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Li, DongXiang,Jang, Yu Jin,Lee, Jieun,Lee, Ji-Eun,Kochuveedu, Saji Thomas,Kim, Dong Ha Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.41
<P>Ligand exchange of CTAB-protected gold nanorods (AuNRs) with disulfide initiator was found to usually cause nanorod aggregation, but such aggregation could be prevented under the steric hindrance of pre-anchored poly(ethylene glycol) thiol. The obtained initiator-modified AuNRs were well-dispersed and could initiate the <I>in situ</I> atom-transfer radical polymerization (ATRP) of 4-vinylpyridine, resulting in poly(4-vinylpyridine)-grafted AuNRs as core–shell structures (AuNR@PVP). These polymer/Au nanocomposites displayed pH-responsive surface plasmon resonance changes because of the protonation and deprotonation of pyridine groups. The coordinative polymer shells allowed these structures to be employed as nanosupports for transition metal ions such as platinum ions, which could be reduced to Pt nanoparticles embedded on the surfaces of the AuNRs. Bimetallic nanostructures of Pt-decorated AuNR@PVP nanocomposites exhibited typical catalytic activity for methanol oxidation.</P> <P>Graphic Abstract</P><P>Coordinative poly(4-vinylpyridine) grafted gold nanorods with pH-responsive SPR properties were fabricated and employed as nanosupports for transition metal ions or nanoparticles. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1jm13302k'> </P>
Graphene Oxide Nanosheet-Composited Poly(N-isopropylacrylamide) Hydrogel for Cell Sheet Recovery
Yongqing Xia,Han Wu,Dachao Tang,Shuai Gao,Binghe Chen,Zhujun Zeng,Shengjie Wang,Meiwen Cao,Dongxiang Li 한국고분자학회 2019 Macromolecular Research Vol.27 No.7
Cell sheet engineering technique has been applied to treat various tissues without the use of a traditional scaffold. To date, methods for the cell sheet harvesting depend mostly on grafted poly(N-isopropylacrylamide) (pNIPAAm) thin layers, while the native pNIPAAm hydrogel, which possibly presents the easiest way to prepare thermo-responsive materials, is not suitable for the cell sheet harvesting due to its low cell attachment. In this study, the graphene oxide (GO) nanosheet was utilized as an additive to enhance the bio-compatibility of the pNIPAAm hydrogel. Different concentrations of GO nanosheets were added to prepare GO/pNIPAAm composite hydrogels through the in-situ free radical polymerization with polyethylene glycol dimethacrylate (PEGDA) as a cross-linker. The results indicated that the physical properties of the composite hydrogels had little difference with that of the native pNIPAAm hydrogel. However, the cell attachment, proliferation and detachment behaviors on the composite hydrogel surface were greatly enhanced. Monkey fibroblast COS7 cells attached and proliferated better on the GO/pNIPAAm composite hydrogel, while intact COS7 cell sheets could be harvested from the composite hydrogels by simply lowering the temperature. In contrast, the cells appeared as clusters on the native pNIPAAm hydrogel. Furthermore, when HeLa and COS7 cells were seeded successively onto the micropatterned GO/pNIPAAm hydrogel, there could be the formation of a patterned HeLa/COS7 cell layer. The geometrically patterned GO/pNIPAAm hydrogel may provide an easy-to-prepare material for releasing patterned cell sheets compared to the specific cell-adhesive proteins reported to make patterned cell layers.