Jinbo Fei

Triggered release of insulin from glucose-sensitive enzyme multilayer shells.

A glucose-sensitive multilayer shell, which was fabricated by the layer-by-layer (LbL) assembly method, can be used as a carrier for the encapsulation and controlled release of insulin. In the present report, glucose oxidase (GOD) and catalase (CAT) were assembled on insulin particles alternately via glutaraldehyde (GA) cross-linking. The resulting core-shell system has been proven to be glucose-sensitive. When the external glucose was introduced, the release ratio of insulin from the protein multilayer can be increased observably. This is likely attributed to the catalysis interaction of CAT/GOD shells to glucose, which leads to the production of H(+) and thus drops the pH of the microenvironment. Under the acidic conditions, on the one hand, a part of C=N bond formed from Schiff base reaction can be broken and thus increasing the permeability of the capsule wall. On the other hand, the solubility of insulin can also be increased. The above factors may be the key control to increase the release of insulin from the multilayer. Therefore, such CAT/GOD multilayer may have a great potential as a glucose-sensitive release carrier for insulin, and may open the way for the further application of LbL capsules in the drug delivery and controlled release, etc.

Self-assembly of peptide-inorganic hybrid spheres for adaptive encapsulation of guests.

Adv. Mater. 2010, 22, 1283–1287 2010 WILEY-VCH Verlag G T IO N Self-assembly, a common process at all scales, is emerging as a powerful, bottom-up approach for the fabrication of novel functional nanoor biomaterials. It is ubiquitous in nature. By learning from nature or imitating the self-assembly process in biological systems, one can delicately design or extract molecular building blocks for the creation of biomimetic or bioinspired nanostructural materials. Many bioactive building blocks for self-assembly are derived with inspiration from a pathogenic process. A known example is that of the diphenylalanine peptide (L-Phe-L-Phe) (FF) which is extracted from Alzheimer’s b-amyloid polypeptide as the core recognitionmotif for molecular self-assembly. Such peptides are a sort of versatile, selfassembling building block in the construction of defined supramolecular structures, owing to their ease of synthesis, facile chemical and biological modification, and biocompatibility. However, improved properties and novel functions for such nanoor biomaterials are needed to arrive at potential applications in nanotechnology. The fabrication of hybrid, supramolecular systems based on the combination of peptide or protein building blocks and inorganic components is an effective strategy to achieve the integration of functions. Herein, polyoxometalates (POMs), a well-known class of anionic oxide nanoclusters of transition metals, are used as possible inorganic components for the fabrication of such hybrid materials, owing to their potential applications in catalysis, electronics, optics, magnetic materials, medicine, and biology. We selected a Keggin-type POM, phosphotungstic acid (PTA) as a polyoxoanion model molecule, and combined it with the cationic dipeptide (CDP), H-Phe-Phe-NH2 HCl, which is derived from the FF peptide to assemble the expected hybrids. Figure 1 shows the suggested process of the formation of such functional hybrid colloidal spheres from the coassembly of PTA and CDP in water. To our knowledge, this is the first time that a stable, spherical structure has been obtained in water, based on the coassembly of a bioactive peptide and a polyoxoanion. The as-prepared colloidal spheres not only display stimuli-responsive properties to pH or temperature, but also lead to a novel function: enabling adaptive encapsulation for a wide variety of guest materials ranging from small molecules to nanoscale materials during self-assembly. The supramolecular assembly in the form of colloidal spheres based on PTA and CDP was initially investigated and prepared by the addition of an aqueous solution of PTA to a 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) solution of CDP (in a 1:5 charge ratio) at room temperature. Such a mixing resulted in an immediate, opalescent, cloudy suspension (Fig. S1a in the Supporting Information), indicating there was some assembly taking place in the system. The precipitates, which were separated from the bulky solution, were imaged using scanning electron microscopy (SEM). An SEM image (Fig. 2a) shows that the assemblies are colloidal spheres with diameters ranging from about 100 to 250 nm. Energy dispersive X-ray (EDX) spectroscopy attached to the SEM (inset in Fig. 2a) indicates that such hybrid colloidal spheres are composed of both PTA and CDP, as evidenced by the presence of tungsten and carbon elements throughout the assemblies. Transmission electron microscopy (TEM) images (Fig. 2b–c) also demonstrate the formation of regular spherical structures with average diameters of 150 nm. The high-resolution TEM (HR-TEM) studies indicate that the hybrid colloidal spheres contain basic structural units consisting of many dark objects approximately 1 nm in size (attributable to single PTA clusters) surrounded by a peptide shell with lower electron contrast (Fig. 2d). The average size of the peptide-encapsulated clusters (PECs) is about 1.4 nm. It is noted that the diameter of each POM molecule with a Keggin structure is around 1 nm. In a dynamic light scattering (DLS) measurement

Controlled Preparation of Porous TiO2–Ag Nanostructures through Supramolecular Assembly for Plasmon‐Enhanced Photocatalysis

By templating Ag(+)-induced supramolecular assembly at different temperatures, porous TiO2-Ag nanotubes and nanospheres are fabricated in a controlled manner due to the effect of Rayleigh instability. Compared with traditional TiO2 nanoparticles, TiO2-Ag nanostructures above show much more extensive visible light absorption and exhibit the noticeably plasmon-enhanced photocatalysis because of the existence of Ag nanoparticles.

