Sandwich-type electrochemical aptasensor for sensitive detection of myoglobin based on Pt@CuCo-oxide nanoparticles as a signal marker

When an acute myocardial infarction (AMI) occurs, myoglobin (Mb) is the biomarker whose concentration firstly increases, and the high sensitive detection of Mb is critical for early diagnosis of AMI. Herein, a sandwich-type electrochemical aptasensor for the sensitive detection of Mb was constructed by using Pt@Cu1.33OCo0.83O as the signal marker. On one hand, nano-flower-like Cu1.33OCo0.83O was synthesized by hydrothermal method and Pt nanoparticles (Pt NPs) were loaded on its surface. Pt@Cu1.33OCo0.83O could immobilize aptamer 2 (Apt2) successfully by the Pt-S bond. And because of the synergistic effect between Pt and bimetallic oxide, Pt@Cu1.33OCo0.83O had an excellent catalytic effect on the signal source of hydrogen peroxide (H2O2) to amplify the current signal, which enhance the sensitivity of the aptasensor. On the other hand, the screen-printed gold electrode (SPGE) was used as the sensing base, which had good conductivity and ensured the immobilization of aptamer 1 (Apt1). The quantitative detection of Mb was achieved by specific recognition between Mb and Apt1, Apt2. As a result, the constructed electrochemical aptasensor had a good linear range (1-1500 ng/mL) with a low detection limit (LOD) of 0.128 ng/mL (S/N = 3), and a high sensitivity of 29.47 μA dec-1. The aptasensor also realized the detection of Mb in human serum samples with good accuracy, and the results were consistent with the hospital's biochemical indicators, which demonstrated the potential application of the prepared sensor in the clinical detection of Mb.

Fabrication and evaluation of antimicrobial cellulose/Arabic gum hydrogels as potential drug delivery vehicle

This article aims to assess the highly potent antimicrobial hydrogels composed of cellulose and Arabic gum containing sulfadiazine drug (sulfadiazine-loaded Cel/AG) as drug-targeting carriers. ATR-IR, SEM/ EDS, XRD, and XPS methods were used to investigate the hydrogel. The highest water absorption % was 489.93 ± 4.5 at pH 7.4. Pseudo-second order and Fickian diffusion govern the swelling behavior. The maximal sulfadiazine loading percent was 82.291 ± 74. The in-vitro drug release exhibited significant responses in physiologically simulated pH values. The maximum cumulative release percent was 66.42 ± 0.6 % at pH 7.4. The drug release is predicted by the first order and Korsmeyer-Peppas models. The first diffusion coefficient was (D_i = 9.207 ± 47 × 10^-3 cm²/h) and the late one was (D_L = 5.64 ± 9.0 × 10^-2 cm²/h) at pH 7.4. That hydrogel is well-thought-out a potential drug delivery vehicle. The thermal stability of the Cel/AG hydrogel drug carrier has been enhanced by the incorporation of sulfadiazine which is evidenced by increasing the total activation approximately two-fold. The total activation energy of Cel/AG and sulfadiazine-loaded Cel/AG hydrogels were -0.07362 and -0.2092 J/mol. The sulfadiazine medication's inhibitory effect was markedly enhanced when it was incorporated into the Cel/AG hydrogel films.

Recent Advances in Bioorthogonal Click Chemistry for Enhanced PET and SPECT Radiochemistry

Due to their high reaction rate and reliable selectivity, bioorthogonal click reactions have been extensively investigated in numerous research fields, such as nanotechnology, drug delivery, molecular imaging, and targeted therapy. Previous reviews on bioorthogonal click chemistry for radiochemistry mainly focus on ¹⁸F-labeling protocols employed to produce radiotracers and radiopharmaceuticals. In fact, besides fluorine-18, other radionuclides such as gallium-68, iodine-125, and technetium-99m are also used in the field of bioorthogonal click chemistry. Herein, to provide a more comprehensive perspective, we provide a summary of recent advances in radiotracers prepared using bioorthogonal click reactions, including small molecules, peptides, proteins, antibodies, and nucleic acids as well as nanoparticles based on these radionuclides. The combination of pretargeting with imaging modalities or nanoparticles, as well as the clinical translations study, are also discussed to illustrate the effects and potential of bioorthogonal click chemistry for radiopharmaceuticals.

