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Nuclear track microfilters in controlled drug delivery against chronic skin disease
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Radiation Measurements 36 (2003) 581 – 584 www.elsevier.com/locate/radmeas
Nuclear track micro!lters in controlled drug delivery against chronic skin disease D. Gopalani∗ , A.S. Jodha, S. Saravanan, S. Kumar Defence Laboratory, Ministry of Defence, Ratanada Palace, Jodhpur-342 011, India Received 21 October 2002; received in revised form 3 March 2003; accepted 7 May 2003
Abstract Nuclear track micro!lters have been developed for transdermal therapeutic system. The transdermal therapeutic method reduces the toxicity of the drug as compared to other conventional methods. For this purpose a slow drug release system containing the nuclear track micro!lter was developed. This device was applied to the patients su5ering from psoriasis and cellulites diseases. The delivery of the drug to the patient was con!rmed through high performance liquid chromatography. The preliminary results have shown that patients are responding to drugs with minimum toxicity. c 2003 Published by Elsevier Ltd. Keywords: SSNTD; Nuclear track micro!lter; Slow drug release system; Transdermal therapeutic system
1. Introduction
2. Experimental
The nuclear track micro!lter (NTMF) is a kind of novel material used successfully in various !elds such as precise separation of biological cells, !ltering polluted air steams, stabilizing beverages, microelectronics, pharmaceutical and waste water recycling, etc. (Flerov, 1984; Varobiev et al., 1989). These !lters are fabricated by exposing appropriate track forming insulating material in nuclear reactor or heavy ion accelerator and subsequently chemical etching process to enlarge the radiation damage in order to produce the “through hole”. In the present study, NTMFs have been developed by exposing polyester !lms to 28 Si ion and then sensitized followed by chemical etching with alkaline solution. The developed nuclear track micro!lters have been used as a drug release rate controlling membrane for transdermal therapeutic system. This method shows good zero order release kinetics, i.e. provides a constant rate of drug release over a de!ned period of time.
2.1. Production of NTMFs Indigenously available polyester !lm in the form of Sun control !lm has been used for the production of NTMFs. This !lm (thickness 25 m) was bombarded with 28 Si ion beam of energy 100 MeV in 14 MV pelletron at Tata Institute of Fundamental Research, Mumbai. For improvement of track etch rate (linear rate of chemical attack along the ion trajectory) of 28 Si ion in polyester !lm, a new pre-treatment procedure known as sensibilization of higher eGciency was developed (Gopalani et al., 2000). The sensibilzation of the irradiated !lms were carried out with dimethylformamide (DMF) solvent for half an hour at a temperature of 70◦ C. The DMF solvent treatment was followed by a solvent exchange with ethanol at room temperature for 15 min, since some solvent was not mixable with etchant. The sensibilized !lms were then etched in 5 N-NaOH at 50◦ C by means of thermostatic system. The pore size is controlled by the etching time. 2.2. Slow drug release system (SDRS)
∗
Corresponding author. Tel.: +91-291-567172; fax: +91-291-2511158. E-mail address: [email protected] (D. Gopalani). c 2003 Published by Elsevier Ltd. 1350-4487/03/$ - see front matter doi:10.1016/S1350-4487(03)00205-1
The developed !lters were !tted in pressure driven slow drug release system. This device has the shape of
582
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
Fig. 1. Slow drug release system.
