Fluorescence biosensor based on gold-carbon dot probe for efficient detection of cholesterol

Cardiovascular diseases have raised serious concerns in recent times with a huge number of mortality all over the world. Herein, we report a fluorescence probe, comprising of carbon quantum dots (CD) and gold nanoparticles (AuNP) for efficient sensing of cholesterol, the most important cardio-risk-marker. A simple hydrothermal method has been employed to synthesize the gold-carbon-dot nanohybrid (AuCD). Cholesterol oxidase immobilized AuCD (Ch-AuCD) showed prominent fluorescence emission at the excitation wavelength of 360 nm. Forster resonance energy transfer (FRET) has been observed between Ch-AuCD and graphene oxide with visible fluorescence intensity turn off. This has been recovered by the addition of a range of concentrations of cholesterol which turn on the fluorescence intensity. This 'on-off' mechanism could efficiently detect cholesterol within the concentration range of 10-100 nM (lower detection limit similar to 10 nM). Moreover, selectivity of the probe towards cholesterol has been ascertained by analyzing a range of interfering analytes, viz. ascorbic acid, urea, glucose, galactose and L-cysteine. Thus, we forward this FRET based 'nano-switch' with high selectivity and sensitivity for efficient sensing of cholesterol. Further, ease of detection endorses this fluorescence-based method for real sample analysis, after scrutinizing the allied factors.