María del Rosario Aberturas - Academia.edu (original) (raw)
Papers by María del Rosario Aberturas
Toxicology for the Health and Pharmaceutical Sciences
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Toxicology for the Health and Pharmaceutical Sciences
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Journal of Drug Targeting, 2013
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European Journal of Pharmaceutical Sciences, 2001
The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycapr... more The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycaprolactone nanoparticles (CyA-NP) was assessed in vitro and in vivo and compared to the effects caused by free drug (Sandimmun. The in vivo study included four groups (12 Wistar rats each) receiving oral CyA (10 mg/kg/day for 3 days) as an emulsion of Sandimmun in whole milk or CyA-NP and equivalent doses of empty NP or cremophor in milk as controls. CyA concentrations in blood, urine, liver, spleen and kidney at 24 h post-dosing were measured by fluorescence polarization immunoassay (FPIA). The nephrotoxicity induced by each drug treatment was determined by measuring creatinine plasma levels, malonyl dialdehyde production, and H(2)O(2) and reduced glutathione contents in glomeruli. On the other hand, the immunosuppressive effect was estimated in vivo by incubating lymphocyte suspensions obtained from CyA-, CyA-NP- and control-treated rats, as well as in vitro on lymphocyte suspensions from non-treated healthy animals. Significantly higher blood, urine and tissue levels were achieved with CyA-NP compared to free CyA. However, no changes in creatinine plasma levels were detected due to either CyA or CyA-NP treatment. Only the production of H(2)O(2) in the glomeruli exhibited a significant increase as compared to control groups, but no differences could be ascribed to the different drug treatments. In vivo, the immunosuppressive activity was also comparable for both drug treatments. In contrast, CyA-NP showed a better drug uptake in vitro at concentrations above 25 microM. No immunosuppression was detected in control groups. NP improve the oral bioavailability of CyA and its uptake by lymphocytes in vitro above 25 microM. On the contrary, specific immunosuppression and adverse effects were not simultaneously increased. Further studies are needed to clarify the results.
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Journal of Pharmaceutical Sciences, 1996
Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparti... more Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve bioavailability after oral administration. In this study a composite rotational experimental design was used to evaluate the joint influence of five formulation variables: temperature of the aqueous phase, needle gauge, volume of the organic phase, and the amounts of polymer and surfactant on the micromeritic characteristics of the CyA-loaded NP obtained by the method of Fessi et al. The percentage of drug encapsulated in the NP was also evaluated for each formulation, and the yield, which was expressed as the ratio between the experimentally measured quantity of drug in the formulation and the theoretical content, was determined because CyA undergoes surface adsorption. Potential variables such as stirring speed (500 rpm), final drug concentration (100 μg/mL), or injection rates (GRi = 0.379 mL/s) were maintained constant. The ANOVA corresponding to the experimental design showed that the amounts of polymer and surfactant, and the diameter of the needle used in the preparation of NP, significantly affected the percentage of entrapped drug (r2 = 0.8916). The mean particle size, was significantly affected by all the formulation variables tested except for the amount of surfactant dissolved in the external aqueous phase (r2 = 0.9518). Neither the yield (mean value of 99.61%) nor the size distribution parameters (polydispersity and coefficient of variation) presented good correlation coefficients for the equations obtained, although some variables showed statistical significance. A second study was carried out to investigate the effects on the drug-loaded NP characteristics of varying the global injection rates (GRi) for the organic phase into the aqueous medium. The results showed a dramatic decrease in both particle size and drug incorporation in the carrier as the rate of mixing increased. From the results of both the experimental design and the second study, a theoretical model for nanoparticle formation is proposed that considers the most significant variables, and an empirical relationship to predict mean particle size is presented. Thus, particle size can be controlled by the injection rates (GRi), the needle gauge, and the polymer concentration.
