[17, 18]. Other reports demonstrated a responsive cellular property impaired by low nC60 concentration [14] in bacterial membrane composition and fluidity. In the presence of nC60, Pseudomonas putida reduced its unsaturated fatty acids and augmented cyclopropane fatty acids to defend the bacterial membrane against oxidative stress.
Changes in the composition of the population revealed growth barriers to some indigenous microbial organisms. They showed that the ecotoxicological effects of nC60 could occur within the highly complex medium, including soils. Without previous suspension in water, the maximum concentration of C60 was added in dry conditions. The lack of any ecotoxicological effects may suggest that considering higher concentrations, the bioavailability of C60 in the latter experiment is lower [6].
Fullers (1 μM) combined with UV light have shown a substantially larger inactivation (100% increase) of viruses than UV light alone. In a cytotoxicity analysis on human cell lines [3], fullerols are less toxic than aggregate non‐derivatized fullerenes (nC60). C60‐NH2 with a positive charge hindered the growth and reduced the absorption of substrates. This damage has been recorded in two bacterial species (E. coli and Shewanella oneidensis), at a concentration of 10 mg/l, on the cell structures (cell walls and membranes) [19]. The same study showed moderate to no adverse effects for neutrally charged C60 and C60‐OH [20].
2.1.2 Ecotoxicity of Carbon Nanotubes
The ecotoxicity of zebras (Danio rerio) under various salinity conditions for unprocessed, one‐, and double‐wall carbon nanotubes. In zebrafish embryos, single‐walled carbon nanotubes (SWCNTs) have substantial delays in hatching at concentrations above 120 mg/l. Two‐walled carbon nanotubes also provided a hatching delay of more than 240 mg/l. Carbon black did not affect hatching, however. SWCNT concentrations of up to 360 mg/l [21] have not affected embryo development. In the Rainbow Trout experiment, prepared with surfactant sodium dodecyl sulfate (SDS) and sonicity [22], a dose‐dependent increase in ventilation rates and gill pathology (oedema, altered monocytes, and hyperplasia) at concentrations between 0.1 and 0.5 mg/l was observed. The authors concluded that the trout's SWCNTs might act as a respiratory toxicant and precipitate gill mucus. However, this did not have a significant effect on death, development, or reproduction [23].
2.1.3 Ecotoxicity of Metal Nanoparticles
Metal toxicity is affected by different factors, such as solubility, biological site specificity, and the like. Toxic effects and heavy metal toxicity are defined as any functional or morphological body changes resulting from ingested, injected, inhaled, or consumed medications and chemical or biological agents [24, 25]. There are also antibacterial processes in metal nanoparticles. Depending on the load on the membrane surface, metal nanoparticles practise cytotoxicity. Gram‐positive cells are less vulnerable to genotoxic effects because of a thicker peptidoglycan layer compared to Gram‐negative cells. Nanotoxicity can be due to the energy exchange between membrane nanoparticles and their aggregation in the cytoplasm [26]. In dechlorinated water with a hardness of 142 mg CaCO3/l and a pH of 8.2 [27], copper nanoparticles were tested for comparison with the toxicity of soluble Cu ions in zebrafish (D. rerio) [27] (CuSO4). In this sample, Cu nanoparticles were lower in toxicity than Cu ions. Like Ag [28], nanoparticles are used as an antimicrobial agent. Silver nanoparticles play an essential role in the field of nanotechnology and nanomedicine. Their specific size‐dependent characteristics make these peculiar physical, chemical, and biological properties superior and indispensable. The possible antimicrobial activity of silver nanoparticles is numerous pathogenic microorganisms.
