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Contribution of power on cell adhesion using atmospheric dielectric barrier discharge (DBD) plasma system
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Current Applied Physics 9 (2009) 219–223 www.elsevier.com/locate/cap www.kps.or.kr
Contribution of power on cell adhesion using atmospheric dielectric barrier discharge (DBD) plasma system Hyun Uk Lee a, Ye Sul Jeong a, Kwang Nak Koh a, Se Young Jeong a, Hyun-Gyu Kim b, Jong Sung Bae b, Chae Ryong Cho a,* a
Department of Nano Fusion Technology, Pusan National University, 50 Cheonghak-ri, Samnangjin-eup, Miryang, Gyeongnam 627-706, Republic of Korea b Busan Center, Korea Basic Science Institute, Busan 609-735, Republic of Korea Received 6 November 2007; received in revised form 17 January 2008; accepted 22 January 2008 Available online 5 February 2008
Abstract This study examined the effect of the treatment power on the enhanced cell attachment and proliferation on poly e-caprolactone (PCL) films treated with atmospheric plasma using a dielectric barrier discharge method (AP-DBD). The peak intensities of the –CH, C@O, –OH and –COO vibration modes, and binding energies of carbon and oxygen of the AP-DBD treated-PCL film increased with increasing plasma treatment power. The surfaces of the AP-DBD treated-PCL films were also examined for their in vitro cell adhesion properties using human prostate epithelial cells. The results showed that the level of cell attachment and proliferation on the AP-DBD treated-PCL film was ten times better than that observed on the untreated-PCL films. Ó 2008 Elsevier B.V. All rights reserved. PACS: 87.80. y; 87.68.+z; 52.50.Dg; 52.40.Hf; 52.77. j Keywords: Dielectric barrier discharge; Surface modification; Atmospheric plasma; Poly e-caprolactone; Cell adhesion
1. Introduction Plasma treatments are widely used to modify the surface properties of materials in many applications such as improving the adhesion of coatings to metals and polymers, increasing the wettability and printability of polymers, and in the manufacture of semiconductor devices [1,2]. Plasma treatment also improves polymer fiber-matrix adhesion largely by introducing polar or excited groups or even a new polymer layer that can form strong covalent bonds between the fiber and the matrix [3]. The major advantages of plasma treatment over other techniques include modification of the top atomic layers of a substrate, selection of a desired functional group, minimization of thermal degradation and rapid treatment time [4,5]. However, most plasma treatment processes involve a vacuum *
Corresponding author. Tel.: +82 55 350 5297; fax: +82 55 353 1314. E-mail address: [email protected] (C.R. Cho).
1567-1739/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2008.01.014
system, which may not be a continuous process. Plasma treatment with the DBD system does not require a vacuum system and can be operated at atmospheric pressure. The use of atmospheric plasma treatment can easily overcome the limitations imposed by the currently available vacuum-based plasma sterilizers [6,7]. Plasma treatments have many applications, including surface sterilization and/or decontamination in biomedical and food areas, as well as in biological warfare defense to kill anthrax or other biological warfare agents [8–11]. Poly e-caprolactone (PCL) is a semi-crystalline linear hydrophobic polymer and one of the most flexible synthetic biodegradable polymers [12]. It is used as a surgical material in clinics and it has been reported to have biomedical applications in controlled drug delivery systems and implants for orthopedic surgery [13]. Because of its low glass-transition temperature ( 60 °C) and low melting point (60 °C), the PCL amorphous phase displays high molecular mobility at human body temperature [14,15].