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Journal of Microencapsulation, 1997
ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle sus... more ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle suspensions, stored at 8 and 25 degrees C. The stability of freeze-dried samples was also investigated. Nanoparticles (NP) of poly-sigma-caprolactone (P sigma CL), a biodegradable polymer, were obtained by a modified nanoprecipitation method. A central composite experimental design was used to investigate the simultaneous effect of technological factors (temperature of the aqueous phase and needle gauge) and formulation variables (volume of acetone and the amount of polymer and surfactant). The effect of these variables on the stability of the 100-220 nm particles obtained was evaluated. The percentage of cyclosporin A (CyA) encapsulated in the NP suspensions stored at 8 and 25 degrees C for at least 3 months remained unaltered. Moreover, there was no change in the size of NP. After 4 months storage, the physical stability of the preparation was affected. NP aggregates could be observed by light microscopy. Reconstituted freeze-dried preparations showed a mean increase of 1% in the incorporated drug and also a considerable increase in mean size and size distribution. Additional experiments investigated the effect of freezing temperature (-70 and -196 degrees C) and of 5, 10 and 20% (w/v) cryoprotector (mannitol, sorbitol, glucose and threalose) on 100 nm particles. The addition of glucose and threalose at concentrations > 10% permitted adequate reconstitution of the freeze-dried product with conservation of the encapsulated CyA.
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Drug Development and Industrial Pharmacy, 1989
ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° ... more ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° C is studied “in vitro”. It is noted that as plasma/liposomal suspension ratio is increased, the porcentage of drug retained in the liposomes decreases. Just so, independently from the dosage form, the efflux rate is maximum during the first hour and then falls gradually and in a non linear way. The physical state of the bilayer is a conditioning factor in the release of the encapsulated drug. The dosage forms of egg yolk phosphatidylcholine (EYPC) and of dimiristoylphosphatidylcholine (DMPC) quickly release digitoxin; while dipalmitoylphosphatidylcholine (DPPC) retains 54% of the entrapped drug after 24 hours incubation with 80% of plasma at 37°C. The inclusion of cholesterol (CHOL) and dicetylphosphate (DCP) in the liposomal matrix neither aids in the incorporation of digitoxin to the liposomes, nor augments the stability of the system in the human plasma.
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Drug Development and Industrial Pharmacy, 1994
ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 g... more ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer. In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.
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International Journal of Pharmaceutics, 1992
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European Journal of Pharmaceutical Sciences, 2001
The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycapr... more The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycaprolactone nanoparticles (CyA-NP) was assessed in vitro and in vivo and compared to the effects caused by free drug (Sandimmun. The in vivo study included four groups (12 Wistar rats each) receiving oral CyA (10 mg/kg/day for 3 days) as an emulsion of Sandimmun in whole milk or CyA-NP and equivalent doses of empty NP or cremophor in milk as controls. CyA concentrations in blood, urine, liver, spleen and kidney at 24 h post-dosing were measured by fluorescence polarization immunoassay (FPIA). The nephrotoxicity induced by each drug treatment was determined by measuring creatinine plasma levels, malonyl dialdehyde production, and H(2)O(2) and reduced glutathione contents in glomeruli. On the other hand, the immunosuppressive effect was estimated in vivo by incubating lymphocyte suspensions obtained from CyA-, CyA-NP- and control-treated rats, as well as in vitro on lymphocyte suspensions from non-treated healthy animals. Significantly higher blood, urine and tissue levels were achieved with CyA-NP compared to free CyA. However, no changes in creatinine plasma levels were detected due to either CyA or CyA-NP treatment. Only the production of H(2)O(2) in the glomeruli exhibited a significant increase as compared to control groups, but no differences could be ascribed to the different drug treatments. In vivo, the immunosuppressive activity was also comparable for both drug treatments. In contrast, CyA-NP showed a better drug uptake in vitro at concentrations above 25 microM. No immunosuppression was detected in control groups. NP improve the oral bioavailability of CyA and its uptake by lymphocytes in vitro above 25 microM. On the contrary, specific immunosuppression and adverse effects were not simultaneously increased. Further studies are needed to clarify the results.
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Journal of Microencapsulation, 2002
The present study describes the development of a new cyclosporine formulation based on polycaprol... more The present study describes the development of a new cyclosporine formulation based on polycaprolactone (PCL) microspheres (MS) prepared by the solvent evaporation method. Ternary phase diagrams were used to identify the domains where MS were formed. The application of central composite designs established the influence of several technological (stirring speed) and formulation factors (polymer and surfactant amounts, and organic solvent volume) on the size of PCL MS. Cyclosporine-loaded MS of a size around 2.5 microm were prepared and characterized. The stability of the systems, either alone or loaded with cyclosporine, stored at 8 degrees C and room temperature (RT) was assessed as well. Freeze-drying was evaluated as an alternative method to achieve long-term stability. The experimental design showed that the stirring speed and the organic phase volume were the only parameters significantly affecting the MS size. Experimental conditions selected to obtain CyA-loaded MS of 2.5 microm resulted in a high entrapment percentage (98.4 +/- 0.66%) with the drug dissolved or molecularly dispersed within the dense polymeric matrix of MS. After 12 months of storage at 8 degrees C and RT, PCL MS remained physically stable, although the crystallinity of the polymer increased by 35% upon storage at both temperatures. Freeze-drying studies revealed that MS could be successfully lyophilized in the absence of cryoprotectants without significant changes of the drug entrapment; however, the presence of at least 5% cryoprotectant was essential to keep the initial particle size. Therefore, a stable MS-based CyA formulation was easily prepared and characterized. This formulation offer the possibility of CyA administration through different routes.
