Ultrasmall Platinum Research Articles

Stabilization of Ultrasmall Platinum Nanoparticles by Nitrogen-Doped Carbon: Implications for Catalysis and Electrocatalysis

Stabilization of Ultrasmall Platinum Nanoparticles by Nitrogen-Doped Carbon: Implications for Catalysis and Electrocatalysis

Tumor-permeated ATP-based size-controllable immunogenic cell death amplifier remodel immunosuppressive microenvironment to boost cancer immunotherapy

Increase extracellular adenosine triphosphate (ATP, a necessary eat me signal for ICD) is a facile way to amplify immunogenic cell death (ICD) cascade for cancer immunotherapy. However, it is still challenging for intratumoral delivery ATP due to complicated enzyme environment in the whole body. Furthermore, tumor immunosuppressive microenvironment (TIM) also hampers the function of mature DCs and limit the activation of immune response. To overcome these drawbacks, a tumor-permeated ATP-based immunogenic cell death amplifier (NABP@SNCs) is fabricated for the first time. (Phenylboronic acid-polyethylene glycol-phenylboronic acid) PBA-PEG-PBA stabilized ultrasmall platinum nanoparticles (ABP) is constructed and interacted with ATP through borate ester bond. Indoleamine 2, 3-dioxygenase 1 (IDO1) inhibitor NLG919 and ABP are co-wrapped with MMP-2 sensitive framework to form NABP@SNCs. NABP@SNCs can not only protect ATP degradation but also release small sized ABP under MMP-2 microenvironment for tumor penetration. Interestingly, ATP can also be released into extracellular regions in tumor acidic pH and act as ‘eat me signal’ for DCs maturation. Synergistically ICD activation by BP (PBA-PEG-PBA stabilized ultrasmall platinum nanoparticles) and TIM reversal by NLG919 can facilitate T lymphocyte cells infiltration for immune response. NABP@SNCs can significantly regress tumor growth and reduce pulmonary metastasis for improved cancer immunotherapy.

Development of an Ultrasmall and Biocompatible Platinum Nanozyme Encapsulated by Zwitterionic Dendrimer for Highly Sensitive Detection of Glucose.

Many kinds of noble metal nanoparticles can mimic the peroxidase-like function of horseradish peroxidase, which results in their wide applications in bio-related detection and drug delivery. However, those metal nanoparticles usually have low stability and reduced catalytic activity in biological complex medium. Herein, a zwitterionic peroxidase-like enzyme has been developed, which has high stability in fibrinogen solutions and high sensitivity for glucose detection. Maleic anhydride, cysteamine, and zwitterionic peptide EKEKC (EK-5) were used to modify generation 5 poly(amido amine) dendrimers (G5 PAMAM) to prepare zwitterionic dendrimer G5MEKnC with nonfouling properties. Finally, the G5MEKnC-encapsulated platinum nanoparticles (Ptn-G5MEK50C) were prepared by entrapping the platinum nanoparticles (1.40 nm) in the catalytic centers in the interior of G5MEK50C. Pt55-G5MEK50C showed high stability in the buffer solution and the fibrinogen solution within 4 days. They also displayed high biocompatibility toward HeLa cells based on cytotoxicity results and morphological observations. Furthermore, the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine with H2O2 by Pt55-G5MEK50C followed the Michaelis-Menten equation, which confirmed their peroxidase-like properties. The catalytic mechanism was due to the generation of •OH from H2O2. More importantly, the peroxidase-like ability of Pt55-G5MEK50C was successfully used to establish a method for the determination of glucose concentration with a broad linear range of 1-2000 μM and a low detection limit of 0.1 μM. This method was highly accurate for the determination of glucose concentration in plasma. The zwitterionic dendrimer template enhanced the properties of Pt55-G5MEK50C. Taken together, a new kind of biocompatible nanozyme has been developed and successfully used for the sensitive detection of glucose in bio-related medium.

