- Email: [email protected]
Controlled formation of surface hydrophilicity enhanced chitosan film by layer-by-layer electro-assembly
Materials Science and Engineering C 56 (2015) 518–521
Contents lists available at ScienceDirect
Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec
Controlled formation of surface hydrophilicity enhanced chitosan film by layer-by-layer electro-assembly Li Chen, Kuo Liu, Jia-Ru Ye, Qing Shen ⁎ State Key Laboratory for Modification of Chemical Fiber and Polymer Materials, Polymer Department of Donghua University, 2999 N. Renmin Rd. Songjiang, 201620 Shanghai, China
a r t i c l e
i n f o
Article history: Received 19 February 2015 Received in revised form 6 May 2015 Accepted 10 July 2015 Available online 16 July 2015 Keywords: Chitosan film Hydrophilicity Layer-by-layer electro-assembly
a b s t r a c t Several surface hydrophilicity enhanced chitosan, CS, films were controllably formed by using the layer-by-layer electro-assembly, LBLEA, method with varied voltages. Experimentally, an employed electrostatic generator was employed by taking its anode and cathode electrodes alternatively linking to the CS solution or silicon plate to form two opposite cycles corresponding to the electrostatic force, EF, enhancement or reduction, respectively. Wetting results showed that the water contact angle, θW, on those CS film surfaces was gradually reduced with the applied voltage increase, especially by EF reduction, e.g. the θW on 0 V sample at about 55° and on 4 kV EFreduction formed sample at about 20°. AFM images comparison showed that the LBLEA process can control the surface structure for CS film. ATR–FTIR spectra comparison showed that the EF reduction process would reveal the C–O groups on CS film surface to enhance the hydrophilicity. © 2015 Elsevier B.V. All rights reserved.
1. Introduction
2. Materials and methods
Chitosan, CS, is derived by de-acetylating of chitin. CS is the second most abundant biopolymer in nature after cellulose [1,2]. CS has special β(1 → 4) linked D-glucosamine structure and this leads it has some important advantages, e.g. biocompatibility, biodegradability and notoxicity [1–5]. CS is a positive polyelectrolyte with bad hydrophilic due to the water contact angles, θW, on its surface at about 50–60° [6–10]. This thus limited its application due to somewhere the used CS is wished to have either enhanced hydrophilic or in hydrophobic [10–14]. As known, the surface properties of CS can be modified by chemical [2] or physical methods, e.g. the UV irradiation [15] and the low-energy electron irradiation [16]. Our recent study showed that the hydrophilic CS surface can be turned into hydrophobic by layer-by-layer electroassembling, LBLEA, the negative lignosulfonate [5]. However, it is truly yet without a method can be directly applied fabrication of CS film with controlled hydrophilicity. In this work, we introduced a case to directly fabricate the CS film with enhanced hydrophilicity. Experimentally, we again used the LBLEA method, however, only the CS was used. As the same as previously, the anode and cathode electrodes of the electrostatic generator were alternatively linked to the positive CS solution and the used silicon plate to form two opposite cycles in relation to the electrostatic forces, EF, in enhancement or reduction, respectively [5].
2.1. Materials
⁎ Corresponding author. Tel.: 86-21-62822096. E-mail address: [email protected] (Q. Shen).
http://dx.doi.org/10.1016/j.msec.2015.07.021 0928-4931/© 2015 Elsevier B.V. All rights reserved.
A commercial CS powder in microsize (Weifang Kehai Chitosan Co., Ltd, China) was used as received. In terms of the provider, this CS has a molecular weight of about 3 × 105 g/mol and a de-acetylation degree of about 95%, respectively [5].
