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Controlled release of ketoprofen from electrospun poly(vinyl alcohol) nanofibers
Materials Science and Engineering A 459 (2007) 390–396
Controlled release of ketoprofen from electrospun poly(vinyl alcohol) nanofibers El-Refaie Kenawy a,∗ , Fouad I. Abdel-Hay a , Mohamed H. El-Newehy a,b , Gary E. Wnek b,c a
Chemistry Department, Polymer Research Group, Faculty of Science, Tanta University, Tanta 31527, Egypt b Department of Chemical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA c Department of Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106-7217, USA Received 16 November 2006; received in revised form 28 December 2006; accepted 11 January 2007
Abstract Poly(vinyl alcohol) (PVA) as a biodegradable hydrophilic polymer has unique properties. It absorbs water and swells easily, but the swelling is inhibited by salts. Its physico-chemical properties depend on the degree of hydrolysis. The solubility of PVA in water increases greatly as its degree of hydrolysis increases. In the current work, new systems for the delivery of ketoprofen as non-steroidal anti-inflammatory drug (NSAID) were developed. New electrospun fibers containing ketoprofen and made from partially and fully hydrolyzed poly(vinyl alcohol) (PVA) were developed as drug delivery system. Moreover, electrospun PVA fibers were stabilized against disintegration in water by treatment with alcohol such as methanol. The release of ketoprofen from the electrospun fibers was determined by UV spectrophotometer at the body temperature (37 ◦ C) and at the room temperature (20 ◦ C). The results showed that upon the treatment of electrospun PVA with alcohol, the burst release was eliminated. © 2007 Elsevier B.V. All rights reserved. Keywords: Electrospinning; Poly(vinyl alcohol); Controlled-release; Ketoprofen; Anti-inflammatory drug
1. Introduction Poly(vinyl alcohol) (PVA) is a hydrophilic polymer, has unique properties. It absorbs water and swells easily, but the swelling is inhibited by salts [1,2]. Its physico-chemical properties depend on the degree of hydrolysis [3,4]. The solubility of PVA in water increases greatly as its degree of hydrolysis increases [5]. Moreover, PVA can be used for releasing biological and medical materials in a controlled way [6]. PVA was used in some modern technologies, such as hydrogels, polyelectrolytes, optics, and biomaterials [7] including soft contact lenses [8], implants [9], and artificial organs [10]. This is due to their inherent non-toxicity, non-carcinogenicity, good biocompatibility, and high degree of swelling in aqueous solutions. The PVA hydrogels were used as drug delivery matrices [11–14] or in the form of powders added to mixtures of other excipients for tablet formation [15].
∗
Corresponding author. E-mail address: [email protected] (E.-R. Kenawy).
0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.01.039
Generally, polymer-based drug delivery systems are used to optimize the therapeutic properties of drugs and to render them safer, effective and reliable [16]. Non-steroidal antiinflammatory drugs (NSAIDs) are used for controlling pain and inflammation in rheumatic diseases. Administration of acidic NSAIDs to arthritic patients relieves pain and inflammatory swelling [17]. Ketoprofen, our drug model, is one of NSAIDs group. It is effective as anti-inflammatory agent in humans with flogistic diseases. The major side effects involve gastrointestinal symptoms. Due to the many advantages of the PVA, much attention has been focused on the electrospinning of PVA for applications in different fields such as biosensor [18], antimicrobial fibers [19–21], composites [22,23], macroporus and nanoporous films and membranes [24–26], and filtration applications [27]. Our laboratories have been especially interested in the electrospinning of poly(vinyl alcohol) (PVA) because it is an inexpensive biocompatible material. Electrospinning is an inexpensive method that produces polymer fibers with diameter in the range of nano- to a few microns using electrically driven jet of polymer solution or melt. The fibers are driven by charging a liquid typically to 5–30 kV versus ground at short distance
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away, which leads to charge injection into the liquid from the electrode. As the solvent of the polymer jet evaporates, the jet solidifies and a polymer fiber is formed. Electrospinning with research interests usually focusing on the theoretical foundation of the electrospinning process, including fiber initiation, jet instability and the structure and morphology of the electrospun fiber [28]. Recently, electrospinning includes a variety of applications including carbonaceous materials, tissue engineering scaffolds [29–32], separation filters, wound dressing materials, controlled-drug delivery platforms [33], and sensors [34–36]. In the current work, new systems of controlled drug release via electrospinning technique were developed. Electrospinning of partially and fully hydrolyzed PVA was carried out. Moreover, PVA was stabilized against disintegration in water and their visual mechanical property was increased by treatment with alcohol (not measured). The PVA electrospun fibers were used as controlled-release system for ketoprofen and were compared with casting films with the same composition. 2. Experimental 2.1. General experimental procedure 2.1.1. Materials Poly(vinyl alcohol) (PVA) (99+% hydrolyzed) (average Mw 85–146 kg/mol), poly(vinyl alcohol) (PVA) (87–89% hydrolyzed) (average Mw 124–186 kg/mol), methanol, sodium phosphate dibasic (Na2 HPO4 ) and potassium phosphate monobasic (KH2 PO4 ) were purchased from Aldrich (USA). Triton® X-100 was purchased from Sigma–Aldrich Corp. St. Louis, MO, USA. Ketoprofen was purchased from Sigma (USA). All materials were used as received without further purification. 2.1.2. Instruments Microscopy: Scanning electron microscope (SEM) was used to study the morphology of a dried mats and were performed on a JSM-820 scanning electron microscope (JEOL Ltd., USA). Precision micrometer: The thickness of electrospun mats and films was measured using PRECISION MICROMETER, Model No. 49–61, Range 0–1.270 mm, Testing Machines INC. AMITVILLE N.Y. (USA). Spectroscopy: UV spectra were recorded using GENESYSTM 6 Spectrophotometer (USA). 2.1.3. Preparation of phosphate buffer solution (PB) The phosphate buffer solution (pH 9.0) was prepared by dissolving sodium phosphate dibasic (Na2 HPO4 ) (35.49 g) in 1 L deionized water and the pH was adjusted to 9.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The phosphate buffer solution (pH 7.4) was prepared by dissolving sodium phosphate dibasic (Na2 HPO4 ) (21.70 g) and potassium phosphate monobasic (KH2 PO4 ) (2.60 g) in 1 L deionized water and the pH was adjusted to 7.4 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The pH 2.0 buffer solu-
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tions were adjusted with 0.1N hydrochloric acid and the pH was adjusted to 2.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. 2.2. Electrospinning Electrospinning apparatus: The setup of our electrospinning apparatus consists of a syringe with a flat-end metal needle cut, a syringe pump (model 100 KD scientific Inc., New Hope, PA) for controlled feeding rates, a grounded cylindrical stainless steel mandrel, and a high voltage dc power supply (Spellman, CZE1000R, Spellman High voltage Electronics Corp., Hauppauge, NY). 2.2.1. Preparation of polymer solution and fiber aggregates 2.2.1.1. Fully hydrolyzed poly(vinyl alcohol). Fully hydrolyzed poly(vinyl alcohol) was dissolved in deionized water on heating at 90 ◦ C for 6 h with vigorous stirring to obtain a concentration of 10 wt% solution. Then, the PVA solution was cooled to room temperature. Triton X-100 in concentration of 2.50% (w/w) PVA was added. The mixture was stirred for further 1 h. Ketoprofen in concentration of 5% (w/w) PVA was dissolved in a small amount of methanol and was added to the mixture of PVA/Triton X-100 and stirred for 20–30 min before electrospinning. 2.2.1.2. Partially hydrolyzed poly(vinyl alcohol). Partially hydrolyzed poly(vinyl alcohol) solution was prepared by dissolving PVA in deionized water at room temperature overnight with vigorous stirring to obtain a concentration of 10 wt% solution. Ketoprofen in concentration of 5% (w/w) PVA was dissolved in a small amount of methanol and was added to PVA solution and was stirred for 20–30 min before electrospinning. 2.2.2. General procedure for electrospinning process For the electrospun microfiber fabrics, a series of PVA solutions was prepared by dissolving the polymers in water at a concentration of 10 wt% and various concentrations of the drug was added as described earlier. The polymer solution was delivered at a constant flow rate (10 ml/h) using a syringe pump to the stainless steel blunt-ended needle with an air gap between the metal collector and the needle tip of 15 cm at a driving voltage of 20 kV (Table 1). The electrospun mats was dried in hood at room temperature overnight. For the purpose of comparison, casting film was made onto Petri dish. Table 1 Summary of electrospinning parameters applied for electrospinning of fully and partially hydrolyzed poly(vinyl alcohol) Sample code
Applied voltage (kV)
Feeding rate (mL/h)
TCDa (cm)
Polarity
PVA (99%) PVA (87–89%)
20 20
1.5 0.5
15 15
+ve +ve
a
Tip-to-collector distance.
