Accepted Design of Protein Resistant Surfaces
Polymer Brushes Showing Non-Fouling in
Blood Plasma Challenge the Currently Accepted Design of Protein Resistant Surfaces a
Cesar Rodriguez-Emmenegger,* Eduard Brynda, Tomas Riedel, Milan Houska, Vladimir Sˇubr, Aldo Bologna Alles, Erol Hasan, Julien E. Gautrot, Wilhelm T. S. Huck
Introduction
Protein fouling in complex biological fluids, in particular, blood, plasma, and serum, is an adverse event that can impair the properties or functions of various biotechnolo-gical and biomedical devices.[1–3]Some examples include
stopping flow through separation columns and porous membranes,[4] non-specific response of affinity biosen-sors,[2,3,5]reduced circulation time of nanocarriers in the blood stream due to colloidal instability[6] or
opsoniza-Dr. C. Rodriguez-Emmenegger, opsoniza-Dr. E. Brynda, opsoniza-Dr. T. Riedel, opsoniza-Dr. M.
Houska, Dr. V. Sˇubr
Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Prague, 162 00, Czech Republic E-mail: rodriguez@imc.cas.cz
Dr. C. Rodriguez-Emmenegger, Dr. A. B. Alles
College of Engineering, Universidad de la Republica, Montevideo, 11300, Uruguay
aSupporting Informationfor this article is available from the Wiley Online Library or from the author.
Dr. T. Riedel
Institute of Hematology and Blood Transfusion, Prague, 12820, Czech Republic
Dr. E. Hasan
Department of Chemistry, University of Liverpool, L69 3BX, United Kingdom
Dr. J. E. Gautrot, Prof. W. T. S. Huck
Department of Chemistry, University of Cambridge, CB2 1EW, United Kingdom
Prof. W. T. S. Huck
Radboud University Nijmegen, Institute for Molecules and Materials, 6525 AJ Nijmegen, The Netherlands
Ultra-low-fouling poly[N-(2-hydroxypropyl) methacrylamide] (poly(HPMA)) brushes have been synthesized for the first time. Similar to the so far only ultra-low-fouling surface, poly(carboxybetaine acrylamide), the level of blood plasma fouling was below the detection limit of surface plasmon resonance (SPR, 0.03 ngcm2)
despite being a hydrogen bond donor and displaying a moderate wettability, thus challenging the currently accepted views for the design of antifouling properties.
The antifouling properties were preserved even after two years of storage. To demonstrate the potential of poly-(HPMA) brushes for the preparation of bioactive ultra-low fouling surfaces a label-free SPR immunosensor for detection of G Streptococcus was prepared.
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tion,[7–11] bacteria attachment on contact lenses[12] and synthetic grafts,[13]or disabling of cardiovascular devices by thrombus formation.[13,14]Ultra-low-fouling properties are particularly essential for biosensors designed to detect analytes in real-time in complex biological media, such as blood serum or plasma.[5]Contemporary surface modifica-tions with antifouling self-assembled monolayers (SAMs),[15] grafted polymer layers, and polymer brushes reduce considerably or suppress the adsorption from single protein solutions. Authors have often claimed that they have obtained perfectly antifouling,[16] super-low foul-ing,[17] ultra-low fouling,[18] and even non-fouling[19]
surfaces because they had not observed any adsorption from solutions of the main plasma proteins—human serum albumin (HSA) and fibrinogen (Fbg). However, a reduction or even total prevention of the adsorption of the main blood plasma proteins (HSA and Fbg) and immuno-globulin G (IgG) is not evidence that the surface is resistant to blood plasma.[3,6,20] Much fewer works showed a reduction in the fouling from blood plasma.[3,21] Grafted carboxymethyl dextrane or poly(ethylene glycol) have been used but only a minor decrease in plasma fouling was reached. Currently, the design of antifouling surfaces is based on general principles that were established from experiments conducted on SAMs and thin (functional) polymer films. Surface wettability, the presence of hydro-gen bond acceptors, the lack of hydrohydro-gen bond donors, and a neutral charge have been postulated to be essential properties for efficient resistance to protein adsorp-tion.[22–26] The water barrier theory[27,28] and the steric repulsion[29]derived from colloidal stability theory have also been used to interpret the surface resistance to proteins. Theoretical treatment also predicted enhanced antifouling properties with increasing grafting density and chain length of the polymers, i.e., the polymer chains in the brush regime.