Construction of ultra-small Pt nanoparticles @Ti3C2Tx MXene electrocatalyst for efficient and stable electrochemical hydrodechlorination of chloramphenicol

Halogenated antibiotics, especially chloramphenicol (CAP), are abused in human and poultry treatment of bacterial infections, resulting in a rising environmental risk posed by antibiotic-resistant bacteria and genes. Therefore, the degradation of CAP before release by gentle and efficient electrochemical hydrodechlorination (EHDC) has attracted tremendous interest. Platinum group metals are irreplaceable in EHDC but suffer from high cost and scarcity, necessitating strategies of reducing the particle size to increase the atom utilization efficiency. Here, ultra-small platinum nanoparticles @ Ti3C2Tx MXene ([email protected]) electrocatalyst was constructed through a general and facile approach. Benefitting from the synergy of electron transfer and atomic H*, 1% [email protected] could almost completely reduce CAP within 90 min (98.7%), and retained impressive removal efficiency (86.5%) after 25 recycling tests. Remarkably, the rate constant (k) contributed by unit mass of metal (k/ratio) of 1% [email protected] is 75 times higher than that of Commercial Pt/C. Two plausible degradation pathways on 1% [email protected] are deduced from the analysis of intermediate products. Besides, 1% [email protected] can be extended to actually remove the high content of CAP in the urine of hospital patients. This work paves an avenue for rational design of noble metal electrocatalysts on MXene and their applications in hydrodechlorination.

Hypoxia-Responsive Platinum Supernanoparticles for Urinary Microfluidic Monitoring of Tumors.

Cancer has become a leading cause of morbidity and mortality, and there is an increasing need for versatile tools to enable sensitive, simple and early cancer monitoring. Here, we report platinum supernanoparticles as an exogenous nanosensor which can dissociate into ultrasmall platinum nanoclusters (PtNCs) under tumor-specific hypoxia conditions. The resulting PtNCs can be filtered through the kidney as urinary reporters to be quantified by a companion volumetric bar-chart chip (V-Chip) for point-of-care analysis. The V-Chip signals of triple-negative breast cancer and its lung metastasis mouse model showed a significant increase compared to healthy mice. Our nanosensor can also noninvasively monitor the course of treatment, which is significant for screening tumor recurrence and individualized evaluation of pharmacological and follow-up efficacy. Importantly, this strategy could be adapted for various diseases to form a common diagnostic platform by changing responsive linkers.

Hypoxia‐Responsive Platinum Supernanoparticles for Urinary Microfluidic Monitoring of Tumors

AbstractCancer has become a leading cause of morbidity and mortality, and there is an increasing need for versatile tools to enable sensitive, simple and early cancer monitoring. Here, we report platinum supernanoparticles as an exogenous nanosensor which can dissociate into ultrasmall platinum nanoclusters (PtNCs) under tumor‐specific hypoxia conditions. The resulting PtNCs can be filtered through the kidney as urinary reporters to be quantified by a companion volumetric bar‐chart chip (V‐Chip) for point‐of‐care analysis. The V‐Chip signals of triple‐negative breast cancer and its lung metastasis mouse model showed a significant increase compared to healthy mice. Our nanosensor can also noninvasively monitor the course of treatment, which is significant for screening tumor recurrence and individualized evaluation of pharmacological and follow‐up efficacy. Importantly, this strategy could be adapted for various diseases to form a common diagnostic platform by changing responsive linkers.

Fluorescence-active and peroxidase-like expanded mesoporous silica-encapsulated ultrasmall Pt nanoclusters: a novel colorimetric/fluorescent dual-mode nanosensor for sensitive detection of mercury in medicinal and edible Pueraria lobata.

Anovel colorimetric/fluorescent dual-mode nanosensor for Hg2+ detection was constructed using expanded mesoporous silica (EMSN)-encapsulated ultrasmall platinum nanoclusters (EMSN@Pt NCs) with improved peroxidase-like and stable fluorescent activities. The sensing technique was based on the mechanism that the peroxidase mimetic activity and fluorescence intensity of EMSN@Pt NCs can be inhibited in the presence of Hg2+. In this sensing platform, a linear range of 5-50 nM with a detection limit of 1.78±0.38 nM and quantification limit of 5.93 nM was obtained via fluorescent analysis. Alinear calibration curve from 0.25 to 200 nM with a detection limit of 8.25±0.51 nM and quantification limit of 27.47 nM was achieved via colorimetric analysis. The proposed dual-mode probe possesses excellent selectivity and reliability for Hg2+ detection, which can function as an efficient nanosensor for the quantitative determination of Hg2+ in Pueraria lobata.

