Diagnostic biomarkers of Alzheimer's disease in Down syndrome

Accurate and highly sensitive detection of Alzheimer's disease-related extracellular vesicles via förster resonance energy transfer

Alzheimer's disease (AD) is the most common neurodegenerative disease in the world and poses a huge challenge to global healthcare. Early and accurate detection of amyloid-β (1-42) (Aβ42), a key biomarker of AD, is crucial for effective diagnosis and intervention of AD. Specific or overexpressed proteins on extracellular vesicles (EVs) describe a close correlation with the occurrence and development of diseases. EVs are a very promising non-invasive biomarker for the diagnosis of AD and other diseases. As a sensitive, simple and rapid analytical method, fluorescence resonance energy transfer (FRET) has been widely applied in the detection of EVs. Herein, we developed a dual labelling strategy for simultaneously detecting EV membrane proteins of Aβ42 and CD63 based on FRET pair consisting of Au nanoclusters (AuNCs) and polydopamine nanospheres (PDANSs). The constructed nanoprobe, termed EVMPFAP assay, could specifically measure the Aβ42 and CD63 on EVs with excellent sensitivity, high specificity and satisfactory accuracy. The limit of detection of EVMPFAP assay was 1.4 × 103 particles mL-1 and the linear range was from 104 to 108 particles mL-1. EVMPFAP assay was successfully used to analyze plasma EVs to distinguish AD and healthy mice. We expect that EVMPFAP assay can be routinely applied for early diagnosis and development-monitoring of AD, thus facilitating the fight against AD.

Preclinical Alzheimer's dementia: a useful concept or another dead end?

The term, preclinical dementia, was introduced in 2011 when new guidelines for the diagnosis of Alzheimer's dementia (AD) were published. In the intervening 11 years, many studies have appeared in the literature focusing on this early stage. A search conducted in English on Google Scholar on 06.23.2022 using the term "preclinical (Alzheimer's) dementia" produced 121, 000 results. However, the label is arguably more relevant for research purposes, and it is possible that the knowledge gained may lead to a cure for AD. The term has not been widely adopted by clinical practitioners. Furthermore, it is still not possible to predict who, after a diagnosis of preclinical dementia, will go on to develop AD, and if so, what the risk factors (modifiable and non-modifiable) might be. This Review/Theoretical article will focus on preclinical Alzheimer's dementia (hereafter called preclinical AD). We outline how preclinical AD is currently defined, explain how it is diagnosed and explore why this is problematic at a number of different levels. We also ask the question: Is the concept 'preclinical AD' useful in clinical practice or is it just another dead end in the Holy Grail to find a treatment for AD? Specific recommendations for research and clinical practice are provided.