[30] The development of surface-initiated controlled radical polymerization allowed the coating of surfaces with well-defined, highly dense polymers brushes with tunable chain length.[31] Polymer brushes of poly(vinyl pyrrolidone),[32,33] poly(phosphorylcholine methacrylate),[3] poly(N-isopropyl acrylamide),[34] and poly(N-substituted acrylamide) containing different carbo-hydrates,[18,35] were shown to reduce the fouling from single protein solutions. Zwitterionic poly(sulfobetaine) brushes were studied because of their high wettability and neutral electric charge. Although these brushes totally suppressed the fouling from single protein solutions[17]
they were fouled in blood plasma.[3]More recent attempts include the use of polyampholyte brushes composed of positively and negatively charged monomers which resisted the fouling from single protein solution and reduced the fouling from diluted blood plasma.[36,37]An important reduction in plasma fouling has been achieved with brushes of poly(hydroxypropyl methacrylate)[38]
and particularly with brushes of poly(oligoethylene glycol methacrylate), which reduced the plasma fouling by 80–90%.[21,39,40]It should be stressed that to date only zwitterionic poly(carboxybetaine) brushes have provided surfaces on which plasma fouling has not been detectable even using surface plasmon resonance (SPR) with a detection limit of 0.03 ngcm2.[2,3]While the antifouling effect of poly(ethylene glycol) depends on the conforma-tional flexibility and hydration mediated by hydrogen bonding,[30,41]poly(betaines)’ superior resistance to fouling has been explained by a much stronger surface hydration due to ionic solvation of their zwitterionic groups.[42,43]
Herein the first synthesis of poly[N-(2-hydroxypropyl) methacrylamide] (poly(HPMA)) brushes grafted from gold surfaces by surface-initiated atom transfer radical poly-merization (SI-ATRP) is presented (Figure 1). The interaction of these brushes with single plasma protein solutions and blood plasma was compared with that of the best known antifouling brushes, i.e., poly(carboxybetaine acrylamide) (poly(CBAA)), poly(oligo(ethylene glycol) methyl ether methacrylate) (poly(MeOEGMA)), and the newly synthe-sized poly(2-hydroxypropyl methacrylate) (poly(HPM)), as well as with the widely used antifouling SAMs of hexa(ethylene glycol) undecanethiol on gold (OEG6).
Remarkably, poly(HPMA) brushes do not follow the currently accepted requirements for protein resistant surfaces, as they have hydrogen bond donors and are considerably less wettable than poly(CBAA), nonetheless they show unprecedented low fouling from undiluted blood plasma. A label-free SPR immunosensor for the detection of GStreptococcuswas prepared by facile covalent immobilization of an antibody to poly(HPMA) brushes demonstrating that these brushes can be used for the preparation of biotechnological and biomedical devices without the interference of non-specific interactions.
Experimental Section
Materials
All chemicals and solvents were purchased from Sigma–Aldrich, Acros, or Serva at the highest available purity and were used as received. The monomers N-(2-hydroxypropyl) methacrylamide Figure 1.Ultra-low-fouling functionalizable poly(HPMA) brushes.
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(HPMA) and (3-acryloylaminopropyl)(2-carboxyethyl)dimethy-lammonium (carboxybetaine acrylamide, CBAA) were synthesized according to literature procedures (see the Supporting Information).[44,45]
Preparation of SAMs
Gold-coated substrates (SPR chips) were rinsed with ethanol and water, dried with nitrogen, and cleaned with UV–ozone cleaner (Jelight) for 15 min. The substrates were immediately immersed in a 1103M solution of HS(CH2)11EG6(EG¼ethyleneglycol) or HS(CH2)11EG2in ethanol at 408C for 10 min and then kept in the dark at room temperature for 1 d. The preparation of the initiator SAM was analogous but the chips were placed in a 1103M
solution of v-mercaptoundecyl bromoisobutyrate at room temperature.
Polymerization of HPMA and CBAA
Ethanol (10 mL) was degassed using three freeze–pump–thaw cycles and transferred to a Schlenk tube containing CuBr (19.1 mg, 133mmol), CuBr2 (5.9 mg, 26.5mmol), and Me4Cyclam (40.9 mg, 160mmol). The blue solution of the catalyst was added to the monomer HPMA (953 mg, 6.7mmol) or CBAA (1 500 mg, 6.7 mmol).
