Subtyping of circulating exosome-bound amyloid β reflects brain plaque deposition

Thermodynamics of oligomerization and Helix-to-sheet structural transition of amyloid β-protein on anionic phospholipid vesicles

Understanding oligomerization and aggregation of the amyloid-β protein is important to elucidate the pathological mechanisms of Alzheimer's disease, and lipid membranes play critical roles in this process. In addition to studies reported by other groups, our group has also reported that the negatively-charged lipid bilayers with a high positive curvature induced α-helix-to-β-sheet conformational transitions of amyloid-β-(1-40) upon increase in protein density on the membrane surface and promoted amyloid fibril formation of the protein. Herein, we investigated detailed mechanisms of the conformational transition and oligomer formation of the amyloid-β protein on the membrane surface. Changes in the fractions of the three protein conformers (free monomer, membrane-bound α-helix-rich conformation, and β-sheet-rich conformation) were determined from the fluorescent spectral changes of the tryptophan probe in the protein. The helix-to-sheet structural transition on the surface was described by a thermodynamic model of octamer formation driven by entropic forces including hydrophobic interactions. These findings provide useful information for understanding the self-assembly of amyloidogenic proteins on lipid membrane surfaces.

Exosome-Based Macromolecular neurotherapeutic drug delivery approaches in overcoming the Blood-Brain barrier for treating brain disorders

Delivering drugs to the brain is a complex challenge in medical research, particularly for disorders like Alzheimer's and Parkinson's. The blood-brain barrier restricts the entry of many therapeutic molecules, hindering their effectiveness. Nanoparticles, a potential solution, face issues like toxicity and limited approvals. A new avenue explores the use of small extracellular vesicles (sEVs), i.e., exosomes, as natural carriers for drug delivery. sEVs, tiny structures below 150 nm, show promise due to their minimal immune response and ability to precisely deliver drugs. This review focuses on the potential of sEVs-based drug delivery systems for treating neurological disorders, brain cancers, and other brain-related issues. Notably, bioengineered sEVs-carrying therapeutic compounds exhibit promise in early studies. The unique features of sEVs, such as their small size and natural properties, position them as candidates to overcome challenges in drug delivery to the brain. Ongoing clinical trials and research into sEVs behavior within the body further highlight their potential for revolutionizing drug delivery and addressing complex brain conditions.

Efficient EVs separation and detection by an alumina-nanochannel-array-membrane integrated microfluidic chip and an antibody barcode biochip

BACKGROUND

Small endosome-derived lipid nanovesicles (30-200 nm) are actively secreted by living cells and serve as pivotal biomarkers for early cancer diagnosis. However, the study of extracellular vesicles (EVs) requires isolation and purification from various body fluids. Although traditional EVs isolation and detection technologies are mature, they usually require large amount of sample, consumes long-time, and have relatively low-throughput. How to efficiently isolate, purify and detect these structurally specific EVs from body fluids with high-throughput remains a great challenge in in vitro diagnostics and clinical research.

RESULTS

Herein, we suggest a nanosized microfluidic device for efficient and economical EVs filtration based on an alumina nanochannel array membrane. We evaluated the filtration device performance of alumina membranes with different diameters and found that an optimized chamber array with a hydrophilic-treated channel diameter of 90 nm could realize a filtration efficiency of up to 82% without any assistance from chemical or physical separation methods. Importantly, by integrating meticulously designed multichannel microfluidic biochips, EVs can be captured in-situ and monitored by antibody barcode biochip. The proposed filtration chip together with the high-throughput detection chip were capable of filtration of a few tens of μL samples and recognition of different phonotypes. The practical filtration and detection of EVs from clinical samples demonstrated the high performance of the device.

SIGNIFICANT

Overall, this work provides a cost-effective, highly efficient and automated EVs filtration chip and detection dual-function integrated chip platform, which can directly separate EVs from serum or cerebrospinal fluid with an efficiency of 82% and conduct in-situ detection. This small fluidic device can provide a powerful tool for highly efficient identifying and analyzing EVs, presenting great application potential in clinical detection.

Extracellular vesicles as nanotheranostic platforms for targeted neurological disorder interventions

Central Nervous System (CNS) disorders represent a profound public health challenge that affects millions of people around the world. Diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and traumatic brain injury (TBI) exemplify the complexities and diversities that complicate their early detection and the development of effective treatments. Amid these challenges, the emergence of nanotechnology and extracellular vesicles (EVs) signals a new dawn for treating and diagnosing CNS ailments. EVs are cellularly derived lipid bilayer nanosized particles that are pivotal in intercellular communication within the CNS and have the potential to revolutionize targeted therapeutic delivery and the identification of novel biomarkers. Integrating EVs with nanotechnology amplifies their diagnostic and therapeutic capabilities, opening new avenues for managing CNS diseases. This review focuses on examining the fascinating interplay between EVs and nanotechnology in CNS theranostics. Through highlighting the remarkable advancements and unique methodologies, we aim to offer valuable perspectives on how these approaches can bring about a revolutionary change in disease management. The objective is to harness the distinctive attributes of EVs and nanotechnology to forge personalized, efficient interventions for CNS disorders, thereby providing a beacon of hope for affected individuals. In short, the confluence of EVs and nanotechnology heralds a promising frontier for targeted and impactful treatments against CNS diseases, which continue to pose significant public health challenges. By focusing on personalized and powerful diagnostic and therapeutic methods, we might improve the quality of patients.

Surface-functionalized SERS platform for deep learning-assisted diagnosis of Alzheimer's disease

Early diagnosis of Alzheimer's disease is crucial to stall the deterioration of brain function, but conventional diagnostic methods require complicated analytical procedures or inflict acute pain on the patient. Then, label-free Surface-enhanced Raman spectroscopy (SERS) analysis of blood-based biomarkers is a convenient alternative to rapidly obtain spectral information from biofluids. However, despite the rapid acquisition of spectral information from biofluids, it is challenging to distinguish spectral features of biomarkers due to interference from biofluidic components. Here, we introduce a deep learning-assisted, SERS-based platform for separate analysis of blood-based amyloid β (1-42) and metabolites, enabling the diagnosis of Alzheimer's disease. SERS substrates consisting of Au nanowire arrays are fabricated and functionalized in two characteristic ways to compare the validity of different Alzheimer's disease biomarkers measured on our SERS system. The 6E10 antibody is immobilized for the capture of amyloid β (1-42) and analysis of its oligomerization process, while various self-assembled monolayers are attached for different dipole interactions with blood-based metabolites. Ultimately, SERS spectra of blood plasma of Alzheimer's disease patients and human controls are measured on the substrates and classified via advanced deep learning techniques that automatically extract informative features to learn generalizable representations. Accuracies up to 99.5% are achieved for metabolite-based analyses, which are verified with an explainable artificial intelligence technique that identifies key spectral features used for classification and for deducing significant biomarkers.

