Dendritic Platinum Nanoparticles Research Articles

Development of a novel electrochemical biosensor based on plastic antibodies for detection of STEAP1 biomarker in cancer

STEAP1 is a cell surface protein of the STEAP family whose main function focuses on intercellular communication and cell growth. STEAP1 is considered a promising putative biomarker and a candidate target for prostate cancer treatment.For specific and selective detection of STEAP1, a molecularly imprinted polymers (MIP) was developed on a screen-printed electrode (C-SPE) whose surface was modified with a nanocomposite based on carbon nanotubes decorated with dendritic platinum nanoparticles (CNTs- PAH /Pt). Then, the MIPs were produced on the modified C-SPE by electropolymerization of a mixture of STEAP1 and a monomer (pyrrole-2-carboxylic acid). Then, the protein was removed from the polymeric network by enzymatic treatment with trypsin, which created the specific template cavities for further STEAP1 detection. Electrochemical techniques such as EIS and CV were used to follow the chemical modification steps of C-SPE. The analytical performance of the biosensor was evaluated by SWV in PBS buffer and in lysates of neoplastic prostate cancer cells (LNCaP) extracts. The MIP material showing a linear range from 130 pg/ml to 13 µg/ml. Overall, the biosensor exhibits essential properties such as selectivity, sensitivity and reproducibility for its application in medical and clinical research diagnosis and/or prognosis of prostate cancer.

Pressure/colorimetric dual-readout immunochromatographic test strip for point-of-care testing of aflatoxin B1

Immunochromatographic test strip (ITS) for point-of-care testing (POCT) has attracted prominent attention due to the advantages including rapid response, low cost and good portability. Here, we developed a sensitive ITS for detecting aflatoxin B1 (AFB1) by using dendritic platinum nanoparticles (DPNs) as novel pressure/colorimetric dual-readout probes. DPNs-labeled antibody of AFB1 were used as the signal tracer of the immunochromatographic process. After 10-min competitive immunoreaction, black color appeared on the test line of ITS due to the accumulation of DPNs, which was observed visually as a colorimetric readout for qualitation purpose. Furthermore, DPNs with peroxidase-like activity caused decomposition of hydrogen peroxide aqueous solution to produce pressure change signal in vials, which was detected by a hand-held pressure meter for quantitation purpose. With the pressure readout mode, the detection range was 0.05–10 ng mL−1, and the detection limit was 0.03 ng mL−1 (S/N = 3) for AFB1. The proposed ITS was successfully utilized for detecting AFB1 in herbal medicine samples, and the acceptable recoveries of 93.77–114.09% indicated the reliability for real sample detection. It provides a new avenue for POCT with great application potential in various area including drug and food quality control, pollutants monitoring as well as medical diagnosis.

A facile surfactant-assisted synthesis of carbon-supported dendritic Pt nanoparticles with high electrocatalytic performance for the oxygen reduction reaction

Abstract Dendritic platinum (Pt) nanoparticles are successfully anchored on Ketjen Black by a facile synthetic route without organic solvent. The nonionic surfactant Brij 58 is used as a mesopore-forming agent during the in-situ growth of Pt nanoparticles. The dendritic Pt nanoparticles on Ketjen Black exhibit highly efficient electrocatalytic activity for the oxygen reduction reaction. The electrocatalytic activity can be further improved by increasing the Pt loading amount on Ketjen Black. Upon increasing to 31.4 wt% Pt, the half-wave potential and limited-diffusion current density reach 0.887 V and 6.22 mA cm−2, respectively. The as-prepared catalyst shows an ideal four-electron pathway of O2 reduction to H2O and a low H2O2 yield of less than 1% in the potential window of 0.2–0.8 V. Moreover, the catalyst exhibits remarkable long-term durability with the same limiting current density and only a 10.5 mV negative shift in the half-wave potential after 5000 cycles.

Efficient wide range electrochemical bisphenol-A sensor by self-supported dendritic platinum nanoparticles on screen-printed carbon electrode

Abstract A highly sensitive sensor is strategically designed for bisphenol A (BPA) detection. To enable the sensor to meet the requirements of sensitivity and selectivity, dendritic platinum nanoparticles (DPNs) with a high surface area were prepared and directly coated on gold nanoparticles deposited on a screen-printed carbon electrode, followed by the deposition of a polyethyleneimine-phosphatidylcholine (PEI-PC) layer. The PEI-PC layer protects the sensor against interference effects (such as from ascorbic acid, acetaminophen, uric acid, and dopamine) and further enhances the sensitivity. With our sensor, we were able to detect the presence of bisphenol A precisely at the oxidation potential of 0.270 V. The sensor performance in BPA detection using amperometry under the optimized experimental conditions was demonstrated to reveal the two wide dynamic ranges of 0.01–1.0 μM and 1.0 μM–300 μM, with correlation coefficients of 0.9957 and 0.9864, respectively. The detection limit (DL) for BPA was determined to be 6.63 ± 0.77 nM. To examine its reliability, the sensor was evaluated for the detection of BPA in tap water through a recovery study, which paves the way for practical applications.