2.2. Formation of chitosan film by layer-by-layer electro-assembly The CS solution was prepared by dissolving the CS powder in acetic acid at a concentration of 2 mg/ml and pH at 4.1, respectively [5]. During the assembly process, a single crystal silicon plate (Zhejiang CrystalOptech Co. Ltd. China) was used and pretreated as the same as previously [5]. The EF-controlled LBLEA process was performed as Fig. 1 described by taking the anode and cathode electrodes alternatively to link to either the positive CS solution or the silicon plate, respectively. In presented two cycles, the linkage presented as Fig. 1 left described by inserting the anode electrode into the positive CS solution should cause the occurred EF in enhancement, and the linkage described as Fig. 1 right should correspond to the EF reduction. By varying the applied voltages, therefore, the EF enhancement or reduction would be controlled in formation of those CS films. During this electro-assembly process corresponding to different applied voltages, the substrate was immersed in CS+ solution for each run and each run was kept about 10 min at 25 °C, then air dried for next running under an air stream flow condition.
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
EF enhancement
519
EF reduction
Fig. 1. Scheme on the formation of CS film by LBLEA in relation to the control of the EF in enhancement or reduction, respectively.
2.3. Characterization
3. Results and discussions
The wetting was performed by means of the sessile drop contact angle measurement using the OCA40 Micro (Dataphysics Co., Ltd). During the measurement, the droplet volume was controlled constantly at about 1 μl for each drop and the temperature was controlled in constant, 25 °C. The surface topography and roughness of the multilayer film were analyzed using a NanoScope IV (Veeco Co., Ltd) atomic force microscopy, AFM, with a tapping mode. The attenuated total reflectance Fourier transform infrared spectroscopy, ATR–FTIR, (NEXUS-670, Nicolet Co., Ltd) was applied to present spectra in transmission mode by aligning the film on a silicon wafer substrate (1–2 cm2) at a Brewster's angle of 75° with respect to the incident beam.
3.1. Effect of applied voltages on the wettability and morphology of chitosan films To enhance the hydrophilicity of CS seems to be not easy because Praxedes et al. have applied the UV irradiation to treat CS [15]. In terms of them, the θW on CS surface was reduced very few because the original surface presented value at about 85° and after UV irradiation reduced to at about 75° [15]. In addition, the electro-deposition enhanced the hydrophilicity of CS was also found few [17]. The wettability of LBLEA formed CS films in relation to various applied voltages was showed in Fig. 2. We found that the water contact angle, θW, on these CS films obviously reduced because it on 0 V sample surface at 55.3 ± 1.00° in good agreement with our previous report [5]
60
(CS/CS)n
θW (0)
50
40
30
EF enhancement EF reduction
20 0
1000
2000
3000
4000
ρ (V)
0V formed CS film
4kV-EF reduction formed CS film
θW=55.3±1.000
θW=21.4±0.350
Fig. 2. Wettability of the LBLEA formed CS films in relation to the EF enhancement or reduction, respectively.
520
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
and literature reported values [18,19], while on all LBLEA formed sample surfaces obviously reduced with the applied voltage increase, especially for 4 kV-EF reduction formed sample at 21.4 ± 0.35°. This importantly indicated that this LBLEA method can directly fabricate CS film with enhanced hydrophilicity. In terms of Fig. 2 presented values, the EF reduction presented θW is obviously lower than that of the EF enhancement yielded result. This suggested that the wettability of CS film can be controllably formed by the LBLEA process by varying the electrode linkage to control the EF. Obviously, the method we used is better for enhancing the hydrophilicity for forming CS film as compared with literature reported cases [15–19]. The AFM images recorded in tapping model on two LBLEA formed CS films were prepared in Fig. 3 to compare to the 0 V sample. It was found that the CS film formed at 0 V showed smooth surface while two 4 kV LBLEA formed samples both showed surface roughness, especially by reducing the EF. This finding is interesting because this indicated that the CS films formed by electric assembly would increase the surface roughness. We believe that this change would influence the application of those CS films. The effect of EF enhancement or reduction on CS film was also known from these AFM images (Fig. 3), because a comparison found that the CS film surface presented random spots due to EF enhancement (Fig. 3 middle), and presented bright and right orientated
Voltage
layers due to EF reduction (Fig. 3 bottom). These differences importantly implied that the CS film surface structure was influenced and controlled by EF-controllable LBLEA method.