wristwatch (Fig. 1). The !lters of pore size 2–3 m were kept to provide a uniform zero order deliver rate of drug in a long period. This device was applied to the patients su5ering from psoriasis and cellulites. The drug delivered through !lters by applying the pressure through a piston. The delivery of drug into the patient was con!rmed through high performance liquid chromatography of serum taken before and after the application of slow drug release system. The serum of patient before and after application (∼5 h) were taken and allowed to clot. Clotted blood was centrifuged for 10 min. at 1200 rpm before analysis then these (450 l in both case) mixed with internal standard (50 l aminopterin) in a glass tube. The mixture was vortexed after adding 500 l acetone and was centrifuged at 1000 rpm for 10 min. A volume of 600 l of the supernatant was
transferred to a second tube containing 600 l n-butanol and 800 l diethyl ether. This was mixed using the vortex mixer, then the mixture was transferred to a second microtube sizing 5 mm × 100 mm. This was centrifuged again at 1000 rpm for 10 min. The supernatant was discarded. The lower aqueous portion was directly injected on to the reverse phase C-18 column using 10 l Hamilton syringe. Peaks were identi!ed by using retention times compared with the internal standard. The retention time for drug (in this study only methotrexate was detected) was 9:09 min while 6:32 min for internal standard. Chromatography was performed at ambient temperature with detection at 313 nm. The area of peak in both cases, i.e. before and after application were taken for comparison point of view.
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
583
3. Results and discussion 3.1. Transdermal therapeutic system Administering 10 or 12 tablets to someone to help them manage their chronic illness may someday be a memory. In these days a novel method as Transdermal drug administration, which provides improve compliance, minimum side e5ects and more patient satisfaction has gained momentum. Transdermal, meaning ‘through the skin’ refers to a method of administering substances via a topical application to the skin. In this, substances are absorbed slowly through the skin and into the bloodstream. This route of absorption provides direct systemic administrations by delivering the compound through the skin in a time-released manner, which allows a direct access path to blood circulation. In this technique, controlled drug delivery occurs when a polymer, whether natural or synthetic, is judiciously combined with a drug or other active agent in such a way that the active agent is released from the material in a predesigned manner (Ishihara et al., 1983). The purpose behind controlling the drug delivery is to achieve more e5ective therapies while eliminating the potential for both under and overdosing. The goal of controlled release systems is to achieve a delivery pro!le that would yield a high blood level of the drug over a long period of time. With traditional tablets or injections, the drug level in the blood rises after each administration of the drug and then decreases until the next administration. There are three primarily mechanisms by which active agents can be released from a delivery system, namely, degradation, swelling and di5usion. In the present work, the drug delivery system was developed on the di5usion mechanism. Di5usion occurs when a drug or other active agent passes through the polymer that forms the controlled release device. In the present study, a transdermal therapeutic system has been designed in the shape of a wristwatch, where drug remains in a reservoir volume of 5-ml. This drug is covered and delivered to patient through developed nuclear track micro!lter made of polyester !lms. This material is selected due to its physical strength, transparency, chemically inert and free of leachable impurities. It also has an appropriate physical structure with minimal undesired aging and readily processable. 3.2. Nuclear track micro4lter The nuclear track micro!lters have been developed by bombarding these polyester !lms with 28 Si ions at Tata Institute of Fundamental Research, Mumbai. The 28 Si ion as M passing through polyester !lm leaves narrow (∼30–100 A) trails of damage. In conventional chemical etching etchant (NaOH/KOH) dissolve or degrade damaged region at a much higher rate (track etch rate, i.e. Vt ) than the undamaged material (bulk etch rate Vb ). The narrow damage trail is thus gouged out by the etchant, forming a hole. For cylin-
Fig. 2. Nuclear track micro!lter.
