium, selenium oxide was also found after T. harzianum had been grown with selenite. Tellurium oxide was detected in the particles generated by T. harzianum and Mortierella humilis grown with tellurite.

Myco-Synthesis of Chalcogenide Nanoparticles
Chalcogens are chemical elements from group 16 of the periodic table: oxygen, sulfur, selenium, tellurium, polonium, and livemorioum. Oxygen is often treated separately from the other group 16 elements, or even excluded from the scope of the term "chalcogen", owing to its very different chemical behavior from the other chalcogens [120]. Chemical compounds consisting of at least one chalcogen anion and at least one more electropositive element are called chalcogenides. The three most important groups of chalcogenides are sulfides, selenides, and tellurides. In recent years, fungi-assisted synthesis of chalcogenide NPs and nanomaterials has become of interest.

Myco-Synthesis of Sulfide Nanoparticles
Fungi-mediated synthesized sulfide NPs are the most commonly studied of all chalcogenides. One of the most important types of semiconductor nanomaterials with a wide band gap and with stability than that of the other chalcogenide NPs, sulfide NPs are more suitable for industrial applications, including high temperature operations, high voltage optoelectronic devices, and as high efficiency electric energy transformers and generators [13].
According to the data so far, fungal cultures can synthesize cadmium, zinc, and lead sulfide NPs. Several researchers have also found that some fungi can produce gold, silver, and copper sulfide NPs (Table 6).  Among mycogenic sulfide NPs, the best studied are cadmium sulfide (CdS) NPs. These were first obtained with the use of fungal cultures in the 1980s, when Dameron and colleagues synthesized quantum CdS nano-crystallites with the yeasts Candida glabrata and Schizosaccharomyces pombe [154]. Short chelating peptides of general structure (γ-Glu-Cys) n -Gly control the nucleation and growth of CdS crystallites to peptide-capped intracellular particles of diameter 20 Å (2 nm). Both yeasts also produce larger, extracellular CdS NPs with an uncharacterized coating, 29 Å (2.9 nm) in diameter. Later, the S. pombemediated synthesis of CdS NPs was studied by Williams et al. [133]. It was found that intracellular CdS quantum semiconductor crystallites approximately 1.8 nm in diameter can be selectively released from S. pombe cells by freezing-thawing. S. pombe and C. glabrata also formed CdS NPs in their cytoplasm when yeasts were grown in a fed-batch process at high Cd concentrations [124].
A. niger bio-mass challenged with precursors produced highly stable poly-dispersed CdS nanospheres with a size ranging from 2.7 to 7.5 nm; these particles were found to have antimicrobial and anticancer abilities [123]. The bio-mass of F. oxysporum produced extracellular biocompatible CdS QDs from sulfur waste and Cd(NO 3 ) 2 [126]. These QDs were circular with a diameter of about 6 nm and had a wurtzite crystalline structure. F. oxysporum incubated with CdSO 4 formed CdS NPs in the size range 5-20 nm [125]. Fusarium sp. bio-mass, after being exposed to a CdSO 4 solution, formed spherical CdS NPs with an average particle size of 80 to 120 nm and agglomerates with a size of 350 to 390 nm [127]. CdS QDs synthesized by the fungus Phanerochaete chrysosporium had an average size of 2.56 nm [128]. The synthesis of cysteine and proteins was found to play an important part in the formation and stabilization of CdS QDs. CdS QDs with an average size of 8.8 nm formed by Rhizopus stolonifer mycelial bio-mass [130]. Luminescent CdS QDs synthesized with P. ostreatus mycelium were spherical, were predominantly 4 to 5 nm in size [129], and had anticancer properties [155].
