Preparation and In Vitro Evaluation of Chitosan Microspheres Containing Prednisolone: Comparison of Simple and Conjugate Microspheres

The purpose of the present study was to obtain a novel microparticulate formulation of prednisolone, which was adequate for the treatment of inflammatory bowel disease (IBD). The formulations prepared were evaluated in vitro. Two types of chitosan microspheres containing prednisolone, named Ch-Pred and Ch-SP-MS, were prepared by an emulsification-solvent evaporation method using a chitosan-prednisolone mixture and a chitosan-succinyl-prednisolone conjugate (Ch-SP), respectively. Ch-Pred and Ch-SP-MS were obtained in almost spherical shape. Ch-Pred showed a relatively high drug content of 13.2% (w/w), but the particle size was distributed from 10 to 45 µm, and a large initial burst release of approximately 60% was observed. On the other hand, although Ch-SP-MS exhibited a fairly low drug content of 3.5% (w/w), their particle size ranged from several hundred nanometers to 20 µm, with the mean diameter of 5 µm, and a gradual drug release profile was achieved. These characteristics on particle size and in vitro release suggested that Ch-SP-MS should have good potential as a microparticulate system for the treatment of IBD.     

Eudragit coating of chitosan-prednisolone conjugate microspheres and in vitro evaluation of coated microspheres

Chitosan-prednisolone conjugate microspheres (Ch-SP-MS) were prepared, and Eudragit coating was applied in order to efficiently deliver the microspheres and drug to the intestinal disease sites. The Eudragit L100-coated microspheres (Ch-SP-MS/EuL100) were examined for particle characteristics and the release of drug and Ch-SP-MS in different pH media at 37°C. Ch-SP-MS were spherical, with a mean size of 4.5 μm and prednisolone content of 3.3% (w/w). Ch-SP-MS/EuL100 were fairly spherical, with a mean size of 22. 5 μm and drug content of 0.32% (w/w). At pH 1.2, the release extent was less than 5% even at 48 h, and Eudragit coating tended to suppress the release. In contrast, at pH 6.8 and 7.4, Ch-SP-MS/EuL100 tended to show somewhat faster drug release than Ch-SP-MS. Ch-SP-MS/EuL100 displayed a release extent of 23 and 27% at pH 6.8 and 7.4, respectively. Ch-SP-MS aggregated at pH 1.2, but almost kept their initial size and shape at pH 6.8 and 7.4. Ch-SP-MS/EuL100 almost maintained their original shape and size at pH 1.2, and gradually released Ch-SP-MS at pH 6.8 and 7.4 due to dissolution of the Eudragit layer. Eudragit coating is suggested to be useful to efficiently deliver Ch-SP-MS to the intestinal disease sites.     

Eudragit Coating of Chitosan-Prednisolone Conjugate Microspheres and In Vitro Evaluation of Coated Microspheres

Chitosan-prednisolone conjugate microspheres (Ch-SP-MS) were prepared, and Eudragit coating was applied in order to efficiently deliver the microspheres and drug to the intestinal disease sites. The Eudragit L100-coated microspheres (Ch-SP-MS/EuL100) were examined for particle characteristics and the release of drug and Ch-SP-MS in different pH media at 37°C. Ch‐SP-MS were spherical, with a mean size of 4.5 μm and prednisolone content of 3.3% (w/w). Ch-SP-MS/EuL100 were fairly spherical, with a mean size of 22. 5 μm and drug content of 0.32% (w/w). At pH 1.2, the release extent was less than 5% even at 48 h, and Eudragit coating tended to suppress the release. In contrast, at pH 6.8 and 7.4, Ch-SP-MS/EuL100 tended to show somewhat faster drug release than Ch-SP-MS. Ch-SP-MS/EuL100 displayed a release extent of 23 and 27% at pH 6.8 and 7.4, respectively. Ch-SP-MS aggregated at pH 1.2, but almost kept their initial size and shape at pH 6.8 and 7.4. Ch-SP-MS/EuL100 almost maintained their original shape and size at pH 1.2, and gradually released Ch-SP-MS at pH 6.8 and 7.4 due to dissolution of the Eudragit layer. Eudragit coating is suggested to be useful to efficiently deliver Ch-SP-MS to the intestinal disease sites.     

