Integration of RAFT polymerization and click chemistry to fabricate PAMPS modified macroporous polypropylene membrane for protein fouling mitigation.

A copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) grafting-to method was used to tether alkyne-terminated poly(2-acrylamido-2-methyl propane sulfonic acid) (alkyne-PAMPS) to the azide functionalized macroporous polypropylene membrane (MPPM-N3). Alkyne-PAMPS was synthesized by the reversible addition-fragmentation chain transfer polymerization (RAFT) of AMPS with an alkyne-terminated trithiocarbonate served as a chain transfer agent. The combination of RAFT polymerization with click chemistry to graft polymer to the surface of polypropylene membrane produced relatively high grafting density and controllable grafting chain length. The structure and composition of the modified and unmodified MPPM surfaces were analyzed by attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS); field emission scanning electron microscopy (FE-SEM) was employed to observe the morphological changes on the membrane surface. The permeation performances were tested by the filtration of protein dispersion. The experimental results show that with the grafting degree going up, the relative flux reduction decreases, while the relative flux recovery ratio increases, and the protein fouling is obviously mitigated by tethering PAMPS to the membrane surface. The modified membranes can be potentially applied for fouling reduction during the filtration of proteins.

DNA nanostructure-based imaging probes and drug carriers.

Self-assembled DNA nanostructures are well-defined nanoscale shapes, with uniform sizes, precise spatial addressability, and excellent biocompatibility. With these features, DNA nanostructures show great potential for biomedical applications; various DNA-based biomedical imaging probes or payload delivery carriers have been developed. In this review, we summarize the recent developments of DNA-based nanostructures as tools for diagnosis and cancer therapy. The biological effects that are brought about by DNA nanostructures are highlighted by in vitro and in vivo imaging, antitumor drug delivery, and immunostimulatory therapy. The challenges and perspectives of DNA nanostructures in the field of nanomedicine are discussed.

Enhanced chemiluminescence of the luminol-AgNO3 system by Ag nanoparticles.

The oxidation reaction of luminol with AgNO(3) can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV-vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol-AgNO(3)-Ag NPs system indicated that the luminophore was still 3-aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO(3), they catalysed the reduction of AgNO(3) by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol-AgNO(3)-Ag NPs CL system were studied by a flow-injection procedure, which led to an effective method for detecting these compounds.

Surface modification of polypropylene macroporous membrane to improve its antifouling characteristics in a submerged membrane-bioreactor: H(2)O plasma treatment.

To improve the antifouling characteristics of polypropylene hollow fiber macroporous membranes in a submerged membrane-bioreactor for wastewater treatment, the membranes were surface modified by H(2)O plasma treatment. Structural and morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM). The change of surface wettability was monitored by contact angle measurement. The static water contact angle of the modified membrane reduced obviously with the increase of plasma treatment time. The total surface free energy and its dispersive component decreased, while the polar component increased with the increase of treatment time. The relative pure water flux for the modified membranes increased gradually with the increase of plasma treatment time. The tensile strength and the tensile elongation at break for the membranes decreased after plasma treatment. After continuous operation in a submerged membrane-bioreactor for about 68 h, flux recovery after water and caustic cleaning, flux ratio after fouling were improved by 2.0, 3.6 and 22.0%, while reduction of flux was reduced by 1.1% for the 1 min H(2)O plasma treated membrane, compared to those of the unmodified membrane.

Surface modification of polypropylene microporous membrane to improve its antifouling characteristics in an SMBR: N2 plasma treatment.

Fouling is the major obstacle in membrane processes applied in water and wastewater treatment. The polypropylene hollow fiber microporous membranes (PPHFMMs) were surface modified by N(2) low-temperature plasma treatment to improve the antifouling characteristics. Morphological changes on the membrane surface were characterized by field emission scanning electron microscopy (FE-SEM). The change of surface wettability was monitored by contact angle measurements. The static water contact angle of the modified membrane reduced obviously; the relative pure water flux of the modified membranes increased with the increase of plasma treatment time. To assess the relation between plasma treatment and membrane fouling in a submerged membrane bioreactor (SMBR), filtration of activated sludge was carried out by using synthetic wastewater. After continuous operation in the SMBR for about 90 h, flux recoveries for the N(2) plasma-treated PPHFMM for 8 min were 62.9% and 67.8% higher than those of the virgin membrane after water and NaOH cleaning. The irreversible fouling resistance decreased after plasma treatment.

Improvement of antifouling characteristics in a bioreactor of polypropylene microporous membrane by the adsorption of Tween 20.

Surface modification by physical adsorption of Tween 20 was accomplished on polypropylene microporous membranes (PPMMs). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR) and field emission scanning electron microscope (FE-SEM) were used to characterize the chemical and morphological changes on the membrane surfaces. Water contact angles and relative pure water fluxes were measured. The data showed that the hydrophilic performance for the modified membranes increased with the increase in the adsorption amount of Tween 20 onto the surface or into the pores of polypropylene microporous membranes. To test the antifouling property of the membranes by the adsorption of Tween 20 in a membrane bioreactor (MBR), filtration for active sludge was performed using synthetic wastewater. With the help of the data of water fluxes and the FE-SEM photos of the modified PPMMs before or after operating in a MBR for about 12 d, the PPMMs with monolayer adsorption of Tween 20 showed higher remained flux and stronger antifouling ability than unmodified membrane and other modification membranes studied.

Enhancement of the flux for polypropylene hollow fiber membrane in a submerged membrane-bioreactor by surface modification.

To improve its limiting flux and antifouling characteristics in a submerged membrane-bioreactor (SMBR) for wastewater treatment, polypropylene hollow fiber microporous membrane (PPHFMM) was surface-modified by the plasma-induced immobilization of poly (N-vinyl-2-pyrrolidone) (PVP) and the plasma treatment with different gases respectively. Attenuated total reflection-Fourier transform infrared spectroscopy (FT-IR/ATR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Water contact angle was measured by the sessile drop method. It was found that the water contact angle was 128.8, 72.3, 62.7, 74.4, 79.1, 86.3, and 71.3 degrees for the nascent, PVP-immobilized, air, O2, Ar, CO2 and H2O plasma treated PPHFMM, respectively. The SMBR was operated at fixed transmembrane pressure to determine the limiting flux for the PPHFMM before and after surface modification. Results showed that the limiting flux appeared to be 103, 159, 117, 133, 136, 121 and 152 L/(m(2)x h) for the nascent, PVP-immobilized, air, 02, Ar, CO2 and H2O plasma treated PPHFMM, respectively. After continuous operation for about 50 h in the SMBR, the antifouling characteristics were improved to some extent.