S. cerevisiae-mediated synthesis of CdS NPs was reported by Prasad and Jha [131]. The NPs were almost spherical, with an average size of 3.57 nm. Another study described the production of CdS nanospheres (average size of 2 nm) with S. cerevisiae bio-mass [132]. Cds NPs were formed intracellularly by an S. pombe strain [134]. The NPs had a wurtzite (Cd 16 S 20 )-type structure and were mostly in the size range 1-1.5 nm. By using S. pombemediated CdS NPs, a polymer/nanoparticle diode with a low operating voltage and a high forward current was fabricated. Wurtzite CdS NPs of 3-5 nm were synthesized with a Termitomyces heimii mushroom extract [135]. The volume of extract used for the synthesis affected the particle size. A Trametes versicolor culture synthesized spherical extracellular CdS QDs with an average size of 6 nm [136]. T. harzianum bio-mass formed spherical CdS NPs (3-8 nm) with photocatalytic activity, which was determined upon degradation of methylene blue dye [137]. CdS nanospheres with a size range of about 6-15 nm were formed with the yeast Trichosporon jirovecii [138].
Gold sulfide (Au 2 S) nanospheres with a size of 20-30 nm were synthesized with Humicola sp mycelium [122]. The prepared particles were shown to be nontoxic to humans and, therefore, can be proposed for use in leishmania treatment, nano-diagnostics, and drug carrier applications.
Copper sulfide (CuS) NPs were synthesized with F. oxysporum mycelium and with CuSO 4 as a precursor [139]. The formed spherical particles with a size of 2-5 nm were enclosed in spherical peptide shells about 20 nm in diameter. Later, the same authors obtained CuS NPs by incubating F. oxysporum mycelium with copper mine wastewater [140]. The results showed that the produced NPs had a covelite composition and that their size was about 10-40 nm.
Lead sulfide (PbS) NPs with quantum semiconductor properties were first synthesized with Torulopsis sp. [144]. Seshadri et al. reported the intracellular synthesis of stable PbS NPs by the marine yeast Rhodosporidium diobovatum [142]. The NPs, of 2-5 nm, were spherical and well dispersed. S. cerevisiae produced PbS nanospheres 0.667-6.95 nm in size [143]. Synthesis of PbS NPs with A. flavus yielded 35-100-nm particles that had the potential for the detection of arsenic in aqueous solution [141].
ZnS NPs was synthesized with an extract of the edible mushroom A. bisporus [145]. The agglomeration and size of the NPs decreased along with increasing the A. bisporus extract volume used for the myco-synthesis. With a high extract volume, the NPs were almost spherical and the average particle size varied from 2.1 to 3.5 nm. The same authors also synthesized ZnS NPs with a P. ostreatus fruit body extract [152]. In that case, the agglomeration of the particles and their size also decreased as the amount of the mushroom extract was increased. With the use of a P. ostreatus extract, a large quantity of spherical NPs of 4.04 to 2.30 nm was formed. The authors attribute the smaller size of the ZnS NPs obtained with A. bisporus to the higher protein content of this mushroom's fruit bodies [145].
Spherical ZnS QDs (average size of 18 nm) were obtained with A. flavus bio-mass [146,147]. Later, the same researchers utilized A. flavus bio-mass to synthesize gadolinium-doped ZnS (ZnS:Gd) [148]. The fluorescence intensity of the biogenic ZnS:Gd NPs increased in comparison to ZnS NPs, which makes them a reliable fluorescent sensing tool. Jacob and colleagues studied ZnS QD production with bio-mass of two micro-mycetes, Aspergillus sp. and Penicillium sp. In both cases, the mycogenic NPs were spherical and their average size was 11.08 nm for Aspergillus [149] and 6.3 nm for Penicillium [151]. Aspergillus-mediated ZnS QDs showed excellent antibacterial and dye-degrading activities. The QDs synthesized by Penicillium sp. were effective in the photodegradation of methylene blue dye. F. oxysporum mycelial bio-mass was used to synthesize spherical ZnS NPs with an mean size of 42 nm [150]. S. cerevisiae bio-mass formed 30-40-nm ZnS nanospheres [153].

