Despite intense interests in developing blood measurements of Alzheimer’s disease (AD), the progress has been confounded by limited sensitivity and poor correlation to brain pathology. Here, we present a dedicated analytical platform for measuring different populations of circulating amyloid β (Aβ) proteins – exosome-bound vs. unbound – directly from blood. The technology, termed a mplified p lasmonic ex osome (APEX), leverages in situ enzymatic conversion of localized optical deposits and double-layered plasmonic nanostructures to enable sensitive, multiplexed population analysis. It demonstrates superior sensitivity (~200 exosomes), and enables diverse target co-localization in exosomes. Employing the platform, we find that prefibrillar Aβ aggregates preferentially bind with exosomes. We thus define a population of Aβ as exosome-bound (Aβ42+ CD63+) and measure its abundance directly from AD and control blood samples. As compared to the unbound or total circulating Aβ, the exosome-bound Aβ measurement could better reflect PET imaging of brain amyloid plaques and differentiate various clinical groups.

Exosomes are nanoscale vesicles distinguished by characteristic biophysical and biomolecular features; current analytical approaches, however, remain univariate. Here, we develop a dedicated platform for multiparametric exosome analysis—through simultaneous biophysical and biomolecular evaluation of the same vesicles—directly in clinical biofluids. Termed templated plasmonics for exosomes, the technology leverages in situ growth of gold nanoshells on vesicles to achieve multiselectivity. For biophysical selectivity, the nanoshell formation is templated by and tuned to distinguish exosome dimensions. For biomolecular selectivity, the nanoshell plasmonics locally quenches fluorescent probes only if they are target-bound on the same vesicle. The technology thus achieves multiplexed analysis of diverse exosomal biomarkers (e.g., proteins and microRNAs) but remains unresponsive to nonvesicle biomarkers. When implemented on a microfluidic, smartphone-based sensor, the platform is rapid, sensitive, and wash-free. It not only distinguished biomarker organizational states in native clinical samples but also showed that the exosomal subpopulation could more accurately differentiate patient prognosis.

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Alginate hydrogels possess tunable mechanical properties that can mimic soft marrow tissue and present three-dimensional (3D) cues. This study evaluates its utility for supporting leukemic cell growth in vitro and its impact on cell survival, growth, and differentiation. Our results showed that the standard viscosity alginates had compromised leukemia cell viability but lower viscosity alginates recovered cell viability and improved 3D cell proliferation (27 fold) compared to 2D cultures (18 fold). Conjugation with RGD peptides promoted further cell growth (43 folds). In general, 3D hydrogels supported high-density cultures better than 2D cultures. Leukemic cells formed densely packed cell clusters in alginate hydrogels and spontaneously differentiated into a more diverse myeloid population. The cell cycle data suggested that more cells go into active cycling with a G2/M arrest in alginate hydrogels and the presence of multiploidy confirmed maturation toward megakaryocytes. In summary, superior culture of leukemia cells in 3D hydrogels is demonstrated in this study accompanied by a potential role of physical cues influencing cell fate decision. Manipulation of biophysical and biochemical properties of alginate hydrogels permits the study of specific interactions and serves to provide a robust 3D platform for studying extrinsic contributions inside the bone marrow.

Background and purpose Various blood biomarkers reflecting brain amyloid‐β (Aβ) load have recently been proposed with promising results. However, to date, no comparative study amongst blood biomarkers has been reported. Our objective was to examine the diagnostic performance and cost effectiveness of three blood biomarkers on the same cohort. Methods Using the same cohort (n = 68), the performances of the single‐molecule array (Simoa) Aβ40, Aβ42, Aβ42/Aβ40 and the amplified plasmonic exosome (APEX) Aβ42 blood biomarkers were compared using amyloid positron emission tomography (PET) as the reference standard. The extent to which these blood tests can reduce the recruitment cost of clinical trials was also determined by identifying amyloid positive (Aβ+) participants. Results Compared to Simoa biomarkers, APEX‐Aβ42 showed significantly higher correlations with amyloid PET retention values and excellent diagnostic performance (sensitivity 100%, specificity 93.3%, area under the curve 0.995). When utilized for clinical trial recruitment, our simulation showed that pre‐screening with blood biomarkers followed by a confirmatory amyloid PET imaging would roughly half the cost (56.8% reduction for APEX‐Aβ42 and 48.6% for Simoa‐Aβ42/Aβ40) compared to the situation where only PET imaging is used. Moreover, with 100% sensitivity, APEX‐Aβ42 pre‐screening does not increase the required number of initial participants. Conclusions With its high diagnostic performance, APEX is an ideal candidate for Aβ+ subject identification, monitoring and primary care screening, and could efficiently enrich clinical trials with Aβ+ participants whilst halving recruitment costs.

