Bridging the gaps in Alzheimer's disease biomarker research: From multi-omics integration to point-of-care diagnostics, a comprehensive review.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder, yet its early and definitive diagnosis remains a formidable clinical challenge. Over the past decade, substantial progress has been made in the identification and validation of AD biomarkers across cerebrospinal fluid (CSF), blood, and emerging non-invasive biofluids. The core CSF biomarkers-amyloid-β (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau)-have been integrated into revised diagnostic criteria, while blood-based biomarkers such as plasma p-tau217 and the Aβ42/Aβ40 ratio are approaching clinical readiness. Simultaneously, electrochemical biosensor technologies have demonstrated remarkable detection sensitivity at the femtomolar level, and multi-omics approaches combining metabolomics, lipidomics, proteomics, and epigenomics are revealing new molecular signatures of early AD. Despite these advances, several critical research questions remain unanswered, including how to optimally combine biomarkers across biofluids, how to translate biosensor technology from the laboratory to the clinic, how to integrate multi-omics data into practical diagnostic frameworks, how to validate non-invasive biofluid markers at clinical scale, and how to harmonize blood-based assays for global implementation. This review systematically examines the current state of AD biomarker science, identifies key unresolved challenges, evaluates the most promising existing approaches, and proposes specific methodological strategies to advance the field from discovery to clinical practice.