Insights into the self-aggregating properties of a solvatochromic probe and interaction with β-lactoglobulin

Abstract

A benzothiazole derivative L₁ exhibits water-induced aggregation by solvent switching, which selectively detects β-lactoglobulin (βlg). At the same time, L₂, a nitro-based electron-deficient compound, has been synthesized as a control. The aggregation occurrence has been ascertained by microscopy, spectroscopy, and light scattering studies. Both L₁ and L₂ display solvatochromic effects on solvent polarity variation. This feebly emissive probe (L₁) offers a blue-shifted turn-on response towards βlg in a buffered medium. Selectivity is observed over multiple other related proteins and enzymes contrary to its control compound. L₁ shows a limit of detection of 2.89 ppm towards this milk allergen. The detection ability has been examined in bovine milk, commercial whey protein sources, and a bio-fluidic matrix. Trypsin-triggered enzyme digestion of βlg has also been tracked by the probe. Spectral and molecular docking studies are computed to confirm probe-protein binding. Paper strip experiments are performed to demonstrate the analytical practicability of the probe.