drical pores, the cone angle should be minimum, which can be obtained by larger value of Vt . The Vt of heavy ion is higher as its speci!c energy loss is more, which produces maximum damage along the trajectory. The 28 Si (lower atomic number) ion gives smaller track etch rate along the ion trajectory in the !lm after the conventional chemical etching. This smaller value of track etch rate cannot produce !ne pores of a nearly cylindrical shape. The DMF treatment enhanced the track etch rate of 28 Si ion because of similarity in solubility parameter of polyester !lm. Hence DMF penetrates into the polyester matrix and induces a crystallization of the amorphous region in the polyester. This e5ect produces more chemical attack along the ion trajectory and its value is !ve times more as compared to that of without any treatment. This enhanced value of track etch rate is comparable with speci!c energy loss of higher atomic number ion in polyester !lms. The pore size of the !lters was determined with the help of SEM. The NTMFs, of pore size ∼2–3 m were used in the present work (Fig. 2). The pore diameter was selected based on the required drug release rate from the slow drug release system. In the present study, the requirement of drug delivery to patient was 2:5 ml=day. The release rate measurement was carried out using Millipore assembly (Guo et al., 1990). In this assembly, a constant pressure was applied across the nuclear track micro!lter and Dow rate was measured. This pressure was same as the pressure maintained in the device using piston arrangement and its value is 6:3 mbar as overpressure. Based on the Dow rate measurement the release rate, i.e. 2:5 ml=day was optimized. The application of this device to each patient was given once in every week time (as described drug dosage). The reduction of these diseases starts after 2 weeks time. The other adverse e5ects were also checked through necessary tests were carried out simultaneously. A case history of each
584
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
patient in which all the results of these tests were documented in a typed Performa was maintained. Based on these results, a con!rmation was made that this device does not produce any side e5ects due to these medicine via slow drug release system. 3.3. Application of NTMFs for chronic skin diseases The slow drug release system was used as transdermal therapeutic for the treatment of psoriasis and cellulites. These diseases are chronic skin diseases. For the treatment of these diseases, Methotrexate and Taxim-o (Ce!xime) drugs are given to patients, respectively. The toxicity of these drugs to liver is more and via this route its e5ect became even much more (Von Ho5 et al., 1977). To reduce this toxicity level to patient’s liver, another route was tried as transdermal therapeutic (through skin) in the form of slow drug release system. The slow drug release system !lled with these medicines in its reservoir was applied to patient’s hand as wearing the wristwatch for 24 h. The drug was delivered to patient through penetration into skin constitutes an additional series of di5usion and active transport steps. The area of peak before and after application in high performance liquid chromatography (HPLC) technique measured and their values are 4:00 × 107 and 4:30 × 107 , respectively. The increase in area of peak was also noted in two more patients using the same analysis technique and found that area of peak increases for them also after the application of slow drug release system. 4. Conclusions The following conclusions were drawn from this study: (i) Low cost, high mechanical strength commercial grade polyester !lm in the form of Sun control !lm can be used for development of nuclear track micro!lters.
(ii) By using sensibilization method, low Z-ion is able to produce cylindrical pores. (iii) A slow drug release system containing nuclear track micro!lter in the form of wrist watch was designed and developed for transdermal therapeutic purpose. (iv) Using high performance liquid chromatography technique the con!rmation of drug into patient’s serum was carried out . (v) This method is very useful for the patients, who are suffering from di5erent diseases in which drugs have maximum toxicity. References Flerov, G.N., 1984. Synthesis of super heavy elements and application of physics methods in adjacent !elds. Vestnik Akad. Nauk SSSR 4, 35–48. Gopalani, D., Kumar, S., Jodha, A.S., Singh, R., Khatri, P.K., Gopal, R., 2000. A novel method for production of polyester !lms based nuclear track micro!lters. Journal of Membrane Science 178, 93–98. Guo, S.L., Ganz, M., Fuest, M., Vater, P., Brandt, R., 1990. Further studies on the !ltration of liquids using kapton nuclear track micro!lters. Isotopenpraxis 26 (6), 271–275. Ishihara, K., Kabayoshi, M., Shinohara, I., 1983. Control of Insulin permeation through a polymer membrane with responsive function of glucose. Makromol. Chem. Rapid Commun. 4, 327. Varobiev, E.D., Ovchinnikov, V.V., Shestakov, V.D., 1989. Some peculiarities of use of the polymeric nuclear track membranes in clean rooms. JINR Report 18-89 –529. Von Ho5, O.D., Penta, J.S., Helman, L.J., Slavik, M., 1977. Incidence of drug related deaths secondary to high dose methotrexate and citrovorum factor administration. Cancer Treat Report 61, 745–748.
