Subtle Hydrophobicity‐Triggered Vesicle Modulation for Label‐Free Rapid Detection of Native Fatty Acids and Steroids

Abstract Rapid and precise detection of fatty acids (FAs) and steroids has always been challenging and unmet, primarily because of their close similarities in molecular weights, functionalities, chemical structures, and properties. The conventional technique such as gas chromatography‐mass spectrometry (GCMS), requires derivatization of FAs and necessitate complex setups, which are expensive and time‐consuming procedures. Herein, this study has constructed a gemini lipidoid (GL), which does not assemble unless triggered by external hydrophobic molecules. This unique hydrophobicity‐dependent vesicle formation enables detection of hydrophobic bioanalytes by optically monitoring the subtle changes in self‐assembly formation, precluding any pretreatments. Notably, FAs having different chain lengths, unsaturation, and, most importantly, their geometrical ( cis‐trans ) isomers are efficiently differentiated without chemical modification even in complex serum media. The sensing platform holds strong potential for addressing real‐world challenges, including rapidly assessing the quality of edible oils with a certain amount of trans FAs contamination, and phenotypic patterning of drug‐resistant bacteria based on their membrane lipid profile. These applications highlight the sensor's versatility and broad potential across clinical diagnostics, food quality control, and microbiological research. Overall, the sensing system can be a potential platform for hypothesis‐free screening of various hydrophobic biomolecules deficits of any specific interacting groups using optical signals.