Gold Nanoparticles Based Enzyme Biosensor for the Detection of Chloramphenicol

Chronic use of chloramphenicol (CAM) antibiotic leads to anaemia and bone marrow suppression resulting in 40 – 50% mortality. Hence, there is a need to develop an economical, fast and convenient method to detect CAM in milk, honey, shrimp and other aquaculture products. In the current method, coenzyme A was used to indirectly quantify CAM (since it is the cofactor product of the acetylation reaction of CAM). Coenzyme A (CoASH) was used to stabilize gold nanoparticles which were characterized by studying their extinction spectra. The reductant concentration and synthesis time were optimized. With optimized parameters the proposed system could detect CoASH up to 0.1 nM in buffer, with a linear range of detection from 0.1 μM to 1 mM

Photon induced quantum yield regeneration of cap-exchanged CdSe/CdS quantum rods for ratiometric biosensing and cellular imaging

Full water-dispersion of commercial hydrophobic CdSe/CdS core/shell quantum rods (QRs) was achieved by cap-exchange using a dihydrolipoic acid zwitterion ligand at a low ligand:QR molar ratio (LQMR) of 1000. However, this process almost completely quenched the QR fluorescence, greatly limiting its potential in downstream fluorescence based applications. Fortunately, we found that the QR fluorescence could be recovered by exposure to near ultra-violet to blue light radiation (e.g. 300–450 nm). These “reborn” QRs were found to be compact, bright, and stable, and were resistant to non-specific adsorption, which make them powerful fluorescent probes in broad biomedical applications. We demonstrated their potential in two model applications: first, the QRs were conjugated with His8-tagged small antibody mimetic proteins (also known as Affimers) for the sensitive detection of target proteins via a Förster resonance energy transfer (FRET) readout strategy and second, the QR surface was functionalized with biotins for targeted imaging of cancer cells

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