Simple Strategy to Functionalize Polymeric Substrates via Surface

Dec 21, 2012 - The functionalization of polymer surfaces via surface-initiated atom transfer radical polymerization (ATRP) is of crucial importance to...
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Simple Strategy to Functionalize Polymeric Substrates via Surface-Initiated ATRP for Biomedical Applications C. Y. Li, F. J. Xu, and W. T. Yang*

Langmuir 2013.29:1541-1550. Downloaded from pubs.acs.org by AUSTRALIAN NATL UNIV on 07/29/18. For personal use only.

State Key Laboratory of Chemical Resource Engineering, Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education College of Materials Science & Engineering, Beijing University of Chemical Technology, Beijing, China 100029 ABSTRACT: The functionalization of polymer surfaces via surfaceinitiated atom transfer radical polymerization (ATRP) is of crucial importance to prepare various functional materials. It is generally complicated to conduct ATRP on different organic material surfaces. In this work, a facile photoinduced one-step method was first developed for the covalent immobilization of ATRP initiators on the C−H groupcontaining substrates such as biaxially oriented polypropylene (BOPP). The C−H bonds of precise location of inert polymer surfaces were readily transferred to bromoalkyl initiator, followed by ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and glycidyl methacrylate (GMA), respectively, to produce the resultant patterned BOPP-gP(DMAEMA) and BOPP-g-P(GMA) films. The epoxy groups of the P(GMA) microdomains can be aminated for covalently coupling IgG, while the P(DMAEMA) microdomains were used for immobilizing IgG via electronic interactions. The resultant IgG-coupled microdomains could interact with the corresponding target proteins, anti-IgG.

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in the presence of acetone.34 The acetone excited by UV can abstract the hydrogens of C−H bonds of polymer substrates and O−H bond of phenol derivatives, and the resultant carboncentered radicals and oxygen-centered phenoxy radicals were coupled together. Inspired by this technique, we intended to develop a versatile strategy to covalently immobilize an ATRP initiator, one α-bromine-containing phenol derivative, onto the polymer surfaces with inert C−H bonds. In this work, the phenol derivative, bromo4-hydroxyacetophenone (BHAP) as the model ATRP initiator, is first directly immobilized on the polymer substrates under UV irritation (Scheme 1). The inert biaxially oriented polypropylene (BOPP) film, one of the common commercial polymers, was chosen as the model. Metal photomask was used to pattern the BHAP initiators for the subsequent surface-initiated ATRP. Then, 2-(dimethylamino)ethyl methacrylate (DMAEMA) and glycidyl methacrylate (GMA) are polymerized respectively on the BOPP films with fixed ATRP initiators to produce the corresponding functional BOPP-g-P(DMAEMA) and BOPP-g-P(GMA) films. The epoxy groups of the P(GMA) microdomains can be aminated for covalently coupling IgG, while the P(DMAEMA) microdomains were used for immobilizing IgG via electronic interactions. The resultant IgG-coupled microdomains could interact with the corresponding target proteins, anti-IgG. The present simple one-step UV-induced strategy of fixing ATRP initiators would be readily applicable to a wide range of polymer films containing aliphatic C−H groups, making controlled functionalization

INTRODUCTION Covalent tethering of functional brushes on polymer surface without any destruction of bulk properties is of crucial importance to impart new surface performance including responsive ability,1,2 nonfouling property,3−5 cell adhesive characteristic,6,7 antibacterial proerty, 8,9 and protein immobilization.10,11 Especially, topics of patterning artificial surfaces have attracted much attention to develop biosensors, microarrays, and bioreactors.12−15 The desirable modification methods include surface-initiated thermal polymerization,16 photopolymerization,17 and controlled/living radical polymerization (CRP).18−20 Surfaceinitiated CRP is most frequently used, because it could produce well-defined polymer brushes with specific compositions, architectures, and functionalities.21,22 Among the different SICRPs available, atom transfer radical polymerization (ATRP) is quite popular because of its high tolerance toward a wide range of monomers, high compatibilities, and relatively mild reaction conditions.23−25 For surface-initiated ATRP, the immobilization of the ATRP initiators on the surfaces is the key process.26−28 There are two common approaches for the attachment of ATRP initiators. One relatively universal but complicated approach involves the deposition of a monolayer on the primary layer surface.29,30 The other strategy is to couple the end-functionalized initiators using the functional groups of substrate surfaces.31−33 However, most polymer substrate surfaces consist primarily of inert C−H bonds and lack the functional groups such as hydroxyl or amino groups. In general, complicated synthetic procedures were needed to produce the required functional groups. Recently, we found that the C−H bonds of the polymer substrate surfaces could be coupled with phenol derivatives under UV irradiation © 2012 American Chemical Society