3.2. Effect of applied voltages on the structure of chitosan films In order to understand the reason why the surface of CS film was changed by LBLEA method, we furthermore applied ATR–FTIR spectroscopy to characterize these CS films. According to recorded ATR–FTIR spectra (Fig. 4), these CS films all showed typical peaks at 2099 cm−1 due to CH3 stretching, 1452 cm− 1 due to CH2 deformation modes, 1109 cm− 1 due to C–O and C–C stretching from COH binding, 885 cm−1 due to associated with the coupled C–O and C–C stretching vibrations of the polysaccharide molecules, 736 cm− 1 due to CH–CH stretching, and 617 cm−1 due to C_O stretching [20]. Since only the 4 kV EF reduction-formed sample showed a new peak at about 1220 cm−1 corresponding to the C–O group stretching [20], which others without appearance, this importantly indicated that the EF reduction-controlled LBLEA process revealed the C–O group on CS film surface. In other words, this indicated that this EF-controllable LBLEA method can modify the chemical structure of CS film surface.
AFM images
0V
4kV EF enhancement
4 kV EF reduction
Fig. 3. AFM images of the CS films formed by LBLEA in relation to the EF enhancement or reduction, respectively.
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
521
4. Conclusions
0V
4kV, EF enhancement
In summary, the CS film can be formed with enhanced hydrophilicity by using the LBLEA method. Since the LBLEA process can be performed in relation to the EF enhancement or reduction, this work has proven that the EF reduction is better for enhancing the hydrophilicity for CS film because it can cause the C–O groups revealing on the CS surface to increase the roughness and hydrophilicity than that of the EF enhancement.
750
1000
1250
1500
References
2099
1452
1220
1109
885
617 500
736
4kV, EF reduction
1750
2000
2250
2500
-1
Wavenumber (cm ) Fig. 4. ATR–FTIR spectra of the CS films formed by LBLEA in relation to the EF enhancement or reduction, respectively.
Thus, the reason why the surface roughness of CS film was increased by LBLEA process is known due to the revelation of the C–O groups. Furthermore, the AFM images showed bright and right orientated layers (Fig. 3 bottom) are also known probably corresponding to the revealed C–O groups. On the basis of above discussions, a related mechanism on forming the hydrophilicity enhanced CS film is primarily known. In the presence of an extra electric field, the surface tension of CS solution was reduced with the voltage increase to influence the film formation and related structure [5]. The alternatively electrode linkages controlled the assembly process and the film surface structure because the occurred EF to be in enhancement or reduction, and the latter would cause the C–O groups revealing on the CS film surface to enhance the surface hydrophilicity.