Finally, the polymerization solution was transferred to the reactor containing the substrate coated with a SAM ofv-mercaptoundecyl bromoisobutyrate and the reaction was allowed to proceed for 2 h at 308C. The substrates coated with poly(HPMA) or poly(CBAA) brushes were washed with ethanol and water and stored in phosphate buffered saline (PBS).
Polymerization of Monomethoxy-Terminated Oligo(ethylene glycol)methacrylate (MeOEGMA)
To a degassed solution of CuBr2(8.1 mg, 36.4mmol), 2,20-dipyridyl (145 mg, 930mmol), and MeOEGMA (5.7 g, 19 mmol) in 10 mL of water, CuCl (37 mg, 375mmol) was added. The polymerization mixture was transferred under Ar protection to the reactor containing the initiator-coated substrate. The reaction was stopped after 30 min to yield 30 nm thick polymer brushes.
Polymerization of 2-Hydroxypropyl Methacrylate (HPM)
The novel poly(HPM) brushes were synthesized for the first time using a modified procedure described elsewhere.[46]To a degassed solution of CuBr2 (8.1 mg, 36.4mmol), 2,20-dipyridyl (145 mg, 930mmol), and HPM (6.4 g, 44.3 mmol) in 10 mL of water/ethanol (1 : 1), CuCl (37 mg, 375mmol) was added. The polymerization mixture was transferred under Ar to the reactor containing the initiator-coated substrate and the polymerization was allowed to proceed for 90 min at 308C to obtain 30 nm thick poly(HPM) brushes.
Biofunctionalization of Poly(HPMA) Brushes
Hydroxy groups in poly(HPMA) brushes with the same thickness as those used for fouling studies (19 nm) were activated by incubating them overnight in a solution ofN,N0-disuccinimidyl carbonate (DSC, 0.1M) and 4-dimethylaminopyridine (DMAP, 0.1M) in
anhydrousN,N-dimethylformamide (DMF) at room temperature for 24 h. The activation was carried out under inert atmosphere. The success of the activation was confirmed by FT-IR spectroscopy.
Freshly activated chips were rinsed with DMF and water. Antibody was immobilized by spreading a 150mL drop of a 50mgmL1 solution of rabbit antibody against peptidoglycan-polysaccharide antigen unique to group GStreptococcusin PBS, pH 7.4. The samples were placed in a glass chamber saturated with humidity for 12 h at 48C. The samples were rinsed with PBS and kept in PBS for 24 h before use. The binding of the peptidoglycan-polysaccharide antigen at concentrations of 600 and 6 000 ngmL1in PBS and the subsequent binding of secondary mouse antibody against the captured antigen was monitored in-real time using a Biacore 300 SPR apparatus.
Characterization
The thickness of the polymer brushes was determined by spectro-scopic ellipsometry using a Variable Angle Spectrospectro-scopic Imaging Auto-Nulling Ellipsometer EP3-SE in air at room temperature. The chemical composition of the brushes was studied by FT-IR grazing angle specular reflectance (GASR) at a grazing angle of 808and p-polarization. The wettability of the surfaces, assessed as the water contact angle, was examined by the dynamic sessile water drop method (Table 1, Supporting Information). Protein fouling was quantified by SPR spectroscopy using a custom built instrument described elsewhere.[45]For more details of the characterization techniques refer to the Supporting Information.
Results and Discussion
Poly(HPMA), poly(CBAA), poly(MeOEGMA), and poly(HPM) brushes were grown from gold surfaces modified with a SAM ofv-mercaptoundecyl bromoisobutyrate by SI-ATRP.
The chemical structure of the brushes was verified by FT-IR GASR (Figure 1, Supporting Information).
A dry thickness of 30 nm was selected as a minimum to reach optimal antifouling properties for poly(MeOEGMA) brushes. For poly(CBAA) and poly(HPM), a thickness of 18 and 30 nm, respectively, was selected following literature reports.[38,47] The adsorption from solutions of the main plasma proteins Fbg (1 mgmL1), HSA (5 mgmL1), IgG (8 mgmL1), and lysozyme (Lys, 1 mgmL1) in PBS as well as from undiluted human blood plasma was measured by SPR spectroscopy (Figure 2 and Supporting Information). All the brushes were able to suppress adsorption from the single protein solutions, but only poly(CBAA) and poly(HPMA) were able to fully suppress the fouling from blood plasma below the SPR detection limit of 0.03 ngcm2as depicted in Figure 2 and in Table 2 of the Supporting Information.
