PVA blended hydrogel membranes

Journal of Membrane Science 236 (2004) 39–51

Evaluation of chitosan/PVA blended hydrogel membranes Jen Ming Yang a,∗ , Wen Yu Su a , Te Lang Leu b , Ming Chien Yang b a b

Department of Chemical and Materials Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan, ROC Department of Polymer Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, ROC Received 15 August 2003; received in revised form 13 February 2004; accepted 15 February 2004

Abstract Blended membranes of chitosan and poly(vinyl alcohol) (PVA) in various ratios were prepared and treated with formaldehyde. Electron spectroscopy for chemical analysis of the membrane showed that the –NH2 group in chitosan changed into –N=C group after membrane treatment with formaldehyde. From the spectral change of FTIR, the hydroxyl groups disappeared and an acetal ring and ether linkage were formed for the reaction between the hydroxyl groups of PVA and formaldehyde. The results of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) showed that (1) the crystalline area in PVA decreased after treatment with formaldehyde, (2) chitosan and PVA are not very compatible in the chitosan/PVA blended hydrogel membrane and (3) the thermostability of the membranes is enhanced by formaldehyde as crosslink agent. The effect of chitosan content on the water content and water vapor transmission rates on the blended hydrogel membrane were determined. It was found that the water content and water vapor transmission rates on the blended hydrogel membrane increased with increasing chitosan content. In antibacterial assessment, it appears that the antibacterial activity of all chitosan/PVA blended hydrogel membranes is similar. The viable cell number of aurococcus on the various chitosan/PVA blended hydrogel membranes was about (2.5 ± 0.5) × 107 cells/ml. The permeation of creatinine, 5-FU, uric acid and vitamin B12 through the chitosan/PVA blended hydrogel membranes were conducted. The linear relationship between permeability of creatinine, 5-FU and vitamin B12 molecules and chitosan content in the chitosan/PVA blended hydrogel membranes were found. As the electrostatic attraction between the uric acid and chitosan in the membrane, the permeation of uric acid through the chitosan/PVA blended hydrogel membranes is higher for the membranes with chitosan content higher than 80% in the blended hydrogel membranes. © 2004 Elsevier B.V. All rights reserved. Keywords: Chitosan/PVA blended membrane; Permeability of solute; 5-FU; Uric acid

1. Introduction Hydrogels exhibit the ability to swell in water and retain a significant fraction of water within its structure without dissolving. It has physical properties similar to those of human tissues and possesses excellent tissue compatibility. The main disadvantage of hydrogels is their poor mechanical properties after swelling. In order to eliminate the disadvantage, hydrogels can be modified by physical blending [1–5] or/and chemical modification by grafting [6–10], interpenetrating polymer networks [11–12] and crosslinking method [5,13–15]. Chitosan (poly-␤(1,4)-d-glucosamine), a cationic polysaccharide, is obtained by alkaline deacetylation of chitin,

∗

Corresponding author. Tel.: +886-3-2118800x5290. E-mail address: [email protected] (J.M. Yang).

0376-7388/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2004.02.005

the principal exoskeletal component in crustaceans. As the combination of properties of chitosan such as water binding capacity, fat binding capacity, bioactivity, biodegradability, nontoxicity, biocompatibility, and antifungal activity, chitosan and its modified analogs have shown many applications in medicine, cosmetics, agriculture, biochemical separation systems, tissue engineering, biomaterials and drug controlled release systems [15–21]. Because of the good chemical stability, film-forming ability and high hydrophilicity, the studies on diffusive permeabilities of solutes in poly(vinyl alcohol) (PVA) gel membranes and the application for separation have been reported [13–14,22–25]. In addition, since PVA is biocompatible and nontoxic, and exhibits minimal cell adhesion and protein absorption, PVA membranes have been developed for biomedical applications [2–5,26–29]. As the specific intermolecular interactions between PVA and chitosan in the blends, the blend of PVA/chitosan has good

40

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

mechanical properties and the applications of PVA/chitosan blends have been reported [3–5,30–32]. Microcapsules and nanoparticles have been widely investigated for applications in drug release systems. To prevent the drug from rapidly releasing, the use of enteric polymers as protective drug coatings has been developed [33]. 5-Fluorouracil is antineoplastic and the choice in the treatment of carcinoma of colon or rectum, and is also used in the treatment of precancerous dermatoses, especially actinic keratosis for which is the treatment of choice if the lesions are multiple [34]. The cytotoxic anticancer drug often causes severe side effects because it does not act selectively on the target. In order to control the release rate of 5-FU, chitosan/PVA blended hydrogel membranes can be used as the protective drug coatings. In the pre-study of 5-FU containing drug-containing nanoparticles, the permeability of 5-FU through chitosan/PVA blended hydrogel membranes is evaluated in this study. In this study the preparation of chitosan/PVA blended hydrogel membranes treated with formaldehyde is reported. The blended hydrogel membranes were characterized by ESCA and FTIR. The thermal stability of the chitosan/PVA membrane was studied with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The effect of chitosan content on water absorption of and water vapor transmission rates on the blended hydrogel membrane were determined. In addition, antibacterial assessment, as well as the permeation of 5-FU on the chitosan/PVA blended hydrogel membranes, were conducted. As chitosan membranes have been found to have excellent film-forming properties and high mechanical strength suitable for haemodialysis [1,35], the permeability of creatinine, uric acid and vitamin B12 through the chitosan/PVA blended hydrogel membranes were also evaluated.