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2.2.3. Stabilization of electrospun poly(vinyl alcohol) fibers containing ketoprofen The electrospun mats of fully and partially hydrolyzed PVA, were treated with alcohol such as methanol for periods of 1 and 24 h and were then dried overnight in the hood at room temperature. For the purpose of comparison, casting film was also treated with alcohol in the same way as for electrospun fibers. The amount of drug lost in alcohol during treatment was determined for each sample. 2.3. Release study 2.3.1. Determination of total ketoprofen content of the electrospun mats and films A known weight of the mat or the film (10 mg) was suspended in 10 mL basic solution of pH 9.0 (sodium hydroxide solution). The mat or the film was maintained for 24 h at 60 ◦ C in the basic solution and the amount of ketoprofen released by hydrolysis was determined by UV spectrophotometer at λmax = 260 nm. 2.3.2. Ketoprofen drug release The release of ketoprofen from the electrospun mats and from the films was determined by placing a known mass of the material (10 mg) in 10 mL phosphate buffer (PB) of pH 7.4 and was shacked in a shaking water bath (Shaker Water bath, Model #25, USA) at 37 ◦ C and at room temperature (20 ◦ C). The ketoprofen release was monitored by monitoring the absorbance at λmax = 260 nm as a function of time. The buffer solution was changed if the release drug gave absorbance higher than 2.0. Release experiments were done in triplicate. 3. Results and discussions The use of electrospun fibers as drug carriers will be promising in the future of biomedical applications especially, postoperative local chemotherapy. Electrospinning is one of the few techniques to prepare long fibers of nano- to micrometer diameter, great progress has been made in recent years. However, the study on the electrospun fibers carriers for drug delivery is very limited. Our previous publications were the first in this field [33]. In the current work, we are specifically interested to utilize the fully hydrolyzed (>99%) and the partially hydrolyzed PVA as the new drug delivery system. PVA solution containing ketoprofen as a model drug was spun. The PVA-drug electrospun fibers were stabilized to overcome the burst release phenomena and the PVA water solubility. 3.1. Preparation of fiber aggregates 3.1.1. Poly(vinyl alcohol) (PVA) Electrospinning of fully hydrolyzed PVA: Generally, when the applied electrical voltage exceeds a critical electrical potential electrospinning occurs. At this point the electrostatic force overcomes the surface tension of the polymer. For PVA, as the degree of hydrolysis approaches to 100%, the surface tension increases [28]. This leads to the inability to electrospinning of fully
Fig. 1. SEM micrograph of electrospun fully hydrolyzed PVA mat containing ketoprofen without soaking in alcohol, before drug release.
hydrolyzed PVA solution. Electrospinning of fully hydrolyzed PVA with ketoprofen entrapped on it, started to dominate when a small amount of surfactant (Triton X-100) and acetic acid were added. Electrospinning conditions, including the PVA concentration (10 wt%), TCD (15 cm), feeding rate 1.5 mL/h and voltage (20 kV) were used. A rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 0.5 to 1.5 m as shown in Fig. 1, before drug release. The sheet thickness ranged from 43 to 156 m. The electrospun mat is opaque due to light scattering from the fibrous structure. No ketoprofen crystals were detected by SEM either on the surface of the fibers or outside the fibers as shown in Fig. 1. This indicated that, ketoprofen was totally embedded in the fibers. Casting films containing the ketoprofen were prepared and the films thickness ranged from 52 to 228 m. Electrospinning of partially hydrolyzed PVA: Partially hydrolyzed PVA with ketoprofen entrapped on it was electrospun from 10 wt% water solution with feeding rate 0.5 mL/h when 20 kV was applied with TCD (15 cm). A rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 294 to 588 nm. The sheet thickness ranged from 50 to 87 m. The SEM of electrospun fiber before drug release is shown in Fig. 2. The electrospun mat is opaque due to light scattering from the fibrous structure. No ketoprofen crystals were detected by SEM either on the surface of the fibers or outside the fibers as shown in Fig. 2. This indicated that, ketoprofen was totally embedded in the fibers. Casting film containing the ketoprofen was prepared and the film thickness ranged from 80 to 468 m. Stabilization of PVA mats: When an electrospun PVA mat is immersed in water, the mat shrinks and becomes transparent and gelatinous. The electrospun PVA mat was stabilized towards disintegration in water by simple soaking in methanol or ethanol. Alcohol treatment served to increase the degree of crystallinity, and hence the number of physical crosslinks in the electrospun
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Table 2 Ketoprofen content for electrospun mats and films made from fully hydrolyzed PVA after sonication for 24 h at 60 ◦ C
Fig. 2. SEM micrograph of electrospun partially hydrolyzed PVA mat containing ketoprofen without soaking in alcohol before drug release.
PVA fibers (Fig. 3). This may occur by removal of residual water within the fibers by the alcohol, allowing PVA-water hydrogen bonding to be replaced by intermolecular polymer hydrogen bonding resulting in additional crystallization. Moreover, upon alcohol treatment, its visual mechanical properties increased. The main advantage in this stabilization technique is that no chemical used in the crosslinking process. Treatment of the ketoprofen containing electrospun fibers with lower alcohols physically crosslinked the PVA. Soaking the drug containing electrospun PVA in lower alcohol for at least 12 h preserves the integrity of the mat when it was immersed in water. However, there is a little loss of the drug entrapped in the fibers in the first few hours of alcohol treatment. 3.2. Determination of total ketoprofen content To evaluate the total content of ketoprofen in the samples, they were hydrolyzed by heating or sonication of a known amount
Fig. 3. SEM micrograph of electrospun partially hydrolyzed PVA mat containing ketoprofen after soaking in alcohol for 24 h before drug release.
