Bovine Serum Albumin-stabilized Gold Nanoclusters Research Articles

A Turn-On Fluorescent Sensor for Glutathione Based on Bovine Serum Albumin-Stabilized Gold Nanoclusters.

A fluorescence sensor for the detection of glutathione based on the fluorescence recovering of the bovine serum albumin-stabilized gold nanoclusters is reported. This study indicates that glutathione restores the copper-ion-quenched fluorescence by coordinating the bound copper ion in the bovine serum albumin molecule used for stabilizing the gold nanocluster through its sulfydryl. Under the experimental conditions, the fluorescence response showed a linear relationship with the concentration of glutathione over the range from 10 µM to 400 µM. The fluorescence sensor successfully detected glutathione in commercial drug products.

A wide-color-varying ratiometric nanoprobe for detection of norepinephrine in urine samples

Owing to its dual role as a hormone and neurotransmitter, norepinephrine (NE) detection is of great significance to biomedical diagnosis. In the present work, we have explored intense green fluorescence of poly (norepinephrine) (PNE) nanoparticles synthesized by oxidizing NE in alkaline condition, in combination with red fluorescent bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) for naked-eye detection of NE. The effect of sodium hydroxide on the emission behavior of NE was studied. The surface morphology and optical properties of PNE nanoparticles were characterized by UV–Vis, fluorescence, FTIR, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. For ratiometric sensing of NE, red fluorescent BSA-AuNCs were served as an internal reference while NE delivered a new emission peak at 527 nm, resulting in a wide distinguishable color change from strong red into red, pink, orange, and green under a UV lamp. The ratiometric approach was demonstrated to be highly sensitive and selective for NE detection against even structurally similar biomolecules with a detection limit of 49 nmol L−1. Furthermore, the proposed method was successfully applied to determine NE in urine samples.

Chiral recognition of naproxen enantiomers based on fluorescence quenching of bovine serum albumin–stabilized gold nanoclusters

A simple, fast and green method for chiral recognition of S- and R-naproxen has been introduced. The method was based on quenching of the fluorescence intensity of bovine serum albumin–stabilized gold nanoclusters in the presence of naproxen enantiomers. The quenching intensity in the presence of S-naproxen was higher than R-naproxen when phosphate buffer solution at pH7.0 was used. The chiral recognition occurred due to steric effect between bovine serum albumin conformation and naproxen enantiomers. Two linear determination range were established as 7.4×10−7–9.1×10−6 and 9.1×10−6–3.1×10−5molL−1 for both enantiomers and detection limits of 7.4×10−8molL−1 and 9.5×10−8molL−1 were obtained for S- and R-naproxen, respectively. The developed method showed good repeatability and reproducibility for the analysis of a synthetic sample. To make the procedure applicable to biological samples, the removal of heavy metals from the sample is suggested before any analytical attempt.

Gold nanocluster-coated gold nanorods for simultaneously enhanced photothermal performance and stability

Gold nanorods (GNRs) with unique optical properties are interesting nanomaterials, which have been widely explored in biomedical imaging and photothermal therapies. A GNR-based nanocomposite, which was coated with BSA-stabilized gold nanoclusters (GNCs), was successfully fabricated based on the electrostatic interaction between the negatively charged GNCs and the positively charged GNRs. Compared with the un-modified GNRs, this GNC−GNR nanocomposite with a core-satellite structure showed significantly enhanced photothermal performance together with improved shape stability and colloidal stability upon near-infrared irradiation. In addition, BSA as the stabilizer of GNCs can suppress the cytotoxicity of the nanocomposite, which made it well suited for further biological applications.

A gold nanocluster-based fluorescent probe for simultaneous pH and temperature sensing and its application to cellular imaging and logic gates.

Metal nanocluster-based nanomaterials for the simultaneous determination of temperature and pH variations in micro-environments are still a challenge. In this study, we develop a dual-emission fluorescent probe consisting of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs) and fluorescein-5-isothiocyanate (FITC) as temperature- and pH-responsive fluorescence signals. Under single wavelength excitation the FITC/BSA-AuNCs exhibited well-separated dual emission bands at 525 and 670 nm. When FITC was used as a reference fluorophore, FITC/BSA-AuNCs showed a good linear response over the temperature range 1-71 °C and offered temperature-independent spectral shifts, temperature accuracy, activation energy, and reusability. The possible mechanism for high temperature-induced fluorescence quenching of FITC/BSA-AuNCs could be attributed to a weakening of the Au-S bond, thereby lowering the charge transfer from BSA to AuNCs. Additionally, the pH- and temperature-responsive properties of FITC/BSA-AuNCs allow simultaneous temperature sensing from 21 to 41 °C (at intervals of 5 °C) and pH from 6.0 to 8.0 (at intervals of 0.5 pH unit), facilitating the construction of two-input AND logic gates. Three-input AND logic gates were also designed using temperature, pH, and trypsin as inputs. The practicality of using FITC/BSA-AuNCs to determine the temperature and pH changes in HeLa cells is also validated.

