Co-reporter:XiuJuan Shi;Dan Li;Jing Xie;Shawn Wang;ZhaoQiang Wu
Science Bulletin 2012 Volume 57( Issue 10) pp:1109-1115
Publication Date(Web):2012 April
DOI:10.1007/s11434-011-4741-3
The interactions between bovine serum albumin (BSA) and gold nanoparticles (AuNPs), and the conformational changes of BSA induced by this interaction, were investigated by UV-visible absorption spectroscopy, fluorescence spectroscopy, and Fourier transform infrared in combination with attenuated total reflection spectroscopy (ATR-FTIR). The critical adsorption density for preventing AuNP aggregation in 0.1 mol/L phosphate buffered saline (pH 7.2) was 23 BSA molecules per gold particle or 3.8×1012 BSA molecules/cm2. BSA bound to the AuNPs with high affinity (binding constant Ks=7.59×108 L/mol), and the intrinsic fluorescence of BSA was quenched by the AuNPs in accordance with the static quenching mechanism. Both fluorescence spectroscopy and ATR-FTIR showed that AuNPs induced conformational changes in BSA, which resulted in it becoming less compact and increased the polarity of the microenvironment around the tryptophan residue Trp-212.
Co-reporter:Qian Yu, Yanxia Zhang, Hong Chen, Zhaoqiang Wu, He Huang, Chi Cheng
Colloids and Surfaces B: Biointerfaces 2010 Volume 76(Issue 2) pp:468-474
Publication Date(Web):1 April 2010
DOI:10.1016/j.colsurfb.2009.12.006
In this work, we investigated the protein adsorption on the end-tethered thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes with varying grafted layer thickness prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) on initiator-immobilized silicon surfaces. The thickness of a grafted layer was modulated by adjusting reaction time and/or solvent composition. The surface properties as a function of thickness were investigated by water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). The influence of PNIPAAm-grafted layer thickness on human serum albumin (HSA) adsorption in phosphate-buffered saline (PBS) (pH 7.4) at different temperature was evaluated using a radiolabeling method. In a lower thickness range (<15 nm), protein adsorption on PNIPAAm-grafted layer shows a thermoresponsive change in a certain extent, but the variation is not remarkable. However, it is interesting to observe that these surfaces exhibit good protein-resistant property. For the surface with a PNIPAAm thickness of 13.4 nm, the HSA adsorption level measured at room temperature was ∼7 ng/cm2, corresponding to a reduction of 97% compared to the unmodified silicon surface. For thicker PNIPAAm-grafted surface with thickness of 38.1 nm, the adsorption results of three proteins (HSA, fibrinogen, and lysozyme) with different sizes and charges indicate that the PNIPAAm-modified surface exhibits a size-sensitive property of protein adsorption.
Co-reporter:Jun Zheng, Wei Song, He Huang, Hong Chen
Colloids and Surfaces B: Biointerfaces 2010 Volume 77(Issue 2) pp:234-239
Publication Date(Web):1 June 2010
DOI:10.1016/j.colsurfb.2010.01.032
Lotus leaf-like polyurethane/Pluronic® F-127 surface was fabricated via replica molding using a natural lotus leaf as the template. Water contact angle measurements showed that both the hydrophobicity of the unmodified polyurethane (PU) surface and the hydrophilicity of the PU/Pluronic® surface were enhanced by the construction of lotus leaf-like topography. Protein adsorption on the PU/Pluronic® surface without topographic modification was significantly lower than on the PU surface. Adsorption was further reduced when lotus leaf-like topography was constructed on the PU/Pluronic® surface. Cell culture experiments with L929 cells showed that adhesion on the PU/Pluronic® surface with lotus leaf-like topography was low and adherent cells were spherical and of low viability. The PU/Pluronic® surface with lotus leaf-like topography thus appears to be resistant to nonspecific protein adsorption and to cell adhesion, and these effects derive from the both chemical composition and topography. The results suggest a new strategy based on surface topography for the design of antifouling materials.