Colorimetric detection of penicillin G in milk using antibody-functionalized dendritic platinum nanoparticles

A facile colorimetric method for detecting residual penicillin G in milk using amine-immobilized glass vials and dendritic platinum nanoparticles has been developed. Two distinct methods, liquid-phase and vapor-phase deposition, were used to treat a glass vial with 3-aminopropyl triethoxysilane (APTES) to produce amine groups on the internal surface of the vial. A milk solution spiked with penicillin G was introduced into the glass vial and any compounds in the milk containing carboxylic acid groups (including penicillin G) were allowed to bind to the glass surface through the formation of amide bonds. However, subsequently-added antibody-functionalized dendritic platinum nanoparticles were found to bind only to the penicillin G, which provides the specificity of the proposed assay. Addition of 3,3′,5,5′-tetramethylbenzidine (TMB) solution to the glass vial induced color changes owing to the platinum-nanoparticle-mediated oxidation of TMB. The color change could be identified with the naked eye and the limit of detection was found to be 1ng/mL. The observed color change in the glass vial treated with APTES in the vapor phase was higher than that in the liquid phase, which was attributed to the presence of a higher density of accessible amine groups.

Low-Dimensional Carbon Allotropes: Ground- and Excited-State Charge Transfer with NIR-Absorbing Heptamethine Cyanine

Summary At the focal point of our studies are mutual interactions between an anionic heptamethine cyanine and individualized single-walled carbon nanotubes (SWCNTs) or exfoliated nanographene (NG). Here, we report the distinct near-infrared absorption of the heptamethine cyanine, which assists in visualizing the electronic interactions in the ground state with ease and precision. In statistical Raman assays, we conclude from downshifted 2D- and G-modes for SWCNTs, as well as upshifted 2D- and downshifted G-modes for NG, that these electronic interactions result in stable n-doping of SWCNTs and NG. Key to this shift of charge density is the electron-donating character of the heptamethine cyanine. In the excited state, a complete but metastable transfer of charges is accompanied by a radical-ion-pair state that lives for several nanoseconds. Such a time domain has not yet been realized, for example, in NG to date.

Synthesis and Cytotoxicity of Dendritic Platinum Nanoparticles with HEK-293 Cells.

Dendritic platinum nanoparticles (DPNs) have been synthesized from l-ascorbic acid and an amphiphilic non-ionic surfactant (Brij-58) via a sonochemical method. The particle size and shape of the DPNs could be tuned by changing the reduction temperature, resulting in a uniform DPN with a size of 23 nm or 60 nm. The facets of DPNs have been studied by high-resolution transmission electron microscopy. The cytotoxicity of DPNs has been investigated using human embryonic kidney cells (HEK-293), and the biological adaptability exhibited by DPNs has opened a pathway to biomedical applications such as drug-delivery systems, photothermal treatment, and biosensors.

Graphene Paper Decorated with a 2D Array of Dendritic Platinum Nanoparticles for Ultrasensitive Electrochemical Detection of Dopamine Secreted by Live Cells.

To circumvent the bottlenecks of non‐flexibility, low sensitivity, and narrow workable detection range of conventional biosensors for biological molecule detection (e.g., dopamine (DA) secreted by living cells), a new hybrid flexible electrochemical biosensor has been created by decorating closely packed dendritic Pt nanoparticles (NPs) on freestanding graphene paper. This innovative structural integration of ultrathin graphene paper and uniform 2D arrays of dendritic NPs by tailored wet chemical synthesis has been achieved by a modular strategy through a facile and delicately controlled oil–water interfacial assembly method, whereby the uniform distribution of catalytic dendritic NPs on the graphene paper is maximized. In this way, the performance is improved by several orders of magnitude. The developed hybrid electrode shows a high sensitivity of 2 μA cm−2 μm −1, up to about 33 times higher than those of conventional sensors, a low detection limit of 5 nm, and a wide linear range of 87 nm to 100 μm. These combined features enable the ultrasensitive detection of DA released from pheochromocytoma (PC 12) cells. The unique features of this flexible sensor can be attributed to the well‐tailored uniform 2D array of dendritic Pt NPs and the modular electrode assembly at the oil–water interface. Its excellent performance holds much promise for the future development of optimized flexible electrochemical sensors for a diverse range of electroactive molecules to better serve society.