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Journal of Pharmaceutical Sciences, 1996
Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparti... more Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve bioavailability after oral administration. In this study a composite rotational experimental design was used to evaluate the joint influence of five formulation variables: temperature of the aqueous phase, needle gauge, volume of the organic phase, and the amounts of polymer and surfactant on the micromeritic characteristics of the CyA-loaded NP obtained by the method of Fessi et al. The percentage of drug encapsulated in the NP was also evaluated for each formulation, and the yield, which was expressed as the ratio between the experimentally measured quantity of drug in the formulation and the theoretical content, was determined because CyA undergoes surface adsorption. Potential variables such as stirring speed (500 rpm), final drug concentration (100 μg/mL), or injection rates (GRi = 0.379 mL/s) were maintained constant. The ANOVA corresponding to the experimental design showed that the amounts of polymer and surfactant, and the diameter of the needle used in the preparation of NP, significantly affected the percentage of entrapped drug (r2 = 0.8916). The mean particle size, was significantly affected by all the formulation variables tested except for the amount of surfactant dissolved in the external aqueous phase (r2 = 0.9518). Neither the yield (mean value of 99.61%) nor the size distribution parameters (polydispersity and coefficient of variation) presented good correlation coefficients for the equations obtained, although some variables showed statistical significance. A second study was carried out to investigate the effects on the drug-loaded NP characteristics of varying the global injection rates (GRi) for the organic phase into the aqueous medium. The results showed a dramatic decrease in both particle size and drug incorporation in the carrier as the rate of mixing increased. From the results of both the experimental design and the second study, a theoretical model for nanoparticle formation is proposed that considers the most significant variables, and an empirical relationship to predict mean particle size is presented. Thus, particle size can be controlled by the injection rates (GRi), the needle gauge, and the polymer concentration.
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European Journal of Pharmaceutics and Biopharmaceutics, 2000
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Journal of Microencapsulation, 1997
ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle sus... more ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle suspensions, stored at 8 and 25 degrees C. The stability of freeze-dried samples was also investigated. Nanoparticles (NP) of poly-sigma-caprolactone (P sigma CL), a biodegradable polymer, were obtained by a modified nanoprecipitation method. A central composite experimental design was used to investigate the simultaneous effect of technological factors (temperature of the aqueous phase and needle gauge) and formulation variables (volume of acetone and the amount of polymer and surfactant). The effect of these variables on the stability of the 100-220 nm particles obtained was evaluated. The percentage of cyclosporin A (CyA) encapsulated in the NP suspensions stored at 8 and 25 degrees C for at least 3 months remained unaltered. Moreover, there was no change in the size of NP. After 4 months storage, the physical stability of the preparation was affected. NP aggregates could be observed by light microscopy. Reconstituted freeze-dried preparations showed a mean increase of 1% in the incorporated drug and also a considerable increase in mean size and size distribution. Additional experiments investigated the effect of freezing temperature (-70 and -196 degrees C) and of 5, 10 and 20% (w/v) cryoprotector (mannitol, sorbitol, glucose and threalose) on 100 nm particles. The addition of glucose and threalose at concentrations > 10% permitted adequate reconstitution of the freeze-dried product with conservation of the encapsulated CyA.
