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Peptide loaded microparticles produced by the ASES process
Poster Session P2: Monday 16 September
Afthoughtherearedear&a&gas with the nasai route of administration, the low bioavailabilii of large hydrophilic mdecules is a drawback. By utilislng mucoadhesive delivery systems as caniers drug bioavailabifii could be improved through different mechanisms In a previous in-vitro study of difterent polymenc microsphere systems containing FlTCdextran (Mw 4.3 kDa) as a model drug, carbopol 934P (C934P) showed a superior mucoadheebn (1). This study inv@gated the effect of G934P, chitcean and non-mucosdhearve f&+oe mrcroy (as cpntrol) on the ~s~kinebcs and nasal broavarlabillty of F C-dextran tn male NZW Microspheres (FITCdextran 1 mg kg’, lo-12% w/w, 33.6 pm o.d.) were admitist~, lntranasaky (in.) into cne nostrfl using a specially designed device. FlTGdextran isotonic solutbn (1 mg Qt) was afso administered
(Tabfe 1). Table 1 Terminal half-lie, AlJCs 8 Bloavakabilky of FITCDextran. Mkms&am 6.n.) ( i.v.). chitooan c831P Lsctces
ttn
43.9i 10.6
FITCDextran
(1)
88.8*
54.5
110.6G2A
24O.Qt13D.Q
187.8de.2
17.4*&4
23.7 * 4.0
61.4 * 20.4
lC0
9.1 t3.8
12.6+4.5
327 t 13.2
bioavailability was signiflly
higher
M. Abdel-Hameed and I.W. Kellaway, Rot. STS Pubfish., Cardll(l995) p 39.
from C934P
4ft1 Ukaps Cod
Clenbuterol (CBL), a pa-adrenergic agonist, has been misused for its growth promoting effects in animals used for food production. CBL residues have caused food poisoning in the consumer, necessitating residue monitoring. At present, an enzyme immunoassay using polyclonal antibodies to CBL, raised in rabbits, is commonly used to quantify CBL residues. However, the production of these antibodies involves repeated subcutaneous (s/c) injections of a clenbuterol-transferrin conjugate (CBL-Tfn) with Quil A as an adjuvant. Poly(lactide-co-glycollde)t (PLGA) and polymethylmethacrylate (PMMA) colloidal polymeric systems are promising vaccine adjuvants. To improve the method of CBL antibody production, CBL-Tfn associated PLGA and PMMA nanoparticles were investigated as adjuvants. Their efficacy in viva was measured in terms of the anti-CBL titres generated, as determined by an ELISA, following their s/c administration to mice (n=4 per group). Over the 15 week experimental period the positive control group (the current method for raising CBL antibodies) required four immunizations, on days 0, 21, 66 and 99, to achieve high antibody titres. Despite three immunizations (days 0, 21 and 66) PMMA adsorbed CBL-Tfn did not result in significantly higher titres than the control group. However, with only two immunizations on days 0 and 21, PLGA nanoencapsulated CBL-Tfn. administered with Quil A, resulted in antibody titres that were consistently higher than those of the positive control group. Furthermore, the group receiving this PLGA system was the only one in which all 4 mice responded at each of the sampling times (days 28,51,84 and 106). In conclusion, a PLGA nanoparticulate system had clear immunological advantages over the current method of raising antibodies to CBL. It resulted In improved antibody tires with fewer immunizations, and in our sample generated a 100% response rate in mice. This model could be applied to facilitate ELISA development for other haptens. 1, Eldridge, J.H. et al (1991) Molecular Immunology 28: 287- 294
The low dissolution rate of many drugs can cause difficulty in their use. Drug dissolution rate is mainly affected by two parameters, the effective surface area and the saturation solubility of the drug in the dissolution medium. A possible method of improving the dissolution rate of poorly soluble drugs would be to coat each particle of drug with a thin layer of a hydrophilic compound. This should ensure wetting of the drug particle and give a large effective surface area. The objective of the present work was to investigate whether microencapsulation of poorly soluble drugs with hydrophilic polymers could be used to increase their