Fluoreszcens sajátsággal bíró funkcionális arany nanoklaszterek

The dissertation contains the development of mainly one-step "green chemistry" synthesis processes, where the reduction of precursor tetrachloroaurate ions and the stabilization of the resulting nano-objects is mainly achieved by using small molecules. The research includes the study of key experimental conditions (metal ion/ligand molar ratio, pH, temperature, reaction time) and the comprehensive structural and optical characterization of nanodispersions. The aim of my PhD thesis is to investigate the effect of systematic variation of the above-mentioned experimental parameters on the production process and reproducibility of Au NCs. In order to achieve the reduction of metal ions, we utilized newly studied Vitamin B and the hydroxamic acid derivatives of amino acids having aromatic side chain. In addition to the development of syntheses and purification protocols, the potential usefulness of the products obtained was also a priority. On the one hand, the use of the synthesized and characterized blue-emitting Au NCs stabilized with the hydroxamic acid derivatives of the amino acids in sensing areas was proposed. There is a considerable literature on the detection of metal ions with Au NCs, but few publications provide a more detailed understanding of the mechanisms. For the most promising metal ions, where possible, my task was to determine the minimum detectable limit and to interpret the fluorescence (PL) quenching and enhancement processes and to explore their mechanisms. In addition to the development of optical sensors, the preparation of Au NCs with antioxidant property, stabilized with vitamin B derivatives and their structural analysis was also part of my research. In addition, an attempt was made to study the interaction of these latter mentioned Au NCs with human serum albumin using specific measurement techniques (surface plasmon resonance (SPR) spectroscopy, isothermal titration calorimetry (ITC)), for which data are missing in the literature. The main motivation for the PhD thesis was that the study of fluorescent noble metal NCs is a unique research area in Hungary, so we would like to contribute to the expansion of the field with new scientific results. In addition, the importance of sub-nanometer sized structures with tunable fluorescence properties was highlighted by the Nobel Prize in Chemistry 2023

Promising Bioactivity of Vitamin B1-Au Nanocluster: Structure, Enhanced Antioxidant Behavior, and Serum Protein Interaction

In the current work, we first present a simple synthesis method for the preparation of novel Vitamin-B1-stabilized few-atomic gold nanoclusters with few atomic layers. The formed nanostructure contains ca. eight Au atoms and shows intensive blue emissions at 450 nm. The absolute quantum yield is 3%. The average lifetime is in the nanosecond range and three main components are separated and assigned to the metal–metal and ligand–metal charge transfers. Based on the structural characterization, the formed clusters contain Au in zero oxidation state, and Vitamin B1 stabilizes the metal cores via the coordination of pyrimidine-N. The antioxidant property of the Au nanoclusters is more prominent than that of the pure Vitamin B1, which is confirmed by two different colorimetric assays. For the investigation into their potential bioactivity, interactions with bovine serum albumin were carried out and quantified. The determined stoichiometry indicates a self-catalyzed binding, which is almost the same value based on the fluorometric and calorimetric measurements. The calculated thermodynamic parameters verify the spontaneous bond of the clusters along the protein chain by hydrogen bonds and electrostatic interactions

Histidinehydroxamic acid as new biomolecule to produce molecular-like fluorescent gold nanoclusters: Possible mechanisms for metal ion sensing

We firstly demonstrate a new biomolecule, Histidinehydroxamic acid (HisHA), to produce few-atomic fluorescent gold nanoclusters (Au NCs) in aqueous medium. The preparation protocol has been optimized by studying the effect of metal ion/biomolecule molar ratio, metal ion concentration, pH, temperature, reaction time as well as the role of citrate as mild reducing agent on appearance of blue-emitting (λem = 440 nm, λex = 365 nm) molecular-like NCs. Structural studies confirmed that imidazole-N and amino-N of the HisHA stabilize the formed metallic cores. The quantum yield of ~ 4% and fluorescence lifetime of 4.2 ns were determined. Moreover, these NCs show suitable stability under high inert salt (cNaCl = 2.5 M) concentration as well. Verifying its ability to detect metal ions, dual strategies were discovered. We confirmed that the copper ions cause fluorescence quenching (LOD = 2.49 µM) by pushing the higher amount of soft HisHA ligand from the metallic surface and forming complexes with dominantly hydroxamate-[O,O] coordination mode in the aqueous medium. For Zn2+- ions, a “turn-on” sensing mechanism was observed; the smallest detectable amount of Zn2+ is 7.5 µM. Linear increase of the quantum yield (from ~ 4% to ~ 11.5%) was identified above 75 μM of Zn2+ due to the binding of the Zn2+-ions on the cluster surface via hydroxamate-[O,O] donors

Photocatalytic and antimicrobial activity of sulfur functionalized TiO 2 containing composite films

