The study of adsorption characteristics of electrospun polymer nanofibers for benzenes in water.

The adsorption properties of benzene, p-dichlorobenzene and nitrobenzene on polymer nanofibers were studied. Compared with polyacrylonitrile nanofiber, polystyrene (PS) nanofiber presented better adsorption performance. Langmuir and Freundlich adsorption models were used for the mathematical description of adsorption equilibria, and Freundlich isotherms fitted better. Kinetic studies showed that the adsorption of PS nanofiber followed pseudo first-order model. Various thermodynamic parameters such as standard free energy (delta G), enthalpy (delta H) and entropy (delta S) were calculated for predicting the adsorption nature of PS nanofiber for three benzenes, which indicated that the adsorption was spontaneous and a physical process. The regeneration efficiency maintains over 80% after five cycles of adsorption/desorption tests. It showed that PS nanofibers are promising candidates for adsorption and removal of aromatic hydrocarbons from water.

Application of nanofiber-packed SPE for determination of salivary-free cortisol using fluorescence precolumn derivatization and HPLC detection.

Salivary cortisol has emerged as an easy-to-collect biologic marker of stress in many researches. In this study, we present a method for the determination of salivary-free cortisol using HPLC method with fluorescence precolumn derivatization, which is based on a novel extraction from the strongly acidic medium (fluorescent derivatives of cortisol in sulfuric acid medium) by electrospun polystyrene nanofibers packed SPE. For high-throughput sample extraction, an array pretreatment device based on nanofibers packed SPE micro-column was designed. The LOD of cortisol was 0.01 microg/L (S/N=3). The RSDs (n=6) for all analytes were below 8.0%, and the recoveries were 110, 102.4, and 99.4% (n=3) for saliva spiked with 0.1, 10, and 20 microg/L of cortisol, respectively. The proposed method was then successfully applied in the determination of free cortisol in human saliva. The salivary cortisol concentrations in the real samples ranged from 0.22 to 7.45 microg/L. The nanofiber-packed SPE overcame the low extraction recovery and bad clean-up effect of the conventional methods, and increased the sensitivity and selectivity of the method.

Performance of electrospun nanofibers for SPE of drugs from aqueous solutions.

A novel extraction technique was reported. The solid phase material, nanofiber, was prepared by electrospinning using polystyrene. Twenty different drugs (10 microg/L in water) were extracted using 1 mg of nanofibers within 5 min. The analytes can be desorpted from the fibers with 50 microL of the methanol and then monitored by LC coupled to a UV detector. Packed-fiber SPE (PFSPE) provide high recoveries (>50%) for some relatively non-polar drugs (log P >1.5) (n-octanol-to-water partition ratio), and relatively low recoveries (9.9-39.8%) for the drugs within the log P window below 1. Experimental optimization of the technique has been carried out using seven representative drugs, edaravone, cinchonine, quinine, voriconazole, chlordiazepoxide, verapamil, and rutonding. Except for edaravone, the maximum yields of seven drugs (0.2 microg/L) from water samples were approximately 100%, and were 33.7-88.2% from human plasma. The advantageous aspect of the technique encompasses high throughput, high sensitivity, simplicity, low cost, and green chemistry.

A multifunctional wearable sensor based on a graphene/inverse opal cellulose film for simultaneous, in situ monitoring of human motion and sweat.

A multifunctional, wearable sensor based on a reduced oxide graphene (rGO) film onto a porous inverse opal acetylcellulose (IOAC) film has been developed and can perform simultaneous, in situ monitoring of various human motions and ion concentrations in sweat. The rGO film is used as a strain-sensing layer for monitoring human motion via its resistance change, whereas the porous IOAC film is used as a flexible microstructured substrate not only for high sensitive motion sensing, but also for collection and analysis of ion concentrations in sweat by its simple colorimetric changes or reflection-peak shifts. Studies on humans demonstrated that the devices have excellent capability for monitoring various human motions, such as finger bending motion, wrist bending motion, head rotation motion and various small-scale motions of the throat. Simultaneous, in situ analysis of the ion concentration in sweat during these motions shows that the IOAC substrate can detect a wide range of NaCl concentrations in sweat from normal 30 to 680 mM under the conditions of severe dehydration. This investigation provides new horizons toward the design and fabrication of multifunctional, wearable health monitoring devices and the proposed wearable sensor shows promising applications in healthcare and preventive medicine.