Received: July 17, 2012 Revised: December 3, 2012 Published: December 21, 2012 1541

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Scheme 1. Schematic Illustration of the ATRP Processes of GMA and DMAEMA on BAHP-Functionalized BOPP Films and Their Resultant Protein Immobilizationa

a

BHAP, 2-bromo-4-hydroxyacetophenone; BOPP, biaxially-oriented polypropylene; GMA, glycidyl methacrylate; DMAEMA, 2-(dimethylamino)ethyl methacrylate).

Figure 1. XPS C 1s core-level spectra of the (a) pristine BOPP, (c) BOPP-Br, and the Br 3d core-level spectra of the (b) pristine BOPP and (d) BOPP-Br surfaces. removal of the inhibitors in a ready-to-use disposable inhibitor-removal column (Sigma-Aldrich). FITC-IgG, Rhodamine-IgG, FITC-anti-IgG, and Rhodamine-anti-IgG were obtained from Beijing Biosynthesis Biotechnology Co. and used without purification. Immobilization of ATRP Initiators on BOPP Films by UV Irradiation. A “sandwich” structure was applied in the UV irradiation to immobilize the ATRP initiators on BOPP films. A thin layer of BHAP acetone solution (50 μL, 0.2 mmol/mL) was coated onto the BOPP film (diameter 6 cm) with a micro syringe. Then, a top BOPP film covered this solution and the drop of solution was spread to be a thin liquid layer under suitable pressure from a quartz plate (weight 55 g). The irradiation area was controlled by the metallic mask, which was placed onto the BOPP film surface. The “sandwich” was irradiated by UV light (high-pressure mercury lamp, 1000 W; UV intensity,

of their surfaces possible via ATRP for potential biomedical applications.

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EXPERIMENTAL SECTION

Materials. Biaxially oriented polypropylene (BOPP) with a thickness of about 30 μm was supplied by Beijing Plastic Factory No. 6. The film discs were extracted with acetone for 12 h and then dried in a vacuum oven at room temperature until a constant weight. 2-Bromo-4-hydroxyacetophenone (BHAP, 98%), 2,2-dipyridyl (bpy, 99%), copper(I) bromide (CuBr, ≥99%), copper(II) bromide (CuBr2, ≥98%), 2-(dimethylamino)ethyl methacrylate (DMAEMA), and glycidyl methacrylate (GMA) were obtained from Sigma-Aldrich Chemical Co. Milwaukee. GMA and DMAEMA were used after 1542

