MAPT and Alzheimer disease: further reported a sensitive SERS‐based immunosensor utilizing half antibody fragments on head‐flocked gold nanopillar substrates and SERS‐nanotags for blood‐based detection of Tau protein, achieving femtomolar‐level sensitivity (3.21 fm) under 785 nm laser excitation and successfully distinguishing AD patients from healthy controls in clinical plasma samples.[325]