The observed plasma deposits, 22.5 ngcm2 on poly(-MeOEGMA), 40.5 ngcm2on poly(HPM), and 71 ngcm2 on OEG6 would be too high for many applications, particularly for label-free biosensing. The results were
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qualitatively confirmed by FT-IR GASR, by which no plasma deposits were detected on poly(CBAA) and poly(HPMA) (Supporting Information) after 15 min incubation. It is worth noting that for biosensing applications, resistance to a 15 min contact with blood plasma is a sufficient proof of fouling resistance, however, other applications require longer contact times with blood plasma. Therefore, the resistance to longer incubation in undiluted blood plasma was evaluated. No fouling was detected even after 2 h contact with undiluted human blood plasma.
Importantly, while the resistance of poly(CBAA) to protein adsorption corresponds well with the accepted ideas for the design of surfaces resistant to blood plasma fouling, i.e., high wettability expressed by low advancing and receding water contact angles,uadv¼238andurec¼88, and to the lack of hydrogen bond donors, poly(HPMA) brushes are out of line with these criteria. Remarkably, the novel brushes based on poly(HPMA) totally suppressed plasma fouling despite being hydrogen bond donors and displaying a moderate wettability, measured by water contact angles,uadv¼408andurec¼218, which were closer to those of poly(MeOEGMA) (uadv¼558 and urec¼228) or poly(HPM) (uadv¼508andurec¼368). The hydration of the poly(HPMA) brushes in water, characterized by a swelling of 176% of their dry thickness, was even lower than that of poly(MeOEGMA) brushes (216%). The excellent non-fouling properties of poly(HPMA) brushes together with our previous results showing no direct relationships between the plasma fouling on various surfaces and their wettability or ability to suppress adsorption of the main plasma proteins,[3] suggest that the principles of blood plasma fouling remain not well understood.
After incubation in blood plasma, SPR chips coated with poly(HPMA) brushes were stored in PBS. No fouling on the
chips was detected when the used chips were stored in PBS buffer and re-incubated in blood plasma after three months.
A plasma deposit of only 17 ngcm2was observed when these chips were incubated for a third time after two years storage in PBS. The stability of the poly(HPMA) antifouling properties easily out-performs that of the so far only ultra-low-fouling material, poly(CBAA) brushes, on which 125 ngcm2deposit was observed when repeating the incubation in plasma after two years of storage in PBS (Supporting Information).
Most of the real applications of non-fouling surfaces require covalent attachment of bioactive molecules, e.g., antibodies, antigens, aptamers, and cell interacting molecules,[5,20] to perform specific functions without the interference of fouling from the surrounding biological medium.[14]To demonstrate the potential of poly(HPMA) brushes for these applications a label-free SPR immuno-sensor for detection of G Streptococcus was prepared. A Figure 2.Fouling on SAMs of OEG6, poly(MeOEGMA), poly(HPMA),
poly(CBAA), and poly(HPMA) brushes after 15 min contact with undiluted blood plasma (BP) or single protein solutions of human fibrinogen (Fbg) 1 mgmL1, immunoglobulin G (IgG) 8 mgmL1, human serum albumin (HSA) 5 mgmL1, and lysozyme (Lys) 1 mgmL1in PBS. The fouling from BP was also studied in re-used samples of poly(CBAA) and poly(HPMA) after two years storage in PBS. () fouling below the limit of the SPR detection of 0.03 ngcm2.
Figure 3.A) Functionalization of poly(HPMA) brushes. Antibody was covalently attached to 18 nm thick poly(HPMA) brushes. The binding of antigen from PBS, continuous line: 6mgmL1, dashed line: 600 ngmL1, to the immobilized antibody and the binding of secondary antibody to the captured antigen (second parts of the curves) was observed by SPR. B) The interaction of undiluted blood plasma with poly(HPMA) brushes functionalized by cova-lently attached antibody. These experiments were carried out in a SPR apparatus from Biacore.
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rabbit antibody against a peptidoglycan-polysaccharide antigen unique to group G Streptococcus (Ab) was covalently attached to poly(HPMA) brushes activated with DSC and DMAP using a procedure described elsewhere.[48,49]
Figure 3A shows the real-time binding of the peptidogly-can-polysaccharide antigen at concentrations of 600 and 6 000 ngmL1 in PBS and the subsequent binding of secondary mouse antibody against the captured antigen observed by SPR spectroscopy utilizing a Biacore 3000 apparatus. Concentrations as low as 600 ngmL1could be detected (Figure 3A) while no increase in blood plasma fouling was observed after the immobilization of the antibody (Figure 3B) demonstrating the versatility of these brushes for the preparation of ultra-low-fouling bioactive surfaces.