Exosomal mediators in sepsis and inflammatory organ injury: unraveling the role of exosomes in intercellular crosstalk and organ dysfunction

Sepsis, a severe systemic inflammatory response to infection, remains a leading cause of morbidity and mortality worldwide. Exosomes, as mediators of intercellular communication, play a pivotal role in the pathogenesis of sepsis through modulating immune responses, metabolic reprogramming, coagulopathy, and organ dysfunction. This review highlights the emerging significance of exosomes in these processes. Initially, it provides an in-depth insight into exosome biogenesis and characterization, laying the groundwork for understanding their diverse and intricate functions. Subsequently, it explores the regulatory roles of exosomes in various immune cells such as neutrophils, macrophages, dendritic cells, T cells, and B cells. This analysis elucidates how exosomes are pivotal in modulating immune responses, thus contributing to the complexity of sepsis pathophysiology. Additionally, this review delves into the role of exosomes in the regulation of metabolism and subsequent organ dysfunction in sepsis. It also establishes a connection between exosomes and the coagulation cascade, which affects endothelial integrity and promotes thrombogenesis in sepsis. Moreover, the review discusses the dual role of exosomes in the progression and resolution of sepsis, exploring their complex involvement in inflammation and healing processes. Furthermore, it underscores their potential as biomarkers and therapeutic targets. Understanding these mechanisms presents new opportunities for novel interventions to mitigate the severe outcomes of sepsis, emphasizing the therapeutic promise of exosome research in critical care settings.

[On the road to biological blood diagnosis of Alzheimer's disease?]

The growing number of people suffering from Alzheimer's disease (AD) represents a major public health problem. The diagnosis of AD is multidisciplinary and involves the use of amyloid and tau biomarkers measured in cerebrospinal fluid. Recent advances in analytical techniques now allow us to measure these biomarkers in blood. Blood biomarkers offer particularly promising potential for early, minimally invasive detection of AD, as well as for differential diagnosis of dementia and patient follow-up. The aim of this review is to provide an overview of current and candidate blood biomarkers for AD, their informative value, and their potential to be integrated into clinical practice in the near future.

Construction of built-in correction photoelectrochemical sensing platform for diagnosis of Alzheimer's disease

The occurrence of Alzheimer's disease (AD) is strongly associated with the progressive aggregation of a 42-amino-acid fragment derived from the amyloid-β precursor protein (Aβ1-42). Therefore, it is crucial to establish a versatile platform that can effectively detect Aβ1-42 to aid in the early-stage preclinical diagnosis of AD. Herein, we introduce a specialized split-type analytical platform that enables sensitive and accurate monitoring of Aβ1-42 based on a self-corrected photoelectrochemical (PEC) sensing system. To realize this design, gelatinized Ti3C2@Bi2WO6 Schottky heterojunctions were prepared and served as photoelectrodes for tackling the photoinduced charge carriers. Functionalized CaCO3@CuO2 nanocomposites were used as signal converters to detect Aβ1-42 and amplify the signal further. Benefiting from the glucose oxidation induced acid microenvironment and H2O2 output, the nanocomposites are able to rapidly decompose, producing Ca2+ and Fenton-like catalyst Cu2+. The Cu2+-driven Fenton-like reaction generated ·OH, which accelerated the 3,3',5,5'-tetramethylbenzidine (TMB) oxidation. Additionally, Ca2+ was cross-linked with alginate inducing gelation on the surface of Ti3C2@Bi2WO6 Schottky heterojunctions, influencing mass transfer and light absorption. Eventually results in the shift of photocurrent, allowing for precise quantification with a detection limit of 0.06 pg mL-1. The combination of colorimetric variation and the photoelectric effect provide a more accurate and reliable result. This research opens up new possibilities for constructing PEC platforms and beyond.

Specific Binding of Alzheimer's Aβ Peptides to Extracellular Vesicles

Alzheimer's disease (AD) is the fifth leading cause of death among adults aged 65 and older, yet the onset and progression of the disease is poorly understood. What is known is that the presence of amyloid, particularly polymerized Aβ42, defines when people are on the AD continuum. Interestingly, as AD progresses, less Aβ42 is detectable in the plasma, a phenomenon thought to result from Aβ becoming more aggregated in the brain and less Aβ42 and Aβ40 being transported from the brain to the plasma via the CSF. We propose that extracellular vesicles (EVs) play a role in this transport. EVs are found in bodily fluids such as blood, urine, and cerebrospinal fluid and carry diverse "cargos" of bioactive molecules (e.g., proteins, nucleic acids, lipids, metabolites) that dynamically reflect changes in the cells from which they are secreted. While Aβ42 and Aβ40 have been reported to be present in EVs, it is not known whether this interaction is specific for these peptides and thus whether amyloid-carrying EVs play a role in AD and/or serve as brain-specific biomarkers of the AD process. To determine if there is a specific interaction between Aβ and EVs, we used isothermal titration calorimetry (ITC) and discovered that Aβ42 and Aβ40 bind to EVs in a manner that is sequence specific, saturable, and endothermic. In addition, Aβ incubation with EVs overnight yielded larger amounts of bound Aβ peptide that was fibrillar in structure. These findings point to a specific amyloid-EV interaction, a potential role for EVs in the transport of amyloid from the brain to the blood, and a role for this amyloid pool in the AD process.

Ultrasensitive and Multiple Biomarker Discrimination for Alzheimer's Disease via Plasmonic & Microfluidic Sensing Technologies

As the population ages, the worldwide prevalence of Alzheimer's disease (AD) as the most common dementia in the elderly is increasing dramatically. However, a long-term challenge is to achieve rapid and accurate early diagnosis of AD by detecting hallmarks such as amyloid beta (Aβ42). Here, a multi-channel microfluidic-based plasmonic fiber-optic biosensing platform is established for simultaneous detection and differentiation of multiple AD biomarkers. The platform is based on a gold-coated, highly-tilted fiber Bragg grating (TFBG) and a custom-developed microfluidics. TFBG excites a high-density, narrow-cladding-mode spectral comb that overlaps with the broad absorption of surface plasmons for high-precision interrogation, enabling ultrasensitive monitoring of analytes. In situ detection and in-parallel discrimination of different forms of Aβ42 in cerebrospinal fluid (CSF) are successfully demonstrated with a detection of limit in the range of ≈30-170 pg mL-1, which is one order of magnitude below the clinical cut-off level in AD onset, providing high detection sensitivity for early diagnosis of AD. The integration of the TFBG sensor with multi-channel microfluidics enables simultaneous detection of multiple biomarkers using sub-µL sample volumes, as well as combining initial binding rate and real-time response time to differentiate between multiple biomarkers in terms of binding kinetics. With the advantages of multi-parameter, low consumption, and highly sensitive detection, the sensor represents an urgently needed potentials for large-scale diagnosis of diseases at early stage.

Neuropathogenesis-on-chips for neurodegenerative diseases

Developing diagnostics and treatments for neurodegenerative diseases (NDs) is challenging due to multifactorial pathogenesis that progresses gradually. Advanced in vitro systems that recapitulate patient-like pathophysiology are emerging as alternatives to conventional animal-based models. In this review, we explore the interconnected pathogenic features of different types of ND, discuss the general strategy to modelling NDs using a microfluidic chip, and introduce the organoid-on-a-chip as the next advanced relevant model. Lastly, we overview how these models are being applied in academic and industrial drug development. The integration of microfluidic chips, stem cells, and biotechnological devices promises to provide valuable insights for biomedical research and developing diagnostic and therapeutic solutions for NDs.

Extracellular Vesicles Slow Down Aβ(1-42) Aggregation by Interfering with the Amyloid Fibril Elongation Step

Formation of amyloid-β (Aβ) fibrils is a central pathogenic feature of Alzheimer's disease. Cell-secreted extracellular vesicles (EVs) have been suggested as disease modulators, although their exact roles and relations to Aβ pathology remain unclear. We combined kinetics assays and biophysical analyses to explore how small (<220 nm) EVs from neuronal and non-neuronal human cell lines affected the aggregation of the disease-associated Aβ variant Aβ(1-42) into amyloid fibrils. Using thioflavin-T monitored kinetics and seeding assays, we found that EVs reduced Aβ(1-42) aggregation by inhibiting fibril elongation. Morphological analyses revealed this to result in the formation of short fibril fragments with increased thicknesses and less apparent twists. We suggest that EVs may have protective roles by reducing Aβ(1-42) amyloid loads, but also note that the formation of small amyloid fragments could be problematic from a neurotoxicity perspective. EVs may therefore have double-edged roles in the regulation of Aβ pathology in Alzheimer's disease.

