Biodegradable cross-linked starch/protein microcapsules containing proteinase inhibitor for oral protein administration.

The objective of this study is to demonstrate the feasibility of microcapsules containing a protein and a proteinase inhibitor in order to allow the oral administration of proteic or peptidic drug. Starch/bovine serum albumin mixed-walled microcapsules were prepared using interfacial cross-linking with terephthaloyl chloride. The microcapsules were loaded with native or amino-protected aprotinin by incorporating protease inhibitors in the aqueous phase during the cross-linking process. Microcapsules can be degraded in the presence of alpha-amylase. The influence of the formulation parameters on the in vitro release of the inhibitor activity and the protein was studied. The protective effect of microcapsules with aprotinin for bovine serum albumin was revealed in vitro. The presence of the native bovine serum albumin was demonstrated after incubation of the microcapsules with aprotinin in a mixture of alpha-amylase (5.4 U/ml) and trypsin (900 spectrophotometric BAEE units/ml) for 3 h at 37 degrees C, whereas the protein was completely degraded in the release medium of the microcapsules without aprotinin.     

Preparation of serum albumin microcapsules

Simple coacervation of bovine serum albumin was studied to prepare biodegradable microcapsules. Three types of microcapsules, which differed in shape, were obtained by changing either core size or the bovine serum albumin concentrations of the coacervating systems. Mononuclear microcapsules were prepared by using spherical poly(acrylonitrile) beads as a core material.     

In-vitro cytotoxic activity of cross-linked protein microcapsules

Microcapsules (5-100 microns) were prepared through interfacial cross-linking of various proteins (human serum albumin, lysozyme, haemoglobin, casein, pepsin) with glutaraldehyde or terephthaloylchloride. Surprisingly they all showed an inhibitory effect on cultured cells in a concentration range of 100 micrograms ml-1 to 10 mg ml-1. This effect seemed non-specific, reversible and to depend on contact with the cell plasma membrane. The electric charges of microcapsules could be involved in the inhibition phenomenon.     

The effect of cross-linked protein microcapsules on cell cultures

Microcapsules (diameter range: 5 to 100 microns) prepared through interfacial cross-linking of proteins with terephthaloylchloride exhibited a cytotoxic effect on L 1210 cell cultures. IC50 was: 0.86 mg/ml +/- 0.24 for microcapsules prepared from human serum albumin (AT microcapsules) and 0.63 mg/ml +/- 0.05 for those obtained from egg white lysozyme (LT microcapsules). With K 562 cells IC50 were 0.42 +/- 0.11 mg/ml (AT microcapsules), 0.06 mg/ml (LT microcapsules). An increase in the cytotoxicity was observed when reducing the size of the microcapsules and when increasing the reaction pH or the terephthaloylchloride concentration, or the relative concentration of microcapsules vs cells. On the contrary, the cytotoxic effect decreased, when prolonging the cross-linking time. The activity was not affected when the microcapsules were washed with toluene or with an alkaline solute. The cytotoxic effect, which appears for relatively high doses, apparently involves a contact between the microcapsules and the cells and seems to be related with the degree of cross-linking of the constitutive protein.     

In vitro drug release from egg albumin microcapsules

The in vitro release of phenacetin from microcapsules prepared using egg albumin as the membrane material was investigated. It was shown by scanning electron microscopy that the albumin microcapsules have nonsmooth surfaces. The amount of phenacetin released is proportional to the square root of time up to 50-70% drug release. Increases in the albumin concentration and 1-vinyl-2-pyrrolidinone polymer content in the aqueous phases used in the microcapsule preparation have an effect on matrix porosity and channel tortuosity in the matrix of albumin microcapsules. The in vitro release rate was found to decrease with increasing albumin concentration and 1-vinyl-2-pyrrolidinone polymer content in the aqueous phases. The in vitro release rate per unit area also decreased with decreasing capsule size.     