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European Journal of Pharmaceutical Sciences, 1999
The present paper describes the stability of poly (D, L-lactide-glycolide) nanoparticles (PLGA NP... more The present paper describes the stability of poly (D, L-lactide-glycolide) nanoparticles (PLGA NP) and microspheres (MS), either alone or loaded with cyclosporine (CyA), stored at 8 degrees C and room temperature (RT). Freeze-drying of these formulations was evaluated as an alternative method to achieve long term stability. A significant polymer rupture was detected during PLGA MS preparation by solvent evaporation, which correlated with the stirring rates used for the formation of the primary emulsion. On the other hand, the polymer remained unchanged during NP formation. After 6 months of storage, PLGA NP of a size below 80 nm aggregated when stored at RT whereas no changes of particle size were observed for the remaining formulations and experimental conditions. Drug entrapment significantly increased by about 9.5% only during PLGA NP storage at RT. The PLGA molecular weight of NP dropped at RT being these changes related to the initial particle size and amount of CyA incorporated. The same effect was observed at 8 degrees C but only the particle size showed a significant influence. The drop of PLGA molecular weight observed during storage of MS was not dependent on the storage temperature but it was directly related to the molecular weights obtained after MS preparation. Freeze-drying studies revealed that it was not feasible to maintain the initial PLGA NP characteristics after reconstitution. On the other hand, MS lyophilized in the absence of cryoprotectants retained the drug initially entrapped; however, the presence of at least 5% cryoprotectant was essential to keep the initial particle size. Therefore, PLGA NP and MS show a significant instability when stored as suspensions. Freeze-drying offers a good alternative to stabilize polymeric MS but the preservation of the PLGA NP characteristics by freeze-drying needs for further investigations.
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Drug Development and Industrial Pharmacy, 1989
ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° ... more ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° C is studied “in vitro”. It is noted that as plasma/liposomal suspension ratio is increased, the porcentage of drug retained in the liposomes decreases. Just so, independently from the dosage form, the efflux rate is maximum during the first hour and then falls gradually and in a non linear way. The physical state of the bilayer is a conditioning factor in the release of the encapsulated drug. The dosage forms of egg yolk phosphatidylcholine (EYPC) and of dimiristoylphosphatidylcholine (DMPC) quickly release digitoxin; while dipalmitoylphosphatidylcholine (DPPC) retains 54% of the entrapped drug after 24 hours incubation with 80% of plasma at 37°C. The inclusion of cholesterol (CHOL) and dicetylphosphate (DCP) in the liposomal matrix neither aids in the incorporation of digitoxin to the liposomes, nor augments the stability of the system in the human plasma.
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Journal of Microencapsulation, 1996
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Drug Development and Industrial Pharmacy, 1994
ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 g... more ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer. In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.
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International Journal of Pharmaceutics, 1992
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Journal of Pharmaceutical Sciences, 1993
The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with ... more The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with acute hemodynamic changes that result in high nephrotoxicity. Among colloidal vectors, nanoparticles (NPs) are receiving much attention as potential drug carriers that would avoid the therapeutic risks of conventional formulations. Two different mechanisms for obtaining polymeric NPs loaded with CyA were studied with regard to their preparation and physicochemical characterization. Isobutyl-2-cyanoacrylate monomer (IBCA) was polymerized, whereas poly-E-caprolactone (PCL, a preformed polymer) was precipitated; both reactions took place in an aqueous medium containing Pluronic F-68 (polyoxypropylene polyoxyethylene block copolymer) as a surface active agent. The encapsulation efficiencies were 78.49 ± 5.87 and 84.85 ± 5.02%, respectively, and they remained stable over a wide range of drug concentrations. The polymeric NP had average sizes of 81 ± 25 and 95 ± 25 nm for poly-IBCA and PCL, respectively, as confirmed by photon correlation spectroscopy. Poly-IBCA NPs were built from oligomers with molecular weights of 157 to 2644 that joined to form a polymeric nanomatrix. In vitro activity of the drug and the carrier was tested by inhibition of lymphocyte proliferation induced by Concanavalin A. Drug-loaded PCL NPs and free CyA inhibited lymphocyte proliferation by 91.40 and 86.19%, respectively. However, drug-free NPs also exhibited statistically significant (p < 0.05) immunosuppressive activity.
