The hallmarks of Alzheimer’s disease (AD) are the accumulation of Aβ plaques and neurofibrillary tangles composed of hyperphosphorylated tau. We developed sensitive cellular assays using human embryonic kidney–293T cells to quantify intracellular self-propagating conformers of Aβ in brain samples from patients with AD or other neurodegenerative diseases. Postmortem brain tissue from patients with AD had measurable amounts of pathological Aβ conformers. Individuals over 80 years of age had the lowest amounts of prion-like Aβ and phosphorylated tau. Unexpectedly, the longevity-dependent decrease in self-propagating tau conformers occurred in spite of increasing amounts of total insoluble tau. When corrected for the abundance of insoluble tau, the ability of postmortem AD brain homogenates to induce misfolded tau in the cellular assays showed an exponential decrease with longevity, with a half-life of about one decade over the age range of 37 to 99 years. Thus, our findings demonstrate an inverse correlation between longevity in patients with AD and the abundance of pathological tau conformers. Our cellular assays can be applied to patient selection for clinical studies and the development of new drugs and diagnostics for AD.

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Nanoparticle cellular interactions are governed by nanoparticle surface chemistry and the surface display of functional (bio)molecules. To conjugate and display thiol-containing (bio)molecules on nanoparticle surfaces, reactions between thiols and functional maleimide groups are often exploited. However, current procedures for modifying nanoparticle surfaces with maleimide groups are complex and can result in nanoparticle aggregation. Here, we demonstrate a straightforward, fast (∼30 min), efficient, and robust one-step surface engineering protocol for modifying gold nanoparticles with functional maleimide groups. We designed a hetero-bifunctional poly(ethylene glycol)-based molecule that attaches efficiently to the gold nanoparticle surface in a single step via its orthopyridyl disulfide (OPSS) terminal end, leaving its maleimide functional group available for downstream reaction with thiols. Using this surface engineering approach, we fabricated gold nanoparticles with near neutral and positive surface charges, respectively. We demonstrate that nanoparticle cellular uptake efficiencies in model mouse breast cancer (4T1) cells, human breast cancer (MDA-MB-231) cells, and human umbilical vein endothelial (HUVEC) cells in tissue culture can be tuned by up to 3 orders of magnitude by adjusting nanoparticle surface chemistry. Our straightforward and efficient maleimide-based nanoparticle surface engineering protocol creates a platform technology for controlled covalent surface attachment of a variety of thiol-containing (bio)molecules to nanoparticles for rational design of nanomaterials with precise cellular interactions for widespread applications in bioanalysis and nanomedicine.

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In microscopy-based drug screens, fluorescent markers carry critical information on how compounds affect different biological processes. However, practical considerations may hinder the use of certain fluorescent markers. Here, we present a deep learning method for overcoming this limitation. We accurately generated predicted fluorescent signals from other related markers and validated this new machine learning (ML) method on two biologically distinct datasets. We used the ML method to improve the selection of biologically active compounds for Alzheimer's disease (AD) from high-content high-throughput screening (HCS). The ML method identified novel compounds that effectively blocked tau aggregation, which would have been missed by traditional screening approaches unguided by ML. The method improved triaging efficiency of compound rankings over conventional rankings by raw image channels. We reproduced this ML pipeline on a biologically independent cancer-based dataset, demonstrating its generalizability.The approach is disease-agnostic and applicable across diverse fluorescence microscopy datasets..