A Sandwich Structure of Fulvic Acid and PMIDA-Modified LDHs for the Simultaneous Removal of Cu2+ and Aniline in Multicomponent Solutions

The coexistence of organic and inorganic pollutants in industrial wastewater has emerged as a concerning environmental issue worldwide due to the critical levels of biological toxicity of these pollutants. In this context, the present study proposes a sandwich structure of fulvic acid and PMIDA-modified LDHs (FA/PMIDA-LDHs) for the simultaneous removal of Cu²⁺ and aniline from wastewater. The specific structure was synthesized using a combination of coprecipitation and impregnation methods. Abundant benzene rings and oxygen-containing functional groups greatly increased the number of sites for the adsorption of both Cu²⁺ and aniline. The maximum adsorption capacity of Cu²⁺ and aniline in solution with initial pH 5.0 at 25 °C could reach 221.24 and 132.28 mg/g, respectively. Cu²⁺ could be chelated by the functional groups in the FA/PMIDA-LDHs structure, and a coupled reduction-complexation mechanism was proposed for this process. The uptake of aniline on FA/PMIDA-LDHs was demonstrated to be a result of the combination of coordination forces, hydrophobic effects, π-π interactions, and hydrogen bonds. In a multicomponent solution, FA/PMIDA-LDHs exhibited excellent salt tolerance of up to 1000 mg/L of Na⁺ or Ca²⁺. The effects of Fe³⁺, Ni²⁺, Cl^-, Cr₂O₇^2-, SO₄^2-, and H₂PO₄^- on the uptakes of Cu²⁺ and aniline were also investigated.

An optical aptasensor for real-time quantification of endotoxin: From ensemble to single-molecule resolution

Endotoxin is a deadly pyrogen, rendering it crucial to monitor with high accuracy and efficiency. However, current endotoxin detection relies on multistep processes that are labor-intensive, time-consuming, and unsustainable. Here, we report an aptamer-based biosensor for the real-time optical detection of endotoxin. The endotoxin sensor exploits the distance-dependent scattering of gold nanoparticles (AuNPs) coupled to a gold nanofilm. This is enabled by the conformational changes of an endotoxin-specific aptamer upon target binding. The sensor can be used in an ensemble mode and single-particle mode under dark-field illumination. In the ensemble mode, the sensor is coupled with a microspectrometer and exhibits high specificity, reliability (i.e., linear concentration to signal profile in logarithmic scale), and reusability for repeated endotoxin measurements. Individual endotoxins can be detected by monitoring the color of single AuNPs via a color camera, achieving single-molecule resolution. This platform can potentially advance endotoxin detection to safeguard medical, food, and pharmaceutical products.

Mesoporous Silica-Coated Upconversion Nanoparticles Assisted Photodynamic Therapy Using 5-Aminolevulinic Acid: Mechanistic and In Vivo Studies

