Preparation of magnetic attapulgite/polypyrrole nanocomposites for magnetic effervescence-assisted dispersive solid-phase extraction of pyrethroids from honey samples.

In this work, a novel extraction technique based on the effervescence-assisted dispersion and magnetic recovery of attapulgite/polypyrrole sorbents was developed for determining the concentrations of five pyrethroids in honey samples. The magnetic nanoparticles were synthesized by a one-pot method. Several experimental parameters that affected the extraction efficiency, including the dispersion conditions, pH, ionic strength, and desorption conditions, were investigated. Under optimal conditions, the calibration curves for the five pyrethroids in honey samples exhibited good linearity, with r2 values ranging from 0.9979 to 0.9990. The limits of detection varied between 0.21 and 0.34 µg/L. Satisfactory recoveries of 81.42-106.73% with intra- and interday relative standard deviations of less than 6.94 and 10.89%, respectively, were obtained. Moreover, the sorbents exhibited acceptable batch-to-batch repeatability in the range of 5.06-15.01%, and each sorbent could be reused for up to four extraction cycles without a significant loss in the extraction recovery.

Nonwoven polypropylene as a novel extractant phase holder for the determination of insecticides in environmental water samples.

In this work, a novel liquid-phase microextraction approach using nonwoven polypropylene as the extraction solvent holder was developed. Nonwoven polypropylene, a hydrophobic material, is widely used in the cleanup of oil spills. Due to its large surface area, efficient, and full extraction can be achieved. Nonwoven polypropylene containing an ionic liquid was used to extract benzoylurea insecticides (diflubenzuron, teflubenzuron, flufenoxuron, and chlorfluazuron) through vortex-assisted liquid-liquid microextraction. The parameters that affected the extraction efficiency included the type and volume of the extractant, the extraction time, the time and solvent volume for desorption and the mass and surface area of the nonwoven polypropylene. Under the optimized conditions, good linearity was obtained, with coefficients of determination greater than 0.9996, and the limit of detections of these compounds, calculated at S/N = 3, were in the range of 0.73-5.0 ng/mL. The recoveries of the four insecticides at two spiked levels ranged from 93.3 to 102.0%, with relative standard deviations of less than 4.0%. The proposed method was then successfully used for the rapid determination of benzoylurea insecticides in spiked real water samples before liquid chromatographic analysis. The procedure is simple, inexpensive, easy to execute, and can be widely used.

Fabrication of superparamagnetic nanofibrous poly(l-lactic acid)/γ-Fe2 O3 microspheres for cell carriers.

Nanofibrous poly(l-lactic acid) (PLLA) microspheres are extensively studied to be used as cell carriers in the field of tissue engineering because the unique structure can promote cell proliferation and migration. But as injectable scaffold materials, PLLA microspheres easily run off to the soft tissue space because of the lack of cohesive force. It will affect the treatment efficiency and even cause additional inflammatory response. In order to overcome this disadvantage, superparamagnetic γ-Fe2 O3 nanoparticles assisted with oxidative polymerization of dopamine were used for surface modification of PLLA microspheres in this study. The results showed that this surface modification had no obvious cytotoxicity, and the modified microspheres possessed the ability to carry seed cells to controllably move to the defect sites with the guidance of magnetic field, which may be able to increase the repair efficiency. Moreover, the characteristic nanofibrous structure was not destroyed after modification, which was able to promote biological activity of cells. This work provides a novel way to produce superparamagnetic nanofibrous microspheres designed for cell microcarriers. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 511-520, 2019.

Preparation of bioactive ß-tricalcium phosphate microspheres as bone graft substitute materials.

In this study, ß-tricalcium phosphate (Ca3PO4, ß-TCP) microspheres with different diameters were fabricated via a solid-in-oil-in-water (S/O/W) emulsion method. After soaking in simulated body fluid (SBF), the fabricated ß-TCP microspheres were fully covered with a new bone-like apatite layer; subsequent analysis suggested that the microspheres have excellent bioactivity properties, specifically in inducing apatite deposition. The calcium release profiles of the microspheres were tested in pH7.4 Tris-HCl buffer, and results demonstrated that the Ca2+ continually released from microspheres during the two-week test period. We then co-cultured bone marrow stem cells (BMSCs) in vitro with ß-TCP microspheres, and performed SEM and confocal microscope analyses to find that ß-TCP microspheres efficiently promoted BMSC attachment and bone-related gene expression. The co-cultured BMSCs and microspheres were successfully implanted subcutaneously into nude mice for 8weeks. The H&E neo-tissue staining results showed that abundant new bone-like structures had formed between the ß-TCP microspheres, implying that ß-TCP microspheres used as a cell carrier and bone graft substitute material show highly promising potential application for irregular-shaped bone defect regeneration.

Magnetic mixed hemimicelles dispersive solid-phase extraction based on ionic liquid-coated attapulgite/polyaniline-polypyrrole/Fe3O4 nanocomposites for determination of acaricides in fruit juice prior to high-performance liquid chromatography-diode array detection.

