Since the last two decades, protein conjugated fluorescent gold nanoclusters (NCs) owe much attention in the field of medical and nanobiotechnology due to their excellent photo stability characteristics. In this paper, we reported stable, nontoxic and red fluorescent emission BSA-Au NCs for selective detection of L-dopamine (DA) in cerebrospinal fluid (CSF). The evolution was probed by various instrumental techniques such as UV-vis spectroscopy, High resolution transmission electron microscopy (HTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL). The synthesised BSA-Au NCs were showing 4–6 nm with high fluorescent ~8% Quantum yield (QY). The fluorescence intensity of BSA-Au NCs was quenched upon the addition of various concentrations of DA via an electron transfer mechanism. The decrease in BSA-Au NCs fluorescence intensity made it possible to determine DA in PBS buffer and the spiked DA in CSF in the linear range from 0 to 10 nM with the limit of detection (LOD) 0.622 and 0.830 nM respectively. Best of our knowledge, as-prepared BSA-Au NCs will gain possible strategy and good platform for biosensor, drug discovery, and rapid disease diagnosis such as Parkinson’s and Alzheimer diseases.

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Curcumin-conjugated gold clusters (CUR-AuNCs) were synthesized using a "green" procedure and utilized as an anticancer and a bioimaging agent. Curcumin is a well-known anticancer agent, which forms a cluster when reacting with a gold precursor under mild alkali condition. A fluorescence spectroscopy analysis showed that the CUR-AuNCs emitted red fluorescence (650 nm) upon visible light (550) irradiation. Fourier transform infrared spectroscopy analysis confirmed the stretching and bending nature between the gold atoms and curcumin. Meanwhile, transmission electron microscopy analysis showed a cluster of approximately 1-3 nm with a uniform size. Time-resolved fluorescence analysis demonstrated that the red fluorescence was highly stable. Moreover, laser confocal imaging and atomic force microscopy analysis illustrated that a cluster was well distributed in the cell. This cluster exhibited less toxicity in the mortal cell line (COS-7) and high toxicity in the cervical cancer cell line (HeLa). The results demonstrated the conjugation of curcumin into the fluorescent gold cluster as a potential material for anticancer therapy and bioimaging applications.

Background: Kaempferol (K) is a recognized anticancer drug that can conjugate with small-size gold nanoclusters (AuNCs). Materials and methods: K-AuNCs were synthesized and their use as an anticancer drug was explored using A549 lung cancer cells. Colony formation and cell migration assays were carried out. The morphology of the K-AuNCs treated A549 cells was explored using bio-atomic force microscopy. Results: The K-AuNCs were 1-3 nm in diameter and emitted strong fluorescent at 650 nm following excitation at 550 nm. The stretching and bending nature of the K-AuNCs were analyzed by the Fourier transform infrared spectroscopy. The presence of kaempferol in the AuNCs were confirmed by the PL spectroscopy. Conclusion: The synthesized K-AuNCs mainly targeted and damaged the nuclei of the cancer cells. This composite nanocluster was less toxicity to the normal human cell and higher toxicity to the A549 lunch cancer cell and these material is potential for anticancer drug delivery and bio imaging applications.