Showing papers in "Journal of Microencapsulation in 1992"
TL;DR: A method based on an emulsification process was developed for the production of calcium alginate microspheres and it was found that a suspension of the drug particles was required for effective microencapsulation.
Abstract: A method based on an emulsification process was developed for the production of calcium alginate microspheres. Isopropyl alcohol and acetone, which are strong dehydrating agents, were used to aid in the hardening and drying of the microspheres. However, the amount of drug encapsulated was very low. This was due to the drug being soluble in the dehydrating solvents. In the absence of the solvents a high percentage of drug was encapsulated, and this was further increased by forming the microspheres by phase inversion. It was also found that a suspension of the drug particles was required for effective microencapsulation. The efficiency of drug encapsulation generally increased with the ratio of drug to encapsulating material. The microspheres produced were free-flowing and most of them were smaller than 150 microns.
123 citations
TL;DR: Poloxamine 1508 was the most efficient coating material in reducing the liver uptake and increasing the blood levels of poly(methyl methacrylate) nanoparticles, and another parameter for preselection could be molecular weights of the poloxamines.
Abstract: The body distribution of surfactant-coated and non-coated poly(methyl methacrylate) nanoparticles with a size of 131 +/- 30 nm after intravenous injection into rats was investigated. The coating materials were poloxamine 904, poloxamine 908, poloxamine 1508, poloxamer 338, and Brij 35. These materials were preselected by the method of contact angle measurement. No overall valid relation between contact angles and the modification of body distribution could be found. However, the classification of surfactants by determination of the contact angles of the surfactant solution on the polymer material seems to be a very helpful method for preselection of poloxamers and poloxamines. Another parameter for preselection could be molecular weights of the poloxamines. Poloxamine 1508 was the most efficient coating material in reducing the liver uptake and increasing the blood levels of poly(methyl methacrylate) nanoparticles.
60 citations
TL;DR: Ibuprofen-wax (carnauba, paraffin, beeswax, and the semisynthetic glyceryl esters--Gelucire 64/02 and Precirol ATO5) microparticles were prepared without organic solvents as an alternative to polymeric microp articles to improve drug loading and morphological and release properties.
Abstract: Ibuprofen-wax (carnauba, paraffin, beeswax, and the semisynthetic glyceryl esters--Gelucire 64/02 and Precirol ATO5) microparticles were prepared without organic solvents as an alternative to polymeric microparticles. In the melt dispersion technique, the drug-wax melt was emulsified into a heated aqueous phase followed by cooling to form the microparticles. The microparticles were characterized with respect to their drug loading, and morphological and release properties. They were spherical and non-agglomerated and drug loading close to 60 per cent were achieved. The more hydrophilic waxes (Gelucire 64/02 or Precirol ATO5) could be prepared without the use of surfactants. With the other waxes, increasing amounts of sodium lauryl sulphate in the external aqueous phase decreased the drug loading because of drug solubilization when compared to the polymeric stabilizer, poly(vinyl alcohol). The type of wax, the rate of cooling, and the temperature of the aqueous phase had no significant effect on the drug loading because of the low solubility of the drug in the external aqueous phase. The drug release was controlled by the hydrophobicity of the wax. Besides ibuprofen, other water-soluble drugs (ketoprofen, indomethacin, hydrocortisone) were also encapsulated by this method. The wax microparticles could be formulated into an aqueous sustained-release oral suspension dosage form.
57 citations
TL;DR: Pseudoephedrine HCl-carnauba wax microparticles prepared by a multiple emulsion-melt dispersion technique were formed after cooling and congealing of the wax phase and the drug release was much faster when compared to the release from polymeric microspheres.
Abstract: Pseudoephedrine HCl-carnauba wax microparticles were prepared by a multiple emulsion-melt dispersion technique. A heated aqueous drug solution was emulsified into the wax melt (W/O emulsion), followed by emulsification of this primary emulsion into a heated external aqueous phase (W/O/W emulsion). The drug-containing microparticles were formed after cooling and congealing of the wax phase. The encapsulation efficiencies were above 80 per cent and actual drug loadings close to 50 per cent were achieved. The surface of the microparticles had submicron pores and drug crystals were visible on cross-sections. The drug loading depended on the rate of cooling and the volume of the internal aqueous phase but was insensitive to the volume of the continuous phase. The drug release was much faster when compared to the release from polymeric microspheres.