Fabrication of photonic crystals with nigrosine-doped poly(MMA-co-DVB-co-MAA) particles.

A convenient approach was developed to fabricate monodisperse nigrosine-doped poly(methyl methacrylate-co-divinylbenzene-co-methacrylic acid) nanoparticles with different cross-linkage by soap-free emulsion polymerization at boiling status and swelling process. The dye-doped nanoparticles were used for the fabrication of colloidal crystal films and beads. It was found that nigrosine dye in the nanoparticles can efficiently depress the light scattering inside the colloidal crystal films and eliminate the iridescent effect in the photonic beads. These results make the colloidal crystals useful in photonic paper, bioassay, and so on.

Mechanical tension applied to substrate films specifies location of neuritogenesis and promotes major neurite growth at the expense of minor neurite development.

One obstacle in neural repair is facilitating axon growth long enough to reach denervated targets. Recent studies show that axonal growth is accelerated by applying tension to bundles of neurites, and additional studies show that mechanical tension is critical to all neurite growth. However, no studies yet describe how individual neurons respond to tensile forces applied to cell bodies and neurites simultaneously; neither do any test motor neurons, a phenotype critical to neural repair. Here we examine the growth of dissociated motor neurons on stretchable substrates. E15 spinal motor neurons were cultured on poly-lactide-co-glycolide films stretched at 4.8, 9.6, or 14.3 mm day(-1). Morphological analysis revealed that substrate stretching has profound effects on developing motor neurons. Stretching increases major neurite length; it also forces neuritogenesis to occur nearest poles of the cell closest to the sources of tension. Stretching also reduces the number of neurites per neuron. These data show that substrate stretching affects neuronal morphology by specifying locations on the cell where neuritogenesis occurs and favoring major neurite growth at the expense of minor neurites. These results serve as a building block for development of new techniques to control and improve the growth of neurons for nerve repair purposes.

Colorimetric photonic hydrogel aptasensor for the screening of heavy metal ions.

We have developed a robust method for the visual detection of heavy metal ions (such as Hg(2+) and Pb(2+)) by using aptamer-functionalized colloidal photonic crystal hydrogel (CPCH) films. The CPCHs were derived from a colloidal crystal array of monodisperse silica nanoparticles, which were polymerized within the polyacrylamide hydrogel. The heavy metal ion-responsive aptamers were then cross-linked in the hydrogel network. During detection, the specific binding of heavy metal ions and cross-linked single-stranded aptamers in the hydrogel network caused the hydrogel to shrink, which was detected as a corresponding blue shift in the Bragg diffraction peak position of the CPCHs. The shift value could be used to estimate, quantitatively, the amount of the target ion. It was demonstrated that our CPCH aptasensor could screen a wide concentration range of heavy metal ions with high selectivity and reversibility. In addition, these aptasensors could be rehydrated from dried gels for storage and aptamer protection. It is anticipated that our technology may also be used in the screening of a broad range of metal ions in food, drugs and the environment.

Factors influencing the transfer of porcine endogenous retroviruses across the membrane in bioartificial livers.

OBJECTIVES: to investigate the factors influencing the transfer of porcine endogenous retroviruses (PERVs) across the membrane in a new bioartificial liver (BAL). METHODS: A new BAL containing 2 circuits was constructed using plasma component separators with membrane pore sizes of 10 nm, 20 nm, 30 nm, and 35 nm, or a plasma filter with a membrane pore size of 500 nm. Cocultured cells of porcine hepatocytes and mesenchymal stem cells or single porcine hepatocytes were incubated in the bioreactors, and the BAL worked for 72 hours, with supernatant samples in internal and external circuits collected every 12 hours. PERV RNA, reverse transcriptase (RT) activity, and in vitro infectivity of the supernatant were detected. RESULTS: With the plasma filters, the results of PERV detection were the same in both circuits. With plasma component separators, PERV RNA was found in the external circuits, but no positive RT activity or HEK293 cell infection was found. The time at which the PERV RNA was first detected varied with the pore size of membrane; the larger the membrane pore size was, the earlier the RNA was detected. The PERV RNA level in the external circuits was reduced significantly compared with that in the internal circuits at any detecting time. CONCLUSIONS: The plasma component separators with membrane pore size =35 nm could significantly reduce the passage of infectious PERVs. And the membrane pore size, the treatment duration, and the viral level in the internal circuit were potential factors influencing the transfer of PERVs across the membrane in a BAL. In addition, a low risk of PERV transmission from porcine hepatocytes to human cells was found.