plate by soaking in 12 wt.% NaOH(aq) at room temperature for 1 h, washed with distillated water, then soaked in distillated water for 24 h and lyophilized it. The chemical compositions of these membranes were characterized with an ESCA 2100VG Scientific and a Perkin-Elmer model 567 IR spectrometer. The thermal properties were evaluated with DSC (Du Pont 2100 DSC V4 OB) and TAG (Du Pont 9900 TA) systems equipped with a 951 TGA module. The DSC scans were at 10 ◦ C/min. The TGA thermograms were measured in a temperature range 30–800 ◦ C at a heating rate of 10 ◦ C/min. Dynamic mechanical measurement of specimens was performed using a Du Pont 2980 DMA in a temperature range 0–200 ◦ C at 1 Hz and a temperature sweep rate of 5 ◦ C/min. The sinusoidal oscillation amplitude was set at 20 ␮m. 2.2. Measurement of water content and water vapor transmission rates (WVTR) on the chitosan/PVA blended hydrogel membranes The chitosan/PVA blended hydrogel membrane was cut into 6 × 6 cm2 and dried in a vacuum oven at 110 ◦ C for 24 h to determine their dry weight (Wd ). Water content was measured by immersing the chitosan/PVA blended hydrogel membrane in distilled water at 23 ◦ C for 2 h. The wet weight (Wt ) was determined by wiping off the surface water with a piece of filter paper. The absorbed water content was then calculated by
 Wt − Wd water content,W (%) = × 100 Wt The water vapor transmission rates (WVTR) were determined according the method of previous study [36].

3. Antibacterial assessment 2. Materials and methods 2.1. Preparation of chitosan/PVA blended hydrogel membranes 2.5 wt.% chitosan solutions were prepared by dissolving chitosan with 85% deacetylation and molecular weight about 635,000 (Chitin, Chitosan Inc., Taiwan) in 1% acetic acid solution at ambient temperature with stirring for overnight. The solution was filtered by filter before use. 10 wt.% PVA solutions were prepared by dissolving PVA (weight average molecular weight being about 75 000, Sigma) in 80 ◦ C distilled water with stirring for 4 h. Then the mixture of chitosan and PVA solution were stirred with different wt.% of chitosan from 20 to 100 wt.% for 24 h and cast in petri-dish at ambient temperature for 48 h and heating at 60 and 140 ◦ C for 2 and 4 h, respectively. After heating treatment, the membranes were soaked in 2.5 wt.% formaldehyde solution with 17 wt.% H2 SO4(aq) . The membranes were removed from the

The antibacterial assessment was similar to our previous study [37]. Bactericidal activity was evaluated from examining the killing rate by the viable cell counting technique against aurococcus. One loopful of the bacterial was inoculated in 150 ml of nutrient broth at 37 ◦ C for 18 h in a test tube. The chitosan/PVA blended hydrogel membranes were contacted with 2 ml solution having 107 cells/ml for aurococcus to assess their bactericidal activities. After 18 h, 1 ml of same culture was added to 9 ml of distilled water, and several decimal solutions were repeated. From this diluted solution, the surviving bacteria were counted by the spread plate method. After inoculation, the plates were kept at 37 ◦ C and the colonies were counted after 18 h.

4. Permeation studies Permeation studies were performed using side-by-side diffusion cells. Preswollen chitosan/PVA blended hydrogel

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

membranes were mounted between the two half-cells of the donor cell and receptor cell. A solution with a specific model drug concentration was added to the donor cell, and fresh buffer solution was added to the receptor cell. The entire content of the receptor cell was removed at regular time intervals and replaced with fresh buffer solution. To ensure constant temperature of the solution, water with constant temperature was pumped through the outer half-cells. A UV-Vis light spectrophotometer (Ultrospec 1100 pro, Biochrom Ltd., Cambridge, UK) was used to measure the absorbance of the samples taken from the receptor half-cell. The solute concentration of each sample could be determined using a calibration curve derived from the absorbance of the known concentration of the solute. Creatinine, 5-FU, uric acid and vitamin B12 were used in the study. The permeability coefficients, P (cm/s), were determined [38] from the following equation:
 2Ct 2A ln 1 − = − Pt (1) C0 V where Ct is the solute concentration in the receptor cell at time t, C0 the initial solute concentration of the donor cell, V the volume of each half-cell, A the effective area of the membrane available for solute permeation. Linear regression was employed to calculate the permeability of solutes through the membrane.

5. Results and discussion 5.1. Characterization of chitosan/PVA blended hydrogel membranes The effect of formaldehyde in chemical structure of the chitosan membrane surface was investigated by ESCA (Fig. 1). The peaks at about 283, 285, 531, 398 and

41

Table 1 The percentage of C, O, –N–C, and –N=C Sample

C (%)

O (%)

–N–C (%)

–N=C (%)

Pure chitosan membrane Chitosan membrane treated with formaldehyde

79.10 76.19

17.99 21.77

2.49 1.83

0.13 0.16

406 eV indicated –C–H, –C–O, –O–C, –N–C and –N=C bonds in chitosan membrane surface, respectively. From Table 1, it was found that the oxygen atom and –N=C content increased whereas –N–C content decreased after chitosan treated with formaldehyde, which resulted from the crosslinking of formaldehyde with chitosan. It was confirmed from the results of FTIR spectrum (Fig. 2). The FTIR spectrum of pure chitosan membrane showed the absorption peaks at 1635 cm−1 (NHCOCH3 ) and at about 1559 cm−1 for the –NH2 group. Compared with the pure chitosan membrane (Fig. 2a) to the chitosan membrane treated with formaldehyde (Fig. 2b), the amount of –NH2 group on the membrane decreased, which resulted from the reaction between formaldehyde and –NH2 group, and the –N–C bond changed into –N=C bond. The FTIR spectrum of pure PVA membrane, (Fig. 2g) showed the absorption peaks at about 3256 cm−1 (–OH) and at about 1086 and 1415 cm−1 for the –C–O group. Fig. 2g and h illustrate the effect of formaldehyde on the chemical structure of the PVA membrane. A decrease in the absorption peaks at OH and C–O groups in PVA was found; whereas a strong absorption peak at 1007 cm−1 for the –C–O–C group was shown in Fig. 2h. The spectral change resulted from the disappearance of the hydroxyl groups and the formation of an acetal ring and ether linkage as a result of the reaction between the hydroxyl groups and formaldehyde [14]. Comparing Fig. 2a–h, the effect of relative content of PVA

