Cytotoxicity of albebetin oligomers depends on cross‐β‐sheet formation

Prefibrillar cytotoxicity was suggested as a common amyloid characteristic. We showed two types of albebetin prefibrillar oligomers are formed during incubation at pH 7.3. Initial round‐shaped oligomers consist of 10–15 molecules determined by atomic force microscopy, do not bind thioflavin‐T and do not affect viability of granular neurons and SH‐SY5Y cells. They are converted into ca. 30–40‐mers possessing cross‐β‐sheet and reducing viability of neuronal cells. Neither monomers nor fibrils possess cytotoxicity. We suggest that oligomeric size is important for stabilising cross‐β‐sheet core critical for cytotoxicity. As albebetin was used as a carrier‐protein for drug delivery, examination of amyloidogenicity is required prior polypeptide biomedical applications.