Rat hepatocyte aggregate formation on discrete aligned nanofibers of type-I collagen-coated poly(L-lactic acid).

Primary hepatocytes cultured in three dimensional tissue constructs composed of multicellular aggregates maintain normal differentiated cellular function in vitro while cultured monolayers do not. Here, we report a technique to induce hepatocyte aggregate formation using type-I collagen-coated poly(L-lactic acid) (PLLA) discrete aligned nanofibers (disAFs) by providing limited cell-substrate adhesion strength and restricting cell migration to uniaxial movement. Kinetics of aggregate formation, morphology and biochemical activities of rat hepatocyte aggregates were tested over a 15 day culture period. Evidence was provided that physical cues from disAFs quickly induced the formation of aggregates. After 3 days in culture, 88.3% of free hepatocytes on disAFs were incorporated into aggregates with an average diameter of 61 +/- 18 microm. Hepatocyte aggregates formed on disAFs displayed excellent cell retention, cell activity and stable functional expression in terms of albumin secretion, urea synthesis and phase I and II (CYP1A and UGT) metabolic enzyme activity compared to monolayer culture of hepatocytes on tissue culture plastic (TCP) with type-I collagen as well as on meshes of type-I collagen-coated PLLA random nanofibers (meshRFs). These results suggest that disAFs may be a suitable method to maintain large-scale hepatic cultures with high activity for tissue engineering research and potential therapeutic applications, such as bioartificial liver devices.

Electrospun chitosan nanofibers for hepatocyte culture.

In this study, we developed a method to obtain high surface area nanofiber meshes composed of chitosan of a number of molecular weights. This method required decreasing the viscosity and surface tension of the chitosan solution as well as optimization of the electrospinning parameters such as applied voltage and environmental humidity. These chitosan nanofiber meshes were developed as a culture substrate for hepatocytes. The fibers exhibited a uniform diameter distribution (average diameter: 112 nm) and FTIR results indicate that the chemical structure of chitosan is stable during the electrospinning process. The attachment, morphology and activity of hepatocytes cultured on the chitosan nanofiber meshes were tested. The results showed that the chitosan nanofibers are biocompatible with hepatocytes and that these chitosan nanofiber meshes could be useful tissue culture substrates for various applications, including bioartificial liver-assist devices and tissue engineering for liver regeneration.

The influence of type-I collagen-coated PLLA aligned nanofibers on growth of blood outgrowth endothelial cells.

Nanofibrous scaffolds have been applied widely in tissue engineering to simulate the nanostructure of natural extracellular matrix (ECM) and promote cell bioactivity. The aim of this study was to design a biocompatible nanofibrous scaffold for blood outgrowth endothelial cells (BOECs) and investigate the interaction between the topography of the nanofibrous scaffold and cell growth. Poly(L-lactic acid) (PLLA) random and aligned nanofibers with a uniform diameter distribution were fabricated by electrospinning. NH(3) plasma etching was used to create a hydrophilic surface on the nanofibers to improve type-I collagen adsorption; the conditions of the NH(3) plasma etching were optimized by XPS and water contact angle analysis. Cell attachment, proliferation, viability, phenotype and morphology of BOECs cultured on type-I collagen-coated PLLA film (col-Film), random fibers (col-RFs) and aligned fibers (col-AFs) were detected over a 7 day culture period. The results showed that collagen-coated PLLA nanofibers improved cell attachment and proliferation; col-AFs induced the directional growth of cells along the aligned nanofibers and enhanced endothelialization. We suggest that col-AFs may be a potential implantable scaffold for vascular tissue engineering.

Photo-bleaching immunity encoded photonic suspension array for label-free multiplex analysis.

A new type of suspension array for multiplex analysis has been proposed by using polarized luminescent ratios of dichroic dyes as the encoding elements, which provided highly stable codes and advantages of label-free detection.