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However, the use of PCL films as a biomaterial is limited by its hydrophobic nature, which leads to low adhesion to the film. Although PCL films mimic the extra-cellular matrix in living tissues, their poor hydrophilicity results in a low cell loading in the initial stage of cell culture as well as a reduced the ability of cell adhesion, migration, proliferation, and differentiation [16]. Therefore, it is essential to improve the hydrophilicity of PCL to overcome these difficulties. This paper reports the plasma treatment power effect of a PCL film for enhanced cell attachment and proliferation. The chemical bonding states and vibration modes of the functional groups of a PCL film surface modified by AP-DBD were also investigated. 2. Materials and methods AP-DBD surface treatment was carried out in air (25 °C and room humidity = 52%) using a dielectric barrier discharge system (DBD), as shown in Fig. 1. The AP-DBD treatment system consists of an electrode with a length of 150 mm, a grounding plate of 200 mm, dielectric materials and a moving stage. A high frequency, self-tuning power supply of 20 kHz with a peak voltage of 1–10 kV was applied to the electrode to generate the linear micro-streamer discharge between electrodes within a gap of 1.5 mm. Based on previous experience, the typical range of working conditions for processing PCL films includes the input power (adjustable from 100 to 750 W), which were chosen as the operating parameter range. The PCL films were prepared at different AP-DBD treatment powers of 250 W, 280 W and 350 W (frequency: 20 kHz, duty: 10 ls, speed: 1.2 cm/min). Any thermal effects or electrical damages on the plasma treated-PCL films used in this study are observed. The extent of the surface modification of the
Fig. 2. (a) Surface contact angles and (b) AFM surface images of the PCL films according to the AP-DBD treatment power. (Untreated, 250 W, 280 W, and 350 W).
PCL films by the AP-DBD treatment were evaluated by water contact angle (Dataphysics, OCA), atomic force microscopy (AFM, PSIA, XE-120), Fourier-transformation infrared spectroscopy (FTIR, JASCO, FTIR-6300) and X-ray photoelectron spectroscopy (XPS, VG Scientific, ESCALAB250). The surfaces of the AP-DBD treated-PCL films were also examined for their in vitro cell attachment and proliferation using human prostate epithelial cells (HPECs). Fig. 2 shows the wettability and surface morphology of the AP-DBD treated-PCL film at different treatment powers. 3. Results and discussion
Fig. 1. Schematic diagram of the atmospheric plasma using a dielectric barrier discharge (AP-DBD) treatment system.
Fig. 2a shows the contact angles on the PCL film surface after the AP-DBD treatment. The contact angle on the modified-PCL films decreased from 65.3° to 36.3° with increasing treatment power. The decrease in water contact angle was attributed to the surface functionalization reactions, which introduced some hydrophilic groups onto the surface of the PCL films. The surface hydrophilicity
H.U. Lee et al. / Current Applied Physics 9 (2009) 219–223
of the polymers directly influences the adhesion of the interface between the polymer and the over layer material [4–6]. Fig. 2b shows AFM images of the AP-DBD treated-PCL film surface, which was carried out by acquiring a height intensity using identical measurement conditions. The average surface roughness (Ra) of the modified-PCL films increased from 1.6 to 64.6 nm with increasing the treatment power. However, the specific-surface area of the AP-DBD treated-PCL film at 350 W was lower than those of films treated at 250 W and 280 W due to surface damage. Fig. 3 shows the FT-IR absorbance spectra of the APDBD treated-PCL film at different treatment powers. In addition, the intensity of the peaks corresponding to the –OH, –CH3, –CH2, C@O, C–O and –COO functional groups at 3700–3600 cm 1, 2980 cm 1, 2850 cm 1, 1724 cm 1, 1294 cm 1 and 1190–1220 cm 1, respectively, increased with increasing power, as shown in Fig. 3a–d. The spectral changes observed after the AP treatments may be due to surface oxidation of the PCL film to hydrophilic groups, such as oxygen and carbon, on the PCL film surfaces by the active species in the plasma, where oxygen and carbon could originate from the surrounding air and fragment the polymer chains on the surface of the PCL film, as shown in Fig. 3e. The surface chemical bonding states of the AP-DBD treated-PCL film was examined by XPS (Fig. 4). The APDBD treated-PCL film surface showed O1s and C1s components at binding energies of 532.5 eV and 285.1 eV [17], respectively. The peaks for C1s could be fitted to the experimental C1s photopeaks, depending on the chemical bonding states of oxygen atoms bonded to the carbon. The intensity of the deconvoluted peaks at –CH (284.6 eV)
221
Fig. 4. Line-shape analysis of the high-resolution C1s and O1s spectra of the PCL films according to the AP-DBD treatment power. The peaks deconvoluted from the carbon and oxygen spectra are displayed, respectively. (The surface chemical bonding states of the AP-DBD treated-PCL film was examined by X-ray photoelectron spectroscopy).