Polymer code
Found from hydrolysis (mg ketoprofen)/(g polymer)
Calculated
PVA-spun PVA-spun-1 h PVA-spun-12 h PVA-spun-24 h PVA-film PVA-film-1 h PVA-film-24 h
47.15 26.93 32.90 39.90 48.73 31.82 26.08
49.98 49.93 49.93 49.94 49.93 45.94 45.98
of the mat or film in alkaline solution of pH 9.0. The amount released of ketoprofen from the sample was determined by UV spectrophotometer at λmax = 260 nm, at room temperature within 30 min. Then, the samples were heated at 60 ◦ C and the drug content was measured by UV spectrophotometer until it reaches a constant concentration of the drug. 3.2.1. Fully hydrolyzed PVA The fast hydrolysis studies of electrospun fully hydrolyzed PVA mats in alkaline solution of pH 9.0 at 60 ◦ C showed that, PVA-spun pre-methanol treatment contains 47.15 (mg ketoprofen)/(g polymer), PVA-spun treated with methanol for 1 h contains 26.93 (mg ketoprofen)/(g polymer), and PVA-spun treated with methanol for 24 h contains 39.90 (mg ketoprofen)/(g polymer) (Table 2). At the same time, the total content of ketoprofen for PVA-film pre-methanol treatment was 48.73 (mg ketoprofen)/(g polymer), 31.82 (mg ketoprofen)/(g polymer) for PVA-film treated with methanol for 1 h and 26.08 (mg ketoprofen)/(g polymer) for PVA-film treated with methanol for 24 h (Table 2). From the above investigation, it was found that the fully hydrolyzed electrospun PVA mat pre-methanol treatment contains 47.15 (mg ketoprofen)/(g polymer). However, this value of ketoprofen content was reduced to 26.93 (mg ketoprofen)/(g polymer) upon treatment with lower alcohol for 1 h, 32.9 for 12 h and to 39.90 (mg ketoprofen)/(g polymer) upon treatment with methanol for 24 h. This could be due to diffusion or dissolution of a small amount of the drug in the alcohol solution. However, the leached drug after soaking the spun mat in methanol for 24 h re-adsorbed again into the fiber matrix. This explanation could be the case for electrospun fibers but is not the case with the film since the surface area is low and does not favor the re-adsorption phenomena. Therefore, in case of the film, the drug content decreases with increasing the time of the methanol soaking. 3.2.2. Partially hydrolyzed PVA According to the fast release studies of drug-electrospun partially hydrolyzed PVA mats in alkaline solution of pH 9.0 at 60 ◦ C, the total ketoprofen content was 47.34 mg/g polymer for PVA-spun before methanol treatment while it was 27.07 and 29.92 mg/g polymer for PVA-spun mats treated with methanol for 1 h and for 24 h, respectively. Under the same conditions, the total ketoprofen contents for PVA-films were 46.31, 21.72 and 20.66 mg/g polymer (Table 3).
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Table 3 Ketoprofen content for electrospun mats and films made from partially hydrolyzed PVA after sonication for 24 h at 60 ◦ C Polymer code
Found from hydrolysis (mg ketoprofen)/(g polymer)
Calculated
PVA-spun PVA-spun-1 h PVA-spun-24 h PVA-film PVA-film-1 h PVA-film-24 h
47.34 27.0 30.0 46.31 21.72 20.66
49.80 49.80 50.19 50.37 45.01 49.35
From the above investigation, it was found that the partially hydrolyzed electrospun PVA mat without methanol treatment contains 47.34 (mg ketoprofen)/(g polymer). However, this value of ketoprofen content was reduced to 27.0 (mg ketoprofen)/(g polymer) upon treatment with methanol for 1 h and to 30 (mg ketoprofen)/(g polymer) upon treatment with methanol for 24 h. The same phenomena of drug dissolution and re-adsorption occurs here as in case of fully hydrolyzed PVA. 3.3. In vitro drug release The electrospinning technique is newly utilized in the field of drug delivery. The rate of ketoprofen released from electrospun fibers was investigated at pH 7.4 and at two different temperatures, 37 ◦ C (body temperature) and 20 ◦ C (room temperature). The rate of release is likely to depend on the temperature. 3.3.1. Drug release from electrospun fibers and films made from fully hydrolyzed poly(vinyl alcohol) (PVA) The release profiles of the ketoprofen drug from fully hydrolyzed PVA are shown in Figs. 4 and 5. The release rates were investigated in buffer solution of pH 7.4 at both room temperature (20 ◦ C) and the body temperature (37 ◦ C). The ketoprofen release from electrospun PVA containing ketoprofen was investigated as shown in Fig. 4 in pH 7.4 at 37 ◦ C. The untreated fibers showed initial fast release. It released about 85.24% of its drug content within the first 2 h and reached about 96.69% of its drug content within 2 weeks. On treatment of the electrospun fully hydrolyzed ketoprofen containing mat with methanol,
Fig. 4. In vitro release profile of ketoprofen from electrospun mat and film made from fully hydrolyzed PVA in phosphate buffer (pH 7.4) at the body temperature (37 ◦ C).
Fig. 5. In vitro release profile of ketoprofen from electrospun mat and film made from fully hydrolyzed PVA in phosphate buffer (pH 7.4) at room temperature (20 ◦ C).
the drug release profile varied completely, it became smoother with much lower initial fast release. This effect was also varied according to the period of methanol treatment, for example the initial fast release for 1 h methanol treated sample was 26.49% of its drug content, whereas was 10.42% of its drug content when the sample was treated for 24 h as shown in Figs. 4 and 5. The 1 h treated fibers showed a total release of 62.41% of its drug content after 2 weeks whereas, the 24 h treated sample showed slower release of 34.68% of its drug content after 2 weeks. This reduction in the rate of release for the treated samples is due to the physical crosslinking that occurs during the methanol treatment, which in turn slowed down the diffusion rate of the drug from the interior of the fiber to the release medium. For comparison, a film containing the ketoprofen drug was cast from fully hydrolyzed PVA. The release profiles of ketoprofen from the fully hydrolyzed PVA films were as shown in Figs. 4 and 5. The release rate from the fully hydrolyzed PVA film was highly affected by the methanol treatment. The untreated film showed initial fast release; it released 72.82% of its drug content within the first 2 h and showed a total release of 88.72% of its drug content within 2 weeks. In contrast, the 1 h methanol treated sample released 33.28% of its drug content within the first 2 h and a total release of 76.95% of its drug content within 2 weeks. The 24 h methanol treated sample showed about 20.04% of its drug content after 2 h release with total release of 69.18% of its drug content within 2 weeks. It is clear from the release characteristics of fibers and films that the effect of methanol treatment on electrospun fiber is more than on the films. The treatment delayed the release rate from the electrospun fiber more than it happened with the films. This could be attributed to the high surface area of the electrospun fibers compared to films, which consequently produce more physical crosslink on methanol treatment. The release of ketoprofen from the untreated electrospun, treated electrospun mats, untreated films and methanol treated films was also investigated at room temperature (20 ◦ C) is as shown in Fig. 5. Similar results for the factors affecting drug release were obtained from this investigation. Comparison of the effect of temperature on the release rate of ketoprofen from untreated electrospun, treated electrospun
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Fig. 6. In vitro release profile of ketoprofen from electrospun mat and film made from partially hydrolyzed PVA in phosphate buffer (pH 7.4) at the body temperature (37 ◦ C).