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

Investigating metabolic dysregulation in serum of triple transgenic Alzheimer's disease male mice: implications for pathogenesis and potential biomarkers

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease that lacks convenient and accessible peripheral blood diagnostic markers and effective drugs. Metabolic dysfunction is one of AD risk factors, which leaded to alterations of various metabolites in the body. Pathological changes of the brain can be reflected in blood metabolites that are expected to explain the disease mechanisms or be candidate biomarkers. The aim of this study was to investigate the changes of targeted metabolites within peripheral blood of AD mouse model, with the purpose of exploring the disease mechanism and potential biomarkers. Targeted metabolomics was used to quantify 256 metabolites in serum of triple transgenic AD (3 × Tg-AD) male mice. Compared with controls, 49 differential metabolites represented dysregulation in purine, pyrimidine, tryptophan, cysteine and methionine and glycerophospholipid metabolism. Among them, adenosine, serotonin, N-acetyl-5-hydroxytryptamine, and acetylcholine play a key role in regulating neural transmitter network. The alteration of S-adenosine-L-homocysteine, S-adenosine-L-methionine, and trimethylamine-N-oxide in AD mice serum can served as indicator of AD risk. The results revealed the changes of metabolites in serum, suggesting that metabolic dysregulation in periphery in AD mice may be related to the disturbances in neuroinhibition, the serotonergic system, sleep function, the cholinergic system, and the gut microbiota. This study provides novel insights into the dysregulation of several key metabolites and metabolic pathways in AD, presenting potential avenues for future research and the development of peripheral biomarkers.

Dielectrophoretic Capture of Cancer-Derived Small-Extracellular-Vesicle-Bound Janus Nanoparticles via Lectin-Glycan Interaction

Glycosylation is closely related to cellular metabolism and disease progression. In particular, glycan levels in cancer cells and tissues increase during cancer progression. This upregulation of glycosylation in cancer cells may provide a basis for the development of new biomarkers for the targeting and diagnosis of specific cancers. Here, they developed a detection technology for pancreatic cancer cell-derived small extracellular vesicles (PC-sEVs) based on lectin-glycan interactions. Lectins specific for sialic acids are conjugated to Janus nanoparticles to induce interactions with PC-sEVs in a dielectrophoretic (DEP) system. PC-sEVs are selectively bound to the lectin-conjugated Janus nanoparticles (lectin-JNPs) with an affinity comparable to that of conventionally used carbohydrate antigen 19-9 (CA19-9) antibodies. Furthermore, sEVs-bound Lectin-JNPs (sEVs-Lec-JNPs) are manipulated between two electrodes to which an AC signal is applied for DEP capture. In addition, the proposed DEP system can be used to trap the sEVs-Lec-JNP on the electrodes. Their results, which are confirmed by lectin-JNPs using the proposed DEP system followed by target gene analysis, provide a basis for the development of a new early diagnostic marker based on the glycan characteristics of PC-sEVs. In turn, these novel detection methods could overcome the shortcomings of commercially available pancreatic cancer detection techniques.

Advances in colorimetric biosensors of exosomes: novel approaches based on natural enzymes and nanozymes

Exosomes are 30-150 nm vesicles derived from diverse cell types, serving as one of the most important biomarkers for early diagnosis and prognosis of diseases. However, the conventional detection method for exosomes faces significant challenges, such as unsatisfactory sensitivity, complicated operation, and the requirement of complicated devices. In recent years, colorimetric exosome biosensors with a visual readout underwent rapid development due to the advances in natural enzyme-based assays and the integration of various types of nanozymes. These synthetic nanomaterials show unique physiochemical properties and catalytic abilities, enabling the construction of exosome colorimetric biosensors with novel principles. This review will illustrate the reaction mechanisms and properties of natural enzymes and nanozymes, followed by a detailed introduction of the recent advances in both types of enzyme-based colorimetric biosensors. A comparison between natural enzymes and nanozymes is made to provide insights into the research that improves the sensitivity and convenience of assays. Finally, the advantages, challenges, and future directions of enzymes as well as exosome colorimetric biosensors are highlighted, aiming at improving the overall performance from different approaches.

Novel method for collecting hippocampal interstitial fluid extracellular vesicles (EVISF ) reveals sex-dependent changes in microglial EV proteome in response to Aβ pathology

Brain-derived extracellular vesicles (EVs) play an active role in Alzheimer's disease (AD), relaying important physiological information about their host tissues. The internal cargo of EVs is protected from degradation, making EVs attractive AD biomarkers. However, it is unclear how circulating EVs relate to EVs isolated from disease-vulnerable brain regions. We developed a novel method for collecting EVs from the hippocampal interstitial fluid (ISF) of live mice. EVs (EVISF ) were isolated via ultracentrifugation and characterized by nanoparticle tracking analysis, immunogold labelling, and flow cytometry. Mass spectrometry and proteomic analyses were performed on EVISF cargo. EVISF were 40-150 nm in size and expressed CD63, CD9, and CD81. Using a model of cerebral amyloidosis (e.g., APPswe, PSEN1dE9 mice), we found protein concentration increased but protein diversity decreased with Aβ deposition. Genotype, age, and Aβ deposition modulated proteostasis- and immunometabolic-related pathways. Changes in the microglial EVISF proteome were sexually dimorphic and associated with a differential response of plaque associated microglia. We found that female APP/PS1 mice have more amyloid plaques, less plaque associated microglia, and a less robust- and diverse- EVISF microglial proteome. Thus, in vivo microdialysis is a novel technique for collecting EVISF and offers a unique opportunity to explore the role of EVs in AD.

CSF Extracellular Vesicle Aβ42 and Tau/Aβ42 Ratio Are Associated with Cognitive Impairment in Older People with HIV

HIV-associated neurocognitive disorders (HAND) remain prevalent despite viral suppression on antiretroviral therapy (ART). Older people with HIV (PWH) are also at risk for amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). β-amyloid (Aβ) and Tau biomarkers are associated with aMCI/AD, but their relationship to HAND is unclear. Given the role of extracellular vesicles (EVs) in age-related neurological disorders, we investigated soluble and EV-associated Aβ42, total Tau, NFL, GFAP, ICAM-1, VCAM-1, and CRP in relation to cognitive impairment in PWH. Plasma and CSF EVs were isolated from 184 participants (98 PWH on ART and 86 HIV- controls). Biomarkers were measured using Meso Scale Discovery assays. The median age of PWH was 53 years, and 52% were diagnosed with mild forms of HAND. PWH had increased plasma NFL (p = 0.04) and CSF Aβ42 (p = 0.0003) compared with HIV- controls but no significant difference in Tau or EV-associated forms of these markers. CSF EV Aβ42 was decreased (p = 0.0002) and CSF EV Tau/Aβ42 ratio was increased (p = 0.001) in PWH with HAND vs. no HAND, while soluble forms of these markers showed no significant differences. Decreased CSF EV Aβ42 (p < 0.0001) and an increased CSF EV Tau/Aβ42 ratio (p = 0.0003) were associated with lower neurocognitive T scores in age-adjusted models; an optimal model included both CSF EV Aβ42 and plasma NFL. Levels of soluble, but not EV-associated, ICAM-1, VCAM-1, and CRP were increased in PWH with HAND vs. no HAND (p < 0.05). These findings suggest that decreased Aβ42 and an increased Tau/Aβ42 ratio in CSF EVs are associated with cognitive impairment in older PWH, and these EV-associated biomarkers may help to distinguish aMCI/AD from HIV-related cognitive disorders in future studies.