Co-reporter:Qian Yu, Yanxia Zhang, Hong Chen, Feng Zhou, Zhaoqiang Wu, He Huang and John L. Brash
Langmuir 2010 Volume 26(Issue 11) pp:8582-8588
Publication Date(Web):February 19, 2010
DOI:10.1021/la904663m
Diblock copolymer grafts covalently attached to surfaces have attracted considerable attention because of their special structure and novel properties. In this work, poly(N-isopropylacrylamide)-block-polystyrene (PNIPAAm-b-PS) brushes were prepared via surface-initiated consecutive atom-transfer radical polymerization on initiator-immobilized silicon. Because of the inherent thermosensitivity of PNIPAAm and the hydrophobicity difference between the two blocks, the modified surfaces were responsive to both temperature and solvent. Moreover, the diblock copolymer brushes exhibited both resistance to nonspecific protein adsorption and unique cell interaction properties. They showed strong protein resistance in both phosphate-buffered saline and blood plasma. In particular, fibrinogen adsorption from plasma at either room temperature or body temperature was less than 8 ng/cm2, suggesting that the surfaces might possess good blood compatibility. In addition, the adhesion and detachment of L929 cells could be “tuned”, and the ability to control the detachment of cells thermally was restored by block polymerization of hydrophobic, cell-adhesive PS onto a thicker PNIPAAm layer. In addition to providing a simple and effective design for advanced cell-culture surfaces, these results suggest new biomedical applications for PNIPAAm.
Co-reporter:Jinbo Gan, Hong Chen, Feng Zhou, He Huang, Jun Zheng, Wei Song, Lin Yuan, Zhongkui Wu
Colloids and Surfaces B: Biointerfaces 2010 Volume 76(Issue 1) pp:381-385
Publication Date(Web):1 March 2010
DOI:10.1016/j.colsurfb.2009.11.013
Cell patterning on substrates has played a significant role in the study of basic biology, cell-based biosensor and tissue engineering. In this report, a cell pattern was prepared on poly(dimethylsiloxane) (PDMS) substrate by vacuum ultraviolet (VUV) lithography. After immobilizing allyl-polyethylene glycol (APEG) onto PDMS, a chemical heterogeneous patterned surface was fabricated by VUV (Xe2 excimer: 172 nm) lithography with copper mesh as a photomask. The UV exposed domains can promote L929 cell adhesion and growth. However, non-exposed regions resist cell attachment because of the repelling property of PEG. Therefore, cell pattern could be achieved without pre-adsorption of cell adhesive species before cell culture.
Co-reporter:Dan Li, Hong Chen, W. Glenn McClung, John L. Brash
Acta Biomaterialia 2009 Volume 5(Issue 6) pp:1864-1871
Publication Date(Web):July 2009
DOI:10.1016/j.actbio.2009.03.001
Abstract
Fibrinolytic polyurethane surfaces were prepared by conjugating lysine to the distal terminus of surface-grafted poly(ethylene glycol) (PEG). Conjugation was through the α-amino group leaving the ε-amino group free. Lysine in this form is expected to adsorb both plasminogen and t-PA specifically from blood. It was shown in previous work that the PEG spacer, while effectively resisting nonspecific protein adsorption, was a deterrent to the specific binding of plasminogen. In the present work, the effects of PEG spacer chain length on the balance of nonspecific and specific protein binding were investigated. PEG–lysine (PEG-Lys) surfaces were prepared using PEGs of different molecular weight (PEG300 and PEG1000). The lysine-derivatized surfaces with either PEG300 or PEG1000 as spacer showed good resistance to fibrinogen in buffer. The PEG300-Lys surface adsorbed plasminogen from plasma more rapidly than the PEG1000-Lys surface. The PEG300-Lys was also more effective in lysing fibrin formed on the surface. These results suggest that the optimum spacer length for protein resistance and plasminogen binding is relatively short. Immunoblots of proteins eluted after plasma contact confirmed that the PEG–lysine surface adsorbed plasminogen while resisting most of the other plasma proteins. The hemocompatibility of the optimized PEG–lysine surface was further assessed in whole blood experiments in which fibrinogen adsorption and platelet adhesion were measured simultaneously. Platelet adhesion was shown to be strongly correlated with fibrinogen adsorption. Platelet adhesion was very low on the PEG-containing surfaces and neither surface-bound lysine nor adsorbed plasminogen promoted platelet adhesion.