and C–O (286.6 eV) in the C1s spectra, and that of –OH (531.5 eV) and –COOH (533.2 eV) peaks in the O1s spectrum increased with increasing AP-DBD treatment power. With increasing treatment power, the –OH (531.5 eV) and –COOH (533.2 eV) peaks were also shifted to a higher binding energy due to the increase in the concentration of functional groups. The surface chemical bonding states of these spectra might increase the hydrophilicity of the AP treated-PCL films and consequently improve the cell adhesion properties. In order to investigate the level of cell proliferation, HPECs (ATCC, Manassas) were cultured in RPMI-1640 media (Invitrogen, Carlsbad), supplemented with 10% fetal bovine serum and 1% penicillin and streptomycin in a atmosphere 5% CO2 at 37 °C for 7 days. The HPECs were detached from each sample using trypsin-EDTA, and the cells were counted by a hematocytometer [18]. The results are shown in Fig. 5a. HPECs with a density of 1.5 105 cells/cm2 were seeded on six well plates and pro-
Fig. 3. (a)–(d) FT-IR absorbance spectra of the PCL films according to the AP-DBD treatment power and (e) reaction models of functional group after the plasma treatment. (Untreated, 250 W, 280 W, and 350 W).
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Fig. 5. (a) Cell proliferation of the HPECs on the PCL films according to the atmospheric plasma treatment power and culturing time. SEM images of HPECs grown for 7 days on (b) untreated and (c, d) AP-DBD treated with 280 W. (Fig. 4d is an enlarged SEM image of Fig. 4c).
liferated onto a single layer. The difference in the number of cells attached to the AP-DBD treated-PCL films at different treatment powers was found to be 5 104, 2.3 105, 5.6 105 and 4.7 105 cells/cm2 culturing the cells for 7 days. The level of cell attachment and proliferation on the AP-DBD treated-PCL film at 280 W was ten times that observed on the AP-DBD untreated-PCL film. However, the AP-DBD treated-PCL film at 280 W showed better cell attachment and proliferation than that at 350 W. This was attributed to an increase in the specific-surface area and hydrophilic groups of the AP-DBD treated-PCL film surface at 280 W, but the specific-surface area of AP-DBD treated-PCL film at 350 W might be decreased by the higher plasma power. Fig. 5b–d shows FE-SEM images of the HPECs grown for 7 days after seeding on an untreated and AP-DBD treated-PCL film at 280 W. These results suggest that the AP-DBD treated-PCL film produces a better cell distribution and growth than the untreated-PCL film. The proteins of the cell membrane, which contain hydrophilic amino acids, exist in the outer region due to the repulsion caused by the protein and hydrophobic component at the inner region. Therefore, among the requirements of the matrix for cell culturing, the hydrophilic property of the AP-DBD treated-PCL surface improves the level of cell attachment by increasing the affinity between the protein and AP-DBD treated-PCL surface. In this study, a higher level of HPEC attachment and proliferation on the AP-DBD treated-PCL film might be due to its improved hydrophilic properties through the plasma surface treatment. 4. Summary In summary, the surface rearrangement of PCL films by an AP-DBD treatment was attributed to surface oxidation, which produced hydrophilic groups, such as oxygen and carbon onto the PCL film surface. Therefore, the hydrophilic properties of the AP-DBD treated-PCL film might
be improved by increasing the treatment power, which would improve the adhesion properties. Therefore, the AP-DBD treated-PCL film according to the power provides a better cell distribution and growth than that of the untreated-PCL film. The enhanced cell attachment and biocompatibility of the PCL film by the AP treatment was also attributed to both the increase in specific-surface area and number of hydrophilic groups on the AP-DBD treated-PCL film surface. The AP-DBD treated-PCL film underlines the cytocompatibility of a PCL film as well as its potential utility as a suitable scaffold in tissue engineering and cell chip applications. Acknowledgement This work was supported by SMEs Technology Innovation Program. References [1] S. Marais, M. Metayer, F. Poncin-Epaillard, Journal of Fluorine Chemistry 199 (2001) 107. [2] S. Tajima, K. Komvopoulos, Applied Physics Letter 124102 (2006) 89. [3] J. Hopkins, J.P.S. Badyal, Langmuir 3666 (1996) 12. [4] G.H. Yang, E.T. Kang, K.G. Neoh, Journal of Polymer Science 3498 (2000) 38. [5] J. Hyun, Polymer 6473 (2001) 42. [6] C.T. Montie, K.K. Wintenberg, J.R. Roth, IEEE Transactions on Plasma Science 33 (2005) 2. [7] M. Laroussi, J.P. Richardson, F.C. Dobbs, Applied Physics Letter 4 (2002) 81. [8] M. Nagatsu, F. Terashita, H. Nonaka, Applied Physics Letter 211502 (2005) 86. [9] X.T. Deng, J.J. Shi, G. Shama, M.G. Kong, Applied Physics Letter 153901 (2005) 87. [10] Q.S. Yu, C. Huang, F.H. Hsieh, H. Huff, Y. Duan, Applied Physics Letter 13903 (2006) 88. [11] T. Sato, T. Miyahara, A. Doi, S. Ochiai, T. Urayama, T. Nakatani, Applied Physics Letter 73902 (2006) 89.
