Nile red derivatives for dual-channel organelle imaging and LPS detection.

A series of Nile red derivatives (N1-N3) were synthesized and systematically investigated in terms of their photophysical properties and sub-cellular imaging capabilities. Among them, N1 exhibited dual-channel fluorescence imaging, localizing predominantly in lipid droplets (LDs) under 488 nm excitation and additionally targeting the endoplasmic reticulum (ER). Notably, prolonged light irradiation induced a dynamic shift in N1 localization from the smooth ER to the rough ER, offering a rare chemical tool to distinguish these ER sub-domains. In contrast, N3, bearing an aliphatic hydrocarbon substituent, selectively stained lysosomes, highlighting the impact of molecular modification on organelle targeting. Furthermore, N1 demonstrated a strong fluorescence turn-on response upon interaction with lipopolysaccharides (LPS), with an 87-fold enhancement in emission intensity. These findings underscore the critical role of structural substitution in tuning the sub-cellular localisation of Nile red analogues and introduce N1 as a promising probe for real-time imaging of ER dynamics and LPS detection.