Dextran hydrogels for colon-specific drug delivery

Hovgaard, Lars; Brøndsted, H.V.

doi:10.1016/0168-3659(95)00049-e

Cited by 205 publications

(114 citation statements)

References 20 publications

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“…Enzymatic degradation of the uncoated dextran microspheres was carried out using dextranase and 2% rat cecal contents (Hovgaard & Brondsted, 1995). Weighed amount of microspheres (100 mg) was suspended separately in 5 mL of phosphate buffer, pH 7.4 containing 0.7 IU/mL dextranase or 2% rat cecal contents or without dextranase and 2% rat cecal contents and agitated on the shaker at 37 ± 0.5 C at 50 rpm for 24 h. The residue was washed with water, centrifuged and dried in oven at 37 ± 0.5 C until the constant weight was reached.…”

Section: In Vitro Enzymatic Degradationmentioning

confidence: 99%

Eudragit-coated dextran microspheres of 5-fluorouracil for site-specific delivery to colon

et al. 2014

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Objective of the present investigation was to prepare and evaluate the potential of enteric coated dextran microspheres for colon targeting of 5-fluorouracil (5-FU). Dextran microspheres were prepared by emulsification-crosslinking method and the formulation variables studied included different molecular weights of dextran, drug:polymer ratio, volume of crosslinking agent, stirring speed and time. Enteric coating (Eudragit S-100) of dextran microspheres was performed by oil-in-oil solvent evaporation method using different coat:core ratios (4:1 or 8:1). Uncoated and coated dextran microspheres were characterized by particle size, surface morphology, entrapment efficiency, DSC, in vitro drug release in the presence of dextranase and 2% rat cecal contents. The release study of 5-FU from coated dextran microspheres was pH dependent. No release was observed at acidic pH; however, the drug was released quickly where Eudragit starts solublizing there was continuous release of drug from the microspheres. Organ distribution study was suggested that coated dextran microspheres retard the release of drug in gastric and intestinal pH environment and released of drug from microspheres in colon due to the degradation of dextran by colonic enzymes.

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Section: In Vitro Enzymatic Degradationmentioning

confidence: 99%

Eudragit-coated dextran microspheres of 5-fluorouracil for site-specific delivery to colon

et al. 2014

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“…Gels with different equilibrium swelling ratios and physical properties were obtained. These dextran-based hydrogels may have special use as drug delivery matrices for colonic targeting, particularly because of their expected degradation by dextranases, which are known to be present in the colon [17].…”

Section: Introductionmentioning

confidence: 99%

Enzymatic synthesis of dextran-containing hydrogels

2002

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Dextran, a natural glucose-containing polysaccharide, has been acylated by Proleather FG-F and lipase AY, a protease and lipase from Bacillus sp. and Candida rugosa, respectively, in anhydrous dimethylsulfoxide in the presence of vinyl acrylate (VA). The efficiency of the reaction in the presence of Proleather FG-F and the isolated yields were ca. 71% and 45%, respectively. Dextran derivatized with VA (dexT70-VA) was characterized by gel permeation chromatography and its structure was established by NMR indicating two positional isomers at the 2 and 3 positions on the glucose moieties in equal amounts. Furthermore, the dextran glucopyranose residues were mono-substituted. The benefits of the biocatalytic synthesis of dextran acrylates was demonstrated using 4-dimethylaminopyridine as a chemical catalyst. Gels were prepared by free radical polymerization of aqueous solutions of dexT70-VA with different degrees of substitution and monomer concentrations. Intermolecular linkages and physical entanglements are predominantly formed by concentrated solutions, however, a part of the acrylate groups did not react. Gel pore sizes were calculated from swelling experiments and ranged from ca. 18 to 182 ( A. r

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“…Microbial populations in the colon may express reductive or hydrolytic enzymes and are able to degrade various types of polysaccharides including pectin, CS, cyclodextrin and dextrin. Because the microbial enzyme dextranase can degrade the polysaccharide dextran, it has been exploited in formulations of drug delivery systems for the colon (Hovgaard & Brøndsted, 1995;Jain et al, 2007).…”

Section: Enzyme-sensitive Polymersmentioning

confidence: 99%

Classification of stimuli–responsive polymers as anticancer drug delivery systems

et al. 2014

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Although several anticancer drugs have been introduced as chemotherapeutic agents, the effective treatment of cancer remains a challenge. Major limitations in the application of anticancer drugs include their nonspecificity, wide biodistribution, short half-life, low concentration in tumor tissue and systemic toxicity. Drug delivery to the tumor site has become feasible in recent years, and recent advances in the development of new drug delivery systems for controlled drug release in tumor tissues with reduced side effects show great promise. In this field, the use of biodegradable polymers as drug carriers has attracted the most attention. However, drug release is still difficult to control even when a polymeric drug carrier is used. The design of pharmaceutical polymers that respond to external stimuli (known as stimuli-responsive polymers) such as temperature, pH, electric or magnetic field, enzymes, ultrasound waves, etc. appears to be a successful approach. In these systems, drug release is triggered by different stimuli. The purpose of this review is to summarize different types of polymeric drug carriers and stimuli, in addition to the combination use of stimuli in order to achieve a better controlled drug release, and it discusses their potential strengths and applications. A survey of the recent literature on various stimuli-responsive drug delivery systems is also provided and perspectives on possible future developments in controlled drug release at tumor site have been discussed.

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Dextran hydrogels for colon-specific drug delivery

Cited by 205 publications

References 20 publications

Eudragit-coated dextran microspheres of 5-fluorouracil for site-specific delivery to colon

Eudragit-coated dextran microspheres of 5-fluorouracil for site-specific delivery to colon

Enzymatic synthesis of dextran-containing hydrogels

Classification of stimuli–responsive polymers as anticancer drug delivery systems

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