Recyclable Colorimetric Detection of Trivalent Cations in Aqueous Media Using Zwitterionic Gold Nanoparticles

This report describes a colorimetric assay for trivalent metal cations (M³⁺) using gold nanoparticles (AuNPs)-modified with oppositely charged thiols that can form intermolecular zwitterionic surfaces. Zwitterionic AuNPs (Zw-AuNPs) are stable in high-salt solutions and well-dispersed in a wide range of pH values. M³⁺ including Fe³⁺, Al³⁺, and Cr³⁺ can effectively trigger the aggregation of Zw-AuNPs by interfering with their surface potential, and aggregated AuNPs can be regenerated and recycled by removing M³⁺. In our approach, the output signal can be observed by the naked eye within a micromolar (μM) concentration range. Uniquely, our assay is capable of discriminating Fe³⁺ from Fe²⁺, which is challenging using traditional approaches. More importantly, Zw-AuNPs can be stored stably at room temperature for a long period (3 months) with constant detection performance. Both the cost-effectiveness and the long shelf life make Zw-AuNPs ideal for detecting M³⁺ in resource-poor and remote areas

Biomimetic Polymersomes as Carriers for Hydrophilic Quantum Dots

For polymersomes to achieve their potential as effective delivery vehicles, they must efficiently encapsulate therapeutic agents into either the aqueous interior or the hydrophobic membrane. In this study, cell membrane-mimetic polymersomes were prepared from amphiphilic poly(d,l-lactide)-<i>b</i>-poly(2-methacryloyloxyethylphosphorylcholine) (PLA-<i>b</i>-PMPC) diblock copolymers and were used as encapsulation devices for water-soluble molecules. Thioalkylated zwitterionic phosphorylcholine protected quantum dots (PC@QDs) were chosen as hydrophilic model substrates and successfully encapsulated into the aqueous polymersome interior, as evidenced by transmission electron microscopy (TEM) and flow cytometry. In addition, we also found a fraction of the PC@QDs were bound to both the external and internal surfaces of the polymersome. This interesting immobilization might be due to the ion-pair interactions between the phosphorylcholine groups on the PC@QDs and polymersomes. The experimental encapsulation results support a mechanism of PLA-<i>b</i>-PMPC polymersome formation in which PLA-<i>b</i>-PMPC copolymer chains first form spherical micelles, then worm-like micelles, and finally disk-like micelles which close up to form polymersomes

Surface and Size Effects on Cell Interaction of Gold Nanoparticles with Both Phagocytic and Nonphagocytic Cells

With the development of nanotechnology and its application in biomedicine, studies on the interaction between nanoparticles and cells have become increasingly important. To understand the surface and size effects on cell interaction of nanoparticles, the cellular uptake behaviors of two series of gold nanoparticles (AuNPs) with both positively and negatively charged surfaces and sizes range from ∼16 to ∼58 nm were investigated in both phagocytic RAW 264.7 and nonphagocytic HepG2 cells. The internalization of AuNPs was quantified by ICP-MS, and the intracellular fate of NPs was evaluated by TEM analysis. The results showed that the AuNPs with positive surface charge have much higher cell internalization ability than those with negative surface charge in nonphagocytic HepG2 cells. However, the uptake extent of negatively charged AuNPs was similar with that of the positively charged AuNPs when in phagocytic RAW 264.7 cells. Among the tested size range, negatively charged AuNPs with a diameter of ∼40 nm had the highest uptake in both cells, while the positively charged AuNPs did not show a certain tendency. Intracellular TEM analysis demonstrated the different fate of AuNPs in different cells, where both the positively and negatively charged AuNPs were mainly trapped in the lysosomes in HepG2 cells, but many of them were localized in phagosomes when in RAW 264.7 cells. Cytotoxicity of these AuNPs was tested by both MTT and LDH assays, which suggested NP’s toxicity is closely related to the tested cell types besides the surface and size of NPs. It demonstrates that cell interaction between nanoparticles and cells is not only affected by surface and size factors but also strongly depends on cell types

Multidentate Polyethylene Glycol Modified Gold Nanorods for in Vivo Near-Infrared Photothermal Cancer Therapy

Gold nanorods (AuNRs), because of their strong absorption of near-infrared (NIR) light, are very suitable for in vivo photothermal therapy of cancer. However, appropriate surface modification must be performed on AuNRs before their in vivo application because of the high toxicity of their original stabilizer cetyltrimethyl­ammonium bromide. Multidentate ligands have attracted a lot of attention for modification of inorganic nanoparticles (NPs) because of their high ligand affinity and multifunctionality, while the therapeutic effect of multidentate ligands modified NPs in vivo remains unexplored. Here, we modified AuNRs with a polythiol PEG-based copolymer. The multidentate PEG coated AuNRs (AuNR-PTPEGm950) showed good stabilities in high saline condition and wide pH range. And they had much stronger resistance to ligand competition of dithiothreitol (DTT) than AuNRs coated by monothiol-anchored PEG. The AuNR-PTPEGm950 had very low cytotoxicity and showed high efficacy for the ablation of cancer cells in vitro. Moreover, the AuNR-PTPEGm950 showed good stability in serum, and they had a long circulation time in blood that led to a high accumulation in tumors after intravenous injection. In vivo photothermal therapy showed that tumors were completely cured without reoccurrence by one-time irradiation of NIR laser after a single injection of these multidentate PEG modified AuNRs