Exclusively red-emitting upconversion nanoparticles (UCNPs) with the composition NaErF₄:0.5%Tm as a core and NaYF₄ as a shell were synthesized for performing photodynamic therapy (PDT). A possible mechanism was proposed for core-shell UCNPs formation. For loading a maximum amount of 5-aminolevulinic acid (5-ALA), mesoporous silica coating was performed on UCNPs. Studies under dark conditions confirmed the biocompatibility of 5-ALA-loaded UCNPs formulation (UCNPs-5-ALA) with MCF-7 cells. Meanwhile, studies under light-exposed conditions exhibited effective cytotoxicity against MCF-7 cells. Studies employing D₂O-based cell cultured media and addition of DABCO in cell culture established that the cell death was due to oxidation of cellular components by reactive oxygen species (ROS) triggering the apoptosis. The formation of ROS was confirmed by DCF(H)DA-based ROS analysis via fluorescence microscopy to demonstrate the ROS production, which mediates the programmed cell death. Additionally, we have validated the apoptosis in MCF-7 cells with flow cytometry analyses. This was further confirmed by an electrophoretic mobility shift assay on nuclear extract and measurement of mitochondrial membrane potential. In the case of animal model studies, the formulation UCNPs-5-ALA without irradiation (980 nm) did not possess any in vivo cytotoxicity on tumor-induced SCID mice and there was a minimum migration of UCNPs-5-ALA to the vital organs but maximum retention at the tumor site only. Meanwhile, only the mice treated with UCNPs-5-ALA and irradiated on the tumor region with 980 nm laser (500 mW) for 20 min possessed a tumor with a size reduced to about 75% as compared with the corresponding control groups. To the best of our knowledge, this type of study was conducted for the first time employing exclusively red-emitting phosphors for effective PDT.

Dually Cross-Linked Core-Shell Structure Nanohydrogel with Redox-Responsive Degradability for Intracellular Delivery

A redox-responsive nanocarrier is a promising strategy for the intracellular drug release because it protects the payload, prevents its undesirable leakage during extracellular transport, and favors site-specific drug delivery. In this study, we developed a novel redox responsive core-shell structure nanohydrogel prepared by a water in oil nanoemulsion method using two biocompatible synthetic polymers: vinyl sulfonated poly(N-(2-hydroxypropyl) methacrylamide mono/dilactate)-polyethylene glycol-poly(N-(2-hydroxypropyl) methacrylamide mono/dilactate) triblock copolymer, and thiolated hyaluronic acid. The influence on the nanohydrogel particle size and distribution of formulation parameters was investigated by a three-level full factorial design to optimize the preparation conditions. The surface and core-shell morphology of the nanohydrogel were observed by scanning electron microscope, transmission electron microscopy, and further confirmed by Fourier transform infrared spectroscopy and Raman spectroscopy from the standpoint of chemical composition. The redox-responsive biodegradability of the nanohydrogel in reducing environments was determined using glutathione as reducing agent. A nanohydrogel with particle size around 250 nm and polydispersity index around 0.1 is characterized by a thermosensitive shell which jellifies at body temperature and crosslinks at the interface of a redox-responsive hyaluronic acid core via the Michael addition reaction. The nanohydrogel showed good encapsulation efficiency for model macromolecules of different molecular weight (93% for cytochrome C, 47% for horseradish peroxidase, and 90% for bovine serum albumin), capacity to retain the peroxidase-like enzymatic activity (around 90%) of cytochrome C and horseradish peroxidase, and specific redox-responsive release behavior. Additionally, the nanohydrogel exhibited excellent cytocompatibility and internalization efficiency into macrophages. Therefore, the developed core-shell structure nanohydrogel can be considered a promising tool for the potential intracellular delivery of different pharmaceutical applications, including for cancer therapy.

Studies on the Mechanism of Cu(II) Ion Sorption on Purolite S 940 and Purolite S 950

The aim of the presented research was to investigate the mechanism of sorption of Cu(II) ions on the commercially available Purolite S 940 and Purolite S 950 chelating ion exchangers with the aminophosphonic functional groups. In order to understand better the sorption mechanism, the beads were cut with an ultramicrotome before and after the Cu(II) ion sorption process. The cut beads were examined by scanning electron microscopy (SEM) with an EDX detector. The performed linear profiles of the elemental composition allowed us to examine the depth with which the sorbed metal penetrates into. For further investigations concerning the mechanism of the sorption process, the Fourier transform infrared spectroscopy (FTIR) analysis using the attenuated total reflectance (ATR) technique and the X-ray photoelectron spectroscopy (XPS) methods have been used. The comparison of FTIR and XPS spectra before and after the sorption of Cu(II) ions showed that free electron pairs from nitrogen and oxygen in the aminophosphonic functional groups participate in the process of copper ion sorption. In addition, the microscopic studies suggested that the process of ion exchange between Na(I) ions and sorbed Cu(II) ions takes place on the Purolite S 940 and Purolite S 950. This study concerning the in-depth understanding the of Cu(II) sorption mechanism, using modern analytical tools and research methods could be very useful for its further modifications leading to the improvement of the process efficiency.