Large-scale preparation of 3D self-assembled iron hydroxide and oxide hierarchical nanostructures and their applications for water treatment

Large-scale urchin-like iron hydroxide and oxide nanostructures were self-assembled through a low-temperature hydrothermal process assisted by two-way phase transition under sonication. The as-obtained iron hydroxide and oxide nanomaterials were used as adsorbents in waste-water treatment, and showed very good ability to remove organic pollutants.

Lipid coated mesoporous silica nanoparticles as photosensitive drug carriers

This paper presents a strategy for the biofunctionalization of novel photosensitizer carriers, mesoporous silica nanoparticles (MSNs). After being calcined and absorbed with photosensitizers (hypocrellin B, HB), MSNs can be coated with a lipid layer. Transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) results proved that HB molecules can be loaded into MSN porous and lipid can coated on the surface of the nanoparticles. When co-cultured with cancer cells (MCF-7), MSNs can transport HB molecules into cells and present low cytotoxicity. With the introduction of a lipid layer, the efficiency of MSN uptake by cells can be improved. These intracellular HB-loaded MSN materials also present cytotoxicity to MCF-7 cells after light irradiation which indicates the materials can be used as good photosensitizer carriers in photodynamic therapy.

pH- and redox-responsive polysaccharide-based microcapsules with autofluorescence for biomedical applications.

Autofluorescent microcapsules were assembled by covalent cross-linking of polysaccharide alginate dialdehyde (ADA) derivative and cystamine dihydrochloride (CM) through a layer-by-layer (LBL) technique. The formulated Schiff base and disulfide bonds render capsules with pH- and redox-responsive properties for pinpointed intracellular delivery based on the physiological difference between intracellular and extracellular environments. This simple and versatile method could be extended to other polysaccharide derivatives for the fabrication of autofluorescent nano- and micromaterials with dual stimuli response for biomedical applications.

Controlled Fabrication of Polyaniline Spherical and Cubic Shells with Hierarchical Nanostructures

Polyaniline spherical and cubic shells with hierarchical nanostructures were prepared by using MnO(2) hollow hierarchical nanostructures with different morphologies as reactive templates in a controlled manner. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images reveal that the PANI shells as-prepared are narrowly dispersed and possess uniform morphologies. Fourier transform infrared (FT-IR) and UV-vis spectra of the hollow shells indicate that the PANI exists in the emeraldine form. Cyclic voltammogram shows that the PANI exhibits multiple redox behavior during potentiodynamic cycling in acidic media at potentials. This strategy developed can be extended to synthesize other conducting polymers such as PPY shells with the similar controlled 3D hierarchical nanostructures.

A peony-flower-like hierarchical mesocrystal formed by diphenylalanine

A facile method is reported to manipulate a diphenylalanine peptide into hierarchically ordered structures with interesting peony-like flower morphology in the organic solvent tetrahydrofuran. The flowers formed in THF and showed, by scanning electron microscopy, that they are actually flake-built spherical aggregations, while the aggregations of FF that formed in other chosen organic solvents, such as DMSO and pyridine, show dispersive flakes. The building of the flower-like architectures is correlated to a nonclassical crystallization pathway. The similarity between the as-obtained peptide mesocrystals formed in different solvents has been investigated and discussed. Due to the roughness of the hierarchical peptide assemblies, an antiwetting surface is readily constructed with a low surface free energy fluoroalkylsilane.

Peptide Mesocrystals as Templates to Create an Au Surface with Stronger Surface‐Enhanced Raman Spectroscopic Properties

The design and fabrication of various nanostructures with predefined geometry and composition is a big challenge of nanotechnology. Here we demonstrate an Au nanoflake film replicated from a self-assembled, well-ordered, dipeptide flower-like hierarchical architecture. Such morphology can give rise to useful and remarkable surface-enhanced Raman spectroscopy (SERS) properties. We obtained these nanostructures by using a scaffold of flake-built spherical dipeptide aggregations. Gold nanoparticles were sputtered on the surface of as-assembled dipeptide by an etching system. After removing the dipeptide templates by ethanol, a metal crust was left with a morphology similar to that of the dipeptide hierarchical structure. The different steps within the process were monitored by using electron microscopy, energy-dispersive spectrum (EDS) analysis and atomic force microscopy (AFM). Cyclic voltammetry and Raman spectra were employed to prove the SERS effect of the obtained Au substrates. The enhancement factor is estimated to be about 10(4) for 4-mercaptobenzoic acid (4-MBA) molecules on the Au nanoflake surfaces.

Coassembly of Photosystem II and ATPase as Artificial Chloroplast for Light-Driven ATP Synthesis

Adenosine triphosphate (ATP) is one of the most important energy sources in living cells, which can drive serial key biochemical processes. However, generation of a proton gradient for ATP production in an artificial way poses a great challenge. In nature, photophosphorylation occurring in chloroplasts is an ideal prototype of ATP production. In this paper we imitate the light-to-ATP conversion process occurring in the thylakoid membrane by construction of FoF1-ATPase proteoliposome-coated PSII-based microspheres with well-defined core@shell structures using molecular assembly. Under light illumination, PSII can split water into protons, oxygen, and electrons and can generate a proton gradient for ATPase to produce ATP. Thus, an artificially designed chloroplast for PSII-driven ATP synthesis is realized. This biomimetic system will help to understand the photophosphorylation process and may facilitate the development of ATP-driven devices by remote light control.