Selenium nanoparticles (SeNPs) have been produced by many bacterial species like Pantoea agglomerans, Zooglea ramigera, Pseudomonas alcaliphila, Bacillus subtilis, Bacillus cereus and Duganella sp. [ 1 - 3 ]. Selenium respiring bacteria Sulfurospirillum barnesii, Bacillus selenitireducens and Selenihalanaerobacter shriftii also produced SeNPs in anaerobic conditions [ 4 ]. However, production in aerobic condition is much easier than in the anaerobic condition. Anaerobic biogenesis is a tiresome and difficult process [ 1 ].

Acetaminophen (APAP) is well-known drug inducing severe oxidative stress allowing mitochondrial permeability transition in liver cells. Liver cells eliminate free radicals and face apoptosis as a result of the drug hepatotoxicity [ 5 ]. Several studies tackled the hepatotoxic effect of APAP in male and female mice and rat [ 6 - 13 ].

In male albino rats, SeNPs have been used as an antioxidant against the hepatic damage caused by parasitism [ 14 ] and neural and renal APAP toxicity. SeNPs also showed anti-inflammatory and analgesic effects in irradiated rats [ 15 ]. It is therefore, necessary to investigate its ameliorative role against APAP hepatotoxicity in male mice.

Observation of the culture incubated with (Na₂SeO₃) showed a change from yellow to red (Figure 1) which is characteristic for SeNPs. The red color [ 3 ] which was due to the excitation of surface plasmon vibrations in SeNPs provided a convenient spectroscopic signature of the nanoparticles formation [ 1 , 4 ]. No color change could be demonstrated in cultures without selenium dioxide as negative control. The UV-Vis absorption spectra recorded a strong resonance at 335 nm (Figure 1). However, no absorption peak appeared after addition of salts indicating that a constituent of the culture medium was not involved in SeNPs.

The biosynthesized SeNPs shown in TEM image were spherical and polydispersed with average diameter range of 10 - 55 nm (Figure 2(a)). Bacillus megaterium and Bacillus cereus reduced selenite to SeNPs after 40 hrs [ 1 , 21 ].

Bacillus sp. MSh-1 produced spherical SeNPs with 80 nm diameter [ 3 , 18 ]. We consider this study the first that reported the formation of small SeNPs by Bacillus tequilensis. The XRD analysis for the biosynthesized selenium indicated three intense peaks in the whole spectrum of 2q values ranging from 5 to 80 (Figure 3). The diffractions peak at 2q value of 23.780, 29.797 and 43.878 can be indexed to the (100), (101) and (102) planes of the face-centered cubic (fcc) red elemental selenium, respectively [ 21 ].

As AL-Harabi et al. [ 22 ] concluded, liver was the main tissues clearly influenced significantly by nonoparticles treatment. ALP, AST and ALT were increased significantly (p < 0.01) in the group received APAP indicating the toxic effect of the drug. Several investigations accumulated similar findings [ 6 - 13 ].

The enzymes activity in the groups treated with SeNPs immediately after APAP supplementation or in combination with APAP showed normal enzyme activity with no significant difference to that of the control (Table 1). Unfortunately, the two main liver markers (albumin and total proteins) did not exhibit significant variations in either control or treated groups. Similar findings were revealed by Oleaga et al. [ 23 ] where, doxorubicin which is considered hepatotoxic, did not show any effect on albumin. No significant influence in the liver antioxidants has been recorded, except slight changes (p > 0.05) in the group treated with APAP and SeNPs in MDA and in SeNPs group for TAC. This can be interpreted with the toxicity of SeNPs that enhances the liver cells to eliminate free radicals [ 24 ]. In conclusion SeNPs, with very low concentration, generally protected liver against oxidative damage induced by APAP in mice.

Liver histology of the control group appeared more or less normal (Figure 4). The organ was divided

into hepatic lobules in which the central vein was centrally located and surrounded by hepatic columns. The hepatocytes appeared polyhydral with centrally located vesicular nuclei. Hepatic sinusoids were seen between the hepatic columns. Van kupffer cells were frequently seen. The hepatocytes of the mice treated with APAP had cloudy swelling and vacuolar degeneration (Figure 5(a)). Pericentral necrosis was seen in most cases in which the hepatocytes showed strongly eosinophilic cytoplasm with pyknotic nuclei (Figure 5(b)). Centrolobularly, solitary cells underwent pyknosis in some areas. The blood vessels were dilated and engorged with blood. The hepatic sinusoids were dilated in some areas with mild proliferation of Von

kupffer cells. The liver of mice treated with SeNPs appeared more or less histologically normal (Figure 6). No necrotic changes had been recorded. The hepatic lobules were well organized. In some areas, a few cells were very mildly degenerated but without toxic changes. Compared to APAP group, the liver of mice treated with both APAP and SeNPs were markedly improved and the liver appeared normal to more extent. Few cells were still showing very mild degenerative changes and pyknosis (Figure 7). The blood vessels were mildly dilated and congested. No necrotic changes could be seen. Similar damage for liver tissues by APAP has been recorded [ 25 - 28 ]. SeNPs showed also ameliorative effect, histologically, on hepatotoxicity induced by drugs or parasites in several investigations [ 14 , 29 ].

In conclusion, SeNPs can be used to replace today’s therapies of APAP hepatotoxicity as the liver enzymes become normal after treatment with the synthesized nanoparticles. Meanwhile, liver histology showed an improvement by SeNPs administration.