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Toxicology for the Health and Pharmaceutical Sciences
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Toxicology for the Health and Pharmaceutical Sciences
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Journal of Drug Targeting, 2013
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European Journal of Pharmaceutical Sciences, 2001
The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycapr... more The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycaprolactone nanoparticles (CyA-NP) was assessed in vitro and in vivo and compared to the effects caused by free drug (Sandimmun. The in vivo study included four groups (12 Wistar rats each) receiving oral CyA (10 mg/kg/day for 3 days) as an emulsion of Sandimmun in whole milk or CyA-NP and equivalent doses of empty NP or cremophor in milk as controls. CyA concentrations in blood, urine, liver, spleen and kidney at 24 h post-dosing were measured by fluorescence polarization immunoassay (FPIA). The nephrotoxicity induced by each drug treatment was determined by measuring creatinine plasma levels, malonyl dialdehyde production, and H(2)O(2) and reduced glutathione contents in glomeruli. On the other hand, the immunosuppressive effect was estimated in vivo by incubating lymphocyte suspensions obtained from CyA-, CyA-NP- and control-treated rats, as well as in vitro on lymphocyte suspensions from non-treated healthy animals. Significantly higher blood, urine and tissue levels were achieved with CyA-NP compared to free CyA. However, no changes in creatinine plasma levels were detected due to either CyA or CyA-NP treatment. Only the production of H(2)O(2) in the glomeruli exhibited a significant increase as compared to control groups, but no differences could be ascribed to the different drug treatments. In vivo, the immunosuppressive activity was also comparable for both drug treatments. In contrast, CyA-NP showed a better drug uptake in vitro at concentrations above 25 microM. No immunosuppression was detected in control groups. NP improve the oral bioavailability of CyA and its uptake by lymphocytes in vitro above 25 microM. On the contrary, specific immunosuppression and adverse effects were not simultaneously increased. Further studies are needed to clarify the results.
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Journal of Pharmaceutical Sciences, 1996
Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparti... more Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve bioavailability after oral administration. In this study a composite rotational experimental design was used to evaluate the joint influence of five formulation variables: temperature of the aqueous phase, needle gauge, volume of the organic phase, and the amounts of polymer and surfactant on the micromeritic characteristics of the CyA-loaded NP obtained by the method of Fessi et al. The percentage of drug encapsulated in the NP was also evaluated for each formulation, and the yield, which was expressed as the ratio between the experimentally measured quantity of drug in the formulation and the theoretical content, was determined because CyA undergoes surface adsorption. Potential variables such as stirring speed (500 rpm), final drug concentration (100 μg/mL), or injection rates (GRi = 0.379 mL/s) were maintained constant. The ANOVA corresponding to the experimental design showed that the amounts of polymer and surfactant, and the diameter of the needle used in the preparation of NP, significantly affected the percentage of entrapped drug (r2 = 0.8916). The mean particle size, was significantly affected by all the formulation variables tested except for the amount of surfactant dissolved in the external aqueous phase (r2 = 0.9518). Neither the yield (mean value of 99.61%) nor the size distribution parameters (polydispersity and coefficient of variation) presented good correlation coefficients for the equations obtained, although some variables showed statistical significance. A second study was carried out to investigate the effects on the drug-loaded NP characteristics of varying the global injection rates (GRi) for the organic phase into the aqueous medium. The results showed a dramatic decrease in both particle size and drug incorporation in the carrier as the rate of mixing increased. From the results of both the experimental design and the second study, a theoretical model for nanoparticle formation is proposed that considers the most significant variables, and an empirical relationship to predict mean particle size is presented. Thus, particle size can be controlled by the injection rates (GRi), the needle gauge, and the polymer concentration.
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Journal of Microencapsulation, 1997
ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle sus... more ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle suspensions, stored at 8 and 25 degrees C. The stability of freeze-dried samples was also investigated. Nanoparticles (NP) of poly-sigma-caprolactone (P sigma CL), a biodegradable polymer, were obtained by a modified nanoprecipitation method. A central composite experimental design was used to investigate the simultaneous effect of technological factors (temperature of the aqueous phase and needle gauge) and formulation variables (volume of acetone and the amount of polymer and surfactant). The effect of these variables on the stability of the 100-220 nm particles obtained was evaluated. The percentage of cyclosporin A (CyA) encapsulated in the NP suspensions stored at 8 and 25 degrees C for at least 3 months remained unaltered. Moreover, there was no change in the size of NP. After 4 months storage, the physical stability of the preparation was affected. NP aggregates could be observed by light microscopy. Reconstituted freeze-dried preparations showed a mean increase of 1% in the incorporated drug and also a considerable increase in mean size and size distribution. Additional experiments investigated the effect of freezing temperature (-70 and -196 degrees C) and of 5, 10 and 20% (w/v) cryoprotector (mannitol, sorbitol, glucose and threalose) on 100 nm particles. The addition of glucose and threalose at concentrations > 10% permitted adequate reconstitution of the freeze-dried product with conservation of the encapsulated CyA.