(a)

Intensity(counts/sec

C

O N

(b)

O C N

0

200

400

600

800

1000

Binding Energy (eV) Fig. 1. ESCA spectrum of (a) pure chitosan and (b) pure chitosan with formaldehyde treatment.

42

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

Fig. 2. Fourier transfer infrared spectrum of various chitosan/PVA blended hydrogel membranes: (a) pure chitosan, (b) chitosan with formaldehyde treatment, (c) 80% chitosan with formaldehyde treatment, (d) 50% chitosan without formaldehyde treatment, (e) 50% chitosan with formaldehyde treatment, (f) 25% chitosan with formaldehyde treatment, (g) pure PVA without formaldehyde treatment, and (h) pure PVA with formaldehyde treatment.

on the chemical structure of the chitosan/PVA blended hydrogel membranes was found. With increasing the content of PVA in the blended hydrogel membranes, the absorption peak at 1635 cm−1 (NHCOCH3 ) and at about 1559 cm−1 for the –NH2 group decreased but the absorption peak at 1007 cm−1 for the –C–O–C group increased. DSC curves (first scan) of chitosan membranes were shown in Fig. 3a. There is an endothermic peak at 125 ◦ C. Following the first scan, the characteristic peak was erased in the second scan (not shown here). The presence of this peak results from the dissociation process of interchain hydrogen bonding of chitosan [4]. It is similar to the report of Beatrice and Mariastella [37], and this behavior has been related to the denaturation of order domains of protein. Compared

to the pure chitosan membrane, the effect of formaldehyde on the peak temperature was found in Fig. 3b. The peak temperature increased significantly from 125 to 214 ◦ C. A melting endothermic peak at 223 ◦ C was shown in Fig. 3e, which is associated with the crystalline polymer fraction of PVA. After treatment with formaldehyde, the temperature shifted to 229 ◦ C (Fig. 3f). The glass transition temperature of the amorphous PVA fraction increased significantly from 71 to 103 ◦ C (Fig. 4). Fig. 3c and d showed the DSC curve of the chitosan/PVA blended hydrogel membranes. The dissociation temperatures of chitosan were at 139 and 169 ◦ C for the membrane without and with the treatment of formaldehyde, respectively. The characteristic peak of crystalline polymer fraction of PVA is at about 218 ◦ C for

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

43

Endothermal

(a) (b) (c) (d) (e) (f)

-50

0

50

100

150

200

250

0

Temperature( C)

Fig. 3. DSC curves of various chitosan/PVA blended hydrogel membranes: (a) pure chitosan, (b) pure chitosan with formaldehyde treatment, (c) 50% chitosan without formaldehyde treatment, (d) 50% chitosan with formaldehyde treatment, (e) pure PVA without formaldehyde treatment, and (f) pure PVA with formaldehyde treatment.

both samples. Comparing the area of the endothermic peak to that of PVA membranes suggests that the PVA crystallization is decreased after blending with chitosan. Storage modulus is a measure of the stiffness (rigidity) of the material. Fig. 5 shows the plots of storage modulus (E ) versus scan temperature for various samples. Chi-

Endothermal

a

b

20

40

60

80

100

120

Temperature( 0 C)

Fig. 4. The glass transition temperature of (a) pure PVA without formaldehyde treatment and (b) pure PVA with formaldehyde treatment.

tosan has a flat modulus response in the test temperature range (Fig. 5a). Formaldehyde has no significant effect on E (Fig. 5b). The change in E is relatively small for chitosan with formaldehyde. When temperature is higher than 50 ◦ C, E decreases for the pure PVA (Fig. 5e). The effect of formaldehyde was observed: Note that E drops as the specimen of PVA with formaldehyde pass through the glass transition, about 100 ◦ C, where they exit the glassy phase and enter the rubbery phase (Fig. 5f). Compared to chitosan, PVA has low storage modulus when the temperature is higher than 100 ◦ C. The stiffness of chitosan is due to the existence of the interchain hydrogen bonding within chitosan. From Fig. 5c and d, it is found that the stiffness of chitosan/PVA blend was dominated by the existence of chitosan. When temperature is higher than 70 ◦ C, E decreases for the chitosan/PVA blend without formaldehyde (Fig. 5c). The enhancement of stiffness by formaldehyde was also found in Fig. 5d. When temperature is higher than 120 ◦ C, E decreases for the chitosan/PVA blend with formaldehyde (Fig. 5d). Compared to the chitosan/PVA blend without formaldehyde, the storage modulus is higher for the chitosan/PVA blend with formaldehyde. tan δ is a damping term defined as the ratio of energy dissipated as heat to the maximum energy stored in the material. It is an index of material viscoelasticity. Fig. 6 shows the plots of tan δ versus scan temperature for various samples. A significant damping peak at 110 ◦ C was found for PVA with formaldehyde (Fig. 6f), and regards as glass

44

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

10000 (a) (b) (c) (d) (e) (f)

Storagege Modulus(Mpa)