Fig. 7. In vitro release profile of ketoprofen from electrospun mat and film made from partially hydrolyzed PVA in phosphate buffer (pH 7.4) at room temperature (20 ◦ C).
mats, untreated films and methanol treated films were carried out. The results showed that the initial release from the treated mat and the film was almost the same at the two temperatures (20 and 37 ◦ C) while, the untreated fibers and films showed faster release rate and higher amounts release at 37 ◦ C compared to 20 ◦ C. The effect of temperature on the release rate of ketoprofen from untreated samples was investigated. All untreated samples showed initial fast release. The maximum amount released of ketoprofen from untreated electrospun mat within 2 weeks at room temperature (20 ◦ C) was 82.50% of its drug content. When the temperature was increased to 37 ◦ C, the amount released of ketoprofen was 96.69% of its drug content. A similar phenomenon was observed for the untreated films. The total amount released of ketoprofen over 2 weeks in pH 7.4 was 72.88% of its drug content at room temperature (20 ◦ C) whereas 88.72% of its drug content released at 37 ◦ C. Similar effect of the temperature was observed for the release of the drug from the methanol treated films and fibers.
content. The 24 h treated sample showed a release of 7.61 (mg drug)/(g polymer) which represents 28.11% of its drug content. During the first week of release studies, the electrospun mats showed sustained release for the drug. After 2 weeks, the release of ketoprofen was continued, the untreated electrospun mat showed a total release of 44.89 (mg drug)/(g polymer) which represents 94.80% of its drug content. At the same time, the 1 h methanol treated electrospun mat released 25.02 (mg drug)/(g polymer) which represents 92.42% of its drug content. The 24 h methanol treated electrospun mat released only 19.71 (mg drug)/(g polymer) which represents 72.79% of its drug content. For comparison, films were cast from partially hydrolyzed PVA. The release of ketoprofen from the films was investigated at the body temperature (37 ◦ C). At 37 ◦ C, the untreated partially hydrolyzed PVA film showed initial fast release, it released 68.92% of its drug content within the first 2 h and 84.34% of total release after 2 weeks, whereas, both the 1 h and 24 h methanol treated films showed less initial release rates followed by a very smooth increment. It released 20.36% of its drug content within the first 2 h and 80.34, 68.79% of its drug content after 2 weeks for the 1 h and 24 h methanol treated samples, respectively. The release rate of ketoprofen from untreated and treated electrospun mats and films was investigated at room temperature (20 ◦ C) as shown in Fig. 7. The release rate of ketoprofen from untreated and treated electrospun mats was carried out at room temperature (20 ◦ C). The results are as shown in (Table 4). Similar trend was obtained for cast films at room temperature (20 ◦ C) as shown in Fig. 7. The data obtained are summarized in (Table 5). The data showed clearly the effect of methanol treatment on the release rate. This can be seen from the high percent
3.3.2. Drug release of ketoprofen from electrospun fibers and films made from partially hydrolyzed poly(vinyl alcohol) (PVA) Partially hydrolyzed PVA was used as carrier for ketoprofen by electrospinning of the polymer solution containing calculated amount of ketoprofen. The aim of this work was to investigate the difference in the release rate of the drug from fully and partially hydrolyzed PVA since there is a difference in the electrospinning conditions of both. The release profiles of ketoprofen from partially hydrolyzed PVA are shown in Figs. 6 and 7. The release rates were investigated in buffer solution of pH 7.4 at both the body temperature (37 ◦ C) and at room temperature (20 ◦ C). The release profiles of ketoprofen from partially hydrolyzed electrospun PVA fibers at 37 ◦ C are shown in Fig. 6. It was noticed that the amount of ketoprofen released from methanol treated electrospun fibers was slower than that release from the untreated samples. For example, in the first 2 h, the amount released of ketoprofen from the untreated sample was 34.41 (mg drug)/(g polymer) which represents about 72.67% of its total drug content. At the same time, the 1 h treated methanol sample released 9.25 (mg drug)/(g polymer) which represents 34.15% of its drug
Table 4 Amount of ketoprofen released from electrospun partially hydrolyzed PVA mat at room temperature (20 ◦ C) Sample code
Untreated electrospun mat 1 h treated electrospun mat 24 h treated electrospun mat
Time (% of the drug content) 2h
1 week
2 weeks
58.43 30.85 25.31
76.04 54.31 47.70
83.82 70.26 58.88
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Table 5 Amount of ketoprofen released from partially hydrolyzed PVA film at room temperature (20 ◦ C) Sample code
Untreated film 1 h treated film 24 h treated film
Time (% of the drug content) 2h
1 week
2 weeks
52.99 18.07 15.25
71.84 48.87 30.43
75.35 60.68 41.17
released of ketoprofen from the untreated partially hydrolyzed PVA film, which is 52.99% of its drug content. This percent upon treatment with methanol for 1 h was reduced to 18.07% of its drug content and upon treatment for 24 h was reduced to 15.25% of its drug content. Also, the total amounts released of ketoprofen from the untreated, 1 h treated and 24 h treated samples were 75.35, 60.68, and 41.17% of its drug content, respectively. Comparison between the release rate of ketoprofen from untreated electrospun mats and cast films at the body temperature (37 ◦ C) and room temperature (20 ◦ C), indicated that, on increasing the temperature, the release rate increased. For example, the electrospun mat released 83.82% of its drug content after 2 weeks at room temperature (20 ◦ C) while it released about 94.80% of its drug content at 37 ◦ C at the same period. The same effect of temperature was observed for the cast film. The amount released from the film at room temperature is 75.35% of its drug content and it was increased to 84.34% of its drug content when the temperature was raised to 37 ◦ C. Similar trend was obtained for the 1 h methanol treated and 24 h methanol treated, electrospun mats and films. 4. Conclusion New system for the delivery of ketoprofen as non-steroidal anti-inflammatory drug (NSAID) based on the encapsulation of ketoprofen in the electrospun fibers was developed. Herein, new electrospun fibers as a new approach for drug delivery system using electrospinning technique were developed. These fibers were biodegradable polymers such as partially and fully hydrolyzed poly(vinyl alcohol) (PVA). The release was monitored in phosphate buffer of pH 7.4 at the body temperature (37 ◦ C) and at room temperature (20 ◦ C). It is worth mentioning here that fully hydrolyzed PVA can be stabilized against disintegration in water and its visual mechanical properties was improved by treatment with lower alcohol such as methanol. Also, upon the treatment with methanol, the burst release was disappeared. The results obtained from the release experiments showed that upon the treatment of electrospun PVA with methanol, the burst release was eliminated. Generally, the temperature of the medium played an important role, higher temperature for the release medium showed higher release rates. For PVA the release rates varied according to the degree of hydrolysis of the PVA. Methanol treated mats and films showed a lower release than untreated ones.