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9 mW/cm2 at wavelength 254 nm) at room temperature for a certain time. The UV intensity could be regulated by changing the distance between the sample and the lamp. After irradiation, the resultant BOPP-Br films were taken out. The films were washed with copious amounts of acetone and subjected to Soxhlet extraction with acetone for 8 h, followed by three additional washings with acetone to remove the residual BHAP and the possibly generated benzopinacol. Finally, the washed films were dried at room temperature until constant weight. All samples were stored in the dark area. Surface-Initiated ATRP on BOPP Films. CuBr2 (3.8 mg, 0.017 mmol) and bpy (66.7 mg, 0.427 mmol) were added to a Schlenk flask containing methanol/water mixture at room temperature. The mixture was degassed under vacuum and purged with argon. To the Schlenk flask, the DMAEMA or GMA monomer was introduced and their concentrations were varied from 25% to 50%. The resulting solution was deoxygenated for 30 min by passing a continuous stream of dry argon through the solution being stirred. CuBr (24.5 mg, 0.171 mmol) was added to the solution under a stream of argon and was deoxygenated by a continuous stream of dry argon for 5 min. The initiatorimmobolized BOPP films were introduced the Schlenk flask, and then, the Schlenk flask was degassed with dry argon. The time of polymerization was varied from 1 to 11 h at room temperature, and the resultant patterned BOPP-g-P(DMAEMA) or BOPP-g-P(GMA) films were taken out, and rinsed with water and methanol. The films were then dried in vacuum oven for subsequent characterization. Protein Immobilization. The FITC-IgG or IgG/PBS solution (pH 7.4) (or Rhodamine-IgG or IgG/PBS solution (pH 7.4)) at a concentration of 0.1 mg/mL was dropped on BOPP-g-P(GMA) (or BOPP-g-P(DMAEMA)) surface, and then they were incubated for 30 min at 37 °C. Thorough washing with a mixture solution of PBS solution (pH 7.4) and Tween 80 (100/0.1) was performed to remove the nonspecific adsorption. In order to check the activity of IgG immobilized on BOPP, anti-IgG solution was applied. BSA/PBS pH 7.4 solution was dropped on the IgG-coupled film surfaces, and then incubated for 30 min at 37 °C to block the background. After washing thoroughly, the blocked BOPP-g-P(GMA)/IgG and BOPP-g-P(DMAEMA)/IgG films were immersed into Rhodamine-anti-IgG/ PBS and FITC-anti-IgG/PBS pH 7.4 solution (0.1 mg/mL). Finally, thorough washing with a mixture solution of PBS solution (pH 7.4) and Tween 80 was performed. Characterization. X-ray photoelectron spectra (XPS) on the surfaces were obtained by using an ESCALAB 250 Thermo Electron Corporation with a Al KΘ X-ray source (1486.6 eV). The core-level signals were obtained at a photoelectron takeoff angle of 75° (with respect to the sample surface). The UV absorption measurements of the films were performed on a GBC Cintra 20 spectrophotometer (GBC Scientific Equip-ment, Australia). Fluorescent microscopic images were taken by a Nikon Eclipse E600W. Scanning electron microscopy (SEM) was performed with a Hitachi S-4700 instrument. Atomic force microscopy (AFM) in tapping mode was carried out on a NanoScope IIIa (Digital Instruments Co., Santa Barbara, CA) instrument. Static water contact angles of the films surface were measured at 25 °C and 50% relative humidity by the sessile drop method, using a 2 μL water droplet by the Digital Instruments Inc. of ZhongChen, Shanghai, China. Grafting yield (GY) is defined as GY = (Wb − Wa)/A, where Wa and Wb represent the weight of the dry films before and after grafting, respectively, and A is the film area (about 30 cm2). Data are presented as means ± standard deviation (n = 3).

Figure 2. UV−visible spectra of the blank BOPP, modified BOPP films from different reaction times, and the BOPP reacted with acetone without BHAP for 14 min under UV.

Figure 3. Fluorescent images of the patterned BOPP-Br film surfaces.

recombination reactions with surface radicals because of electronic and steric reasons. Consequently, the BHAP oxygencentered free radicals, denoted as ATRP initiator groups, could be introduced onto the BOPP film surfaces. The chemical composition of the BOPP-Br film surfaces was determined by X-ray photoelectron spectroscopy (XPS). Figure 1 shows the C 1s and Br 3d core-level spectra of the (a,b) pristine BOPP and (c,d) BOPP-Br surfaces. The C 1s core-level spectra can be curve-fitted into three peak components with binding energies (BEs) at about 284.6, 286.2, and 288.7 eV, attributable to the C−H, C−O (and C−Br), and CO species, respectively. A Br 3d signal at BE of about 70 eV, characteristic of covalently bonded bromine, has appeared in the BOPP-Br. The weak Br 3d signal for the BOPP-Br surfaces is consistent with the nature

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RESULTS AND DISCUSSION Immobilization of ATRP Initiators. As shown in Scheme 1, the one-step method was used to immobilize the BHAP ATRP initiators. Acetone becomes excited to the triplet state under UV irradiation. Then, the excited acetone abstracts a hydrogen atom either from the C−H group of the polymeric substrate or from the OH group of BHAP. Thus, surface carbon-centered free radicals and BHAP oxygen-centered free radicals are generated. The BHAP oxygen-centered free radicals preferentially undergo 1543

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of the single BHAP monolayer on the pristine BOPP-Br film surface. To further confirm the immobilization of BHAP, the qualitative analysis by UV spectroscopy was conducted as shown in Figure 2. The pristine BOPP film and the BOPP film irradiated only with acetone both displayed no absorption bands in the UV−visible region. However, the UV−visible spectra of the photocoupled samples (irradiation time: 6, 10, 14, 18 min) presented the absorption bands from 200 to 300 nm. The absorption bands were related to the immobilized BHAP groups. The absorption intensity increased with the irradiation time. During the immobilization of ATRP initiators by UV irradiation, it is facile to design and microfabricate the surface patterning on polymer substrates by the use of metal masking. In this work, two different patterned metal masks, one with circles of different distribution and sizes and another one with our university logo, BUCT, were applied. After the immobilization of initiators, BHAP of the BOPP-BHAP surfaces was excited by purple light, and their fluorescent images were shown in Figure 3a,b. The beautiful images show the two different BHAP patterns, indicating it is successful to immobilize the ATRP initiators. Surface-Initiated ATRP on BOPP Films. Surface-initiated ATRP of GMA or DMAEMA was performed from the BOPPBr membrane to produce the corresponding BOPP-g-P(GMA) or BOPP-g-P(DMAEMA) films. The presence of grafted P(DMAEMA) and P(GMA) chains on the BOPP film surfaces was confirmed by XPS analysis after the surfaces had been subjected to vigorous washing and extraction. Figure 4 shows the respective wide scan and C 1s core-level spectra of the (a,a′)