1000

100

10

1

0

50

100

150

200

0

Temperature( C) Fig. 5. Plot of storage modulus vs. temperature for (a) pure chitosan with formaldehyde treatment, (b) pure chitosan, (c) 50% chitosan without formaldehyde treatment, (d) 50% chitosan with formaldehyde treatment, (e) pure PVA without formaldehyde treatment, and (f) pure PVA with formaldehyde treatment.

transition temperature. But there is no significant damping peak for pure PVA (Fig. 6e). And the value of tan δ increases sharply after about 148 ◦ C. As shown in our previous study, the broad and decrease of damping peak can be described as the incompatibility within the material [39]. The results of Fig. 6e and f can be described as follows. As pure PVA

is a crystalline polymer, the incompatibility between the amorphous phase and crystalline area results in the broader damping for the pure PVA (Fig. 6e). After treated with formaldehyde, the crystalline polymer fraction in PVA decreases and the separation between the amorphous phase and crystalline area decreases and results in the increase of

0.25 (a) (b) (c) (d) (e) (f)

Tan Delta

0.2

0.15

0.1

0.05

0

0

50

100

150

200

0

Temperature( C) Fig. 6. Plot of damping term vs. temperature for (a) pure chitosan with formaldehyde treatment, (b) pure chitosan, (c) 50% chitosan without formaldehyde treatment, (d) 50% chitosan with formaldehyde treatment, (e) pure PVA without formaldehyde treatment, and (f) pure PVA with formaldehyde treatment.

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51 120 (a) (b) (c) (d) (e) (f) (g) (h)

100

80 Weight(%)

the damping peak (Fig. 6f). The results can be confirmed from the storage modulus (Fig. 5e and f). When the temperature is lower than 50 ◦ C, PVA is in the glassy state. The values of storage seem the same for PVA with and without formaldehyde treatment. When the temperature is higher than 100 ◦ C, the values of storage modulus are higher for the pure PVA (Fig. 5e) than those of PVA treated with formaldehyde (Fig. 5f). Although formaldehyde works as crosslinking agent and enhances the storage modulus in the temperature between 50 and 100 ◦ C, it destroys the crystalline area of PVA and results in the decrease of storage modulus after temperature is higher than 100 ◦ C. Because tan δ is the measure of the ratio of energy dissipated as heat to the maximum energy stored in the material, more energy is stored in the material at lower values of tan δ. From Fig. 6a and b, no significant damping peak was found for chitosan. The value of tan δ increases smoothly in the test temperature range. No glass transition temperature exists in chitosan. Compared to PVA, it shows that more energy is stored in chitosan than in PVA and the property of viscoelasticity for PVA is more significant than that of chitosan. No damping peak exists for chitosan/PVA blended hydrogel membrane without formaldehyde treatment (Fig. 6c). Significant increase of the value of tan δ was found at about 120 ◦ C and then leveled off after about 160 ◦ C. When the temperature is higher than 150 ◦ C, the value of tan δ seems the same for the pure PVA and PVA/chitosan blended hydrogel membranes without formaldehyde treatment (Fig. 6c and e). When temperature is lower than 150 ◦ C, the value of tan δ for the pure PVA (Fig. 6e) is higher than that of PVA/chitosan blended hydrogel membranes without formaldehyde treatment (Fig. 6c). It means that the viscoelasticity is dominated by chitosan before 120 ◦ C. In the temperature range between 120 and 150 ◦ C, the part of amorphous PVA changes from glassy state to rubbery state and the dissociation process of interchain hydrogen bonding in the part of chitosan occurs. Due to the disappearance of the interchain hydrogen bonding within the chitosan, the viscoelasticity of the chitosan/PVA blended hydrogel after 150 ◦ C is dominated by the part of PVA. The effect of formaldehyde on the value of tan δ was found in Fig. 6d. The values of tan δ are lower for the chitosan/PVA blended hydrogel with formaldehyde treatment (Fig. 6d) than those of the chitosan/PVA blended hydrogel without formaldehyde treatment (Fig. 6c). Significant increase of the value of tan δ was found at about 110 ◦ C and then leveled off at about 150 ◦ C for chitosan/PVA hydrogel membrane treated with formaldehyde. The shift of temperature from 120 ◦ C (Fig. 6c) to 110 ◦ C (Fig. 6d) is due to that the crystalline area was decreased when the PVA was treated with formaldehyde. The representative TGA curves for the chitosan/PVA blended hydrogel membranes were shown in Fig. 7. The initial decomposition temperature of chitosan/PVA blended hydrogel membranes was at about 288 ± 5 ◦ C, whereas the

45

60

40

20

0

0

100

200

300

400

500

600

700

800

900

0

Temperature( C)

Fig. 7. TGA curves of various chitosan/PVA blended hydrogel membranes: (a) pure chitosan, (b) pure chitosan with formaldehyde treatment, (c) 80% chitosan treated with formaldehyde, (d) 50% chitosan without formaldehyde treatment, (e) 50% chitosan with formaldehyde treatment, (f) 25% chitosan with formaldehyde treatment, (g) pure PVA without formaldehyde treatment, and (h) pure PVA with formaldehyde treatment.

