Search Results (14)

We report the development of highly luminescent, bovine serum albumin (BSA)-stabilized gold–silver bimetallic nanoclusters (Au-AgNCs@BSA) as a novel platform for high-sensitivity, ratiometric intracellular temperature sensing. Precise and non-invasive temperature sensing at the nanoscale is crucial for applications ranging from intracellular thermogenesis monitoring to localized hyperthermia therapies. Traditional luminescent thermometric platforms often suffer from limitations such as high cytotoxicity and low photostability. Here, we synthesized Au-AgNCs@BSA via a one-pot aqueous reaction, achieving significantly enhanced photoluminescence quantum yields (PL QYs, up to 18%) and superior thermal responsiveness compared to monometallic counterparts. The dual-emissive Au-AgNCs@BSA exhibit a linear ratiometric fluorescence response to temperature fluctuations within the physiological range (20–50 °C), enabling accurate and concentration-independent thermometry in live cells. Time-resolved PL and Arrhenius analyses reveal two distinct emissive states and a high thermal activation energy (E_a = 199 meV), indicating strong temperature dependence. Silver doping increases radiative decay rates while maintaining low non-radiative losses, thus amplifying fluorescence intensity and thermal sensitivity. Owing to their small size, excellent photostability, and low cytotoxicity, these nanoclusters were applied to non-invasive intracellular temperature mapping, presenting a promising luminescent nanothermometer for real-time cellular thermogenesis monitoring and advanced bioimaging applications. Full article

We developed a highly sensitive solid-state sensor for mercury detection by stabilizing red-sub-nanometric fluorescent gold nanoclusters (AuNC, 0.9 ± 0.1 nm diameter) with bovine serum albumin in a matrix composed of cellulose nanofibrils (CNF) (BSA-AuNC/CNF). The main morphological and optical features of the system were investigated via atomic force/transmission electron microscopy and UV-Vis/fluorescence spectroscopy. The hybrid film (off-white and highly transparent) showed strong photoluminescene under UV irradiation. The latter is assigned to the AuNC, which also increase the ductility of the emitting film, which was demonstrated for high sensitivity Hg²⁺ detection. When used as a sensor system, following AuNC printing on CNF hybrid films, a limit of detection <10 nM was confirmed. What is more, nanocellulose films have a high pore structure and selective separation properties, showcasing a wide range of potential applications in many fields such as water treatment and oil–water separation. Full article

Gold nanoclusters (Au NCs) belong to a class of materials that is highly fluorescent and biocompatible. Bovine serum albumin (BSA) protected gold nanoclusters (BSA-Au NCs) have been extensively used in biological applications due to their easy synthesis and relatively high quantum yield. Therefore, understanding the behavior of BSA-Au NCs in different chemical and physical environments is essential to enhance their application in biological systems. In this study, we investigated the effect of plasmonic nanostructures with different localized surface plasmon resonance (LSPR) wavelengths on the behavior of BSA-Au NCs by recording time-dependent fluorescence spectra in the presence of silver nanoparticles (AgNPs) with various shapes. However, we did not observe any conclusive LSPR-wavelength-dependent fluorescent behavior. Additionally, the fluorescence intensity of BSA-Au NCs exhibited gradual decay under light excitation, even at several hundred μW/cm² in a fluorescence spectrometer, indicating that they are not as photostable as previously assumed. We found further that the photostability of BSA-Au NCs is affected by the wavelength of the incident light (370, 420, 480, and 550 nm), which can be accurately described using bi-exponential decay functions. Our study provides an easy in situ method to evaluate the photostability of Au NCs under different-wavelength light irradiation using a commercial fluorescence spectrometer. Full article