[1] R.A.A. Muzzarelli, in: P. Jolles, R.A.A. Muzzarelli (Eds.), Chitin and Chitinases, Birkhauser Verlag, Basel, Switzerland, 1999. [2] M. Dasha, F. Chiellini, R.M. Ottenbriteb, E. Chiellini, Prog. Polym. Sci. 36 (2011) 981–1014. [3] Q. Yang, F.D. Dou, B.R. Liang, Q. Shen, Carbohydr. Polym. 59 (2005) 205–210. [4] Q. Yang, F.D. Dou, B.R. Liang, Q. Shen, Carbohydr. Polym. 61 (2005) 393–398. [5] J.R. Ye, L. Chen, Y. Zhang, Q.C. Zhang, Q. Shen, RSC Adv. 4 (2014) 58200. [6] S. Kim, Y. Liu, M.W. Gaber, J.D. Bumgardner, W.O. Haggard, Y. Yang, J. Biomed. Mater. Res. Part B 90B (2009) 145–155. [7] M.G.N. Campos, N. Satsangi, H.R. Rawls, L.H.L. Mei, Macromol. Symp. 279 (2009) 169–174. [8] N.E. Suyatma, L. Tighzert, A. Copinet, J. Agric. Food Chem. 53 (2005) 3950–3957. [9] Q.S. Zhao, Q.X. Ji, K. Xing, X.Y. Li, C.S. Liu, X.G. Chen, Carbohydr. Polym. 76 (2009) 410–416. [10] Z. Cui, E.S. Beach, P.T. Anastas, Green Chem. Lett. Rev. 4 (2011) 35–40. [11] S. Hohne, R. Frenzel, A. Heppe, F. Simon, Biomacromolecules 8 (2007) 2051–2058. [12] A.A. Jensen, H. Leffers, Int. J. Androl. 31 (2008) 161–169. [13] G. Crini, P.M. Badot, Prog. Polym. Sci. 33 (2008) 399–447. [14] J.K.F. Suh, H.W.T. Matthew, Biomaterials 21 (2000) 2589–2598. [15] A.P.P. Praxedes, A.J.C. da Silva, R.C. da Silva, R.P.A. Lima, J. Tonholo, A.S. Ribeiro, I.N. de Oliveira, J. Colloid Interface Sci. 376 (2012) 255–261. [16] A. Ryzhkova, U. Jarzak, A. Schafer, M. Baumer, P. Swiderek, Carbohydr. Polym. 83 (2011) 608–615. [17] S.T. Koev, P.H. Dykstra, X. Luo, W. Rubloff, W.E. Bentley, G.F. Payne, R. Ghodssi, Lab Chip 10 (2010) 3026–3042. [18] I.F. Amaral, P.L. Granja, Luis V. Melo, B. Saramago, M.A. Barbosa, J. Appl. Polym. Sci. 102 (2006) 276–284. [19] K. Tomihata, Y. Ikada, Biomaterials 18 (1997) 567. [20] N.L. Delgadillo-Armendariz, N.A. Rangel-Vázquez, A.I. García-Castanon, Spectrochim. Acta A 120 (2014) 524–528.
Contents lists available at ScienceDirect
Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec
Controlled formation of surface hydrophilicity enhanced chitosan film by layer-by-layer electro-assembly Li Chen, Kuo Liu, Jia-Ru Ye, Qing Shen ⁎ State Key Laboratory for Modification of Chemical Fiber and Polymer Materials, Polymer Department of Donghua University, 2999 N. Renmin Rd. Songjiang, 201620 Shanghai, China
a r t i c l e
i n f o
Article history: Received 19 February 2015 Received in revised form 6 May 2015 Accepted 10 July 2015 Available online 16 July 2015 Keywords: Chitosan film Hydrophilicity Layer-by-layer electro-assembly
a b s t r a c t Several surface hydrophilicity enhanced chitosan, CS, films were controllably formed by using the layer-by-layer electro-assembly, LBLEA, method with varied voltages. Experimentally, an employed electrostatic generator was employed by taking its anode and cathode electrodes alternatively linking to the CS solution or silicon plate to form two opposite cycles corresponding to the electrostatic force, EF, enhancement or reduction, respectively. Wetting results showed that the water contact angle, θW, on those CS film surfaces was gradually reduced with the applied voltage increase, especially by EF reduction, e.g. the θW on 0 V sample at about 55° and on 4 kV EFreduction formed sample at about 20°. AFM images comparison showed that the LBLEA process can control the surface structure for CS film. ATR–FTIR spectra comparison showed that the EF reduction process would reveal the C–O groups on CS film surface to enhance the hydrophilicity. © 2015 Elsevier B.V. All rights reserved.