dissolution rate. The lipophilic drugs used were the steroids hydrocortisone, 17-p-estradiol and prednisolone. The coating materials used were the hydrophilic polymers chitosan, dextran. sodium carboxymethylcellulose and hydroxypropylmethylcellulose. Microencapsulation was carried out by the spray-drying technique. The shape of the microparticles as well as the size distribution was affected by the coating material used. The particle size distribution of the microparticles was narrow with the mean particle size ranging from 3-8 urn. DTA graphs did not shown crystal change in the steroids after microparticle formation. Dissolution testing showed a considerable improvement in the dissolution rate of all the steroids after microencapsulation. For hydrocortisone the best results were obtained with dextran, NaCMC and chitosan. with dextran being marginally the best, HPMC also increased the dissolution rate but to a less degree. Chitosan did not improve the dissolution rate of 17-p-estradiol but the other polymers did, with HPMC giving the best results. All the polymers improved the dissolution rate of prednisolone to an equal extent. The results indicate that it is possible to improve the dissolution rate of poorly soluble drugs such as steroids by microencapsulating with hvdrophilic polymers
The Aerosol Solvent Extraction System (ASES, (11) is a method to produce microparticles utilizing the extraction properties of supercritical carbon dioxide. The properties of the manufactured microparticles are influenced by physico-chemical characteristics of the used biodegradable polymers as well as by varying the microparticle formulation [2.3]. The aim of the present study was to determine the influence of different drug loadings, the molecular weight of the used polymer and the addition of lecithin on the characteristics of microparticles. As model drug a pentapeptide (Thymopentine) was used. The employed polymers were two coblockpolymers of poty-d,l-lactide-co-glycolide with different chain length. Using an n-factorial design micropanicles were produced by means of the ASES process. The particles were characterized using laser diffraction measurement and scanning electron microscopy respectively. Furthermore the release profiles, the content of residual solvent and contact angle measurements of the produced batches were examined. With increasing molecularweightof the polymers the average particle size of the microparticles decreased. The particle size was influenced by the amount of loaded drug: the higher the concentration of added thymopentine the smaller the size of the particles. The contact angle of the microparticles was influenced by the addition of small quantities of lecithin as well as by the amount of incorporated drug. There was a relation between lecithin added and drug loading on the release profiles of the microparticles.
1. Muller, B.W. and Fischer, W., U.S. Patent 6043,280 (1991) 2. Ruchatz, F., Bleich, J., Miiller, B. W., Proc. Contr. Rel. Bioact. Mat.,(l994) 3. Ruchatz, F. MOller,B.W., 42ndAnnual CongressoftheAPV, L902,(1996)
Afthoughtherearedear&a&gas with the nasai route of administration, the low bioavailabilii of large hydrophilic mdecules is a drawback. By utilislng mucoadhesive delivery systems as caniers drug bioavailabifii could be improved through different mechanisms In a previous in-vitro study of difterent polymenc microsphere systems containing FlTCdextran (Mw 4.3 kDa) as a model drug, carbopol 934P (C934P) showed a superior mucoadheebn (1). This study inv@gated the effect of G934P, chitcean and non-mucosdhearve f&+oe mrcroy (as cpntrol) on the ~s~kinebcs and nasal broavarlabillty of F C-dextran tn male NZW Microspheres (FITCdextran 1 mg kg’, lo-12% w/w, 33.6 pm o.d.) were admitist~, lntranasaky (in.) into cne nostrfl using a specially designed device. FlTGdextran isotonic solutbn (1 mg Qt) was afso administered
(Tabfe 1). Table 1 Terminal half-lie, AlJCs 8 Bloavakabilky of FITCDextran. Mkms&am 6.n.) ( i.v.). chitooan c831P Lsctces
ttn
43.9i 10.6
FITCDextran
(1)