initial decomposition was at about 260 ◦ C for PVA membrane. Although there was no significant effect of formaldehyde on initial decomposition temperature, the maximum decomposition temperature of PVA shifted significantly from about 300 ◦ C to about 400 ◦ C after the membrane was treated with formaldehyde. The maximum decomposition temperatures of chitosan/PVA blended hydrogel membranes with formaldehyde treatment are higher than those membranes without formaldehyde treatment. At temperatures higher than 520 ◦ C, the TGA curves level off. The wt.% loss decreased with increasing the chitosan content in the blended hydrogel membranes. Compared to the membrane without formaldehyde treatment, the wt.% loss was lower for the membranes with formaldehyde treatment. From the results of Fig. 7 it can be concluded that the thermal stability of blended hydrogel membranes increases with chitosan content and the treatment of formaldehyde. 5.2. Properties of chitosan/PVA blended hydrogel membranes Linear relationship to chitosan content for water content and vapor transmission rates in the chitosan/PVA blended hydrogel membranes were found in Fig. 8. Both water content and vapor transmission rates increased with increasing chitosan content in the chitosan/PVA blended hydrogel membranes. As described in the previous study [30], PVA is a water-soluble polymer and the blending of chitosan with PVA tends to increase the water uptake by PVA content. The results are opposite to our study. It is due to the effect of formaldehyde. In the previous study [30], the chitosan/PVA

46

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51 300

(Fig. 7). As the effect of formaldehyde, the lower water content and water vapor transmission rate on PAV membrane than those on chitosan membrane were found in this study. The viable cell number of aurococcus after coming into contact with various chitosan/PVA blended hydrogel membranes were evaluated. It appears that the antibacterial activity of all chitosan/PVA blended hydrogel membranes is similar. The viable cell number of aurococcus on the various chitosan/PVA blended hydrogel membranes was about (2.5 ± 0.5) × 107 cells/ml. Although increasing the chitosan content of the chitosan-containing modified nonwoven fabric resulted in the decrease of the viable cell number that was found in our previous study [40], there is no significant effect of chitosan content on the antibacterial activity in this study. From our referring data of the antibacterial activity, the viable cell number of Staphylococcus aureus on the pure chitosan membrane was about 1.6 × 105 cells/ml at beginning. Then the viable cell number decreases to 3.2 × 103 cells/ml after 18 h. It means that chitosan is an antibacterial material. As the existence of formaldehyde and PVA, the antibacterial ability of chitosan became less in the chitosan/PVA blended hydrogel membranes. The permeability coefficient of various solutes, such as creatinine, 5-FU, uric acid and vitamin B12 through chitosan/PVA blended hydrogel membranes, as function of time, was determined from the slope of the straight line obtained by plotting −(V/2A) ln[1 − 2(Ct /C0 )] versus time (Figs. 9–12). Higher permeability was observed for the blended hydrogel membranes with higher chitosan content.

6 5

Water content (%)

2

4

Water Vapor Perneation (kg/m /day)

250

200 3 2

150

1 100 0 50 -1 0

0

20

40

60

80

100

-2

Chitosan (%)

Fig. 8. (䊏) Water content and (䉬) water vapor transmission rate through various chitosan/PVA blended hydrogel membranes.

blended membranes were prepared without formaldehyde treatment, whereas the chitosan/PVA blended hydrogel membranes were treated with formaldehyde in this study. As shown in the discussion about the effect of formaldehyde on DSC and TGA, the glass transition temperature of the amorphous PVA fraction increases significantly from 71 to 103 ◦ C (Fig. 4) and the maximum decomposition temperature of PVA shifted significantly from about 300 to about 400 ◦ C after the membrane was treated with formaldehyde 3.0 2.8

20% 40% 60% 80% 100%

2.6 2.4 2.2

-(V/2A)*ln(1-2Ct /C0)

2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

2000

4000

6000

8000

10000

12000

14000

Time (sec)

Fig. 9. Permeation of creatinine through various chitosan/PVA blended hydrogel membranes with (䊏) 20, (䊉) 40, (䉱) 60, (䉲) 80 and (䉬) 100% chitosan in the membrane.

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

47

3.2 3.0 2.8

20% 40% 60% 80% 100%

2.6

-(V/2A)*ln(1-2Ct /C0)

2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

2000

4000

6000

8000

10000

12000

14000

16000

Time (sec)

Fig. 10. Permeation of 5-FU through various chitosan/PVA blended hydrogel membranes with (䊏) 20, (䊉) 40, (䉱) 60, (䉲) 80 and (䉬) 100% chitosan in the membrane. 0.32 0.30

20% 40% 60% 80% 100%

0.28 0.26 0.24

-(V/2A)*ln(1-2Ct /C0)

0.22 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 0

2000

4000

6000

8000

10000

12000

14000

Time (sec)

Fig. 11. Permeation of vitamin B12 through various chitosan/PVA blended hydrogel membranes with (䊏) 20, (䊉) 40, (䉱) 60, (䉲) 80 and (䉬) 100% chitosan in the membrane.

From the slope of Figs. 9–12 and the results of Table 2, the values of permeability were calculated and shown in Table 3. The relationship between the permeability and chitosan content in the blended hydrogel membranes were shown in

Fig. 13. From Fig. 13, the linear relationship between the permeability of solute (except uric acid) through the hydrogel membrane, P (cm/s), and the wt.% of chitosan in the membrane, X, is apparent. The results of linear regression are given in Table 4. For each blended hydrogel membrane,

48

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51 0.55

20% 40% 60% 80% 100%

0.50 0.45

-(V/2A)*ln(1-2Ct/C0)

0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0

2000

4000

6000

8000

10000

12000

14000

Time (sec)

Fig. 12. Permeation of uric acid through various chitosan/PVA blended hydrogel membranes with (䊏) 20, (䊉) 40, (䉱) 60, (䉲) 80 and (䉬) 100% chitosan in the membrane. Table 2 Regression results of −(V/2A) ln[1 − 2(Ct /C0 )] versus time (s) for different solute through various chitosan/PVA membranes Solute

Chitosan content (%)

