Journal of Microencapsulation Micro and Nano Carriers
ISSN: 0265-2048 (Print) 1464-5246 (Online) Journal homepage: http://www.tandfonline.com/loi/imnc20
Cyclophosphamide loaded albumin microspheres II. Release characteristics I. Vural, H. S. Kasl, A. A. Hincal & G. Cavé To cite this article: I. Vural, H. S. Kasl, A. A. Hincal & G. Cavé (1990) Cyclophosphamide loaded albumin microspheres II. Release characteristics, Journal of Microencapsulation, 7:4, 511-516 To link to this article: http://dx.doi.org/10.3109/02652049009040474
Published online: 27 Sep 2008.
Submit your article to this journal
Article views: 14
View related articles
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=imnc20 Download by: [University of California, San Diego]
Date: 07 November 2015, At: 21:16
J. MICROENCAPSULATION,
1990, VOL. 7,
NO.
4, 511-516
Cyclophosphamide loaded albumin microspheres 11. Release characteristics
Downloaded by [University of California, San Diego] at 21:16 07 November 2015
i. VURAL, H . S. KAS, A. A. HINCAL
and G. CAVE?
Pharmaceutical Technology Department, Faculty of Pharmacy, University of Hacettepe, 06100 Ankara, Turkey t Laboratoire de Pharmacie Galhique, Facultk des Sciences Pharmaceutiques, 2 Boulevard Tonnelk, Boive Postall 3213, 31400 Tours, France (Received 9 February 1990; accepted 6 March 1990)
The purpose of this investigation was to evaluate the release characteristics of cyclophosphamide (CP) from glutaraldehyde stabilized human serum albumin microspheres, and to study the effect of the extent of cross-linking, the amount of the stabilizing agent and the size of the microspheres on the in vitro release of CP. Microspheres were prepared by emulsion polymerization method using two different volumes ( 0 1 and 0.7 ml) ofglutaraldehyde solution (25 per cent) and two different crosslinking durations (1 5 min and 1 h). The resulting mean particle size of the microspheres also varied between 2.5 pm and 3.7 p n . The total CP content in microspheres was analysed from the surface drug and the entrapped drug.
Introduction T h e selective delivery of drugs to specific target organs in the body reduces the systemic dose of a given drug while still achieving the effective local concentration. This results in a reduction of unwanted side-effects. One approach to target chemotherapeutics is the entrapment of the agents within a colloidal carrier. Albumin microspheres have been investigated for changing the biodistribution of anticancer drugs (Sugibayashi et al. 1977, Widder et al. 1979, Tomlinson 1983). T h e active substance of this investigation, cyclophosphamide (CP) belongs to the group of medicines called the alkylating agents. CP interferes with the growth of cancer cells which are eventually destroyed. Since side-effects of CP are frequently dose related, by incorporating a low dose of CP in human serum albumin (HSA) microspheres, the normal body cells are not affected while the tumour cells are destroyed. I t has also been demonstrated that due to its lysosomotropic nature, drugassociated albumin microspheres may be useful for treating cancer cells otherwise resistant to the drug (Widder et al. 1983). T h e release of drugs from microspheres has been observed to be dependent on a number of factors including the size, the type and the amount of the matrix material, the position of the drug in the microsphere, the extent and nature of the crosslinking agent and release environment (Tomlinson et al. 1984). T h e aim of this investigation was to study the influence of the extent of crosslinking and the amount of the stabilizing material on in vitro release characteristics of CP from HSA microspheres.
Experimental details Materials T h e active substance was cyclophosphamide (Ibrahim-Etem, Istanbul, Turkey). T h e matrix material is human serum albumin (Rehringwerke AG, Marburg, FRG). 0265-2048/90 $3.00 0 1990 Taylor & Francis Ltd.
i. Vural et al.
512
Downloaded by [University of California, San Diego] at 21:16 07 November 2015
T h e hardening agent used is glutaraldehyde (25 per cent aqueous solution) (Merck). All substances were used without further purification.