Silver nanoparticles demonstrate undesirable toxic effects on human health and the environment alongside this antimicrobial activity [1]. Ecologists have cautioned that nano‐antimicrobials released into water sources. The widespread release of such a potent antimicrobial may have significant negative implications for bacteria in natural systems. There is also increasing evidence that silver nanoparticles and being toxic to bacteria are incredibly harmful to mammalian cells [29]. Silver nanoparticles damage brain cells [30], liver cells [31], and stem cells. Silver is also extremely toxic to fish [32] algae, individual plants, fungi [33] crustaceans, and bacteria such as heterotrophic nitrogen‐fixing bacteria and chemical soil‐forming bacteria [34] in its bulk form. Silver nanoparticles, which have well‐known bactericidal and cytotoxic effects, including specific mitochondrial products and ROS generation, are mainly produced for antiseptic purposes [31].
Silver is also extremely toxic to fish [32] algae, individual plants, fungi [33] crustaceans, and bacteria such as heterotrophic nitrogen‐fixing bacteria and chemical soil‐forming bacteria [34] in its bulk form. Silver nanoparticles, including unique mitochondrial products and ROS generation, are mainly formulated for antiseptic purposes and have well‐established bactericidal and cytotoxic effects [31, 35].
2.1.4 Ecotoxicity of Nanocomposites
Nanocomposites vowed to do so because of their multifunction, which means that distinctive properties with conventional materials can be combined [36]. Depending on the nanophase and matrix nature, a wide variety of nanocomposites can be developed [37]. Through two separate viewpoints, the concept of using polymer metal nanocomposites is beneficial. First, by preventing the autocomposition of polymer‐stabilized metal nanoparticles, nanoparticles' production can be considered one of the most encouraging resolutions to stability. Furthermore, the use of immobilized NPs limits their environmental changes [38, 39]. The features of the metal nanoparticles do not primarily determine the characteristics of nanocomposites. For example, the formulation of metal nanoparticles in polymer matrices can significantly change the polymer morphology because of the existence of nanoporosity, which promotes mass transfer within the nanocomposites and specific additional structural parameters that are of high significance in their practical applications [40]. A significant number of water purification and efficiency problems are solved by nanotechnology [41]. The application of metal nanoparticles in the field of reductive dechlorination of organic halogenated compounds in groundwater has been meticulously observed [42]. As pure monometallic entities or in combination with platinum, iron nanoparticles are one of the most substantial components. The long‐term stability of these nanoparticles can, however, be enhanced by immobilization in stable support. The ion sharing is widely used in various water treatment ion‐sharing processes to prevent undesired or harmful ionic impurities such as hardness ions, iron, and heavy metals. The modification of such bactericidal metal nanoparticles allows for eliminating microbiological contaminants by a combination of traditional water treatment with disinfection. One person may perform the two extra water treatment measures with one person.
Nanoparticles of titanium dioxide (TiO2) tend to be of little toxicity to terrestrial species and are used as nanocomposites on a sunscreen where TiO2 has been coated with magnesium, silica, or alumina and also with amphiphilic organic substances such as polydimethylsiloxane (PDMS), which ageing alters [43].
Another critical technical problem, known as biofouling, can also be solved using silver nanoparticles containing nanocomposites. Biofouling or biological fouling [37] is the unintended accumulation of microbes on the surface of water treatment systems and materials, such as reverse osmosis membranes, cooling water cycles, and ion exchange resins. The surface shift technique was based on commercially available ion exchange materials with a silver shell [42] and a magnetic core [43]. These products are the eco‐friendly bactericide nanocomposites suited for traditional water treatment and reagent‐free disinfection. These materials have the main advantages as follows: (i) They are trapped firmly into the polymer matrix, which prohibits the escape into the medium being processed. (ii) Applying a material's surface metallic nanoparticles ensures interaction with the bacteria to avoid fast water disinfection. (iii) Metal nanoparticles are superparamagnetically shielded in nature because a simple magnet trap prevents any post‐contamination of treated water with metal nanoparticles leached by the polymer matrix. (iv) Like the ion exchange capacity [44], the surface location of metal nanoparticles does not essentially affect the core
