Encapsulation Efficiency Of Microspheres Research Articles

18F-FDG-PET/CT guiding to diagnosis of neurosarcoidosis

Protein instability during microencapsulation has been one of the major drawbacks of protein delivery systems. In this study, the effects of various excipients (poly vinyl alcohol, glucose, starch, heparin) on the stability of encapsulated human immunoglobulin G (IgG) in poly(ε-caprolactone) (PCL) microspheres and on microsphere characteristics were investigated before and after γ-sterilization. Microspheres formulated without any excipients and with glucose had a mean particle size around 3–4 μm whereas the mean particle sizes of other microspheres were around 5–6 μm. Use of PVA significantly increased the IgG-loading and encapsulation efficiency of microspheres. After γ-irradiation, IgG stability was mostly maintained in the microspheres with excipients compared to microspheres without any excipients. According to the μBCA results, microspheres without any excipient showed a high initial burst release as well as a fast release profile among all groups. Presence of PVA decreased the loss in the activity of IgG released before (completely retained after 6 h and 15.69% loss after 7 days) and after γ-irradiation (26.04% loss and 52.39% loss after 6 h and 7 days, respectively). The stabilization effect of PVA on the retention of the activity of released IgG was found more efficient compared to other groups formulated with carbohydrates.

Pharmacokinetic study of furosemide incorporated PLGA microspheres after oral administration to rat.

The purpose of the current study was to assess the feasibility of microspheres from biocompatible polymer for oral bioavailability (BA) enhancement of potent sulfonamide- type loop diuretic- Furosemide - which used in the treatment of congestive heart failure, caused edema, cirrhosis, renal disease and as an adjunct in acute pulmonary edema. The comparatively poor and inconstant BA of furosemide, which occurs site-specifically in the stomach and upper small intestine, has been ascribed to the poor dissolution of furosemide. In attempt to enhance the drug BA, poly (dl-lactic-co-glycolic acid) (PLGA) microspheres of furosemide were obtained using solvent-evaporation method and the carrier characteristics were investigated subsequently. The in vivo performance of optimum formulation was assessed by pharmacokinetic evaluation of drug after orally administration of free and loaded in microspheres to rats (4 mg/Kg). For this reason, the concentration of drug in plasma was measured by a new developed and sensitive method of HPLC. Acceptable drug loading and encapsulation efficiency of microspheres were obtained to be 70.43 and 85.21 %, respectively. Microspheres provided improved pharmacokinetic parameters (Cmax = 147.94 ng/ml, Tmax = 1.92 hr) in rats as compared with pure drug (Cmax = 75.69 ng/ml, Tmax = 1.5 hr). The obtained AUC of drug in microsphere was 10 fold higher than of the free drug. The results showed that the prepared microspheres successfully improved BA of the poorly water-soluble drug effectively.

Design and Characterization of Mucoadhesive Microspheres for Gastro- Retentive Delivery of Famotidine Hydrochloride

This article illustrates the Design and Characterization of Mucoadhesive microspheres with Famotidine Hydrochloride as drug for Gastro-Retention of drug release. The microspheres were prepared by the Ion Gelation method and Thermal Cross Linking Method. In Ion Gelation method sodium alginate is used as a release controlling biopolymer and Calcium chloride is acts as hygroscopic cross linking agent. In Thermal Cross Linking Method egg albumin is used as binding agent and a Thermal energy is used as cross linking property. The characteristics like shape and structure of prepared microspheres by Optical microscopy and scanning electron microscopy, respectively. In vitro drug release studies were done and drug release was evaluated. Effect on the Mucoadhesion, drug Entrapment Efficiency of microspheres and Drug release were observed. The prepared microspheres exhibited prolonged drug release (17 hrs) the mean particle size increased as the concentration of sodium alginate increased, as the egg albumin concentration increases the Mucoadhesion increased and the drug release rate decreased at higher concentration of sodium alginate. Significant effect of the Encapsulation Efficiency of microspheres was observed. In vitro studies demonstrated the Gastro retentive delivery of drug from the microspheres.

Influence of excipients on characteristics and release profiles of poly(ε-caprolactone) microspheres containing immunoglobulin G.

