Interpenetrating network hydrogels via simultaneous "click chemistry" and atom transfer radical polymerization.

Simultaneous interpenetrating polymer networks (sIPNs) from concurrent copper(I)-catalyzed azide-alkyne cycloaddition "click chemistry" and atom transfer radical polymerization (ATRP) are described. Semi-sIPN of poly(ethylene glycol)/poly(2-hydroxyethyl methacrylate) (semi-PEG/PHEMA-sIPN) was first prepared via simultaneous "click chemistry" and ATRP from a mixture of poly(ethylene glycol)-diazide (N3-PEG-N3, Mn=4000 g/mol), tetrakis(2-propynyloxymethyl)methane (TPOM), ethyl-2-bromobutyrate (EBB), CuBr, pentamethyldiethylenetriamine (PMDETA), and 2-hydroxyethyl methacrylate (HEMA) in dimethylformamide (DMF). Full sIPN of PEG/PHEMA (full-PEG/PHEMA-sIPN) was then prepared via simultaneous "click chemistry" and ATRP from a mixture of N3-PEG-N3 (Mn=4000 g/mol), TPOM, EBB, CuBr, PMDETA, HEMA, and poly(ethylene glycol) diacrylate) (PEGDA, Mn=575) in DMF. Both the semi- and full-sIPNs exhibit a fast gelation rate and high gel yield. The sIPNs also exhibit high swelling ratios and good mechanical and antifouling properties. The morphology and thermal behavior of the sIPNs were studied by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). These sIPNs could find applications as biomaterials for contact lenses, biomedical materials, artificial organs, and drug delivery systems.

Smart nanofibers from combined living radical polymerization, "click chemistry", and electrospinning.

A simple method for preparing solvent-resistant nanofibers with a thermal-sensitive surface has been developed by the combined technology of reversible addition-fragmentation chain-transfer (RAFT) polymerization, atom transfer radical polymerization (ATRP), electrospinning, and "click chemistry". Initially, well-defined block copolymers of 4-vinylbenzyl chloride (VBC) and glycidyl methacrylate (GMA) (PVBC-b-PGMA) were prepared via RAFT polymerization. Electrospinning of PVBC-b-PGMA from a solution in tetrahydrofuran gave rise to fibers with diameters in the range of 0.4-1.5 microm. Exposure to a solution of sodium azide (NaN(3)) not only affords nanofibers with azido groups on the surface but also leads to a cross-linking structure in the nanofibers. One more step of "click chemistry" between the PVBC-b-PGMA nanofibers with azido groups on the surface (PVBC-b-PGMA(-N3)) and alkyne-terminated polymers of N-isopropylacrylamide (NIPAM) (PNIPAM(AT)), which were prepared by ATRP, allows the preparation of a PVBC-b-PGMA nanofiber with thermal-sensitive PNIPAM brushes on the surface (PVBC-b-PGMA-g-PNIPAM). PVBC-b-PGMA-g-PNIPAM nanofibers exhibit a good resistance to solvents and thermal-responsive character to the environment, having a hydrophobic surface at 45 degrees C (water contact angle approximately 140 degrees) and having a hydrophilic surface at 20 degrees C (water contact angle approximately 30 degrees).

Three-dimensionally ordered porous membranes prepared via self-assembly and reverse micelle formation from well-defined amphiphilic block copolymers.

Block copolymers of poly(pentafluorostyrene) (PFS) and poly(tert-butyl acrylate) (PtBA), or PFS-b-PtBA copolymers, were synthesized via consecutive atom transfer radical polymerizations (ATRPs). Amphiphilic block copolymers of PFS and poly(acrylic acid) (PFS-b-PAAC copolymers) were prepared via hydrolysis of the corresponding PFS-b-PtBA copolymers. The chemical structure and composition of the PFS-b-PtBA and PFS-b-PAAC block copolymers were studied by nuclear magnetic resonance (NMR) spectroscopy, themogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The amphiphilic PFS-b-PAAC copolymers were cast into porous membranes by phase inversion in aqueous media. The surface and cross-sectional morphology of the PFS-b-PAAC membranes were studied by scanning electron microscopy (SEM). Membranes with well-defined pores of sizes in the micrometer range were obtained as a result of inverse micelle formation. The pH of the aqueous media for phase inversion and the PAAC content in the PFS-b-PAAC copolymers could be used to adjust the pore size of the membranes.

Protein kinase C and intracellular calcium are involved in follicle-stimulating hormone-mediated meiotic resumption of cumulus cell-enclosed porcine oocytes in hypoxanthine-supplemented medium.

The present experiments were conducted to examine the hypothesis that follicle-stimulating hormone (FSH) can stimulate the hydrolysis of phosphoinositide, generating the intracellular second messengers to activate protein kinase C and mobilizing intracellular calcium, thus inducing oocyte meiotic resumption. Pig cumulus cell-enclosed oocytes (CEO) were cultured for 24 hr in 4 mM hypoxanthine (HX)-supplemented medium and treated with different agents in the following designs: (1) CEO were treated with neomycin (an inhibitor of phosphoinositide hydrolysis) in the presence of FSH or only treated with 7,12-dimethylbenzin(a) anthracene (DMBA, a tumor promoter which can cause phosphorylation of phospholipase C (PLC), formation of inositol triphophate, and mobilization of intracellular calcium) to mimic the direct activation of PLC; (2) CEO were challenged by FSH, together with sphingosine or staurosporine (two kinds of PKC inhibitors); or treated with phorbol myristate acetate (PMA, an activator of PKC) separately; (3) CEO were primed with BAPTA/AM (an intracellular calcium chelator) or BAPTA/AM +FSH for 60 min, and then transferred into a new culture medium supplemented with FSH but without BAPTA/AM; total culture time was 24 hr. At the end of the culture, the incidence of germinal vesicle breakdown (GVBD) was calculated. The results showed that: (1) FSH (100 U/liter) could stimulate pig CEO to override the arrest of HX and resume meiosis; DMBA (10(-8)-10(-5) M) itself also had such a kind of effect; whereas neomycin, at the level of 10-20 mM, could dramatically inhibit the stimulatory effect of FSH. (2) Staurosporine (10(-9)-10(-6) M) or sphingosine (10(-8)-10(-5) M) could also inhibit the effect of FSH in a dose-dependent manner on stimulating CEO to resume meiosis. However, PMA (10(-8)-10(-5) M) alone had a dual effect on the meiotic resumption of pig CEO. PMA, at the level of 10(-8)-10(-6) M, could stimulate CEO to resume meiosis, and at high concentration of 10(-5) M , it could even enhance the inhibitory effect of HX. (3) Priming CEO with BAPTA/AM only or BAPTA/AM +FSH for 60 min could significantly inhibit the effect of FSH in a dose-dependent manner. These results indicate that in the process of ligand-mediated meiotic resumption of pig CEO, FSH can stimulate the hydrolysis of phosphoinositide leading to the activation of PKC and mobilization of intracellular calcium; and suggest that multiple signaling pathways and signal interaction are involved in this process.