Binding mechanism of doxorubicin in ion-exchange albumin microcapsules

The absorption efficiency of cross-linked albumin microcapsules was evaluated as a function of various experimental conditions in an attempt to elucidate the doxorubicin binding mechanism of these microcapsules. The amount of drug absorbed augmented with increasing doxorubicin concentration until saturation was reached. Neither a Langmuir nor a Freundlich isotherm relationship was observed, indicating that the fixation of doxorubicin on the microcapsule walls did not follow a common physical adsorption process. Decreasing the mean particle diameter of the microcapsules increased the absorption rate and the total amount of doxorubicin absorbed, as expected. The absorption rate was enhanced by the elevation of the stirring rate of the aqueous drug solution. Furthermore, the presence of electrolytes in this aqueous solution profoundly altered the absorption profile of doxorubicin. Increasing the NaCl concentration in the solution reduced the total amount of drug absorbed. Moreover, the nature of the cation used also affected the absorption profile. These results suggested that there is a competitive fixation of the cation on the binding sites (identified as R-COO groups) available to the drug molecules. The weakly cross-linked microcapsules acted as cation-exchange resins which can exchange their labile sodium with the protonated drug present in the solution. This was also confirmed by the results of the titrimetric assay of the acidic microcapsules with NaOH.     

Membrane formation mechanism of cross-linked polyurea microcapsules by phase separation method

This research was conducted to clarify the membrane formation mechanism of cross-linked polyurea microcapsules by phase separation method, especially the role of polymeric surfactant, such as poly(ethylene-alt-maleic anhydride) (poly(E-MA)) at the interface of O/W emulsion. It was found that poly(E-MA) was necessary for the formation of cross-linked polyurea membrane. The addition of sodium dodecyl sulphate (SDS) prohibited the membrane formation reaction at the interface, even in the case of poly(E-MA) concentration enough for polymeric microcapsule formation. From the results in this study, poly(E-MA) was found to be adsorbed on the O/W emulsion and provide the reaction site for the membrane formation of polymeric microcapsules.     

Membrane formation mechanism of cross-linked polyurea microcapsules by phase separation method

This research was conducted to clarify the membrane formation mechanism of cross-linked polyurea microcapsules by phase separation method, especially the role of polymeric surfactant, such as poly(ethylene-alt-maleic anhydride) (poly(E-MA)) at the interface of O/W emulsion. It was found that poly(E-MA) was necessary for the formation of cross-linked polyurea membrane. The addition of sodium dodecyl sulphate (SDS) prohibited the membrane formation reaction at the interface, even in the case of poly(E-MA) concentration enough for polymeric microcapsule formation. From the results in this study, poly(E-MA) was found to be adsorbed on the O/W emulsion and provide the reaction site for the membrane formation of polymeric microcapsules.     

Optimization and characterization of chitosan-coated alginate microcapsules containing albumin

In order to obtain small microcapsules with high protein encapsulation efficiency and extended release characteristics various processing factors were studied. Bovine serum albumin-loaded alginate microcapsules were prepared by an emulsion method and further incubated in chitosan. Many process factors were tested including the concentration and molecular weight of alginate, the concentration and pH of chitosan, and surfactants, etc. Microcapsules were achieved with diameters less than 2 microm, high encapsulation efficiency (> 80%) and high loading rate (> 10% w/w). The results also showed that the initial BSA amount of 20%-30% loaded alginate microcapsules coated with 0.2%-0.5% chitosan solutions at pH 4 by the two-stage procedure present the best sustained releasing characteristics.     

Mixed-wall microcapsules made of cross-linked proteins and polysaccharides: preparation and properties

Microcapsules were prepared through an interfacial cross-linking process using terephthaloylchloride and applied to mixtures of a protein (human serum albumin or gelatin) and a polysaccharide. Their properties were compared with those of microcapsules prepared from the protein alone. Morphological characteristics of mixed-walled microcapsules were often modified, as seen by light and electron microscopy. Otherwise, they appeared to be more resistant to digestive media: they were gastroresistant, and their degradation time in pancreatin was prolonged upon raising the amount of polysaccharide. Moreover, the lysis time was shown to depend on the nature of the polysaccharide: microcapsules prepared from acidic polysaccharides at pH 9.8 were hydrolyzed faster. Lastly, the resistance increased upon decreasing the polymers/acylchloride ratio, or upon raising the reaction pH. Encapsulation assays were carried out with sodium salicylate, which was incorporated with a high efficiency. Mixed-walled microcapsules allowed a prolonged release of the tracer in vitro. As compared with protein microcapsules, the release profiles of batches prepared with hydroxyethylstarch exhibited only slight modifications of the initial part of the curve, while a significant burst effect was observed with carboxymethylcellulose-containing microcapsules.     

