Consistent with the above results, the immunohistochemistry results showed that PLGA NPs with encapsulated S1 significantly decreased the Aβ deposit burden in the AD mouse brains (Figure 4E and 4F), implying that the S1 peptide delivered by PLGA nanoparticle effectively inhibited Aβ production in vivo. Consistent with this result, NPs loaded with S1 peptide were able to inhibit APP cleavage in vitro (Supplementary Figure 3). Here, APP is linked to Alzheimer disease.