H.U. Lee et al. / Current Applied Physics 9 (2009) 219–223 [12] K.H. Lee, H.Y. Kim, M.S. Khil, Y.M. Ra, D.R. Lee, Polymer 1287 (2003) 44. [13] D. Rohner, D.W. Hutmacher, T.K. Cheng, M. Oberholzer, M. Hammer, Journal of Biomedical Materials Research 574 (2003) 66B. [14] K.J. Lowry, K.R. Hamson, L. Bear, Y.B. Peng, R. Calaluce, M.L. Evans, J.O. Anglen, W.C. Allen, Journal of Biomedical Materials Research 536 (1997) 36.
223
[15] R. Langer, J.P. Vacanti, Science 920 (1993) 260. [16] L.G. Cima, J.P. Vacanti, D. Ingber, D.J. Mooney, R. Langer, Journal of Biomechanical Engineering 143 (1991) 113. [17] B.I. Noh, S.S. Chang, W.C. Moon, S.B. Jung, International Journal of Adhesion and Adhesives 200 (2007) 27. [18] J. Rosenberg, E.J. Small, Current Opinion in Oncology 217 (2003) 15.
Current Applied Physics 9 (2009) 219–223 www.elsevier.com/locate/cap www.kps.or.kr
Contribution of power on cell adhesion using atmospheric dielectric barrier discharge (DBD) plasma system Hyun Uk Lee a, Ye Sul Jeong a, Kwang Nak Koh a, Se Young Jeong a, Hyun-Gyu Kim b, Jong Sung Bae b, Chae Ryong Cho a,* a
Department of Nano Fusion Technology, Pusan National University, 50 Cheonghak-ri, Samnangjin-eup, Miryang, Gyeongnam 627-706, Republic of Korea b Busan Center, Korea Basic Science Institute, Busan 609-735, Republic of Korea Received 6 November 2007; received in revised form 17 January 2008; accepted 22 January 2008 Available online 5 February 2008
Abstract This study examined the effect of the treatment power on the enhanced cell attachment and proliferation on poly e-caprolactone (PCL) films treated with atmospheric plasma using a dielectric barrier discharge method (AP-DBD). The peak intensities of the –CH, C@O, –OH and –COO vibration modes, and binding energies of carbon and oxygen of the AP-DBD treated-PCL film increased with increasing plasma treatment power. The surfaces of the AP-DBD treated-PCL films were also examined for their in vitro cell adhesion properties using human prostate epithelial cells. The results showed that the level of cell attachment and proliferation on the AP-DBD treated-PCL film was ten times better than that observed on the untreated-PCL films. Ó 2008 Elsevier B.V. All rights reserved. PACS: 87.80. y; 87.68.+z; 52.50.Dg; 52.40.Hf; 52.77. j Keywords: Dielectric barrier discharge; Surface modification; Atmospheric plasma; Poly e-caprolactone; Cell adhesion
1. Introduction Plasma treatments are widely used to modify the surface properties of materials in many applications such as improving the adhesion of coatings to metals and polymers, increasing the wettability and printability of polymers, and in the manufacture of semiconductor devices [1,2]. Plasma treatment also improves polymer fiber-matrix adhesion largely by introducing polar or excited groups or even a new polymer layer that can form strong covalent bonds between the fiber and the matrix [3]. The major advantages of plasma treatment over other techniques include modification of the top atomic layers of a substrate, selection of a desired functional group, minimization of thermal degradation and rapid treatment time [4,5]. However, most plasma treatment processes involve a vacuum *
Corresponding author. Tel.: +82 55 350 5297; fax: +82 55 353 1314. E-mail address: [email protected] (C.R. Cho).