Myco-Synthesis of Selenide Nanoparticles
Selenides are another important class of chalcogenide semiconductors. Their potential applications include photocatalysis, bioimaging and biolabeling, and nanomedicine [156]. Mycogenic selenide NPs obtained by bio-nanotechnologists so far include cadmium, lead, silver, gold, indium, and neodymium selenides. To date, they have been obtained mostly with fungal bio-mass or living cultures (Table 7). The most widely studied mycogenic selenide NPs are cadmium selenide (CdSe) NPs, and their synthesis with yeasts is the best studied so far [159,[162][163][164][165]170]. Various conditions for CdSe QD synthesis with S. cerevisiae were investigated and optimized to obtain particles with a controllable size and with tunable fluorescence emission [163]. Brooks and Lefebvre examined the ability of S. cerevisiae sequentially treated with sodium selenite and cadmium chloride to synthesize CdSe QDs in the cytoplasm [164]. They optimized biosynthesis conditions for the highest yield of QDs, and through the optimized method they obtained fluorescent QDs with an average particle diameter of 2.8 nm. Shao et al. studied Se precursors and Se metabolic flux in the synthesis of CdSe QDs in S. cerevisiae and improved their ability to synthesize CdSe QDs through gene modification [165]. They identified selenocysteine as the primary Se precursor in the intracellular biosynthesis of CdSe QDs. Further studies showed that the seleno-methionine-to-selenocysteine pathway regulates CdSe QD biosynthesis. Seleno-methionine synthesis was enhanced by overexpression of the MET6 gene, and the yield of CdSe QDs in the engineered cells was increased.
CdSe QDs (average size of 4.38 nm) were also fabricated in vivo with Candida utilis [159]. Higher Cd and lower Se contents favored the formation of QDs with a higher fluorescence intensity and better stability, implying a possibility of tuning the fluorescence properties of these QDs. Candida-mediated CdSe QDs were directly used in live-cell imaging without further surface modification. Cao et al. synthesized CdSe QDs with bio-mass of the yeast Rhodotorula mucilaginosa [162]. The synthesis was regulated by changing the concentration of precursors and the pH of the medium, and it was found that the concentration of cadmium ions, rather than that of selenium ions, determined the synthesis of CdSe QDs. The synthesized CdSe QDs had a narrow size distribution (3.2 ± 0.4 nm) and great photocatalytic activity toward malachite green dye under ultraviolet and visible light.
Besides various yeasts, other micro-mycetes are also able to form CdSe QDs. F. oxysporum bio-mass was used for the synthesis of highly stable semiconductor CdSe QDs (average size of about 11 nm) with a broad fluorescent spectrum [160]. Helminthosporum solani mycelial bio-mass induced the synthesis of small monodisperse luminescent CdSe QDs with a mean size of 5.5 nm [161]. Most of these NPs were spherical, and a few cubelike particles were present. Ag 2 Se QDs with a uniform size of 3.9 nm were obtained with living S. cerevisiae yeast [157]. The authors showed that selenocysteine was the primary Se precursor, and the ability to synthesize Ag 2 Se QDs was improved by the construction of engineering strains. Ag 2 Se synthesized with S. cerevisiae were weakly toxic and could be used for in vivo imaging.
AuSe nanospheres with an average particle size of 52 nm were synthesized by incubating F. oxysporum mycelium with SeCl 4 and HAuCl 4 [158]. First, SeCl 4 was reduced into Se NPs, and then these NPs were reacted with HAuCl 4 and formed AuSe NPs. In the absence of an Se intermediate, HAuCl 4 was reduced to Au NPs by fungal biomolecules. AuSe NPs effectively inhibited conidiophores, conidiation, and sporulation in the fungus A. niger.
Sinharoy and Lens studied the simultaneous removal of indium, selenium, and tellurium by A. niger from media by using different precursor concentrations [166]. Characterization of the fungal bio-mass showed accumulation mostly of elementary Se NPs within mycelial pellets, and, in addition, the formation of indium selenide (InSe) during their simultaneous removal. The NPs were <10 nm in size. Biomimetic fabrication of neodymium selenide (Nd 2 Se 3 ) NPs was conducted with a nitrate-dependent reductase from the fungus F. oxysporum as a reducing agent and with a synthetic peptide as a capping molecule [167]. Nd 2 Se 3 NPs were spherical, with an average size of 18 nm.
