Tin oxide nanoparticles trigger the formation of amyloid β oligomers/protofibrils and underlying neurotoxicity as a marker of Alzheimer's diseases

Alzheimer's disease (AD) is known as one of the most common forms of dementia, and oligomerization of amyloid β (Aβ42) peptides can result in the onset of AD. Tin oxide nanoparticles (SnO2 NPs) showed several applications in biomedical fields can trigger unwanted interaction with proteins and inducing protein aggregation. Herein, we synthesized SnO2 NPs via the hydrothermal method and characterized by UV-visible, XRD, FTIR, TEM, and DLS techniques. Afterward, the formation of Aβ42 amyloid oligomers/protofibrils treated alone and with SnO2 NPs was explored by ThT and Nile red fluorescence and CD spectroscopic methods along with TEM imaging. The neurotoxicity of different spices of Aβ42 samples against PC-12 cells was then explored by MTT and caspase-3 activity assays. The characterization of SnO2 NPs confirmed the successful synthesis of crystalline NPs (20-30 nm). Different biophysical and cellular analyses indicated that SnO2 NPs accelerated Aβ42 fibrillogenesis and promoted amyloid oligomers/protofibrils cytotoxicity. As compared to the Aβ42 samples grown alone, the ThT and ANS fluorescence intensity along with ellipticity results indicated the promotory effect of SnO2 NPs on the formation of oligomers/protofibrils. Also, the cellular results showed that the treated Aβ42 samples with SnO2 NPs further reduced cell viability through activation of caspase-3. In conclusion, SnO2 NPs greatly accelerate the fibrillation of Aβ42 peptides and lead to the formation of more toxic species. The present data may offer further warrants into nano-based systems for biomedical applications in the central nervous system.