Nano-Brush Structure for Rapid Label-Free Differentiation of Alzheimer's Disease Stages and Direct Capture of Neuron-Derived Exosomes from Human Blood Plasma

The measurement of the neurofilament light chain (NFL) in human blood plasma/serum is a promising liquid biopsy for Alzheimer's disease (AD) diagnosis, offering advantages over conventional neuroimaging techniques recommended in clinical guidelines. Here, a controllable nano-brush structure comprising upstanding silicon nanowires coated with indium tin oxide was employed as the sensing substrate. This nano-brush structure was modified with an NFL antibody (NFLAb) via silane coupling and then further connected as the extended gate in a field-effect transistor (EGFET). Notable signal differences emerged within a 2 min timeframe, enabling the label-free differentiation in human blood plasmas among four distinct cohorts: healthy controls, subjective cognitive decline, mild cognitive impairment, and dementia due to AD. Our study indicates that achieving a surface roughness exceeding 400 nm on the modified nano-brush structure enables the effective electrical sensing in our EGFETs. These distinct electrical responses measured via the NFLAb-modified nano-brush EGFETs can be attributed to the combined effects of the captured NFLs and NFL-specific neuron-derived exosomes (NDEs) found in dementia patients, as confirmed by electron spectroscopy for chemical analysis, atomic force microscopy, and scanning electron microscopy. Finally, the potential of quantitatively detecting NDEs on the NFLAb-modified nano-brush structure was demonstrated using spiked solutions containing NFL-specific NDEs from IMR-32 neuroblast cells, wherein concentration-dependent changes were observed in the EGFETs output signal. Our findings show that the NFLAb-modified nano-brush EGFET enables rapid, label-free differentiation between healthy individuals and patients at varying stages of AD.

Advanced extracellular vesicle bioinformatic nanomaterials: from enrichment, decoding to clinical diagnostics

Extracellular vesicles (EVs) are membrane nanoarchitectures generated by cells that carry a variety of biomolecules, including DNA, RNA, proteins and metabolites. These characteristics make them attractive as circulating bioinformatic nanocabinets for liquid biopsy. Recent advances on EV biology and biogenesis demonstrate that EVs serve as highly important cellular surrogates involved in a wide range of diseases, opening up new frontiers for modern diagnostics. However, inefficient methods for EV enrichment, as well as low sensitivity of EV bioinformatic decoding technologies, hinder the use of EV nanocabinet for clinical diagnosis. To overcome these challenges, new EV nanotechnology is being actively developed to promote the clinical translation of EV diagnostics. This article aims to present the emerging enrichment strategies and bioinformatic decoding platforms for EV analysis, and their applications as bioinformatic nanomaterials in clinical settings.

A meta-analysis of neurogenic exosomes in the diagnosis of Alzheimer's disease

Background

Alzheimer's disease (AD) is an irreversible and difficult-to-treat neurodegenerative disease. It is necessary to search for reliable biomarkers for the early diagnosis of AD in a timely and effective manner in high-risk or preclinical AD populations. Studies have shown that neurogenic exosomes in the blood can be effectively used as biomarkers for AD.

Objective

In this meta-analysis, we aimed to find reliable biomarkers (Aβ42, T-tau, and P-tau181 in peripheral blood neurogenic exosomes) for the early diagnosis of AD to provide theoretical support for the early diagnosis of high-risk or preclinical AD populations.

Methods

By searching the literature database, relevant studies on AD diagnostic markers were collected. The study period was from April 1, 2012, to April 1, 2022. The average concentrations of Aβ42, T-tau, and P-tau181 in the exosomes of the AD group and healthy control group were compared using RevMan 5.3 software.

Results

A total of 13 studies were screened, including 842 subjects. Meta-analysis showed that the combined SMD value of neurogenic exosome Aβ42 was 1.70 (95% CI = [1.20,2.20], Z = 6.69, P < 0.05). The combined SMD value of T-tau was 1.02 (95% CI = [0.27,1.77], Z = 2.67, P < 0.05). The combined SMD value of P-tau181 was 1.75 (95% CI = [1.16, 2.35], Z = 5.75, P < 0.05). The levels of neurogenic exosomes Aβ42, T-tau, and P-tau181 in AD patients were significantly higher than those in healthy controls.

Conclusion

Aβ42, T-tau, and P-tau181 in blood neurogenic exosomes can be effectively used as biomarkers for AD and can be applied in the diagnosis, screening, prognosis prediction and disease monitoring of AD.

Application of Single Extracellular Vesicle Analysis Techniques

Extracellular vesicles (EVs) are lipid containers that are actively released by cells and contain complex molecular cargoes. These cargoes include abundant material such as genomes and proteins from cells of origin. They are involved in intercellular communication and various pathological processes, showing excellent potential for diagnosing and treating diseases. Given the significant heterogeneity of EVs in complex physiopathological processes, unveiling their composition is essential to understanding their function. Bulk detection methods have been previously used to analyze EVs, but they often mask their heterogeneity, leading to the loss of valuable information. To overcome this limitation, single extracellular vesicle (SEV) analysis techniques have been developed and advanced. These techniques allow for analyzing EVs' physical information and biometric molecules at the SEV level. This paper reviews recent advances in SEV detection methods and summarizes some clinical applications for SEV detection strategies.

Small-molecule probes from bench to bedside: advancing molecular analysis of drug-target interactions toward precision medicine

Over the past decade, remarkable advances have been witnessed in the development of small-molecule probes. These molecular tools have been widely applied for interrogating proteins, pathways and drug-target interactions in preclinical research. While novel structures and designs are commonly explored in probe development, the clinical translation of small-molecule probes remains limited, primarily due to safety and regulatory considerations. Recent synergistic developments - interfacing novel chemical probes with complementary analytical technologies - have introduced and expedited diverse biomedical opportunities to molecularly characterize targeted drug interactions directly in the human body or through accessible clinical specimens (e.g., blood and ascites fluid). These integrated developments thus offer unprecedented opportunities for drug development, disease diagnostics and treatment monitoring. In this review, we discuss recent advances in the structure and design of small-molecule probes with novel functionalities and the integrated development with imaging, proteomics and other emerging technologies. We further highlight recent applications of integrated small-molecule technologies for the molecular analysis of drug-target interactions, including translational applications and emerging opportunities for whole-body imaging, tissue-based measurement and blood-based analysis.

Emerging nanotechnology for Alzheimer's disease: From detection to treatment

Alzheimer's disease (AD), one of the most common chronic neurodegenerative diseases, is characterized by memory impairment, synaptic dysfunction, and character mutations. The pathological features of AD are Aβ accumulation, tau protein enrichment, oxidative stress, and immune inflammation. Since the pathogenesis of AD is complicated and ambiguous, it is still challenging to achieve early detection and timely treatment of AD. Due to the unique physical, electrical, magnetic, and optical properties of nanoparticles (NPs), nanotechnology has shown great potential for detecting and treating AD. This review provides an overview of the latest developments in AD detection via nanotechnology based on NPs with electrochemical sensing, optical sensing, and imaging techniques. Meanwhile, we highlight the important advances in nanotechnology-based AD treatment through targeting disease biomarkers, stem-cell therapy and immunotherapy. Furthermore, we summarize the current challenges and present a promising prospect for nanotechnology-based AD diagnosis and intervention.

