De novo design of a mechano-pharmaceutical screening platform against formation of individual beta-amyloid oligomers.

Small molecules that can reduce the neurotoxic beta-amyloid (Aβ) aggregates in the brain provide a potential treatment for Alzheimer disease (AD). Most screening methods for small-molecule hits focus on the overall Aβ aggregations without a specific target, such as the very first association step (i.e., nucleation) en route to the Aβ oligomers. Located in the middle of a full-length Aβ peptide, Aβ19-20 (diphenylalanine or FF) nucleates the neurotoxic Aβ oligomer formation. Here, we innovate a single-molecule screen method in optical tweezers by targeting the nucleation process in Aβ aggregation, namely FF-dimerization. With a 121-compound National Institutes of Health (NIH) library, we identify 12 inhibitors and 8 stimulants that can inhibit/promote Aβ19-20 dimerization significantly. The representative hits are subjected to the thioflavin T and cell toxicity assays to confirm their inhibiting or stimulating activities. By replacing FF with longer Aβ sequences, our single-molecule platform may identify more specific and potent small molecules to fight AD.