88.8*
54.5
110.6G2A
24O.Qt13D.Q
187.8de.2
17.4*&4
23.7 * 4.0
61.4 * 20.4
lC0
9.1 t3.8
12.6+4.5
327 t 13.2
bioavailability was signiflly
higher
M. Abdel-Hameed and I.W. Kellaway, Rot. STS Pubfish., Cardll(l995) p 39.
from C934P
4ft1 Ukaps Cod
Clenbuterol (CBL), a pa-adrenergic agonist, has been misused for its growth promoting effects in animals used for food production. CBL residues have caused food poisoning in the consumer, necessitating residue monitoring. At present, an enzyme immunoassay using polyclonal antibodies to CBL, raised in rabbits, is commonly used to quantify CBL residues. However, the production of these antibodies involves repeated subcutaneous (s/c) injections of a clenbuterol-transferrin conjugate (CBL-Tfn) with Quil A as an adjuvant. Poly(lactide-co-glycollde)t (PLGA) and polymethylmethacrylate (PMMA) colloidal polymeric systems are promising vaccine adjuvants. To improve the method of CBL antibody production, CBL-Tfn associated PLGA and PMMA nanoparticles were investigated as adjuvants. Their efficacy in viva was measured in terms of the anti-CBL titres generated, as determined by an ELISA, following their s/c administration to mice (n=4 per group). Over the 15 week experimental period the positive control group (the current method for raising CBL antibodies) required four immunizations, on days 0, 21, 66 and 99, to achieve high antibody titres. Despite three immunizations (days 0, 21 and 66) PMMA adsorbed CBL-Tfn did not result in significantly higher titres than the control group. However, with only two immunizations on days 0 and 21, PLGA nanoencapsulated CBL-Tfn. administered with Quil A, resulted in antibody titres that were consistently higher than those of the positive control group. Furthermore, the group receiving this PLGA system was the only one in which all 4 mice responded at each of the sampling times (days 28,51,84 and 106). In conclusion, a PLGA nanoparticulate system had clear immunological advantages over the current method of raising antibodies to CBL. It resulted In improved antibody tires with fewer immunizations, and in our sample generated a 100% response rate in mice. This model could be applied to facilitate ELISA development for other haptens. 1, Eldridge, J.H. et al (1991) Molecular Immunology 28: 287- 294
The low dissolution rate of many drugs can cause difficulty in their use. Drug dissolution rate is mainly affected by two parameters, the effective surface area and the saturation solubility of the drug in the dissolution medium. A possible method of improving the dissolution rate of poorly soluble drugs would be to coat each particle of drug with a thin layer of a hydrophilic compound. This should ensure wetting of the drug particle and give a large effective surface area. The objective of the present work was to investigate whether microencapsulation of poorly soluble drugs with hydrophilic polymers could be used to increase their dissolution rate. The lipophilic drugs used were the steroids hydrocortisone, 17-p-estradiol and prednisolone. The coating materials used were the hydrophilic polymers chitosan, dextran. sodium carboxymethylcellulose and hydroxypropylmethylcellulose. Microencapsulation was carried out by the spray-drying technique. The shape of the microparticles as well as the size distribution was affected by the coating material used. The particle size distribution of the microparticles was narrow with the mean particle size ranging from 3-8 urn. DTA graphs did not shown crystal change in the steroids after microparticle formation. Dissolution testing showed a considerable improvement in the dissolution rate of all the steroids after microencapsulation. For hydrocortisone the best results were obtained with dextran, NaCMC and chitosan. with dextran being marginally the best, HPMC also increased the dissolution rate but to a less degree. Chitosan did not improve the dissolution rate of 17-p-estradiol but the other polymers did, with HPMC giving the best results. All the polymers improved the dissolution rate of prednisolone to an equal extent. The results indicate that it is possible to improve the dissolution rate of poorly soluble drugs such as steroids by microencapsulating with hvdrophilic polymers
The Aerosol Solvent Extraction System (ASES, (11) is a method to produce microparticles utilizing the extraction properties of supercritical carbon dioxide. The properties of the manufactured microparticles are influenced by physico-chemical characteristics of the used biodegradable polymers as well as by varying the microparticle formulation [2.3]. The aim of the present study was to determine the influence of different drug loadings, the molecular weight of the used polymer and the addition of lecithin on the characteristics of microparticles. As model drug a pentapeptide (Thymopentine) was used. The employed polymers were two coblockpolymers of poty-d,l-lactide-co-glycolide with different chain length. Using an n-factorial design micropanicles were produced by means of the ASES process. The particles were characterized using laser diffraction measurement and scanning electron microscopy respectively. Furthermore the release profiles, the content of residual solvent and contact angle measurements of the produced batches were examined. With increasing molecularweightof the polymers the average particle size of the microparticles decreased. The particle size was influenced by the amount of loaded drug: the higher the concentration of added thymopentine the smaller the size of the particles. The contact angle of the microparticles was influenced by the addition of small quantities of lecithin as well as by the amount of incorporated drug. There was a relation between lecithin added and drug loading on the release profiles of the microparticles.
1. Muller, B.W. and Fischer, W., U.S. Patent 6043,280 (1991) 2. Ruchatz, F., Bleich, J., Miiller, B. W., Proc. Contr. Rel. Bioact. Mat.,(l994) 3. Ruchatz, F. MOller,B.W., 42ndAnnual CongressoftheAPV, L902,(1996)