Review of the advances in lipid anchors-based biosensors for the isolation and detection of exosomes

Exosomes are nanoparticles with a bilayer lipid structure that carry cargo from their cells of origin. These vesicles are vital to disease diagnosis and therapeutics; however, conventional isolation and detection techniques are generally complicated, time-consuming, and costly, thus hampering the clinical applications of exosomes. Meanwhile, sandwich-structured immunoassays for exosome isolation and detection rely on the specific binding of membrane surface biomarkers, which may be limited by the type and amount of target protein present. Recently, lipid anchors inserted into the membranes of vesicles through hydrophobic interactions have been adopted as a new strategy for extracellular vesicle manipulation. By combining nonspecific and specific binding, the performance of biosensors can be improved variously. This review presents the reaction mechanisms and properties of lipid anchors/probes, as well as advances in the development of biosensors. The combination of signal amplification methods with lipid anchors is discussed in detail to provide insights into the design of convenient and sensitive detection techniques. Finally, the advantages, challenges, and future directions of lipid anchor-based exosome isolation and detection methods are highlighted from the perspectives of research, clinical use, and commercialization.

Emerging integrated SERS-microfluidic devices for analysis of cancer-derived small extracellular vesicles

Cancer-derived small extracellular vesicles (sEVs) are specific subgroups of lipid bilayer vesicles secreted from cancer cells to the extracellular environment. They carry distinct biomolecules (e.g., proteins, lipids and nucleic acids) from their parent cancer cells. Therefore, the analysis of cancer-derived sEVs can provide valuable information for cancer diagnosis. However, the use of cancer-derived sEVs in clinics is still limited due to their small size, low amounts in circulating fluids, and heterogeneous molecular features, making their isolation and analysis challenging. Recently, microfluidic technology has gained great attention for its ability to isolate sEVs in minimal volume. In addition, microfluidics allows the isolation and detection of sEVs to be integrated into a single device, offering new opportunities for clinical application. Among various detection techniques, surface-enhanced Raman scattering (SERS) has emerged as a promising candidate for integrating with microfluidic devices due to its ultra-sensitivity, stability, rapid readout, and multiplexing capability. In this tutorial review, we start with the design of microfluidics devices for isolation of sEVs and introduce the key factors to be considered for the design, and then discuss the integration of SERS and microfluidic devices by providing descriptive examples of the currently developed platforms. Lastly, we discuss the current limitations and provide our insights for utilising integrated SERS-microfluidics to isolate and analyse cancer-derived sEVs in clinical settings.

Plasmonic metasurface enhanced by nanobumps for label-free biosensing of lung tumor markers in serum

Plasmonic metasurface biosensing has excellent potential in label-free detection of tumor biomarkers. In general, a variety of plasmonic metasurface nanofabrication leads to various degree of metallic surface roughness. However, the metasurface roughness effects on plasmonic sensing of tumor markers have been barely reported. Here we fabricate high-roughness (HR) gold nanohole metasurfaces with nanobumps and investigate their biosensing in comparison with the low-roughness (LR) counterparts. The HR metasurfaces demonstrate the surface sensitivity of multilayer polyelectrolyte molecules, which is 57.0% higher than the LR ones. The HR metasurfaces also illuminate higher immunoassay sensitivity to multiple lung cancer biomarkers, including carcinoembryonic antigen, neuron-specific enolase and cytokeratin fragment 21-1. The highest increasement of tumor marker sensitivity is up to 71.4%. The biosensing enhancement is attributed to the introduction of gold nanobumps on metasurfaces, which provides more hot-spot regions, higher localized near-field intensity and better optical impedance matching. Furthermore, the biosensing of HR metasurfaces effectively covers the threshold values of tumor markers for early lung cancer diagnosis, and is used for the detection of clinical serum samples. The testing deviation is less than 4% compared with commercial immunoassay, which implies promising applications on medical examinations. Our research provides a scientific guide to surface roughness engineering for plasmonic metasensing in the future point-of-care testing.

Label-free plasmonic metasensing of PSA and exosomes in serum for rapid high-sensitivity diagnosis of early prostate cancer

Prostate-specific antigen (PSA) test is widely used to diagnose early prostate cancer (PCa). Its low sensitivity, especially in the gray zone, usually incurs overtreatment or missed diagnosis. As an emerging tumor marker, exosomes have attracted great interest in non-invasive diagnosis of PCa. However, the quick direct detection of exosomes in serum is still a big challenge for convenient screening of early PCa due to their high-degree heterogeneity and complexity. Here we develop the label-free biosensors based on wafer-scale plasmonic metasurfaces, and establish a flexible spectral methodology of exosomes profiling, which facilitates their identification and quantification in serum. We combine the metasurfaces functionalized by anti-PSA and anti-CD63, respectively, and build a portable immunoassay system to detect serum PSA and exosomes simultaneously within 20 min. Our scheme can discriminate early PCa from benign prostatic hyperplasia with a diagnostic sensitivity of 92.3%, which is much higher that of 58.3% for conventional PSA tests. The receiver operating characteristic analysis in clinical trials demonstrates significant PCa distinguishing capability with an area under the curve up to 99.4%. Our work provides a rapid and powerful approach for precise diagnosis of early PCa, and will inspire more exosomes metasensing studies for other early cancer screening.

Analytical device miniaturization for the detection of circulating biomarkers

Diverse (sub)cellular materials are secreted by cells into the systemic circulation at different stages of disease progression. These circulating biomarkers include whole cells, such as circulating tumour cells, subcellular extracellular vesicles and cell-free factors such as DNA, RNA and proteins. The biophysical and biomolecular state of circulating biomarkers carry a rich repertoire of molecular information that can be captured in the form of liquid biopsies for disease detection and monitoring. In this Review, we discuss miniaturized platforms that allow the minimally invasive and rapid detection and analysis of circulating biomarkers, accounting for their differences in size, concentration and molecular composition. We examine differently scaled materials and devices that can enrich, measure and analyse specific circulating biomarkers, outlining their distinct detection challenges. Finally, we highlight emerging opportunities in biomarker and device integration and provide key future milestones for their clinical translation.

Nanosensor-Driven Detection of Neuron-Derived Exosomal Aβ42 with Graphene Electrolyte-Gated Transistor for Alzheimer's Disease Diagnosis

Blood-based tests have sparked tremendous attention in non-invasive early diagnosis of Alzheimer's disease (AD), a most prevalent neurodegenerative malady worldwide. Despite significant progress in the methodologies for detecting AD core biomarkers such as Aβ₄₂ from serum/plasma, there remains cautious optimism going forward due to its controversial diagnostic value and disease relevance. Here, a graphene electrolyte-gated transistor biosensor is reported for the detection of serum neuron-derived exosomal Aβ₄₂ (NDE-Aβ₄₂), which is an emerging, compelling trove of blood biomarker for AD. Assisted by the antifouling strategy with the dual-blocking process, the noise against complex biological background was considerably reduced, forging an impressive sensitivity gain with a limit of detection of 447 ag/mL. An accurate detection of SH-SY5Y-derived exosomal Aβ₄₂ was also achieved with highly conformable enzyme-linked immunosorbent assay results. Importantly, the clinical analysis for 27 subjects revealed the immense diagnostic value of NDE-Aβ₄₂, which can outclass that of serum Aβ₄₂. The developed electronic assay demonstrates, for the first time, nanosensor-driven NDE-Aβ₄₂ detection, which enables a reliable discrimination of AD patients from non-AD individuals and even the differential diagnosis between AD and vascular dementia patients, with an accuracy of 100% and a Youden index of 1. This NDE-Aβ₄₂ biosensor defines a robust approach for blood-based confident AD ascertain.