In this research, a novel method using magnetic mixed hemimicelles dispersive solid-phase extraction (MMHDSPE) based on C16mimBr-coated attapulgite/polyaniline-polypyrrole/Fe3O4 (ATP/PANI-PPY/Fe3O4) nanocomposites were investigated for enrichment and separation of three acaricides in fruit juice. In this method, we combined the simplicity and speed of dispersive solid-phase extraction, the advantages of mixed hemimicelles and the facility of the phase separation of the magnetic nanoparticles to develop a simple, rapid, sensitive, and effective method for detecting target analytes from the juice samples. ATP/PANI-PPY/Fe3O4 nanocomposites were successfully synthesized using a one-pot method. The as-prepared nanocomposite sorbents were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental factors affecting the extraction efficiency including the sorbent type, amount of ATP/PANI-PPY/Fe3O4 nanocomposites, volume of ILs, sonication time, pH, and desorption conditions were optimized. Under the optimal conditions, good linearity was observed for all target analytes, with correlation coefficients (r2) ranging from 0.9994 to 0.9999; the limits of detection (LOD) were in the range of 0.16-0.57µgL-1, and the recoveries of analytes using the proposed method ranged between 88.67% and 95.10%. The sorbents exhibited excellent repeatability in the range of 1.83-4.24% in extracting the three target analytes. In addition, the intra-day and inter-day precision values were found to be in the range of 0.19-6.24% and 2.23-8.36%, respectively. The method was successfully applied to analyze fruit juice samples by rapid preconcentration of acaricides.

[Determination of lignin content in tiny Panax ginseng by UV spectrophotometry].

OBJECTIVE: To establish the UV spectrophotometry for determining lignin content in tiny Panax ginseng powder. METHODS: Classical Klason method and UV spectrophotometry were used. RESULTS: The lignin contents measured by UV spectrophotometry were higher, more repeatable and accurate as comparison with the Klason method. The specific absorptance peak of ginseng lignin appeared at 260 nm. The acetyl bromide treatment of the UV spectrophotometry was processed for ginseng powder at 70 degrees C for 30 minutes. It is also concluded that the lignin contents were obvious different among various ginsengs. CONCLUSION: UV spectrophotometry is simple, accurate and just need a little materials. It is especially suitable to determine the lignin content for ginseng and other precious Chinese traditional medicines.

A pilot study of conically graded chitosan-gelatin hydrogel/PLGA scaffold with dual-delivery of TGF-ß1 and BMP-2 for regeneration of cartilage-bone interface.

Repair of cartilage-bone interface tissue remains challenging, because it combines different cell types and gradients of composition and properties. To enable simultaneous regeneration of bone, cartilage, and especially their interface, a conically graded scaffold of chitosan-gelatin hydrogel/poly(l-lactide-co-glycolide) (PLGA) was facilely prepared in the study. The chitosan-gelatin hydrogel containing transforming growth factor ß1 (TGF-ß1) was used for chondrogenesis, while the PLGA scaffold loading bone morphogenetic protein-2 (BMP-2) for osteogenesis. The conically graded transition from the hydrogel to PLGA scaffold and graded variation in amount of growth factors from TGF-ß1 to BMP-2 benefited the cartilage-bone interface reconstruction. The graded scaffold exhibited spatio-temporal delivery of TGF-ß1 and BMP-2. Preliminary results of in vitro cell culture demonstrated that the hydrogel and PLGA phases could promote bone marrow mesenchymal stem cells toward chondrogenic and osteogenic differentiation, respectively. From the result of the pilot in vivo experiment, it showed that the regenerated hyaline-like cartilage surface and subchondral bone excellently integrated with the native tissues were found by using the TGF-ß1 and BMP-2 double-loaded hydrogel/PLGA graded scaffold via H&E and immunohistochemical stainings of collagen I, collagen II, and osteocalcin at 2 months. The obtained preliminary experiment results showed that the hydrogel/PLGA graded scaffold combining multiphasic composition and spatial dual growth-factor delivery would be useful for cartilage-bone interface tissue defect repair.

Flexible 3D porous CuO nanowire arrays for enzymeless glucose sensing: in situ engineered versus ex situ piled.

Convenient determination of glucose in a sensitive, reliable and cost-effective way has aroused sustained research passion, bringing along assiduous investigation of high-performance electroactive nanomaterials to build enzymeless sensors. In addition to the intrinsic electrocatalytic capability of the sensing materials, electrode architecture at the microscale is also crucial for fully enhancing the performance. In this work, free-standing porous CuO nanowire (NW) was taken as a model sensing material to illustrate this point, where an in situ formed 3D CuO nanowire array (NWA) and CuO nanowires pile (NWP) immobilized with polymer binder by conventional drop-casting technique were both studied for enzymeless glucose sensing. The NWA electrode exhibited greatly promoted electrochemistry characterized by decreased overpotential for electro-oxidation of glucose and over 5-fold higher sensitivity compared to the NWP counterpart, benefiting from the binder-free nanoarray structure. Besides, its sensing performance was also satisfying in terms of rapidness, selectivity and durability. Further, the CuO NWA was utilized to fabricate a flexible sensor which showed excellent performance stability against mechanical bending. Thanks to its favorable electrode architecture, the CuO NWA is believed to offer opportunities for building high-efficiency flexible electrochemical devices.