38 citations
TL;DR: The Eudragit E100-coated crosslinked gelatin microcapsule formulation was most effective in preventing release of the TE-031 under simulated conditions of storage in an aqueous solution.
Abstract: Various microencapsulated dosage forms were prepared to limit the release of an antibiotic in solution for up to 3 days and in the oral cavity following per oral administration. An experimental antibiotic, clarithromycin (TE-031), was used in these studies. The drug was first encapsulated in gelatin followed in some cases by crosslinking with glutaraldehyde. The gelatin microcapsules were then coated with acrylic resins (Eudragit®), whose solubility properties vary according to pH. A non-solvent coacervation technique was used to apply the Eudragit resins. It was found that crosslinking the gelatin retarded release of TE-031 somewhat relative to that from uncrosslinked gelatin microcapsules in a 72 h release experiment conducted at room temperature. Coating the gelatin microcapsules with Eudragit resins L100, S100, or E100 slowed the release of TE-031 further still; less TE-031 was released over 72 h from the Eudragit-coated formulations prepared with crosslinked gelatin compared with formulations...
36 citations
TL;DR: It is reasonable to hypothesize that drug loading level has a greater effect on drug diffusion than on polymer relaxation, which could explain the increase of the diffusion component of the drug release process as the payload increased.
Abstract: The effect of drug loading level both on dynamic swelling and drug release was evaluated using crosslinked gelatin microspheres. Owing to water penetration the microsphere diameter went first to a maximum value, which was not affected by the payload; the diameter gradually approached to an equilibrium swollen value, which was affected by drug loading level. Water absorption increases and drug diffusion decreases the microsphere diameter. Obviously, the diameter variation depends on the factor (water absorption or drug diffusion) predominating in the process. As the payload affected only the equilibrium swollen value it is reasonable to hypothesize that drug loading level has a greater effect on drug diffusion than on polymer relaxation. This rationale could explain the increase of the diffusion component of the drug release process as the payload increased.
35 citations
TL;DR: Flow property measurements indicated that the plasticizers also affect the cohesiveness of the spray-dried products, and propylene glycol, glycerin and citric acid appeared to be beneficial to the microcapsule wall formation, with microcapsules containingcitric acid having the slowest drug release.
Abstract: Microencapsulated theophylline particles were prepared by an aqueous spray-drying process using hydroxypropylmethylcellulose. The effect of different plasticizers, triethylcitrate, polyethylene glycol, propylene glycol, glycerin and citric acid, was investigated. Triethylcitrate, a water-insoluble plasticizer, produced a porous honeycomb-like microcapsule wall resulting in rapid drug release. The presence of the plasticizers also influenced crystallization of the drug. The formation of a solid drug dispersion was observed with the addition of citric acid or glycerin. Changes in the pH of liquid feed caused by the plasticizer had an effect on the product dissolution profile, but this was not a major factor. Formation of pores due to leaching of plasticizers during dissolution enhanced drug release. Flow property measurements indicated that the plasticizers also affect the cohesiveness of the spray-dried products. Compared to the microcapsules formed without any plasticizers, propylene glycol, glyce...
33 citations
TL;DR: The studies suggest the potentiality of primaquine-loaded, glutaraldehyde-treated erythrocytes as an intravenous drug delivery system for casual prophylaxis and radical cure of malaria.
Abstract: Primaquine phosphate, an antimalarial drug, was loaded in erythrocytes by the process of endocytosis. The encapsulation of 0.1-0.15 mg of drug ml−1 of packed erythrocytes was achieved. The loaded cells attained spherical shape and exhibited higher osmotic fragility and lower resistance to turbulence shock as compared with normal cells. Glutaraldehyde treatment stabilized the cells which were noted to be resistant to the osmotic and turbulence shocks. In vitro release of drug and haemoglobin was also retarded upon treatment of loaded erythrocytes with glutaraldehyde. The studies suggest the potentiality of primaquine-loaded, glutaral-dehyde-treated erythrocytes as an intravenous drug delivery system for casual prophylaxis and radical cure of malaria.