栓塞颌面血管瘤动脉的平阳霉素白蛋白微球的制备

目的　制备平阳霉素白蛋白微球 ,提高平阳霉素抑制血管瘤的作用。方法　以化学交联法在单因素考察的基础上进行均匀试验设计 ,筛选出栓塞血管瘤动脉的平阳霉素白蛋白微球的最佳制备工艺 ,考察了微球的形态和粒度分布及体外释药特性。结果　化学交联法制得的微球表面圆整、光滑 ,平均粒径为 83.6± 10 .5 μm ,药物平均包封率为 34.3% ;载药量为4 0 .2 % ;释药特性可用Higuichi和单指数方程描述。结论　以化学交联法制备的平阳霉素白蛋白微球粒径符合栓塞要求 ,体外具有明显缓释效果。     

The incorporation and release of bovine serum albumin from poly-hydroxybutyrate-hydroxyvalerate microcapsules

Abstract

Spherical microporous reservoir type microcapsules composed of P(HB-HV) (10·8% HV)/20% PCL containing BSA (surrogate protein) loaded agarose have been fabricated using a double emulsion technique with solvent evaporation. Microcapsules were generated in high yield (> 75 wt%) and BSA incorporation had no significant effect on microcapsule size distribution (21–200 μm). The loss of BSA both by partitioning into the aqueous continuous phase, and through micropores as BSA-loaded-agarose during the precipitation of the fabrication polymer concomitant with solvent evaporation, resulted in low encapsulation efficiency (12%). The amount and duration of BSA release was influenced as much by micropore numbers and diameter as by the extent of reservoir loading and detectable levels of BSA release could be monitored for up to 24 days.     

An evaluation of albumin microcapsules prepared using a multiple emulsion technique

Albumin microcapsules containing sulphadiazine were prepared using a multiple emulsion technique. Heat was utilized to denature the albumin and form the capsule shell. Albumin microcapsules prepared using this technique were free-flowing, spherical in shape, and had varying degrees of vacuolation. The effects of drug: polymer ratio and concentration of cross-linking agent on the percentage of drug retained in the microcapsules and release of drug from the microcapsules were studied. Also, the effect of viscosity of the innermost oil layer, of the multiple emulsion, upon the mean diameter of the microcapsules and release of drug from the microcapsules was investigated.     

Preparation and characterization of Pingyangmycin-loaded bovine serum albumin microspheres for embolization therapy

Bovine serum albumin microspheres (BSA-MSs) containing Pingyangmycin hydrochloride (PYM) were prepared for the interventional embolization by an emulsification-crosslinking method. The average diameter of the MSs was 83.6 microm with 80% ranging from 35 to 200 microm. The MSs showed a rather high entrapment efficiency (EE%) of 87.6+/-5.7% and the drug loading efficacy (DL%) was 20.2+/-1.3%. The drug release behaviors were evaluated both in vitro and in vivo, using UV-spectroscopy and HPLC, respectively. The in vitro results showed a significantly delayed release of drug for 10 days. The central auricular artery of rabbit was chosen as an embolization sites to study the in vivo drug release and the pharmacokinetics of the MSs compared with PYM injections. Experiments performed by artery perfusion and embolization in rabbits central auricular artery revealed that the PYM loaded BSA-MSs (PYM-BSA-MSs) could obviously prolong in vivo drug release, extend the mean residence time (MRT) and had equal bioavailability compared with plain PYM injections. These results demonstrated that by embolization of the central auricular artery with PYM-BSA-MSs, the local drug concentration could maintain at a relative high level for a longer time, thus achieve the aim of tumor targeting therapy. PYM-BSA-MSs are excellent potential alternatives of interventional embolization materials for the treatment of maxillofacial region tumors.     