Hydrogen peroxide (H₂O₂) has been a fascinating target in various chemical, biological, clinical, and industrial fields. Several types of fluorescent protein-stabilized gold nanoclusters (protein-AuNCs) have been developed for sensitive and easy detection of H₂O₂. However, its low sensitivity makes is difficult to measure negligible concentrations of H₂O₂. Therefore, to overcome this limitation, we developed a horseradish peroxidase-encapsulated fluorescent bio-nanoparticle (HEFBNP), comprising bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and horseradish peroxidase-stabilized gold nanoclusters (HRP-AuNCs). The fabricated HEFBNP can sensitively detect H₂O₂ owing to its two properties. The first is that HEFBNPs have a continuous two-step fluorescence quenching mechanism, which comes from the heterogenous fluorescence quenching mechanism of HRP-AuNCs and BSA-AuNCs. Second, the proximity of two protein-AuNCs in a single HEFBNP allows a reaction intermediate (•OH) to rapidly reach the adjacent protein-AuNCs. As a result, HEFBNP can improve the overall reaction event and decrease the loss of intermediate in the solution. Due to the continuous quenching mechanism and effective reaction event, a HEFBNP-based sensing system can measure very low concentrations of H₂O₂ up to 0.5 nM and show good selectivity. Furthermore, we design a glass-based microfluidic device to make it easier use HEFBNP, which allowed us to detect H₂O₂ with the naked eye. Overall, the proposed H₂O₂ sensing system is expected to be an easy and highly sensitive on-site detection tool in chemistry, biology, clinics, and industry fields. Full article

The BSA-encapsulated gold nanoclusters (AuNC@BSA) have drawn considerable interest and demonstrated applications as biological sensors. In this study, we demonstrated that the red-emitting AuNC@BSA prepared using a modified procedure fully retained the binding of standard BSA-ligands (small molecule drugs), significantly improving fluorescence detection in some cases due to the red-emission property. Further, we showed that AuNC@BSA efficiently bind a series of aflatoxin-related mycotoxins as well as the aliphatic mycotoxin FB₁, reporting interactions in the nanomolar range by instantaneous emission change at 680 nm. Such red emission detection is advantageous over current detection strategies for the same mycotoxins, based on complex mass spectrometry procedures or, eventually (upon chemical modification of the mycotoxin), by fluorescence detection in the UV range (<400 nm). The later technique yields fluorescence strongly overlapping with the intrinsic absorption and emission of biorelevant mixtures in which mycotoxins appear. Thus, here we present a new approach using the AuNC@BSA red fluorescence reporter for mycotoxins as a fast, cheap, and simple detection technique that offers significant advantages over currently available methods. Full article

Highly biocompatible nanostructures for multimodality imaging are critical for clinical diagnostics improvements in the future. Combining optical imaging with other techniques may lead to important advances in diagnostics. The purpose of such a system would be to combine the individual advantages of each imaging method to provide reliable and accurate information at the site of the disease bypassing the limitations of each. The aim of the presented study was to evaluate biodistribution of the biocompatible technetium-99m labelled bovine serum albumin–gold nanoclusters (^99mTc-BSA-Au NCs) as photoluminescence-SPECT/CT agent in experimental animals. It was verified spectroscopically that radiolabelling with ^99mTc does not influence the optical properties of BSA-Au NCs within the synthesized ^99mTc-BSA-Au NCs bioconjugates. Biodistribution imaging of the ^99mTc-BSA-Au NCs in Wistar rats was performed using a clinical SPECT/CT system. In vivo imaging of Wistar rats demonstrated intense cardiac blood pool activity, as well as rapid blood clearance and accumulation in the kidneys, liver, and urinary bladder. Confocal images of kidney, liver and spleen tissues revealed no visible uptake indicating that the circulation lifetime of ^99mTc-BSA-Au NCs in the bloodstream might be too short for accumulation in these tissues. The cellular uptake of ^99mTc-BSA-Au NCs in kidney cells was also delayed and substantial accumulation was observed only after 24-h incubation. Based on our experiments, it was concluded that ^99mTc-BSA-Au NCs could be used as a contrast agent and shows promise as potential diagnostic agents for bloodstream imaging of the excretory organs in vivo. Full article

