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The role of crystallinity on differential attachment/proliferation of osteoblasts and fibroblasts on poly(caprolactone-co-glycolide) polymeric surfaces
Helen CUI, Patrick J. SINKO
Front Mater Sci. 2012, 6 (1): 47-59.
https://doi.org/10.1007/s11706-012-0154-8
The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly(caprolactone-co-glycolide) (PCL/PGA) polymers. PCL/PGA polymers were selected since they reflect both highly crystalline and amorphous materials. PCL/PGA polymeric materials were fabricated by compression molding into thin films. Five compositions, from PCL or PGA to intermediate copolymeric compositions of PCL/PGA in ratios of 25:75, 35:65 and 45:55, were studied. Pure PCL and PGA represented the crystalline materials while the copolymers were amorphous. The polymers/copolymers were characterized using DSC to assess crystallinity, contact angle measurement for hydrophobicity, and AFM for nanotopography. The PCL/PGA films demonstrated similar hydrophobicity and nanotopography whereas they differed significantly in crystallinity. Cell adhesion to and proliferation on PCL/PGA films and proliferation studies were performed using osteoblasts and NIH-3T3 fibroblasts. It was observed that highly crystalline and rigid PCL and PGA surfaces were significantly more efficient in supporting fibroblast growth, whereas amorphous/flexible PCL/PGA 35:65 was significantly more efficient in supporting growth of osteoblasts. This study demonstrated that while chemical composition, hydrophobicity and surface roughness of PCL/PGA polymers were held constant, crystallinity and rigidity of PCL/PGA played major roles in determining cell responses.
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Preparation of poly(N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography
Zong-Jian LIU, Yan-Li LIANG, Fang-Fang GENG, Fang LV, Rong-Ji DAI, Yu-Kui ZHANG, Yu-Lin DENG
Front Mater Sci. 2012, 6 (1): 60-68.
https://doi.org/10.1007/s11706-012-0161-9
Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyrate-functionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl2/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/m2 and 0.0215 chains/nm2, respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution (Mw/Mn=1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.
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