1. Introduction
2. Materials and methods
Chitosan, CS, is derived by de-acetylating of chitin. CS is the second most abundant biopolymer in nature after cellulose [1,2]. CS has special β(1 → 4) linked D-glucosamine structure and this leads it has some important advantages, e.g. biocompatibility, biodegradability and notoxicity [1–5]. CS is a positive polyelectrolyte with bad hydrophilic due to the water contact angles, θW, on its surface at about 50–60° [6–10]. This thus limited its application due to somewhere the used CS is wished to have either enhanced hydrophilic or in hydrophobic [10–14]. As known, the surface properties of CS can be modified by chemical [2] or physical methods, e.g. the UV irradiation [15] and the low-energy electron irradiation [16]. Our recent study showed that the hydrophilic CS surface can be turned into hydrophobic by layer-by-layer electroassembling, LBLEA, the negative lignosulfonate [5]. However, it is truly yet without a method can be directly applied fabrication of CS film with controlled hydrophilicity. In this work, we introduced a case to directly fabricate the CS film with enhanced hydrophilicity. Experimentally, we again used the LBLEA method, however, only the CS was used. As the same as previously, the anode and cathode electrodes of the electrostatic generator were alternatively linked to the positive CS solution and the used silicon plate to form two opposite cycles in relation to the electrostatic forces, EF, in enhancement or reduction, respectively [5].
2.1. Materials
⁎ Corresponding author. Tel.: 86-21-62822096. E-mail address: [email protected] (Q. Shen).
http://dx.doi.org/10.1016/j.msec.2015.07.021 0928-4931/© 2015 Elsevier B.V. All rights reserved.
A commercial CS powder in microsize (Weifang Kehai Chitosan Co., Ltd, China) was used as received. In terms of the provider, this CS has a molecular weight of about 3 × 105 g/mol and a de-acetylation degree of about 95%, respectively [5].
2.2. Formation of chitosan film by layer-by-layer electro-assembly The CS solution was prepared by dissolving the CS powder in acetic acid at a concentration of 2 mg/ml and pH at 4.1, respectively [5]. During the assembly process, a single crystal silicon plate (Zhejiang CrystalOptech Co. Ltd. China) was used and pretreated as the same as previously [5]. The EF-controlled LBLEA process was performed as Fig. 1 described by taking the anode and cathode electrodes alternatively to link to either the positive CS solution or the silicon plate, respectively. In presented two cycles, the linkage presented as Fig. 1 left described by inserting the anode electrode into the positive CS solution should cause the occurred EF in enhancement, and the linkage described as Fig. 1 right should correspond to the EF reduction. By varying the applied voltages, therefore, the EF enhancement or reduction would be controlled in formation of those CS films. During this electro-assembly process corresponding to different applied voltages, the substrate was immersed in CS+ solution for each run and each run was kept about 10 min at 25 °C, then air dried for next running under an air stream flow condition.
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
EF enhancement
519
EF reduction
Fig. 1. Scheme on the formation of CS film by LBLEA in relation to the control of the EF in enhancement or reduction, respectively.
2.3. Characterization
3. Results and discussions
The wetting was performed by means of the sessile drop contact angle measurement using the OCA40 Micro (Dataphysics Co., Ltd). During the measurement, the droplet volume was controlled constantly at about 1 μl for each drop and the temperature was controlled in constant, 25 °C. The surface topography and roughness of the multilayer film were analyzed using a NanoScope IV (Veeco Co., Ltd) atomic force microscopy, AFM, with a tapping mode. The attenuated total reflectance Fourier transform infrared spectroscopy, ATR–FTIR, (NEXUS-670, Nicolet Co., Ltd) was applied to present spectra in transmission mode by aligning the film on a silicon wafer substrate (1–2 cm2) at a Brewster's angle of 75° with respect to the incident beam.
