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Formation of Hydrophobic Domains on the poly(MPC-co-Dodecyl Methacrylate)-Coated Surface Recognized by Macrophage-like Cells Risa Katayama,† Musashi Ikeda,† Kohei Shiraishi,‡ Akikazu Matsumoto,*,† and Chie Kojima*,† †
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan ‡ Graduate School of Systems Engineering, Kindai University, 1 Takaya-umenobe, Higashi-hiroshima, Hiroshima 739-2116, Japan
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S Supporting Information *
ABSTRACT: Copolymers comprising 2-methacryloyloxyethyl phosphorylcholine (MPC) and hydrophobic methacrylic esters were used as biomembrane-mimetic polymers to provide blood compatibility. In the present study, we compared the surfaces coated with two MPC polymers with different alkyl groups, namely, poly(MPC-co-butyl methacrylate) (PMB) and poly(MPC-co-dodecyl methacrylate) (PMD), to clarify the effect of their hydrophobic units. Various substrates, such as poly(ethylene terephthalate), polycarbonate, polypropylene, acrylonitrile-butadiene-styrene copolymer, and stainless steel, were coated with ethanol solutions containing various concentrations of PMD or PMB. The solubility of PMD in ethanol changed depending on the water content. Scanning probe microscopy and rhodamine 6G staining revealed heterogeneous microstructures on the PMD-coated surface but not on the PMB-coated surface. Adhesion of various cells was efficiently suppressed by the PMD coating at lower concentration than the PMB coating, except regarding the adhesion of macrophage-like RAW264.7 cells. Our results suggest that the dodecyl groups in PMD increased its affinity for the substrates and simultaneously induced the formation of hydrophobic domains recognized by RAW264.7 cells.
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INTRODUCTION Researchers have developed biocompatible synthetic polymers for various biomedical applications such as drug delivery systems, regenerative medicine, and medical devices.1−4 Biomolecule adhesion can be prevented by coating with zwitterionic polymers such as sulfobetaine- and carboxybetaine-based materials. Therefore, such polymers have attracted attention in recent years.5−10 Polymers comprising 2methacryloyloxyethyl phosphorylcholine (MPC), which are zwitterionic, have been developed by Ishihara et al.11 MPC polymers have a phosphorylcholine group in a side chain, which mimics the phosphatidylcholine in cell membranes.11−14 MPC polymer coatings on artificial materials can provide biologically inert surfaces that mimic vascular endothelium cells.11 It is thought that protein adsorption and cell adhesion are suppressed, because a hydration layer is formed on the MPC polymer-coated surface owing to the presence of the phosphorylcholine group.11−26 Because MPC homopolymers are highly soluble in water, copolymers of MPC with a hydrophobic comonomer are used as coatings.11−13,18−26 Previously, various methacrylate esters including butyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, dodecyl methacrylate, and stearyl methacrylate were copolymerized with MPC, and their cell adhesion properties were investigated.22 The results indicated that a coating comprising poly(MPC-co-butyl methacrylate) (PMB) suppressed platelet © XXXX American Chemical Society
adhesion and that the suppression effects of other MPC polymers depended on the type of substrate.22 Many researchers have investigated the biocompatibility of PMB, which is one of the most widely used MPC polymers, to assess its potential for the surface modification of various materials including polymers, metals, and ceramics.11−13,19−21 There are several reports about a decrease in the adsorption of plasma proteins and platelets onto coatings comprising poly(MPC-cododecyl methacrylate) (PMD),22−26 which is much less than in reports on PMB. Here, we focused on the effects of hydrophobic esters in MPC polymers (Figure 1). And, we prepared PMB- and PMDcoated substrates using poly(ethylene terephthalate) (PET), polycarbonate (PC), polypropylene (PP), acrylonitrile-butadiene-styrene copolymer (ABS), and stainless steel (SUS), because these materials are used as the components of heart− lung machines. The surfaces of substrates coated with these MPC polymers were analyzed using energy-dispersive X-ray fluorescence spectrometry (ED-XRF), X-ray photoelectron Special Issue: Zwitterionic Interfaces: Concepts and Emerging Applications Received: January 17, 2019 Revised: February 24, 2019 Published: February 28, 2019 A
DOI: 10.1021/acs.langmuir.9b00178 Langmuir XXXX, XXX, XXX−XXX
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cultured on the SUS and ABS substrates were stained using 50 μL of a PBS solution containing 0.4% calcein acetoxymethyl ester (calceinAM). After incubation for 20 min, the green-fluorescent cells were counted using the fluorescence microscope. Cell adhesion (%) was defined as follows: cell adhesion (%) =
Two areas per substrate were examined, and three substrates were used for each experiment. The average value for cell adhesion (%) was obtained from the mean of the six results. PMD-coated PET substrates stained with rhodamine 6G were fixed on 35 mm dishes, then RAW264.7 cells ((1.5−7.5) × 105 cells) were seeded onto the dish. After incubation at 37 °C for 24 h, the RAW264.7 cells were stained with calcein-AM, as described above. Then, the adhered green fluorescent cells and the visible hydrophobic domains on the substrates were counted using a fluorescence microscope.