Facile sulfation of TiO2 semiconductor photocatalyst was achieved by a simple grinding and calcination method using elemental sulfur from desulfurization of petroleum. The successful sulfation of the prepared visible-light-active photocatalyst was also proved by infrared and X-ray photoelectron spectroscopic measurements. Photocatalytic tests revealed that the most efficient member of the series has higher photocatalytic activity than TiO2 in the photodegradation of formic acid under both UV and visible-light activation. Moreover, the improved electrokinetic and water dispersibility behaviors of the sulfur-modified photocatalyst allowed the preparation of polyacrylate-based photoreactive thin films with increased photocatalytic activity, strong antimicrobial properties, and improved mechanical behavior

Comparison of minor bleeding complications using dabigatran or enoxaparin after cemented total hip arthroplasty

BACKGROUND: Orally administered chemical thromboprophylactic agents for total hip replacement (THR) have become popular in recent years. Certain clinical trials suggest that the efficacy and the risk of major bleeding after administration of direct thrombin inhibitor dabigatran etexilate are equivalent to the clinical trial comparator, subcutaneous low-molecular-weight heparin enoxaparin. Our aim was to compare and evaluate the incidence of minor haemorrhagic and soft-tissue adverse effects of enoxaparin and dabigatran. MATERIALS AND METHODS: 122 patients who were treated by elective cemented primary THR were enrolled in our quasi-randomised study. Two groups were formed according to which perioperative thromboprophylactic agent was used: 61 patients in enoxaparin group versus 61 patients in dabigatran group. Thigh volume changes, calculated perioperative blood loss, area of haematoma, wound bleeding, duration of wound discharge and intensity of serous wound discharge on postoperative day 3 and day 7 were recorded. RESULTS: The duration and intensity of serous wound discharge differed significantly between the two groups. Duration of wound discharge after drain removal was 2.2 (+/-2.7) days in the dabigatran group and 1.2 (+/-1.9) days in the enoxaparin group (p < 0.05). Significant increase in serous discharge was found in the dabigatran group (p < 0.05) on third and seventh postoperative days compared to the enoxaparin group. CONCLUSION: Both thromboprophylactic agents were found to have appropriate antithrombotic effects after THR. However, dabigatran was associated with an increased incidence of prolonged serous wound discharge, which might cause longer hospitalization and might instigate the use of prolonged antibiotic prophylaxis

Thermodynamic Characterization of the Interaction of Biofunctionalized Gold Nanoclusters with Serum Albumin Using Two- and Three-Dimensional Methods

Fluorescent gold nanoclusters have been successfully used as fluorescent markers for imaging of cells and tissues, and their potential role in drug delivery monitoring is coming to the fore. In addition, the development of biosensors using structure-tunable fluorescent nanoclusters is also a prominent research field. In the case of these sensor applications, the typical goal is the selective identification of, e.g., metal ions, small molecules having neuroactive or antioxidant effects, or proteins. During these application-oriented developments, in general, there is not enough time to systematically examine the interaction between nanoclusters and relevant biomolecules/proteins from a thermodynamic viewpoint. In this way, the primary motivation of this article is to carry out a series of tests to partially fill this scientific gap. Besides the well-known fluorescent probes, the mentioned interactions were investigated using such unique measurement methods as surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). These two-dimensional (at the solid/liquid interface) and three-dimensional (in the bulk phase) measuring techniques provide a unique opportunity for the thermodynamic characterization of the interaction between different gold nanoclusters containing various surface functionalizing ligands and bovine serum albumin (BSA)

Tryptophanhydroxamic Acid-Stabilized Ultrasmall Gold Nanoclusters: Tuning the Selectivity for Metal Ion Sensing

Sub-nanometer-sized gold nanoclusters (Au NCs) were prepared via the spontaneous reduction of [AuCl4]−- ions with a hydroxamate derivative of L-tryptophan (Trp) natural amino acid (TrpHA). The prepared TrpHA-Au NCs possess intense blue emission (λem = 470 nm; λex = 380 nm) with a 2.13% absolute quantum yield and 1.47 ns average lifetime. The Trp-stabilized noble metal NCs are excellent metal ion sensors for Fe3+, but in this work, we highlighted that the incorporation of the hydroxamate functional group with an excellent metal ion binding capability can tune the selectivity and sensitivity of these NCs, which is a promising way to design novel strategies for the detection of other metal ions as well. Moreover, their simultaneous identification can also be realized. By decreasing the sensitivity of our nano-sensor for Fe3+ (limit of detection (LOD) ~11 µM), it was clearly demonstrated that the selectivity for Cu2+-ions can be significantly increased (LOD = 3.16 µM) in an acidic (pH = 3–4) condition. The surface-bounded TrpHA molecules can coordinate the Cu2+ confirmed by thermodynamic data, which strongly generates the linking of the NCs via the Cu2+ ions in acidic pH, and a parallel fluorescence quenching occurs. In the case of Fe3+, the degree of quenching strongly depends on the metal ion concentration, and it only occurs when the NCs are not able to bind more Fe3+ (~10 µM) on the surface, causing the NCs’ aggregation