3.1. Effect of applied voltages on the wettability and morphology of chitosan films To enhance the hydrophilicity of CS seems to be not easy because Praxedes et al. have applied the UV irradiation to treat CS [15]. In terms of them, the θW on CS surface was reduced very few because the original surface presented value at about 85° and after UV irradiation reduced to at about 75° [15]. In addition, the electro-deposition enhanced the hydrophilicity of CS was also found few [17]. The wettability of LBLEA formed CS films in relation to various applied voltages was showed in Fig. 2. We found that the water contact angle, θW, on these CS films obviously reduced because it on 0 V sample surface at 55.3 ± 1.00° in good agreement with our previous report [5]
60
(CS/CS)n
θW (0)
50
40
30
EF enhancement EF reduction
20 0
1000
2000
3000
4000
ρ (V)
0V formed CS film
4kV-EF reduction formed CS film
θW=55.3±1.000
θW=21.4±0.350
Fig. 2. Wettability of the LBLEA formed CS films in relation to the EF enhancement or reduction, respectively.
520
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
and literature reported values [18,19], while on all LBLEA formed sample surfaces obviously reduced with the applied voltage increase, especially for 4 kV-EF reduction formed sample at 21.4 ± 0.35°. This importantly indicated that this LBLEA method can directly fabricate CS film with enhanced hydrophilicity. In terms of Fig. 2 presented values, the EF reduction presented θW is obviously lower than that of the EF enhancement yielded result. This suggested that the wettability of CS film can be controllably formed by the LBLEA process by varying the electrode linkage to control the EF. Obviously, the method we used is better for enhancing the hydrophilicity for forming CS film as compared with literature reported cases [15–19]. The AFM images recorded in tapping model on two LBLEA formed CS films were prepared in Fig. 3 to compare to the 0 V sample. It was found that the CS film formed at 0 V showed smooth surface while two 4 kV LBLEA formed samples both showed surface roughness, especially by reducing the EF. This finding is interesting because this indicated that the CS films formed by electric assembly would increase the surface roughness. We believe that this change would influence the application of those CS films. The effect of EF enhancement or reduction on CS film was also known from these AFM images (Fig. 3), because a comparison found that the CS film surface presented random spots due to EF enhancement (Fig. 3 middle), and presented bright and right orientated
Voltage
layers due to EF reduction (Fig. 3 bottom). These differences importantly implied that the CS film surface structure was influenced and controlled by EF-controllable LBLEA method.
3.2. Effect of applied voltages on the structure of chitosan films In order to understand the reason why the surface of CS film was changed by LBLEA method, we furthermore applied ATR–FTIR spectroscopy to characterize these CS films. According to recorded ATR–FTIR spectra (Fig. 4), these CS films all showed typical peaks at 2099 cm−1 due to CH3 stretching, 1452 cm− 1 due to CH2 deformation modes, 1109 cm− 1 due to C–O and C–C stretching from COH binding, 885 cm−1 due to associated with the coupled C–O and C–C stretching vibrations of the polysaccharide molecules, 736 cm− 1 due to CH–CH stretching, and 617 cm−1 due to C_O stretching [20]. Since only the 4 kV EF reduction-formed sample showed a new peak at about 1220 cm−1 corresponding to the C–O group stretching [20], which others without appearance, this importantly indicated that the EF reduction-controlled LBLEA process revealed the C–O group on CS film surface. In other words, this indicated that this EF-controllable LBLEA method can modify the chemical structure of CS film surface.
AFM images
0V
4kV EF enhancement
4 kV EF reduction
Fig. 3. AFM images of the CS films formed by LBLEA in relation to the EF enhancement or reduction, respectively.
L. Chen et al. / Materials Science and Engineering C 56 (2015) 518–521
521
4. Conclusions
0V
4kV, EF enhancement
In summary, the CS film can be formed with enhanced hydrophilicity by using the LBLEA method. Since the LBLEA process can be performed in relation to the EF enhancement or reduction, this work has proven that the EF reduction is better for enhancing the hydrophilicity for CS film because it can cause the C–O groups revealing on the CS surface to increase the roughness and hydrophilicity than that of the EF enhancement.
750
1000
1250
1500
References
2099
1452
1220
1109
885
617 500
736
4kV, EF reduction
1750
2000
2250
2500
-1
Wavenumber (cm ) Fig. 4. ATR–FTIR spectra of the CS films formed by LBLEA in relation to the EF enhancement or reduction, respectively.
