A biocompatible fluorescent probe for selective detection of amyloid fibrils.

The misfolding and aggregation of proteins leading to amyloid formation has been linked to numerous diseases, necessitating the development of tools to monitor the fibrillation process. Here, we report an intramolecular charge transfer (ICT) dye, DMNDC, as an alternative to thioflavin-T (ThT), most commonly used for monitoring amyloid fibrils. Using insulin as a model protein, we show that DMNDC efficiently reports on the kinetics of fibril formation. An approximately 70 nm hypsochromic shift along with a large enhancement in emission intensity was observed upon binding of DMNDC to protein fibrils. The aggregation kinetics of insulin was not significantly affected in the presence of DMNDC, suggesting that DMNDC does not inhibit insulin aggregation. Additionally, the efficient cellular internalization and low toxicity of DMNDC make it highly-suited for sensing and imaging of amyloid fibrils in the complex biological milieu.