Role of Tau Protein on Photophysical Properties of Carbon Dots

Abstract

Aggregation of intrinsically disordered Tau protein is a key biomarker of the progressive neurodegenerative disorder Alzheimer's Disease [1]. Although the precise mechanism by which tau aggregates is not well understood, abnormal post-translational modifications of tau have been implicated in the formation of tau aggregates and neurofibrillary tangles. In vitro, Tau aggregation may be detected by the fluorescent Thioflavin T dye, which is limited by non-specific interactions between the dye and other additives and low fluorescence quantum yield. CDs are a highly modifiable nanomaterials with characteristic optical properties and poorly-understood protein interactions. Using the novel fluorescent nanoallotrope, Carbon dots (CDs), we examined an alternative method for facile detection of intrinsically disordered Tau protein. Through photophysical studies of tau protein with two varieties of CDs, we determined that Tau protein decreased the fluorescent intensity of dual-fluorescing CDs to a greater extent than nitrogen-doped CDs after monitoring fluorescence. Tau protein aggregation was also induced by using heparin and this process was monitored by using ThT as well as CD assays. The CDs exhibited similar properties with heparin-aggregated tau samples and non-aggregated tau protein under specific experimental conditions. Data indicate that carbon dots are viable sensors for proteins and could be further optimized for disease biomarker detection and quantification in the development of rapid, sensitive and selective diagnostic assays.