The Influence of Emulsifers on the Formation of Chitosan Microspheres
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Chitosan microspheres were prepared by emulsion-dispersed chemical-crosslinking method and by using glutaradelhye as crosslinking agent, vacuum-pump oil and paraffin oil mixture as oil phase. The influence of emulsifers on the formation of chitosan microspheres was investigated. The results show that kinds and concentration of emulsifers affect the formation of chitosan microspheres. Under conditions of span-80 and magnesium stearate mixture with mass ration 3:1 as emulsifier, and the total concentration of emulsifier ranged from 10 g/L to 20 g/L, chitosan microspheres are gained with good spherical shape and diameters ranged from 1 m to 5 m.Cite
The experimentation used composite crosslinker (formaldehyde and glutaraldehyde) to prepare tetracycline hydrochloridel chitosan sustained-release microspheres by emulsion cross-linking method. In order to select the optimum technology for preparing chitosan sustained-release microspheres,the influencing factors of drug-carried microspheres were analysed,including the types of chitosan,the mass ratio of raw materials,the dosage of crosslinking agent and the emulsifying speeds. Moreover,the experimentation researched the modality of microspheres by scanning electron microscope and chatelier-type microscope.And the in-vitro release characteristics of microspheres were investigated under the conditions of pH=7.4 and temperature is 37℃. The results suggest that prepared with emulsion cross-linking method in this test, the sphericity of microspheres was good, the diameter of microspheres was from 5-50μm. The drugloading was 26.9%, and the enbedding ratio was 56.3%, and the in vitro release of tetracycline hydrochloridel from the microspheres is sustained.
Glutaraldehyde
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This article presents the results obtained in the encapsulation and the characterization of coriander essential oil microspheres using sodium alginate and alginate/chitosan systems. The coriander essential oil microspheres were obtained in two steps: 1. the oil/water emulsion was prepared, and 2. the extrusion of the emulsion was realized. A Box-Behnken design was used for the preparation of alginate/chitosan microspheres with independent variables: polymer concentration (X1), surfactant concentration (X2), oil concentration (X3) and sonication time (X4) and dependent variables: size of emulsion droplets (Y1), size of microspheres (Y2) and encapsulation efficiency (Y3). The emulsions with the smallest droplets (4.85 µm) have ensured maximum encapsulation efficiency (92.58%). These values were obtained on a concentration of 2% alginate, 1.5% surfactant, 30% coriander oil and 15 minutes ultrasonication. For the Alg/Chi microspheres the maximum value of encapsulation efficiency (97.23%) was obtained for a mass ratio Alg/Chi = 1:2. The shape and surface of alginate, chitosan and alginate/chitosan microspheres were observed by means of optical microscopy and scanning electron microscopy. The release of the coriander oil is correlated with the morphology and the swelling degree of microspheres. At a pH value of 4 and 60 ° C, after 60 minutes, the release rate of the coriander oil was of 4.5% for the alginate microspheres and of 12.75% for the alginate/chitosan microspheres with the alginate/chitosan ratio of 1:2, while at a pH value of 5, on the same conditions of temperature and time, the release rate was higher for both types of microspheres. Temperature positively influences the release rate of the coriander oil.
Sonication
Sodium alginate
Box–Behnken design
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In the present work,four kinds of chitosan-based microspheres with different molecular weight of chitosan were prepared by emulsion-chemical crosslinking method.The characterizations of the microspheres were investigated regarding mean particle size,swelling ratio,drug-loading efficiency,encapsulation efficiency and performance of slow-release.The results indicated that the microspheres prepared with 240kDa of chitosan had higher drug-loading efficiency,higher encapsulation efficiency and more slowly released speed than the other microspheres.The chitosan-solid dispersion microspheres prepared with 240kDa of chitosan increased the solubility of ibuprofen and decreased the speed of drug release.The results revealed that the chitosan-solid dispersion microspheres had potential applications in drug release systems.