Binary regulation of the tumor microenvironment by a pH-responsive reversible shielding nanoplatform for improved tumor chemo-immunotherapy

The limited infiltration of specific T cells in an immunosuppressive microenvironment is a major challenge for cancer immunotherapy. Reversing tumor microenvironment and inducing an antitumor immune response are crucial for cancer therapy. Here, phenylboronic acid (PBA) derivative-stabilized ultrasmall platinum nanoparticles (PBA-Pt) and dextran-coated BLZ-945 nanoparticles (DNPs) were co-assembled through a pH-responsive borate ester bond to construct a versatile reversible shielding multifunctional nanoplatform (Pt@DNPs) for the first time. Pt@DNPs dissociated into two individual components, namely PBA-Pt and DNPs, in the tumor acid microenvironment. Both in vitro and in vivo studies revealed that Pt@DNPs induced immunogenic cell death (ICD) (through multimechanisms involving PtⅡ release and a multienzyme catalytic process by PBA-Pt) and relieved immunosuppressive microenvironment (depletion of tumor-associated macrophages by BLZ-945), which led to tumor-associated antigen release, maturation of dendritic cells, and infiltration of cytotoxic T cells for efficient antitumor immune response against both primary tumor and pulmonary metastatic tumor nodules. Therefore, Pt@DNPs is a promising option for cancer chemo-immunotherapy. Statement of significanceA versatile reversible shielding multifunctional nanoplatform (Pt@DNPs) was engineered for the first time for combinational cancer chemo-immunotherapy. Multimechanisms involving induction of immunogenic cell death by PBA-Pt and sufficient TAM depletion by DNPs could efficiently relieve tumor immunosuppressive microenvironment and activate the antitumor immune response. The synergistic effect not only increased the infiltration of specific T cells in primary tumor, but it also induced a strong immune response against pulmonary metastatic nodules. Collectively, this nanoplatform may represent a promising strategy for combinational chemo-immunotherapy for cancers.

Seed-Mediated Synthesis and Catalytic ORR Reactivity of Facet-Stable, Monodisperse Platinum Nano-Octahedra

Shape-selective, sub-10 nm-sized metal nanoparticles are of high fundamental and practical interest in catalysis and electrocatalysis, where the surface structure dictates the kinetic properties of the nanomaterials. Unlike their bimetallic analogues, the synthesis of size-controlled, pure Pt octahedral nanocatalysts has remained a formidable chemical challenge. In bimetallic shaped systems, however, the benefit of shape is often convoluted with surface composition in complex ways. In the present work, a seed-templated approach is presented for the preparation of ultrasmall octahedral platinum nanoparticles (Pt NPs), harnessing the effect of monocrystalline anisotropic seeds and strict control of the reduction rate and other physicochemical parameters while avoiding polymers, surfactants, and organic solvents. The procedure yields previously elusive 6.7 nm, strictly single-crystal, Pt NPs with partially truncated octahedral shape and prevalent extended {111} surface facets. Electrochemical measurements using rotating disk electrodes in an acid electrolyte revealed a much higher electrochemical active surface area (ECSA) over the state-of-the-art octahedral Pt NPs, which is ascribed to small-sized, poison-free, and preferentially {111} orientated facets. The dramatic kinetic benefit for the oxygen reduction reaction (ORR) of the octahedral shape over spherical particle shapes of same size is convincingly demonstrated. More important for practical applications is the fact that the intrinsic specific ORR activity is about 2.4-fold higher than commercial optimized spherical Pt NPs deployed in fuel cell cathodes at comparable ORR stability. In doing this analysis, we validate the voltammetric correspondence between Pt single crystals and Pt nanoparticulate materials and highlight the kinetic benefits of limiting the proportion of {100} facets. Prolonged suppression of {100} facet growth in octahedral Pt catalysts is the reason for the unusually high specific activity and fair stability and calls for their integration and testing as cathode catalysts in fuel cell membrane electrode assemblies.

Charge Modified Porous Organic Polymer Stabilized Ultrasmall Platinum Nanoparticles for the Catalytic Dehydrogenative Coupling of Silanes with Alcohols

Charge Modified Porous Organic Polymer Stabilized Ultrasmall Platinum Nanoparticles for the Catalytic Dehydrogenative Coupling of Silanes with Alcohols

Ultra-Small Platinum Nanoparticle-Enabled Catalysis and Corrosion Susceptibility Reverse Tumor Hypoxia for Cancer Chemoimmunotherapy.