In Situ Production of Ni Catalysts at the Tips of Carbon Nanofibers and Application in Catalytic Ammonia Decomposition

Ni-carbon nanofibers (Ni-CNFs) catalysts were synthesized in situ by the decomposition of carbon-containing gases (i.e., CH₄, CO, and C₂H₄) over Ni/Al₂O₃ catalyst and directly used to catalyze ammonia decomposition. The results showed that Ni nanoparticles were found to locate at the tips of CNFs when using CH₄ and CO as carbon sources, while they located at the roots of CNFs when using C₂H₄ as a carbon source. For ammonia decomposition, Ni catalysts at the tips of CNFs showed higher activity, which could be due to the more accessible surfaces to the reactants. Interestingly, the Ni catalyst at the tips of CNFs with CH₄ as a carbon source exhibited higher activity than that with CO as a carbon source, even though the former catalyst had a larger average particle size. The possible mechanism was given by combining characterization results with our previous simulation results. Finally, when using CH₄ as a carbon source, the effect of the Ni-CNFs catalysts with different growth times on the activity was further studied

Asymmetric Free-Standing Film with Multifunctional Anti-Bacterial and Self-Cleaning Properties

A superhydrophobic/hydrophilic asymmetric free-standing film has been created using layer-by-layer assembly technique. Poly­(ethylene-imine)-Ag⁺ complex (PEI-Ag⁺) at pH 9.0 was assembled with poly­(acrylic acid) (PAA) at pH 3.2 on a Teflon substrate to yield a micronanostructured surface that can be turned to be superhydrophobic after being coated with a low surface energy compound. Silver nanoparticle loaded free-standing film with one surface being superhydrophobic while the other surface is hydrophilic was then obtained after detachment from the substrate. The superhydrophobicity enabled the upper surface with anti-adhesion and self-cleaning properties and the hydrophilic bottom surface can release silver ions as antibiotic agent. The broad-spectrum antimicrobial capability of silver ions released from the bottom surface coupled with superhydrophobic barrier protection of the upper surface may make the free-standing film a new therapy for open wound

Understanding the Oxidative Stability of Antifouling Polymer Brushes

Poly­(oligoethylene glycol methacrylate) (POEGMA) and zwitterionic polymer brushes have been widely used for constructing biocompatible or antifouling surfaces, and their oxidative stability is very important to the practical application. Herein, POEGMA, poly­(sulfobetaine methacrylate) (PSBMA), poly­(2-(methacryloyloxy)­ethyl phosphorylcholine) (PMPC), and poly­(carboxybetaine methacrylate) (PCBMA) were grafted on quartz crystal microbalance (QCM) chips via surface-initiated atom transfer radical polymerization (SI-ATRP). XPS and MS analyses demonstrate that the mass loss of these polymer brushes in oxidative environment is due to the scission of the polymer-anchoring segments. Molecular simulation further illustrates this mass loss mechanism should be always true for those polymer brushes anchored on different substrates. In situ QCM monitoring indicates that, compared with zwitterionic polymethacrylates, POEGMA brushes show the lowest mass loss rate mainly due to their cross-linked structures. This study sheds light on the contradictory reports about the oxidative stability of POEGMA and zwitterionic polymethacrylate brushes up to now, and highlights the important role of the polymer-anchoring segments playing in the oxidative stability of polymer brushes

Hemoglobin as a Smart pH-Sensitive Nanocarrier To Achieve Aggregation Enhanced Tumor Retention

Natural proteins have been greatly explored to address unmet medical needs. However, few work has treated proteins as natural pH-sensitive nanoplatforms that make use of the inherent pH gradient of pathogenic sites. Here, hemoglobin is employed as a smart pH-sensitive nanocarrier for near-infrared dye IR780, which disperses well at normal tissue pH and exhibits aggregation at tumor acidic milieu. The pH-sensitive hemoglobin loaded with IR780 shows higher uptake by cancer cells at tumor acidic pH 6.5 than normal tissue pH 7.4. In vivo and ex vivo studies reveal that the hemoglobin nanocarrier exhibits distinct retention kinetics with remarkably prolonged residence time in tumor. Hemoglobin is then proved to be a potent pH-sensitive nanocarrier for cancer diagnosis and treatment

Infusing Lubricant onto Erasable Microstructured Surfaces toward Guided Sliding of Liquid Droplets

Introducing a lubricant layer onto surfaces has emerged as a novel strategy to address a wide range of interface-related challenges. Recent studies of lubricant-infused surfaces have extended beyond repelling liquids to manipulating the mobility of fluids. In this study, we report a design of slippery surfaces based on infusing lubricant onto a polyelectrolyte multilayer film whose surface microstructures can be erased rapidly under mild condition. Unlike other lubricant-infused surfaces, the liquid movements (e.g., moving resistance and direction) on such surfaces can be manipulated via programming the surface microstructures beforehand. The work reported here offers a versatile design concept of lubricant-infused surfaces and may turn on new applications of this emerging class of bioinspired materials