Showing papers by "Bing Xu published in 2010"

Aromatic−Aromatic Interactions Induce the Self-Assembly of Pentapeptidic Derivatives in Water To Form Nanofibers and Supramolecular Hydrogels

Abstract: In this paper we report the conjugation of an aromatic moiety (pyrene (P), fluorene (F), or naphthalene (N)) to pentapeptides GAGAS (1), GVPVP (2), VPGVG (3), VTEEI (4), VYGGG (5), and YGFGG (6) to...

Small peptide nanofibers as the matrices of molecular hydrogels for mimicking enzymes and enhancing the activity of enzymes

Abstract: Enzymes, together with the process of self-assembly, constitute necessary components of the foundation of life on the nanometre scale. The exceedingly high efficiency and selectivity exhibited by enzymes for catalyzing biotransformations naturally lead to the exploration of enzyme mimics and the applications of enzymes in industrial biotransformations. While the mimicking of enzymes aims to preserve the essence of enzymes in a simpler system than proteins, industrial biotransformations demand high activity and stability of enzymes. Recent research suggests that small peptide-based nanofibers in the form of molecular hydrogels can provide a general platform to achieve both important goals. This tutorial review will introduce the recent progress of these research activities on small peptide-based nanomaterials for catalysis and hopes to provide a starting point for further explorations that ultimately may lead to practical applications of enzymes and enzyme mimics for addressing important societal problems in energy, environment, and health.

Molecular nanofibers of olsalazine form supramolecular hydrogels for reductive release of an anti-inflammatory agent.

Abstract: Conjugation of tripeptide derivatives with olsalazine, a clinically used anti-inflammatory prodrug, yields small molecules that self-assemble in water to form supramolecular hydrogels that undergo a gel-to-sol phase transition upon reduction, resulting in the controlled release of 5-aminosalicylic acid as the anti-inflammatory agent. This methodology will ultimately lead to new biomaterials for site-specific drug delivery.

Enzyme-instructed self-assembly of peptide derivatives to form nanofibers and hydrogels

Abstract: The review describes the use of enzyme catalysis and self-assembly, two essential and ubiquitous processes in biology, to create molecular nanofibers of peptide derivatives at the supramolecular level as potential nanomedicines and biomaterials In particular, we discuss the use of enzymes to instruct the self-assembly of small peptide derivatives for hydrogelation, which takes place in vitro or in vivo, extra- or intracellularly, as a new strategy to detect the activity of enzymes, screen enzyme inhibitors, type bacteria, develop drug delivery systems, enhance the activity and stability of enzymes, and control the fate of cells

Multifunctional Magnetic Nanoparticles: Design, Synthesis, and Biomedical Applications

Abstract: The combination of nanotechnology and molecular biology has developed into an emerging research area: nanobiotechnology. Magnetic nanoparticles are well-established nanomaterials that offer controlled size, ability to be manipulated externally, and enhancement of contrast in magnetic resonance imaging (MRI). As a result, these nanoparticles could have many applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Because of the potential benefits of multimodal functionality in biomedical applications, researchers would like to design and fabricate multifunctional magnetic nanoparticles. Currently, there are two strategies to fabricate magnetic nanoparticle-based multifunctional nanostructures. The first, molecular functionalization, involves attaching antibodies, proteins, and dyes to the magnetic nanoparticles. The other method integrates the magnetic nanoparticles with other functional nanocomponents, such as quantum dots (QDs) or metallic nanoparticles. Because they can exhibit several features synergistically and deliver more than one function simultaneously, such multifunctional magnetic nanoparticles could have unique advantages in biomedical applications. In this Account, we review examples of the design and biomedical application of multifunctional magnetic nanoparticles. After their conjugation with proper ligands, antibodies, or proteins, the biofunctional magnetic nanoparticles exhibit highly selective binding. These results indicate that such nanoparticles could be applied to biological medical problems such as protein purification, bacterial detection, and toxin decorporation. The hybrid nanostructures, which combine magnetic nanoparticles with other nanocomponents, exhibit paramagnetism alongside features such as fluorescence or enhanced optical contrast. Such structures could provide a platform for enhanced medical imaging and controlled drug delivery. We expect that the combination of unique structural characteristics and integrated functions of multicomponent magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nanomedicine.