BOPP-g-P(GMA)1, (b,b′) BOPP-g-P(GMA)2, and (c,c′) BOPPg-P(GMA)3 surfaces. The relative intensities of the O 1s and C 1s peaks increased with the ATRP time from 1 to 5 h. The C 1s core-level spectrum of BOPP-g-P(GMA) can be curved-fitted with three peak components, with BEs at 284.6 eV for the C−H and C−C species, 286.2 eV for the C−O species, and 288.7 eV for the OC−O species, respectively. The OC−O intensities of the epoxy functional group at about 288.7 eV are both substantially increased, and the oxygen-to-carbon signal ratio (O/C) increases from 0.17 to 0.38 with the ATRP time. It is a little lower than the theoretical ratio of 0.43 calculated for pure PGMA. This indicates that C−C of BOPP is detected through the PGMA grafts. Figure 5 shows the respective wide scan and C 1s core-level spectra of the (a,a′) BOPP-gP(DMAEMA)1, (b,b′) BOPP-g-P(DMAEMA)2, and (c,c′) BOPP-g-P(DMAEMA)3 surfaces. The intensities of the N 1s and O 1s peaks increase with the ATRP time from 1 to 5 h. The intensities of the C−N species at 286.2 eV and OC−O at 288.7 eV species peak components of the BOPP-gP(DMAEMA) also substantially increase. The oxygen-to-carbon signal ratio (N/C) increases from 0.042 to 0.084 with the ATRP time. Similarly, the ratio also is lower than the theoretical ratio of 0.12 calculated for pure PDMAEMA. The above results indicate that the densely grafted P(GMA) and P(DMAEMA) brushes have successfully grafted on the film. The growth kinetics of P(GMA) and P(DMAEMA) from the BOPP-Br films via surface-initiated ATRP were investigated by graft yield (GY) and thickness of grafted polymer. The GY was obtained by the weighing method, and the thicknesses were measured by the sectional analysis of AFM. Then, the

Figure 4. XPS wide scan and C 1s core-level spectra of the (a,a′) BOPP-g-P(GMA)1, (b,b′) BOPP-g-P(GMA)2, and (c,c′) BOPP-g-P(GMA)3 surfaces. 1544

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Figure 5. XPS wide scan and C 1s core level spectra of the (a,a′) BOPP-g-P(DMAEMA)1, (b,b′) BOPP-g-P(DMAEMA)2, and (c,c′) BOPP-gP(DMAEMA)3 surfaces.

average height of grafted polymer microdomains was defined as the thickness of grafted polymer. An approximately linear increase in GY and thickness of the P(GMA) and P(DMAEMA) chains on the BOPP films with polymerization time is shown in Figure 6. The results suggest that the chain growth from the BOPP films was consistent with a living and well-defined process. The growth of the P(GMA) brushes polymerized is faster than P(DMAEMA). Control experiments on the pristine BOPP films revealed that there was no linear increase in graft yield when they were subjected to the “surface initiated” ATRP of GMA and DMAEMA under similar reaction conditions. These results were consistent with the above obtained result. The surface morphologies of the grafted films were studied by scanning electron microscopy (SEM). Because the crosssectional views of BOPP-g-P(GMA) and BOPP-g-P(DMAEMA) are quite similar, the cross images of BOPP-g-P(GMA) were only shown. Figure 7 shows the cross-sectional images of the (a) pristine BOPP film and BOPP-g-P(GMA) film surfaces with different polymeric time of (b) 1 h, (c) 3 h, and (d) 5 h. The thickness of the pristine BOPP film is just about 30 μm. After grafting, the new polymer layer appeared and the uniformly grafted P(GMA) polymers were well formed on the BOPP film surface. Additionally, it was clearly seen that the P(GMA) thicknesses were increased gradually with the increase of the polymerization time. The thickness of the film from ATRP time of 5 h was up to 40 μm from the starting 30 μm.

