Younian Liu

Fabrication of Biopolymeric Complex Coacervation Core Micelles for Efficient Tea Polyphenol Delivery via a Green Process

Nanoencapsulation is a promising method to improve the bioavailability of tea polyphenol (TPP). In this work, we adopted a green process to develop a new kind of complex coacervation core micelles (C3Ms) based on biopolymers for efficient tea polyphenol delivery. First, gelatin-dextran conjugate was synthesized using Maillard reaction. Then the C3Ms were produced by mixing gelatin-dextran conjugate with TPP. Variable factors on the self-assembly of the C3Ms were investigated. Under optimal conditions, the obtained C3Ms are of nanosize (average 86 nm in diameter) with narrow distribution. The formation of the C3Ms is attributed to hydrophobic interaction and hydrogen bonding instead of electrostatic interaction. Transmission electron microscope (TEM) and scanning electron microscope (SEM) results showed that C3Ms have a spherical shape with core-shell structure. ζ-Potential measurement suggested that the core is composed of gelatin with TPP, whereas the shell is composed of dextran segments. The encapsulation efficiency of the C3Ms is pH-independent, but the loading capacity is controllable and as high as 360 wt % (weight/weight of protein). In addition, the C3Ms show sustained release of TPP in vitro. MTT assay revealed that the C3Ms have comparable or even stronger cytotoxicity against MCF-7 cells than free TPP.

Binding of α-Synuclein with Fe(III) and with Fe(II) and Biological Implications of the Resultant Complexes

Parkinsons disease (PD) is hallmarked by the abnormal intracellular inclusions (Lewy bodies or LBs) in dopaminergic cells. Amyloidogenic protein alpha-synuclein (alpha-syn) and iron (including both Fe(III) and Fe(II)) are both found to be present in LBs. The interaction between iron and alpha-syn might have important biological relevance to PD etiology. Previously, a moderate binding affinity between alpha-syn and Fe(II) (5.8x10(3)M(-1)) has been measured, but studies on the binding between alpha-syn and Fe(III) have not been reported. In this work, electrospray mass spectrometry (ES-MS), cyclic voltammetry (CV), and fluorescence spectroscopy were used to study the binding between alpha-syn and Fe(II) and the redox property of the resultant alpha-syn-Fe(II) complex. The complex is of a 1:1 stoichiometry and can be readily oxidized electrochemically and chemically (by O(2)) to the putative alpha-syn-Fe(III) complex, with H(2)O(2) as a co-product. The reduction potential was estimated to be 0.025V vs. Ag/AgCl, which represents a shift by -0.550V vs. the standard reduction potential of the free Fe(III)/Fe(II) couple. Such a shift allows a binding constant between alpha-syn and Fe(III), 1.2x10(13)M(-1), to be deduced. Despite the relatively high binding affinity, alpha-syn-Fe(III) generated from the oxidation of alpha-syn-Fe(II) still dissociates due to the stronger tendency of Fe(III) to hydrolyze to Fe(OH)(3) and/or ferrihydrite gel. The roles of alpha-syn and its interaction with Fe(III) and/or Fe(II) are discussed in the context of oxidative stress, metal-catalyzed alpha-syn aggregation, and iron transfer processes.

Additive-free solvothermal synthesis of hierarchical flower-like LiFePO4/C mesocrystal and its electrochemical performance

Three dimensional hierarchical flower-like lithium iron phosphate (LiFePO4) mesocrystals were successfully synthesized via a solvothermal approach with the utilization of a mixture of water/ethylene glycol/dimethylacetamide (H2O/EG/DMAC) as co-solvent. No other surfactant or template agent was used and beautiful micro-sized LiFePO4 mesoporous structures with a special rose-like morphology were obtained. The hierarchical LiFePO4 mesocrystals were assembled by well crystallized nano-sized LiFePO4 thin plates with a thickness around 100 nm. The characteristics and electrochemical dynamics as well as performance of the obtained hierarchical flower-like LiFePO4 mesocrystals were carefully investigated. The flower-like hierarchical LiFePO4 mesocrystals showed a high initial lithium intercalation capability of 147 mA h g−1 at a current density of 17 mA g−1 (0.1 C), which should be attributed to the high specific surface area resulting from the mesoporous superstructure and well crystallized LiFePO4 nano-plate composition units. Polyvinylpyrrolidone (PVP) was introduced during the solvothermal synthesis as an in situ carbon coating source. The obtained flower-like C-coated LiFePO4 mesocrystals exhibited even better initial lithium intercalation capability of 161 mA h g−1 at 0.1 C and showed improved lithium storage performance at high rates as well as good cyclic stability.