Co-reporter:Zhaoqiang Wu;He Huang;Tieliang Zhao;Xiaoli Liu;Dan Li;Qian Yu
Macromolecular Bioscience 2009 Volume 9( Issue 12) pp:1165-1168
Publication Date(Web):
DOI:10.1002/mabi.200900221
Co-reporter:Zhongkui Wu, Haiying Yan, Hong Chen, He Huang
Applied Surface Science 2009 Volume 255(Issue 8) pp:4702-4704
Publication Date(Web):1 February 2009
DOI:10.1016/j.apsusc.2008.11.083
Abstract
A sub-micron hydrophilic microchannel was fabricated on poly(dimethylsiloxane) (PDMS) in one step using vacuum ultraviolet light (VUV) lithography in vacuum. The topographies and properties of the irradiated PDMS surface were characterized and analyzed by atomic force microscopy (AFM), and the chemical composition changes on VUV-treated PDMS analyzed by X-ray photoelectron spectroscopy (XPS). The hydrophilic stability of irradiated PDMS surface was studied by static water contact angle. As demonstrated, the hydrophilicity on surface of PDMS microchannel can be kept for a longer term even three months after the treatment.
Co-reporter:Hong Chen;Yanxia Zhang;Dan Li;Xiaoyang Hu;Liang Wang;W. Glenn McClung;John L. Brash
Journal of Biomedical Materials Research Part A 2009 Volume 90A( Issue 3) pp:940-946
Publication Date(Web):
DOI:10.1002/jbm.a.32152
Abstract
The objective of this work is to develop a blood contacting surface that possesses both resistance to nonspecific protein adsorption and clot lysing properties. Chemical modification of a polyurethane (PU) surface with poly(ethylene glycol) (PEG); and lysine was used to create a plasminogen-binding potentially fibrinolytic surface. The preparation involves modification of the PU surface with dihydroxy PEG, reaction of the unreacted distal OH with N,N′-disuccinimidyl carbonate (DSC) to produce a PU-PEG-NHS surface, followed by conjugation of ε-amino-protected lysine (H-Lys(t-BOC)-OH) by reaction of the α-amino group with the NHS and deprotection. The result is a lysine-derivatized surface in which the ε-amino groups of the lysine are free to participate in binding plasminogen and tissue plasminogen activator (t-PA). Surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Protein adsorption experiments showed that nonspecific protein adsorption was greatly reduced on these surfaces and that they adsorbed significant quantities of plasminogen from plasma. After incubation with plasma and treatment with t-PA the surfaces were able to dissolve nascent plasma clots formed around them. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Co-reporter:Zhaoqiang Wu, Hong Chen, Xiaoli Liu, Yanxia Zhang, Dan Li and He Huang
Langmuir 2009 Volume 25(Issue 5) pp:2900-2906
Publication Date(Web):February 3, 2009
DOI:10.1021/la8037523
Well-controlled poly(N-vinylpyrrolidone) (PVP)-grafted silicon surfaces were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) with 1,4-dioxane/water mixtures as solvents and CuCl/5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Me6TATD) as a catalyst. The thickness of the PVP layer on the surface increased with reaction time, suggesting that the ATRP grafting of N-vinylpyrrolidone (NVP) from the silicon surfaces was a well-controlled process. The water contact angle and X-ray photoelectron spectroscopy (XPS) were used to characterize the modified surfaces. The protein adsorption property of the PVP-grafted surfaces was evaluated using a radiolabeling method. Compared with unmodified silicon surfaces, a Si−PVP60 surface with a PVP thickness of 15.06 nm reduced the level of adsorption of fibrinogen, human serum albumin (HSA), and lysozyme by 75, 93, and 81%, respectively. Moreover, the level of fibrinogen adsorption decreases gradually with an increase in PVP thickness. However, no significant difference in fibrinogen adsorption was found when the PVP layer was thicker than the critical thickness of 13.45 nm.