Figure 6. Dependence of graft yield and thickness of the BOPP-gP(GMA) and BOPP-g-P(DMAEMA) films on the surface-initiated ATRP time. 1545

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Figure 7. SEM images of the cross-sectional views of the (a) pristine BOPP film and BOPP-g-P(GMA) film surfaces with different polymerization times of (b) 1 h, (c) 3 h, and (d) 5 h.

Figure 8. SEM images of the top views of the (a) BOPP-g-P(GMA)1, (b) BOPP-g-P(GMA)3, (c) BOPP-g-P(DMAEMA)1, and (d) BOPP-gP(DMAEMA)3 film surfaces.

Figure 8 shows the SEM images for the top views of the (a) BOPP-g-P(GMA)1 (from ATRP time of 1 h), (b) BOPP-gP(GMA)2 (from ATRP time of 5 h), (c) BOPP-g-P(DMAEMA)1 (from ATRP time of 1 h), and (d) BOPP-g-PDMAEMA2 (from ATRP time of 5 h) film surfaces. The images show two different shapes and heights of pattern on the BOPP films. After the grafting with P(GMA) for 1 h, a lot of symmetrical but thin columns appeared on the film surface (Figure 8a). After ATRP time of 5 h, these thin columns grow and demonstrate the obvious and uniform alignment (Figure 8b). P(DMAEMA) pattern ranked in strip shape on BOPP film surface. Similarly, the contrast of pattern increased with the polymerization time, which is consistent with those of atomic force microscopy

(AFM) images (Figure 9). The average height of P(GMA)1 microdomains is about 490 nm, while the average height of P(GMA)2 is around 4.80 μm; and the average height of P(DMAEMA)1 microdomains is about 0.28 μm, as well as that of the P(DMAEMA)2 being about 1.88 μm. The above results confirmed that the dense functional brushes of P(GMA) and P(DMAEMA) have been successfully obtained from the ATRP time of 5 h. Immobilization of IgG. The epoxy groups of the P(GMA) microdomains can be aminated for covalently coupling IgG, while the P(DMAEMA) microdomains were also used for immobilizing IgG via the electronic interaction. The isoelectric point of IgG is about 4.7. When pH > 4.7, the net charge of IgG 1546

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Figure 9. AFM images for the top view of the BOPP-g-P(GMA) film surfaces with different polymeric times of (a) 1 and (b) 5 h, and of the BOPPg-P(DMAEMA) film surfaces with different polymerization times of (c) 1 and (d) 5 h.

For P(GMA) and P(DMAEMA) brushes, no clear fluorescent images observed under excitement by blue or green light (Figure 11a,d). The BOPP-g-P(GMA)/FITC-IgG surfaces were excited by blue light and the BOPP-g-P(DMAEMA)/ Rhodamine-IgG surfaces were excited by green light. Their corresponding fluorescent images were shown in Figure 11b,e, respectively. The corresponding uniform and strong green (or red) fluorescence is observed across their respective regions, indicating that considerable amounts of IgG have binded successfully to the corresponding microdomains. The pattern of the fluorescence intensity perfectly corresponds to the specific bimolecular-coupled microdomains. In order to avoid the fluoresce interference, the BOPP-gP(GMA)/IgG and BOPP-g-P(DMAEMA)/IgG films without fluorescein were used to clearly investigate the interaction between IgG and anti-IgG. After the interaction of fluorescenselabeled anti-IgG with IgG, the BOPP-g-P(GMA)/IgG/Rhodamineanti-IgG surface was excited by green light to become red (Figure 11c), while the BOPP-g-P(GMA)/FITC-IgG was excited by blue light to be green (Figure 11b).The BOPP-g-

is negative and the electrostatic interaction will occur between cationic species of P(DMAEMA) and carboxylate groups of IgG. After the immobilization of IgG, the C 1s core-level spectra of the BOPP-g-P(GMA)/IgG and BOPP-g-P(DMAEMA)/IgG surfaces were shown in Figure 10a,b, respectively. In comparison with those of the BOPP-g-P(GMA) surfaces (Figure 4a′,b′,c′), the C 1s core-level spectra of the BOPP-g-P(GMA)/IgG surfaces possessed two additional peaks at about 285.9 and 287.4 eV, attributable to the C−N and OC−N species, respectively, which were associated with the amino and peptide bonds in IgG. An additional peak at about 287.4 eV attributable to OC−N species also appeared in BOPP-g-P(DMAEMA)/IgG surfaces. After the interaction of anti-IgG with the IgG immobilized on films, the C−N and OC−N species of the BOPP-g-P(GMA)/ IgG/anti-IgG and BOPP-g-P(DMAEMA)/IgG/anti-IgG surfaces increased, and the [N]/[C] ratios also increased, respectively (Figure 10a′,b′). Their corresponding immobilized amounts of IgG (or anti-IgG) are about 22.5 (or 26.2) and 17.6 (or 16.8) μg/cm2, respectively (Table 1). In addition, their water contact angles were also summarized in Table 1. 1547