Figure 1. Chemical structures of PMB and PMD.
spectroscopy (XPS), and scanning probe microscopy (SPM). We observed heterogeneous microstructure by SPM and visualized the aggregation of the hydrophobic side chains of the MPC polymers by staining the phosphorylcholine groups with rhodamine 6G.27 We also examined the adhesion of various kinds of cells to different substrates coated with PMD or PMB, to investigate the influence of the hydrophobic groups on cell adhesion. The adhesion of platelets and components included in whole blood to MPC polymer-coated substrates has been studied previously.11−13,19,22−25 However, to the best of our knowledge, there have been no comparisons of the individual adhesion properties of various types of adhesive cells. Therefore, in the present study, we investigated the following cultured cells: HeLa cells (human cervical cancer cells), SH-SY5Y cells (human neuroblastoma cells), MC3T3E1 cells (murine osteoblasts), MDCK cells (Madin−Darby canine kidney epithelial cells), and RAW264.7 cells (murine macrophage-like cells). Our results suggest that the dodecyl groups in PMD greatly increased its affinity for the substrates and simultaneously induced the formation of hydrophobic domains, which were recognized by the macrophage-like RAW264.7 cells.
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cell number on the coated substrate × 100 cell number on the uncoated substrate
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RESULTS AND DISCUSSION Solubility of the MPC Polymers. In the present study, the substrates were dip-coated using MPC polymer solutions in ethanol and then air-dried. First, we examined the air-drying of ethanol. The solution content decreased to 50% in 20 min and to 1% in 40 min (Figure S1A). Proton nuclear magnetic resonance (1H NMR) analysis revealed that the solution was contaminated with a large amount of water (ca. 40 vol %) after 30 min (Figure S1B). Thus, the solubilities of PMB and PMD were examined in mixtures of ethanol and water. The transmittance of the PMB solutions was consistently high, which indicates that PMB was soluble in the solvents, irrespective of their composition. However, the transmittance of the PMD solutions decreased significantly at ethanol concentrations of 60−90 vol % (Figure 2). This indicates
EXPERIMENTAL SECTION
Dip-Coating with MPC Polymers. Sheets of PET, PC, PP, ABS (each 2 mm thick), and SUS (1.3 mm thick) were cut into ∼1 cm × 1.5 cm rectangles and washed with isopropyl alcohol for 5 min. The substrates were dip-coated with ethanol solutions (0.1−10 mg/mL) of PMD (ca. 33 mol % of MPC) or PMB (ca. 30 mol % of MPC) at a rate of 1 cm/s at room temperature. The coated substrates were airdried in an open glass Petri dish at room temperature for 24 h. Characterization. The solubility of the MPC polymers, the solution content during the air-drying, water contact angles of the MPC polymers-coated substrates were examined. ED-XRF, XPS, and SPM analyses and protein adsorption assays of the MPC polymerscoated substrates were also performed. Details of the procedures are provided in the Supporting Information. Staining with Rhodamine 6G. The MPC polymers were stained with rhodamine 6G using a method described in the literature.27 Briefly, the PET substrates coated with PMD or PMB (1 mg/mL) were immersed in an aqueous solution of rhodamine 6G (0.02%) for 30 s and then washed twice with pure water for 30 s. After they were dried in air at 25 °C for 24 h, images of the stained substrates were recorded using a fluorescence microscope (IX71, Olympus). An uncoated PET substrate was used as a control. After the PMD-coated substrates were immersed in pure water for 24 and 72 h, the same procedure described above was performed. Cell Adhesion. The MPC polymer-coated substrate and the uncoated substrate were fixed on a single 35 mm culture dish using a transparent adhesive sheet (CS 9621, Nitto Denko Corp.), and then 1.5 × 105 HeLa, SH-SY5Y, MC3T3-E1, MDCK, or RAW264.7 cells were seeded onto the culture dish. After incubation at 37 °C for 24 h, the substrates were washed for 1 min using phosphate-buffered saline (PBS) for the HeLa, MC3T3-E1, and SH-SY5Y cells, and PBS− ethylenediaminetetraacetic acid (EDTA) for the MDCK and RAW264.7 cells. The adhered cells to PET, PC, and PP were counted using an optical microscope (IX71, Olympus). The cells
Figure 2. Transmittance of the MPC polymer solutions in ethanol/ water mixtures.