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Controlled release of ketoprofen from electrospun poly(vinyl alcohol) nanofibers El-Refaie Kenawy a,∗ , Fouad I. Abdel-Hay a , Mohamed H. El-Newehy a,b , Gary E. Wnek b,c a
Chemistry Department, Polymer Research Group, Faculty of Science, Tanta University, Tanta 31527, Egypt b Department of Chemical Engineering, Virginia Commonwealth University, Richmond, VA 23284, USA c Department of Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106-7217, USA Received 16 November 2006; received in revised form 28 December 2006; accepted 11 January 2007
Abstract Poly(vinyl alcohol) (PVA) as a biodegradable hydrophilic polymer has unique properties. It absorbs water and swells easily, but the swelling is inhibited by salts. Its physico-chemical properties depend on the degree of hydrolysis. The solubility of PVA in water increases greatly as its degree of hydrolysis increases. In the current work, new systems for the delivery of ketoprofen as non-steroidal anti-inflammatory drug (NSAID) were developed. New electrospun fibers containing ketoprofen and made from partially and fully hydrolyzed poly(vinyl alcohol) (PVA) were developed as drug delivery system. Moreover, electrospun PVA fibers were stabilized against disintegration in water by treatment with alcohol such as methanol. The release of ketoprofen from the electrospun fibers was determined by UV spectrophotometer at the body temperature (37 ◦ C) and at the room temperature (20 ◦ C). The results showed that upon the treatment of electrospun PVA with alcohol, the burst release was eliminated. © 2007 Elsevier B.V. All rights reserved. Keywords: Electrospinning; Poly(vinyl alcohol); Controlled-release; Ketoprofen; Anti-inflammatory drug
1. Introduction Poly(vinyl alcohol) (PVA) is a hydrophilic polymer, has unique properties. It absorbs water and swells easily, but the swelling is inhibited by salts [1,2]. Its physico-chemical properties depend on the degree of hydrolysis [3,4]. The solubility of PVA in water increases greatly as its degree of hydrolysis increases [5]. Moreover, PVA can be used for releasing biological and medical materials in a controlled way [6]. PVA was used in some modern technologies, such as hydrogels, polyelectrolytes, optics, and biomaterials [7] including soft contact lenses [8], implants [9], and artificial organs [10]. This is due to their inherent non-toxicity, non-carcinogenicity, good biocompatibility, and high degree of swelling in aqueous solutions. The PVA hydrogels were used as drug delivery matrices [11–14] or in the form of powders added to mixtures of other excipients for tablet formation [15].
∗
Corresponding author. E-mail address: [email protected] (E.-R. Kenawy).
0921-5093/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2007.01.039
Generally, polymer-based drug delivery systems are used to optimize the therapeutic properties of drugs and to render them safer, effective and reliable [16]. Non-steroidal antiinflammatory drugs (NSAIDs) are used for controlling pain and inflammation in rheumatic diseases. Administration of acidic NSAIDs to arthritic patients relieves pain and inflammatory swelling [17]. Ketoprofen, our drug model, is one of NSAIDs group. It is effective as anti-inflammatory agent in humans with flogistic diseases. The major side effects involve gastrointestinal symptoms. Due to the many advantages of the PVA, much attention has been focused on the electrospinning of PVA for applications in different fields such as biosensor [18], antimicrobial fibers [19–21], composites [22,23], macroporus and nanoporous films and membranes [24–26], and filtration applications [27]. Our laboratories have been especially interested in the electrospinning of poly(vinyl alcohol) (PVA) because it is an inexpensive biocompatible material. Electrospinning is an inexpensive method that produces polymer fibers with diameter in the range of nano- to a few microns using electrically driven jet of polymer solution or melt. The fibers are driven by charging a liquid typically to 5–30 kV versus ground at short distance
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away, which leads to charge injection into the liquid from the electrode. As the solvent of the polymer jet evaporates, the jet solidifies and a polymer fiber is formed. Electrospinning with research interests usually focusing on the theoretical foundation of the electrospinning process, including fiber initiation, jet instability and the structure and morphology of the electrospun fiber [28]. Recently, electrospinning includes a variety of applications including carbonaceous materials, tissue engineering scaffolds [29–32], separation filters, wound dressing materials, controlled-drug delivery platforms [33], and sensors [34–36]. In the current work, new systems of controlled drug release via electrospinning technique were developed. Electrospinning of partially and fully hydrolyzed PVA was carried out. Moreover, PVA was stabilized against disintegration in water and their visual mechanical property was increased by treatment with alcohol (not measured). The PVA electrospun fibers were used as controlled-release system for ketoprofen and were compared with casting films with the same composition. 2. Experimental 2.1. General experimental procedure 2.1.1. Materials Poly(vinyl alcohol) (PVA) (99+% hydrolyzed) (average Mw 85–146 kg/mol), poly(vinyl alcohol) (PVA) (87–89% hydrolyzed) (average Mw 124–186 kg/mol), methanol, sodium phosphate dibasic (Na2 HPO4 ) and potassium phosphate monobasic (KH2 PO4 ) were purchased from Aldrich (USA). Triton® X-100 was purchased from Sigma–Aldrich Corp. St. Louis, MO, USA. Ketoprofen was purchased from Sigma (USA). All materials were used as received without further purification. 2.1.2. Instruments Microscopy: Scanning electron microscope (SEM) was used to study the morphology of a dried mats and were performed on a JSM-820 scanning electron microscope (JEOL Ltd., USA). Precision micrometer: The thickness of electrospun mats and films was measured using PRECISION MICROMETER, Model No. 49–61, Range 0–1.270 mm, Testing Machines INC. AMITVILLE N.Y. (USA). Spectroscopy: UV spectra were recorded using GENESYSTM 6 Spectrophotometer (USA). 2.1.3. Preparation of phosphate buffer solution (PB) The phosphate buffer solution (pH 9.0) was prepared by dissolving sodium phosphate dibasic (Na2 HPO4 ) (35.49 g) in 1 L deionized water and the pH was adjusted to 9.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The phosphate buffer solution (pH 7.4) was prepared by dissolving sodium phosphate dibasic (Na2 HPO4 ) (21.70 g) and potassium phosphate monobasic (KH2 PO4 ) (2.60 g) in 1 L deionized water and the pH was adjusted to 7.4 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. The pH 2.0 buffer solu-
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tions were adjusted with 0.1N hydrochloric acid and the pH was adjusted to 2.0 using 0.1N sodium hydroxide and 0.1N hydrochloric acid solutions. 2.2. Electrospinning Electrospinning apparatus: The setup of our electrospinning apparatus consists of a syringe with a flat-end metal needle cut, a syringe pump (model 100 KD scientific Inc., New Hope, PA) for controlled feeding rates, a grounded cylindrical stainless steel mandrel, and a high voltage dc power supply (Spellman, CZE1000R, Spellman High voltage Electronics Corp., Hauppauge, NY). 2.2.1. Preparation of polymer solution and fiber aggregates 2.2.1.1. Fully hydrolyzed poly(vinyl alcohol). Fully hydrolyzed poly(vinyl alcohol) was dissolved in deionized water on heating at 90 ◦ C for 6 h with vigorous stirring to obtain a concentration of 10 wt% solution. Then, the PVA solution was cooled to room temperature. Triton X-100 in concentration of 2.50% (w/w) PVA was added. The mixture was stirred for further 1 h. Ketoprofen in concentration of 5% (w/w) PVA was dissolved in a small amount of methanol and was added to the mixture of PVA/Triton X-100 and stirred for 20–30 min before electrospinning. 2.2.1.2. Partially hydrolyzed poly(vinyl alcohol). Partially hydrolyzed poly(vinyl alcohol) solution was prepared by dissolving PVA in deionized water at room temperature overnight with vigorous stirring to obtain a concentration of 10 wt% solution. Ketoprofen in concentration of 5% (w/w) PVA was dissolved in a small amount of methanol and was added to PVA solution and was stirred for 20–30 min before electrospinning. 2.2.2. General procedure for electrospinning process For the electrospun microfiber fabrics, a series of PVA solutions was prepared by dissolving the polymers in water at a concentration of 10 wt% and various concentrations of the drug was added as described earlier. The polymer solution was delivered at a constant flow rate (10 ml/h) using a syringe pump to the stainless steel blunt-ended needle with an air gap between the metal collector and the needle tip of 15 cm at a driving voltage of 20 kV (Table 1). The electrospun mats was dried in hood at room temperature overnight. For the purpose of comparison, casting film was made onto Petri dish. Table 1 Summary of electrospinning parameters applied for electrospinning of fully and partially hydrolyzed poly(vinyl alcohol) Sample code
Applied voltage (kV)
Feeding rate (mL/h)
TCDa (cm)
Polarity
PVA (99%) PVA (87–89%)
20 20
1.5 0.5
15 15
+ve +ve
a
Tip-to-collector distance.