Gold nanoclusters (AuNCs), with diameters less than 2 nanometers, have particular fluorescent properties. These nanoclusters can be prepared by microwave-assisted synthesis using BSA (bovine serum albumin) as a template [1]. During the synthesis, Au(III) ions are reduced to Au(I) or Au(0), which are bonded to BSA, forming, thus, Au(I)-BSA complexes and/or AuNCs-BSA, respectively. Here, femtosecond-stimulated Raman spectroscopy (FSRS), an ultrafast nonlinear optical technique, is used to study the vibrational structure of Au(I)-BSA complexes and AuNCs-BSA. FSRS has time resolution comparable to the vibrational period of molecular movements (ps to fs) and energy resolution less than 10 cm⁻¹. Three laser pulses are exploited in a typical FSRS experiment: actinic pulse, Raman pulse and probe pulse [2]. According to our preliminary results, FSRS represents a very promising tool in the investigation of Au(I)-BSA complexes and AuNCs-BSA systems. Full article

Bovine serum albumin-embedded Au nanoclusters (BSA-AuNCs) are thoroughly probed by continuous wave electron paramagnetic resonance (CW-EPR), light-induced EPR (LEPR), and sequences of microscopic investigations performed via high-resolution transmission electron microscopy (HR-TEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray analysis (EDS). To the best of our knowledge, this is the first report analyzing the BSA-AuNCs by CW-EPR/LEPR technique. Besides the presence of Au(0) and Au(I) oxidation states in BSA-AuNCs, the authors observe a significant amount of Au(II), which may result from a disproportionation event occurring within NCs: 2Au(I) → Au(II) + Au(0). Based on the LEPR experiments, and by comparing the behavior of BSA versus BSA-AuNCs under UV light irradiation (at 325 nm) during light off-on-off cycles, any energy and/or charge transfer event occurring between BSA and AuNCs during photoexcitation can be excluded. According to CW-EPR results, the Au nano assemblies within BSA-AuNCs are estimated to contain 6–8 Au units per fluorescent cluster. Direct observation of BSA-AuNCs by STEM and HR-TEM techniques confirms the presence of such diameters of gold nanoclusters in BSA-AuNCs. Moreover, in situ formation and migration of Au nanostructures are observed and evidenced after application of either a focused electron beam from HR-TEM, or an X-ray from EDS experiments. Full article

In medical research the visualization of drug carrier accumulation and release of the loaded drugs in vivo is an important field. In this work, two protein-stabilized gold nanoclusters (Au NCs) as effective fluorescent reporters (FRs) were investigated for labeling of biocompatible chitosan-modified hyaluronic acid based nanocarriers having two different structures. The colloid stability of the labeled carriers was studied by dynamic light scattering and Zeta potential measurements, while the changes in the fluorescence of the lysozyme- (LYZ) and bovine serum albumin (BSA)-stabilized Au NCs were analyzed by spectrofluorimetry and confocal fluorescent microscopy. We found that the labeling was effective with a wide range of marker:carrier mass ratios, and the fluorescence of the NCs and the colloid stability of the complexes were retained. Labeling during preparation and subsequent labeling were compared, and based on composition (nanocluster:carrier mass ratio) and structure of the complex systems we preferred the latter method, as it left the Au NCs free for further modifications. Considering both marker:carrier mass ratios and emission intensities, the LYZ-stabilized Au NCs proved to be better labels. The core-shell type carrier formulations showed increased fluorescence with LYZ-stabilized NCs, presumably from aggregation induced emission. Full article

Fluorescent gold nanoclusters (AuNCs) are envisaged as a novel type of fluorophores. This work reports on the first comparative study investigating the effect of presence/absence/abundance of fatty acids (namely palmitic acid, PA) or other substances (like glycoproteins and globulins) in the protein (bovine serum albumin, BSA) on synthesis and properties of the final AuNCs. The most popular template (BSA) and microwave (MW)-assisted synthesis of AuNCs have been intentionally chosen. Our results clearly demonstrate that the fluorescent characteristics (i.e., fluorescence lifetime and quantum yield) are affected by the fatty acids and/or other substances. Importantly, the as-prepared AuNCs are biocompatible, as determined by Alamar Blue assay performed on Hep G2 cell line. Full article