Formula

Creatinine

20 40 60 80 100

Y Y Y Y Y

5-FU

20 40 60 80 100 20 40 60 80 100 20 40 60 80 100

Vitamin B12

Uric acid

R

N

P

= 1.0653 × 10−4 X = 1.3500 × 10−4 X = 1.5080 × 10−4 X = 1.7806 × 10−4 X = 1.99988 × 10−4 X

0.99918 0.99889 0.99769 0.99653 0.99376

8 8 8 8 8

<0.0001 <0.0001 <0.0001 <0.0001 <0.0001

Y Y Y Y Y Y Y Y Y Y

= 9.48336 × 10−5 X = 1.1582 × 10−4 X = 1.43572 × 10−4 X = 1.71706 × 10−4 X = 2.02715 × 10−4 X = 1.48081 × 10−5 X = 1.60595 × 10−5 X = 1.85214 × 10−5 X = 2.05638 × 10−5 X = 2.29033 × 10−5 X

0.99986 0.995 0.99709 0.99693 0.99882 0.99986 0.99991 0.99979 0.99997 0.99996

9 9 9 9 9 8 8 8 8 8

<0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001

Y Y Y Y Y

= 9.24791 × 10−7 X = 1.25526 × 10−6 X = 5.9323 × 10−7 X = 3.43855 × 10−5 X = 3.90628 × 10−5 X

0.99599 0.99758 0.99003 0.99952 0.99908

8 8 8 8 8

<0.0001 <0.0001 <0.0001 <0.0001 <0.0001

the order of the permeability is creatinine (FW = 113.1) > 5-FU (FW = 130.1) > vitamin B12 (FW = 1355.4). As mentioned in an earlier study [30], vitamin B12 transport through chitosan/PVA blend can be considered as pore mechanism. It means that permeation of solute in the pore model is expected to occur primarily via the bulk-like water within the hydrogel. As shown in Fig. 8, water content in-

creased linearly with chitosan content in the chitosan/PVA blended hydrogel membranes. Therefore, the permeability of solutes through the chitosan/PVA hydrogel membranes can be explained by water content which is based on the free volume theory of diffusion [41]. By comparing the permeability of creatinine and 5-FU with that of vitamin B12 , the effect of chitosan content in the blended hydrogel

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51 Table 3 Permeability, P (×105 cm/s), of different solute through various chitosan/PVA membrane Samples with various wt.% of chitosan in membrane

Creatinine 5-FU Vitamin B12 Uric acid

20

40

60

80

100

10.653 9.483 1.481 0.092

13.500 11.582 1.605 0.125

15.080 14.357 1.852 0.059

17.806 17.170 2.056 3.439

19.999 20.271 2.290 3.906

Table 4 Linear regression of permeability coefficient (P) versus chitosan content (X) Solute

Creatinine 5-FU Vitamin B12

P (×10−5 cm/s) = b + mX b ± S.D.

m ± S.D.

8.51 ± 0.33 6.42 ± 0.34 1.24 ± 0.04

11.50 ± 0.50 13.58 ± 0.52 1.03 ± 0.06

R2

0.9944 0.9956 0.9911

membranes on permeability is more significant for solute with low molecular weight (creatinine and 5-FU) than the solute with high molecular weight (vitamin B12 ). In general, the crystallinity of PVA can affect the permeability of solutes through the chitosan/PVA blended hydrogel membranes. In this study, the chitosan/PVA blended hydrogel membranes were treated with formaldehyde. From the study of DSC and dynamic mechanical analysis (Figs. 3–6), the crystallinity in the chitosan/PVA blended hydrogel membranes was decreased by formaldehyde treatment. Thus the effect of crystallinity on the permeability of

49

solutes through the chitosan/PVA blended hydrogel membrane was decreased. When the content of chitosan in the chitosan/PVA blended hydrogel membrane increased, the effect of crystallinity of PVA in the permeability became less. From Table 4, the permeability of solute through the chitosan/PVA hydrogel membrane depends linearly with the chitosan content. Uric acid is an anionic molecule and chitosan is a cationic polysaccharide, thus electrostatic attraction occurs when the permeation of uric acid through the chitosan/PVA blended hydrogel membrane. An intriguing result of uric acid through the chitosan/PVA blended hydrogel membranes was found. When the chitosan content was between 20 and 60% in the chitosan/PVA blended hydrogel membranes, the permeability of uric acid through the membranes was about 10−6 cm/s. There was a lowest permeability at about 5.9 × 10−7 cm/s for the chitosan/PVA membrane at 60% chitosan content. However, these values are within experimental error. But the permeability of uric acid through the chitosan/PVA blended hydrogel membranes with 80 and 100% content of chitosan is at about 3.5 × 10−5 cm/s. As mentioned in a previous study [42], the attraction between anionic solute and cationic membrane made it difficult for the solute to leave the present position and to move the next position in the membrane, whereas it offered more chances to find the next position in the membrane. The experiment result of uric acid suggests that the former effect is predominant for the chitosan/PVA blended hydrogel membranes with 20, 40 and 60% content of chitosan, whereas the latter effect is predominant for the chitosan/PVA blended hydrogel membrane with 80 and 100% content of chitosan.

0.00022

5-FU creatinine vitamin B12

0.00020 0.00018

permeability cofficient, P (cm/sec)

uric acid 0.00016 0.00014 0.00012 0.00010 0.00008 0.00006 0.00004 0.00002 0.00000 0

20

40

60

80

100

Weight percent of chitosan in chitosan/PVA blended membrane (%)

Fig. 13. Permeability of (䊏) 5-FU, (䊉) creatinine, (䉱) uric acid and (䉲) vitamin B12 through various chitosan/PVA blended hydrogel membranes.