Bovine serum albumin-stabilized gold nanoclusters as a fluorescent probe for determination of ferrous ion in cerebrospinal fluids via the Fenton reaction

Gold nanoclusters (AuNCs) stabilized with bovine serum albumin were utilized as a fluorescent probe for ferrous ion. The detection scheme is based on the quenching of the fluorescence of the modified AuNCs by hydroxyl radical (•OH) that is generated in the Fenton reaction between Fe(II) and H2O2. Fe(II) can be quantified in the 0.08 to 100 μM concentration range, and the limit of detection is as low as 24 nM. The method also displays good accuracy and high sensitivity when employed to the determination of Fe(II) in rat cerebrospinal fluids (CSFs). When applied to CSFs of a rat model of Alzheimer’s disease, it revealed enhanced levels of Fe(II) compared to a control, thereby showing the important physiological role of iron(II) in this disease.

Cytotoxicity of BSA-Stabilized Gold Nanoclusters: In Vitro and In Vivo Study.

Gold nanoclusters (Au NCs) are one of the most promising fluorescent nanomaterials for bioimaging, targeting, and cancer therapy due to their tunable optical properties, yet their biocompatibility still remains unclear. Herein, the cytotoxicity of bovine serum albumin (BSA)-stabilized Au NCs is studied by using three tumor cell lines and two normal cell lines. The results indicate that Au NCs induce the decline of cell viabilities of different cell lines to varying degrees in a dose- and time-dependent manner, and umbilical vein endothelial cells which had a higher intake of Au NCs than melanoma cells show more toxicity. Addition of free BSA to BSA-Au NCs solutions can relieve the cytotoxicity, implying that BSA can prevent cell damage. Moreover, Au NCs increase intracellular reactive oxygen species (ROS) production, further causing cell apoptosis. Furthermore, N-acetylcysteine, a ROS scavenger, partially reverses Au NCs-induced cell apoptosis and cytotoxicity, indicating that ROS might be one of the primary reasons for the toxicity of BSA-Au NCs. Surprisingly, Au NCs with concentrations of 5 and 20 nM significantly inhibit tumor growth in the xenograft mice model of human liver cancer, which might provide a new avenue for the design of anti-cancer drug delivery vehicles.

Controlling the self-assembly and optical properties of gold nanoclusters and gold nanoparticles biomineralized with bovine serum albumin

While the size-dependent optical properties of BSA-stabilized gold nanoclusters are well known, the time-dependent growth mechanism remains to be described.

A label-free gold nanocluster fluorescent probe for protease activity monitoring.

Water soluble BSA-stabilized gold nanoclusters (Au NCs) were synthesized with a simple one-pot procedure. The as-prepared Au NCs were able to emit intensive red fluorescence under the excitation of ultraviolet light, and the fluorescence could be quenched by enzymatic hydrolysis. In this contribution, BSA-stabilized Au NCs as novel fluorescent probes were successfully utilized for the detection and real-time monitoring of proteolytic activity of trypsin and chymotrypsin. High performance liquid chromatography-inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and X-ray absorption fine structure were performed to investigate the quenching mechanism, and the results indicated that BSA scaffold degradation caused by enzymatic proteolysis led to the decrease in fluorescence intensity. Furthermore, this method would be potentially extended to the detection of other enzymes with Au NCs stabilized by different biomolecules.

Cu2 + modulated BSA–Au nanoclusters: A versatile fluorescence turn-on sensor for dopamine

In this work, Cu2+ modified BSA stabilized gold nanoclusters (BSA–Au NCs) were fabricated for the fluorescence turn-on detection of dopamine, an important catecholamine neurotransmitter. The fluorescence of BSA–Au NCs was initially quenched by the Cu2+ ion, and then the addition of dopamine molecule causes the retrieval fluorescence by binding with the metal ion and removing it from the surface of BSA–Au NCs. The mode of interaction between metal ion with BSA–Au nanoclusters and dopamine was studied using fluorescence lifetime measurements, circular dichroism and infrared spectroscopy. The developed Cu2+ quenched BSA-Au nanocluster demonstrated high selectivity and sensitivity towards dopamine over other catecholamines and coexisting substances with a limit of detection 0.01μM. The feasibility of the new turn on sensor in different real samples was demonstrated. The recovery of fluorescence by spiked analyte in human serum and urine samples ranged from 92 to 98% attesting the validity of the developed method.

