Diagnosis and management of neurological disorders and trauma can be challenging due to subjective measures, invasive sample collection, and/or inaccessible testing technologies. Ultrasensitive technologies enable the detection and measurement of low-abundance neurological biomarkers in blood, overcoming the limitations of conventional immunoassay systems and detection in cerebrospinal fluid. There is a need for reproducible and scalable ultrasensitive methods for detection of blood-based neurological biomarkers, to enable high-quality research studies and guide clinical use. 

Single-molecule counting technology by Fluxus, Inc. (Sunnyvale, CA, USA) combines integrated optics and microfluidics on a single chip-based system and achieves ultrasensitive detection of biomarkers. Here, we report preliminary performance characteristics for an assay measuring blood-based pTau217, a neurological biomarker associated with amyloid pathology, utilizing Fluxus’ ultrasensitive technology. 

An immunoassay for pTau217 was developed using high-performance antibodies and reagents. Capture antibodies were immobilized on magnetic particles, and detection antibodies conjugated to a proprietary fluorescent reporter construct. Multiple incubation and wash steps were followed by dissociation of the immune complexes and separation of reporter-Ab from the magnetic particles. Released, free-flowing reporter-Ab molecules were injected into the detector device for single-molecule counting.  

Limits of detection (LoD) and quantification (LoQ), dynamic range, linearity, and precision were assessed, and testing in clinical samples with comparison to established methods are ongoing.