Hao-Hua Deng

In Situ Growth of Porous Platinum Nanoparticles on Graphene Oxide for Colorimetric Detection of Cancer Cells

A green approach is proposed for in situ growth of porous platinum nanoparticles on graphene oxide (PtNPs/GO). The resulting nanocomposite has been proven to function as peroxidase mimetics that can catalyze the reaction of peroxidase substrate in the presence of hydrogen peroxide. On the basis of the peroxidase-like activity, we used the PtNPs/GO as a signal transducer to develop a colorimetric assay for the direct detection of cancer cells. By using folic acid as a recognition element, a total of 125 cancer cells (MCF-7) can be distinguished by naked-eye observation. We envision that this nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine.

Fluorescent hydrogen peroxide sensor based on cupric oxide nanoparticles and its application for glucose and L-lactate detection

A novel fluorescent hydrogen peroxide sensor was developed based on the peroxidase-like activity of cupric oxide nanoparticles. Cupric oxide nanoparticles effectively catalyzed the decomposition of hydrogen peroxide into hydroxyl radicals. Then terephthalic acid was oxidized by hydroxyl radical to form a highly fluorescent product. The linear range of hydrogen peroxide estimated to be 5.0 × 10(-6)-2.0 × 10(-4)M with a detection limit of 3.4 × 10(-7)M. Moreover, this detection system enabled the sensing of analytes which can enzymatically generate hydrogen peroxide. By coupling the oxidation of glucose or L-lactate catalyzed by their corresponding oxidase enzymes with terephthalic acid oxidation catalyzed by cupric oxide nanoparticles, sensitive assays of glucose and l-lactate with detection limits of 1.0 × 10(-6) and 4.5 × 10(-8)M were realized. The successful applications of this approach in human serum samples have also been demonstrated.

Choline and acetylcholine detection based on peroxidase-like activity and protein antifouling property of platinum nanoparticles in bovine serum albumin scaffold

Platinum nanoparticles (PtNPs) in the scaffold of bovine serum albumin (BSA) through biomineralization are found to possess excellent peroxidase-like activity that can catalyze N-ethyl-N-(3-sulfopropyl)-3-methylaniline sodium salt (TOPS) coupled with 4-amino-antipyrine (4-AAP) by the action of hydrogen peroxide to give an obvious purple product. Based on this phenomenon, acetylcholinesterase (AChE) and choline oxidase (ChOx) are used to catalyze ACh and choline to form the active product H2O2 and the as-produced H2O2 is detected optically. Owning to the protection effect of the protein shell, BSA-PtNPs turn out to be very stable and preserve the catalytic activity in the presence of protein and even in the real plasma samples. This protein antifouling property makes the BSA-PtNPs suitable for a wide range of applications in sensors for biological samples. Choline in infant formula and ACh in plasma have been successfully detected.

Colorimetric detection of sulfide based on target-induced shielding against the peroxidase-like activity of gold nanoparticles

Colorimetric recognition and sensing of sulfide with high sensitivity was proposed based on target-induced shielding against the peroxidase-like activity of bare gold nanoparticles. Significant features of the new assay system are its simplicity and cost-effectiveness. The recognition of sulfide by bare gold nanoparticles can be fulfilled in a few seconds and the assay can be accomplished in about 10 min. Furthermore, the new assay system does not require surface modification of GNPs to obtain the specificity for sulfide, and a salt-induced aggregation step is not needed. The detection limit of this method for sulfide was 80 nM. These features make this sensor a potentially powerful tool for the quantitative determination of sulfide in water samples.

Methionine-directed fabrication of gold nanoclusters with yellow fluorescent emission for Cu2+ sensing

In the past few years, fluorescent gold nanoclusters (AuNCs) have gained much attention in many areas of physics, chemistry, materials science, and biosciences due to their unique physical, electrical, and optical properties. Herein, we reported for the first time the synthesis of water soluble, monodispersed AuNCs by using methionine both as a reductant and a stabilizer. The synthetic process is green and simple, and the resulting AuNCs capped by methionine (Met-AuNCs) would be biocompatible with bioorganisms. UV-visible absorption, photoluminescence, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) were carried out to demonstrate the chemical composition and optical properties of the as-prepared Met-AuNCs. The Met-AuNCs possess many attractive features including intense yellow fluorescence (emission maximum at 530nm), a long fluorescence lifetime (181ns and 1651ns), high colloidal stability (pH-, temperature-, salt- and time-stability), and a large Stokes shift (110nm), holding great promise as late-model analytical tools for life science and environmental studies. Moreover, the as-synthesized Met-AuNCs can serve as an efficient fluorescent probe for selective detection of Cu(2+) by fluorescence quenching. The limit of detection for Cu(2+) was determined to be 7.9nM and linear response over the Cu(2+) concentrations range from 50nM to 8μM. Furthermore, the new-constructed probe allows simple and rapid detection of the concentrations of Cu(2+) in soil, with results demonstrating its great feasibility for the determination of copper in real samples.