Methods Preparation of H S A microspheres. Cyclophosphamide microspheres were prepared using a modification of the methods of Scheffel et al. (1972), Giirkan et al. (1 986) and iveri et al. (1989). An aqueous solution, containing 25 per cent w/v HSA and 37.5 mg CP, was mixed with 130ml cottonseed oil and homogenized. T h e resulting homogenate was added into continuously stirred cottonseed oil at 25°C. T h e albumin microspheres were washed with diethyl ether to remove the oil phase and the microspheres were stabilized by using two different volumes (0.1 and 0.7 ml) of glutaraldehyde solution (25 per cent) and two different crosslinking durations (1 5 min and 1 h). T h e resulting microspheres were kept at 4°C after drying (table 1).
Assay of C P . C P was assayed by reading the colour intensity of the complex formed by 4-(4-nitrobenzyl)pyridine (Suzuki et al. 1986). Recovery of microspheres. T h e total and entrapped drug content of the microspheres were determined using unwashed and four times washed microspheres, respectively. T h e following relationship was used to determine the total recovery of C P from albumin microspheres: Total recovery =
drug content of unwashed microspheres x 100 mg C P per mg of albumin started
S i z e distribution of microspheres. T h e particle size distributi.>n of HSA microspheres of C P were obtained by Coulter Counter-Multisizer (Coulter Electronics). T h e sizes of different codes of microspheres were found to range betwetii 2.5 pm and 3.7 pm. Determination of C P content of H S A microspherey. T h e total drug content was obtained by using the method of Gupta et al. (1 989). By this method both the surface and the entrapped drug amount was calculated (table 2). Surface drug: 1 rnl 0.9 per cent sodium chloride solution and Tween 80 was added onto l0rng CP microspheres. This suspension was kept in an ultrasonic bath for 5 min and then centrifuged for 10 min at 2000g. T h e clear liquid layer was pipetted and the same procedure was applied three more times to the supernatant. All the clear solutions were mixed and the C P content was assayed. Entrapped drug: 5 ml 0.5 M acetic acid was added to the rnicrospheres and washed four times. They were kept overnight at 4°C. T h e next day this microsphere suspension was kept at ultrasonic bath for 20min and then Table 1.
Codes of microspheres used in in vztro release studies.
Stabilizing agent
Concentration of the stabilizing agent (ml)
Duration of stabilization (min)
Codes
______-._
ISSN: 0265-2048 (Print) 1464-5246 (Online) Journal homepage: http://www.tandfonline.com/loi/imnc20
Cyclophosphamide loaded albumin microspheres II. Release characteristics I. Vural, H. S. Kasl, A. A. Hincal & G. Cavé To cite this article: I. Vural, H. S. Kasl, A. A. Hincal & G. Cavé (1990) Cyclophosphamide loaded albumin microspheres II. Release characteristics, Journal of Microencapsulation, 7:4, 511-516 To link to this article: http://dx.doi.org/10.3109/02652049009040474
Published online: 27 Sep 2008.
Submit your article to this journal
Article views: 14
View related articles
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=imnc20 Download by: [University of California, San Diego]
Date: 07 November 2015, At: 21:16
J. MICROENCAPSULATION,
1990, VOL. 7,
NO.
4, 511-516
Cyclophosphamide loaded albumin microspheres 11. Release characteristics
Downloaded by [University of California, San Diego] at 21:16 07 November 2015
i. VURAL, H . S. KAS, A. A. HINCAL
and G. CAVE?
Pharmaceutical Technology Department, Faculty of Pharmacy, University of Hacettepe, 06100 Ankara, Turkey t Laboratoire de Pharmacie Galhique, Facultk des Sciences Pharmaceutiques, 2 Boulevard Tonnelk, Boive Postall 3213, 31400 Tours, France (Received 9 February 1990; accepted 6 March 1990)
The purpose of this investigation was to evaluate the release characteristics of cyclophosphamide (CP) from glutaraldehyde stabilized human serum albumin microspheres, and to study the effect of the extent of cross-linking, the amount of the stabilizing agent and the size of the microspheres on the in vitro release of CP. Microspheres were prepared by emulsion polymerization method using two different volumes ( 0 1 and 0.7 ml) ofglutaraldehyde solution (25 per cent) and two different crosslinking durations (1 5 min and 1 h). The resulting mean particle size of the microspheres also varied between 2.5 pm and 3.7 p n . The total CP content in microspheres was analysed from the surface drug and the entrapped drug.