Conclusion
In conclusion, a new class of ultra-low-fouling polymer brushes based on the biocompatible poly[N-(2-hydroxy-propyl) methacrylamide] was prepared for the first time.
Together with poly(CBAA), these novel protein resistant brushes are the only surface modifications capable of preventing the fouling from blood plasma below the detection levels of label-free monitoring platforms based on SPR. Importantly, the new poly(HPMA) brushes are based on a hydrogen bond donor and are moderately hydrophilic, which is in contrast to the currently accepted views for the design of protein resistant surfaces. Thus, these brushes open a new paradigm for the field of non-fouling surfaces based on new materials. The covalent functionalization of poly(HPMA) brushes with antibodies demonstrated their potential application for the preparation of ultra-low-fouling surfaces with specific biological activities.
Acknowledgements: This research was supported by the Acad-emy of Sciences of the Czech Republic under Contract No KAN200670701, by the Grant Agency of the Academy of Sciences of the Czech Republic (No. IAAX 00500803), and by grant SVV-2011-263.
Received: March 25, 2011; Revised: April 14, 2011; Published online: June 3, 2011; DOI: 10.1002/marc.201100189
Keywords: biosensors; blood plasma; HPMA; polymer brushes;
surfaces
[1] A. Hucknall, S. Rangarajan, A. Chilkoti,Adv. Mater.2009,21, 2441.
[2] S. Jiang, Z. Cao,Adv. Mater.2010,22,920.
[3] C. Rodriguez Emmenegger, E. Brynda, T. Riedel, Z. Sedlakova, M. Houska, A. B. Alles,Langmuir2009,25,6328.
[4] D. Rana, T. Matsuura,Chem. Rev.2010,110,2448.
[5] J. Homola,Chem. Rev.2008,108,462.
[6] C. Rodriguez-Emmenegger, A. Ja¨ger, E. Ja¨ger, P. Stepanek, A. B.
Alles, S. S. Guterres, A. R. Pohlmann, E. Brynda,Colloids Surf. B 2011,83,376.
[7] A. Verma, F. Stellacci,Small2010,6,12.
[8] I. Lynch, T. Cedervall, M. Lundqvist, C. Cabaleiro-Lago, S. Linse, K. A. Dawson,Adv. Colloid Interface Sci.2007, 134-135,167.
[9] M. Lundqvist, J. Stigler, G. Elia, I. Lynch, T. Cedervall, K. A.
Dawson,Proc. Natl. Acad. Sci. USA2008,105,14265.
[10] I. Lynch, K. A. Dawson,Nano Today2008,3,40.
[11] K. Knop, R. Hoogenboom, D. Fischer, U. S. Schubert,Angew.
Chem., Int. Ed.2010,49,6288.
[12] H. Thissen, T. Gengenbach, R. du Toit, D. F. Sweeney, P. Kingshott, H. J. Griesser, L. Meagher,Biomaterials2010, 31,5510.
[13] B. D. Ratner,Biomaterials2007,28,5144.
[14] B. D. Ratner,J. Biomed. Mater. Res.1993,27,283.
[15] L. Y. Li, S. F. Chen, S. Y. Jiang,J. Biomater. Sci., Polym. Ed.2007, 18,1415.
[16] Y.-Y. Luk, M. Kato, M. Mrksich,Langmuir2000,16,9604.
[17] Z. Zhang, S. Chen, Y. Chang, S. Jiang,J. Phys. Chem. B2006,110, 10799.
[18] K. Yu, J. N. Kizhakkedathu,Biomacromolecules2010,11,3073.
[19] H. Ma, Ja. He, X. Liu, J. Gan, G. Jin, J. Zhou,ACS Appl. Mater.
Interfaces2010,2,3223.
[20] W. Yang, L. Zhang, S. Wang, A. D. White, S. Jiang,Biomaterials 2009,30,5617.
[21] C. Rodriguez-Emmenegger, O. Kylian, M. Houska, E. Brynda, A. Artemenko, J. Kousal, A. Bologna Alles, H. Biederman, Biomacromolecules2011,12,1058.
[22] G. B. Sigal, M. Mrksich, G. M. Whitesides,J. Am. Chem. Soc.
1998,120,3464.