Water-soluble gold nanoclusters prepared by protein-ligand interaction as fluorescent probe for real-time assay of pyrophosphatase activity.

This paper reports a new and facile method for the synthesis of water-soluble thiolate-protected AuNCs via protein-ligand interaction. Using 3-mercaptopropionic acid (MPA) as a model ligand and bovine serum albumin (BSA) as a model protein, water-soluble AuNCs (BSA/MPA-AuNCs) with intense orange-yellow fluorescent emission (quantum yield=16%) are obtained. Results show that AuNCs produced with this method have hydrophobic interactions with BSA. The synthetic strategy is then successfully extended to produce water-soluble AuNCs protected by other thiolates. Moreover, a sensitive and eco-friendly sensing system is established for detection of the activity of inorganic pyrophosphatase (PPase), which relies on the selective coordination of Fe(3+)with BSA/MPA-AuNCs, the higher affinity between pyrophosphate (PPi) and Fe(3+), and the hydrolysis of PPi by PPase. A good linearity between the fluorescence intensity and PPase activity within the range from 0.1 to 3U/L is found, with a detection limit down to 0.07U/L. Additionally, the fluorescent assay developed here is utilized to assay the PPase activity in real biological samples and as well as to evaluate PPase inhibitor, illustrating the great potential for biological analysis.

Colorimetric sensor based on dual-functional gold nanoparticles: analyte-recognition and peroxidase-like activity.

A novel colorimetric sensor based on the interaction ability with specific analytes and peroxidase-like activity of gold nanoparticles was established in this work. Combining the high-affinity binding between bare gold nanoparticles and melamine with signal amplification procedure based on the catalytic activity of gold nanoparticles for oxidation of TMB, melamine with the concentration as low as 0.02 mg/L can be easily distinguished by naked-eye observation. Such system can be adapted through carefully-controlled surface modifications of gold nanoparticles for determination of other targets.

Synthesis and Peroxidase‐Like Activity of Salt‐Resistant Platinum Nanoparticles by Using Bovine Serum Albumin as the Scaffold

A green approach is proposed for the synthesis of Pt nanoparticles (PtNPs) in the bovine serum albumin (BSA) scaffold through biomineralization. The resulting BSA–PtNPs have been proved to function as peroxidase mimics that can catalyze the reaction of various peroxidase substrates in the presence of H2O2. Kinetic studies indicate that BSA–PtNPs have a much higher affinity for H2O2 than the NPs of other Pt‐based peroxidase mimics. Furthermore, the BSA shell plays an important role in promoting the robust stability of PtNPs. Even in high ionic strength environment (2 M NaCl), the catalytic activity can be well preserved. These excellent properties make the BSA–PtNPs an ideal candidate for a wide range of potential applications as peroxidase mimics.

An IMPLICATION logic gate based on citrate-capped gold nanoparticles with thiocyanate and iodide as inputs

Herein we developed an IMPLICATION logic gate based on citrate-capped AuNPs by employing thiocyanate (SCN(-)) and iodide (I(-)) as inputs, and devised a colorimetric sensor for the determination of I(-) with good selectivity and sensitivity. To the best of our knowledge, this is the first example in which two species of anions serve as inputs to obtain visually observed Boolean outputs. Under the optimum conditions, 0.8 μM I(-) could induce a significant color change and be recognized by the naked eye. The detection limit is 50 nM by using UV-vis spectroscopy.

Determination of tannic acid based on luminol chemiluminescence catalyzed by cupric oxide nanoparticles

In this study, it was found that tannic acid could inhibit the chemiluminescence (CL) intensity of luminol–H2O2–cupric oxide nanoparticles significantly. Based on this inhibition effect, a novel and highly sensitive flow injection method with inhibited chemiluminescence was developed for the determination of tannic acid. Under optimum conditions, the net CL intensity was proportional to the concentration of tannic acid over the range of 10–100 nM and the detection limit was 2.6 nM. The relative standard deviation (RSD) for six repeated determinations of 80 nM tannic acid was 2.8%. Note that this method has been successfully used for the analysis of tannic acid in real Chinese gall samples.