Co-reporter:Lin Yuan, Zhi Yue, Hong Chen, He Huang, Tieliang Zhao
Colloids and Surfaces B: Biointerfaces 2009 Volume 73(Issue 2) pp:346-350
Publication Date(Web):15 October 2009
DOI:10.1016/j.colsurfb.2009.06.003
It is well known that the sulfate groups on different positions in polysaccharides play important roles in protein adsorption. However, the interactions between sulfated chitosans and lysozyme have not been clearly elucidated. In this study, the regioselectively sulfated chitosans, 6-O-sulfated chitosan (C6S), 2-N-6-O-sulfated chitosan (C26S) and 3,6-O-sulfated chitosan (C36S), were chosen to investigate the possible mechanisms determining the interaction between lysozyme and the sulfated chitosans. It has been found that the selectively sulfated products of chitosan (CS), C6S, C26S and C36S all exhibit lysozyme binding activity. However, the maximum binding ratios of lysozyme/polysaccharide are significantly different for C6S, C26S and C36S. In addition, though C6S possesses the lowest sulfur content among the three sulfated chitosans, it exhibits the highest binding activity with lysozyme. Furthermore, in the protein mixtures, C6S shows the highest selective binding activity with lysozyme among the three sulfated chitosans in the presence of γ-globulin and bovine serum albumin (BSA). The results indicate that 6-O-sulfate groups may be responsible for the high affinity and specific interaction of sulfated chitosan with lysozyme, while 2-O-sulfate and 3-O-sulfate groups are unfavorable to this interaction.
Co-reporter:Zhongkui Wu, Libin Ding, Hong Chen, Lin Yuan, He Huang, Wei Song
Colloids and Surfaces B: Biointerfaces 2009 Volume 69(Issue 1) pp:71-76
Publication Date(Web):15 February 2009
DOI:10.1016/j.colsurfb.2008.11.001
Over the last decade, the chelator-based strategy for protein immobilization has received considerable attention. Here, we describe a stepwise approach for the modification of polyurethane (PU) surfaces which involves the introduction of a poly(ethylene glycol) (PEG) layer to shield the PU substrate surface against nonspecific protein adsorption and a chelator head (quinolin-8-ol, HQ), to provide relatively high-target protein binding capacity. The surface properties, the immobilization of proteins on the surface, and the bioactivity of the immobilized proteins were investigated by various techniques. It was demonstrated that this approach provides a powerful means for surface immobilization of proteins with high density, with a homogeneous distribution and retaining the bioactivity of the immobilized proteins.
Co-reporter:Hong Chen, Wei Song, Feng Zhou, Zhongkui Wu, He Huang, Junhu Zhang, Quan Lin, Bai Yang
Colloids and Surfaces B: Biointerfaces 2009 Volume 71(Issue 2) pp:275-281
Publication Date(Web):1 July 2009
DOI:10.1016/j.colsurfb.2009.02.018
Chemical homogeneous poly(dimethylsiloxane) (PDMS) surface with dot-like protrusion pattern was used to investigate the individual effect of surface microtopography on protein adsorption and subsequent biological responses. Fibrinogen (Fg) and fibronectin (Fn) were chosen as model proteins due to their effect on platelet and cell adhesion, respectively. Fg labeled with 125I and fluorescein isothiocyanate (FITC) was used to study its adsorption on flat and patterned surfaces. Patterned surface has a 46% increase in the adsorption of Fg when compared with flat surface. However, the surface area of the patterned surface was only 8% larger than that of the flat surface. Therefore, the increase in the surface area was not the only factor responsible for the increase in protein adsorption. Clear fluorescent pattern was visualized on patterned surface, indicating that adsorbed Fg regularly distributed and adsorbed most on the flanks and valleys of the protrusions. Such distribution and local enrichment of Fg presumably caused the specific location of platelets adhered from platelet-rich plasma (PRP) and flowing whole blood (FWB) on patterned surface. Furthermore, the different combination of surface topography and pre-adsorbed Fn could influence the adhesion of L929 cells. The flat surface with pre-adsorbed Fn was the optimum substrate while the virgin patterned surface was the poor substrate in terms of L929 cells spread.