Enhancing catalytic potential of gold nanoparticles by linear and cross-linked polyurethane blending

This work describes the synthesis of gold nanoparticles (AuNPs) and their subsequent stabilization using a water-borne polyurethane matrix of micro-particles (Au/PU) by a heating method. Composites were prepared both from linear and cross-linked polyurethane (LPU and CPU). Catalytic activities of synthesized composites exhibiting 226.4 nm size were evaluated for reduction of Congo red dye. More than 90% Congo red degradation was achieved in just 6 minutes with Au/LPU. Under similar conditions, 30% of dye was degraded with Au/CPU composite in 5 minutes. The effects of different variables such as concentration of dye, catalyst dose and concentration of reagents have been optimized. The degradation process followed first order kinetics. The most efficient composite (Au/LPU) was characterized using UV/Vis, FTIR, SEM, XRD and DLS techniques. The excellent catalytic activity can be attributed to the polyurethane matrix making the dye available to catalytic sites (AuNPs).

This work describes the synthesis of gold nanoparticles (AuNPs) and their subsequent stabilization using a water-borne polyurethane matrix of micro-particles (Au/PU).

Minimalization of Metallic Pd Formation in Suzuki Reaction with a Solid-State Organometallic Catalyst

Suzuki reaction usually uses palladium (Pd) complexes to accommodate a wide range of substrates. In pursuing greener synthesis, immobilization of Pd complexes with various support materials has shown promising potential. Although this approach can give stable conversion, initially immobilized Pd ions are largely reduced to Pd⁰ aggregates and turned essentially into supported nanoparticles after use, which departs from its original intention of complex immobilization and thus hampers its activity. Herein, we immobilize noble metal ions into a spherical thiolated organosilica. This new type of catalysts can catalyze Suzuki reaction homogeneously via leaching out Pd ions and shuttling them back after the reaction. The excellent reusability attained can be attributed to minimalization of forming metallic palladium. Thus, the developed catalysts can be viewed as a two-way device to release and to restore metal ions for homogeneous catalysis.

Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy: Disulfide Bridges Linking Gold Nanoclusters

As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5'-bis(mercaptomethyl)-2,2'-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R-S-S-R) between clusters, and X-ray photoelectron spectra support the finding.

Synthesis of polyimide-modified carbon nanotubes as catalyst for organic pollutant degradation via production of singlet oxygen with peroxymonosulfate without light irradiation

Polyimide-modified carbon nanotubes (PI/CNTs) were synthesized via a solvent-free thermal method and used as a metal-free catalyst to activate peroxymonosulfate for organic contaminant degradation without light irradiation. The characterization results suggested that PI was loaded onto the surface of CNTs. The catalytic ability of the PI/CNTs was strongly correlated with the content of PI in the catalysts. The PI/CNTs (22% of PI) showed the highest catalytic efficiency for organic pollutant degradation at room temperature. The degradation efficiency of acid orange 7 (AO7) dye was significantly enhanced to 98.9% within 15 min, compared to the efficiency of 2.2% exhibited by pure PI. The radical quenching tests and electron paramagnetic resonance spectrometry proved that singlet oxygen, instead of hydroxyl radicals or sulfate radicals, played a dominant role during the catalytic oxidation of AO7. The influences of operation parameters including temperature and catalyst amount were investigated. The PI/CNTs metal-free catalyst exhibited high catalytic activity under a broad range of pH values. The recycling study of four repeated reactions demonstrated good stability of the PI/CNTs. This work provided a promising metal-free catalyst for degradation of organic pollutants in aqueous solutions, contributing to the development of green materials for sustainable remediation.