Preparation and characterization of chitosan microspheres containing doxifluridine

Chitosan microspheres containing 5-fluorouracil (5-FU), tegafur (FT), and doxifluridine (DFUR) were prepared by the dry-in-oil method using silicone oil with no surfactant as a dispersion medium. For DFUR-containing chitosan microspheres (DFUR-M), reacetylation with acetic anhydride or coating using chitosan and glutaraldehyde was performed. DFUR-M, reacetylated DFUR-M, and chitosan-coated DFUR-M were investigated on in vitro drug release, and the former two microspheres were examined for in vivo degradation after subcutaneous (s.c.) implantation in mice, and in vivo plasma concentration-time profiles after s.c. implantation in rats. The present method gave fairly large microspheres purely composed of chitosan and drug because of no use of surfactant, which showed the mean particle diameters of 300-900 µm and the drug contents of 4-22% (w/w). Encapsulation efficiency of DFUR was higher than that of 5-FU and FT. DFUR-M and reacetylated DFUR-M exhibited spherical shape except chitosan-coated DFUR-M. DFUR-M showed high initial rapid release, which was suppressed to some extent by reacetylation or chitosan coating. DFUR-M and reacetylated DFUR-M subcutaneously implanted were gradually degraded, and approximately half or a little more of the microspheres disappeared from the implanted site at 3 weeks postimplantation. DFUR-M and reacetylated DFUR-M implanted subcutaneously gave similar plasma concentration-time profiles of DFUR, which did not indicate prolonged release in vivo. DFUR-containing chitosan microspheres with fairly large size and good drug content could be obtained by the present preparation but remained to be improved for drug release properties.     

Controlled drug delivery systems based on thiolated chitosan microspheres

The aim of the present study was to verify the potential of chitosan-thio-butyl-amidine (TBA) microspheres as carrier systems for controlled drug delivery. In this study microspheres were prepared utilizing water in oil (w/o) emulsification solvent evaporation technique. A concentration of 0.5% of chitosan-TBA conjugate displaying 100 µM thiol groups per gram polymer was used in the aqueous phase of the emulsion in order to prepare microspheres. The obtained non-aggregated free-flowing microspheres were examined with conventional light microscope as well as scanning electron microscopy (SEM). The microscopic images indicated that the prepared chitosan-TBA microspheres were of spherical shape and smooth surface while microparticles obtained from the unmodified chitosan were of porous structure and non-spherical shape. Particle size distribution was determined to be in the range from 1 to 59 µm. The free thiol group content of chitosan-TBA microspheres prepared with an aqueous phase of pH 2, 5, and 6.5 were determined to be 71.4, 49.4, and 8.2 µM/g polymer, respectively. Furthermore, results attained from in vitro release studies with fluorescein isothiocyanate labelled dextran (FITC-dextran) loaded chitosan-TBA microspheres showed a controlled release rate for more than three hours while the control reached the maximum peak level of release already within an hour. According to these results, chitosan-TBA microspheres seem to be a promising tool in transmucosal drug delivery for poorly absorbed therapeutic agents.     