29 citations
TL;DR: Fluphenazine-loaded microspheres were prepared using biodegradable lactide and lactide-co-glycolide polymers and it was considered that polymer degradation occurred by a mechanism involving propagation of active sites, drug release reflecting the spread of this degradation throughout the polymer.
Abstract: Fluphenazine-loaded microspheres were prepared using biodegradable lactide and lactide-co-glycolide polymers. Sustained release of fluphenazine was achieved with fluphenazine loadings of up to 30 per cent in both the lactide and lactide-co-glycolide polymers. Fluphenazine release from microspheres was found to increase with increasing drug loading and was most rapid from the poly-L-lactide-co-glycolide microspheres. The release profiles showed a ‘lag' period followed by an accelerating release phase and in some cases a decay period, i.e. the release profiles were sigmoidal and fitted the Prout-Tomkins equation (Prout and Tompkins 1944). Consequently it was considered that polymer degradation, the primary rate-determining step controlling drug release, occurred by a mechanism involving propagation of active sites, drug release reflecting the spread of this degradation throughout the polymer.
28 citations
TL;DR: In vitro release of ketoprofen from microcapsules confirmed the efficiency of the encapsulation process for preparing prolonged release medication and a capsule formulation with optimum sustained-release profile was suggested.
Abstract: Ketoprofen powder was encapsulated with Eudragit RL/RS polymer solutions in isopropanol-acetone 1:1, using a simple and rapid method. Microcapsules were prepared using Eudragit solutions with different RL/RS ratios. The encapsulation process produces free-flowing microcapsules with good drug content and marked decrease in dissolution rate. The retardation in release profile of ketoprofen from microcapsules was a function of the polymer ratio employed in the encapsulation process. In vitro release of ketoprofen from microcapsules either filled in gelatin capsules or compressed into tablets, using calcium sulphate as diluent, confirmed the efficiency of the encapsulation process for preparing prolonged release medication. A capsule formulation with optimum sustained-release profile was suggested.
22 citations
TL;DR: It was observed that the pseudolatex-based ocular formulations of pilocarpine exhibited in vivo prolonged therapeutic efficacy and polymer based pseudolatices hold promise for controlled pilocARPine ocular delivery.
Abstract: The pseudolatex-based ocular formulations of pilocarpine were prepared using different combinations of Eudragit RS 100 and polyvinyl pyrrolidone for prolonged and controlled release of the drug. The designed system was essentially based on polymeric pseudolatex dispersion. The process variables that effect the latex particle size, drug loading and release profiles of drug were studied. Preparations were evaluated for their in vitro performance with regard to release profile and diffusion co-efficient. The designed system exhibited linear relationship between cumulative drug release (Q) and square root of time (t0,5). The products selected on the basis of in vitro characterization were studied for in vivo performance evaluation. It was observed that the preparations exhibited in vivo prolonged therapeutic efficacy. Thus polymer based pseudolatices hold promise for controlled pilocarpine ocular delivery.
TL;DR: Reservoir-type microcapsules were prepared using a double emulsion solvent evaporation technique from a series of nine different poly-beta-hydroxybutyrate (PHB)-based polymers in which both molecular weight and hydroxyvalerate content were varied, producing particles that were generally distorted in shape and had highly irregular, macroporous, surface morphologies.