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Figure 10. XPS C 1s core level spectra of the (a) BOPP-g-P(DMAEMA)/IgG, (a′) BOPP-g-P(DMAEMA)/IgG/anti-IgG, (b) BOPP-g-P(GMA)/ IgG, and (b′) BOPP-g-P(GMA)/IgG/anti-IgG surfaces.

immobilized protein could interact specifically with its target protein. The developed procedure in this work can allow protein processing to be carried out entirely in the aqueous phase and at such temperatures compatible with living and biological systems. The ultraviolet radiation was used only prior to the bimolecular immobilization. The present approach could be readily used for biomedical applications including lab-on-chip devices, bio-MEMs, and biosensors.

Table 1. Reaction Time, Grafting Yield (GY), and Static Water Contact Angle of the Functionalized Film Surfaces sample Pristine BOPP BOPP-Bra BOPP-g-P(GMA)1b BOPP-g-P(GMA)2b BOPP-g-P(GMA)3b BOPP-g-P(GMA)3-IgGd BOPP-g-P(GMA)3-IgGanti-IgGe BOPP-g-P(DMAEMA)1c BOPP-g-P(DMAEMA)2c BOPP-g-P(DMAEMA)3c BOPP-g-P(DMAEMA)3IgGd BOPP-g-P(DMAEMA)3anti-IgGe

reaction time

GY (μg/cm2)

14 min 1h 3h 5h 30 min 30 min

48.7 259.6 412.8 22.5 26.2

(±9.1) (±22.5) (±31.3) (±0.5) (±0.5)

110 105 95 82 70 51 48

1h 3h 5h 30 min

26.7 72.5 188.6 17.6

(±8.2) (±17.1) (±32.8) (±0.5)

86 78 48 46

30 min

16.8 (±0.5)

water contact angle (±3°)

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CONCLUSIONS A simple one-step method for the immobilization of BHAP groups (as the active ATRP initiators) on the BOPP surfaces containing the inert C−H bonds was developed under UV irradiation. With the aid of a photomask, the patterned polymer brushes can be easily prepared on the polymer film surfaces. The resultant patterned BOPP-g-P(DMAEMA) and BOPP-gP(GMA) films were used for immobilizing active proteins. The epoxy groups of the P(GMA) microdomains were aminated for covalently coupling IgG, while the P(DMAEMA) microdomains were used for immobilizing IgG via electronic interactions. The resultant IgG-coupled microdomains could strongly interact with the corresponding target proteins, anti-IgG. The present one-step immobilization process should be readily applicable to a wide range of polymer film surfaces containing C−H groups. With the development of a simple approach to the covalent immobilization of ATRP initiators on polymer film surfaces and the inherent versatility of surface-initiated ATRP, the surface functionality of polymer films can be precisely tailored for potential biomedical applications.

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From the BOPP- Br film which was obtained by irradiation under UV after coating of BHAP solution between two BOPP films for 14 min. b From BOPP-g-P(GMA) surfaces. Reaction conditions: [GMA]: [CuBr]:[CuBr2]:[Bpy] = 100:1:0.1:2 in methanol/water (4/1, v/v) mixture at room temperature. cFrom BOPP-g-P(DMAEMA) surfaces. Reaction conditions: [DMAEMA]:[CuBr]:[CuBr 2 ]:[Bpy] = 100:1:0.1:2 in methanol/water (1/4, v/v) mixture at room temperature. dObtained by immersing the BOPP-g-P(GMA) and BOPP-gP(DMAEMA) surfaces in the IgG/PBS 7.4 solution. eObtained by immersing the BOPP-g-P(GMA)/IgG and BOPP-g-P(DMAEMA)/ IgG surfaces in the fluoresce labeled anti-IgG/PBS 7.4 solution. a

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P(DMAEMA)/IgG/FITC-anti-IgG surface was excited by blue light to become green (Figure 11f), while the BOPP-gP(DMAEMA)/Rhodamine-IgG was excited by green light to become red (Figure 11e). The above results suggest that the

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. 1548

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Figure 11. Fluorescent images of the (a) BOPP-g-P(GMA), (b) BOPP-g-P(GMA)/FITC-IgG, (c) BOPP-g-P(GMA)/IgG/Rhodamineanti-IgG, (d) BOPP-g-P(DMAEMA), (e) BOPP-g-P(DMAEMA)/Rhodamine-IgG, and (f) BOPP-g-P(DMAEMA)/IgG/FITC-anti-IgG surfaces.

