# The Influence of Silver Nanoparticle Form on the Toxicity in Freshwater Mussels
## 3 Results
Although no significant changes were observed in protein aggregation (Figure 2C), the levels tended to decrease for cubic nAg and were significantly correlated with neutral lipids (\(r=0.65\)) and viscosity (\(r=0.23\)) (Table 2). No significant differences between nAg of similar SA (10 \(\mu\)g/L spherical and 50 \(\mu\)g/L prismatic nAg) for viscosity, lipids and protein aggregation suggests that no other factors than SA contributed to the observed responses. Figure 2: Changes in cytoplasm properties in mussels exposed to nAg forms. Mussel whole tissue homogenate fractions were isolated and analyzed for viscosity (**A**), protein aggregation changes (**B**) and neutral lipids (**C**). The data represent the mean with the standard error. The star symbol * indicates significant differences from controls. Oxidative stress was determined by measuring labile Zn levels, aCOX activity and LPO (Figure 3A-C). The levels of labile Zn were significantly decreased at 2 \(\mu\)g/L spheric and cubic nAg (Figure 3A) but returned to control levels at higher concentrations, suggesting an hormetic type of effect of nAg, perhaps due to SA-mediated effects. The increased levels of Zn for the 50 \(\mu\)g/L cubic nAg were marginal (\(p\) = 0.1). labile Zn levels were significantly correlated with viscosity changes (r = 0.26), suggesting that increased viscosity was partly associated with the mobilization of Zn in the cytoplasm (oxidative stress?). The activity in aCOX, a marker of inflammation and oxidative stress, did not change with either the exposure concentration or the forms of Ag (Figure 3B). No significant changes in LPO were observed in mussel tissues (Figure 3C). No significant difference was obtained between nAg of similar SA, with LPO and COX activities suggesting no influence by factors other than SA on the observed responses. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **CF** & **Air Surv.** & **AChE** & **FD** & **Free Zn** & **aCOX** & **LPO** & **Prot. Agg.** & **Lipids** \\ \hline CF & 1 & & & & & & & & \\ \hline Air surv & 0.08 & 1 & & & & & & & \\ \hline AChE & **0.22** & \(-\)0.04 & 1 & & & & & & \\ \hline FD & 0.04 & 0.06 & \(-\)0.09 & 1 & & & & & \\ \hline Free Zn & 0.15 & \(-\)0.04 & \(-\)0.02 & 0.13 & 1 & & & & \\ \hline aCOX & 0.01 & 0.03 & 0.20 & 0.04 & 0.13 & 1 & & & \\ \hline LPO & 0.18 & 0.18 & \(\mathbf{-0.22}\) & 0.00 & 0.01 & \(-\)0.10 & 1 & & \\ \hline Prot agg & \(-\)0.08 & \(-\)0.11 & \(-\)0.05 & \(-\)0.02 & \(-\)0.05 & 0.04 & 0.13 & 1 & \\ \hline Lipids & 0.05 & \(-\)0.06 & 0.06 & \(-\)0.01 & \(-\)0.05 & 0.11 & 0.16 & **0.65** & 1 \\ \hline Viscosity & \(-\)0.1 & \(-\)0.04 & 0.17 & 0.03 & **0.26** & 0.17 & \(-\)0.02 & **0.23** & **0.45** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Correlation analysis of biomarker data. Figure 3: _Cont._  
Neural activity was also examined in mussels treated with the various forms of Ag using AChE activity assessments (Figure 4). A decrease in AChE was observed in most forms of Ag in the following order: prism (\(p\) < 0.001) > cube (\(p\) = 0.001) > sphere (\(p\) = 0.01), and the dissolved Ag was similar to controls (\(p\) = 0.11) based on statistical differences of the responses (all concentrations included) with respect to controls. Given the possibility that nAg forms (spheres, cubes and prisms) could alter the biophysical properties, such as crowding of the intracellular space, a long-term memory analysis was used to determine the fractal dimension /D of the AChE reaction (Figure 4B). The analysis revealed that the /D of the AChE reaction was reduced by the various geometries (spheres, cubes and prisms) of nAg compared to controls and to dissolved Ag. With respect to controls, the reduction in the /D was, in order of decreases: sphere (\(p\) = 0.01) < cube (\(p\) = 0.03) < prism (\(p\) = 0.05) where the dissolved Ag did not differ from the controls (\(p\) = 0.16).