50

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51

6. Conclusion The crystallinity of PVA decreases with the treatment of formaldehyde. Chitosan/PVA blended hydrogel membranes prepared and treated with formaldehyde in this study are not very compatible. The values of water content, water vapor transmission and permeability of solutes such as creatinine, 5-FU and vitamin B12 through chitosan/PVA blended hydrogel membranes increase linearly with chitosan content in the blended hydrogel membranes, whereas there is a sharp change of permeability of uric acid through the chitosan/PVA blended hydrogel membrane when the chitosan content is changed from 60 to 80% in the blended hydrogel membrane. As PVA exhibits the properties of minimal cell adhesion and protein absorption [23] and the similar antibacterial activity of all chitosan/PVA blended hydrogel membranes in this study, the application of chitosan/PVA blended hydrogel membranes for different application such as wound dressing, coating for nanoparticle for drug control release and haemodialysis will be evaluated in the future. As the thermostability of the chitosan/PVA blended hydrogel membrane is enhanced by treating with formaldehyde and the electrostatic attraction occurs between the basic chitosan and anionic solutes, the application of chitosan/PVA blended hydrogel membrane for bioseparation will also be studied in our future research.

Acknowledgements This work was supported by National Science Council of the Republic of China under Grant NSC 91-2216-E-182-002 and partial financial support of Chang Gung Memorial Hospital.

References [1] M.M. Amiji, Permeability and blood compatibility properties of chitosan-poly(ethyleneoxide) blend membranes for haemodialysis, Biomaterials 16 (1995) 593–599. [2] M.G. Cascone, B. Sim, S. Downes, Blends of synthetic and natural polymers as drug delivery systems for growth hormone, Biomaterials 16 (1995) 569–574. [3] T. Koyano, N. Koshizaki, H. Umehara, M. Nagura, N. Minoura, Surface states of PVA/chitosan blended hydrogels, Polymer 41 (2000) 4461–4465. [4] W.Y. Chuang, T.H. Young, C.H. Yao, W.Y. Chiu, Properties of the poly(vinyl alcohol)/chitosan blend and its effect on the culture of fibroblast in vitro, Biomaterials 20 (1999) 1479–1487. [5] T. Chandy, C.P. Sharma, Prostaglandin E1 -immobilized poly(vinyl alcohol)-blended chitosan membranes: blood compatibility and permeability properties, J. Appl. Polym. Sci. 44 (1992) 2145–2156. [6] J.M. Yang, C.P. Chang Chian, K.Y. Hsu, Oxygen permeation in SBS-g-DMAEMA copolymer membrane prepared by UV photografting without degassing, J. Membr. Sci. 153 (1999) 175–182. [7] J.M. Yang, M.J. Huang, T.S. Yeh, Preparation of poly(acrylic acid) modified polyurethane membrane for biomaterial by UV radiation without degassing, J. Biomed. Mater. Res. 45 (1999) 133–139.

[8] J.M. Yang, M.C. Wang, Y.G. Hsu, C.H. Chang, S.K. Lo, Preparation of heparin containing SBS-g-VP copolymer membrane for biomaterial usage, J. Membr. Sci. 138 (1998) 19–27. [9] J.M. Yang, Y.J. Jong, K.Y. Hsu, C.H. Chang, Preparation and characterization of heparin containing SBS-g-DMAEMA copolymer membrane, J. Biomed. Mater. Res. 39 (1998) 86–91. [10] J.M. Yang, Y.J. Jong, K.Y. Hsu, Preparation and properties of SBS-g-DMAEMA copolymer membrane by ultraviolet radiation, J. Biomed. Mater. Res. 35 (1997) 175–180. [11] C. Peniche, W. Arguelles-Monal, N. Davidenko, R. Sastre, A. Gallardo, J.S. Roman, Self-curing membranes of chitosan/PAA IPNs obtained by radical polymerization: preparation, characterization and interpolymer complexation, Biomaterials 20 (1999) 1869–1878. [12] P. Gong, L. Zhang, L. Zhuang, J. Lu, Synthesis and characterization of polyurethane-chitosan interpenetrating polymer networks, J. Appl. Polym. Sci. 68 (1998) 1321–1329. [13] V.B. Kushwaha, Permeation of molecules through different polymeric membranes, J. Appl. Polym. Sci. 74 (1999) 3469–3472. [14] C.K. Yeom, K.H. Lee, Pervaporation separation of water–acetic acid mixtures through poly(vinyl alcohol) membranes crosslinked with glutaraldehyde, J. Membr. Sci. 109 (1996) 257–265. [15] J. Ge, Y. Cui, Y. Yan, W. Jiang, The effect of structure on pervaporation of chitosan membrane, J. Membr. Sci. 165 (2000) 75–81. [16] D. Knorr, Dye binding properties of chitin and chitosan, J. Food Sci. 48 (1983) 36–41. [17] D.K. Kweon, S.B. Song, Y.Y. Park, Preparation of water-soluble chitosan/heparin complex and its application as wound healing accelerator, Biomaterials 24 (2003) 1595–1601. [18] Y. Hu, X. Jiang, Y. Ding, H. Ge, Y. Yuan, C. Yang, Synthesis and characterization of chitosan-poly(acrylic acid) nanoparticles, Biomaterials 23 (2002) 3193–3201. [19] M. Ishihara, K. Nakanishi, K. Ono, M. Sato, M. Kikuchi, Y. Saito, H. Yura, T. Matsui, H. Hattori, M. Uenoyama, A. Kurita, Photocrosslinkable chitosan as dressing for wound occlusion and accelerator in healing process, Biomaterials 23 (2002) 833–840. [20] X.Y. Shi, T.W. Tan, Preparation of chitosan/ethylcellulose complex microcapsule and its application in controlled release of vitamin D2 , Biomaterials 23 (2002) 4469–4473. [21] S.J.K. Francis, H.W.T. Matthew, Application of chitosan-based polysaccharide biomaterials in cartilage tissue engineering: a review, Biomaterials 21 (2000) 2589–2598. [22] A. Amanda, A. Kulprathipanja, M. Toennesen, S.K. Mallapragada, Semicrystalline poly(vinyl alcohol) ultrafiltration membranes for bioseparations, J. Membr. Sci. 176 (2000) 87–95. [23] L.F. Gudeman, N.A. Peppas, pH-sensitive membranes from poly(vinyl alcohol)/poly(acrylic acid) interpenetrating networks, J. Membr. Sci. 107 (1995) 239–248. [24] A.S. Hickey, N.A. Peppas, Mesh size and diffusive characteristics of semicrystalline poly(vinyl alcohol) membranes prepared by freezing/thawing techniques, J. Membr. Sci. 107 (1995) 229–237. [25] H. Matsuyama, M. Teramoto, H. Urano, Analysis of solute diffusion in poly(vinyl alcohol) hydrogel membrane, J. Membr. Sci. 126 (1997) 151–160. [26] K. Burczak, E. Gamian, A. Kochman, Long-term in vivo performance and biocompatibility of poly(vinyl alcohol) hydrogel macrocapsules for hybrid-type artificial pancreas, Biomaterials 17 (1996) 2351– 2356. [27] T.H. Yang, N.K. Yao, R.F. Chang, L.W. Chen, Evaluation of asymmetric poly(vinyl alcohol) membranes for use in artificial islets, Biomaterials 17 (1996) 2139–2145. [28] T.H. Yang, W.Y. Chuang, N.K. Yao, L.W. Chen, Use of a diffusion model for assessing the performance of poly(vinyl alcohol) bioartificial pancreases, J. Biomed. Mater. Res. 40 (1998) 385–391. [29] W. Paul, C.P. Sharma, Acetylsalicylic acid loaded poly(vinyl alcohol) hemodialysis membranes: effect of drug release on blood compatibility and permeability, J. Biomed. Sci. Polym. Ed. 8 (1997) 755– 764.