1567-1739/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2008.01.014
system, which may not be a continuous process. Plasma treatment with the DBD system does not require a vacuum system and can be operated at atmospheric pressure. The use of atmospheric plasma treatment can easily overcome the limitations imposed by the currently available vacuum-based plasma sterilizers [6,7]. Plasma treatments have many applications, including surface sterilization and/or decontamination in biomedical and food areas, as well as in biological warfare defense to kill anthrax or other biological warfare agents [8–11]. Poly e-caprolactone (PCL) is a semi-crystalline linear hydrophobic polymer and one of the most flexible synthetic biodegradable polymers [12]. It is used as a surgical material in clinics and it has been reported to have biomedical applications in controlled drug delivery systems and implants for orthopedic surgery [13]. Because of its low glass-transition temperature ( 60 °C) and low melting point (60 °C), the PCL amorphous phase displays high molecular mobility at human body temperature [14,15].
220
H.U. Lee et al. / Current Applied Physics 9 (2009) 219–223
However, the use of PCL films as a biomaterial is limited by its hydrophobic nature, which leads to low adhesion to the film. Although PCL films mimic the extra-cellular matrix in living tissues, their poor hydrophilicity results in a low cell loading in the initial stage of cell culture as well as a reduced the ability of cell adhesion, migration, proliferation, and differentiation [16]. Therefore, it is essential to improve the hydrophilicity of PCL to overcome these difficulties. This paper reports the plasma treatment power effect of a PCL film for enhanced cell attachment and proliferation. The chemical bonding states and vibration modes of the functional groups of a PCL film surface modified by AP-DBD were also investigated. 2. Materials and methods AP-DBD surface treatment was carried out in air (25 °C and room humidity = 52%) using a dielectric barrier discharge system (DBD), as shown in Fig. 1. The AP-DBD treatment system consists of an electrode with a length of 150 mm, a grounding plate of 200 mm, dielectric materials and a moving stage. A high frequency, self-tuning power supply of 20 kHz with a peak voltage of 1–10 kV was applied to the electrode to generate the linear micro-streamer discharge between electrodes within a gap of 1.5 mm. Based on previous experience, the typical range of working conditions for processing PCL films includes the input power (adjustable from 100 to 750 W), which were chosen as the operating parameter range. The PCL films were prepared at different AP-DBD treatment powers of 250 W, 280 W and 350 W (frequency: 20 kHz, duty: 10 ls, speed: 1.2 cm/min). Any thermal effects or electrical damages on the plasma treated-PCL films used in this study are observed. The extent of the surface modification of the
Fig. 2. (a) Surface contact angles and (b) AFM surface images of the PCL films according to the AP-DBD treatment power. (Untreated, 250 W, 280 W, and 350 W).
PCL films by the AP-DBD treatment were evaluated by water contact angle (Dataphysics, OCA), atomic force microscopy (AFM, PSIA, XE-120), Fourier-transformation infrared spectroscopy (FTIR, JASCO, FTIR-6300) and X-ray photoelectron spectroscopy (XPS, VG Scientific, ESCALAB250). The surfaces of the AP-DBD treated-PCL films were also examined for their in vitro cell attachment and proliferation using human prostate epithelial cells (HPECs). Fig. 2 shows the wettability and surface morphology of the AP-DBD treated-PCL film at different treatment powers. 3. Results and discussion
Fig. 1. Schematic diagram of the atmospheric plasma using a dielectric barrier discharge (AP-DBD) treatment system.