Fluorescent, semiconductor lead selenide (PbSe) quantum rods were synthesized with the Pb-and Se-tolerant marine fungus A. terreus [168]. Semiconductor PbSe NPs were also obtained with Trichoderma sp. bio-mass [169]. The optimal ratio between precursors was 1:1 mM SeO 2 :Pb(NO 3 ) 2 . The NPs were 10-30-nm cubic face-centered protein-capped particles, which showed a strong antioxidant activity and photocatalytic activity in degrading rhodamine B dye.

Myco-Synthesis of Telluride Nanoparticles
Yet another group of chalcogenides consists of the tellurides, which also show outstanding properties and potential applications in optical, electronic, thermoelectrical, energy storing, catalytic, magnetic, and biological fields [171,172]. Their antimicrobial and anticancer properties allow them to be used in nanomedicine [173]. The fungal synthesis of NPs of these compounds has been poorly studied and has been described by only a few researchers (Table 8). The ability to fabricate CdTe NPs has been found in several species of micro-mycetes. Highly fluorescent biocompatible CdTe QDs capped with proteins were synthesized with S. cerevisiae cells [175]. The synthesized QDs, obtained after 8 days of incubation, were well-dispersed particles with a uniform diameter of about 3.6 nm. When the incubation time was shortened to 2 days, the resulting CdTe QDs were smaller (about 2.2 nm). The CdTe QDs obtained with F. oxysporum mycelial bio-mass were also highly fluorescent and were stable and biocompatible [174]. These NPs were spherical, were 15-20 nm in diameter, and showed antibacterial activity against Gram-positive and Gram-negative bacteria. Biocompatible CdTe QDs with an average size of 7.6 nm were also obtained with R. stolonifer [133]. The study of the simultaneous removal of indium, selenium, and tellurium by A. niger from media showed accumulation of elementary Te NPs and indium telluride NPs within mycelial pellets [166].

Prospects of Mycogenic Oxide and Chalcogenide Nanoparticles Practical Application
Many researchers have identified a variety of activities in mycogenic oxide and chalcogenide NPs, determining their great potential for further practical employment in biomedicine, optics, agriculture, pollution control, and other fields of application ( Figure 1).  One of the most important fields for use of these NPs is biomedicine. As described above, various biomedical activities were found in many oxide and chalcogenide NPs produced with fungi. Antibacterial, antifungal, antioxidant, anticancer, antidiabetic, and antileishmanial properties offer great prospects for their use in the treatment and prevention of various diseases. The larvicidal and pupicidal activities against human disease vectors, found in mycogenic TiO2 [57], ZnO [64] and CeO2 [97] NPs allow them to be used as agents of infection control. The prospects for fungi-derived NP use in agriculture are opened by CuO [33], ZnO [33] and Fe2O3 [37] NPs' activity against bacterial and fungal crop pathogens and by TiO2 NPs effect against insect pests [70]. Plant growth-promoting properties of TiO2 [56] and MgO [104] myco-synthesized NPs enable their use as nano-fertilizers. One of the most important fields for use of these NPs is biomedicine. As described above, various biomedical activities were found in many oxide and chalcogenide NPs produced with fungi. Antibacterial, antifungal, antioxidant, anticancer, antidiabetic, and antileishmanial properties offer great prospects for their use in the treatment and prevention of various diseases. The larvicidal and pupicidal activities against human disease vectors, found in mycogenic TiO 2 [57], ZnO [64] and CeO 2 [97] NPs allow them to be used as agents of infection control. The prospects for fungi-derived NP use in agriculture are opened by CuO [33], ZnO [33] and Fe 2 O 3 [37] NPs' activity against bacterial and fungal crop pathogens and by TiO 2 NPs effect against insect pests [70]. Plant growth-promoting properties of TiO 2 [56] and MgO [104] myco-synthesized NPs enable their use as nano-fertilizers.