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Drug Development and Industrial Pharmacy, 1989
ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° ... more ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° C is studied “in vitro”. It is noted that as plasma/liposomal suspension ratio is increased, the porcentage of drug retained in the liposomes decreases. Just so, independently from the dosage form, the efflux rate is maximum during the first hour and then falls gradually and in a non linear way. The physical state of the bilayer is a conditioning factor in the release of the encapsulated drug. The dosage forms of egg yolk phosphatidylcholine (EYPC) and of dimiristoylphosphatidylcholine (DMPC) quickly release digitoxin; while dipalmitoylphosphatidylcholine (DPPC) retains 54% of the entrapped drug after 24 hours incubation with 80% of plasma at 37°C. The inclusion of cholesterol (CHOL) and dicetylphosphate (DCP) in the liposomal matrix neither aids in the incorporation of digitoxin to the liposomes, nor augments the stability of the system in the human plasma.
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Drug Development and Industrial Pharmacy, 1994
ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 g... more ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer. In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.
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International Journal of Pharmaceutics, 1992
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European Journal of Pharmaceutical Sciences, 2001
The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycapr... more The nephrotoxicity and immunosuppressive ability of cyclosporine (CyA) incorporated into polycaprolactone nanoparticles (CyA-NP) was assessed in vitro and in vivo and compared to the effects caused by free drug (Sandimmun. The in vivo study included four groups (12 Wistar rats each) receiving oral CyA (10 mg/kg/day for 3 days) as an emulsion of Sandimmun in whole milk or CyA-NP and equivalent doses of empty NP or cremophor in milk as controls. CyA concentrations in blood, urine, liver, spleen and kidney at 24 h post-dosing were measured by fluorescence polarization immunoassay (FPIA). The nephrotoxicity induced by each drug treatment was determined by measuring creatinine plasma levels, malonyl dialdehyde production, and H(2)O(2) and reduced glutathione contents in glomeruli. On the other hand, the immunosuppressive effect was estimated in vivo by incubating lymphocyte suspensions obtained from CyA-, CyA-NP- and control-treated rats, as well as in vitro on lymphocyte suspensions from non-treated healthy animals. Significantly higher blood, urine and tissue levels were achieved with CyA-NP compared to free CyA. However, no changes in creatinine plasma levels were detected due to either CyA or CyA-NP treatment. Only the production of H(2)O(2) in the glomeruli exhibited a significant increase as compared to control groups, but no differences could be ascribed to the different drug treatments. In vivo, the immunosuppressive activity was also comparable for both drug treatments. In contrast, CyA-NP showed a better drug uptake in vitro at concentrations above 25 microM. No immunosuppression was detected in control groups. NP improve the oral bioavailability of CyA and its uptake by lymphocytes in vitro above 25 microM. On the contrary, specific immunosuppression and adverse effects were not simultaneously increased. Further studies are needed to clarify the results.
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Journal of Microencapsulation, 2002
The present study describes the development of a new cyclosporine formulation based on polycaprol... more The present study describes the development of a new cyclosporine formulation based on polycaprolactone (PCL) microspheres (MS) prepared by the solvent evaporation method. Ternary phase diagrams were used to identify the domains where MS were formed. The application of central composite designs established the influence of several technological (stirring speed) and formulation factors (polymer and surfactant amounts, and organic solvent volume) on the size of PCL MS. Cyclosporine-loaded MS of a size around 2.5 microm were prepared and characterized. The stability of the systems, either alone or loaded with cyclosporine, stored at 8 degrees C and room temperature (RT) was assessed as well. Freeze-drying was evaluated as an alternative method to achieve long-term stability. The experimental design showed that the stirring speed and the organic phase volume were the only parameters significantly affecting the MS size. Experimental conditions selected to obtain CyA-loaded MS of 2.5 microm resulted in a high entrapment percentage (98.4 +/- 0.66%) with the drug dissolved or molecularly dispersed within the dense polymeric matrix of MS. After 12 months of storage at 8 degrees C and RT, PCL MS remained physically stable, although the crystallinity of the polymer increased by 35% upon storage at both temperatures. Freeze-drying studies revealed that MS could be successfully lyophilized in the absence of cryoprotectants without significant changes of the drug entrapment; however, the presence of at least 5% cryoprotectant was essential to keep the initial particle size. Therefore, a stable MS-based CyA formulation was easily prepared and characterized. This formulation offer the possibility of CyA administration through different routes.