Bimetallic AgM (M = Pt, Pd, Au) nanostructures: synthesis and applications for surface-enhanced Raman scattering

Bimetallic nanoparticles exhibit unique optical and catalytic properties that are dependent on their composition, morphology and structure. In this work, a facile and effective approach, based on a galvanic replacement reaction and co-reduction method was developed to prepare bimetallic AgM (M = Pt, Pd, Au) nanoparticles with hollow or porous structures. The molar composition of Ag and the structure of AgM nanoparticles could be simply modulated by controlling the reaction time. The hollow or porous structure and bimetallic nature of the nanoparticles were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), and UV-vis spectroscopy. The morphology and phase of the bimetallic AgM nanoparticles were discussed as a function of reaction time. Due to the unusual structures, the bimetallic AgM nanoparticles exhibited interesting optical properties. Surface-enhanced Raman scattering (SERS) measurement showed that the SERS activity of the bimetallic AgM nanoparticles was dependent not only on the composition of the particles, but also on the structures (e.g., hollow or porous). The results indicate that as-synthesized bimetallic AgM nanoparticles are good candidates for SERS spectroscopy.

High colour purity single-phased full colour emitting white LED phosphor Sr2V2O7: Eu3+

Single-phased white-light-emitting phosphor Sr2V2O7 : Eu3+ was successfully synthesized by the solid-state method. The result of x-ray diffraction analysis indicated that the obtained phosphor has the same crystal structure as that of Sr2V2O7. The synthesized Sr2V2O7 : Eu3+ was combined with near-UV light (365 nm) chips and then assembled into ligtht-emitting diodes (LED) devices, which generated white light with colour coordinates of (0.324, 0.317). The white light was generated from yellow–green and red emissions, which should be attributed to the host Sr2V2O7 and dopant Eu ions, respectively. The effects of the concentration of Eu ions and charge compensation on the emission intensity were carefully investigated. The results show that the energy migrates from the host to the dopant and also that Li2CO3 should be the best charge compensator for this single-phased phosphor. In addition, the colour rendering index and luminescence efficiency of the fabricated LED devices with Sr1.90V2O7 : 0.10Eu3+ phosphor were 91 and 32 lm W−1, respectively, suggesting that Sr1.90V2O7 : 0.10Eu3+ phosphor is a potential candidate for the phosphor-converted white-light-emitting diodes with near-UV chips.

Polar modified post-cross-linked resin and its adsorption toward salicylic acid from aqueous solution: Equilibrium, kinetics and breakthrough studies.

A novel polar modified post-cross-linked resin PDMPA was synthesized, characterized and evaluated for adsorption of salicylic acid from aqueous solution. PDMPA was prepared by a suspension polymerization of methyl acrylate (MA) and divinylbenzene (DVB), a Friedel-Crafts reaction and an amination reaction. After characterization of the chemical and pore structure of PDMPA, the adsorption behaviors of salicylic acid on PDMPA were determined in comparison with the precursor resins. The equilibrium adsorption capacity of salicylic acid on PDMPA was much larger than the precursor resins and the equilibrium data were correlated by both of the Langmuir and Freundlich models. The pseudo-second-order rate equation fitted the kinetic data better than the pseudo-first-order rate equation, and the micropore diffusion model could characterize the kinetic data very well. The dynamic experimental results showed that the breakthrough point and saturated point of salicylic acid on PDMPA were 40.3 and 92.4BV (1BV=10mL) at a feed concentration of 995.8mg/L and a flow rate of 1.4mL/min, and the resin column could be regenerated by 16.0BV of a mixture desorption solvent containing 0.01mol/L of NaOH (w/v) and 50% of ethanol (v/v).