A major challenge in the use of chemotherapy and immunotherapy is hypoxia-induced progression of tumor cells. We aim to curb hypoxia using metal-based O2-producing nanomedicine. The key focus is therapeutic targeting of hypoxia-inducible factor 1α (HIF-1α), a major reactive oxygen species (ROS)-activated player that drives hypoxia-dependent tumor progression. Inhibition of tumor growth by blocking both HIF-1α and immune checkpoint molecules via ROS removal is a promising new strategy to avoid ROS-induced hypoxia signaling and boost antitumor immunity. Here, we investigated the synergistic effect of ultra-small platinum nanoparticles (Pt-nano) with dual functions of enzyme-mimicking catalysis and corrosion susceptibility to block hypoxia signaling of tumors. Ultra-small Pt-nano with highly corrosive susceptibility can efficiently catalyze ROS scavenging and promote oxygen accumulation for hypoxia reversal, leading to reduced HIF-1α expression. The unique corrosion susceptibility allows ultra-small Pt-nano to effectively exert platinum cytotoxicity, induce reversal of hypoxia-mediated immune suppression by promoting cytotoxic T-cell infiltration of tumors, and reduce the levels of tumoral immune checkpoint molecules and immunosuppressive cytokines. In combination with immune checkpoint blockade using monoclonal antibodies, nanoparticle-enabled enzyme-mimicking is a promising strategy for the enhancement of chemoimmunotherapeutic efficacy through the reversal of tumor hypoxia.

Magnetic resonance imaging during the templated synthesis of mesoporous TiO2 supporting Pt nanoparticles for MOR

Mesoporous TiO2 was prepared, inside “Taurasi” grape skins. The peel impregnation was followed by magnetic resonance imaging, to monitor the transport process in the natural template and the interaction of the solute with the templating structure.Moreover, the prepared mesoporous structure was used to support ultra-small platinum nanoparticles (USNPs), allowing high dispersion and maximizing active metals utilization. USNPs characterization was performed by means of high-resolution analytical transmission electron microscopy, CO-Diffuse Reflectance Infrared Fourier Transform spectroscopy, and X-ray photoelectron spectroscopy. Low Pt loaded TiO2 was then tested in methanol oxidation reactions, showing an excellent behavior: negligible onset potentials (0.06 V) and very high If/Ib ratio (3.85). The results obtained in this work evidence the outstanding performances of the synthesized nano-electrocatalysts.

Carbon nitride/positive carbon black anchoring PtNPs assembled by γ-rays as ORR catalyst with excellent stability

Electrocatalytic performance of low-cost graphitic carbon nitride (CN) is greatly limited by its limited conductivity and small specific surface area. Herein, a simple and cost-effective idea to produce novel nanocomposite is constructed by the CN and cetyl trimethyl ammonium bromide functionalized carbon black (CB) anchored platinum nanoparticles as highly efficient oxygen reduction catalysts based on gamma irradiation. The assembled carbon nitride/positive carbon black anchoring PtNPs (Pt/CN2-CB+ 1) catalyst exhibits significantly improved specific surface area, high graphitization, and uniformly dispersed ultra-small platinum nanoparticles. For the oxygen reduction reaction (ORR) performance, the catalyst shows more positive onset-potential (0.93 V versus RHE) and larger diffusion limiting current density (5.65 mA cm−2) compared with benchmark Pt/C catalysts in alkaline medium. Moreover, the Pt/CN2-CB+ 1 catalyst exhibits a small Tafel slope (92 mV dec−1). Besides, the catalyst was demonstrated the remarkable methanol tolerance and good long-term stability under working conditions. This work provides a new and effective γ-rays irradiation for synthesizing the carbon nitride catalysts for energy conversion and storage applications.