These tests, which assess different aspects of the patients' cognitive abilities, include abbreviated mental test (AMT), Alzheimer's disease assessment scale-cognitive subscale (ADAS-Cog), mini mental state examination (MMSE), the Montreal cognitive assessment (MoCa), and short blessed test (SBT). Such assessments, however, are subjective and detect diseases only at a late stage. [3-5] As pathological manifestations of neurodegenerative diseases are mainly confined within the brain and difficult to access, alternative methods for evaluating disease pathology involve either invasive biopsy or expensive brain imaging; these approaches are complex and challenging, resulting in limited clinical adoption. [6,7] Consequently, there is an intense interest in developing blood-based measurements [8-11] for safe, minimally invasive disease detection and longitudinal monitoring. Extracellular vesicles (EVs) are nanoscale membrane vesicles found abundantly in almost all bodily fluids. [12,13] These vesicles have recently emerged as a promising circulating biomarker for neurodegenerative diseases. Unlike most of the other molecules in the brain, which are impeded by the highly selective blood-brain barrier and cannot enter the circulation, recent studies have found that EVs can readily cross the blood-brain barrier. [14-17] Moreover, EVs contain diverse molecular contents reflective of their parent cells and extracellular environment. [18-20] These EV molecular cargoes are present in different organizational forms-either as inherited constituents from the parent Neurodegenerative diseases are heterogeneous disorders characterized by a progressive loss of function and/or death of nerve cells, leading to severe cognitive and functional decline. Due to the complex pathology, early detection and intervention are critical to the development of successful treatments; however, current diagnostic approaches are limited to subjective, late-stage clinical findings. Extracellular vesicles (EVs) have recently emerged as a promising circulating biomarker for neurodegenerative diseases. Actively released by diverse cells, EVs are nanoscale membrane vesicles. They abound in blood, readily cross the blood-brain barrier, and carry diverse molecular cargoes in different organizational states: these molecular cargoes are inherited from the parent cells or bound to the EV membrane through surface associations. Specifically, EVs have been found to be associated with several important pathogenic proteins of neurodegenerative diseases, and their involvement could alter disease progression. This article provides an overview of EVs as circulating biomarkers of neurodegenerative diseases and introduces new technological advances to characterize the biophysical properties of EV-associated biomarkers for accurate, blood-based detection of neurodegenerative diseases.

Current technologies to subtype glioblastoma (GBM), the most lethal brain tumor, require highly invasive brain biopsies. Here, we develop a dedicated analytical platform to achieve direct and multiplexed profiling of circulating RNAs in extracellular vesicles for blood-based GBM characterization. The technology, termed ‘enzyme ZIF-8 complexes for regenerative and catalytic digital detection of RNA’ (EZ-READ), leverages an RNA-responsive transducer to regeneratively convert and catalytically enhance signals from rare RNA targets. Each transducer comprises hybrid complexes – protein enzymes encapsulated within metal organic frameworks – to configure strong catalytic activity and robust protection. Upon target RNA hybridization, the transducer activates directly to liberate catalytic complexes, in a target-recyclable manner; when partitioned within a microfluidic device, these complexes can individually catalyze strong chemifluorescence reactions for digital RNA quantification. The EZ-READ platform thus enables programmable and reliable RNA detection, across different-sized RNA subtypes (miRNA and mRNA), directly in sample lysates. When clinically evaluated, the EZ-READ platform established composite signatures for accurate blood-based GBM diagnosis and subtyping.

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