that the solubility of PMD changes dramatically, depending on the ratio of water to ethanol. The aggregation of PMD in the ethanol/water mixtures possibly resulted from the hydrophobic interaction between the dodecyl groups, consistent with the previous report.25 We presume that the water contamination during the air-drying process may have induced the aggregation of the hydrophobic dodecyl groups, when the substrates were dip-coated with PMD. Surface Analyses of MPC Polymer-Coated Substrates. The various substrates were coated with ethanol solutions containing different concentrations of PMB or PMD , and the static water contact angles of the coated surfaces were measured (Figure 3). As the concentration of each MPC polymer solution increased, the water contact angle increased, until it reached a constant value. This indicates that the substrate surfaces are entirely coated with PMB or PMD at B
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regardless of the substrate. These contact angle values were consistent with the previous report,22 suggesting that PMB and PMD provided the coated surfaces with similar hydrophobicity on a macroscopic scale. The thickness of the MPC polymer layer on the various substrates was examined by ED-XRF analysis. The thicknesses of the PMD layers were similar to those of the PMB layers, which we estimated to be 70 nm (Table S1). The exceptions were the PMD- and PMB-coated ABS substrates (23 and 174 nm, respectively) and the PMBcoated PC substrate (127 nm). It was reported that the thickness of an MPC polymer applied by dip-coating was in the range of 30−100 nm,28 which was consistent with our result. This suggests that the MPC layer was thick enough to cover the surfaces of the substrates. We estimated the thickness of the MPC layer using the foundation parameter method on the premise that the layer was uniform. Because PC and ABS are not highly resistant to organic solvents, these substrates were possibly eroded by the MPC solutions, which prevented the precise determination of layer thickness. We also examined the surfaces of PMD- and PMB-coated PET using XPS and SPM. From the XPS spectra, similar phosphorus signals were detected in both substrates, suggesting that similar levels of phosphatidylcholine existed at the coating surfaces. However, a larger carbon signal was detected in the XPS spectrum of the PMD-coated surface than in the spectrum of the PMB-coated surface, because PMD has a higher carbon content than PMB owing to its long alkyl chain (Figure S2). SPM provided topological images and phase images of the surfaces of the PMD- and PMB-coated PET, as shown in Figure 4. Heterogeneous microstructures were observed in the phase images of the PMD-coated surface but not in the image of the PMB-coated surface. It is suggested
Figure 3. Water contact angles of substrates coated with various concentrations of PMD (A) or PMB (B) solutions (n = 5). The water contact angles of the uncoated substrates were 75.9° ± 3.2 for PET; 87.9° ± 1.6 for PC; 98.4° ± 1.5 for PP; 80.2° ± 2.8 for ABS; and 90.4° ± 3.2 for SUS.
high concentrations. The contact angles of PMD and PMB were almost the same (100−110°) at high concentrations,
Figure 4. SPM analysis of the PET substrate coated with PMD or PMB (1 mg/mL). (A) Topological and (B) phase images. Two different areas of the PMD-coated substrate were scanned. C
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Figure 5. Typical fluorescence images of MPC polymer-coated PET substrates stained with rhodamine 6G. (A) The uncoated substrate, (B) the PMB-coated substrate, and (C) the PMD-coated substrates. Scale bar = 100 μm.