Protein instability during microencapsulation has been one of the major drawbacks of protein delivery systems. In this study, the effects of various excipients (poly vinyl alcohol, glucose, starch, heparin) on the stability of encapsulated human immunoglobulin G (IgG) in poly(ε-caprolactone) (PCL) microspheres and on microsphere characteristics were investigated before and after γ-sterilization. Microspheres formulated without any excipients and with glucose had a mean particle size around 3-4μm whereas the mean particle sizes of other microspheres were around 5-6μm. Use of PVA significantly increased the IgG-loading and encapsulation efficiency of microspheres. After γ-irradiation, IgG stability was mostly maintained in the microspheres with excipients compared to microspheres without any excipients. According to the μBCA results, microspheres without any excipient showed a high initial burst release as well as a fast release profile among all groups. Presence of PVA decreased the loss in the activity of IgG released before (completely retained after 6h and 15.69% loss after 7days) and after γ-irradiation (26.04% loss and 52.39% loss after 6h and 7days, respectively). The stabilization effect of PVA on the retention of the activity of released IgG was found more efficient compared to other groups formulated with carbohydrates.

Preparation and Structure Characterization of Poly(lactide-co-ethylene carbonate) Microspheres

The purpose of this study was to prepare and characterize tinidazole-loaded poly (lactide-co-ethylene carbonate) (PLEC) microspheres. These biodegradable microspheres were prepared by solvent evaporation method. The effect of selected emulsifier, polymer type, and ratio of tinidazole to PLEC were investigated. An aqueous gelatin solution used as emulsifier resulted in uniform microspheres with spherical surfaces. The PLEC microspheres exhibited rough surface and porous internal structures when compared with the PLA microspheres. The ratio of tinidazole to PLEC (1/10) exhibited higher encapsulation efficiency and drug loading of tinidazole. The introduction of hydrophilic PEC content influenced the structure and encapsulation efficiency of microspheres. These results suggest that the novel PLEC microspheres can be useful for drug delivery systems.

Fabrication and Properties of Gelatin/Chitosan Microspheres Loaded with 5-Fluorouracil

The use of microspheres as drug delivery vehicles for anticancer therapeutics has great potential to revolutionize the future of cancer therapy. The present paper describes the influence of process variables on the encapsulation and loading efficiency of 5-Fluorouracil (5-FU) in gelatin/chitosan (Gel/Cs) microspheres. The influences of preparation parameters, including the contents of the emulsifier Span-80, the cross-linking agent and 5-FU, and the stirring speed, on drug loading and encapsulation efficiency of the microspheres were investigated. The experimental results indicated that drug loading and encapsulation efficiency of microspheres increased with increasing concentration of the cross-linking agent; and then decreased when the concentration of the cross-linking agent was higher than 0.3 ml·g−1 of Gel/Cs. Drug loading and encapsulation efficiency increased with increasing concentration of Span-80; they reached the maximum value when the concentration of the emulsifier was 0.012 g·ml−1. The loading and encapsulation efficiency of the microspheres also increased with increasing stirring speed. In addition, drug loading and encapsulation efficiency increased with increasing concentration of 5-FU; however, the encapsulation efficiency decreased when the concentration of 5-FU was higher than 40 mg·ml−1.

Preparation and characteristics of interferon-alpha poly(lactic-co-glycolic acid) microspheres

By a double emulsion solvent evaporation method, interferon-α (IFN-α) microspheres were prepared with poly(lactide-co-glycolide) (PLGA) and their characteristics, such as morphology, drug loading, encapsulation efficiency, in vitro release and degradation were evaluated. The IFN-α microspheres were prepared by different viscosities from 0.17–1.13 dL g−1 and concentrations between 5–25% of PLGA, which not only affected the drug loading and encapsulation efficiency of IFN-α microspheres, but also strongly influenced the in vitro release. With smooth and porous surface, the drug loading and encapsulation efficiency of the microspheres prepared by 15% 0.89 dL g−1 PLGA were 7.736% and 77.38%, respectively. The DSC curve of microspheres indicated IFN-α was loaded inside the microspheres. The degradation of microspheres was homogeneous and the mass loss was over 80% in 6 weeks. The release profile of microspheres showed a sustained fashion and the IFN-α released from microspheres maintained its bioactivity for 7 days.

Chitosan microspheres as candidate plasmid vaccine carrier for oral immunisation of Japanese flounder ( Paralichthys olivaceus)