Entrapment of Phenytoin into Microspheres of Oleaginous Materials: Process Development and in Vitro Evaluation of Drug Release

A novel multiparticulate preparation of the antiepileptic agent phenytoin (1) was developed and evaluated in vitro. The preparation consists of gastroresistant microparticulate drug delivery system formulated with oleaginous material (lipospheres) to minimize unwanted effects of l on gastric apparatus. The drug was dispersed in a spherical micromatrix consisting of a mixture of stearyl alcohol and glycerol esters of various fatty acids. The best mixture to obtain discrete, reproducible, free-flowing lipospheres consisted of glyceryl monostearate dilaurate and stearyl alcohol (ratio 3: 17). The lipospheres were obtained by a technique involving melting and dispersion of drug-containing oleaginous material in aqueous medium. The oily droplets of the resulting emulsion after cooling under rapid stirring were transformed into solid. About 99% of the lipospheres were of particle size range 100-800 pm. The lipospheres were analyzed to determine the drug content in various particle sizes and to characterize the in vitro release profile. The average drug content was 23.8% w/w. Drug encapsulation efficiency was about 93.6% and the yield of production ranged from 94 to 98%. The drug discharge pattern from the microparticulate system in the intestinal environment was evaluated. Kinetic results were analyzed to distinguish between various release models. The matrix diffusion-controlled equation was the most appropriate one in describing drug release.     

Aqueous preparation and evaluation of albumin-chitosan microspheres containing indomethacin

Controlled-release egg albumin-chitosan microspheres containing indomethacin as a model drug were successfully prepared by coacervation method. The proposed method can offer a simple method for microsphere preparation in an aqueous system with the elimination of the use of organic solvents that are usually needed in conventional techniques of microencapsulation. The interaction between negatively charged egg albumin molecules in phosphate buffer, pH 7.2, or sodium hydroxide solution and positively charged chitosan molecules dissolved in diluted acetic acid to form an insoluble precipitate was the principle for the formation of the microspheres. The effects of many process variables, such as amount of formaldehyde as a cross-linking agent, stirring time, final pH of encapsulation medium, initial drug loading, and albumin concentration or albumin-to-chitosan weight ratio, on the properties of the prepared microspheres were investigated. Incorporation efficiencies of the microspheres to the drug were high in most cases and ranged between 63.3 ± 3.6% and 92.39 ± 3.2%, while particle sizes were 435.2 ± 12.6 up to 693.9 ± 34.6 µm for the different tested batches. On the other hand, the values of angles of repose and compressibility indices were in the range of 23.5 ± 0.4 to 32.0 ± 0.7 degrees and 11.1 ± 0.7% to 23.6 ± 0.7% respectively, which indicate overall good free flowing nature of the microspheres of all batches. The maximum required amount of the cross-linking agent was determined to avoid excessive unnecessary chemicals. It was also noticed that excessive time of stirring and excessive initial drug loading are not recommended as it may lead to microspheres of low properties. The pH of the encapsulation media (pH 3.77 up to pH 4.91) significantly affected the properties of the microspheres. As the pH of the encapsulation media was increased, the incorporation efficiency, particle size, and flowability decreased, along with increase of drug release rate, which could be related to incomplete cross linking of the microspheres matrix. It was also observed that high concentration of albumin solution and accordingly the increase of albumin-to-chitosan weight ratio were accompanied with increases in incorporation efficiency and particle size with improved microsphere flowability and slow indomethacin release. Thus, the proposed microspheres showed the ability to control the release of indomethacin, and their properties were highly affected by many process variables that could be controlled to obtain an optimized system.     

Entrapment of Phenytoin into Microspheres of Oleaginous Materials: Process Development and in Vitro Evaluation of Drug Release

Abstract

A novel multiparticulate preparation of the antiepileptic agent phenytoin (1) was developed and evaluated in vitro. The preparation consists of gastroresistant microparticulate drug delivery system formulated with oleaginous material (lipospheres) to minimize unwanted effects of l on gastric apparatus. The drug was dispersed in a spherical micromatrix consisting of a mixture of stearyl alcohol and glycerol esters of various fatty acids. The best mixture to obtain discrete, reproducible, free-flowing lipospheres consisted of glyceryl monostearate dilaurate and stearyl alcohol (ratio 3: 17). The lipospheres were obtained by a technique involving melting and dispersion of drug-containing oleaginous material in aqueous medium. The oily droplets of the resulting emulsion after cooling under rapid stirring were transformed into solid. About 99% of the lipospheres were of particle size range 100–800 pm. The lipospheres were analyzed to determine the drug content in various particle sizes and to characterize the in vitro release profile. The average drug content was 23.8% w/w. Drug encapsulation efficiency was about 93.6% and the yield of production ranged from 94 to 98%. The drug discharge pattern from the microparticulate system in the intestinal environment was evaluated. Kinetic results were analyzed to distinguish between various release models. The matrix diffusion-controlled equation was the most appropriate one in describing drug release.     

