Yuanyuan Hu

Self-Assembled Peptide Nanofibers Encapsulated with Superfine Silver Nanoparticles via Ag⁺ Coordination.

We demonstrate that a glutanthione-based oligopeptide, Fmoc-GCE, could self-assemble into nanofibers induced by Ag(+) ions in NaOH solution. During the self-assembly process, the superfine silver nanoparticles were in situ produced on the nanofibers. On the basis of a series of characterizations, we proposed the possible mechanism of the self-assembly, for which the coordination interaction between Fmoc-GCE and Ag(+) ions as well as the π-π stacking of fluorenyl groups were the main driving forces of the self-assembled nanofibers. At appropriate compositions, the 3D networks of Fmoc-GCE/NaOH/Ag(+) nanofibers could further form metallogel, which was responsive to pyridine and melamine, which could coordination with Ag(+) ions. Moreover, the nanofibers encapsulated with superfine silver nanoparticles exhibited catalytic ability in degradation of the azo dye and the antibacterial properties to both Gram negative (E. coli) and Gram positive (S. aureus) bacteria.

Hydrogelation and Crystallization of Sodium Deoxycholate Controlled by Organic Acids

The gelation and crystallization behavior of a biological surfactant, sodium deoxycholate (NaDC), mixed with l-taric acid (L-TA) in water is described in detail. With the variation of molar ratio of L-TA to NaDC (r = n(L-TA)/n(NaDC)) and total concentration of the mixtures, the transition from sol to gel was observed. SEM images showed that the density of nanofibers gradually increases over the sol-gel transition. The microstructures of the hydrogels are three-dimensional networks of densely packed nanofibers with lengths extending to several micrometers. One week after preparation, regular crystallized nanospheres formed along the length of the nanofibers, and it was typical among the transparent hydrogels induced by organic acids with pKa1 value <3.4. Small-angle X-ray diffraction demonstrated differences in the molecular packing between transparent and turbid gels, indicating a variable hydrogen bond mode between NaDC molecules.

Tunable assembly and disassembly of responsive supramolecular polymer brushes

We report the synthesis and assembly of light-responsive supramolecular polymer brushes based on the host–guest interaction between β-cyclodextrin (β-CD) on star-like side chains and azobenzene groups on a polymer backbone. The fraction of the hydrophilic–hydrophobic units can be easily controlled via changing the ratio of host and guest molecules. The supramolecular polymer brushes can self-assemble into unimolecular micelles, multi-molecular micelles, and vesicles with tunable sizes from 28 to 300 nm in water, respectively, with the decrease of β-CD side chains. The assemblies of micelles or vesicles can be disassembled by the trigger of UV light irradiation due to the responsive azobenzene groups. In addition, the phase transition temperature of the supramolecular polymer brushes increases with the decrease of the side chains. The micelles or vesicles can further assemble into strawberry superstructures by increasing the temperature. Our work provides a platform for the generation of assemblies across a wide range of scales, from polymer brushes to micelles or vesicles and superstructures.

Ultrafine Au and Ag Nanoparticles Synthesized from Self‐Assembled Peptide Fibers and Their Excellent Catalytic Activity

The self-assembly of an amphiphilic peptide molecule to form nanofibers facilitated by Ag(+) ions was investigated. Ultrafine AgNPs (NPs=nanoparticles) with an average size of 1.67u2005nm were synthesized in situ along the fibers due to the weak reducibility of the -SH group on the peptide molecule. By adding NaBH4 to the peptide solution, ultrafine AgNPs and AuNPs were synthesized with an average size of 1.35 and 1.18u2005nm, respectively. The AuNPs, AgNPs, and AgNPs/nanofibers all exhibited excellent catalytic activity toward the reduction of 4-nitrophenol, with turnover frequency (TOF) values of 720, 188, and 96u2005h(-1) , respectively. Three dyes were selected for catalytic degradation by the prepared nanoparticles and the nanoparticles showed selective catalysis activity toward the different dyes. It was a surprising discovery that the ultrafine AuNPs in this work had an extremely high catalytic activity toward methylene blue, with a reaction rate constant of 0.21u2005s(-1) and a TOF value of 1899u2005h(-1) .

Effect of Cationic Surfactants with Different Counterions on the Growth of Au Nanoclusters

The influence of a series of cationic surfactants composed of cetyltrimethylammonium cations with different counterions (Br-, Cl-, OH-, C7H8O3S-, [CeCl3Br]-, and NO3-) on the aging process of gold nanoclusters (Au NCs) was studied. The finely different points of Au NCs treated by different surfactants were demonstrated by UV-vis and fluorescence spectra, transmission electron microscopy images, etc. Because of the difference of counterions, these surfactants have diverse physicochemical properties in surface activity, specific conductivity, pH, and viscosity, which may account for the difference of Au NCs in the aging process. In addition, the affinity of the counterions in surfactants to the surface of Au has also been demonstrated completely. This affinity may further guide the difference of the synthesized Au nanomaterials.