Label-free microfluidic cell sorting and detection for rapid blood analysis

Blood tests are considered as standard clinical procedures to screen for markers of diseases and health conditions. However, the complex cellular background (>99.9% RBCs) and biomolecular composition often pose significant technical challenges for accurate blood analysis. An emerging approach for point-of-care blood diagnostics is utilizing "label-free" microfluidic technologies that rely on intrinsic cell properties for blood fractionation and disease detection without any antibody binding. A growing body of clinical evidence has also reported that cellular dysfunction and their biophysical phenotypes are complementary to standard hematoanalyzer analysis (complete blood count) and can provide a more comprehensive health profiling. In this review, we will summarize recent advances in microfluidic label-free separation of different blood cell components including circulating tumor cells, leukocytes, platelets and nanoscale extracellular vesicles. Label-free single cell analysis of intrinsic cell morphology, spectrochemical properties, dielectric parameters and biophysical characteristics as novel blood-based biomarkers will also be presented. Next, we will highlight research efforts that combine label-free microfluidics with machine learning approaches to enhance detection sensitivity and specificity in clinical studies, as well as innovative microfluidic solutions which are capable of fully integrated and label-free blood cell sorting and analysis. Lastly, we will envisage the current challenges and future outlook of label-free microfluidics platforms for high throughput multi-dimensional blood cell analysis to identify non-traditional circulating biomarkers for clinical diagnostics.

Neuronal extracellular vesicles and associated microRNAs induce circuit connectivity downstream BDNF

Extracellular vesicles (EVs) have emerged as mediators of cellular communication, in part via the delivery of associated microRNAs (miRNAs), small non-coding RNAs that regulate gene expression. We show that brain-derived neurotrophic factor (BDNF) mediates the sorting of miR-132-5p, miR-218-5p, and miR-690 in neuron-derived EVs. BDNF-induced EVs in turn increase excitatory synapse formation in recipient hippocampal neurons, which is dependent on the inter-neuronal delivery of these miRNAs. Transcriptomic analysis further indicates the differential expression of developmental and synaptogenesis-related genes by BDNF-induced EVs, many of which are predicted targets of miR-132-5p, miR-218-5p, and miR-690. Furthermore, BDNF-induced EVs up-regulate synaptic vesicle (SV) clustering in a transmissible manner, thereby increasing synaptic transmission and synchronous neuronal activity. As BDNF and EV-miRNAs miR-218 and miR-132 were previously implicated in neuropsychiatric disorders such as anxiety and depression, our results contribute to a better understanding of disorders characterized by aberrant neural circuit connectivity.

A hydrogel-based mechanical metamaterial for the interferometric profiling of extracellular vesicles in patient samples

The utility of mechanical metamaterials for biomedical applications has seldom been explored. Here we show that a metamaterial that is mechanically responsive to antibody-mediated biorecognition can serve as an optical interferometric mask to molecularly profile extracellular vesicles in ascites fluid from patients with cancer. The metamaterial consists of a hydrogel responsive to temperature and redox activity functionalized with antibodies to surface biomarkers on extracellular vesicles, and is patterned into micrometric squares on a gold-coated glass substrate. Through plasmonic heating, the metamaterial is maintained in a transition state between a relaxed form and a buckled state. Binding of extracellular vesicles from the patient samples to the antibodies on the hydrogel causes it to undergo crosslinking, induced by free radicals generated via the activity of horseradish peroxidase conjugated to the antibodies. Hydrogel crosslinking causes the metamaterial to undergo fast chiral re-organization, inducing amplified changes in its mechanical deformation and diffraction patterns, which are detectable by a smartphone camera. The mechanical metamaterial may find broad utility in the sensitive optical immunodetection of biomolecules.

Neuronal deletion of nSMase2 reduces the production of Aβ and directly protects neurons

Extracellular vesicles (EVs) have been proposed to regulate the deposition of Aβ. Multiple publications have shown that APP, amyloid processing enzymes and Aβ peptides are associated with EVs. However, very little Aβ is associated with EVs compared with the total amount Aβ present in human plasma, CSF, or supernatants from cultured neurons. The involvement of EVs has largely been inferred by pharmacological inhibition or whole body deletion of the sphingomyelin hydrolase neutral sphingomyelinase-2 (nSMase2) that is a key regulator for the biogenesis of at-least one population of EVs. Here we used a Cre-Lox system to selectively delete nSMase2 from pyramidal neurons in APP/PS1 mice (APP/PS1-SMPD3-Nex1) and found a ∼ 70% reduction in Aβ deposition at 6 months of age and ∼ 35% reduction at 12 months of age in both cortex and hippocampus. Brain ceramides were increased in APP/PS1 compared with Wt mice, but were similar to Wt in APP/PS1-SMPD3-Nex1 mice suggesting that elevated brain ceramides in this model involves neuronally expressed nSMase2. Reduced levels of PSD95 and deficits of long-term potentiation in APP/PS1 mice were normalized in APP/PS1-SMPD3-Nex1 mice. In contrast, elevated levels of IL-1β, IL-8 and TNFα in APP/PS1 mice were not normalized in APP/PS1-SMPD3-Nex1 mice compared with APP/PS1 mice. Mechanistic studies showed that the size of liquid ordered membrane microdomains was increased in APP/PS1 mice, as were the amounts of APP and BACE1 localized to these microdomains. Pharmacological inhibition of nSMase2 activity with PDDC reduced the size of the liquid ordered membrane microdomains, reduced the localization of APP with BACE1 and reduced the production of Aβ_1-40 and Aβ_1-42. Although inhibition of nSMase2 reduced the release and increased the size of EVs, very little Aβ was associated with EVs in all conditions tested. We also found that nSMase2 directly protected neurons from the toxic effects of oligomerized Aβ and preserved neural network connectivity despite considerable Aβ deposition. These data demonstrate that nSMase2 plays a role in the production of Aβ by stabilizing the interaction of APP with BACE1 in liquid ordered membrane microdomains, and directly protects neurons from the toxic effects of Aβ. The effects of inhibiting nSMase2 on EV biogenesis may be independent from effects on Aβ production and neuronal protection.

Nanotechnology-Inspired Extracellular Vesicles Theranostics for Diagnosis and Therapy of Central Nervous System Diseases

Shuttling various bioactive substances across the blood-brain barrier (BBB) bidirectionally, extracellular vesicles (EVs) have been opening new frontiers for the diagnosis and therapy of central nervous system (CNS) diseases. However, clinical translation of EV-based theranostics remains challenging due to difficulties in effective EV engineering for superior imaging/therapeutic potential, ultrasensitive EV detection for small sample volume, as well as scale-up and standardized EV production. In the past decade, continuous advancement in nanotechnology provided extensive concepts and strategies for EV engineering and analysis, which inspired the application of EVs for CNS diseases. Here we will review the existing types of EV-nanomaterial hybrid systems with improved diagnostic and therapeutic efficacy for CNS diseases. A summary of recent progress in the incorporation of nanomaterials and nanostructures in EV production, separation, and analysis will also be provided. Moreover, the convergence between nanotechnology and microfluidics for integrated EV engineering and liquid biopsy of CNS diseases will be discussed.