that the bright areas and the dark areas correspond to the dodecyl units and the PC units, respectively. We also observed a unique domain with a low PC content that was 20 mm wide and 60 mm long on the PMD-coated substrate (the right panel in Figure 4), which is considered to be a hydrophobic domain. Rhodamine 6G can associate with the phosphorylcholine groups in MPC polymers, and specifically stain local areas that are occupied by the MPC unit on a substrate.27 Fluorescence signals were observed from the PMB- and PMD-coated PET substrates stained with rhodamine 6G, as shown in Figure 5. We observed black spots (10−30 μm in diameter) on the PMD-coated substrate but not on the PMB-coated substrate. The black spots were almost the same size as the hydrophobic domain revealed by SPM, suggesting that they correspond to the domains with low PC content in the PMD coating. This suggests that the dodecyl groups in PMD induced the formation of hydrophobic domains, but the butyl groups in PMB did not. Suppression of Cell Adhesion by Coating with MPC Polymers. Next, we examined the adhesion of various cells to the PMB- and PMD-coated substrates. Figures S3 and S4 show images of HeLa cells adhered to the substrates before and after coating with various concentrations of the PMB and PMD solutions. Coating with solutions containing high concentrations of the MPC polymers reduced the number of cells adhered to each of the substrates (Figures S3 and S4). Figure 6 shows cell adhesion (%) to the various substrates coated with different concentrations of PMB or PMD solutions. There were no obvious differences in the results for the plastic substrates (PC, PET, and PP). Cell adhesion to the PMDcoated substrates was suppressed at concentrations of 0.3 mg/ mL or higher. The concentration necessary to suppress cell adhesion with PMB-coated substrates increased to 0.5 mg/mL. This was because the PMD was effectively bound to the substrates owing to the hydrophobic interaction of the dodecyl groups. Cell adhesion to the MPC polymer-coated ABS and SUS substrates differed slightly from the results obtained for the plastic substrates. The difference might be from the different analytical methods for transparent substrates and nontransparent substrates in our cell adhesion assays. The cells adhered to the transparent substrates (PET, PC, and PP) were counted using an optical microscope, but those adhered to the nontransparent substrates (ABS and SUS) were counted using a fluorescence microscope after the staining with calcein-AM. We also performed the same experiments using various cultured cells (Figure 7 and Figures S5−S9). The adhesion of each type of cell was sufficiently suppressed by coating with high concentrations of PMB solutions. The PMD coating
Figure 6. HeLa cell adhesion (%) on the various substrates coated with different concentrations of PMD (A) and PMB (B) solutions (n = 6).
suppressed the adhesion of most types of cells except for macrophage-like RAW264.7 cells, the adhesion of which was not suppressed even at the highest concentration (10 mg/mL; Figure S5). Thus, the antifouling effect of the PMD coating was not versatile, although PMD suppressed the adhesion of some types of cells at lower concentrations than PMB. Recognition of Hydrophobic Domains by RAW 264.7 Cells. We attempted to elucidate why the RAW264.7 cells adhered to the PMD-coated substrates. RAW264.7 cells were seeded onto PMD-coated substrates that had been stained with rhodamine 6G to verify that they recognized the hydrophobic domains. Different numbers of RAW264.7 cells were seeded, and the relationship between the number of hydrophobic domains and the number of adherent cells was examined (Figure 8). The number of hydrophobic domains decreased as the number of seeded cells increased, indicating that the adhered RAW264.7 cells overlaid the hydrophobic domains. The number of adhered cells reached a plateau as the number of seeded cells continued to increase. This may have been because the hydrophobic domains were consumed by the scaffold of RAW264.7 cells. These results support our D
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protein in cell adhesion and was used as a model protein in the present study.12,24,26 We did not detect fibrinogen adsorption by the PMD-coated substrates (Figure S10), which agreed with the results of an earlier study.25 This suggests that the RAW264.7 cells adhered to the PMD-coated surface without the protein adsorption. A similar phenomenon has been reported regarding the adhesion of 3T3-L1 cells (mouse adipocyte-progenitor cells) to poly(2-methoxyethyl acrylate) analogue-coated substrates. In that case, the 3T3-L1 cells adhered to the substrates in an integrin-independent manner, and the intermediate water might have affected cell adhesion.29 RAW264.7 cells are macrophage-like cells that adhere strongly to substrates. It is necessary to apply a high concentration of trypsin and to incubate for an extended period to detach RAW264.7 cells from a culture dish. Macrophages express many kinds of adhesion molecules, including scavenger receptors, and recognize various endogenous and exogenous molecules.30,31 It has also been reported that some scavenger receptors bind to lipoprotein-containing fatty molecules.30−32 It is possible that these adhesive molecules affected the RAW264.7 cell adhesion to the PMD-coated surface. However, the details of the cell adhesion mechanisms remain unclear and warrant further investigation. Finally, we examined the hydrophobic domain after immersion in water. The area of the black spots decreased after 24 h, and they diminished after 72 h (Figure 9A), which suggests that the hydrophobic domains diminish during immersion in water because of the rearrangement of the PMD chains. We investigated the adhesion of the RAW264.7 cells to the wet surface. The number of adhered RAW264.7 cells decreased after immersion of the PMD-coated PET substrates in water (Figure 9B), indicating that water immersion induced the antifouling effect on PMD-coated substrates. These results also support our hypothesis that RAW264.7 cells recognize hydrophobic domains for the adhesion to the PMD-coated surface.
