A smartphone-assisted portable dual-mode immunoassay of gentamicin based on curcumin nanoparticles and carbon dots.

A smartphone-assisted portable dual-mode immunoassay was constructed based on curcumin nanoparticles (CNPs) and carbon dots (CDs) for gentamicin (GEN) detection. CNPs were labeled with goat anti-mouse IgG (Ab₂) to create a conjugation that coupled dual signals to concentrations of GEN antigens. CNPs were introduced to pH 7.4 water and showed insignificant color and optical responses. When exposed to the high pH environment, the structure of CNPs changed and color and optical properties were restored. Because of the inner filter effect (IFE) between CNPs and CDs, the fluorescence of CNPs at 550 nm quenched the fluorescence of CDs at 450 nm. Colorimetry and ratiometric fluorescence (F_{550 nm}/F_{450 nm}) dual-mode immunoassay linearly correlated with GEN ranged from 10^-4 to 10⁰ µg/mL with a detection limit (LOD) of 8.98 × 10^-5 µg/mL and 4.66 × 10^-5 µg/mL, respectively. This work supplied a portable, sensitive, and specific platform to detect GEN.