Release Behavior Of Microspheres Research Articles

Neovascularization by Sustained Delivery of G-CSF, EPO and VEGF Using Dextran/PLGA Microspheres

Therapeutic neovascularization has some obstacles, such as it requires more than one proangiogenic factor, and these factors have short half-lives. To overcome these obstacles, combined delivery of granulocyte-colony stimulating factor (G-CSF), erythropoietin (EPO) and vascular endothelial growth factor (VEGF) using protein/dextran/poly (lactic-co-glycolic acid) (PLGA) sustained-release microspheres was proposed to promote neovascularization. Dextran microparticles loaded with G-CSF, EPO or VEGF were prepared and encapsulated in PLGA microspheres to obtain protein-dextran-PLGA microspheres. The release behavior of microspheres was studied invitro. The protein/dextran/PLGA microspheres were injected into the ischemic hindlimbs of rats. Neovascularization in ischemic muscle was measured. Microspheres released G-CSF, EPO and VEGF invitro for more than 4weeks. Combined therapy with VEGF, EPO and G-CSF promoted the expression of B-cell lymphoma-2 and stromal cell-derived factor 1, cellular proliferation and the incorporation of C-X-C chemokine receptor 4 positive cells. Capillary density and smooth muscle α-actin+vessel density were higher in the combined treatment of VEGF, EPO and G-CSF than in the single factor treatment. The combined and sustained delivery of VEGF, EPO and G-CSF using dextran-PLGA microspheres had a more significant neovascularization effect than monotherapy with each factor alone. This combined therapy might be a promising treatment for ischemic vascular diseases.

Effect of Calcium Chloride on Release Behavior of Babul (Acacia nilotica) gum Microbeads.

Oral delivery of drugs is the most common method, but due to the inability of drugs to restrain and localize in the gastro-intestinal tract, oral administration of drugs in conventional dosage forms have short-term limitations. Carrier technology may provide many approaches for the delivery of drugs by coupling the drug to a carrier particle, such as Microspheres, nanoparticles and liposomes, which modulate the release and absorption characteristics of the drug. The aim of this study was to prepare Diclofenac sodium microspheres using a natural polymer and show the effect of calcium chloride on the release behavior of microspheres. The microspheres of Diclofenac sodium were successfully developed by ionic gelation technique using natural polymer babul gum with sodium alginate. Diclofenac Sodium was received as a gift sample from Aegis Pharmaceuticals Pvt. Ltd., Roorkee. Acacia nilotica gum was purchased from Ghaziabad and purification was done in the laboratory. All other excipients used analytical grade method. The microspheres of diclofenac sodium were prepared by Ionic gelation method using a natural polimer, i.e. Acacia nilotica. Calcium chloride (5% solution) was used as a cross-linking agent. In this research article all the data was presented as averages and standard deviations. Five formulations were successfully prepared, i.e. F1, F2, F3, F4 and F5. All the formulations were evaluated for micromeritic properties, particle size analysis, percentage yield, drug content, drug entrapment efficacy, percent moisture loss, swelling index and in vitro dissolution studies. The size of the microspheres varied between 14.55 ± 0.29 to 20.18 ± 0.15 μm and as high as 81.51 ± 0.14% entrapment efficiency for babul gum was obtained. Batch F1 and F5 was found to release the drug 91.35% and 75.48% respectively for 6 hrs. The formulations were found to be effective in providing controlled release of drug for a prolonged period of time.

Preparation and investigation the release behaviour of wax microspheres loaded with salicylic acid

Salicylic acid-beeswax microspheres were prepared by melt dispersion technique. The effects of formulation parameters on the microscopic characteristic, drug loading and cumulative amount of released drug were investigated by experimental design. Results showed that all of the microparticles were spherical with porous surfaces. The average size of microspheres was 24–48 µm, the drug content was in the range of 22–45% and the encapsulation efficiency was 46–93%. Drug loading was influenced by emulsification speed as a main factor. All the microspheres had a burst release initially. The emulsifier concentration did not have a significant effect on drug release. The release behaviour of microspheres conformed best to Korsmeyer-Peppas semi-empirical model and the release of SA from beeswax microspheres was Fickian (n < 0.45).

Pectin-based microspheres for colon-specific delivery of vancomycin

The aim of this study was to describe a colon-specific delivery system based on pectin hydrogels formed by complexation with chitosan. Hydrogels were prepared at different weight ratios (4:1, 7:1, 10:1; pectin/chitosan), loaded with vancomycin hydrochloride (2:1, 4:1; polymer/drug weight ratio) and collected by spray-drying. The microspheres obtained were characterized in terms of morphology, swelling behaviour, mucoadhesive properties and drug loading efficiency. The influence of different pectin/chitosan hydrogels on the release behaviour of microspheres at pH 2.0, 5.5 and 7.4 were evaluated in vitro with and without pectinolytic enzyme. The results showed that water uptake was increased by raising the environmental pH (from 2.0 to 7.4) and the pectin/chitosan weight ratio, while drug availability was increased by raising the environmental pH (from 2.0 to 7.4) and decreased by raising the pectin/chitosan weight ratio. In the presence of pectinase, the glycoside bonds of pectin were degraded and a considerable amount of drug was released in a short time. This study suggested that pectin/chitosan microspheres were able to limit the release of vancomycin under acidic conditions and release it under simulated colonic conditions, confirming their potential for a colon-specific drug delivery system.

