Supramolecular nano-sniffers for ultrasensitive detection of formaldehyde.

Supramolecular nanoparticle hybrids for biosensing of analytes have been a major focus due to their tunable
optical and surface properties. Quantum dots-Gold nanoparticle (QDs-GNP) based FRET probes involving turn
on/off principles have gained immense interest due to their specificity and sensitivity. Recent focus is on
applying these supramolecular hybrids for enzyme operated biosensors that can specifically turn-on fluorescence
induced by co-factor or product formed from enzymatic reaction. The present study focuses on locking
and unlocking the interaction between QD-GNP pair leading to differential fluorescent properties. Cationic
GNPs efficiently quenched the anionic QD fluorescence by forming nanoparticle hybrid. Quenching interaction
between QD-GNP pair was unlocked by NADH leading to QD fluorescence turn-on. This phenomenon was
applied for the successful detection of formaldehyde using NAD+ dependent formaldehyde dehydrogenase. The
proposed nano-sniffer could successfully detect formaldehyde from 0.001 to 100000 ng/mL (R2 = 0.9339) by
the turn off-turn on principle. It could also detect formaldehyde in fruit juice and wine samples indicating its
stability and sensitivity in real samples. The proposed nanoprobe can have wide applications in developing
enzyme biosensors in future.