Notes

(10) Kawakita, H.; Masunaga, H.; Nomura, K.; Uezu, K.; Akiba, I.; Tsuneda, S. Adsorption of bovine serum albumin to a polymer brush prepared by atom-transfer radical polymerization in a porous inorganic membrane. J. Porous Mater. 2007, 14, 387−391. (11) Kusumo, A.; Bombalski, L.; Lin, Q.; Matyjaszewski, K.; Schneider, J. W.; Tilton, R. D. High capacity, charge-selective protein uptake by polyelectrolyte brushes. Langmuir 2007, 23, 4448−4454. (12) Blawas, A. S.; Reichert, W. M. Protein patterning. Biomaterials 1998, 19, 595−609. (13) Fodor, S.; Read, J.; Pirrung, M.; Stryer, L.; Lu, A.; Solas, D. Light-directed, spatially addressable parallel chemical synthesis. Science 1991, 251, 767−773. (14) Plummer, S. T.; Wang, Q.; Bohn, P. W.; Stockton, R.; Schwartz, M. A. Electrochemically derived gradients of the extracellular matrix protein fibronectin on gold. Langmuir 2003, 19, 7528−7536. (15) Zhu, H.; Bilgin, M.; Bangham, R.; Hall, D.; Casamayor, A.; Bertone, P.; Lan, N.; Jansen, R.; Bidlingmaier, S.; Houfek, T.; Mitchell, T.; Miller, P.; Dean, R. A.; Gerstein, M.; Snyder, M. Global analysis of protein activities using proteome chips. Science 2001, 293, 2101−2105. (16) Huang, W.; Skanth; Baker, G. L.; Bruening, M. L. Surfaceinitiated thermal radical polymerization on gold. Langmuir 2001, 17, 1731−1736. (17) Susanto, H.; Ulbricht, M. Photografted Thin polymer hydrogel layers on PES ultrafiltration membranes:characterization, stability, and influence on separation performance. Langmuir 2007, 23, 7818−7830. (18) Ma, H.; Hyun, J.; Stiller, P.; Chilkoti, A. “Non-fouling” oligo(ethylene glycol)-functionalized polymer brushes synthesized by surface-initiated atom transfer radical polymerization. Adv. Mater. 2004, 16, 338−341. (19) Matyjaszewski, K.; Miller, P. J.; Shukla, N.; Immaraporn, B.; Gelman, A.; Luokala, B. B.; Siclovan, T. M.; Kickelbick, G.; Vallant, T.; Hoffmann, H.; Pakula, T. Polymers at interfaces:using atom transfer radical polymerization in the controlled growth of homopolymers and block copolymers from silicon surfaces in the absence of untethered sacrificial initiator. Macromolecules 1999, 32, 8716−8724. (20) Baum, M.; Brittain, W. J. Synthesis of polymer brushes on silicate substrates via reversible addition fragmentation chain transfer technique. Macromolecules 2002, 35, 610−615. (21) Szwarc, M. Living’ Polymers. Nature 1956, 178, 1168−1169.

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are grateful for the financial support from National High Technology Research and Development Program (863 Program 2009AA03Z325). Support was also given by EPSRC (EP/H04986X/1) and NSFC (No.51033001, 51221002).