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To prepare the Fe3O4 magnetic microspheres with chemical coprecipitation method,the chitosan was used as the dispersant and summarized the optimum preparation conditions.The initial concentration of Fe3+ was 0.15mol/L,where the mole ratio of Fe3+/Fe2+was 1.70-1.75;The precipitant,25% NH3H2O was used 20-30% excessively under pH=9-11,35℃ and with a stirrer speed of 3000r/min for 60min;As dispersant,the optimum dosage of chitosan was 0.0400g each 60mL responding liquid under 50℃ and pH=1.0.No apparent lamination of the chitosan magnetic microspheres had arisen under the above condition after being placed for 17 months.Chitosan magnetic microspheres were characterized by IR,TG-DTA and UV-visible spectrophotometry,etc.
Coprecipitation
Spectrophotometry
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In order to prepare the targeting drug-loaded system,chitosan(CS) 5-fluorouracil((5-Fu))microspheres were prepared in emulsion by using ultrasonic treatment,glutaraldehyde as cross linking agent,span-80 as emulsifer and paraffin oil as oil phase.The condition of preparation has been optimized.The optimum conditions for preparation were as follows: ultrasonic frequency of(40 kHz),2 mL glutaraldehyde,1.0% chitosan and 1.0% 5-fluorouracil.At these conditions,The CS-5-Fu microspheres were characterized by IR,UV-Vis and SEM.The IR results indicate that 5-Fu was loaded.SEM images show that the CS-5-Fu microspheres are spherical shape with diameter's range from 1~ 4 μm.The encapsulated capacity and drug releasing properties were investigated by UVvis spectrum.The results indicate that the drug encapsulation efficiency of Chitosan(CS) 5-fluorouracil(5-Fu) microspheres was 46.7%,and cumulative release percentage in the phosphate buffer(pH = 7.2) solutions was 60.4% in 30 h.
Glutaraldehyde
Liquid paraffin
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2,4-DGelatin/chitosan microspheres were prepared using inversed phase emulsion with dehyde crosslinking. Gelatin /chitosan complexes and liquid paraffin were used as aqueous phase and oil phase,respectively.Pesticide 2,4-dichlorphenoxyacetic acid(2,4-D) was used as core material and Span80 was used as emulsifier.The influence of preparing conditions on the structure and the entrapment efficteney of the microspheres were investigated,as well as the releasing characteristics of 2,4-D from the microspheres.The results indicated that when the dose of emulsifier Span80 was 0.1mL and the mass ratio of oil phase to water phase was 4∶1 with formaldehyde and glutaraldehyde complex as crosslinking agent the pesticide microspheres,which had good dispersion and smooth surfaces with spherical geometry could be prepared.At the same time the entrapment efficiency of 2,4-D was 70.8%.The complex microspheres with a good controlled-release properties to 2,4-D may be applied in the agriculture field as a new pesticide formulation.
Gelatin
Glutaraldehyde
Aqueous two-phase system
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Silver-loaded chitosan microspheres were prepared using emulsified crosslinking method.The morphology,silver content,and encapsulation efficiency of resultant microspheres were examined to investigate the effects of chitosan molecular weight,the amount of emulsifier,ratio of oil and water,and concentration of silver nitrate.The antimicrobial performance of the chitosan microspheres was evaluated by antimicrobial experiments.The results showed that chitosan with lower molecular weight can favor the formation of microspheres and obtain smaller particle size;the diameter of chitosan microspheres is 1 to 3 μm;silver content in chitosan can reach 256 mg/g;and the encapsulation efficiency obtained is 66.8%.Antimicrobial test results showed that the pure chitosan microspheres have certain antibacterial effect against E.coli and S.aureus and the silver-loaded chitosan microspheres bear excellent antibacterial effect.
Silver nitrate
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Chitosan microspheres loaded with 5-fluorouracil were prepared by crosslinking-emulsion method.The effect of the emulsifier,organic diffusion media,reaction time,glutaraldehyde amount,chitosan concentration and 5-fluorouracil concentration on microspheres property was investigated.The results showed that the optimum conditions for preparation were as follows:the ethyl benzoate as organic diffusion media,2ml Span-80,90min,2ml glutaraldehyde,1% chitosan and 1% 5-fluorouracil.At these conditions,the diameter,drug content and drug trapping efficiency of chitosan microspheres were 10～50μm,19.7% and 52.3%,respectively.
Glutaraldehyde
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Membrane emulsification
Glutaraldehyde
Bovine serum albumin
Aqueous two-phase system
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