[23] S. Herrwerth, W. Eck, S. Reinhardt, M. Grunze,J. Am. Chem.
Soc.2003,125,9359.
[24] A. R. Statz, R. J. Meagher, A. E. Barron, P. B. Messersmith,J. Am.
Chem. Soc.2005,127,7972.
[25] E. Ostuni, R. G. Chapman, R. E. Holmlin, S. Takayama, G. M.
Whitesides,Langmuir2001,17,5605.
[26] R. E. Holmlin, X. Chen, R. G. Chapman, S. Takayama, G. M.
Whitesides,Langmuir2001,17,2841.
[27] J. Zheng, L. Li, S. Chen, S. Jiang,Langmuir2004,20,8931.
[28] M. Zolk, F. Eisert, J. Pipper, S. Herrwerth, W. Eck, M. Buck, M. Grunze,Langmuir2000,16,5849.
[29] S. Sant, S. Poulin, P. Hildgen,J. Biomed. Mater. Res. A2008,87A, 885.
[30] L. Li, S. Chen, J. Zheng, B. D. Ratner, S. Jiang,J. Phys. Chem. B 2005,109,2934.
[31] Rl. Barbey, L. Lavanant, D. Paripovic, N. Schu¨wer, C. Sugnaux, S. Tugulu, H.-A. Klok,Chem. Rev.2009,109,5437.
[32] C. R. Kinnane, G. K. Such, G. Antequera-Garci´a, Y. Yan, S. J.
Dodds, L. M. Liz-Marzan, F. Caruso,Biomacromolecules2009, 10,2839.
[33] Z. Wu, H. Chen, X. Liu, Y. Zhang, D. Li, H. Huang,Langmuir 2009,25,2900.
[34] F. J. Xu, K. G. Neoh, E. T. Kang,Prog. Polym. Sci.2009,34,719.
[35] J. E. Raynor, T. A. Petrie, K. P. Fears, R. A. Latour, As. J. Garci´a, D. M. Collard,Biomacromolecules2009,10,748.
[36] G. Li, H. Xue, C. Gao, F. Zhang, S. Jiang,Macromolecules2009, 43,14.
[37] Y. Chang, S.-H. Shu, Y.-J. Shih, C.-W. Chu, R.-C. Ruaan, W.-Y.
Chen,Langmuir2009,26,3522.
[38] C. Zhao, L. Li, J. Zheng,Langmuir2010,26,17375.
956 Macromol. Rapid Commun.2011,32, 952–957
ß2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.MaterialsViews.com
[39] J. Ladd, Z. Zhang, S. Chen, J. C. Hower, S. Jiang, Biomacromo-lecules2008,9,1357.
[40] J. E. Gautrot, W. T. S. Huck, M. Welch, M. Ramstedt,ACS Appl.
Mater. Interfaces2009,2,193.
[41] S. I. Jeon, J. H. Lee, J. D. Andrade, P. G. De Gennes,J. Colloid Interface Sci.1991,142,149.
[42] J. C. Hower, M. T. Bernards, S. Chen, H.-K. Tsao, Y.-J. Sheng, S. Jiang,J. Phys. Chem. B2008,113,197.
[43] Q. Shao, Y. He, A. D. White, S. Jiang,J. Phys. Chem. B2010,114, 16625.
[44] K. Ulbrich, V. Subr, J. Strohalm, D. Plocova, M. Jelinkova, B. Rihova,J. Controlled Release2000,64,63.
[45] H. Vaisocherova´, W. Yang, Z. Zhang, Z. Cao, G. Cheng, M. Piliarik, Ji. Homola, S. Jiang,Anal. Chem.2008,80,7894.
[46] K. L. Robinson, M. A. Khan, M. V. de Paz Banez, X. S. Wang, S. P.
Armes,Macromolecules2001,34,3155.
[47] H. Vaisocherova, Z. Zhang, W. Yang, Z. Q. Cao, G. Cheng, A. D.
Taylor, M. Piliarik, J. Homola, S. Y. Jiang,Biosens. Bioelectron.
2009,24,1924.
[48] J. Trmcic-Cvitas, E. Hasan, M. Ramstedt, X. Li, M. A. Cooper, C. Abell, W. T. S. Huck, J. E. Gautrot,Biomacromolecules2009, 10,2885.
[49] S. Diamanti, S. Arifuzzaman, A. Elsen, J. Genzer, R. A. Vaia, Polymer2008,49,3770.
www.MaterialsViews.com
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