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2.2.3. Stabilization of electrospun poly(vinyl alcohol) fibers containing ketoprofen The electrospun mats of fully and partially hydrolyzed PVA, were treated with alcohol such as methanol for periods of 1 and 24 h and were then dried overnight in the hood at room temperature. For the purpose of comparison, casting film was also treated with alcohol in the same way as for electrospun fibers. The amount of drug lost in alcohol during treatment was determined for each sample. 2.3. Release study 2.3.1. Determination of total ketoprofen content of the electrospun mats and films A known weight of the mat or the film (10 mg) was suspended in 10 mL basic solution of pH 9.0 (sodium hydroxide solution). The mat or the film was maintained for 24 h at 60 ◦ C in the basic solution and the amount of ketoprofen released by hydrolysis was determined by UV spectrophotometer at λmax = 260 nm. 2.3.2. Ketoprofen drug release The release of ketoprofen from the electrospun mats and from the films was determined by placing a known mass of the material (10 mg) in 10 mL phosphate buffer (PB) of pH 7.4 and was shacked in a shaking water bath (Shaker Water bath, Model #25, USA) at 37 ◦ C and at room temperature (20 ◦ C). The ketoprofen release was monitored by monitoring the absorbance at λmax = 260 nm as a function of time. The buffer solution was changed if the release drug gave absorbance higher than 2.0. Release experiments were done in triplicate. 3. Results and discussions The use of electrospun fibers as drug carriers will be promising in the future of biomedical applications especially, postoperative local chemotherapy. Electrospinning is one of the few techniques to prepare long fibers of nano- to micrometer diameter, great progress has been made in recent years. However, the study on the electrospun fibers carriers for drug delivery is very limited. Our previous publications were the first in this field [33]. In the current work, we are specifically interested to utilize the fully hydrolyzed (>99%) and the partially hydrolyzed PVA as the new drug delivery system. PVA solution containing ketoprofen as a model drug was spun. The PVA-drug electrospun fibers were stabilized to overcome the burst release phenomena and the PVA water solubility. 3.1. Preparation of fiber aggregates 3.1.1. Poly(vinyl alcohol) (PVA) Electrospinning of fully hydrolyzed PVA: Generally, when the applied electrical voltage exceeds a critical electrical potential electrospinning occurs. At this point the electrostatic force overcomes the surface tension of the polymer. For PVA, as the degree of hydrolysis approaches to 100%, the surface tension increases [28]. This leads to the inability to electrospinning of fully
Fig. 1. SEM micrograph of electrospun fully hydrolyzed PVA mat containing ketoprofen without soaking in alcohol, before drug release.
hydrolyzed PVA solution. Electrospinning of fully hydrolyzed PVA with ketoprofen entrapped on it, started to dominate when a small amount of surfactant (Triton X-100) and acetic acid were added. Electrospinning conditions, including the PVA concentration (10 wt%), TCD (15 cm), feeding rate 1.5 mL/h and voltage (20 kV) were used. A rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 0.5 to 1.5 m as shown in Fig. 1, before drug release. The sheet thickness ranged from 43 to 156 m. The electrospun mat is opaque due to light scattering from the fibrous structure. No ketoprofen crystals were detected by SEM either on the surface of the fibers or outside the fibers as shown in Fig. 1. This indicated that, ketoprofen was totally embedded in the fibers. Casting films containing the ketoprofen were prepared and the films thickness ranged from 52 to 228 m. Electrospinning of partially hydrolyzed PVA: Partially hydrolyzed PVA with ketoprofen entrapped on it was electrospun from 10 wt% water solution with feeding rate 0.5 mL/h when 20 kV was applied with TCD (15 cm). A rotating metal drum was used to collect the resulting fiber to give a white sheet of non-woven fiber. The non-woven fiber diameters ranged from 294 to 588 nm. The sheet thickness ranged from 50 to 87 m. The SEM of electrospun fiber before drug release is shown in Fig. 2. The electrospun mat is opaque due to light scattering from the fibrous structure. No ketoprofen crystals were detected by SEM either on the surface of the fibers or outside the fibers as shown in Fig. 2. This indicated that, ketoprofen was totally embedded in the fibers. Casting film containing the ketoprofen was prepared and the film thickness ranged from 80 to 468 m. Stabilization of PVA mats: When an electrospun PVA mat is immersed in water, the mat shrinks and becomes transparent and gelatinous. The electrospun PVA mat was stabilized towards disintegration in water by simple soaking in methanol or ethanol. Alcohol treatment served to increase the degree of crystallinity, and hence the number of physical crosslinks in the electrospun
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Table 2 Ketoprofen content for electrospun mats and films made from fully hydrolyzed PVA after sonication for 24 h at 60 ◦ C
Fig. 2. SEM micrograph of electrospun partially hydrolyzed PVA mat containing ketoprofen without soaking in alcohol before drug release.
PVA fibers (Fig. 3). This may occur by removal of residual water within the fibers by the alcohol, allowing PVA-water hydrogen bonding to be replaced by intermolecular polymer hydrogen bonding resulting in additional crystallization. Moreover, upon alcohol treatment, its visual mechanical properties increased. The main advantage in this stabilization technique is that no chemical used in the crosslinking process. Treatment of the ketoprofen containing electrospun fibers with lower alcohols physically crosslinked the PVA. Soaking the drug containing electrospun PVA in lower alcohol for at least 12 h preserves the integrity of the mat when it was immersed in water. However, there is a little loss of the drug entrapped in the fibers in the first few hours of alcohol treatment. 3.2. Determination of total ketoprofen content To evaluate the total content of ketoprofen in the samples, they were hydrolyzed by heating or sonication of a known amount
Fig. 3. SEM micrograph of electrospun partially hydrolyzed PVA mat containing ketoprofen after soaking in alcohol for 24 h before drug release.