Oral DNA-based immunotherapy is a new treatment option for fish immunisation in intensive culture. However, because of the existence of the nucleases and severe gastrointestinal conditions, DNA-based vaccines can be hydrolyzed or denatured. In our laboratory, a plasmid DNA (pDNA) containing major capsid protein (MCP) gene of lymphocystis disease virus (LCDV) was prepared, and then pDNA was encapsulated in chitosan microspheres through an emulsion-based methodology. The yield, loading percent and encapsulation efficiency of microspheres were 93.6%, 0.3% and 94.5%, respectively. Scanning electron microscopy (SEM) showed that pDNA-loaded microspheres yielded a spherical shape with smooth surfaces. The disproportion of super-coiled to open circle and linear pDNA suggested that high transfection efficiencies of pDNA in microspheres were retained. The cumulative release of pDNA showed that chitosan microspheres were resistant to degradation in simulated gastrointestinal tract environment. The release profile at PBS buffer (pH 7.4) displayed that pDNA-loaded chitosan microspheres had a release up to 42 days after intestinal imbibition. RT-PCR showed that RNA containing information of MCP gene existed in various tissues 10–90 days post-vaccination. SDS-PAGE and immunofluorescent images indicated that pDNA expressed MCP in tissues of fish 10–90 days after oral administration. In addition, indirect ELISA displayed that the immune responses of sera were positive (O.D. ≥ 0.3) from week 1 to week 16 for fish vaccinated with microspheres, in comparison with fish vaccinated with naked pDNA. Data obtained suggested that chitosan microspheres were promising carriers for oral pDNA vaccine. Because this encapsulation technique was easy to operate and immunisation efficacy of microspheres loaded with pDNA was significant, it had potential to be used in drug delivery applications.

Preparation and characterization of fenofibrate-loaded PLA–PEG microspheres

A series of biodegradable block copolymer of poly(lactide)(PLA)/poly(ethylene glycol) (PEG) were prepared by Ring-Opening polymerization of D, L-lactide, using stannous octoate as a catalyst. By nanoprecipitation method, the PLA-PEG can be made into microspheres containing fenofibrate, which is a kind of important cholesterol-lowering drugs. The purpose of this study is to investigate the effect of the copolymer composition on the size, the entrapment and the release behavior of the fenofibrate loaded microspheres. The microspheres can be achieved with small size below 100 nm, better encapsulation efficiencies of more than 55.3% and slower release rates. The release of fenofibrate from microsphere would reach the balance first, when the microsphere prepared by high proportion of hydrophilic PEG block. And the release property of fenofibrate/PLA-PEG microsphere was better than Lipanthyl (a commercial capsule of fenofibrate). It was observed that the composition of PLA-PEG copolymer played a major role in encapsulation efficiency of microspheres and release rates.

Poly(D,L-lactide-co-glycolide) microspheres containing 5-fluorouracil: optimization of process parameters.

The objective of this research was to optimize the processing parameters for poly(D,L-lactide-co-glycolide) (PLGA) microspheres of 5-fluorouracil (5-FU) and to mathematically relate the process parameters and properties of microspheres. Microspheres were prepared by a water-in-oil-in-water emulsion solvent evaporation technique. A 3(2) factorial design was employed to study the effect of the volume of the internal phase of the primary emulsion and the volume of the external phase of the secondary emulsion on yield, particle size, and encapsulation efficiency of microspheres. An increase in the volume of the internal phase of the primary emulsion resulted in a decrease in yield and encapsulation efficiency and an increase in particle size of microspheres. When the volume of the external phase of the secondary emulsion was increased, a decrease in yield, particle size, and encapsulation efficiency was observed. Microspheres with good batch-to-batch reproducibility could be produced. Scanning electron microscopic study indicated that microspheres existed as aggregates.

PEG modulated release of etanidazole from implantable PLGA/PDLA discs

In this work, etanidazole (one type of hypoxic radiosensitizer) is encapsulated into spray dried poly( d, l-lactide-co-glycolide) (PLGA) microspheres and then compressed into discs for controlled release applications. Etanidazole is characterized by intracellular glutathione depletion and glutathione transferases inhibition, thereby enhancing sensitivity to radiation. It is also cytotoxic to tumor cells and can chemosensitize some alkylating agents by activating their tumor cell killing capabilities. We observed the release characteristics of etanidazole in the dosage forms of microspheres and discs, subjected to different preparation conditions. The release characteristics, morphology changes, particle size, and encapsulation efficiency of microspheres are also investigated. The release rate of etanidazole from implantable discs (13 mm in diameter, 1 mm in thickness, fabricated by a press) is much lower than microspheres due to the reduced specific surface. After the initial burst of 1% release for the first day, the cumulative release within the first week is less than 2% until a secondary burst of release (caused by polymer degradation) occurs after one month. Some key preparation conditions such as drug loadings, disc thickness and diameter, and compression pressure can affect the initial burst of etanidazole from the discs. However, none of them can significantly make the release more uniform. In contrast, the incorporation of polyethylene glycol (PEG) can greatly enhance the release rate of discs and also reduces the secondary burst effect, thereby achieving a sustained release for about 2 months.