Illustration of nerve cells affected by Alzheimer's disease showing amyloid plaques amongst neurons and neurofibrillary tangles. Kateryna Kon/SPL/Getty Images

A light-emitting probe can selectively bind to clumps of beta-amyloid peptides, small proteins that are toxic and destroy neurons in the brain, that lead to Alzheimer’s disease1. This binding gives off light that shifts towards red, that show where the clumped proteins are in the brain.

The probe could be used to design a non-invasive and inexpensive imaging technique to detect Alzheimer’s, says a team at the CSIR-Indian Institute of Chemical Biology in Kolkata.

Fluorescent probes used now cannot selectively bind to beta amyloid peptides in the brain, resulting in false detection.

In search of smarter peptide-detecting agents, the scientists, led by Surajit Ghosh, synthesised five fluorescent probes – RM-24 to RM-28. They carried out molecular docking studies and experiments to test their efficiency in detecting beta-amyloid 42, the most toxic form of the peptide aggregates.

The team, which included researchers at the Indian Institute of Technology Jodhpur in Rajasthan, found that RM-27 and RM-28 bound to the peptide aggregate and showed a significant change in emission intensity. The rest showed weak or no emission.

Of the probes, RM-28 displayed the maximum increase in emission intensity. It is non-toxic and only bound to the beta-amyloid 42. It also remained stable up to an hour in human plasma and at physiological pH levels.

In the brain of Alzheimer’s afflicted mice, this probe crossed the blood-brain barrier and detected the beta-amyloid aggregate in the hippocampus, the seat of memory and cerebral cortex, in the outer layer of the brain.