Syntheses and in vitro antitumor activities of ferrocene-conjugated Arg-Gly-Asp peptides

Ferrocene (Fc) and its conjugates have attracted considerable attention in recent years due to their unique electrochemical behavior and significant biological activities such as antitumor, antimalarial, and antifungal. Arg-Gly-Asp (RGD)-containing peptides, because of their selective binding to integrins which are highly expressed in tumor-induced angiogenesis, play a key role in cancer targeted therapy. In this study, Fc-RGD and Fc-Am-RGD (Fc: ferrocenoyl; Am: 6-aminohexanoic acid) conjugates were synthesized, and the antitumor activities in vitro were investigated. The cell uptake of the conjugates by B16 murine melanoma cells was measured using HPLC-electrochemical method. The antitumor activities of the conjugates were also evaluated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and flow cytometric measurements. The experimental results revealed that Fc-RGD and Fc-Am-RGD exhibit more effective antitumor activities than their parent compounds RGD and Fc-COOH. Moreover, it is found that Fc-Am-RGD yields the lowest IC(50) values of 5.2 ± 1.4 μM toward B16 cells. The HPLC-electrochemical studies confirmed that the insertion of flexible alkyl spacer Am between Fc and RGD significantly increases the cell uptake toward B16 cells and consequently improves the antitumor activity. Our results suggest that Fc-RGD and Fc-Am-RGD conjugates are potential candidates for cancer treatment.

Conversion of Natively Unstructured α-Synuclein to Its α-Helical Conformation Significantly Attenuates Production of Reactive Oxygen Species

The intracellular α-synuclein (α-syn) protein, whose conformational change and aggregation have been closely linked to the pathology of Parkingsons disease (PD), is highly populated at the presynaptic termini and remains there in the α-helical conformation. In this study, circular dichroism confirmed that natively unstructured α-syn in aqueous solution was transformed to its α-helical conformation upon addition of trifluoroethanol (TFE). Electrochemical and UV-visible spectroscopic experiments reveal that both Cu (I) and Cu (II) are stabilized, with the former being stabilized by about two orders of magnitude. Compared to unstructured α-syn (Binolfi et al., J. Am. Chem. Soc. 133 (2011) 194-196), α-helical α-syn stabilizes Cu (I) by more than three orders of magnitude. Through the measurements of H(2)O(2) and hydroxyl radicals (OH) in solutions containing different forms of Cu (II) (free and complexed by unstructured or α-helical α-syn), we demonstrate that the significantly enhanced Cu (I) binding affinity helps inhibit the production of highly toxic reactive oxygen species, especially the hydroxyl radicals. Our study provides strong evidence that, as a possible means to prevent neuronal cell damage, conversion of the natively unstructured α-syn to its α-helical conformation in vivo could significantly attenuate the copper-modulated ROS production.

Synthesis, characterization and adsorption properties of an amide-modified hyper-cross-linked resin

Friedel–Crafts reaction, amination reaction and acetylation reaction were performed with chloromethylated polystyrene (CMPS), and amide-modified hyper-cross-linked resin, HCP-EDA-AA, was prepared. The prepared HCP-EDA-AA owned predominant nanopores and medium polarity, making it possess superior adsorption performance to salicylic acid as compared with the raw material CMPS and the intermediate products, hyper-cross-linked polymer (HCP) and the ethylenediamine-modified hyper-cross-linked resin (HCP-EDA). The Langmuir model characterized the equilibrium data better than the Freundlich model. At a feed concentration of 800.5 mg L−1 and a flow rate of 67 mL h−1, the dynamic capacity of salicylic acid on HCP-EDA-AA was 267.8 mg g−1, very close to the extrapolated value by the Langmuir model (273.9 mg g−1). The salicylic acid adsorbed HCP-EDA-AA resin column was almost regenerated by a mixed desorption solvent including 0.01 mol L−1 of sodium hydroxide (w/v) and 20% of ethanol (v/v). HCP-EDA-AA was repeatedly used nine times and the equilibrium capacity for the ninth time reached 95.5% of the equilibrium capacity for the first time.

A β-naphthol-modified hyper-cross-linked resin for adsorption of p-aminobenzoic acid from aqueous solutions

A β-naphthol-modified hyper-cross-linked resin HJ-G10 was synthesized, characterized, and evaluated for adsorption of p-aminobenzoic acid from aqueous solutions. The adsorption was effective and a higher temperature was more favorable. The Freundlich equation characterized the equilibrium data better, the calculated isosteric enthalpy was positive and decreased with increasing of the equilibrium adsorption amount. The molecular form of p-aminobenzoic acid was favorable for the adsorption and the adsorption in acidic solution was relatively more effective. The pseudo-second-order rate equation fitted the kinetic curves better than the pseudo-first-order rate equation.