Novel bovine serum albumin (BSA)-gold nanoclusters with garlic extract modifications (mw_G-BSA-AuNCs) were prepared through microwave-assisted rapid synthesis. The modified nanoclusters were characterized and used for the simple and sensitive detection of Pb²⁺ ions. Both turn-on and turn-off methods were used and compared for Pb²⁺ ion detection. For Pb²⁺ ions, the preparation time for the modified nanoclusters was 10 min, and the detection time for the nanoclusters was 6 min. The modified nanoclusters were stable, and their fluorescence intensities changed by less than 10% in 60 days. The detection limit and linear range for the “off-on” method of mw_G-BSA-AuNCs for Pb²⁺ ion detection were 0.28 and 1–20 nM, respectively. The recoveries of the mw_G-BSA-AuNCs probe used for the detection of the Pb(II) ion in tap water ranged from 93.8% to 102.2%, with an average of 97.1%. The “off-on” method of mw_G-BSA-AuNCs can provide a lower detection limit, higher selectivity, and better recovery than the commonly used “turn-off” methods of mw_BSA-AuNCs for Pb²⁺ ion detection. The proposed method is superior to other methods proposed from 2018 to 2019 because it can provide a shorter preparation time and a lower detection limit with good selectivity. The microwave-assisted novel compound, mw_G-BSA-AuNCs, can be rapidly synthesized in a green manner and can provide a low detection limit, good selectivity, and a simple and fast reaction for Pb²⁺ ion detection. Full article

Screening of illicit drugs for new psychoactive substances—namely cathinone—at crime scenes is in high demand. A dual-emission bovine serum albumin-stabilized gold nanoclusters probe was synthesized and used for quantitation and screening of 4-chloromethcathinone and cathinone analogues in an aqueous solution. The photoluminescent (PL) color of the bovine serum albumin-stabilized Au nanoclusters (BSA-Au NCs) probe solution changed from red to dark blue during the identification of cathinone drugs when excited using a portable ultraviolet light-emitting diodes lamp (365 nm). This probe solution allows the PL color-changing point and limit of detection down to 10.0 and 0.14 mM, respectively, for 4-chloromethcathinone. The phenomenon of PL color-changing of BSA-Au NCs was attributed to its PL band at 650 nm, quenching through an electron transfer mechanism. The probe solution was highly specific to cathinone drugs, over other popular illicit drugs, including heroin, cocaine, ketamine, and methamphetamine. The practicality of this BSA-Au NCs probe was assessed by using it to screen illicit drugs seized by law enforcement officers. All 20 actual cases from street and smuggling samples were validated using this BSA-Au NCs probe solution and then confirmed using gas chromatography–mass spectrometry. The results reveal this BSA-Au NCs probe solution is practical for screening cathinone drugs at crime scenes. Full article

Serum bilirubin is an important biomarker for the diagnosis of various types of liver diseases and blood disorders. A polydopamine/gold nanoclusters composite film was fabricated for the fluorescent sensing of free bilirubin. Bovine serum albumin (BSA)-stabilized gold nanoclusters (AuNCs) were used as probes for biorecognition. The polydopamine film was utilized as an adhesion layer for immobilization of AuNCs. When the composite film was exposed to free bilirubin, due to the complex that was formed between BSA and free bilirubin, the fluorescence intensity of the composite film was gradually weakened as the bilirubin concentration increased. The fluorescence quenching ratio (F₀/F) was linearly proportional to free bilirubin over the concentration range of 0.8~50 μmol/L with a limit of detection of 0.61 ± 0.12 μmol/L (S/N = 3). The response was quick, the film was recyclable, and common ingredients in human serum did not interfere with the detection of free bilirubin. Full article

In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters. Full article