Preparation of genipin cross-linked chitosan-gelatin microcapsules for encapsulation of Zanthoxylum limonella oil (ZLO) using salting-out method

Zanthoxylum limonella oil (ZLO) containing chitosan-gelatin complex microcapsules cross-linked with genipin, a cross-linker of natural origin, have been prepared by a complex coacervation process using the salting-out method. The effects of various parameters such as oil loading, degree of cross-linking, ratio of chitosan to gelatin, etc. on oil content, encapsulation efficiency and the release rate of ZLO have been studied. FT-IR spectroscopy has been used to understand the interaction between the polymers and oil. Scanning electron microscopy (SEM) has been employed to study the morphology of the prepared microcapsules.     

Preparation of genipin cross-linked chitosan-gelatin microcapsules for encapsulation of Zanthoxylum limonella oil (ZLO) using salting-out method

Zanthoxylum limonella oil (ZLO) containing chitosan-gelatin complex microcapsules cross-linked with genipin, a cross-linker of natural origin, have been prepared by a complex coacervation process using the salting-out method. The effects of various parameters such as oil loading, degree of cross-linking, ratio of chitosan to gelatin, etc. on oil content, encapsulation efficiency and the release rate of ZLO have been studied. FT-IR spectroscopy has been used to understand the interaction between the polymers and oil. Scanning electron microscopy (SEM) has been employed to study the morphology of the prepared microcapsules.     

肺鞍向汉防己甲素缓释微囊的小鼠体内分布

目的：测定汉防己甲素在体内样品中的浓度,研究汉防己甲素经微囊化后的体内分布特点。方法：建立样品中江防己甲素浓度测定的RP-HPLC法,对比汉防己甲素水针剂和微囊混悬液经小鼠尾静脉注射后,不同时间时汉防己甲素的浓度值,分析药物的肺靶向性。结果：生物样品检验方法简便易行,结果准确,微囊化汉防己甲素在肺中的浓度明显提高,且缓慢降低,具有明显的肺靶向性。结论：汉防己甲素经微囊化后,可浓集于肺部,且具有缓慢释放的特点,对肺动脉高压的防治具有重要意义。     

In vitro degradation of serum albumin microcapsules: effect of process variables

Microcapsules were prepared by cross-linking of human serum albumin (HSA) with terephthaloyl chloride (TC). Reaction pH was increased from 5.9 to 11, using 2.5% TC and 30 min reaction time. Then, in two series of assays conducted at pH 9.8, TC concentrations were varied from 0.5 to 5% (with 30 min reaction time), and reaction time was increased from 2 to 60 min (with 2.5% TC). Finally, two series of experiments were performed at pH 7.4 and 8, respectively, combining 2.5 and 5% TC with 30 and 60 min reaction time. Microcapsule degradation in pepsin (pH 1.2), and in trypsin (pH 7.5) was studied by microscopic examination. In the pH series, microcapsules prepared at pH ≤8 were degraded by pepsin within 50–70 min, while those obtained at pH ≥9 were resistant. Solubilisation time in trypsin was 3–10 min for pH ≤8, and 20–40 min for pH ≥9. At pH 9.8, resistance to pepsin was observed whatever the reaction time and the TC concentration, while solubilisation time in trypsin was 15–30 min. At pH 7.4 or 8, microcapsules were degraded in pepsin (50–70 min) and in trypsin (8–15 min). The results demonstrate the determining influence of reaction pH on microcapsule degradation. Besides, a correlation was found between microcapsule sensitivity to pepsin and high–NH₂ contents found in previous studies.     

Ion-exchange albumin microcapsules of doxorubicin: an in vitro release kinetic evaluation

Cross-linked albumin microcapsules were prepared, using a polycondensation interfacial process. Doxorubicin was incorporated in these microcapsules by simple adsorption from aqueous solution. Increasing the extent of cross-linkage of the microcapsule walls by either increasing the cross-linking agent concentration or the time of reaction significantly reduced the absorption ability of these microcapsules. Doxorubicin release kinetic evaluation revealed that the presence of a salt in the release medium was needed to enable much of the drug to be released. Furthermore, the doxorubicin displacement intensity from the microcapsules was dependent on the nature and concentration of the cations used, indicating that an ion-exchange process was involved. Analysis of the various doxorubicin release profiles, using ion-exchange kinetic equation, showed that the release kinetic process is governed by a film diffusion process at low and moderate Na+ ion concentrations in the exchanging solution, and by a particle diffusion process at high Na+ ion concentrations, sufficient to drive the doxorubicin exchange to completion.