Intracellular Amyloid-ß Detection from Human Brain Sections Using a Microfluidic Immunoassay in Tandem with MALDI-MS

Alzheimer’s disease (AD) currently affects more than 30 million people worldwide. The lack of understanding of AD’s physiopathology limits the development of therapeutic and diagnostic tools. Soluble amyloid-ß peptide (Aß) oligomers that appear as intermediates along the Aß aggregation into plaques are considered among the main AD neurotoxic species. Although a wealth of data are available about Aß from in vitro and animal models, there is little known about intracellular Aß in human brain cells, mainly due to the lack of technology to assess the intracellular protein content. The elucidation of the Aß species in specific brain cell subpopulations can provide insight into the role of Aß in AD and the neurotoxic mechanism involved. Here, we report a microfluidic immunoassay for in situ mass spectrometry analysis of intracellular Aß species from archived human brain tissue. This approach comprises the selective laser dissection of individual pyramidal cell bodies from tissues, their transfer to the microfluidic platform for sample processing on-chip, and mass spectrometric characterization. As a proof-of-principle, we demonstrate the detection of intracellular Aß species from as few as 20 human brain cells.