Development of novel interpenetrating network gellan gum-poly(vinyl alcohol) hydrogel microspheres for the controlled release of carvedilol

Novel interpenetrating polymeric network microspheres of gellan gum and poly(vinyl alcohol) were prepared by the emulsion cross-linking method. Carvedilol, an antihypertensive drug, was successfully loaded into these microspheres prepared by changing the experimental variables such as ratio of gellan gum:poly(vinyl alcohol) and extent of cross-linking in order to optimize the process variables on drug encapsulation efficiency, release rates, size, and morphology of the microspheres. Formation of interpenetrating network and the chemical stability of carvedilol after preparing the microspheres was confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and x-ray diffraction studies were made on the drug-loaded microspheres to investigate the crystalline nature of the drug after encapsulation. Results indicated a crystalline dispersion of carvedilol in the polymer matrix. Scanning electron microscopy confirmed the spherical nature and smooth surface morphology of the microspheres produced. Mean particle size of the microspheres as measured by laser light scattering technique ranged between 230 and 346 µm. Carvedilol was successfully encapsulated up to 87% in the polymeric matrices. In vitro release studies were performed in the simulated gastric fluid or simulated intestinal fluid. The release of carvedilol was continued up to 12 h. Dynamic swelling studies were performed in the simulated gastric fluid or simulated intestinal fluid, and diffusion coefficients were calculated by considering the spherical geometry of the matrices. The release data were fitted to an empirical relation to estimate the transport parameters. The mechanical properties of interpenetrating polymeric networks prepared were investigated. Network parameters such as molar mass between cross-links and cross-linking density for interpenetrating polymeric networks were calculated.     

Preparation, Characterization and In-Vitro Release Kinetics of Salbutamol Sulphate Loaded Albumin Microspheres

Salbutamol sulphate loaded Bovine serum albumin microspheres were prepared by heat denaturation method. The effects of such preparation conditions as denaturation temperature, denaturation time, protein concentration and phase volume ratio on the extent of drug loading, size and size distribution and drug release were studied. An increase in protein concentration from 5% w/v to 15% w/v increased the mean particle size from 8.5 μm to 16.6 μm and decreased the drug loading from 46% w/w to 18% w/w. A decrease in the phase volume ratio substantially lowered mean particle size and size distribution. An increase in the severity of denaturaion conditions lowered both the drug incorporated and drug released. The kinetics of drug release from microspheres were compared to the theoretical models of Higuchi diffusional release and first order release. Both the models gave an adequate fit to the data. Scanning electron microscopy revealed that the dummy microspheres are spherical with smooth surfaces. As the drug-protein ratio increased, the microspheres exhibited rough surfaces showing the presence of drug crystals.     

Comparison of simple Eudragit microparticles loaded with prednisolone and Eudragit-coated chitosan-succinyl-prednisolone conjugate microparticles: Part I. Particle characteristics and in vitro evaluation as a colonic delivery system

Objective: Simple Eudragit microparticles loaded with prednisolone and chitosan-succinyl-prednisolone conjugate microparticles coated with Eudragit were prepared and characterized in vitro in order to obtain their basic features as a colonic delivery system.

Materials and methods: Both types of microparticles were prepared by the emulsification-solvent evaporation modified somewhat from the previous one. Their particle size, shape and their drug content were investigated, and in vitro release profiles were examined using JP-15 1st fluid (pH 1.2), JP-15 2nd fluid (pH 6.8) and PBS (pH 7.4) as release media. Furthermore, the regeneration of conjugate microparticles from Eudragit-coated microparticles was investigated under the same incubation conditions.