Polymer code
Found from hydrolysis (mg ketoprofen)/(g polymer)
Calculated
PVA-spun PVA-spun-1 h PVA-spun-12 h PVA-spun-24 h PVA-film PVA-film-1 h PVA-film-24 h
47.15 26.93 32.90 39.90 48.73 31.82 26.08
49.98 49.93 49.93 49.94 49.93 45.94 45.98
of the mat or film in alkaline solution of pH 9.0. The amount released of ketoprofen from the sample was determined by UV spectrophotometer at λmax = 260 nm, at room temperature within 30 min. Then, the samples were heated at 60 ◦ C and the drug content was measured by UV spectrophotometer until it reaches a constant concentration of the drug. 3.2.1. Fully hydrolyzed PVA The fast hydrolysis studies of electrospun fully hydrolyzed PVA mats in alkaline solution of pH 9.0 at 60 ◦ C showed that, PVA-spun pre-methanol treatment contains 47.15 (mg ketoprofen)/(g polymer), PVA-spun treated with methanol for 1 h contains 26.93 (mg ketoprofen)/(g polymer), and PVA-spun treated with methanol for 24 h contains 39.90 (mg ketoprofen)/(g polymer) (Table 2). At the same time, the total content of ketoprofen for PVA-film pre-methanol treatment was 48.73 (mg ketoprofen)/(g polymer), 31.82 (mg ketoprofen)/(g polymer) for PVA-film treated with methanol for 1 h and 26.08 (mg ketoprofen)/(g polymer) for PVA-film treated with methanol for 24 h (Table 2). From the above investigation, it was found that the fully hydrolyzed electrospun PVA mat pre-methanol treatment contains 47.15 (mg ketoprofen)/(g polymer). However, this value of ketoprofen content was reduced to 26.93 (mg ketoprofen)/(g polymer) upon treatment with lower alcohol for 1 h, 32.9 for 12 h and to 39.90 (mg ketoprofen)/(g polymer) upon treatment with methanol for 24 h. This could be due to diffusion or dissolution of a small amount of the drug in the alcohol solution. However, the leached drug after soaking the spun mat in methanol for 24 h re-adsorbed again into the fiber matrix. This explanation could be the case for electrospun fibers but is not the case with the film since the surface area is low and does not favor the re-adsorption phenomena. Therefore, in case of the film, the drug content decreases with increasing the time of the methanol soaking. 3.2.2. Partially hydrolyzed PVA According to the fast release studies of drug-electrospun partially hydrolyzed PVA mats in alkaline solution of pH 9.0 at 60 ◦ C, the total ketoprofen content was 47.34 mg/g polymer for PVA-spun before methanol treatment while it was 27.07 and 29.92 mg/g polymer for PVA-spun mats treated with methanol for 1 h and for 24 h, respectively. Under the same conditions, the total ketoprofen contents for PVA-films were 46.31, 21.72 and 20.66 mg/g polymer (Table 3).
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Table 3 Ketoprofen content for electrospun mats and films made from partially hydrolyzed PVA after sonication for 24 h at 60 ◦ C Polymer code
Found from hydrolysis (mg ketoprofen)/(g polymer)
Calculated
PVA-spun PVA-spun-1 h PVA-spun-24 h PVA-film PVA-film-1 h PVA-film-24 h
47.34 27.0 30.0 46.31 21.72 20.66
49.80 49.80 50.19 50.37 45.01 49.35
From the above investigation, it was found that the partially hydrolyzed electrospun PVA mat without methanol treatment contains 47.34 (mg ketoprofen)/(g polymer). However, this value of ketoprofen content was reduced to 27.0 (mg ketoprofen)/(g polymer) upon treatment with methanol for 1 h and to 30 (mg ketoprofen)/(g polymer) upon treatment with methanol for 24 h. The same phenomena of drug dissolution and re-adsorption occurs here as in case of fully hydrolyzed PVA. 3.3. In vitro drug release The electrospinning technique is newly utilized in the field of drug delivery. The rate of ketoprofen released from electrospun fibers was investigated at pH 7.4 and at two different temperatures, 37 ◦ C (body temperature) and 20 ◦ C (room temperature). The rate of release is likely to depend on the temperature. 3.3.1. Drug release from electrospun fibers and films made from fully hydrolyzed poly(vinyl alcohol) (PVA) The release profiles of the ketoprofen drug from fully hydrolyzed PVA are shown in Figs. 4 and 5. The release rates were investigated in buffer solution of pH 7.4 at both room temperature (20 ◦ C) and the body temperature (37 ◦ C). The ketoprofen release from electrospun PVA containing ketoprofen was investigated as shown in Fig. 4 in pH 7.4 at 37 ◦ C. The untreated fibers showed initial fast release. It released about 85.24% of its drug content within the first 2 h and reached about 96.69% of its drug content within 2 weeks. On treatment of the electrospun fully hydrolyzed ketoprofen containing mat with methanol,
Fig. 4. In vitro release profile of ketoprofen from electrospun mat and film made from fully hydrolyzed PVA in phosphate buffer (pH 7.4) at the body temperature (37 ◦ C).
Fig. 5. In vitro release profile of ketoprofen from electrospun mat and film made from fully hydrolyzed PVA in phosphate buffer (pH 7.4) at room temperature (20 ◦ C).
the drug release profile varied completely, it became smoother with much lower initial fast release. This effect was also varied according to the period of methanol treatment, for example the initial fast release for 1 h methanol treated sample was 26.49% of its drug content, whereas was 10.42% of its drug content when the sample was treated for 24 h as shown in Figs. 4 and 5. The 1 h treated fibers showed a total release of 62.41% of its drug content after 2 weeks whereas, the 24 h treated sample showed slower release of 34.68% of its drug content after 2 weeks. This reduction in the rate of release for the treated samples is due to the physical crosslinking that occurs during the methanol treatment, which in turn slowed down the diffusion rate of the drug from the interior of the fiber to the release medium. For comparison, a film containing the ketoprofen drug was cast from fully hydrolyzed PVA. The release profiles of ketoprofen from the fully hydrolyzed PVA films were as shown in Figs. 4 and 5. The release rate from the fully hydrolyzed PVA film was highly affected by the methanol treatment. The untreated film showed initial fast release; it released 72.82% of its drug content within the first 2 h and showed a total release of 88.72% of its drug content within 2 weeks. In contrast, the 1 h methanol treated sample released 33.28% of its drug content within the first 2 h and a total release of 76.95% of its drug content within 2 weeks. The 24 h methanol treated sample showed about 20.04% of its drug content after 2 h release with total release of 69.18% of its drug content within 2 weeks. It is clear from the release characteristics of fibers and films that the effect of methanol treatment on electrospun fiber is more than on the films. The treatment delayed the release rate from the electrospun fiber more than it happened with the films. This could be attributed to the high surface area of the electrospun fibers compared to films, which consequently produce more physical crosslink on methanol treatment. The release of ketoprofen from the untreated electrospun, treated electrospun mats, untreated films and methanol treated films was also investigated at room temperature (20 ◦ C) is as shown in Fig. 5. Similar results for the factors affecting drug release were obtained from this investigation. Comparison of the effect of temperature on the release rate of ketoprofen from untreated electrospun, treated electrospun
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Fig. 6. In vitro release profile of ketoprofen from electrospun mat and film made from partially hydrolyzed PVA in phosphate buffer (pH 7.4) at the body temperature (37 ◦ C).
