Yadong Yao

Toxicological Effect of ZnO Nanoparticles Based on Bacteria

Streptococcus agalactiae and Staphylococcus aureus are two pathogenetic agents of several infective diseases in humans. Biocidal effects and cellular internalization of ZnO nanoparticles (NPs) on two bacteria are reported, and ZnO NPs have a good bacteriostasis effect. ZnO NPs were synthesized in the EG aqueous system through the hydrolysis of ionic Zn2+ salts. Particle size and shape were controlled by the addition of the various surfactants. Bactericidal tests were performed in an ordinary broth medium on solid agar plates and in liquid systems with different concentrations of ZnO NPs. The biocidal action of ZnO materials was studied by transmission electron microscopy of bacteria ultrathin sections. The results confirmed that bactericidal cells were damaged after ZnO NPs contacted with them, showing both gram-negative membrane and gram-positive membrane disorganization. The surface modification of ZnO NPs causes an increase in membrane permeability and the cellular internalization of these NPs whereas there is a ZnO NP structure change inside the cells.

Construction of a Hierarchical NiCo2S4@PPy Core–Shell Heterostructure Nanotube Array on Ni Foam for a High-Performance Asymmetric Supercapacitor

In this paper, a hierarchical NiCo2S4@polypyrrole core-shell heterostructure nanotube array on Ni foam (NiCo2S4@PPy/NF) was successfully developed as a bind-free electrode for supercapacitors. NiCo2S4@PPy-50/NF obtained under 50 s PPy electrodeposition shows a low charge-transfer resistance (0.31 Ω) and a high area specific capacitance of 9.781 F/cm(2) at a current density of 5 mA/cm(2), which is two times higher than that of pristine NiCo2S4/NF (4.255 F/cm(2)). Furthermore, an asymmetric supercapacitor was assembled using NiCo2S4@PPy-50/NF as positive electrode and activated carbon (AC) as negative electrode. The resulting NiCo2S4@PPy-50/NF//AC device exhibits a high energy density of 34.62 Wh/kg at a power density of 120.19 W/kg with good cycling performance (80.64% of the initial capacitance retention at 50 mA/cm(2) over 2500 cycles). The superior electrochemical performance can be attributed to the combined contribution of both component and unique core-shell heterostructure. The results demonstrate that the NiCo2S4@PPy-50 core-shell heterostructure nanotube array is promising as electrode material for supercapacitors in energy storage.

Preparation of PLLA/PLGA microparticles using solution enhanced dispersion by supercritical fluids (SEDS).

In this work, poly(L-lactic acid)/poly(lactide-co-glycolide) (PLLA/PLGA) microparticles were prepared using the technique of solution-enhanced dispersion by supercritical fluids (SEDS). For comparison, separate PLLA and PLGA microparticles were also produced by the same SEDS process. The produced microparticles were characterized by scanning electron microscopy, laser particle size analyzer, X-ray diffraction, differential scanning calorimetry, Fourier transform infrared spectroscopy, and gas chromatography. Results indicate that PLLA/PLGA microparticles possess sphere-like shapes with smooth surfaces. The mean particle size of PLLA/PLGA microparticles ranges from 1.76 to 2.15 microm, depending on the feeding ratio of PLLA to PLGA used in the SEDS process. The crystallinity of PLLA/PLGA microparticles decreases after the SEDS processing, so that the produced microparticles are in an amorphous state. Pure PLGA was hard to precipitate in small, fine microparticle form without the presence of PLLA. A model drug, paclitaxel, was encapsulated into PLLA/PLGA microparticles by the same SEDS process, and the in vitro release rate of paclitaxel from these PLLA/PLGA composites could be modulated by variation of the mixing ratio PLLA:PLGA. The prepared microparticles have negligible residual organic solvent. Drug-loaded PLLA/PLGA microparticles produced by SEDS have potential as an advanced colloidal suspension for pharmaceutical applications.

Preparation, characterization and in vitro cytotoxicity of indomethacin-loaded PLLA/PLGA microparticles using supercritical CO2 technique.