Radiation Measurements 36 (2003) 581 – 584 www.elsevier.com/locate/radmeas
Nuclear track micro!lters in controlled drug delivery against chronic skin disease D. Gopalani∗ , A.S. Jodha, S. Saravanan, S. Kumar Defence Laboratory, Ministry of Defence, Ratanada Palace, Jodhpur-342 011, India Received 21 October 2002; received in revised form 3 March 2003; accepted 7 May 2003
Abstract Nuclear track micro!lters have been developed for transdermal therapeutic system. The transdermal therapeutic method reduces the toxicity of the drug as compared to other conventional methods. For this purpose a slow drug release system containing the nuclear track micro!lter was developed. This device was applied to the patients su5ering from psoriasis and cellulites diseases. The delivery of the drug to the patient was con!rmed through high performance liquid chromatography. The preliminary results have shown that patients are responding to drugs with minimum toxicity. c 2003 Published by Elsevier Ltd. Keywords: SSNTD; Nuclear track micro!lter; Slow drug release system; Transdermal therapeutic system
1. Introduction
2. Experimental
The nuclear track micro!lter (NTMF) is a kind of novel material used successfully in various !elds such as precise separation of biological cells, !ltering polluted air steams, stabilizing beverages, microelectronics, pharmaceutical and waste water recycling, etc. (Flerov, 1984; Varobiev et al., 1989). These !lters are fabricated by exposing appropriate track forming insulating material in nuclear reactor or heavy ion accelerator and subsequently chemical etching process to enlarge the radiation damage in order to produce the “through hole”. In the present study, NTMFs have been developed by exposing polyester !lms to 28 Si ion and then sensitized followed by chemical etching with alkaline solution. The developed nuclear track micro!lters have been used as a drug release rate controlling membrane for transdermal therapeutic system. This method shows good zero order release kinetics, i.e. provides a constant rate of drug release over a de!ned period of time.
2.1. Production of NTMFs Indigenously available polyester !lm in the form of Sun control !lm has been used for the production of NTMFs. This !lm (thickness 25 m) was bombarded with 28 Si ion beam of energy 100 MeV in 14 MV pelletron at Tata Institute of Fundamental Research, Mumbai. For improvement of track etch rate (linear rate of chemical attack along the ion trajectory) of 28 Si ion in polyester !lm, a new pre-treatment procedure known as sensibilization of higher eGciency was developed (Gopalani et al., 2000). The sensibilzation of the irradiated !lms were carried out with dimethylformamide (DMF) solvent for half an hour at a temperature of 70◦ C. The DMF solvent treatment was followed by a solvent exchange with ethanol at room temperature for 15 min, since some solvent was not mixable with etchant. The sensibilized !lms were then etched in 5 N-NaOH at 50◦ C by means of thermostatic system. The pore size is controlled by the etching time. 2.2. Slow drug release system (SDRS)
∗
Corresponding author. Tel.: +91-291-567172; fax: +91-291-2511158. E-mail address: [email protected] (D. Gopalani). c 2003 Published by Elsevier Ltd. 1350-4487/03/$ - see front matter doi:10.1016/S1350-4487(03)00205-1
The developed !lters were !tted in pressure driven slow drug release system. This device has the shape of
582
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
Fig. 1. Slow drug release system.
