Red pitaya peels-based carbon dots for real-time fluorometric and colorimetric assay of Au3+, cellular imaging, and antioxidant activity.

The synthesis of fascinating multifunctional carbon dots (CDs) attracted immense attention. Here, a facile solvothermal treatment of red pitaya peels in acetic acid produced CDs (designated as ACDs, excitation/emission wavelengths at 357/432 nm). ACDs with high sp2-hybridized carbon and carboxylic group contents can rapidly and selectively reduce Au3+ to Au0, and stabilize produced Au nanoparticles (AuNPs). The synergetic effect of electron transfer from ACDs to Au3+ and inner filter effect (IFE) from ACDs to AuNPs quenches the fluorescence within 30 s. Simultaneously, the resulting AuNPs have a purple color with a maximum absorption at 545 nm for visual detection. Therefore, for the first time, we reported a fluorometric and colorimetric dual-mode sensing system for real-time, highly sensitive and selective detection of Au3+. The fluorescence quenching ratio and absorbance change linearly with the increase of Au3+ concentration in the range of 0.3-8.0 µM and 3.3-60.0 µM with limits of detection (LODs) at 0.072 µM and 2.2 µM, respectively. The assay was applied for Au3+ determination in spiked real water samples with recoveries from 95.5 to 105.0%, and relative standard deviation (RSD) of less than 6.5%. Furthermore, ACDs with good photostability, low cytotoxicity, and excellent biocompatibility were successfully applied for intracellular Au3+ sensing and imaging. In addition, ACDs exhibited an extraordinarily high antioxidant activity, with an IC50 value for DPPH radical scavenging (0.70 µg mL-1) much lower than that of ascorbic acid (4.34 µg mL-1). The proposed strategy demonstrates the outstanding properties of ACDs in chemical and biomedical analysis. Graphical abstract.

Diamino-functionalized metal-organic framework for selective capture of gold ions.

Adsorptive recovery of valuable gold (Au) ions from wastes is vital but still challenged, especially regarding adsorption capacity and selectivity. A novel M - 3,5-DABA metal-organic framework (MOF) adsorbent was prepared via anchoring 3,5-diaminobenzoic acid (3,5-DABA) molecule in the MOF-808 matrix. Benefiting from the positive charge property, dense amino groups (3.2 mmol g-1) and high porosity, the adsorption capacity of M - 3,5-DABA reaches 1391.5 mg g-1 (pH = 2.5) and adsorption equilibrium is attained in 5 min. This amino-based material shows excellent selectivity towards various metal ions, evading the poor selectivity problem of classical thiol groups (e.g. for Ag+, Cu2+, Pb2+ and Hg2+ ions). In addition, the regeneration was easily achieved via using a hydrochloric acid-thiourea eluent. Experimental analysis and density functional theory (DFT) calculation show the amino group works as a reductant for Au(III) ions and meanwhile acts as an active site for adsorbing Au(III) ions together with the µ-OH group. Thus, M - 3,5-DABA can act as a potential adsorbent for Au(III) ions, and our work offers a viable strategy to construct novel MOF-based adsorbents.

Introducing Selectivity on Carbonaceous Material: Removing Noble Salts, Au3+, and Ag+ from Aqueous Media by Nanodiamonds Functionalized with Squaramides.

Nanodiamonds coated with dopamine-squaramide compounds have been prepared by a calcination/esterification synthetic process, which improves the efficiency of this carbonaceous material with respect to non-functionalized nanodiamonds. The modified nanodiamonds show excellent selective coordination of Ag+ and Au3+ cations in a Cd2+, Co2+, Cr3+, Cu2+, Pb2+, and Zn2+ mixture in water. The coordination capacity of the carbonyl squaramide groups with the silver and gold cation is based on purely electrostatic cation-dipole interactions. Overall, it is demonstrated that the conjunction between the nanodiamonds and the organic receptor improves the selectivity of the material toward noble cations.

Fabrication of Au(III) ion-imprinted polymer based on thiol-modified chitosan.

Au(III) ions were selectively extracted from aqueous media using Au(III) ion-imprinted bio-adsorbent based on modified chitosan (Au-CMB). First, 2-mercaptobenzaldehyde-chitosan Schiff base was prepared and interacted with Au(III) ions. The obtained polymeric Au(III) complex was then cross-linked by epichlorohydrin (ECH) before leaching the template Au(III) ions out of the cross-linked matrix. During the synthetic procedures, the obtained chitosan derivatives were characterized by Elemental analysis, FTIR and NMR spectra. Moreover, the crystalline structures along with surface morphology of the fabricated polymeric materials were investigated using X-ray diffraction (XRD) spectra and scanning electron microscope (SEM), respectively. The Au(III) ions uptake studies indicated that the adsorption process was greatly influenced by pH and followed the pseudo-second-order kinetic mechanism. Furthermore, the adsorption was endothermic and the isotherms showed the best fit with Langmuir model with qm 370±0.5 and 195±0.5mgg-1 in case of Au-CMB and NI-CMB, respectively.

Synthesis, characterization and biological activity of a gold(I) triazenide complex against chronic myeloid leukemia cells and biofilm producing microorganisms

ABSTRACT The enhancement of anti-leukemia therapy and the treatment of infections caused by multidrug-resistant pathogens are major challenges in healthcare. Although a large arsenal of drugs is available, many of these become ineffective, and as a result, the discovery of new active substances occurs. Notably, triazenes (TZCs) have been consolidated as a promising class of compounds, characterized by significant biological activity, especially antiproliferative and antimicrobial properties. The aim of this study is the synthesis and characterization of a new triazenide complex of gold (I), as well as the in vitro assessment of its antiproliferative activity against the K562 cell line (Chronic Myeloid Leukemia), and antibacterial activity against bacterial isolates of biofilm-producing coagulase-negative staphylococci. The combination of TZC with gold metal tends to have a synergistic effect against all biofilm-producing isolates, with Minimum Inhibitory Concentration values (MIC) between 32 and 64 µg mL-1. It has also shown activity against K562 cell line, getting an IC50=4.96 µM. Imatinib mesylate (Glivec) was used as reference, with IC50=3.86 µM. To the best of our knowledge, this study represents the first report of the activity of a TZC complexed with gold ion in the oxidation state (I) against microorganisms that produce biofilm and K562 cells.