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REFERENCES

(1) Wandera, D.; Wickramasinghe, S. R.; Husson, S. M. Stimuliresponsive membranes. J. Membr. Sci. 2010, 357, 6−35. (2) Chen, T.; Ferris, R.; Zhang, J.; Ducker, R.; Zauscher, S. Stimulusresponsive polymer brushes on surfaces: Transduction mechanisms and applications. Prog. Polym. Sci. 2010, 35, 94−112. (3) Tugulu, S.; Klok, H.-A. Surface Modification of Polydimethylsiloxane Substrates with Nonfouling Poly(Poly(ethylene glycol)methacrylate) Brushes. Macromol. Symp. 2009, 279, 103−109. (4) Xiao, D.; Zhang, H.; Wirth, M. Chemical Modification of the Surface of Poly(dimethylsiloxane) by Atom-Transfer Radical Polymerization of Acrylamide. Langmuir 2002, 18, 9971−9976. (5) Rana, D.; Matsuura, T. Surface Modifications for antifouling membranes. Chem. Rev. 2010, 110, 2448−2471. (6) Raynor, J. E.; Petrie, T. A.; García, A. J.; Collard, D. M. Controlling cell adhesion to titanium: functionalization of poly[oligo(ethylene glycol)methacrylate] brushes with cell-adhesive peptides. Adv. Mater. 2007, 19, 1724−1728. (7) Tugulu, S.; Silacci, P.; Stergiopulos, N.; Klok, H.-A. RGDfunctionalized polymer brushes as substrates for the integrin specific adhesion of human umbilical vein endothelial cells. Biomaterials 2007, 28, 2536−2546. (8) Lee, S. B.; Koepsel, R. R.; Morley, S. W.; Matyjaszewski, K.; Sun, Y.; Russell, A. J. Permanent, nonleaching antibacterial surfaces. 1. synthesis by atom transfer radical polymerization. Biomacromolecules 2004, 5, 877−882. (9) Murata, H.; Koepsel, R. R.; Matyjaszewski, K.; Russell, A. J. Permanent, non-leaching antibacterial surfaces-2: How high density cationic surfaces kill bacterial cells. Biomaterials 2007, 28, 4870−4879. 1549

dx.doi.org/10.1021/la302866n | Langmuir 2013, 29, 1541−1550

Langmuir

Article

(22) Szwarc, M.; Levy, M.; Milkovich, R. Polymerization initiated by electron transfer to monomer. J. Am. Chem. Soc. 1956, 78, 2656−2657. (23) Wang, J.-S.; Matyjaszewski, K. Controlled/″living″ radical polymerization. atom transfer radical polymerization in the presence of transition-metal complexes. J. Am. Chem. Soc. 1995, 117, 5614− 5615. (24) Percec, V.; Barboiu, B. ″Living″ radical polymerization of styrene initiated by arenesulfonyl chlorides and CuI(bpy)nCl. Macromolecules 1995, 28, 7970−7972. (25) Matyjaszewski, K.; Xia, J. Atom transfer radical polymerization. Chem. Rev. 2001, 101, 2921−2990. (26) Huang, X.; Wirth, M. Surface-Initiated Radical Polymerization on Porous Silica. J. Anal. Chem. 1997, 69, 4577−4580. (27) Xu, F. J.; Neoh, K. G.; Kang, E. T. Bioactive surfaces and biomaterials via atom transfer radical polymerization. Prog. Polym. Sci. 2009, 34, 719−761. (28) Barbey, R. l.; Lavanant, L.; Paripovic, D.; Schüwer, N.; Sugnaux, C.; Tugulu, S.; Klok, H.-A. Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications. Chem. Rev. 2009, 109, 5437−5527. (29) Yang, Q.; Tian, J.; Hu, M.-X.; Xu, Z.-K. Construction of a comblike glycosylated membrane surface by a combination of UV-induced graft polymerization and surface-initiated ATRP. Langmuir 2007, 23, 6684−6690. (30) Singh, N.; Husson, S. M.; Zdyrko, B.; Luzinov, I. Surface modification of microporous PVDF membranes by ATRP. J. Membr. Sci. 2005, 262, 81−90. (31) Xu, F. J.; Zhao, J. P.; Kang, E. T.; Neoh, K. G.; Li, J. Functionalization of nylon membranes via surface-initiated atomtransfer radical polymerization. Langmuir 2007, 23, 8585−8592. (32) Holmberg, S.; Holmlund, P.; Wilén, C.-E.; Kallio, T.; Sundholm, G.; Sundholm, F. Synthesis of proton-conducting membranes by the utilization of preirradiation grafting and atom transfer radical polymerization techniques. J. Polym. Sci., Part A: Polym. Chem. 2002, 40, 591−600. (33) Chen, Y.; Kim, H. Poly(vinylidene fluoride) grafted with 3trimethoxysilylpropyl methacrylate for silyl functional membranes. React. Funct. Polym. 2008, 68, 1499−1506. (34) Xu, J.; Ma, Y.; Xie, J.; Xu, F. J.; Yang, W. Functionalization of polymeric surfaces by simple photoactivation of C-H bonds. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 2755−2760.

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