Pectin-based microspheres for colon-specific delivery of vancomycin

Abstract Objectives The aim of this study was to describe a colon-specific delivery system based on pectin hydrogels formed by complexation with chitosan. Methods Hydrogels were prepared at different weight ratios (4: 1, 7: 1, 10: 1; pectin/chitosan), loaded with vancomycin hydrochloride (2: 1, 4: 1; polymer/drug weight ratio) and collected by spray-drying. The microspheres obtained were characterized in terms of morphology, swelling behaviour, mucoadhesive properties and drug loading efficiency. The influence of different pectin/chitosan hydrogels on the release behaviour of microspheres at pH 2.0, 5.5 and 7.4 were evaluated in vitro with and without pectinolytic enzyme. Key findings The results showed that water uptake was increased by raising the environmental pH (from 2.0 to 7.4) and the pectin/chitosan weight ratio, while drug availability was increased by raising the environmental pH (from 2.0 to 7.4) and decreased by raising the pectin/chitosan weight ratio. In the presence of pectinase, the glycoside bonds of pectin were degraded and a considerable amount of drug was released in a short time. Conclusions This study suggested that pectin/chitosan microspheres were able to limit the release of vancomycin under acidic conditions and release it under simulated colonic conditions, confirming their potential for a colon-specific drug delivery system.

시부트라민 고체 분산체의 특성화 및 조절된 방출거동

Solid dispersions of poorly water-soluble drug, sibutramine, were prepared with hydrophilic polymer, poly-N-vinylpyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC) and organic acid, citric acid, to improve the solubility of drug. Physicochemical variation and shape of microsphere were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FT-IR). Microspheres containing additives showed more spherical shape than non additive microspheres. In vitro release behavior of microspheres presented at simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). The solid dispersion form transformed the drug into an amorphous state and dramatically improved its dissolution rate. These data suggest that the solid dispersion technique is an effective approach for developing the appetite depressant drug products and various pharmaceutical excipients are able to control the release behaviors.

Release behavior of microspheres from cross-linked N-methylated chitosan encapsulated ofloxacin

Abstract A series of hollow microspheres encapsulated with ofloxacin have been successfully prepared, using cyclohexane droplets as a template and the N-methylated chitosan (NMC) cross-linked with glutaraldehyde as the shell. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The swelling and releasing behaviors of the microspheres having different weight-average molecular weights (Mw) and the degree of quaternization of NMC at pH 1.2 and 7.4 media were investigated. The results revealed that microspheres exhibited a very smooth surface, and electrostatic interaction existed between cross-linked NMC and ofloxacin. Ofloxacin encapsulated in the microspheres was rapidly released into phosphate buffer solution (pH 7.4), whereas it was only slowly released in 0.1 M HCl (pH 1.2). The degree of swelling of microspheres at pH 7.4 was higher than that at pH 1.2. Moreover, ofloxacin was released more slowly from the microspheres having high Mw of NMC than that with low Mw. The release mechanism of the hollow microsphere was proposed to be a non-Fickan diffusion through the swollen microspheres, and to be controlled by the Mw and the cross-linking density of shell.

Morphology of and release behavior from porous polyurethane microspheres

A novel biomaterial application of porous microspheres is for sustained delivery of biologically active agents. Recent studies have pointed out the importance of biomaterial porosity in promoting biocompatibility and controlling release rate of active agents. The objective of this research was to investigate the effect of chain-extending agent on the porosity and release behavior of polyurethane (PU) microspheres prepared using a two-step suspension polycondensation method with methylene diphenyl diisocyanate (MDI) as the isocyanate, polyethylene glycol (PEG400) as the diol, and 1,4-butanediol as the chain-extending agent. Chain-extending agent was used to increase the ratio of hard to soft segments of the PU network, and its effect on microsphere morphology was studied with scanning electron microscopy. According to the results, porosity was significantly affected by the amount of chain-extending agent. The pore size decreased as the concentration of chain-extending agent increased from zero to 50 mole%. With further increase of chain-extending agent to 60 and 67%, PU chains became stiffer and formation of pores was inhibited. Therefore, pore morphology was significantly affected by variations in the amount of chain-extending agent. The release behavior of microspheres was investigated with diazinon as the active agent. After an initial burst, corresponding to 3% of the incorporated amount of active agent, the release rate was zero order.

Preparation of enteric-coated microspheres ofMycoplasma hyopneumoniaevaccine with cellulose acetate phthalate: (II). Effect of temperature and pH on the stability and release behaviour of microspheres

The in vitro stability (temperature and pH) and dissolution study (pH 7.4 phosphate buffer solution and pH changed medium) of the enteric-coated microspheres containing Mycoplasma hyopneumoniae vaccine (MHV) were examined. The MHV microspheres were thermally more stable than the unencapsulated MHV. More than 90% of antigenicity was retained in the MHV microspheres for 3 weeks when stored at 4 degrees C. The MHV microspheres in pH 1.2 and pH 3.0 medium were more stable than the unencapsulated MHV. The MHV enteric-coated microspheres exhibited an excellent enteric function to prevent pH-related inactivation. The influence of particle size, CAP concentration and span 80 concentration on the MHV released from microspheres was also determined. The smaller the particle size, the higher the dissolution rate due to the larger surface area of the smaller particle. The higher the concentration of span 80 used, the more the greater the amount of MHV released. This was attributed to the more porous structure of microspheres prepared by the higher concentration of span 80. By increasing the CAP concentration, however, the release rate of MHV was decreased due to the larger amount of CAP and the more compact structure of microspheres.