Results: Simple Eudragit S100 (EuS) microparticles (ES-M) were almost spherical, ca. 1.2 μm diameter, and PD content ca. 3.7% (w/w). Conjugate microparticles (CS-M1) and EuS-coated conjugate microparticles (CS-M1/S) had particle sizes of ca. 2.8 and 15.3 μm, respectively, and PD contents of 5.4 and 2.1% (w/w), respectively. ES-M exhibited suppressed release at pH 1.2, gradual release at pH 6.8 and rapid release at pH 7.4. CS-M1 showed no release at pH 1.2, and very slow release at pH 6.8 and 7.4. CS-M1 regenerated poorly from CS-M1/S at pH 6.8.

Conclusions: Simple Eudragit micrparticles and Eudragit-caoted conjugate microparticles, prepared by the present methods, were found in vitro to be possibly useful as the delivery systems of PD to the lower intestine, although there were differences in their release rate and morphological features.     

Development of biodegradable microcapsules as carrier for oral controlled delivery of amifostine

The primary objective of this project was to develop a biodegradable, orally active controlled-release formulation of amifostine. Development of such a formulation will mark an important advancement in the areas of chemoprotection and radioprotection. Biodegradable microcapsules of amifostine were prepared using poly(lactide/glycolide) (PLGA 50:50). The microcapsules were prepared by solvent evaporation technique. Amifostine-loaded microcapsules were evaluated for particle size, surface morphology, thermal characteristics, and drug release. Particle size and surface morphology were determined using scanning electron microscopy (SEM). Thermal characterization was conducted using differential scanning calorimetry (DSC). In vitro release study was performed at 37°C using phosphate buffer (pH 7.4). Amifostine release was calculated by measuring the amount of drug remaining within the microcapsules at a specific sampling time. The amount of amifostine in the samples was determined by high-performance liquid chromatography (HPLC) using an electrochemical detector. The yield of microcapsules was 75%. Scanning electron microscopy pictures revealed that the particles were nearly spherical and smooth with an average size of 54 µm. Differential scanning calorimetry thermograms showed that microcapsules loaded with amifostine have a glass transition at 39.4°C, and the melting endotherm of amifostine was absent. The absence of a melting endotherm for amifostine was an indication that amifostine was not in the crystalline state in the microcapsules, but rather in the form of a solid solution in PLGA. Approximately 50% amifostine was released during the first 6 hr of the in vitro release study. The drug, however, continued to release over the observed period of 12 hr during which 92% amifostine was released.     

Formulation and in vitro evaluation of prolonged release floating microspheres of atenolol using multicompartment dissolution apparatus

The aim of the present work was to prepare floating microspheres of atenolol as prolonged release multiparticulate system and evaluate it using novel multi-compartment dissolution apparatus. Atenolol loaded floating microspheres were prepared by emulsion solvent evaporation method using 3² full factorial design. Formulations F1 to F9 were prepared using two independent variables (polymer ratio and % polyvinyl alcohol) and evaluated for dependent variables (particle size, percentage drug entrapment efficiency and percentage buoyancy). The formulation(F8) with particle size of 329?±?2.69 µm, percentage entrapment efficiency of 61.33% and percentage buoyancy of 96.33% for 12?h was the of optimized formulation (F8). The results of factorial design revealed that the independent variables significantly affected the particle size, percentage drug entrapment efficiency and percentage buoyancy of the microspheres. In vitro drug release study revealed zero order release from F8 (98.33% in 12?h). SEM revealed the hollow cavity and smooth surface of the hollow microspheres.     