Fig. 7. In vitro release profile of ketoprofen from electrospun mat and film made from partially hydrolyzed PVA in phosphate buffer (pH 7.4) at room temperature (20 ◦ C).
mats, untreated films and methanol treated films were carried out. The results showed that the initial release from the treated mat and the film was almost the same at the two temperatures (20 and 37 ◦ C) while, the untreated fibers and films showed faster release rate and higher amounts release at 37 ◦ C compared to 20 ◦ C. The effect of temperature on the release rate of ketoprofen from untreated samples was investigated. All untreated samples showed initial fast release. The maximum amount released of ketoprofen from untreated electrospun mat within 2 weeks at room temperature (20 ◦ C) was 82.50% of its drug content. When the temperature was increased to 37 ◦ C, the amount released of ketoprofen was 96.69% of its drug content. A similar phenomenon was observed for the untreated films. The total amount released of ketoprofen over 2 weeks in pH 7.4 was 72.88% of its drug content at room temperature (20 ◦ C) whereas 88.72% of its drug content released at 37 ◦ C. Similar effect of the temperature was observed for the release of the drug from the methanol treated films and fibers.
content. The 24 h treated sample showed a release of 7.61 (mg drug)/(g polymer) which represents 28.11% of its drug content. During the first week of release studies, the electrospun mats showed sustained release for the drug. After 2 weeks, the release of ketoprofen was continued, the untreated electrospun mat showed a total release of 44.89 (mg drug)/(g polymer) which represents 94.80% of its drug content. At the same time, the 1 h methanol treated electrospun mat released 25.02 (mg drug)/(g polymer) which represents 92.42% of its drug content. The 24 h methanol treated electrospun mat released only 19.71 (mg drug)/(g polymer) which represents 72.79% of its drug content. For comparison, films were cast from partially hydrolyzed PVA. The release of ketoprofen from the films was investigated at the body temperature (37 ◦ C). At 37 ◦ C, the untreated partially hydrolyzed PVA film showed initial fast release, it released 68.92% of its drug content within the first 2 h and 84.34% of total release after 2 weeks, whereas, both the 1 h and 24 h methanol treated films showed less initial release rates followed by a very smooth increment. It released 20.36% of its drug content within the first 2 h and 80.34, 68.79% of its drug content after 2 weeks for the 1 h and 24 h methanol treated samples, respectively. The release rate of ketoprofen from untreated and treated electrospun mats and films was investigated at room temperature (20 ◦ C) as shown in Fig. 7. The release rate of ketoprofen from untreated and treated electrospun mats was carried out at room temperature (20 ◦ C). The results are as shown in (Table 4). Similar trend was obtained for cast films at room temperature (20 ◦ C) as shown in Fig. 7. The data obtained are summarized in (Table 5). The data showed clearly the effect of methanol treatment on the release rate. This can be seen from the high percent
3.3.2. Drug release of ketoprofen from electrospun fibers and films made from partially hydrolyzed poly(vinyl alcohol) (PVA) Partially hydrolyzed PVA was used as carrier for ketoprofen by electrospinning of the polymer solution containing calculated amount of ketoprofen. The aim of this work was to investigate the difference in the release rate of the drug from fully and partially hydrolyzed PVA since there is a difference in the electrospinning conditions of both. The release profiles of ketoprofen from partially hydrolyzed PVA are shown in Figs. 6 and 7. The release rates were investigated in buffer solution of pH 7.4 at both the body temperature (37 ◦ C) and at room temperature (20 ◦ C). The release profiles of ketoprofen from partially hydrolyzed electrospun PVA fibers at 37 ◦ C are shown in Fig. 6. It was noticed that the amount of ketoprofen released from methanol treated electrospun fibers was slower than that release from the untreated samples. For example, in the first 2 h, the amount released of ketoprofen from the untreated sample was 34.41 (mg drug)/(g polymer) which represents about 72.67% of its total drug content. At the same time, the 1 h treated methanol sample released 9.25 (mg drug)/(g polymer) which represents 34.15% of its drug
Table 4 Amount of ketoprofen released from electrospun partially hydrolyzed PVA mat at room temperature (20 ◦ C) Sample code
Untreated electrospun mat 1 h treated electrospun mat 24 h treated electrospun mat
Time (% of the drug content) 2h
1 week
2 weeks
58.43 30.85 25.31
76.04 54.31 47.70
83.82 70.26 58.88
396
E.-R. Kenawy et al. / Materials Science and Engineering A 459 (2007) 390–396
Table 5 Amount of ketoprofen released from partially hydrolyzed PVA film at room temperature (20 ◦ C) Sample code
Untreated film 1 h treated film 24 h treated film
Time (% of the drug content) 2h
1 week
2 weeks
52.99 18.07 15.25
71.84 48.87 30.43
75.35 60.68 41.17
released of ketoprofen from the untreated partially hydrolyzed PVA film, which is 52.99% of its drug content. This percent upon treatment with methanol for 1 h was reduced to 18.07% of its drug content and upon treatment for 24 h was reduced to 15.25% of its drug content. Also, the total amounts released of ketoprofen from the untreated, 1 h treated and 24 h treated samples were 75.35, 60.68, and 41.17% of its drug content, respectively. Comparison between the release rate of ketoprofen from untreated electrospun mats and cast films at the body temperature (37 ◦ C) and room temperature (20 ◦ C), indicated that, on increasing the temperature, the release rate increased. For example, the electrospun mat released 83.82% of its drug content after 2 weeks at room temperature (20 ◦ C) while it released about 94.80% of its drug content at 37 ◦ C at the same period. The same effect of temperature was observed for the cast film. The amount released from the film at room temperature is 75.35% of its drug content and it was increased to 84.34% of its drug content when the temperature was raised to 37 ◦ C. Similar trend was obtained for the 1 h methanol treated and 24 h methanol treated, electrospun mats and films. 4. Conclusion New system for the delivery of ketoprofen as non-steroidal anti-inflammatory drug (NSAID) based on the encapsulation of ketoprofen in the electrospun fibers was developed. Herein, new electrospun fibers as a new approach for drug delivery system using electrospinning technique were developed. These fibers were biodegradable polymers such as partially and fully hydrolyzed poly(vinyl alcohol) (PVA). The release was monitored in phosphate buffer of pH 7.4 at the body temperature (37 ◦ C) and at room temperature (20 ◦ C). It is worth mentioning here that fully hydrolyzed PVA can be stabilized against disintegration in water and its visual mechanical properties was improved by treatment with lower alcohol such as methanol. Also, upon the treatment with methanol, the burst release was disappeared. The results obtained from the release experiments showed that upon the treatment of electrospun PVA with methanol, the burst release was eliminated. Generally, the temperature of the medium played an important role, higher temperature for the release medium showed higher release rates. For PVA the release rates varied according to the degree of hydrolysis of the PVA. Methanol treated mats and films showed a lower release than untreated ones.
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