Thus, the reason why the surface roughness of CS film was increased by LBLEA process is known due to the revelation of the C–O groups. Furthermore, the AFM images showed bright and right orientated layers (Fig. 3 bottom) are also known probably corresponding to the revealed C–O groups. On the basis of above discussions, a related mechanism on forming the hydrophilicity enhanced CS film is primarily known. In the presence of an extra electric field, the surface tension of CS solution was reduced with the voltage increase to influence the film formation and related structure [5]. The alternatively electrode linkages controlled the assembly process and the film surface structure because the occurred EF to be in enhancement or reduction, and the latter would cause the C–O groups revealing on the CS film surface to enhance the surface hydrophilicity.
[1] R.A.A. Muzzarelli, in: P. Jolles, R.A.A. Muzzarelli (Eds.), Chitin and Chitinases, Birkhauser Verlag, Basel, Switzerland, 1999. [2] M. Dasha, F. Chiellini, R.M. Ottenbriteb, E. Chiellini, Prog. Polym. Sci. 36 (2011) 981–1014. [3] Q. Yang, F.D. Dou, B.R. Liang, Q. Shen, Carbohydr. Polym. 59 (2005) 205–210. [4] Q. Yang, F.D. Dou, B.R. Liang, Q. Shen, Carbohydr. Polym. 61 (2005) 393–398. [5] J.R. Ye, L. Chen, Y. Zhang, Q.C. Zhang, Q. Shen, RSC Adv. 4 (2014) 58200. [6] S. Kim, Y. Liu, M.W. Gaber, J.D. Bumgardner, W.O. Haggard, Y. Yang, J. Biomed. Mater. Res. Part B 90B (2009) 145–155. [7] M.G.N. Campos, N. Satsangi, H.R. Rawls, L.H.L. Mei, Macromol. Symp. 279 (2009) 169–174. [8] N.E. Suyatma, L. Tighzert, A. Copinet, J. Agric. Food Chem. 53 (2005) 3950–3957. [9] Q.S. Zhao, Q.X. Ji, K. Xing, X.Y. Li, C.S. Liu, X.G. Chen, Carbohydr. Polym. 76 (2009) 410–416. [10] Z. Cui, E.S. Beach, P.T. Anastas, Green Chem. Lett. Rev. 4 (2011) 35–40. [11] S. Hohne, R. Frenzel, A. Heppe, F. Simon, Biomacromolecules 8 (2007) 2051–2058. [12] A.A. Jensen, H. Leffers, Int. J. Androl. 31 (2008) 161–169. [13] G. Crini, P.M. Badot, Prog. Polym. Sci. 33 (2008) 399–447. [14] J.K.F. Suh, H.W.T. Matthew, Biomaterials 21 (2000) 2589–2598. [15] A.P.P. Praxedes, A.J.C. da Silva, R.C. da Silva, R.P.A. Lima, J. Tonholo, A.S. Ribeiro, I.N. de Oliveira, J. Colloid Interface Sci. 376 (2012) 255–261. [16] A. Ryzhkova, U. Jarzak, A. Schafer, M. Baumer, P. Swiderek, Carbohydr. Polym. 83 (2011) 608–615. [17] S.T. Koev, P.H. Dykstra, X. Luo, W. Rubloff, W.E. Bentley, G.F. Payne, R. Ghodssi, Lab Chip 10 (2010) 3026–3042. [18] I.F. Amaral, P.L. Granja, Luis V. Melo, B. Saramago, M.A. Barbosa, J. Appl. Polym. Sci. 102 (2006) 276–284. [19] K. Tomihata, Y. Ikada, Biomaterials 18 (1997) 567. [20] N.L. Delgadillo-Armendariz, N.A. Rangel-Vázquez, A.I. García-Castanon, Spectrochim. Acta A 120 (2014) 524–528.