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Journal of Pharmaceutical Sciences, 1996
Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparti... more Cyclosporin A (CyA) is a good candidate for incorporation in colloidal carriers such as nanoparticles (NP) that would diminish the adverse effects associated with its use under conventional pharmaceutical dosage forms and improve bioavailability after oral administration. In this study a composite rotational experimental design was used to evaluate the joint influence of five formulation variables: temperature of the aqueous phase, needle gauge, volume of the organic phase, and the amounts of polymer and surfactant on the micromeritic characteristics of the CyA-loaded NP obtained by the method of Fessi et al. The percentage of drug encapsulated in the NP was also evaluated for each formulation, and the yield, which was expressed as the ratio between the experimentally measured quantity of drug in the formulation and the theoretical content, was determined because CyA undergoes surface adsorption. Potential variables such as stirring speed (500 rpm), final drug concentration (100 μg/mL), or injection rates (GRi = 0.379 mL/s) were maintained constant. The ANOVA corresponding to the experimental design showed that the amounts of polymer and surfactant, and the diameter of the needle used in the preparation of NP, significantly affected the percentage of entrapped drug (r2 = 0.8916). The mean particle size, was significantly affected by all the formulation variables tested except for the amount of surfactant dissolved in the external aqueous phase (r2 = 0.9518). Neither the yield (mean value of 99.61%) nor the size distribution parameters (polydispersity and coefficient of variation) presented good correlation coefficients for the equations obtained, although some variables showed statistical significance. A second study was carried out to investigate the effects on the drug-loaded NP characteristics of varying the global injection rates (GRi) for the organic phase into the aqueous medium. The results showed a dramatic decrease in both particle size and drug incorporation in the carrier as the rate of mixing increased. From the results of both the experimental design and the second study, a theoretical model for nanoparticle formation is proposed that considers the most significant variables, and an empirical relationship to predict mean particle size is presented. Thus, particle size can be controlled by the injection rates (GRi), the needle gauge, and the polymer concentration.
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European Journal of Pharmaceutics and Biopharmaceutics, 2000
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Journal of Microencapsulation, 1997
ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle sus... more ABSTRACT The aim was to evaluate the long-term stability of cyclosporin A-loaded nanoparticle suspensions, stored at 8 and 25 degrees C. The stability of freeze-dried samples was also investigated. Nanoparticles (NP) of poly-sigma-caprolactone (P sigma CL), a biodegradable polymer, were obtained by a modified nanoprecipitation method. A central composite experimental design was used to investigate the simultaneous effect of technological factors (temperature of the aqueous phase and needle gauge) and formulation variables (volume of acetone and the amount of polymer and surfactant). The effect of these variables on the stability of the 100-220 nm particles obtained was evaluated. The percentage of cyclosporin A (CyA) encapsulated in the NP suspensions stored at 8 and 25 degrees C for at least 3 months remained unaltered. Moreover, there was no change in the size of NP. After 4 months storage, the physical stability of the preparation was affected. NP aggregates could be observed by light microscopy. Reconstituted freeze-dried preparations showed a mean increase of 1% in the incorporated drug and also a considerable increase in mean size and size distribution. Additional experiments investigated the effect of freezing temperature (-70 and -196 degrees C) and of 5, 10 and 20% (w/v) cryoprotector (mannitol, sorbitol, glucose and threalose) on 100 nm particles. The addition of glucose and threalose at concentrations > 10% permitted adequate reconstitution of the freeze-dried product with conservation of the encapsulated CyA.
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European Journal of Pharmaceutical Sciences, 1999
The present paper describes the stability of poly (D, L-lactide-glycolide) nanoparticles (PLGA NP... more The present paper describes the stability of poly (D, L-lactide-glycolide) nanoparticles (PLGA NP) and microspheres (MS), either alone or loaded with cyclosporine (CyA), stored at 8 degrees C and room temperature (RT). Freeze-drying of these formulations was evaluated as an alternative method to achieve long term stability. A significant polymer rupture was detected during PLGA MS preparation by solvent evaporation, which correlated with the stirring rates used for the formation of the primary emulsion. On the other hand, the polymer remained unchanged during NP formation. After 6 months of storage, PLGA NP of a size below 80 nm aggregated when stored at RT whereas no changes of particle size were observed for the remaining formulations and experimental conditions. Drug entrapment significantly increased by about 9.5% only during PLGA NP storage at RT. The PLGA molecular weight of NP dropped at RT being these changes related to the initial particle size and amount of CyA incorporated. The same effect was observed at 8 degrees C but only the particle size showed a significant influence. The drop of PLGA molecular weight observed during storage of MS was not dependent on the storage temperature but it was directly related to the molecular weights obtained after MS preparation. Freeze-drying studies revealed that it was not feasible to maintain the initial PLGA NP characteristics after reconstitution. On the other hand, MS lyophilized in the absence of cryoprotectants retained the drug initially entrapped; however, the presence of at least 5% cryoprotectant was essential to keep the initial particle size. Therefore, PLGA NP and MS show a significant instability when stored as suspensions. Freeze-drying offers a good alternative to stabilize polymeric MS but the preservation of the PLGA NP characteristics by freeze-drying needs for further investigations.