Co-reporter:Feng Zhou;Lin Yuan;He Huang
Science Bulletin 2009 Volume 54( Issue 18) pp:3200-3205
Publication Date(Web):2009 September
DOI:10.1007/s11434-009-0366-1
The topography of material surface has important influence on cell behavior and physiological functions. Groove-like pattern has drawn much attention among various patterns, due to the phenomenon of “contact guidance“ induced by this kind of topography. This review mainly focuses on “contact guidance“ formation as well as its influence on cell behavior and physiological effects. The possible mechanisms of “contact guidance” formation were discussed. The research trend and the potential applications were also suggested.
Co-reporter:Hong Chen, Lin Yuan, Wei Song, Zhongkui Wu, Dan Li
Progress in Polymer Science 2008 Volume 33(Issue 11) pp:1059-1087
Publication Date(Web):November 2008
DOI:10.1016/j.progpolymsci.2008.07.006
Biocompatibility is one of the most important characteristics of a biomedical polymer material whose surface is required to interact with a biological system. Such interactions between polymer surfaces and organisms have been the focus of many studies. Since proteins are viewed as the primary and the most important player in mediating polymer–organism interactions, the status of the proteins on a material surface is believed to determine the ultimate biocompatibility of a given polymer. In order to achieve specific responses between polymer surfaces and the adjacent cells and to reduce non-specific interactions, the principles for designing biocompatible polymer materials are brought forth, such as passivating the polymer surfaces to minimize non-specific protein interaction, or decorating polymer surfaces with biomolecules to induce specific protein adsorption and cell responses. An ongoing goal is to produce a more effective biocompatible antifouling surface coupled with the use of specific ligands to induce anticipated protein and cell responses in vitro and in vivo.
Co-reporter:Hong Chen;Liang Wang;Yanxia Zhang;Dan Li;W. Glenn McClung;Michael A. Brook;Heather Sheardown;John L. Brash
Macromolecular Bioscience 2008 Volume 8( Issue 9) pp:863-870
Publication Date(Web):
DOI:10.1002/mabi.200800014
Co-reporter:Hong Chen, Xiaoyang Hu, Yanxia Zhang, Dan Li, Zhongkui Wu, Tao Zhang
Colloids and Surfaces B: Biointerfaces 2008 Volume 61(Issue 2) pp:237-243
Publication Date(Web):15 February 2008
DOI:10.1016/j.colsurfb.2007.08.012
Polyurethanes were modified using monobenzyloxy polyethylene glycol (BPEG) which possesses a bulky hydrophobic benzyloxy group at one end and a hydroxyl group at the other end as a preconstructed BPEG layer, and poly(ethylene glycol) (PEG) and monomethoxyl poly(ethylene glycol) (MPEG) with various chain lengths as fillers. Our objective was to investigate the effect of PEG graft density and conformation on protein adsorption at PEGlated surface. The graft density was estimated by a chemical titration method. The combination of ATR-FTIR, AFM and titration results provide evidences that the graft density can be increased by backfilling PEG or MPEG to a BPEG layer. However, fibrinogen and albumin adsorption significantly increased on all surfaces after PEG or MPEG backfilling. We conclude that the conformation of hydrophobic benzyloxy end groups of the BPEG layer plays a key role. The benzyloxy end groups of preconstructed PEG chains stretch to the surface after PEG backfilling, which possibly accounts for the observed increase in protein adsorption. The BPEG conformation change after backfilling with PEG or MPEG was also suggested by contact angles. Additionally, protein adsorption was slightly influenced by the length of filler, suggesting a change in surface morphology.
Co-reporter:Wei Song
Science Bulletin 2007 Volume 52( Issue 23) pp:3169-3173
Publication Date(Web):2007 December
DOI:10.1007/s11434-007-0504-6
Protein adsorption behavior on the surfaces of biomedical materials is highly related to the biocompatibility of the materials. In the past, numerous research reports were mainly focused on the effect of chemical components of a material’s surface on protein adsorption. The effect of surface topography on protein adsorption, the topic of this review, has recently received keen interest. The influence of surface nano-topographic factors, including roughness, curvature and geometry, on protein adsorption as well as the protein adsorption behavior, such as the amount of protein adsorbed, the activity and morphology of adsorbed protein, is introduced.
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