In this work, indomethacin-loaded poly(l-lactic acid)/poly(lactide-co-glycolide) (IDMC-PLLA/PLGA) microparticles were prepared using solution-enhanced dispersion by supercritical fluids (SEDS) technique in an effort to obtain alternative IDMC formulation for drug delivery system. Surface morphology, particle size and particle size distribution, drug encapsulation efficiency, drug release kinetics, in vitro cytotoxicity and the cellular uptake of drug-loaded microparticles were investigated. The drug-loaded microparticles exhibited sphere-like shape and small particle size with narrow particle size distribution. IDMC was amorphously dispersed within the PLLA/PLGA matrix after the SEDS process. In vitro release studies revealed that the drug-loaded microparticles substantially enhanced the dissolution rate of IDMC compared to the free IDMC, and demonstrated a biphasic drug release profile. In vitro cytotoxicity assays indicated that drug-loaded microparticles possessed longer sustained inhibition activity on proliferation of the non-small-cell lung cancer A549 cell lines than did free IDMC. Fluorescence microscopy and transmission electron microscopy identified the phagocytosis of drug-loaded microparticles into the A549 cells and characteristic morphology of cell apoptosis such as the nuclear aberrations, condensation of chromatin, and swelling damage in mitochondria. These results collectively suggested that IDMC-PLLA/PLGA microparticles prepared using SEDS would have potentials in anti-tumor applications as a controlled drug release dosage form without harmful organic solvent residue.

Localized delivery of growth factors for angiogenesis and bone formation in tissue engineering

Angiogenesis is a key component of bone formation. Delivery of growth factors for both angiogenesis and osteogenesis is about to gain important potential as a future therapeutic tool. This review focuses on these growth factors that have dual functions in angiogenesis and osteogenesis, and their localized application. A major hurdle in the clinical development of growth factor therapy so far is how to assure safe and efficacious therapeutic use of such factors and avoid unwanted side effects and toxicity. It is now firmly established from the available information that the type, dose, combinations and delivery kinetics of growth factors all play a decisive role for the success of growth factor therapy. All of these parameters have to be adapted and optimized for each animal model or clinical case. In this review we discuss some important parameters associated with growth factor therapy and present an overview of selected preclinical studies, followed by a conceptual description of both established and proposed delivery strategies meeting therapeutic needs.

A study on the in vitro degradation properties of poly(l-lactic acid)/β-tricalcuim phosphate(PLLA/β-TCP) scaffold under dynamic loading

The objective of this study was to investigate the effects of dynamic loading on the in vitro degradation properties of poly(L-lactic acid)/beta-tricalcuim phosphate (PLLA/beta-TCP) composite scaffolds. These scaffolds were prepared by a technique, namely solvent self-proliferating/model compressing/particulate leaching, and they were incubated in a customized simulated body fluid (SBF) flow system under dynamic loading conditions for 6 weeks. The bioactivity and the degradation behaviors of the composite scaffolds were systematically investigated through the formation of apatite, the mass and porosity changes, the molecular weight changes of PLLA, the compressive strength changes, etc. Results show a high level of apatite deposition on the scaffolds, suggesting their good bioactivity in the SBF. Changes in mass, porosity, molecular weight and compressive strength of the scaffolds happened more under dynamic loading conditions than that under flow only SBF conditions. Dynamic loading with the investigated frequency promoted the degradation of the scaffolds, but did not markedly deteriorate the mechanical properties of the scaffolds. All the results suggest that the composite scaffolds have great potential to be applied in bone replacements or repairs under the in vivo load-bearing conditions.

Characterization and bacterial response of zinc oxide particles prepared by a biomineralization process.

In this paper, olive-like ZnO particles were successfully synthesized via a facile biomineralization process in the template of silk fibroin (SF) peptide at room temperature. The coat of SF peptide on the surface of ZnO particles had a substantial influence on their morphology during the biomineralization. Room-temperature photoluminescence behavior of ZnO particles indicated that the visible blue emission peak centered at 410 nm was enhanced with the mineralization time. Bacteriological tests revealed that the mineralized ZnO particles with SF peptide were not toxic for Staphylococcus aureus, Escherichia coli, and Streptococcus agalactiae, presenting good cytocompatibility due to the surface coat of peptide. Their potential applications in bio-optical detectors could be envisioned.

