Thioflavin S Staining for MALDI-MSI

Thioflavin S staining was done directly on tissue sections used for MALDI-MSI on ITO coated slides after MALDI-MSI. Slides were first dipped in methanol and to remove DAN matrix and allowed to dry. Tissue was then fixed in 3% formaldehyde in PBS for 15 minutes. 1% Thioflavin S was made in 50 mL H₂O and filtered prior to application. Tissue was first washed three times in 50% ethanol for three minutes each time. A three min H₂O wash was then performed. 1% filtered thioflavin S was then applied to the samples for 10 minutes in the dark. All steps here on out were performed in the dark to preserve fluorescence. The tissue was then dehydrated using three, five-minute washes in 70% ethanol and three, three-minute washes in 50% ethanol. The tissue was then washed in dH₂O for 15 minutes then allowed to air-dry for 15 minutes prior to coverslipping with Fluoroshield with DAPI.