Performance of a multilayered small-diameter vascular scaffold dual-loaded with VEGF and PDGF.

The urgent needs of functional arterial replacements for curing the vascular system diseases have been proposed for many years. However, an ideal small-diameter vascular scaffold, which is nonthrombogenic, minimizes intimal hyperplasia, matches the mechanical properties of natural vessels, and supports neovascular tissue reconstruction, is still in progress. For this purpose, we previously attempted dual-delivery of VEGF and PDGF by double-layered electrospun membranes. Here, a multilayered vascular scaffold in 1.5-mm diameter with sufficient mechanical properties was developed by electrospinning from poly(ethylene glycol)-b-poly(L-lactide-co-ε-caprolactone) (PELCL), poly(L-lactide-co-glycolide) (PLGA), poly(ε-caprolactone) (PCL) and gelatin. Spatio-temporal releases of vascular endothelial growth factor (VEGF) and platelet-derived growth factor-bb (PDGF) were specially controlled by the inner PELCL and middle PLGA layers, respectively, and the outer PCL layer contributed to the mechanical stability. Introduction of gelatin improved vascular endothelial cells adhesion at first, and loosen membrane after its degradation facilitated vascular smooth muscle cells (VSMCs) ingrowth. Cell activities indicated dual release of growth factors promoted endothelialization and inhibited VSMCs hyperproliferation. The small-diameter vascular scaffold dual-loading VEGF and PDGF could maintain patency in rabbit left common carotid artery for 8 weeks. It is concluded that the specially prepared fibrous scaffold in multilayer could benefit blood vessel reconstruction.

Facile preparation and upconversion luminescence of graphene quantum dots.

A facile hydrazine hydrate reduction of graphene oxide (GO) with surface-passivated by a polyethylene glycol (PEG) method for the fabrication of graphene quantum dots (GQDs) with frequency upconverted emission is presented. And we speculate on the upconversion luminescence due to the anti-Stokes photoluminescence (ASPL), where the δE between the π and σ orbitals is near 1.1 eV.

Physically controlled cross-linking in gelated crystalline colloidal array photonic crystals.

We prepared a poly(vinyl alcohol) (PVA) gelated crystalline colloidal array (GCCA) through physical cross-linking. PVA hydrogel was formed by utilizing a chilling-thawing method while the CCA was physically immobilized within the PVA hydrogel matrix. After being chilled at 2 degrees C for 24 h, the gel could be formed without disturbing the CCA. With the repetition of chilling-thawing cycle, the hydrogel network was reinforced. This photonic crystal material could be shaped as needed and efficiently diffracts visible light, and the diffraction wavelength can be tuned anywhere within the visible spectrum by simply varying the CCA concentration. The GCCA represents sol-gel reversibility as the temperature is cycled. It has been observed that the GCCA retained its ability of diffraction after rehydration, and the sample could be stored for long periods of time. We further functionalized the PVA hydrogel with Chitosan (CS), and the pH sensing behavior of the PVA/CS GCCA was observed. It revealed that the sensitivity of the PVA/CS GCCA correlates with the CS concentration.

An enhanced biosensor for glutamate based on self-assembled carbon nanotubes and dendrimer-encapsulated platinum nanobiocomposites-doped polypyrrole film.

An enhanced amperometric biosensor based on incorporating one kind of unique nanobiocomposite as dopant within an electropolymerized polypyrrole film has been investigated. The nanobiocomposite was synthesized by self-assembling glutamate dehydrogenase (GLDH) and poly(amidoamine) dendrimer-encapsulated platinum nanoparticles (Pt-DENs) onto multiwall carbon nanotubes (CNTs). Zeta-potentials and high-resolution transmission electron microscopy (HRTEM) confirmed the uniform growth of the layer-by-layer nanostructures onto the carboxyl-functionalized CNTs. The size of Pt nanoparticles is approximately 3 nm. The (GLDH/Pt-DENs)n/CNTs/Ppy hybrid film was obtained by electropolymerization of pyrrole onto glassy carbon electrodes and characterized with scanning electron microscopy (SEM), cyclic voltammetry (CV) and other electrochemical measurements. All methods indicated that the (GLDH/Pt-DENs)n/CNTs nanobiocomposites were entrapped within the porous polypyrrole film and resulted in a hybrid film that showed a high electrocatalytic ability toward the oxidation of glutamate at a potential 0.2 V versus Ag/AgCl. The biosensor shows performance characteristics with high sensitivity (51.48 microA mM(-1)), rapid response (within 3 s), low detection limit (about 10 nM), low level of interference and excellent reproducibility and stability.