Ultra-small platinum nanoparticles segregated by nickle sites for efficient ORR and HER processes

In the electrochemical process, Pt nanoparticles (NPs) in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint, ultimately resulting in reduction of the active sites and catalytic efficiency. How to uniformly disperse and firmly fix Pt NPs on carbon matrix with suitable particle size for catalysis is still a big challenge. Herein, to prevent the agglomeration and shedding of Pt NPs, Ni species is introduced and are evenly dispersed in the surface of carbon matrix in the form of Ni-N-C active sites (Ni ZIF-NC). The Ni sites can be used to anchor Pt NPs, and then effectively limit the further growth and agglomeration of Pt NPs during the reaction process. Compared with commercial Pt/C catalyst, Pt@Ni ZIF-NC, with ultralow Pt loading (7 wt%) and ideal particle size (2.3 nm), not only increases the active center, but also promotes the catalysis kinetics, greatly improving the ORR and HER catalytic activity. Under acidic conditions, its half-wave potential (0.902 V) is superior to commercial Pt/C (0.861 V), and the mass activity (0.38 A per mg Pt) at 0.9 V is 4.7 times that of Pt/C (0.08 A per mg Pt). Besides, it also shows outstanding HER performance. At 20 and 30 mV, its mass activity is even 2 and 6 times that of Pt/C, respectively. Whether it is under ORR or HER conditions, it still shows excellent durability. These undoubtedly indicate the realization of dual-functional catalysts with low-Pt and high-efficiency properties.

Ambient-Stable Black Phosphorus-Based 2D/2D S-Scheme Heterojunction for Efficient Photocatalytic CO2 Reduction to Syngas

Black phosphorus (BP), an emerging remarkable photocatalytic semiconductor, is arousing strong interests in this field of solar-driven CO2 reduction, but its stability and activity are still facing huge challenges. Here, an ambient-stable and effective 2D/2D heterostructure of BP/bismuth tungstate (Bi2WO6) with oxygen vacancy is innovatively designed for syngas production via photocatalytic CO2 reduction. This work, not only resolves the stability problem of BP nanosheets by anchoring ultrasmall platinum (Pt) nanoparticles (∼2 nm) but also greatly improves the charge transfer efficiency by constructing S-scheme 2D/2D heterostructure with coupled oxygen defects. As a result, the generation rates of carbon monoxide (CO) and hydrogen (H2) remarkably reach 20.5 and 16.8 μmol g-1 h-1, respectively, which are much higher than that of reported BP-based materials, and the accomplished CO/H2 ratios (1:1-2:1) are exactly the most desirable syngas for industrial applications. Thus, this work constructs an efficient and ambient-stable BP-based photocatalyst for syngas production by CO2 reduction at mild conditions.

Binary Regulation of Tumor Microenvironment by pH-Responsive Reversible Shielding Nanoplatform for Improved Tumor Chemo-Immunotherapy

Limited specific T cells infiltration in immunosuppressive microenvironment is the major challenge for cancer immunotherapy. Reversing tumor microenvironment and inducing antitumor immune response is crucial for successful cancer management. Herein, phenylboronic acid (PBA) derivate stabilized ultrasmall platinum nanoparticle (PBA-Pt) was bound with dextran coated BLZ-945 nanoparticle (DNPs) through pH-responsive borate ester bond to construct a novel reversible shielding multifunctional nanoplatform (Pt@DNPs) for the first time. We demonstrated that Pt@DNPs could separate into two individual parts PBA-Pt and DNPs in acidic microenvironment. Both in vitro and in vivo studies revealed that Pt@DNPs could both induce immunogenic cell death (ICD) effect (through multi-mechanisms PtⅡ release and multi-enzymes catalytic process by PBA-Pt) and immunosuppressive microenvironment relief (tumor associated macrophage depletion by DNPs), which could lead to tumor associated antigen release, dendritic cells maturation and cytotoxic T cells infiltration for efficient antitumor immune response against both primary tumor and pulmonary metastasis tumor nodules. Therefore, Pt@DNPs will be a promising option for breast cancer and metastatic breast cancer chemo-immunotherapy.

One-step Synthesis of Ultrasmall Platinum Nanoparticles Supported on Amino-Functionalized Graphene to Create an Electrochemical Molecularly Imprinted Polymer Sensor for Fluxapyroxad

One-step Synthesis of Ultrasmall Platinum Nanoparticles Supported on Amino-Functionalized Graphene to Create an Electrochemical Molecularly Imprinted Polymer Sensor for Fluxapyroxad

Stretchable Electrode Based on Au@Pt Nanotube Networks for Real-Time Monitoring of ROS Signaling in Endothelial Mechanotransduction.