wristwatch (Fig. 1). The !lters of pore size 2–3 m were kept to provide a uniform zero order deliver rate of drug in a long period. This device was applied to the patients su5ering from psoriasis and cellulites. The drug delivered through !lters by applying the pressure through a piston. The delivery of drug into the patient was con!rmed through high performance liquid chromatography of serum taken before and after the application of slow drug release system. The serum of patient before and after application (∼5 h) were taken and allowed to clot. Clotted blood was centrifuged for 10 min. at 1200 rpm before analysis then these (450 l in both case) mixed with internal standard (50 l aminopterin) in a glass tube. The mixture was vortexed after adding 500 l acetone and was centrifuged at 1000 rpm for 10 min. A volume of 600 l of the supernatant was
transferred to a second tube containing 600 l n-butanol and 800 l diethyl ether. This was mixed using the vortex mixer, then the mixture was transferred to a second microtube sizing 5 mm × 100 mm. This was centrifuged again at 1000 rpm for 10 min. The supernatant was discarded. The lower aqueous portion was directly injected on to the reverse phase C-18 column using 10 l Hamilton syringe. Peaks were identi!ed by using retention times compared with the internal standard. The retention time for drug (in this study only methotrexate was detected) was 9:09 min while 6:32 min for internal standard. Chromatography was performed at ambient temperature with detection at 313 nm. The area of peak in both cases, i.e. before and after application were taken for comparison point of view.
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
583
3. Results and discussion 3.1. Transdermal therapeutic system Administering 10 or 12 tablets to someone to help them manage their chronic illness may someday be a memory. In these days a novel method as Transdermal drug administration, which provides improve compliance, minimum side e5ects and more patient satisfaction has gained momentum. Transdermal, meaning ‘through the skin’ refers to a method of administering substances via a topical application to the skin. In this, substances are absorbed slowly through the skin and into the bloodstream. This route of absorption provides direct systemic administrations by delivering the compound through the skin in a time-released manner, which allows a direct access path to blood circulation. In this technique, controlled drug delivery occurs when a polymer, whether natural or synthetic, is judiciously combined with a drug or other active agent in such a way that the active agent is released from the material in a predesigned manner (Ishihara et al., 1983). The purpose behind controlling the drug delivery is to achieve more e5ective therapies while eliminating the potential for both under and overdosing. The goal of controlled release systems is to achieve a delivery pro!le that would yield a high blood level of the drug over a long period of time. With traditional tablets or injections, the drug level in the blood rises after each administration of the drug and then decreases until the next administration. There are three primarily mechanisms by which active agents can be released from a delivery system, namely, degradation, swelling and di5usion. In the present work, the drug delivery system was developed on the di5usion mechanism. Di5usion occurs when a drug or other active agent passes through the polymer that forms the controlled release device. In the present study, a transdermal therapeutic system has been designed in the shape of a wristwatch, where drug remains in a reservoir volume of 5-ml. This drug is covered and delivered to patient through developed nuclear track micro!lter made of polyester !lms. This material is selected due to its physical strength, transparency, chemically inert and free of leachable impurities. It also has an appropriate physical structure with minimal undesired aging and readily processable. 3.2. Nuclear track micro4lter The nuclear track micro!lters have been developed by bombarding these polyester !lms with 28 Si ions at Tata Institute of Fundamental Research, Mumbai. The 28 Si ion as M passing through polyester !lm leaves narrow (∼30–100 A) trails of damage. In conventional chemical etching etchant (NaOH/KOH) dissolve or degrade damaged region at a much higher rate (track etch rate, i.e. Vt ) than the undamaged material (bulk etch rate Vb ). The narrow damage trail is thus gouged out by the etchant, forming a hole. For cylin-
Fig. 2. Nuclear track micro!lter.