Silver Surface Iodination for Enhancing the Conductivity of Conductive Composites

Abstract: The electrical conductivity of a silver microflake-filled conductive composites is dramatically improved after a filler surface treatment. By a simple iodine solution treatment, nonstoichiometric silver/silver iodide nanoislands form on the silver filler surface. Evidence of the decrease of surface silver oxide species is provided by TOF-SIMS and the redox property of the nanoclusters is studied using cyclic voltammetry and TOF-SIMS depth profile analyses. The redox property of the nanoclusters on silver flakes helps enhance the electrical conductivity of the conductive composites. The electrical resistivity of the improved conductive composites is measured by four-point probe method; the reliability of the printed thin film resistors is evaluated by both the 85 °C/85% relative humidity moisture exposure and the −40 ∼ 125 °C thermal cycling exposure. The conductive composite printed radio frequency identification (RFID) antennas with 27.5 wt% of the modified silver flake content show comparable performance in the RFID tag read range versus copper foil antennas, and better than those commercial conductive adhesives that require much higher silver content (i.e., 80 wt%). This work suggests that a surface chemistry method can significantly reduce the percolation threshold of the loading level of the silver flakes and improve the electrical conductivity of an important printed electronic passive component.

Colloidosome-based Synthesis of a Multifunctional Nanostructure of Silver and Hollow Iron Oxide Nanoparticles

Abstract: Nanoparticles that self-assemble on a liquid-liquid interface serve as the building block for making heterodimeric nanostructures. Specifically, hollow iron oxide nanoparticles within hexane form colloidosomes in the aqueous solution of silver nitrate, and iron oxide exposed to the aqueous phase catalyzes the reduction of silver ions to afford a heterodimer of silver and hollow iron oxide nanoparticles. Transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectrometry, X-ray diffraction, UV-vis spectroscopy, and SQUID were used to characterize the heterodimers. Interestingly, the formation of silver nanoparticles helps the removal of spinglass layer on the hollow iron oxide nanoparticles. This work demonstrates a powerful yet convenient strategy for producing sophisticated, multifunctional nanostructures.

Phenyl groups in supramolecular nanofibers confer hydrogels with high elasticity and rapid recovery

Abstract: In this study, we report multi-component supramolecular hydrogels that exhibit exceptional high storage moduli and a rapid recovery of their original mechanical strength after removing external forces. The formation of such kind of supramolecular hydrogels is simple and versatile, and the components can be easily synthesized or commercially available in large quantities. The supramolecular hydrogels have been characterized by SEM and fluorescence spectrometry and the results obtained by both techniques correlate well with their mechanical properties. They have potential to be developed into useful materials that require high mechanical stiffness and possess rapid recovery properties, such as the injectable immobilization matrix for cells culture, drug release, enzyme encapsulation, etc.

Implementing self-assembly nanometer-sized structures within metal—polymer interface

Abstract: An adhesion bond between a metallic surface layer and a second surface is formed by treating the layers with a material comprising sulphur-containing molecules. The sulphur-containing molecules are applied as a surface treatment of the surfaces, so that the sulphur-containing molecules act as a coupling agent to bond chemically to both substrates form nanometer-sized structures on the surfaces. The nanometer-sized structures are incorporated into a self-assembly interlayer in between the surfaces, with the interlayer forming a bond to both surfaces.

Antineoplastic Hydrogels, and Enzyme-Instructed Preparations Thereof

Abstract: Disclosed is a general methodology to create nano fibers of therapeutic molecules that have a dual role, as both the delivery vehicle and the drug itself. It is shown that with proper molecular design, the integration of enzymatic reaction and self-assembly provides a powerful method to create molecular hydrogels of clinically-used therapeutics without compromising their bioactivities. In addition, the results disclosed herein demonstrate enzyme-instructed self-assembly as a facile strategy for generating the supramolecular hydrogels of molecules that inherently have poor solubility in water. For example, by covalently connecting paclitaxel with a motif that is prone to self-assemble, a hydrogel of paclitaxel can be formed without compromising the activity of the paclitaxel.

Biocompatible reactions: internal construction.

Abstract: Among the wide variety of synthetic processes that chemists have developed, only a few can be carried out under physiological conditions. A condensation reaction that is controlled by the constituents of cells has led to the formation of nanostructures within living cells.

Low-temperature dynamics of magnetic nanoshells

Abstract: Well and poorly crystallized iron oxide nanoshells (or hollow nanoparticles) were successfully fabricated using the Kirkendall effect in an oxygen and in an air environment using Fe nanoparticles. The low-field, zero-field–cooling (ZFC) and field-cooling (FC), measurements on these two samples indicated that the inter-particle interactions between the well-crystallized nanoshells were much stronger than those in the poorly crystallized nanoshell assembly. However, the memory experiments showed that there was no spin-glass phase in the well-crystallized nanoshell assembly, whereas the signature of the spin-glass phase (or the memory effect) was evident in the poorly crystallized nanoshell assembly. This result suggests that the origin of the spin-glass characteristic observed in the poorly crystallized nanoshells is the existence of the spin-glass phase within those particular nanoshells.