Label-free turn-on fluorescent detection of melamine based on the anti-quenching ability of Hg2+ to gold nanoclusters

In this work, we proposed a facile, environmentally friendly and cost-effective assay for melamine with BSA-stabilized gold nanoclusters (AuNCs) as a fluorescence reader. Melamine, which has a multi-nitrogen heterocyclic ring, is prone to coordinate with Hg2+. This property causes the anti-quenching ability of Hg2+ to AuNCs through decreasing the metallophilic interaction between Hg2+ and Au+. By this method, detection limit down to 0.15µM is obtained, which is approximately 130 times lower than that of the US food and Drug Administration estimated melamine safety limit of 20µM. Furthermore, several real samples spiked with melamine, including raw milk and milk powder, are analyzed using the sensing system with excellent recoveries. This gold-nanocluster-based fluorescent method could find applications in highly sensitive detection of melamine in real samples.

Highly fluorescent gold nanoclusters based sensor for the detection of quercetin

In this contribution, novel luminescent gold nanoclusters were synthesized by utilizing bovine serum albumin as templates with a simple, rapid, and one-pot procedure. The as-prepared gold nanoclusters were highly dispersed in aqueous solution and emitted an intense red fluorescence under UV light (365 nm). They exhibited strong fluorescence and the maximum excitation and emission wavelengths were 480 and 613.5 nm. In addition, the bovine serum albumin-stabilized gold nanoclusters were successfully utilized as novel fluorescent probes for the detection of quercetin for the first time. It was found that the addition of quercetin induced the strong fluorescence intensity of the gold nanoclusters to decrease. The decrease in fluorescence intensity of the gold nanoclusters caused by quercetin allowed the sensitive detection of quercetin in the range of 8.9 × 10−8–1.8 × 10−4 mol L−1. The detection limit for quercetin is 1.8 × 10−8 mol L−1 at a signal-to-noise ratio of 3. The present sensor for quercetin detection possessed a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.

Selective determination of cysteine using BSA-stabilized gold nanoclusters with red emission

Gold nanoclusters (AuNCs) were synthesized by a macromolecules template using bovine serum albumin (BSA) as stabilizer which can emit red photoluminescence under illumination of ultraviolet light. The fluorescence intensity of AuNCs enhanced through decreasing the surface defects of AuNCs modified with cysteine, herein we present a novel fluorometry for determination of trace cysteine. This method with a wider linear range from 2.0 to 800 nmol mL(-1), higher sensitivity (detection limit was 1.2 nmol mL(-1)) and better selectivity has been utilized to determine cysteine content in real samples, and the results were in a good agreement with those determined by electrochemical biosensor. At the same time, the structures of AuNCs and AuNCs-cysteine were characterized by Fourier-transform infrared spectroscopy (FTIR) and high resolution transmission electron microscopy (HRTEM) and the mechanism of the proposed assay for the detection of cysteine has been discussed.

A novel approach for rapid determination of vitamin B12 in pharmaceutical preparations using BSA-modified gold nanoclusters

A simple, sensitive, and selective method based on the fluorescence quenching of BSA-stabilized gold nanoclusters (BSA-AuNCs) for rapid determination of vitamin B12 is developed. The fluorescence emission was measured at λex/λem 370/617 nm in phosphate buffer solution of pH 7.4, and the experimental variables and possible interference were studied. Under optimized conditions, the proposed method allows the determination of vitamin B12 over the range 160.0 ng mL−1 to 38.5 μg mL−1 with a correlation coefficient of 0.998 and a limit of quantification of 100.0 ng mL−1. The proposed method was successfully applied to commercial injection dosage forms. The recovery of the method is in the range of 97.7–102.0% and the relative standard deviation is in the range of 2.0%–5.9%.

Highly sensitive fluorescent detection of trypsin based on BSA-stabilized gold nanoclusters

In this study, fluorescent metal nanoclusters are presented as novel probes for sensitive detection of protease for the first time. The sensing mechanism is based on trypsin digestion of the protein template of BSA-stabilized Au nanoclusters. The decrease in fluorescence intensity of BSA-Au nanoclusters caused by trypsin allows the sensitive detection of trypsin in the range of 0.01–100 μg/mL. The detection limit for trypsin is 2 ng/mL (86 pM) at a signal-to-noise ratio of 3. The present nanosensor for trypsin detection possesses red emission, excellent biocompatibility, high selectivity, and good stability. In addition, we demonstrated the application of the present approach in real urine samples, which suggested its potential for diagnostic purposes.