Figure 1.
X-ray Diffraction analysis of aluminium oxide nanoparticles.
The XRD results shows five dominant peaks [37.72°, 36.53°, 39.46°, 47.80° and 67.01°] confirming the crystalline nature of aluminium oxide nanoparticles.
Figure 2.
Transmission Electron Microscopic analysis of aluminium oxide nanoparticles.
Transmission electron micrograph confirmed the spherical shape of the aluminium oxide nanoparticles with particle size ranging from 40 nm to 100 nm diameters. (n = 3).
Figure 3.
Particle aggregation profile of aluminium oxide nanoparticles.
Time dependent variation in mean hydrodynamic diameter (MHD) of aluminium oxide nanoparticles was observed with respect to particle concentration. (n = 3).
Figure 4.
Bioavailability profile of aluminium oxide nanoparticles.
The available concentration of aluminium oxide nanoparticles in the test matrix is seen to decrease with respect to time. The rate of reduction of bioavailability is faster as the concentration of the nanoparticle increases. (n = 3).
Figure 5.
Effect of aluminium oxide nanoparticles on C. dubia survival.
The relative survival of C. dubia was shown to decrease with respect to time. With nanoparticle concentration, survival rate increased which suggests reduced toxicity of nanoparticles probably due to aggregation. (n = 3).
Figure 6.
Effect of labile aluminium leached from aluminium oxide nanoparticles.
(A) Dissolution of ions from the aluminium oxide nanoparticles showed an increasing trend with time, but the release kinetics is not concentration dependent. (B) The relative survival of C. dubia upon exposure to labile aluminium was quantified. It showed no effect up to 24 h exposure, whereas, 48 and 72 h exposures showed a significant impact on the survival compared to the untreated group.
Figure 7.
Reactive Oxygen Species profile.
Generation of reactive oxygen species (ROS) was found to increase with time and with concentration suggesting oxidative stress induced toxicity of nanoparticles. (n = 3).
Figure 8.
Gross internalization of nanoparticles.
Nanoparticles adsorbed onto the animal outer surface and internalized into the gut were found to increase with exposure concentrations. (n = 3).
Figure 9.
Systemic internalization of nanoparticles.
Systemic internalization of nanoparticles was seen to remain almost constant till 100 µg/mL nanoparticle concentration after which a slight increase was observed for 120 µg/mL. (n = 3).
Figure 10.
Optical microscopic analysis of C. dubia before and after the interaction.
(A) Bright-field micrograph shows nearly transparent animal with traces of algal feed in the alimentary canal of the untreated animal. (B) Phase contrast micrograph shows natural coloration of tissues prior to the nanoparticle exposure. (C) Interacted daphinds show deposition of nanoparticle around the alimentary canal. (D) Altered coloration of the tissues can be noted in the phase contrast micrograph of interacted daphnid.
Figure 11.
Transmission electron microscopy of the alimentary canal.
Alimentary canal of untreated daphnids shows (A) uniform gut lining with intact microvilli and basal membrane; (B) a closure view of the gut lining showing healthy microvilli and basal membrane. The treated samples show (C) disrupted cellular features with (D) disintegrated micrivilli and basal membrane. Certain samples also showed (E) complete destruction of microvilli with few loosely attached cells and (F) abnormal cellular interior. BM: basal membrane; MV: microvilli. The gut lining of at least five different animals were observed to draw a conclusion (n = 5).