Abstract: Reservoir-type microcapsules were prepared using a double emulsion solvent evaporation technique from a series of nine different poly-β-hydroxybutyrate (PHB)-based polymers in which both molecular weight and hydroxyvalerate content were varied. Particles prepared from a low molecular weight (MW 43 000) homopolymer had a shrivelled appearance, but were not porous. When the molecular weight of the fabricating homopolymer was increased to 540000, however, these features disappeared and non-wrinkled particles with microporous surfaces were observed. Microcapsules prepared from a high molecular weight copolymer of PHB with 10.8 per cent hydroxyvalerate (HV) had a similar appearance, but particles prepared from a high molecular weight 20.1 per cent HV copolymer had much smoother and less porous surfaces. Lowering the molecular weight of the copolymer had the effect of producing particles that were generally distorted in shape and had highly irregular, macroporous, surface morphologies. Increasing the do...
TL;DR: In-vivo studies in dogs confirmed that dried beads prepared by extruding a suspension of 10 per cent w/w sulphamethizole in 3 per cent aqueous Gelrite dispersion had effective sustained properties on oral dosing in comparison to a conventional capsule formulation but had a possible small loss in relative bioavailability.
Abstract: Deacetylated gellan gum (Gelrite) was used to produce a bead formulation containing sulphamethizole by a hot extrusion process into chilled ethylacetate. The spherical dried beads recovered had a porous surface which could be reduced in porosity by increasing the Gelrite concentration. Energy dispersive analysis showed the drug to be uniformly distributed throughout the beads. Dissolution studies confirmed that the drug was slowly released from the beads, the retardation of which could be extended by the use of increasing Gelrite concentration or by post-treatment of dried beads with either a waxy sealant or gamma irradiation. In-vivo studies in dogs confirmed that dried beads prepared by extruding a suspension of 10 per cent w/w sulphamethizole in 3 per cent aqueous Gelrite dispersion had effective sustained properties on oral dosing in comparison to a conventional capsule formulation but had a possible small loss in relative bioavailability.
TL;DR: It was observed that compression of grafted starch microspheres modified drug release and extended drug action via slow release following buccal application.
Abstract: A polymer-grafted mucoadhesive system bearing isosorbide dinitrate was prepared for buccal administration. Polymer grafting of starch microspheres modified drug release and surface characteristics of microspheres. Bioadhesion and factors affecting bioadhesion were studied. Process variables that could affect microsphere size, and as a result the release of the drug, were also studied. It was observed that compression of grafted starch microspheres modified drug release and extended drug action via slow release following buccal application. Prepared system(s) were characterized for drug release and in vivo performance and compared with conventional oral treatment. The systems were noted to be promising.
TL;DR: An emulsion-solvent evaporation method for preparation of microcapsules containing water-soluble 2-hydroxypropyl-beta-cyclodextrin complex of a lipophilic water-insoluble drug, hydrocortisone, is described.
Abstract: An emulsion-solvent evaporation method for preparation of microcapsules containing water-soluble 2-hydroxypropyl-β-cyclodextrin complex of a lipophilic water-insoluble drug, hydrocortisone, is described. The release of the drug from the microcapsules was determined in simulated gastric fluid. The drug release rate from the microcapsules could be controlled by addition of a plasticizer and it was sustained over extended time. Addition of solubilizing compounds to the dissolution medium did not affect the drug release rate.
TL;DR: In this paper, the authors studied the permeation of electrolyte ions through poly(L-lysine-alt-terephthalic acid) microcapsule membranes as a function of the pH of the medium at different ionic strengths.
Abstract: Permeation of electrolyte ions through poly(L-lysine-alt-terephthalic acid) microcapsule membranes was studied as a function of the pH of the medium at different ionic strengths. When the pH of the medium was varied, the permeation rate for 5-sulphosalicylate anions, as well as phenyltrimethylammonium cations, was slow at pH values lower than 4, showed a sudden and large increase in the pH range between 4 and 6, and thereafter remained unchanged. This remarkable change in the permeation rate was found to be produced by an abrupt increase in the microcapsule size observed in the same pH range. Increase in the ionic strength of the medium at pH values higher than 6 increased the rate of anion permeation but decreased the rate of cation permeation due to increase in the screening effect of salt ions on the negative charges in the microcapsule membranes.
TL;DR: Deliberate inclusion of toluene as a fragrance component in one of the prototype fragrances showed that some losses of highly volatile fragrance components can be expected during microencapsulation; but because most fragrance components do not approach the volatility of toLUene, such losses are expected to be minimal.