Seed-mediated synthesis of dendritic platinum nanostructures with high catalytic activity for aqueous-phase hydrogenation of acetophenone

This work reports a facile and efficient seed-mediated method for the synthesis of dendritic platinum (Pt) nanoparticles (NPs) at low temperatures of 55–60 °C in water, using L-ascorbic acid as a reducing agent and sodium citrate as a capping agent.It is found that the dendritic Pt NPs (10–150 nm) are composed of tiny Pt nanocrystals, which nucleate and grow through the introduced smaller Pt seeds with diameters of 3–5 nm. Further investigation shows that the dendritic Pt nanostructures display excellent catalytic performance in an aqueous-phase aromatic ketone hydrogenation reaction, including: (i) acetophenone conversion rate of > 90%, with smaller dendritic Pt NPs (10–46 nm) offering a higher conversion efficiency; (ii) high chemoselectivity toward carbonyl group (90.6%–91.5%), e.g., the selectivity to 1-phenylethanol is ∼90.1% with nearly 100% acetophenone conversion for 10 nm dendritic Pt NPs within 60 min, under mild reaction conditions (20 °C, 1.5 bar H2 pressure, and 1.5 mol% catalyst). The high catalytic activity, selectivity and stability of the dendritic Pt nanostructures under the organic solvent-free conditions make them promising for many potential applications in green catalytic conversion of hydrophilic biomass derived compounds.

Facile Detection of Troponin I Using Dendritic Platinum Nanoparticles and Glass Capillary Tube Indicators

A facile method was developed for the detection of Troponin I (TnI) using dendritic platinum nanoparticles and capillary tube indicators. Dendritic platinum nanoparticles were functionalized with TnI antibodies, which were used to capture TnI in human serum. The captured TnI was conjugated to the inner surface of a glass vial, to which a hydrogen peroxide (H2O2) solution was added. After sealing the glass vial with a screw cap containing a silicon septum, a capillary tube containing a drop of ink was inserted through the septum. The catalytic dissociation of H2O2 to water and oxygen increased the pressure inside the glass vial and raised the ink level in the capillary tube. The ink level increased with the platinum nanoparticle concentration, which is proportional to the TnI concentration. The sensitivity of this assay for TnI in human serum after a 5-min dissociation reaction, detected with the naked eye, was 0.1 ng/mL, which was better than the sensitivity of the conventional colorimetric method using the TMB oxidation reaction under the same experimental conditions. A control experiment using alpha-fetoprotein, interleukin-5, and C-reactive protein revealed that the developed method was highly selective for the detection of TnI. Figure 1

Facile detection of Troponin I using dendritic platinum nanoparticles and capillary tube indicators.

A facile method was developed for the detection of Troponin I (TnI) using dendritic platinum nanoparticles and capillary tube indicators. Dendritic platinum nanoparticles were functionalized with TnI antibodies, which were used to capture TnI in human serum. The captured TnI was conjugated to the inner surface of a glass vial, to which a hydrogen peroxide (H2O2) solution was added. After the glass vial was sealed with a screw cap containing a silicon septum, a capillary tube containing a drop of ink was inserted through the septum. The catalytic dissociation of H2O2 to water and oxygen increased the pressure inside the glass vial and raised the ink level in the capillary tube. The ink level increased with the platinum nanoparticle concentration, which is proportional to the TnI concentration. The sensitivity of this assay for TnI in human serum after a 5 min dissociation reaction, detected with the naked eye, was 0.1 ng/mL, which was better than the sensitivity of the conventional colorimetric method using the TMB oxidation reaction under the same experimental conditions. A control experiment using alpha-fetoprotein, interleukin-5, and C-reactive protein revealed that the developed method was highly selective for the detection of TnI.

A Solution Phase Synthesis of Dendritic Platinum Nanoelectrocatalysts with the Assistance of Polyoxyethylene Nonylphenyl Ether

Dendritic platinum nanoparticles (DPNs) with high surface area have attractive electrocatalytic properties. We report an aqueous solution phase synthesis of DPNs in the presence of various amphiphilic molecules (including surfactants) bypassing the use of organic solvents, seeds, templates or other additives and benefiting from low temperatures and short reaction time (Wang in J Am Chem Soc 132: 13636, 2010; Wang in J Am Chem Soc 133: 9674, 2011; Wang in J Am Chem Soc 135: 16762, 2013). Here we extend this concept to develop an economical and effective solution phase synthesis of DPNs by a simple one-step method with the assistance of polyoxyethylene nonylphenyl ether. The developed strategy remarkably simplifies the synthetic procedures compared to the reported ones. The obtained DPNs exhibit enhanced catalytic activity during methanol oxidation reaction in comparison with the commercially available platinum black. Here we report an aqueous solution phase synthesis for dendritic platinum nanoparticles (DPNs) with a high surface area in the presence of polyoxyethylene nonylphenyl ether .