drical pores, the cone angle should be minimum, which can be obtained by larger value of Vt . The Vt of heavy ion is higher as its speci!c energy loss is more, which produces maximum damage along the trajectory. The 28 Si (lower atomic number) ion gives smaller track etch rate along the ion trajectory in the !lm after the conventional chemical etching. This smaller value of track etch rate cannot produce !ne pores of a nearly cylindrical shape. The DMF treatment enhanced the track etch rate of 28 Si ion because of similarity in solubility parameter of polyester !lm. Hence DMF penetrates into the polyester matrix and induces a crystallization of the amorphous region in the polyester. This e5ect produces more chemical attack along the ion trajectory and its value is !ve times more as compared to that of without any treatment. This enhanced value of track etch rate is comparable with speci!c energy loss of higher atomic number ion in polyester !lms. The pore size of the !lters was determined with the help of SEM. The NTMFs, of pore size ∼2–3 m were used in the present work (Fig. 2). The pore diameter was selected based on the required drug release rate from the slow drug release system. In the present study, the requirement of drug delivery to patient was 2:5 ml=day. The release rate measurement was carried out using Millipore assembly (Guo et al., 1990). In this assembly, a constant pressure was applied across the nuclear track micro!lter and Dow rate was measured. This pressure was same as the pressure maintained in the device using piston arrangement and its value is 6:3 mbar as overpressure. Based on the Dow rate measurement the release rate, i.e. 2:5 ml=day was optimized. The application of this device to each patient was given once in every week time (as described drug dosage). The reduction of these diseases starts after 2 weeks time. The other adverse e5ects were also checked through necessary tests were carried out simultaneously. A case history of each
584
D. Gopalani et al. / Radiation Measurements 36 (2003) 581 – 584
patient in which all the results of these tests were documented in a typed Performa was maintained. Based on these results, a con!rmation was made that this device does not produce any side e5ects due to these medicine via slow drug release system. 3.3. Application of NTMFs for chronic skin diseases The slow drug release system was used as transdermal therapeutic for the treatment of psoriasis and cellulites. These diseases are chronic skin diseases. For the treatment of these diseases, Methotrexate and Taxim-o (Ce!xime) drugs are given to patients, respectively. The toxicity of these drugs to liver is more and via this route its e5ect became even much more (Von Ho5 et al., 1977). To reduce this toxicity level to patient’s liver, another route was tried as transdermal therapeutic (through skin) in the form of slow drug release system. The slow drug release system !lled with these medicines in its reservoir was applied to patient’s hand as wearing the wristwatch for 24 h. The drug was delivered to patient through penetration into skin constitutes an additional series of di5usion and active transport steps. The area of peak before and after application in high performance liquid chromatography (HPLC) technique measured and their values are 4:00 × 107 and 4:30 × 107 , respectively. The increase in area of peak was also noted in two more patients using the same analysis technique and found that area of peak increases for them also after the application of slow drug release system. 4. Conclusions The following conclusions were drawn from this study: (i) Low cost, high mechanical strength commercial grade polyester !lm in the form of Sun control !lm can be used for development of nuclear track micro!lters.
(ii) By using sensibilization method, low Z-ion is able to produce cylindrical pores. (iii) A slow drug release system containing nuclear track micro!lter in the form of wrist watch was designed and developed for transdermal therapeutic purpose. (iv) Using high performance liquid chromatography technique the con!rmation of drug into patient’s serum was carried out . (v) This method is very useful for the patients, who are suffering from di5erent diseases in which drugs have maximum toxicity. References Flerov, G.N., 1984. Synthesis of super heavy elements and application of physics methods in adjacent !elds. Vestnik Akad. Nauk SSSR 4, 35–48. Gopalani, D., Kumar, S., Jodha, A.S., Singh, R., Khatri, P.K., Gopal, R., 2000. A novel method for production of polyester !lms based nuclear track micro!lters. Journal of Membrane Science 178, 93–98. Guo, S.L., Ganz, M., Fuest, M., Vater, P., Brandt, R., 1990. Further studies on the !ltration of liquids using kapton nuclear track micro!lters. Isotopenpraxis 26 (6), 271–275. Ishihara, K., Kabayoshi, M., Shinohara, I., 1983. Control of Insulin permeation through a polymer membrane with responsive function of glucose. Makromol. Chem. Rapid Commun. 4, 327. Varobiev, E.D., Ovchinnikov, V.V., Shestakov, V.D., 1989. Some peculiarities of use of the polymeric nuclear track membranes in clean rooms. JINR Report 18-89 –529. Von Ho5, O.D., Penta, J.S., Helman, L.J., Slavik, M., 1977. Incidence of drug related deaths secondary to high dose methotrexate and citrovorum factor administration. Cancer Treat Report 61, 745–748.