Another important characteristic of NPs is their photocatalytic properties, which determine their ability to degrade toxic dyes [176]. Dye-degrading ability was found in ZnO [74,86], ZnS [149,151], CdS [137], CdSe [162] and PbSe [169] mycogenic NPs. In addition, some fungi-derived NPs, such as Fe 2 O 3 [42] and Fe 3 O 4 [43], were found to be effective for metal ions removal. These properties allow the use of mycogenic oxide and chalcogenide NPs in the bioremediation of polluted areas and in the treatment of industrial and municipal wastewaters. Thanks to their unique physical and photochemical properties, chalcogenide NPs are actively used in various optical and data storage devices, sensors, batteries and solar cells [120]. Fungi-assisted biosynthesis of these NPs opens up opportunities for environmentally safe NP production for these applications.

Conclusions
As compared with the NPs of elementary metals and metalloids, the myco-synthesis of oxide and chalcogenide NPs is less widely studied, but in recent years, it has attracted increasing research attention. To date, the ability to form oxide and/or chalcogenide NPs has been found in about 70 species of fungi of different taxa, mainly in asco-and basidiomycetes. Fungal cultures can synthesize oxide, sulfide, selenide, and telluride NPs of many elements, which have diverse shapes and sizes ( Figure 2).

Conclusions
As compared with the NPs of elementary metals and metalloids, the myco-synthesis of oxide and chalcogenide NPs is less widely studied, but in recent years, it has attracted increasing research attention. To date, the ability to form oxide and/or chalcogenide NPs has been found in about 70 species of fungi of different taxa, mainly in asco-and basidiomycetes. Fungal cultures can synthesize oxide, sulfide, selenide, and telluride NPs of many elements, which have diverse shapes and sizes ( Figure 2). The characteristics of NPs of the same chemical compound may vary greatly depending on the conditions of their production and are determined not only by the physical and chemical parameters of the reaction (precursors and their concentration, growth medium composition, pH, temperature, stirring rate, lighting, reaction time, and so on) but also by the characteristics of the fungal bio-object used (culture species, strain and age) and by the method of use of the fungus (as a living culture, filtered mycelial bio-mass, spores, extracts from the vegetative mycelium or fruit bodies, cell-free culture liquids, purified metabolites). The study of the influence of all these conditions on NP shape and size, their surface topography, dispersity, stability, aggregation resistance, formation rate, bioavailability, The characteristics of NPs of the same chemical compound may vary greatly depending on the conditions of their production and are determined not only by the physical and chemical parameters of the reaction (precursors and their concentration, growth medium composition, pH, temperature, stirring rate, lighting, reaction time, and so on) but also by the characteristics of the fungal bio-object used (culture species, strain and age) and by the method of use of the fungus (as a living culture, filtered mycelial bio-mass, spores, extracts from the vegetative mycelium or fruit bodies, cell-free culture liquids, purified metabolites). The study of the influence of all these conditions on NP shape and size, their surface topography, dispersity, stability, aggregation resistance, formation rate, bioavailability, photoluminescent and magnetic properties, and biological activity is very important for selection of the most effective NP producers and optimization of the bio-nano-synthesis methods.
Micro-nano-synthesis of some oxides and chalcogenides, such as TiO2, ZnO, and CdS, has been well studied, but most of the NPs of these compounds remain virtually unexplored in terms of their fungi-mediated production. Fungal cultures are capable of forming NPs of highly diverse chemical compositions, including compounds that are not widely distributed and difficult to obtain, which have great potential for practical applications in various fields of science and technology. Therefore, important challenges facing nano-biotechnologists include: • screening fungal cultures to identify NP producers of new, previously unexplored compounds; • further enhancing the knowledge of already known mycogenic oxide and chalcogenide NPs; • optimization of production methods and scaling up of processes for the biosynthesis of NPs with the required properties on an industrial scale; • studying the possibilities of practical application of NPs and their introduction into practice.
The enormous potential of fungal cultures as NP producers of various oxides and chalcogenides, together with the extremely poor state of knowledge of the myco-nanosynthesis of the majority of these NPs, makes their further detailed and in-depth study, as objects for the biosynthesis of the oxide and chalcogenide NPs and nanomaterials based on them, a highly important task.