Background The misfolding and deposition of amyloid beta (Aβ) in human brain is the main hallmark of Alzheimer's disease (AD) pathology. One of the drivers of Alzheimer´s pathogenesis is the production of soluble oligomeric Aβ, which could potentially serve as a biomarker of AD. Methods Given that the diphenylalanine (FF) at the C‐terminus of Aβ fragments plays a key role in inducing the AD pathology, based on the hydrophobic structure of FF, we synthesized a near‐infrared BF2‐dipyrrolmethane fluorescent imaging probe (NB) to detect both soluble and insoluble Aβ. Results We found that NB not only binds Aβ, particularly oligomeric Aβ, but also interposes self‐assembly of Aβ through π‐π interaction between NB and FF. Conclusion This work holds great promise in the early detection of AD and may also provide an innovative approach to decelerate and even halt AD onset and progression.

Fluorescein is a traditional organic fluorescent dye that has the disadvantage of agglomeration-induced fluorescence quenching and photobleaching due to its large hydrophobic conjugate π-π system, which makes them have limitations in many fields of application. A method of polymer modification is revealed to address this issue. In this study, fluorescein molecules were modified by polycaprolactone (PCL) to obtain PCL grafting fluorescein (P x F), and subsequently assembled with PEG-PCL to obtain fluorescent nanoparticles (PPxF).PPxF would realize long term cellular fluorescence imaging. PCL polymerization induces self-assembly, which effectively avoids fluorescence quenching caused by fluorescent molecules aggregation, and at the same time well inhibit the energy transfer with oxygen to improve photostability. This method is a good way to improve the fluorescence properties of fluorescent dyes, to be suitable for all traditional organic fluorescent dyes to greatly improve their fluorescence and hydrophilic properties and enhance their application fields.

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