Figure 7. Adhesion (%) of various types of cells to PET coated with different concentrations of PMD (A) and PMB (B) solutions (n = 6).
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Figure 8. Number of adhered cells and observed hydrophobic domains on the PMD-coated substrates when various numbers of cells were seeded.
CONCLUSIONS In the present study, we compared PMB- and PMD-coated substrates by conducting surface analyses and cell adhesion assays to evaluate the effects of their hydrophobic groups. The PMD coating suppressed cell adhesion at lower concentration than PMB, suggesting that PMD interacted with substrates more efficiently than PMB. The PMD solution contained some insoluble fractions in the presence of water. SPM analysis revealed heterogeneous microstructures, and the rhodamine
hypothesis that RAW264.7 cells recognize the hydrophobic domains on PMD-coated substrates. It is believed that cell adhesion occurs after protein adsorption. It was reported that PMB coatings suppressed both protein adsorption and cell adhesion. We examined protein adsorption by the PMD-coated substrates using a quartz crystal microbalance (QCM). Fibrinogen is a key
Figure 9. PMD-coated PET substrates at 10 mg/mL after immersion in water for 24 and 72 h. (A) Rhodamine 6G staining. Scale bar = 100 μm. (B) Adhesion of RAW264.7 cells. E
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(5) Chen, S.; Li, L.; Zhao, C.; Zheng, J. Surface hydration: Principles and application toward low-fouling/nonfouling biomaterials. Polymer 2010, 51, 5283−5293. (6) Hadjesfandiari, N.; Yu, K.; Mei, Y.; Kizhakkedathu, J. N. Polymer brush-based approaches for the development of infection-resistant surfaces. J. Mater. Chem. B 2014, 2, 4968−4978. (7) Schlenoff, J. B. Zwitterion: Coating surfaces with zwitterionic functionality to reduce nonspecific adsorption. Langmuir 2014, 30, 9625−9636. (8) Chen, H.; Yuan, L.; Song, W.; Wu, Z.; Li, D. Biocompatible polymer materials: Role of protein-surface interactions. Prog. Polym. Sci. 2008, 33, 1059−1087. (9) Kwon, H. J.; Lee, Y.; Phuong, L. T.; Seon, G. M.; Kim, E.; Park, J. C.; Yoon, H.; Park, K. D. Zwitterionic sulfobetaine polymerimmobilized surface by simple tyrosinase-mediated grafting for enhanced antifouling property. Acta Biomater. 2017, 61, 169−179. (10) Meng, H.; Cheng, Q.; Li, C. Polyacrylonitrile-based zwitterionic ultrafiltration membrane with improved anti-proteinfouling capacity. Appl. Surf. Sci. 2014, 303, 399−405. (11) Ishihara, K.; Ueda, T.; Nakabayashi, N. Preparation of phospholipid polymers and their properties as polymer hydrogel membranes. Polym. J. 1990, 22, 355−360. (12) Iwasaki, Y.; Ishihara, K. Cell membrane-inspired phospholipid polymers for developing medical devices with excellent biointerfaces. Sci. Technol. Adv. Mater. 2012, 13, No. 064101. (13) Iwasaki, Y.; Ishihara, K. Phosphorylcholine-containing polymers for biomedical applications. Anal. Bioanal. Chem. 2005, 381, 534− 546. (14) Xu, Y.; Takai, M.; Ishihara, K. Phospholipid polymer biointerfaces for lab-on-a-chip devices. Ann. Biomed. Eng. 2010, 38, 1938−1953. (15) Goda, T.; Ishihara, K.; Miyahara, Y. Critical update on 2methacryloyloxyethyl phosphorylcholine (MPC) polymer science. J. Appl. Polym. Sci. 2015, 132, 41766. (16) Moro, T.; Takatori, Y.; Ishihara, K.; Konno, T.; Takigawa, Y.; Matsushita, T.; Chung, U. I. L.; Nakamura, K.; Kawaguchi, H. Surface grafting of artificial joints with a biocompatible polymer for preventing periprosthetic osteolysis. Nat. Mater. 