Preparation,Characterization and In-Vitro Release Kinetics of Salbutamol Sulphate Loaded Albumin Microspheres

Abstract

Salbutamol sulphate loaded Bovine serum albumin microspheres were prepared by heat denaturation method. The effects of such preparation conditions as denaturation temperature, denaturation time, protein concentration and phase volume ratio on the extent of drug loading, size and size distribution and drug release were studied. An increase in protein concentration from 5% w/v to 15% w/v increased the mean particle size from 8.5 μm to 16.6 μm and decreased the drug loading from 46% w/w to 18% w/w. A decrease in the phase volume ratio substantially lowered mean particle size and size distribution. An increase in the severity of denaturaion conditions lowered both the drug incorporated and drug released. The kinetics of drug release from microspheres were compared to the theoretical models of Higuchi diffusional release and first order release. Both the models gave an adequate fit to the data. Scanning electron microscopy revealed that the dummy microspheres are spherical with smooth surfaces. As the drug-protein ratio increased, the microspheres exhibited rough surfaces showing the presence of drug crystals.     

Carnauba Wax Microspheres Loaded with Valproic Acid: Preparation and Evaluation of Drug Release

To minimize unwanted toxic effects of valproic acid (1) by the kinetic control of drug release, gastroresistant carnauba wax microspheres loaded with the antiepileptic agent were prepared. The preparation was based on a technique involving melting and dispersion of drug-containing wax in an aqueous medium. The resulting emulsion after cooling under rapid stirring produced solid, discrete, reproducible free flowing microspheres which converted the liquid drug droplets into solid material. About 94% of the isolated microspheres were of particle size range 200-425 μm. The microspheres were analyzed to determine the drug content in various particle size range and to characterize the in vitro release profile. The average drug content was 26% w/w. The intestinal drug discharge of 1 from the carnauba wax microspheres was studied and compared with the release patterns observed for white beeswax and hexadecanol microspheres previously described. The drug release performance was greatly affected by the material used in the microencapsulation process. In the intestinal environment carnauba wax microspheres exhibited more rapid initial rate of release and about 80% of the entrapped drug was discharged in 120 min while complete release occurred in about 8 h.     

Cellulose acetate microspheres as floating depot systems to increase gastric retention of antidiabetic drug: formulation, characterization and in vitro-in vivo evaluation

Gastric emptying is a complex process that is highly variable and makes the in vivo performance of drug delivery systems uncertain. In order to avoid this variability, efforts have been made to increase the retention time of the drug delivery systems for more than 12 hours utilizing floating or hydrodynamically controlled drug delivery systems. The objective of this investigation was to develop a floating, depot-forming drug delivery system for an antidiabetic drug based on microparticulate technology to maintain constant plasma drug concentrations over a prolonged period of time for effective control of blood sugar levels. Formulations were optimized using cellulose acetate as the polymer and evaluated in vitro for physicochemical characteristics and drug release in phosphate buffered saline (pH 7.4), and evaluated in vivo in healthy male albino mice. The shape and the surface morphology of the prepared microspheres were characterized by optical microscopy and scanning electron microscopy. In vitro drug release studies were performed and drug release kinetics were calculated using the linear regression method. Effects of stirring rate during preparation and polymer concentration on the size of microspheres and drug release were observed. The prepared microspheres exhibited prolonged drug release (more than 10 hours) and remained buoyant for over 10 hours. Spherical and smooth-surfaced microspheres with encapsulation efficiency ranging from 73% to 98% were obtained. The release rate decreased and the mean particle size increased at higher polymer concentrations. Stirring speed affected the morphology of the microspheres. This investigation revealed that upon administration, the biocompatible depot-forming polymeric microspheres controlled the drug release and plasma sugar levels more efficiently than plain orally given drug. These formulations, with their reduced frequency of administration and better control over drug disposition, may provide an economic benefit to the user compared with products currently available for diabetes control.     