Extracellular vesicles in Alzheimer’s disease: from pathology to therapeutic approaches

Alzheimer’s disease is a progressive and fatal neurodegenerative disorder that starts many years before the onset of cognitive symptoms. Identifying novel biomarkers for Alzheimer’s disease has the potential for patient risk stratification, early diagnosis, and disease monitoring in response to therapy. A novel class of biomarkers is extracellular vesicles given their sensitivity and specificity to specific diseases. In addition, extracellular vesicles can be used as novel biological therapeutics given their ability to efficiently and functionally deliver therapeutic cargo. This is critical given the huge unmet need for novel treatment strategies for Alzheimer’s disease. This review summarizes and discusses the most recent findings in this field.

Exosome-based approaches in the management of Alzheimer's disease

Alzheimer's disease (AD) has been the most extensively studied neurological disorders that affects millions of individuals globally and is associated with misfolding of proteins in the brain. Amyloid-β and tau are predominantly involved in the pathogenesis of AD. Therapeutic interventions and nanotechnological advancements are useful only in managing the AD symptoms and the cure for this disease remains elusive. Exosomes, originating from most cell and tissue types are regarded as a double-edged sword, considering their roles in the progression and treatment of AD. Exosomes can be manipulated as drug delivery vehicles for a wide range of therapeutic cargos-both small molecules and macromolecules. Herein, we review the roles of exosomes in the pathology, diagnosis, and treatment of AD and highlight their application as a drug carrier to the brain for AD treatment.

Ultrasensitive Detection of C-Reactive Protein by a Novel Nanoplasmonic Immunoturbidimetry Assay

Nanotechnology has attracted much attention, and may become the key to a whole new world in the fields of food, agriculture, building materials, machinery, medicine, and electrical engineering, because of its unique physical and chemical properties, including high surface area and outstanding electrical and optical properties. The bottom-up approach in nanofabrication involves the growth of particles, and we were inspired to propose a novel nanoplasmonic method to detect the formation of nanoparticles in real time. This innovative idea may contribute to the promotion of nanotechnology development. An increase in nanometer particle size leads to optical extinction or density (OD)-value changes in our nanosensor chip at a specific wavelength measured in a generic microplate reader. Moreover, in applying this method, an ultrasensitive nanoplasmonic immunoturbidimetry assay (NanoPITA) was carried out for the high-throughput quantification of hypersensitive C-reactive protein (CRP), a well-known biomarker of cardiovascular, inflammatory, and tumor diseases. The one-step detection of the CRP concentration was completed in 10 min with high fidelity, using the endpoint analysis method. The new NanoPITA method not only produced a linear range from 1 ng/mL to 500 ng/mL CRP with the detection limit reduced to 0.54 ng/mL, which was an improvement of over 1000 times, with respect to regular immunoturbidity measurement, but was also effective in blood detection. This attractive method, combined with surface plasmon resonance and immunoturbidimetry, may become a new technology platform in the application of biological detection.

Silica Inverse Opal Nanostructured Sensors for Enhanced Immunodetection of Extracellular Vesicles by Quartz Crystal Microbalance with Dissipation Monitoring

Extracellular vesicles (EVs) are nanosized circulating assemblies that contain biomarkers considered promising for early diagnosis within neurology, cardiology, and oncology. Recently, acoustic wave biosensors, in particular based on quartz crystal microbalance with dissipation monitoring (QCM-D), have emerged as a sensitive, label-free, and selective EV characterization platform. A rational approach to further improving sensing detection limits relies on the nanostructuration of the sensor surfaces. To this end, inorganic inverse opals (IOs) derived from colloidal self-assembly present a highly tunable and scalable nanoarchitecture of suitable feature sizes and surface chemistry. This work systematically investigates their use in two-dimensional (2D) and three-dimensional (3D) for enhanced QCM-D EV detection. Precise tuning of the architecture parameters delivered improvements in detection performance to sensitivities as low as 6.24 × 10⁷ particles/mL. Our findings emphasize that attempts to enhance acoustic immunosensing via increasing the surface area by 3D nanostructuration need to be carefully analyzed in order to exclude solvent and artifact entrapment effects. Moreover, the use of 2D nanostructured electrodes to compartmentalize analyte anchoring presents a particularly promising design principle.

Modulation of Amyloid-β and Tau in Alzheimer’s Disease Plasma Neuronal-Derived Extracellular Vesicles by Cerebrolysin® and Donepezil

Background: Plasma neuronal-derived extracellular vesicles (NDEV) contain proteins of pathological, diagnostic, and therapeutic relevance. Objective: We investigated the associations of six plasma NDEV markers with Alzheimer’s disease (AD) severity, cognition and functioning, and changes in these biomarkers after Cerebrolysin®, donepezil, and a combination therapy in AD. Methods: Plasma NDEV levels of Aβ 42, total tau, P-T181-tau, P-S393-tau, neurogranin, and REST were determined in: 1) 116 mild to advanced AD patients and in 20 control subjects; 2) 110 AD patients treated with Cerebrolysin®, donepezil, or combination therapy in a randomized clinical trial (RCT). Samples for NDEV determinations were obtained at baseline in the NDEV study and at baseline and study endpoint in the RCT. Cognition and functioning were assessed at the same time points. Results: NDEV levels of Aβ 42, total tau, P-T181-tau, and P-S393-tau were higher and those of neurogranin and REST were lower in mild-to-moderate AD than in controls (p <  0.05 to p <  0.001). NDEV total tau, neurogranin, and REST increased with AD severity (p <  0.05 to p <  0.001). NDEV Aβ 42 and P-T181-tau correlated negatively with serum BDNF (p <  0.05), and total-tau levels were associated to plasma TNF-α (p <  0.01) and cognitive impairment (p <  0.05). Combination therapy reduced NDEV Aβ 42 with respect to monotherapies (p <  0.05); and NDEV total tau, P-T181-tau, and P-S396-tau were decreased in Cerebrolysin-treated patients compared to those on donepezil monotherapy (p <  0.05). Conclusion: The present results demonstrate the utility of NDEV determinations of pathologic and synaptic proteins as effective AD biomarkers, as markers of AD severity, and as potential tools for monitoring the effects of anti-AD drugs.

Cucurbit[7]uril Macrocyclic Sensors for Optical Fingerprinting: Predicting Protein Structural Changes to Identifying Disease-Specific Amyloid Assemblies

In a three-dimensional (3D) representation, each protein molecule displays a specific pattern of chemical and topological features, which are altered during its misfolding and aggregation pathway. Generating a recognizable fingerprint from such features could provide an enticing approach not only to identify these biomolecules but also to gain clues regarding their folding state and the occurrence of pathologically lethal misfolded aggregates. We report here a universal strategy to generate a fluorescent fingerprint from biomolecules by employing the pan-selective molecular recognition feature of a cucurbit[7]uril (CB[7]) macrocyclic receptor. We implemented a direct sensing strategy by covalently tethering CB[7] with a library of fluorescent reporters. When CB[7] recognizes the chemical and geometrical features of a biomolecule, it brings the tethered fluorophore into the vicinity, concomitantly reporting the nature of its binding microenvironment through a change in their optical signature. The photophysical properties of the fluorophores allow a multitude of probing modes, while their structural features provide additional binding diversity, generating a distinct fluorescence fingerprint from the biomolecule. We first used this strategy to rapidly discriminate a diverse range of protein analytes. The macrocyclic sensor was then applied to probe conformational changes in the protein structure and identify the formation of oligomeric and fibrillar species from misfolded proteins. Notably, the sensor system allowed us to differentiate between different self-assembled forms of the disease-specific amyloid-β (Aβ) aggregates and segregated them from other generic amyloid structures with a 100% identification accuracy. Ultimately, this sensor system predicted clinically relevant changes by fingerprinting serum samples from a cohort of pregnant women.