2004, 3, 829−836. (17) Wang, B. L.; Jin, T. W.; Han, Y. M.; Shen, C. H.; Li, Q.; Lin, Q. K.; Chen, H. Bio-inspired terpolymers contacting dopamine, cations and MPC: a versatile platform to construct a recycle antibacterial and antifouling surface. J. Mater. Chem. B 2015, 3, 5501−5510. (18) Futamura, K.; Matsuno, R.; Konno, T.; Takai, M.; Ishihara, K. Rapid development of hydrophilicity and protein adsorption resistance by polymer surfaces bearing phosphorylcholine and naphthalene groups. Langmuir 2008, 24, 10340−10344. (19) Chen, S.-H.; Chang, Y.; Ishihara, K. Reduced blood cell adhesion on polypropylene substrates through a simple surface zwitterionization. Langmuir 2017, 33, 611−621. (20) Ho, S. P.; Nakabayashi, N.; Iwasaki, Y.; Boland, T.; LaBerge, M. Frictional properties of poly(MPC-co-BMA) phospholipid polymer for catheter applications. Biomaterials 2003, 24, 5121−5129. (21) Fujii, K.; Matsumoto, N. H.; Koyama, Y.; Iwasaki, Y.; Ishihara, K.; Takakuda, K. Prevention of biofilm formation with a coating of 2methacryloyloxyethyl phosphorylcholine polymer. J. Vet. Med. Sci. 2008, 70, 167−173. (22) Ueda, T.; Oshida, H.; Kurita, K.; Ishihara, K.; Nakabayashi, N. Preparation of 2-methacryloyloxyethyl phosphorylcholine copolymers with alkyl methacrylates and their blood compatibility. Polym. J. 1992, 24, 1259−1269. (23) Ishihara, K.; Iwasaki, Y. Reduced protein adsorption on novel phospholipid polymers. J. Biomater. Appl. 1998, 13, 111−127. (24) Ishihara, K.; Nomura, H.; Mihara, T.; Kurita, K.; Iwasaki, Y.; Nakabayashi, N. Why do phospholipid polymers reduce protein adsorption? J. Biomed. Mater. Res. 1998, 39, 323−330. (25) Lewis, A. L.; Hughes, P. D.; Kirkwood, L. C.; Leppard, S. W.; Redman, R. P.; Tolhurst, L. A.; Stratford, P. W. Synthesis and characterization of phosphorylcholine-based polymers useful for coating blood filtration devices. Biomaterials 2000, 21, 1847−1859.
6G staining visualized the formation of hydrophobic domains (∼30 μm) on the PMD-coated substrates, whereas uniform surfaces were observed on the PMB-coated substrates in these analyses. The hydrophobic domains on the PMD-coated surface were recognized by macrophage-like RAW264.7 cells but not after immersion in water. This is the first report showing heterogeneous microstructures, corresponding to hydrophobic domains, on the PMD-coated surface. Hydrophobic domains are possibly formed on the surface coated with other copolymers with hydrophilic and hydrophobic units, which may affect the surface properties. Our results also imply that macrophage-like RAW264.7 cells are useful for detecting hydrophobic domains on various polymer-coated surfaces.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.9b00178.
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Experimental procedures; thickness of MPC polymer coatings (Table S1); air-drying of ethanol (Figure S1); XPS spectra of PMD- and PMB-coated PET (Figure S2); typical images of cell adhesion on various surfaces coated with PMD and PMB (Figures S3 and S4); adhesion properties of various cells (Figures S5-S9); and protein adsorption on the PMD-coated substrate (Figure S10)(PDF)
AUTHOR INFORMATION
Corresponding Authors
*Phone: +81 72 254 8190. Fax: +81 72 254 8190. E-mail:
[email protected]. (C.K.) *Phone: +81 72 254 9292. Fax: +81 72 254 9292. E-mail:
[email protected]. (A.M.) ORCID
Chie Kojima: 0000-0002-2208-5784 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We are grateful to Prof. E. Higuchi (Osaka Prefecture Univ.), Mr. R. Yamato (Shimadzu Techno-Research Corp.), and Ms. S. Moriguchi (Shimadzu Techno-Research Corp.) for their assistance with the XPS, ED-XRF, and SPM analyses, respectively. We are also grateful to Dr. H. Tachi (Osaka Research Institute of Industrial Science and Technology) for his valuable input into our discussions on surface analyses. We thank F. Kitching, MSc., from Edanz Group (www. edanzediting.com/ac) for editing a draft of this manuscript.
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