Abstract: Prototype fragrances, prepared from common fragrance components, were extracted with water, recovered, and characterized by gas chromatography before and after the water treatment, revealing a significant loss of the more water-soluble components. Unextracted prototype fragrances were also microencapsulated by a gelatin/gum arabic coacervation process. The microencapsulated fragrance oils were recovered from the microcapsules, using pepsin enzyme to open up the capsules. Comparison of GC results of microencapsulated fragrance oil versus unencapsulated oil showed many of the changes could be ascribed to solubility losses of the more water-soluble components to the process water. Deliberate inclusion of toluene as a fragrance component in one of the prototype fragrances showed that some losses of highly volatile fragrance components can be expected during microencapsulation; but because most fragrance components do not approach the volatility of toluene, such losses are expected to be minimal. Chrom...
TL;DR: In this article, the in vivo distribution and intrahepatic deacylation of liposomal FUdR-dipalmitate was found to be strongly dependent on liposome composition and on drug to lipid ratio.
Abstract: 3′,5′-O-dipalmitoyl-5-fluoro-2′-deoxyuridine (FUdR-dipalmitate), a lipophilic prodrug of 5-fluoro-2′-deoxyuridine (FUdR), was incorporated in different types of liposomes. The in vivo distribution and intrahepatic deacylation of liposomal FUdR-dipalmitate was found to be strongly dependent on liposome composition and on drug to lipid ratio. The use of fluid-type liposomes (egg PC/PS/CHOL) rendered FUdR-dipalmitate more susceptible to enzymatic breakdown than solid-type liposomes (DSPC/DPPG/CHOL). A decrease of the retention of the drug in the body was also obtained when FUdR-dipalmitate was incorporated in solid-type liposomes with high drug to lipid ratio (1:10) than with low ratio (1:50). In spite of these substantial differences in the rates at which FUdR was liberated from liposomes with different fluidity, size, or drug to lipid ratio, only minor differences in therapeutic effect were observed in a number of murine tumour models (P388 leukaemia, Lewis Lung carcinoma, B16 melanoma and a C26 ad...
TL;DR: In vitro release kinetics of salbutamol sulphate was studied following the zero order, first order and Higuchi equations and release from tableted microcapsules was significantly more prolonged than the respective batches.
Abstract: Microcapsules of salbutamol sulphate were prepared using beeswax and car-nauba wax as coating materials. In vitro release kinetics were studied following the zero order, first order and Higuchi equations. Beeswax alone was not effective but beeswax and carnauba wax combinations were suitable in controlling the in vitro release of the drug. Microcapsules were compressed into tablets to get a controlled release oral dosage form. Release from tableted microcapsules was significantly more prolonged than the respective batches of the microcapsules. Best data fit with the highest correlation coefficient for the tableted microcapsules was obtained for first order.
TL;DR: The prepared microcapsules were evaluated for their drug content, particle size distribution (microscopic method), flow properties, bulk density, in vitro dissolution and drug release kinetics.
Abstract: Propranolol hydrochloride microcapsules were prepared by the coacervationphase separation induced by solvent evaporation technique. The cellulose acetate phthalate was employed as coating material alone and in combination with ethyl cellulose. The prepared microcapsules were evaluated for their drug content, particle size distribution (microscopic method), flow properties, bulk density, in vitro dissolution and drug release kinetics.
TL;DR: It was found from regression analysis that there is relatively simple correlation between unknown parameters of the equation and the preparation conditions, and at least as far as the authors examined here, the release rate constant of the microsphere can be estimated from the preparation Conditions.
Abstract: Release rates from BSA microspheres prepared from various conditions are analysed using a previously reported equation expressing the first-order release rate constant. The permeability constants calculated applying the equation on experimental release rates are in good agreement with the constants measured from permeation studies using planar membrane, for various preparation conditions. It is shown that the equation expressing the first-order release rate constant is valid more extensively. The permeability constant varies depending on the preparation conditions, and the reason for variation is shown clearly to be the difference in degree of swelling of the polymer. It was found from regression analysis that there is relatively simple correlation between unknown parameters of the equation and the preparation conditions. Release rate constants can be calculated applying the equation on the known parameters and the estimated values of the unknown parameters from the correlation. Good agreement was found between the calculated values and experimental ones; therefore, at least as far as we examined here, the release rate constant of the microsphere can be estimated from the preparation conditions.