Fig. 2a shows the contact angles on the PCL film surface after the AP-DBD treatment. The contact angle on the modified-PCL films decreased from 65.3° to 36.3° with increasing treatment power. The decrease in water contact angle was attributed to the surface functionalization reactions, which introduced some hydrophilic groups onto the surface of the PCL films. The surface hydrophilicity
H.U. Lee et al. / Current Applied Physics 9 (2009) 219–223
of the polymers directly influences the adhesion of the interface between the polymer and the over layer material [4–6]. Fig. 2b shows AFM images of the AP-DBD treated-PCL film surface, which was carried out by acquiring a height intensity using identical measurement conditions. The average surface roughness (Ra) of the modified-PCL films increased from 1.6 to 64.6 nm with increasing the treatment power. However, the specific-surface area of the AP-DBD treated-PCL film at 350 W was lower than those of films treated at 250 W and 280 W due to surface damage. Fig. 3 shows the FT-IR absorbance spectra of the APDBD treated-PCL film at different treatment powers. In addition, the intensity of the peaks corresponding to the –OH, –CH3, –CH2, C@O, C–O and –COO functional groups at 3700–3600 cm 1, 2980 cm 1, 2850 cm 1, 1724 cm 1, 1294 cm 1 and 1190–1220 cm 1, respectively, increased with increasing power, as shown in Fig. 3a–d. The spectral changes observed after the AP treatments may be due to surface oxidation of the PCL film to hydrophilic groups, such as oxygen and carbon, on the PCL film surfaces by the active species in the plasma, where oxygen and carbon could originate from the surrounding air and fragment the polymer chains on the surface of the PCL film, as shown in Fig. 3e. The surface chemical bonding states of the AP-DBD treated-PCL film was examined by XPS (Fig. 4). The APDBD treated-PCL film surface showed O1s and C1s components at binding energies of 532.5 eV and 285.1 eV [17], respectively. The peaks for C1s could be fitted to the experimental C1s photopeaks, depending on the chemical bonding states of oxygen atoms bonded to the carbon. The intensity of the deconvoluted peaks at –CH (284.6 eV)
221
Fig. 4. Line-shape analysis of the high-resolution C1s and O1s spectra of the PCL films according to the AP-DBD treatment power. The peaks deconvoluted from the carbon and oxygen spectra are displayed, respectively. (The surface chemical bonding states of the AP-DBD treated-PCL film was examined by X-ray photoelectron spectroscopy).
and C–O (286.6 eV) in the C1s spectra, and that of –OH (531.5 eV) and –COOH (533.2 eV) peaks in the O1s spectrum increased with increasing AP-DBD treatment power. With increasing treatment power, the –OH (531.5 eV) and –COOH (533.2 eV) peaks were also shifted to a higher binding energy due to the increase in the concentration of functional groups. The surface chemical bonding states of these spectra might increase the hydrophilicity of the AP treated-PCL films and consequently improve the cell adhesion properties. In order to investigate the level of cell proliferation, HPECs (ATCC, Manassas) were cultured in RPMI-1640 media (Invitrogen, Carlsbad), supplemented with 10% fetal bovine serum and 1% penicillin and streptomycin in a atmosphere 5% CO2 at 37 °C for 7 days. The HPECs were detached from each sample using trypsin-EDTA, and the cells were counted by a hematocytometer [18]. The results are shown in Fig. 5a. HPECs with a density of 1.5 105 cells/cm2 were seeded on six well plates and pro-
Fig. 3. (a)–(d) FT-IR absorbance spectra of the PCL films according to the AP-DBD treatment power and (e) reaction models of functional group after the plasma treatment. (Untreated, 250 W, 280 W, and 350 W).
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Fig. 5. (a) Cell proliferation of the HPECs on the PCL films according to the atmospheric plasma treatment power and culturing time. SEM images of HPECs grown for 7 days on (b) untreated and (c, d) AP-DBD treated with 280 W. (Fig. 4d is an enlarged SEM image of Fig. 4c).