Nitrone-Modified Gold Nanoparticles: Synthesis, Characterization, and Their Potential as 18F-Labeled Positron Emission Tomography Probes via I-SPANC

A novel bioorthogonal gold nanoparticle (AuNP) template displaying interfacial nitrone functional groups for bioorthogonal interfacial strain-promoted alkyne-nitrone cycloaddition reactions has been synthesized. These nitrone-AuNPs were characterized in detail using 1H nuclear magnetic resonance spectroscopy, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy, and a nanoparticle raw formula was calculated. The ability to control the conjugation of molecules of interest at the molecular level onto the nitrone-AuNP template allowed us to create a novel methodology for the synthesis of AuNP-based radiolabeled probes.

Peptide Cross-Linked Poly(2-oxazoline) as a Sensor Material for the Detection of Proteases with a Quartz Crystal Microbalance

Inflammatory conditions are frequently accompanied by increased levels of active proteases, and there is rising interest in methods for their detection to monitor inflammation in a point of care setting. In this work, new sensor materials for disposable single-step protease biosensors based on poly(2-oxazoline) hydrogels cross-linked with a protease-specific cleavable peptide are described. The performance of the sensor material was assessed targeting the detection of matrix metalloproteinase-9 (MMP-9), a protease that has been shown to be an indicator of inflammation in multiple sclerosis and other inflammatory conditions. Films of the hydrogel were formed on gold-coated quartz crystals using thiol-ene click chemistry, and the cross-link density was optimized. The degradation rate of the hydrogel was monitored using a quartz crystal microbalance (QCM) and showed a strong dependence on the MMP-9 concentration. A concentration range of 0-160 nM of MMP-9 was investigated, and a lower limit of detection of 10 nM MMP-9 was determined.

A novel ultrasensitive surface plasmon resonance-based nanosensor for nitrite detection

Nitrite is a common food additive, however, its reduction product, nitrosamine, is a strong carcinogen, and hence the ultra-sensitive detection of nitrite is an effective means to prevent related cancers. In this study, different sized gold nanoparticles (AuNPs) were modified with P-aminothiophenol (ATP) and naphthylethylenediamine (NED). In the presence of nitrite, satellite-like AuNPs aggregates formed via the diazotization coupling reaction and the color of the system was changed by the functionalized AuNPs aggregates. The carcinogenic nitrite content could be detected by colorimetry according to the change in the system color. The linear concentration range of sodium nitrite was 0-1.0 μg mL^-1 and the detection limit was determined to be 3.0 ng mL^-1. Compared with the traditional method, this method has the advantages of high sensitivity, low detection limit, good selectivity and can significantly lower the naked-eye detection limit to 3.0 ng mL^-1. In addition, this method is suitable for the determination of nitrite in various foods. We think this novel designed highly sensitive nitrate nanosensor holds great market potential.

Characterization, evaluation, and mechanistic insights on the adsorption of antimonite using functionalized carbon nanotubes

Floating catalytic chemical vapor deposition technique was used for synthesizing carbon nanotubes (CNTs) using ferrocene in benzene as the hydrocarbon source. The functionalization of CNTs was carried out by oxidation followed by grafting of potassium iodide (KI) and mercaptoethanol (HS(CH₂)₂OH) ligands to produce iodide-grafted CNTs (CNT-I) and thiol-functionalized CNTs (CNT-SH), respectively. The resulting adsorbents have been thoroughly characterized by various techniques. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) studies revealed the efficient grafting of the ligands. Further, their adsorption capacities towards antimonite have been assessed. The adsorption kinetics fitted the pseudo-second-order model for both the adsorbents. Moreover, the adsorption of Sb(III) followed Langmuir and Freundlich's model. The maximum adsorption capacity of CNT-I and CNT-SH for Sb(III) at pH 7 was found to be 200 and 140.85 mg/g, respectively. The interference effect of various ions on the adsorption of antimonite was studied. A suitable mechanism for Sb(III) adsorption has been postulated using TEM, XRD, XPS, and FTIR. The adaptability of the adsorbents was demonstrated by the removal capacity of Sb(III) at parts per billion levels from nuclear decontamination formulation (NAC) and tap water matrix as well.