TL;DR: It was found that the membrane permeability can be adjusted by changing experimental conditions to obtain high adsorption capacity along with a low level of released particles.
Abstract: A potential haemoperfusion system has been developed using activated charcoal encapsulated with a polyacrylate-polymethacrylate copolymer. The film forms a coating of great mechanical strength around the charcoal particles, which is readily permeable to water and certain dissolved substances. The charcoal granules were coated with various membrane thicknesses consisting of a 2-10 per cent (by weight) film coat, using the modified method of non-solvent addition of Benita et al. (1985). The effect of various encapsulation variables such as stirring rate, rate of addition of non-solvent, percentage of coating polymer and concentration of a non-wall-forming polymer (PIB) in the non-solvent phase on adsorptivity, as well as the release of fine particles, were determined. The effect of coating thickness on the adsorption rate of the coated charcoal was investigated by constructing Higuchi diffusion model plots using methylene blue as a model adsorbate. It was found that the membrane permeability can be adjusted by changing experimental conditions to obtain high adsorption capacity along with a low level of released particles. Further, the effect of presoaking of the coated charcoal in purified water, normal saline, and 0.067 M phosphate buffer pH 7.4 (for 24 h at 37 degrees C) on the rate of adsorption of methylene blue was also evaluated.
TL;DR: Terbutaline sulphate microcapsules were prepared by coacervation-phase separation (solvent evaporation) technique using ethyl cellulose as a coating material and evaluated for their drug content, particle size distribution, flow properties, bulk density, in vitro dissolution, drug release kinetics and surface characteristics.
Abstract: Terbutaline sulphate microcapsules were prepared by coacervation-phase separation (solvent evaporation) technique using ethyl cellulose as a coating material. Acetone, ethyl alcohol and isopropyl alcohol were employed as solvents for coating material. Microcapsules were evaluated for their drug content, particle size distribution (microscopic method), flow properties, bulk density, in vitro dissolution, drug release kinetics and surface characteristics (scanning electron microscopy).
TL;DR: Thermodynamics of small systems was found applicable to analyse the experimental findings, even though the process of water freezing in the microcapsules was not of an equilibrium nature.
Abstract: The freezing behaviour of water in polyurea microcapsules was studied through DSC (differential scanning calorimetry) and ESR (electron spin resonance) measurements under a non-equilibrium condition to show that supercooling of water becomes more noticeable with decreasing droplet size of the liquid. Thermodynamics of small systems was found applicable to analyse the experimental findings, even though the process of water freezing in the microcapsules was not of an equilibrium nature.
TL;DR: The influence of synthetic polymers, trehalose and sodium taurocholate on the stability of both MLVs* and SPLVs prepared from a range of lipids including synthetic polyhydroxyl lipids is reported.
Abstract: We report the influence of synthetic polymers, trehalose and sodium taurocholate on the stability of both MLVs* and SPLVs prepared from a range of lipids including synthetic polyhydroxyl lipids. In the absence of cryoprotective agents liposomes were found to release > 90 per cent of encapsulated marker when exposed to freeze-thawing or freeze-drying procedures. In the presence of polyvinylpalmitate a marginal enhancement of stability towards freeze-drying was observed, the effect being most marked with cholesterol-containing liposomes. Trehalose was also found to stabilize all preparations investigated towards freeze-drying. In particular SPLVS prepared from (C18:0, C14:0-GMG): EPC:C retained in > 90 per cent of the entrapped marker. Addition of polymers to trehalose-containing SPLVS did not further increase the stability. SPLVS prepared from lipids possessing a high transition temperature demonstrated enhanced stability in the presence of bile salts. This effect was most marked with SPLVs prepared from (C18:0, C22:0-GMG): C.