liferated onto a single layer. The difference in the number of cells attached to the AP-DBD treated-PCL films at different treatment powers was found to be 5 104, 2.3 105, 5.6 105 and 4.7 105 cells/cm2 culturing the cells for 7 days. The level of cell attachment and proliferation on the AP-DBD treated-PCL film at 280 W was ten times that observed on the AP-DBD untreated-PCL film. However, the AP-DBD treated-PCL film at 280 W showed better cell attachment and proliferation than that at 350 W. This was attributed to an increase in the specific-surface area and hydrophilic groups of the AP-DBD treated-PCL film surface at 280 W, but the specific-surface area of AP-DBD treated-PCL film at 350 W might be decreased by the higher plasma power. Fig. 5b–d shows FE-SEM images of the HPECs grown for 7 days after seeding on an untreated and AP-DBD treated-PCL film at 280 W. These results suggest that the AP-DBD treated-PCL film produces a better cell distribution and growth than the untreated-PCL film. The proteins of the cell membrane, which contain hydrophilic amino acids, exist in the outer region due to the repulsion caused by the protein and hydrophobic component at the inner region. Therefore, among the requirements of the matrix for cell culturing, the hydrophilic property of the AP-DBD treated-PCL surface improves the level of cell attachment by increasing the affinity between the protein and AP-DBD treated-PCL surface. In this study, a higher level of HPEC attachment and proliferation on the AP-DBD treated-PCL film might be due to its improved hydrophilic properties through the plasma surface treatment. 4. Summary In summary, the surface rearrangement of PCL films by an AP-DBD treatment was attributed to surface oxidation, which produced hydrophilic groups, such as oxygen and carbon onto the PCL film surface. Therefore, the hydrophilic properties of the AP-DBD treated-PCL film might
be improved by increasing the treatment power, which would improve the adhesion properties. Therefore, the AP-DBD treated-PCL film according to the power provides a better cell distribution and growth than that of the untreated-PCL film. The enhanced cell attachment and biocompatibility of the PCL film by the AP treatment was also attributed to both the increase in specific-surface area and number of hydrophilic groups on the AP-DBD treated-PCL film surface. The AP-DBD treated-PCL film underlines the cytocompatibility of a PCL film as well as its potential utility as a suitable scaffold in tissue engineering and cell chip applications. Acknowledgement This work was supported by SMEs Technology Innovation Program. References [1] S. Marais, M. Metayer, F. Poncin-Epaillard, Journal of Fluorine Chemistry 199 (2001) 107. [2] S. Tajima, K. Komvopoulos, Applied Physics Letter 124102 (2006) 89. [3] J. Hopkins, J.P.S. Badyal, Langmuir 3666 (1996) 12. [4] G.H. Yang, E.T. Kang, K.G. Neoh, Journal of Polymer Science 3498 (2000) 38. [5] J. Hyun, Polymer 6473 (2001) 42. [6] C.T. Montie, K.K. Wintenberg, J.R. Roth, IEEE Transactions on Plasma Science 33 (2005) 2. [7] M. Laroussi, J.P. Richardson, F.C. Dobbs, Applied Physics Letter 4 (2002) 81. [8] M. Nagatsu, F. Terashita, H. Nonaka, Applied Physics Letter 211502 (2005) 86. [9] X.T. Deng, J.J. Shi, G. Shama, M.G. Kong, Applied Physics Letter 153901 (2005) 87. [10] Q.S. Yu, C. Huang, F.H. Hsieh, H. Huff, Y. Duan, Applied Physics Letter 13903 (2006) 88. [11] T. Sato, T. Miyahara, A. Doi, S. Ochiai, T. Urayama, T. Nakatani, Applied Physics Letter 73902 (2006) 89.
H.U. Lee et al. / Current Applied Physics 9 (2009) 219–223 [12] K.H. Lee, H.Y. Kim, M.S. Khil, Y.M. Ra, D.R. Lee, Polymer 1287 (2003) 44. [13] D. Rohner, D.W. Hutmacher, T.K. Cheng, M. Oberholzer, M. Hammer, Journal of Biomedical Materials Research 574 (2003) 66B. [14] K.J. Lowry, K.R. Hamson, L. Bear, Y.B. Peng, R. Calaluce, M.L. Evans, J.O. Anglen, W.C. Allen, Journal of Biomedical Materials Research 536 (1997) 36.
223
[15] R. Langer, J.P. Vacanti, Science 920 (1993) 260. [16] L.G. Cima, J.P. Vacanti, D. Ingber, D.J. Mooney, R. Langer, Journal of Biomechanical Engineering 143 (1991) 113. [17] B.I. Noh, S.S. Chang, W.C. Moon, S.B. Jung, International Journal of Adhesion and Adhesives 200 (2007) 27. [18] J. Rosenberg, E.J. Small, Current Opinion in Oncology 217 (2003) 15.