Review on the roles of specific cell-derived exosomes in Alzheimer's disease

Alzheimer's disease (AD) is the sixth leading cause of death worldwide and cannot be effectively cured or prevented; thus, early diagnosis, and intervention are important. The importance of exosomes, membrane-bound extracellular vesicles produced in the endosome of eukaryotic cells, in the development, diagnosis, and treatment of AD has been recognized; however, their specific functions remain controversial and even unclear. With the development of exosome extraction, isolation, and characterization, many studies have focused on exosomes derived from different cells and body fluids. In this study, we summarized the roles of exosomes derived from different body fluids and cells, such as neuron, glial, stem, and endothelial cells, in the development, diagnosis, monitoring, and treatment of AD. We also emphasize the necessity to focus on exosomes from biological fluids and specific cells that are less invasive to target. Moreover, aside from the concentrations of classic and novel biomarkers in exosomes, the size and number of exosomes may also influence early and differential diagnosis of AD.

A degradative to secretory autophagy switch mediates mitochondria clearance in the absence of the mATG8-conjugation machinery

PINK1-Parkin mediated mitophagy, a selective form of autophagy, represents one of the most important mechanisms in mitochondrial quality control (MQC) via the clearance of damaged mitochondria. Although it is well known that the conjugation of mammalian ATG8s (mATG8s) to phosphatidylethanolamine (PE) is a key step in autophagy, its role in mitophagy remains controversial. In this study, we clarify the role of the mATG8-conjugation system in mitophagy by generating knockouts of the mATG8-conjugation machinery. Unexpectedly, we show that mitochondria could still be cleared in the absence of the mATG8-conjugation system, in a process independent of lysosomal degradation. Instead, mitochondria are cleared via extracellular release through a secretory autophagy pathway, in a process we define as Autophagic Secretion of Mitochondria (ASM). Functionally, increased ASM promotes the activation of the innate immune cGAS-STING pathway in recipient cells. Overall, this study reveals ASM as a mechanism in MQC when the cellular mATG8-conjugation machinery is dysfunctional and highlights the critical role of mATG8 lipidation in suppressing inflammatory responses.

The mechanisms underlying mitochondrial quality control are not fully understood. Here the authors identify a switch from degradative to secretory autophagy in the absence of the mATG8-conjugation system, termed Autophagic Secretion of Mitochondria.

Recent advances in optical label-free characterization of extracellular vesicles

Extracellular vesicles (EVs) are complex biological nanoparticles endogenously secreted by all eukaryotic cells. EVs carry a specific molecular cargo of proteins, lipids, and nucleic acids derived from cells of origin and play a significant role in the physiology and pathology of cells, organs, and organisms. Upon release, they may be found in different body fluids that can be easily accessed via noninvasive methodologies. Due to the unique information encoded in their molecular cargo, they may reflect the state of the parent cell and therefore EVs are recognized as a rich source of biomarkers for early diagnostics involving liquid biopsy. However, body fluids contain a mixture of EVs released by different types of healthy and diseased cells, making the detection of the EVs of interest very challenging. Recent research efforts have been focused on the detection and characterization of diagnostically relevant subpopulations of EVs, with emphasis on label-free methods that simplify sample preparation and are free of interfering signals. Therefore, in this paper, we review the recent progress of the label-free optical methods employed for the detection, counting, and morphological and chemical characterization of EVs. We will first briefly discuss the biology and functions of EVs, and then introduce different optical label-free techniques for rapid, precise, and nondestructive characterization of EVs such as nanoparticle tracking analysis, dynamic light scattering, atomic force microscopy, surface plasmon resonance spectroscopy, Raman spectroscopy, and SERS spectroscopy. In the end, we will discuss their applications in the detection of neurodegenerative diseases and cancer and provide an outlook on the future impact and challenges of these technologies to the field of liquid biopsy via EVs.

KIBRA regulates amyloid β metabolism by controlling extracellular vesicles secretion

Background

Previous research has revealed that KIBRA controls secretion of extracellular vesicles (EVs) by inhibiting the proteasomal degradation of Rab27a and EVs play an important role in amyloid β (Aβ) metabolism and transmission during Alzheimer's disease (AD) pathogenesis. Here, we further test the hypothesis that KIBRA regulates Aβ metabolism via the endosomal-lysosomal system.

Methods

We generated KIBRA knockout mice on a 5XFAD background and KIBRA knockdown cells in murine HT22 cells with stably overexpressing APP. Various forms of Aβ and quantification of EVs were analyzed by biochemical methods and nanoparticle tracking analysis, respectively. Multivesicular bodies (MVBs) were visualized by electron microscopy and confocal fluorescent microscopy. In a population-based cohort (n = 1419), KIBRA genotypes and plasma Aβ levels were analyzed using multiple-PCR amplification and Simoa, respectively.

Findings

Multiple forms of Aβ were dramatically attenuated in KIBRA knockout mouse brain, including monomers, oligomers, and extracellular deposition, but KIBRA knockout had no effect on intraneuronal APP C-terminal fragment β (APP-CTFβ)/Aβ levels. KIBRA depletion also decreased APP-CTFβ/Aβ-associated EVs secretion and subsequently enhanced MVBs number. Furthermore, we found that excessive accumulation of MVBs harboring APP-CTFβ/Aβ promoted the MVBs-lysosome fusion for degradation and inhibition of lysosomal function rescued secretion of APP-CTFβ/Aβ-associated EVs. More importantly, whole exon sequencing of KIBRA in a large population-based cohort identified the association of KIBRA rs28421695 polymorphism with plasma Aβ levels.

Interpretation

These results demonstrate that KIBRA regulates Aβ metabolism via controlling the secretion of APP-CTFβ/Aβ-associated EVs.

Funding

National Key R&D Program of China, and National Natural Science Foundation of China.

Expression of Exosome Biogenesis Genes Is Differentially Altered by Aging in the Mouse and in the Human Brain During Alzheimer's Disease

Extracellular vesicles like exosomes are secreted by numerous cell types in a variety of tissues. Exosomes have been implicated in both aging and age-related disorders like Alzheimer's disease (AD). However, how aging and AD affect exosome biogenesis within and across cell types is poorly understood. Moreover, cells acquire characteristics based on tissue niche, but the impact of tissue residence on cell type exosome biogenesis is unknown. We explored the Tabula Muris Senis, Mayo RNA-seq and Rush Religious Order Study/Memory and Aging Project data sets to characterize the cell and tissue-specific effects of aging and AD on genes involved in exosome biogenesis. Specifically, we examined the age-dependent expression (age coefficient) of genes involved in exosome biogenesis (22 genes), exosome cargo (3 genes), and senescence (5 genes). Of the 131 cell populations (cell type × tissue) studied, 95 had at least 1 exosome biogenesis gene affected by age. The most common gene/transcript increased by age was charged multivesicular body protein 2A (CHMP2A) (54 cell populations). The most common gene/transcript decreased by age was syndecan-binding protein (SDCBP) (58 cell populations). The senescence-associated genes cyclin-dependent kinase 1A (CDKN1A) and CDKN2A were not related to changes in CHMP2A and SDCBP and were altered by age in fewer cell populations. Finally, individuals with AD had decreased CHMP2A and increased SDCBP expression, opposite of what is observed during mouse aging in the absence of disease. These findings indicate that exosome biogenesis gene expression is modified by age in many cell populations mostly independent of senescence, and may be further altered in AD.