Chitosan gel incorporated peptide-modified AuNPs for sustained drug delivery with smart pH responsiveness

In this study, gold nanoparticles (AuNPs) were modified with a negatively charged peptide, Fmoc-GCE, for use as nanocarriers of a positively charged anti-tumor drug, doxorubicin hydrochloride (DOX). The Fmoc-GCE-modified AuNPs were further used to load DOX through electrostatic interaction. A temperature-sensitive gel, chitosan (CS) gel, was chosen to act as an appropriate platform to incorporate the modified AuNPs as a drug carrier. The incorporation of AuNPs makes the complex gel exhibit SERS characteristic, showing application prospects for the detection of cancer. More importantly, this drug delivery system with rather good biocompatibility can significantly extend the release time of the incorporated drugs and possesses pH responsiveness, exhibiting the advantages of controlled release and reduced side effects.

Hydrogels Based on Ag+‐Modulated Assembly of 5′‐Adenosine Monophosphate for Enriching Biomolecules

Supramolecular hydrogels obtained by combining 5-adenosine monophosphate (AMP) with Ag+ were fabricated in this work. Their gelation capability was enhanced by increasing the concentration of Ag+ or decreasing the pH. The gels are very sensitive to light, which endows them with potential applications as visible-light photosensitive materials. Coordination between the nucleobase of AMP and Ag+ , as well as π-π stacking of nucleobases, are considered to be the main driving forces for self-assembly. The hydrogels successfully achieved the encapsulation and enrichment of biomolecules. Hydrogen bonding between the amino group of guest molecules and silver nanoparticles along the nanofibers drives the enrichment and is considered to be a crucial interaction.

Surfactant-regulated fabrication of gold nanostars in magnetic core/shell hybrid nanoparticles for controlled release of drug

Core-shell nanostructured materials, which are of great interest for fundamental research and industrial applications, have properties that can be enhanced by combining component superstructures. Here, we report the new construction of magnetic core-shell gold nanostars (AuNSs) for controlled release of drug. The AuNSs were successfully embedded intact between an inner silica layer and outside mesoporous silica layer to create magnetic core/shell hybrid nanoparticles by using a base cationic templating surfactant, cetyltrimethylammonium hydroxide (CTAOH). The core-shell nano-composites containing AuNSs exhibit the characteristics including high magnetization, mesoporous nanostructure, photothermal properties and low in vitro toxicity, showing the potential applications for drug delivery and controlled release.

Self-assembled structural transition in L-Arg/H-AOT mixtures driven by double hydrogen bonding

The aggregation properties of L-arginine (L-Arg) with the acidic form of sodium bis(2-ethyl-1-hexyl)sulfosuccinate, H-AOT, in water, were investigated in detail. Double hydrogen bonding formed between the guanidyl group on the L-Arg molecule and the –SO3H group on the H-AOT molecule. The combination of L-Arg and H-AOT through hydrogen bonding and electrostatic interaction led to the self-assembly of the mixtures. The addition of hydrophobic H-AOT to L-Arg solution modulated the hydrophobicity/hydrophilicity of the L-Arg/H-AOT complexes, resulting in an increase of the packing parameter. Accordingly, a transition of the self-assembled structure from micelles to a closed lamellar bilayer structure (vesicles) and then a bicontinuous bilayer structure (sponge phase) occurred. The microstructural transition was reflected by rheological measurements, for which significant changes in both viscosity and elasticity appeared, and this was further confirmed by Cryo-TEM and FF-TEM observations.

Comparison of therapeutic response to gonadotropin therapy between chinese male adolescents and young adults with hypogonadotropic hypogonadism caused by pituitary stalk interruption.

Hypogonadotropic hypogonadism (HH) is common in pituitary stalk interruption (PSI) patients. However, the optimal timing and effective regimen in the management of the pituitary-gonadal axis deficiency is still controversial. This study involved a retrospective review of 38 male patients with HH resulting from PSI. The HH patients were subdivided according to their ages into 2 experiment groups: Group I (adolescents, 14-18 years old, 25 cases) and Group II (young adults, 18-24 years old, 13 cases). To compare the therapeutic response to exogenous gonadotropin, a control analysis was carried out in the experimental groups with age-matched control groups. Before gonadotropin therapy, no significant increases in gonadal hormones were noted in either of the 2 experimental groups. After treatment with human chorionic gonadotropin (hCG) for less than 6 months, the hormone levels of pituitary-gonadal axis significantly increased in group I than in group II. After adding the human menopause gonadotropin (hMG) for 6 months, the gonadal hormone levels of group II were significantly increased. In addition, the Tanner stage and penis lengths in group I were significantly improved. There was no significant adverse impact on BMI and height velocity (HV) after less than one year therapy. A prolonged hypogonadotropic period without treatment may be responsible for testicular dysfunction in HH males caused by PSI. Early supplementary therapy with hCG and hMG is beneficial for the recovery of gonadal hormone and development of secondary sexual characteristics.