Introduction T h e selective delivery of drugs to specific target organs in the body reduces the systemic dose of a given drug while still achieving the effective local concentration. This results in a reduction of unwanted side-effects. One approach to target chemotherapeutics is the entrapment of the agents within a colloidal carrier. Albumin microspheres have been investigated for changing the biodistribution of anticancer drugs (Sugibayashi et al. 1977, Widder et al. 1979, Tomlinson 1983). T h e active substance of this investigation, cyclophosphamide (CP) belongs to the group of medicines called the alkylating agents. CP interferes with the growth of cancer cells which are eventually destroyed. Since side-effects of CP are frequently dose related, by incorporating a low dose of CP in human serum albumin (HSA) microspheres, the normal body cells are not affected while the tumour cells are destroyed. I t has also been demonstrated that due to its lysosomotropic nature, drugassociated albumin microspheres may be useful for treating cancer cells otherwise resistant to the drug (Widder et al. 1983). T h e release of drugs from microspheres has been observed to be dependent on a number of factors including the size, the type and the amount of the matrix material, the position of the drug in the microsphere, the extent and nature of the crosslinking agent and release environment (Tomlinson et al. 1984). T h e aim of this investigation was to study the influence of the extent of crosslinking and the amount of the stabilizing material on in vitro release characteristics of CP from HSA microspheres.
Experimental details Materials T h e active substance was cyclophosphamide (Ibrahim-Etem, Istanbul, Turkey). T h e matrix material is human serum albumin (Rehringwerke AG, Marburg, FRG). 0265-2048/90 $3.00 0 1990 Taylor & Francis Ltd.
i. Vural et al.
512
Downloaded by [University of California, San Diego] at 21:16 07 November 2015
T h e hardening agent used is glutaraldehyde (25 per cent aqueous solution) (Merck). All substances were used without further purification.
Methods Preparation of H S A microspheres. Cyclophosphamide microspheres were prepared using a modification of the methods of Scheffel et al. (1972), Giirkan et al. (1 986) and iveri et al. (1989). An aqueous solution, containing 25 per cent w/v HSA and 37.5 mg CP, was mixed with 130ml cottonseed oil and homogenized. T h e resulting homogenate was added into continuously stirred cottonseed oil at 25°C. T h e albumin microspheres were washed with diethyl ether to remove the oil phase and the microspheres were stabilized by using two different volumes (0.1 and 0.7 ml) of glutaraldehyde solution (25 per cent) and two different crosslinking durations (1 5 min and 1 h). T h e resulting microspheres were kept at 4°C after drying (table 1).
Assay of C P . C P was assayed by reading the colour intensity of the complex formed by 4-(4-nitrobenzyl)pyridine (Suzuki et al. 1986). Recovery of microspheres. T h e total and entrapped drug content of the microspheres were determined using unwashed and four times washed microspheres, respectively. T h e following relationship was used to determine the total recovery of C P from albumin microspheres: Total recovery =
drug content of unwashed microspheres x 100 mg C P per mg of albumin started
S i z e distribution of microspheres. T h e particle size distributi.>n of HSA microspheres of C P were obtained by Coulter Counter-Multisizer (Coulter Electronics). T h e sizes of different codes of microspheres were found to range betwetii 2.5 pm and 3.7 pm. Determination of C P content of H S A microspherey. T h e total drug content was obtained by using the method of Gupta et al. (1 989). By this method both the surface and the entrapped drug amount was calculated (table 2). Surface drug: 1 rnl 0.9 per cent sodium chloride solution and Tween 80 was added onto l0rng CP microspheres. This suspension was kept in an ultrasonic bath for 5 min and then centrifuged for 10 min at 2000g. T h e clear liquid layer was pipetted and the same procedure was applied three more times to the supernatant. All the clear solutions were mixed and the C P content was assayed. Entrapped drug: 5 ml 0.5 M acetic acid was added to the rnicrospheres and washed four times. They were kept overnight at 4°C. T h e next day this microsphere suspension was kept at ultrasonic bath for 20min and then Table 1.
Codes of microspheres used in in vztro release studies.
Stabilizing agent
Concentration of the stabilizing agent (ml)
Duration of stabilization (min)
Codes
______-._