TL;DR: In this paper, the effects of polymer coating on liposome stability, encapsulation of ASA and its release kinetics have been measured; also, the conditions for optimization of poly(4-vinylpyridine)-coated liposomes have been determined.
Abstract: Liposomes of dimyristoylphosphatidylcholine (DMPC) and dicetylphosphate (DCP) reacted with 4-vinylpyridine (4-VP) to form a salt and, subsequently, autopolymerized for form poly(4-vinylpyridine) (poly(4-VP))-coated liposomes. The conditions for optimization of polymer coating have been determined; also, the effects of polymer coating on liposome stability, the encapsulation of ASA and its release kinetics have been measured. The coating efficiency was maximum at a DMPC: DCP 1: 1 mole ratio, at pH 4.0 in acetate buffer, and a polymerization time of 40min. The polymer-coated liposomes were stable in 2mM sodium cholate and 4 per cent isopropanol solutions, as determined from turbidity measurements, versus a 20–25% decrease in stability of uncoated liposomes. The encapsulation efficiency of ASA reached a maximum of 9 per cent at DMPC : DCP 1: 1 mole ratio. The release of ASA at 37°C., pH 70 was characterized by an initial fast release (85 and 63 per cent in 20min from uncoated and polymer-coated lipos...
TL;DR: Abietic acid was isolated from rosin N Grade by a simple process and the product was further standardized and the effect of various process variables such as agitation speed, coat-core ratio, etc., on the micromeritic and release characteristics has been described.
Abstract: Abietic acid was isolated from rosin N Grade (ISI) by a simple process and the product was further standardized. Sulphadiazine microcapsules were prepared by the solvent evaporation technique, using abietic acid as a wall-forming material. Discrete, spherical and free-flowing microcapsules were obtained by phase separation induced by solvent evaporation using bentonite as a solid emulsifier. The prepared microcapsules were evaluated for drug content, wall thickness, flow properties, size distribution, density and in vitro dissolution studies in gastric fluid. The effect of various process variables such as agitation speed, coat-core ratio, etc., on the micromeritic and release characteristics has been described.
TL;DR: By increasing the ratio of amines to acid chlorides and with a low concentration of total polymer, this work obtained more stable capsules and had a negative effect on the hardness of the polymer.
Abstract: Preparation of microcapsules with aqueous core and polyamide walls is influenced by several factors. We improved the stability of walls and size of capsules by simultaneous variation of four factors: total ratio of polymer, ratio of amines to acid chlorides, concentration of surfactant and speed of stirring. Use of factorial design minimizes the number of experiments and permits us to know the influence of these factors and of their interactions. By increasing the ratio of amines to acid chlorides and with a low concentration of total polymer, we obtained more stable capsules. Surfactant had a negative effect on the hardness of the polymer.
TL;DR: Azapropazone was encapsulated with pectin-rutin mixture using the fluidized bed technique and showed higher dissolution rate and bioavailability but lower ulcerogenic activity as compared with the drug alone.
Abstract: Azapropazone was encapsulated with pectin-rutin mixture using the fluidized bed technique The encapsulated particles showed higher dissolution rate and bioavailability but lower ulcerogenic activity as compared with the drug alone
TL;DR: Flow cytometry was used to analyse cell populations of empty or islet-loaded microcapsules grafted in the peritoneal cavity of mice, and cytotoxic assays with proteases secreted by inflammatory cells found an immune rejection did not seem to occur, but the degree of inflammation could explain the short life of the grafts.
Abstract: Grafted polyacrylamide microencapsulated islets of Langerhans in the peritoneal cavity of mice did not survive more than a few days, perhaps owing to a nonspecific inflammatory reaction or an immune rejection. To assess the two hypotheses, we used flow cytometry (FACS) to analyse cell populations of empty or islet-loaded microcapsules grafted in the peritoneal cavity of mice, and performed cytotoxic assays with proteases secreted by inflammatory cells. An immune rejection did not seem to occur, but the degree of inflammation could explain the short life of the grafts.