J.M. Yang et al. / Journal of Membrane Science 236 (2004) 39–51 [30] S. Nakatsuka, A.L. Andrady, Permeability of vitamin B-12 in chitosan membranes. Effect of crosslinking and blending with poly(vinyl alcohol) on permeability, J. Appl. Polym. Sci. 44 (1992) 17–28. [31] N. Minoura, T. Koyano, T. Koyano, N. Koshizaki, H. Umehara, M. Nagura, K. Kobayashi, Preparation, properties, and cell attachment/growth behavior of PVA/chitosan-blended hydrogels, Mater. Sci. Eng. C 6 (1998) 275–280. [32] H.S. Blair, J. Guthrie, T.K. Law, P. Turkington, Chitosan and modified chitosan membranes. I. Preparation and characterization, J. Appl. Polym. Sci. 33 (1987) 641–656. [33] A. Rubinstein, Approaches and opportunities in colon-specific drug delivery, Crit. Rev. Ther. Drug Carrier Syst. 12 (1995) 101–149. [34] A.R. Gennaro, G.D. Chase, D.A. Marderosian, S.C. Harvey, D.A. Hussar, T. Medwick, E.G. Rippie, J.B. Schwartz, E.A. Swinyard, G.L. Zink (Eds.), Remingtonis Pharmaceutical Sciences, vol. 1151, Mack Printing Company, PA, 1990. [35] M.T. Qureshi, H.S. Blair, S.J. Allen, Studies on modified chitosan membranes. II. Dialysis of low molecular weight metabolites, J. Appl. Polym. Sci. 46 (1992) 263–269. [36] L.R. Cardona, Y.D. Sanzgiri, L.M. Benedetti, V.J. Stella, E.M. Topp, Application of benzyl hyaluronate membranes as potential wound

[37] [38]

[39]

[40]

[41]

[42]

51

dressing: evaluation of water vapor and gas permeabilities, Biomaterials 17 (1996) 1639–1643. S. Beatrice, S. Mariastella, Viscoelastic and thermal properties of collagen/poly(vinyl alcohol) blends, Biomaterials 16 (1995) 785–792. J. Zhang, N.A. Peppas, Synthesis and characterization of pHand temperature-sensitive poly(methacrylic acid)/poly(N-isopropylacrylamide) interpenetrating polymeric networks, Macromolecules 33 (2000) 102–107. J.M. Yang, H.M. Li, M.C. Yang, C.H. Shih, Characterization of acrylic bone cement using dynamic mechanical analysis, J. Biomed Mater. Res. (Appl. Biomater.) 48 (1999) 52–60. J.M. Yang, H.T. Lin, T.H. Wu, C.C. Chen, Wettability and antibacterial assessment of chitosan containing radiation-induced graft nonwoven fabric of polypropylene-g-acrylic acid, J. Appl. Polym. Sci. 90 (2003) 1331–1336. H. Yasuda, L.D. Ikenberry, C.E. Lamaze, Permeability of solutes through hydrated polymer membranes. Part II. Permeability of water soluble organic solutes, Makromol. Chem. 125 (1969) 108–118. H. Matsuyama, Y. Kitamura, Y. Naramura, Diffusive permeability of ionic solutes in charged chitosan membrane, J. Appl. Polym. Sci. 72 (1999) 397–404.