Mercury ion （Hg2＋） pollution exists in water, soil, and food. By interacting with the thiol groups in protein, Hg2＋ ions can ac- cumulate in ways that cause serious damage to the central nervous system and threaten human health and natural environment. Undoubtedly, Hg2＋ ion detection is a significant issue in environment and health monitoring. A variety of sensor platforms for Hg2＋ ion detection based on organic molecules, DNA, oligonucleotides, inorganic materials, etc, have been reported. In this paper, an artificial peptide PHg, with a cluster bio-mineralize sequence （CCY） and a multi-charge hydrophilic sequence is de- signed as a template for the one-step synthesis of a peptide-Au cluster probe. Briefly： the peptide PHg in situ anchors Au ions to form a peptide-Au （I） intermediate and the reaction pH with NaOH is adjusted; alter 12 h incubation at room temperature, the peptide PGg-Au nanocluster probe with red fluorescence is obtained. The probe has a super-small core size of approximately 1.26 nm and a maximum emission peak at 650 rim. The presence of Hg2＋ ions cause the fluorescence of the probe to greatly decrease. Based on the differences in fluorescence intensity of the PHg-Au nanocluster in the absence and presence of Hg2＋ ions, Hg2＋ ions could be quantitatively detected in concentrations ranging from 5 nmol/L to 1 lamol/L. The limit of detection （LOD） is 7.5 nmol/L. Compared with some interference ions such as, K＋, Mg2＋, Ca2＋, Pb2＋, Ni2＋, Fe3＋, and Cue＋, the selectivity was excellent. The sensing of Hg2＋ ion is not affected by the chelate agents： EDTA, which imparts a significant advantage in a range of applications. As a result, a simple, sensitive and oped for the detection of Hg2＋ ions. selective fluorescent assay based on peptide PHg-Au cluster is devel-
Circulating tumor cells(CTCs)are cancer cells that have propagated from primary tumor sites,spreading into the bloodstream as the cellular origin of fatal metastasis,and to secondary tumor sites.Capturing and analyzing CTCs is a kind of‘‘liquid biopsy'of the tumor that provides information about cancer changes over time and tailoring treatment[1].CTC enrichment and detection remains technologically challenging due to their extremely low concentra-
Coating of gold nanoclusters with peptides is an important targeting method in biomedical applications.However, their synthetic method highly influences their targeting ability. Current methods often use harsh reagents and organic solvents to control morphology, which are not preferred for biomedical applications. Recently, several peptides with specific amino acid sequences have successfully been used to reduce Au ions and synthesize biocompatible peptide-covered gold particles in situ.However, the molecular mechanism of peptide-assisted nanocluster formation is yet unclear. Thus, reactive abilities of different amino acids should be studied to improve design of peptides with predetermined amino acid content and consequently, synthesize gold nanoclusters with improved performance. In this theoretical study, we have approximated the reactive abilities of 20 natural amino acids in their neutral state using density functional theory calculations, such as Fukui indices and HOMO/LUMO composition analysis. We have found that the top reducing agents are tryptophan, histidine, and tyrosine, and thestrongest binding can be expected from methionine and cysteine. Further study of the exact reactive sites in these high reactive amino acids provided the deep insight for the peptide design route for the targeted gold nanocluster formation.
Chronic lymphocytic leukaemia （CLL） is a rare blood cancer that always relapses as refractory disease and eventually leads to death. To date, therapeutic options for CLL patients are scarce and there is an urgent need to develop novel chemotherapeutics that are both effective and safe. Gold-containing compounds induce a lethal oxidative and endoplasmic reticulum stress response in cultured and primary CLL cells via inhibition of thioredoxin reductase （TrxR）. However, traditional gold-containing medicines have revealed side effects during clinical applications. Therefore, safer gold-containing drugs are needed to overcome this challenge. In this study, a novel peptide templated gold cluster Au2sSv9 was synthesized and its therapeutic effect on CLL cells was evaluated. This nanocluster could induce cell apoptosis in MEC-1 cells in a dose-dependent manner which correlated with the uptake amount of clusters in cells. As expected, increasing intracellular reactive oxidative species （ROS） in MEC-1 cells was exhibited with the increase of cluster dosage. Further analyses demonstrated the underlying mechanism that the nan- oclusters suppress the activity ofTrxR1, increase the level of intracellular ROS, destroy the mitochondrial membrane potential and finally trigger the mitochondrial apoptotic pathway in MEC-1 cells. Furthermore, the direct interaction between Au2sSv9 clusters and TrxRl was confirmed for the first time by isothermal titration calorimetry. These findings explored the preclinical efficacy and potential mech- anism of gold clusters in CLL therapy and provided a fundamental reference for the development of other novel gold-containing chemotherapeutics to treat CLL.
