Azo polymeric hydrogels for colon targeted drug delivery

Shantha, K. L.; Ravichandran, Praveen Kumar; Rao, K. Panduranga

doi:10.1016/0142-9612(95)91046-2

Cited by 76 publications

(36 citation statements)

References 11 publications

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“…The azo dye Direct Black 38 is metabolized to the mutagen benzidine by human intestinal bacteria [48]. The ability of the bacteria residing in the human intestinal tract to reduce azo dyes has led to the development of drugs that are azo-linked to nontherapeutic moieties and polymeric azo prodrugs that provide colon-specific delivery of active metabolites [49][50][51][52]. After ingestion, the azoreductases from colonic bacteria cleave the azo bonds, releasing the drugs in their active forms [47,52,53].…”

Section: Bacteriamentioning

confidence: 99%

Recent Advances in Azo Dye Degrading Enzyme Research

Chen¹

2006

CPPS

218

125

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Azo dyes, which are characterized by one or more azo bonds, are a predominant class of colorants used in tattooing, cosmetics, foods, and consumer products. These dyes are mainly metabolized by bacteria to colorless aromatic amines, some of which are carcinogenic, by azoreductases that catalyze a NAD(P)H-dependent reduction. The resulting amines are further degraded aerobically by bacteria. Some bacteria have the ability to degrade azo dyes both aerobically and anaerobically. Plant-degrading white rot fungi can break down azo dyes by utilizing a number of oxidases and peroxidases as well. In yeast, a ferric reductase system participates in the extracellular reduction of azo dyes. Recently, two types of azoreductases have been discovered in bacteria. The first class of azoreductases is monomeric flavin-free enzymes containing a putative NAD(P)H binding motif at their N-termini; the second class is polymeric flavin dependent enzymes which are studied more extensively. Azoreductases from bacteria represent novel families of enzymes with little similarity to other reductases. Dissociation and reconstitution of the flavin dependent azoreductases demonstrate that the non-covalent bound flavin prosthetic group is required for the enzymatic functions. In this review, structures and carcinogenicity of azo colorants, protein structure, enzymatic function, and substrate specificity, as well as application of the azo dyes and azoreductases will be discussed.

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Section: Bacteriamentioning

confidence: 99%

Recent Advances in Azo Dye Degrading Enzyme Research

Chen¹

2006

CPPS

218

125

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“…The designing of prodrugs is based on the concept of preventing the release of drugs in the stomach and small intestine, and drug release is triggered by the utilization of some specific property at the target site such as altered pH or high activity of certain enzymes in comparison to nontarget tissues (Davaran et al 1999;Schacht et al 1996). Since it is known that azo function can be reduced in the colon (Chung et al 1992), a lot of novel polymers containing azo groups either in the polymeric backbone (Yamaoka et al 2000) or in the crosslinks (Shantha et al 1995; Van den Mooter et al 1992) have been synthesized. In order to promote further selective degradation in the vicinity of colonic environment, delivery systems have been designed that contain both pH-sensitive acidic monomers and degradable azo aromatic crosslinks (Chandehari et al 1997;Kakoulides et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Design and Development of Multiparticulate System for Targeted Drug Delivery to Colon

Chourasia

Jain

2004

Drug Delivery

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A multiparticulate system combining pH-sensitive property and specific biodegradability for colon-targeted delivery of metronidazole has been investigated. Cross-linked chitosan microspheres were prepared from an emulsion system using liquid paraffin as the external phase and solution of chitosan in acetic acid as the disperse phase. The multiparticulate system was prepared by coating cross-linked chitosan microspheres exploiting Eudragit R L-100 and S-100 as pH-sensitive polymers. Morphology and surface characteristics of the formulations were determined by scanning electron microscopy. Particle size of the chitosan microspheres was determined by optical microscopy while that of coated microspheres was determined by particle size analyzer. In vitro drug-release studies were performed in conditions simulating stomach-to-colon transit in presence and absence of rat caecal contents. The size of the microspheres was small and they were efficiently microencapsulated within Eudragit R microspheres, forming a multireservoir system. By coating the microspheres with Eudragit R pH-dependant release profiles were obtained. No release was observed at acidic pH; however, when it reached the pH where Eudragit R starts solublizing there was continuous release of drug from the formulation. Further, the release of drug was found to be higher in the presence of rat caecal contents, indicating the susceptibility of chitosan matrix to colonic enzymes released from rat caecal contents.

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“…Several attempts have been made to increase effective concentration and reduce toxicity via oral colon-specific delivery systems (Huang et al, 2001;Shantha et al, 1995). Precise colonic drug delivery requires that the triggering mechanism in the delivery system only responds to the physiological conditions particular to the colon.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and evaluation of the 5-fluorouracil-pectin conjugate targeted at the colon

Wang

Liu

et al. 2007

Med Chem Res

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This paper describes the first covalent synthesis of a 5-fluorouracilpectin (FU-PT) conjugate. This conjugate with the potential for colon-targeted delivery has been evaluated. A sensitive high-performance liquid chromatography (HPLC) method was established for the determination of concentration of 5-FU-1-acetic acid in the gastrointestinal contents and plasma of rats. This method was also used to evaluate the colon-targeting properties of 5-FU-PT. 5-FU-PT was given to rats by oral administration at a dosage of 22.5 mg kg -1 . The different parts of gastrointestinal tract and plasma were taken after 1, 3, 5, 7, 9, 12, 24, 36, and 48 h of oral administration of 5-FU-PT to rats, and the concentration of 5-FU-1-acetic acid in gastrointestinal contents and plasma was measured by HPLC. 5-FU-1-acetic acid released from 5-FU-PT was mainly distributed in the cecum and colon. Therefore, the present results suggest that the 5-FU-PT conjugate has a good colon-targeting property.Keywords 5-Fluorouracil Á Pectin Á Colon-specific delivery system Abbreviations FU fluorouracil PT pectin HPLC high-performance liquid chromatography DE degree of esterification DCC dicyclohexylcarbodiimide DMAP dimethylaminopyridine

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Azo polymeric hydrogels for colon targeted drug delivery

Cited by 76 publications

References 11 publications

Recent Advances in Azo Dye Degrading Enzyme Research

Recent Advances in Azo Dye Degrading Enzyme Research

Design and Development of Multiparticulate System for Targeted Drug Delivery to Colon

Synthesis and evaluation of the 5-fluorouracil-pectin conjugate targeted at the colon

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