Vascular endothelial cells (ECs) are natively exposed to dynamic cyclic stretch and respond to it by the production of vasoactive molecules. Among them, reactive oxygen species (ROS) are closely implicated to the endothelial function and vascular homeostasis. However, the dynamic monitoring of ROS release during endothelial mechanotransduction remains a steep challenge. Herein, we developed a stretchable electrochemical sensor by decoration of uniform and ultrasmall platinum nanoparticles (Pt NPs) on gold nanotube (Au NT) networks (denoted as Au@Pt NTs). The orchestrated structure exhibited prominent electrocatalytic property toward the oxidation of hydrogen peroxide (H2O2) (as the most stable ROS) while maintaining excellent mechanical compliance of Au NT networks. Moreover, the favorable biocompatibility of Au NTs and Pt NPs promoted the adhesion and proliferation of ECs cultured thereon. These allowed in situ inducing ECs mechanotransduction and synchronously real-time monitoring of H2O2 release. Further investigation revealed that the production of H2O2 was positively correlated with the applied mechanical strains and could be boosted by other coexisting pathogenic factors. This indicates the great prospect of our proposed sensor in exploring ROS-related signaling for the deep understanding of cell mechanotransduction and vascular disorder.

Ultrasmall platinum nanozymes as broad-spectrum antioxidants for theranostic application in acute kidney injury

Acute kidney injury (AKI) is a common kidney disease with high mortality rate, while surprisingly, the supportive treatment and renal replacement are the only available clinical treatment options to date. The onset of AKI is often triggered by excessive toxic reactive oxygen/nitrogen species (RONS), and hence, the development of antioxidants with high renal accumulation and effective renal clearance is highly demanded to consume RONS in the kidneys. In this study, we developed ultrasmall polyvinylpyrrolidone-coated platinum nanoparticles (Pt NPs-PVP, ~3 nm) as multienzyme mimetics (catalase, peroxidase, and superoxide dismutase). Thanks to their excellent RONS scavenging ability, Pt NPs-PVP effectively reduced the hydrogen peroxide induced cellular damage. Analytical (inductively coupled plasma mass spectrometry) as well as imaging (photoacoustic and computed tomography) techniques revealed the preferential renal uptake and high enrichment of ultrasmall Pt NPs-PVP after intravenous administration, offering remarkable relief of the clinical symptoms of glycerol-induced AKI mice without any apparent systemic toxicity in vivo. Importantly, because of their ultrasmall size, Pt NPs-PVP exhibited rapid excretion from healthy mice, presenting relatively low toxicity and side effects. In conclusion, our work demonstrated ultrasmall Pt nanozyme as a state of the art antioxidant for dual-modal imaging guided treatment of AKI with improved treatment efficacy.

Enhancing the methanol tolerance of ultrasmall platinum nanoparticles and manganese oxide onto carbon for direct methanol fuel cell: The importance of the synthesis procedure

Pt-based cathodes in direct methanol fuel cells are promising materials for a wide range of applications. However, such materials suffer significant performance loss due to severe methanol crossover from anode to cathode, resulting in mixed potentials from methanol oxidation and oxygen reduction reaction. Herein, we proposed some facile synthesis procedures to avoid Pt active sites contamination from methanol. The strategy was to associate controlled ultrasmall Pt nanoparticles (NPs), Vulcan XC-72, and MnOx species prepared from Mn(NO3)2.4H2O. Interestingly, we have observed that depending on the synthetic pathway chosen, the methanol-tolerance ability of the material increased, suggesting different interactions among the components of the catalyst. The results indicated an improved selectivity of the system due to a synergy between Pt and MnOx. The best strategy was the immobilization of ultrasmall Pt NPs (~2 nm) on carbon black, before impregnation and thermal decomposition of MnOx, which almost wholly suppressed the methanol oxidation interference on the system. Also, the optimized cathode presented a comparable performance for ORR to the traditional Pt/C without methanol addition. To further rationalize such findings, physical and electrochemical characterizations were successfully performed, which allowed us to better understand the proposed catalysts and their different methanol-tolerance abilities.