Characterization and biological evaluation of paclitaxel-loaded poly(L-lactic acid) microparticles prepared by supercritical CO2.

In this study, paclitaxel loaded poly( L-lactic acid) (PTX-PLLA) microparticles were prepared using solution enhanced dispersion by supercritical CO2(SEDS) technique. This supercritical antisolvent technique offers the advantage of negligible organic solvent residua in the drug loaded microparticles. Scanning electron microscopy (SEM) showed that microparticles exhibited rather spherical shape and small particle size with narrow particle size distribution. X-ray diffraction (XRD) and differential scanning calorimeter (DSC) indicated that PTX was amorphously dispersed in the PLLA matrix. The drug loading and encapsulation efficiency of PTX-PLLA microparticles were 14.33% and 62.68%, respectively. In vitro cytotoxicity evaluation of PTX-PLLA microparticles against nonsmall-cell lung cancer A549 and ovarian cancer SKOV3 cell lines indicated that PTX-PLLA had superior antiproliferation activity against the A549 and SKOV3 cell lines, compared with free PTX formulations. The cellular internalization of fluorescent microparticles was evidenced by fluorescence microscope and further confirmed by transmission electron microscopy (TEM). This was attributed to the efficient intracellular accumulation of PTX via cell phagocytosis and sustained release of PTX from PLLA matrix. The anticancer activity of PTX-PLLA was associated with PTX-induced cell apoptosis such as nuclear aberrations, condensation of chromatin and swelling damage in mitochondria. The cell apoptosis index detected by flow cytometry was higher in PTX-PLLA group than in free PTX. The PTX-PLLA formulation, which was obtained through micronization of PTX and encapsulation of micronized PTX into PLLA simultaneously in the SEDS process, significantly potentiated the anticancer activity of PTX.

In situ surface derivation of an Fe–Co–Bi layer on an Fe-doped Co3O4 nanoarray for efficient water oxidation electrocatalysis under near-neutral conditions

Developing high-performance water oxidation electrocatalysts working under mild conditions is highly desirable, but still remains challenging. In this communication, we report the in situ surface derivation of an Fe–Co–Bi layer (4–7 nm in thickness) on an Fe-doped Co3O4 nanowire array supported on carbon cloth (Fe–Co3O4/CC). As a 3D catalyst electrode for water oxidation, such a core–shell Fe–Co3O4@Fe–Co–Bi nanoarray (Fe–Co3O4@Fe–Co–Bi/CC) demonstrates superior activity over that of a Co3O4-derived nanoarray catalyst, with the need of an overpotential of 420 mV to drive a geometrical catalytic current density of 10 mA cm−2 in 0.1 M potassium borate (pH = 9.2). Notably, this catalyst also shows good long-term stability with high turnover frequencies.

NiCoP Nanoarray: A Superior Pseudocapacitor Electrode with High Areal Capacitance

High-performance supercapacitors require the design and development of electrode materials with high conductivity and a large electrolyte-accessible surface area. Here, the use of a conductive NiCoP nanoarray on nickel foam (NiCoP/NF) as a superior pseudocapacitor electrode is demonstrated. This 3D electrode exhibits high areal capacitances of 9.2 and 5.97 F cm-2 at current densities of 2 and 50 mA cm-2 , respectively, with good rate capability and cycling stability. The asymmetric supercapacitor (ASC) device assembled using NiCoP/NF as positive electrode and active carbon as negative electrode delivers a high energy density of 1.16 mWh cm-2 at a power density of 1.6 mW cm-2 with 72 % retention of its initial specific capacitance after 2000 cycles at 50 mA cm-2 . The practical use is further demonstrated with two such ASC devices in series to light six LED indicators and also to drive an alkaline water electro- lyzer using NiCoP/NF as both cathode and anode for hydrogen production.