Macroporous carbon decorated with dendritic platinum nanoparticles: one-step synthesis and electrocatalytic properties

Macroporous carbon (MPC) with high pore accessibility and electrical conductivity is of great interest to the electrochemical platform. The development of a simple and efficient route for the direct synthesis of dendritic platinum nanoparticle (DPN) decorated MPC (DPN/MPC) is an interesting challenge, which is highly valuable for electrocatalytic applications. In this study, we propose a very simple route for the one-step synthesis of DPN/MPC in aqueous solution at room temperature without the need for any kind of seed and surfactant to direct the dendritic growth of Pt nanoparticles, which is performed by simply mixing an aqueous solution of K2PtCl4 with MPC and formic acid. The as-prepared DPN/MPC shows high electrocatalytic activities toward the oxidation of methanol and glucose.

Autonomous Movement of Controllable Assembled Janus Capsule Motors

We demonstrate the first example of a self-propelled Janus polyelectrolyte multilayer hollow capsule that can serve as both autonomous motor and smart cargo. This new autonomous Janus capsule motor composed of partially coated dendritic platinum nanoparticles (Pt NPs) was fabricated by using a template-assisted layer-by-layer (LbL) self-assembly combined with a microcontact printing method. The resulting Janus capsule motors still retain outstanding delivery capacities and can respond to external stimuli for controllable encapsulation and triggered release of model drugs. The Pt NPs on the one side of the Janus capsule motors catalytically decompose hydrogen peroxide fuel, generating oxygen bubbles which then recoil the movement of the capsule motors in solution or at an interface. They could autonomously move at a maximum speed of above 1 mm/s (over 125 body lengths/s), while exerting large forces exceeding 75 pN. Also, these asymmetric hollow capsules can be controlled by an external magnetic field to achieve directed movement. This LbL-assembled Janus capsule motor system has potential in making smart self-propelling delivery systems.

One-step and rapid synthesis of “clean” and monodisperse dendritic Pt nanoparticles and their high performance toward methanol oxidation and p-nitrophenol reduction

Well-defined and monodisperse dendritic platinum nanoparticles (DPNs) are successfully prepared by a rapid, one-step, and efficient route with high yield in aqueous solution, wherein neither organic solvents nor surfactants are employed, ensuring the as-made DPNs definitely have "clean" surfaces, allowing them to exhibit high activity for both methanol oxidation and p-nitrophenol reduction. This proposed strategy for simple and facile preparation of "clean" metal nanocatalysts paves the way for accurately evaluating and further improving their intrinsic catalytic activity.

In Vitro Cytotoxicity and Intracellular Bioimaging of Dendritic Platinum Nanoparticles by Differential Interference Contrast (DIC)

Abstract We demonstrated the excellent biocompatibility of dendritic platinum nanoparticles (DPNs) in vitro using a cancer cell line (BT-20) and MTT assay. In addition, a successful observation of DPNs within live cells using differential interference contrast (DIC) microscopy without labelling fluorescent dyes has been achieved.

Rapid and Efficient Synthesis of Platinum Nanodendrites with High Surface Area by Chemical Reduction with Formic Acid

Platinum nanoarchitectures consisting of a large number of edges and corner atoms are highly favorable for enhancing the catalytic performance and efficient utilization of platinum materials. In a recent study, we have shown that Pluronic F127 triblock copolymer can assist the formation of dendritic platinum nanoparticles (Wang, L.; Yamauchi, Y. J. Am. Chem. Soc. 2009, 131, 9152−9153). Herein, we expand this concept to produce platinum nanodendrites (PNDs) with interconnected arms by using various types of nonionic organic molecules. The PDNs with complex nanoarchitectures are produced simply by sonicating treatment of an aqueous solution containing K2PtCl4 precursor and formic acid in the presence of nonionic organic molecules without the need for any template, seed-mediated growth, and additive. As-produced PDNs were shown to be active as nanoelectrocatalysts for electro-oxidation formic acid. The investigated nonionic organic molecules include nonionic surfactants, e.g., Pluronic F127, Brij 700, Tetron...

Block Copolymer Mediated Synthesis of Dendritic Platinum Nanoparticles

Dendritic platinum nanoparticles are straightforwardly synthesized in high yield via a one-step aqueous-phase reaction mediated by Pluronic F127 block copolymer from the reduction of a platinum complex by ascorbic acid without the need for organic solvents, templates, or ion replacements. The proposed method is unique in its simplicity. The as-prepared dendritic platinum nanoparticles possess the highest surface area (56 m(2) g(-1)) of all reported unsupported platinum materials.