Preparation and characterization of microspheres of albumin-heparin conjugates

Kwon, Glen S.; Bae, You Han; Kim, Sung Wan; Cremers, H.F.M.; Feijén, Jan

doi:10.1016/0021-9797(91)90283-e

Cited by 13 publications

(4 citation statements)

References 18 publications

(18 reference statements)

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“…This can be explained by increased retractive forces at increased crosslink densities, which prevent the hydrogel from expanding. Previously this was also observed with AHCMS of which the degree of swelling decreased with increased crosslink density [10,33]. Fig.…”

Section: Preparation and Adriamycin Loading And Release Properties Ofsupporting

confidence: 74%

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Biodegradable ion-exchange microspheres based on modified polylysines

Cremers

Lens

Seymour

et al. 1995

Journal of Controlled Release

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Poly-L-lysine was synthesized via a triethylamine initiated ring-opening polymerization of Z-L-lysine-N'~-carboxyanhydride, followed by deprotection of the E-amino group. Subsequently the polylysine was sulfamated using a pyridinium-sulfate complex to obtain polymers with varying degrees of sulfamation ranging from 0 to 100%. Cytotoxicity of these materials was tested using tetrazolium metabolism (MTI') assays with B16F10 and P388 cell lines. Cytotoxicity of sulfamated polylysines with a degree of sulfamation of 80% and higher was significantly reduced as compared with the native polylysines. In both cell lines, LDso of the sulfamated materials was higher than 5 mg/ml, which was the highest dose tested. LDso of the native polylysines was lower than 0.1 mg/ml in the case of B16F10 and lower than 0.01 mg/ml in the case of P388 cells. Sulfamated polylysines with a degree of sulfamation of 80% were used to prepare microspheres (SPLMS). The microspheres were stabilized using glutaraldehyde or oxidized dextran as a crosslinking agent. The swelling ratio (defined as V~wollen/Vdr~ed) of the SPLMS in aqueous media decreased with increasing ionic strength and crosslink density. The pH (ranging from 3 to 11) had no influence on the swelling ratio of SPLMS. The maximal swelling ratio was approximately 35 (SPLMS crosslinked with 0.5% glutaraldehyde in distilled water). SPLMS could be loaded with adriamycin up to a payload of 60%, which was not influenced by the crosslinking method. The adriamycin release was controlled by the ionic strength of the release medium: no drug was released in non-ionic medium such as distilled water, while 80% of the drug was released in phosphate buffered saline. This effect of the change in ionic strength could be applied to prepare a microsphere suspension in non-ionic medium such as 5% glucose solution, which does not contain free adriamycin. The drug would only be release after intra-arterial administration of this suspension, due to the presence of the blood.

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Section: Preparation and Adriamycin Loading And Release Properties Ofsupporting

confidence: 74%

“…AHCMS were shown to have a maximal swelling ratio of 11 [ 10,33], whereas the maximal swelling ratio of SPLMS was almost 35. Chemoembolization therapy requires microspheres with a diameter of 10-50 ~m in the swollen state.…”

Section: Preparation and Adriamycin Loading And Release Properties Ofmentioning

confidence: 95%

Biodegradable ion-exchange microspheres based on modified polylysines

Cremers

Lens

Seymour

et al. 1995

Journal of Controlled Release

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“…PVP (% w/v) Number-Weight Mean Diam ± SD (µm) (n ) 9) 2.0 3.59 ± 1.09 1.0 3.62 ± 0.82 0. 5 3.53 ± 0.60 0 3.60 ± 1.60 …”

Section: Discussionmentioning

confidence: 97%

“…4 To form microcapsules, the coacervate phase is dispersed in the equilibrium phase, and the resulting coacervate droplets are stabilized using cross-linking agents or the application of heat. 2 Recently Kwon et al 5 have developed an albumin/heparin microencapsulation method which involves conjugation of the carboxyl groups of heparin with the amine groups of albumin by a condensation reaction using [1-ethyl-3-(dimethylamino)-propyl]carbodiimide. These heparin/albumin conjugate microcapsules are stabilized by glutaraldehyde cross-linking.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Stabilization of Heparin/Gelatin Complex Coacervate Microcapsules

Tsung

Burgess

1997

Journal of Pharmaceutical Sciences

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The aims of this study are to optimize conditions for the preparation, stabilization, and harvesting of heparin/gelatin microcapsules prepared by complex coacervation. Microelectrophoresis and dry coacervate weight were used to determine the optimum conditions of pH and ionic strength for maximum heparin/gelatin coacervate yield. Heparin/gelatin microcapsules were formed by complex coacervation in the presence and absence of poly(1-vinyl-2-pyrrolidone) (PVP), which was used as a stabilizer. The microcapsules were collected using a spray-drying technique. Microcapsule particle size was analyzed using an AccuSizer optical sizer. Optimized conditions for maximum coacervate yield were pH 2.6, ionic strength 10 mM, and a 1:2 heparin/gelatin A ratio. PVP stabilized the heparin/gelatin coacervate droplets and reduced droplet aggregation during spray-drying. The mean particle diameter of the spray-dried coacervate droplets was lower in the presence of PVP and was unaffected by PVP concentration (in the range 0.5-2.0% w/w). Heparin/gelatin microcapsules, prepared under conditions optimized for maximum coacervate yield, were stabilized without the use of chemical cross-linking agents. Stabilization was achieved by a combination of the addition of PVP and spray-drying.

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On the assessment of hydrogels for fluid absorbency

Dave¹,

Vaishnav²,

Desai³

et al. 1995

J of Applied Polymer Sci

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Hydrogels are capable of absorbing fluids like water to the extent of several fold. Since this is an important characteristic property of any hydrogel, it is necessary to employ a simple and accurate method for its assessment. Several methods reported in the literature have been discussed for their scope as well as limitations. A comprehensive approach on the basis of polymer structure–property application is made to evaluate suitable methodology for two types of hydrogels, continuous and discrete. Representative methods for both type are suggested with detailed experimental procedures and results. The work provides com parative data with suggested methods which could be useful to the practitioner. © 1995 John Wiley & Sons, Inc.

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Preparation and characterization of microspheres of albumin-heparin conjugates

Cited by 13 publications

References 18 publications

Biodegradable ion-exchange microspheres based on modified polylysines

Biodegradable ion-exchange microspheres based on modified polylysines

Preparation and Stabilization of Heparin/Gelatin Complex Coacervate Microcapsules

On the assessment of hydrogels for fluid absorbency

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