Enteric-coated epichlorohydrin crosslinked dextran microspheres for site-specific delivery to colon

Abstract

Enteric-coated epichlorohydrin crosslinked dextran microspheres containing 5-Fluorouracil (5-FU) for colon drug delivery was prepared by emulsification-crosslinking method. The formulation variables studied includes different molecular weights of dextran, volume of crosslinking agent, stirring speed, time and temperature. Dextran microspheres showed mean entrapment efficiencies ranging between 77 and 87% and mean particle size ranging between 10 and 25?µm. About 90% of drug was released from uncoated dextran microspheres within 8?h, suggesting the fast release and indicated the drug loaded in uncoated microspheres, released before they reached colon. Enteric coating (Eudragit-S-100 and Eudragit-L-100) of dextran microspheres was performed by oil-in-oil solvent evaporation method. The release study of 5-FU from coated dextran microspheres was complete retardation in simulated gastric fluid (pH 1.2) and once the coating layer of enteric polymer was dissolved at higher pH (7.4 and 6.8), a controlled release of the drug from the microspheres was observed. Further, the release of drug was found to be higher in the presence of dextranase and rat caecal contents, indicating the susceptibility of dextran microspheres to colonic enzymes. Organ distribution and pharmacokinetic study in albino rats was performed to establish the targeting potential of optimized formulation in the colon.     

Release behavior and kinetic evaluation of berberine hydrochloride from ethyl cellulose/chitosan microspheres

Novel ethyl cellulose/chitosan microspheres （ECCMs） were prepared by the method of w/o/w emulsion and solvent evaporation. The microspheres were spherical, adhesive, and aggregated loosely with a size not bigger than 5 pm. The drug loading efficiency of berberine hydrochloride （BH） loaded in microspheres were affected by chitosan （CS） concentration, EC concentration and the volume ratio of V（CS）/V（EC）. ECCMs prepared had sustained release efficiency on BH which was changed with different preparation parameters. In addition, the pH value of release media had obvious effect on the release character of ECCMs. The release rate of BH from sample B was only a little more than 30% in diluted hydrochloric acid （dHCl） and that was almost 90% in PBS during 24 h. Furthermore, the drug release data were fitted to different kinetic models to analyze the release kinetics and the mechanism from the microspheres. The released results of BH indicated that ECCMs exhibited non-Fickian diffusion mechanism in dHCI and diffusion-controlled drug release based on Fickian diffusion in PBS. So the ECCMs might be an ideal sustained release system especially in dHCl and the drug release was governed by both diffusion of the drug and dissolution of the polymeric network.     

近红外荧光磁性复合载药脂质体的制备及应用

拟建立以近红外荧光磁性复合脂质体(NFMSLs)为模型药物载体、盐酸多柔比星(DOX)为包封药物的药物输送系统,研究了近红外荧光磁性载药复合脂质体(DOX-NFMSLs)的制备、性质及初步应用.采用共沉淀法制备FeO4磁流体,CdTe掺杂Se制备近红外量子点CdSeTe,薄膜分散法制备DOX-NFMSLs.用DOX荧光分光光度法测定DOX-NFMSLs的包封率和体外药物释放率;用DOX-NFMSLs与HepG2肝癌细胞共孵育来进行细胞成像和细胞毒性实验.结果表明,近红外CdSeTe量子点粒径约为5nm,闪锌矿结构,发射波长824 nm.磷脂与胆固醇质量比为8∶1,药脂比为1∶20的DOX-NFMSLs平均粒径为252.9 nm,Zeta电位为-48.6 mV,理想释放药物温度为41℃,平均包封率为(74.84±0.89)％.DOX-NFMSLs对HepG2肝癌细胞有一定的抗癌效果.得到了具有良好磁响应、释药温度T=41℃、可近红外成像的载药脂质体.     

可生物降解聚乳酸载青风藤总碱微球的制备工艺

探索青风藤总生物碱微球(CSA-MS)的制备方法并优化制备工艺.采用乳化-溶剂挥发法制备CSA-MS,紫外分光光度法测定MS的包封率和栽药量,扫描电镜观察MS的形貌,粒径测定仪测MS粒径分布情况,并测试药物的体外释放情况.结果显示,MS外观圆整,平均粒径为(21.5±1.22)μm.正交实验优化了MS的制备工艺,其优化...