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Drug Development and Industrial Pharmacy, 1989
ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° ... more ABSTRACT Abstract The stability of multilamellar liposomes with digitoxin in human plasma at 37° C is studied “in vitro”. It is noted that as plasma/liposomal suspension ratio is increased, the porcentage of drug retained in the liposomes decreases. Just so, independently from the dosage form, the efflux rate is maximum during the first hour and then falls gradually and in a non linear way. The physical state of the bilayer is a conditioning factor in the release of the encapsulated drug. The dosage forms of egg yolk phosphatidylcholine (EYPC) and of dimiristoylphosphatidylcholine (DMPC) quickly release digitoxin; while dipalmitoylphosphatidylcholine (DPPC) retains 54% of the entrapped drug after 24 hours incubation with 80% of plasma at 37°C. The inclusion of cholesterol (CHOL) and dicetylphosphate (DCP) in the liposomal matrix neither aids in the incorporation of digitoxin to the liposomes, nor augments the stability of the system in the human plasma.
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Journal of Microencapsulation, 1996
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Drug Development and Industrial Pharmacy, 1994
ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 g... more ABSTRACT Abstract Gelatine gels and polyoxyethylene-polyoxypropylene (PluroniR) F-108 and F-127 gels were prepared at concentrations ranging between 5 and 25% (W/V), the former by dispersion at 37°C, the later by dispersion at 4°C. The viscosity, the gel-sol transition temperature and the “in vitro” release kinetics of these gels were compared as a first step for the elaboration of parented controlled release formulations. Phenolsulphonftaleine (PR) was used as a tracer. In all cases the viscosity increased with the rise in the concentration of gelatin (20 to 264 cps for 5 to 20%) or pluronic (260 and 1,520 cps for 20 and 25% F-108). The gel-sol transition temperature for gelatine gels was directly related to the concentration. On the contrary, for pluronic gels an inverse relation was observed, being the gel-sol transition temperature higher in copolymers with a large percentage of polyoxyethylene groups (30±0.2 °C for 25 % F-108). In both types of gels, a rise in pH and ionic strength decreased the gel-sol transition temperature, whereas PR increase this temperature. The release of the tracer, from the gels to the aqueous medium, showed a zero-order kinetics and the release rates were inversely proportional to the concentration of gelling agent.
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International Journal of Pharmaceutics, 1992
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Journal of Pharmaceutical Sciences, 1993
The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with ... more The commercially available formulations of cyclosporine (cyclosporin A, CyA) are associated with acute hemodynamic changes that result in high nephrotoxicity. Among colloidal vectors, nanoparticles (NPs) are receiving much attention as potential drug carriers that would avoid the therapeutic risks of conventional formulations. Two different mechanisms for obtaining polymeric NPs loaded with CyA were studied with regard to their preparation and physicochemical characterization. Isobutyl-2-cyanoacrylate monomer (IBCA) was polymerized, whereas poly-E-caprolactone (PCL, a preformed polymer) was precipitated; both reactions took place in an aqueous medium containing Pluronic F-68 (polyoxypropylene polyoxyethylene block copolymer) as a surface active agent. The encapsulation efficiencies were 78.49 ± 5.87 and 84.85 ± 5.02%, respectively, and they remained stable over a wide range of drug concentrations. The polymeric NP had average sizes of 81 ± 25 and 95 ± 25 nm for poly-IBCA and PCL, respectively, as confirmed by photon correlation spectroscopy. Poly-IBCA NPs were built from oligomers with molecular weights of 157 to 2644 that joined to form a polymeric nanomatrix. In vitro activity of the drug and the carrier was tested by inhibition of lymphocyte proliferation induced by Concanavalin A. Drug-loaded PCL NPs and free CyA inhibited lymphocyte proliferation by 91.40 and 86.19%, respectively. However, drug-free NPs also exhibited statistically significant (p < 0.05) immunosuppressive activity.
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