Detection of Sulfide Using Mercapto Tetrazine-Protected Fluorescent Gold Nanodots: Preparation of Paper-Based Testing Kit for On-Site Monitoring

This work demonstrates the development of a highly sensitive method to detect and quantify sulfide ions (S^2-) in water samples. First, we synthesized 6-mercapto-s-triazolo(4,3-b)-s-tetrazine (MTT) by the reaction between formaldehyde and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole at room temperature. The synthetic MTT was used as a capping ligand for the synthesis of gold nanodots (AuNDs) via a one-pot green method at room temperature with only a 10 min reaction time. Transmission electron microscopy images exhibited that the MTT-AuNDs have an average particle size of 1.9 nm and an emission maximum at 672 nm upon excitation at 360 nm. The synthesized highly red emissive MTT-AuNDs are used as specific fluorescent probes for the detection of S^2-. The fluorescence of MTT-AuNDs was significantly and dose-dependently quenched by the addition of S^2-. The observed fluorescence quenching was ascribed to the formation of an Au₂S complex, which was determined by Raman and mass spectroscopy. A good linearity was achieved for the increasing concentration of S^2- from 870 nM to 16 μM, and the detection limit was found to be 2 nM (S/N = 3). The S^2- detection system that is described in this study was validated and agreed well with the standard methylene blue method. Furthermore, the present sensor was examined for its use in quantifying S^2- in real water samples obtained from lakes and rivers. In addition, the specificity was checked against the most likely ion interferences in real water. Moreover, a cost-effective and viable paper-based S^2- sensor was fabricated for environmental monitoring based on the use of MTT-AuNDs. The developed system would be an environmentally friendly and easy-to-use detection device for S^2- in water.

Carbon nanotube anions for the preparation of gold nanoparticle–nanocarbon hybrids

This methodology highlights the unusual chemistry of negatively charged carbon nanotubes and provides a blueprint for the generation of hybrid nanomaterials.

Thiol–maleimide “click” chemistry: evaluating the influence of solvent, initiator, and thiol on the reaction mechanism, kinetics, and selectivity

The mechanism and kinetics of thiol–maleimide “click” reactions have been modeled computationally under a variety of conditions and further investigated using experimental competition reactions.

A plasmon-assisted fluoro-immunoassay using gold nanoparticle-decorated carbon nanotubes for monitoring the influenza virus

A plasmon-assisted fluoro-immunoassay (PAFI) was developed for the detection of the influenza virus by using Au nanoparticle (Au NP)-decorated carbon nanotubes (AuCNTs) that were synthesized using phytochemical composites at room temperature in deionized water. Specific antibodies (Abs) against the influenza virus were conjugated onto the surface of AuCNTs and cadmium telluride quantum dots (QDs), which had a photoluminescence intensity that varied as a function of virus concentration and a detection limit of 0.1 pg/mL for all three types of influenza viruses examined. The clinically isolated influenza viruses (A/Yokohama/110/2009 (H3N2)) were detected in the range of 50-10,000 PFU/mL, with a detection limit of 50 PFU/mL. From a series of proof-of-concept and clinical experiments, the developed PAFI biosensing system provided robust signal production and enhancement, as well as an excellent selectivity and sensitivity for influenza viruses. This nanoparticle-based technique could be potentially developed as an efficient detection platform for the influenza virus.

High-density assembly of chemiluminescence functionalized gold nanodots on multiwalled carbon nanotubes and their application as biosensing platforms

A one-step strategy was developed for high-density assembly of N-(aminobutyl)-N-(ethylisoluminol) (ABEI) functionalized gold nanodots onto the sidewalls of chitosan-grafted multiwalled carbon nanotubes (cs-MWCNTs) via the reduction of HAuCl4 with ABEI in the presence of cs-MWCNTs, resulting in novel hybrid nanomaterials with excellent chemiluminescence and electrochemiluminescence properties.