Linear Azo Polymer Containing Conjugated 5,5′‐Azodisalicylic Acid Segments in the Main Chain: Synthesis, Characterization, and Degradation

Lai, Junying; Wang, Liqun; Tu, Kehua; Zhao, Changsheng; Sun, Wen‐Hua

doi:10.1002/marc.200500550

Cited by 11 publications

(8 citation statements)

References 22 publications

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“…Dextran/OLZ hydrogels are based on degradable polysaccharide backbond combined with a redox‐sensitive aromatic azo function. In our previous research,22 the degradability of linear PEO‐OLZ copolymer in RCCM and PBS, respectively, was observed. The results show that azo bond is susceptible to degradation through a special kind of microbial enzyme, azoreductase, in the colon site of the human body.…”

Section: Resultsmentioning

confidence: 85%

“…The reason is probably that after the hydrogel swelling, the diffusion‐controlled kinetics becomes weaker, and the release of BSA is chemically controlled 2. Because the hydrolysis of the ester bonds of the hydrogels is slower than the reduction of azo bonds,22 the release rate slows down. With the incubation time prolonging, the degradation degree of the hydrolysis of the ester linkage increases in PBS, this causes loosening of the hydrogels resulting in the release rate of entrapped drug becoming fast again.…”

Section: Resultsmentioning

confidence: 99%

“…Di(2‐hydroxyethyl) 5,5′‐azodisalicylate was synthesized following the procedures of our previous work,22 i.e., OLZ was esterified by ethylene glycol with DCC as coupling agent and DMAP as basic catalyst. Briefly, OLZ (6 g, 20 mmol) and ethylene glycol (4 g, in excess) were dissolved in 40 mL of THF in a sealed flask at room temperature.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Enzyme‐based hydrogels containing dextran as drug delivery carriers: Preparation, characterization, and protein release

Lai

Fang

Wang

et al. 2009

J of Applied Polymer Sci

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Novel enzyme-based hydrogels for drug delivery were prepared by combining dextran with 5,5 0 -azodisalicylic acid using isophorone diisocyanate as the crosslinking agent. The structure of the resultant dextran/5,5 0 -azodisalicylic acid hydrogels was determined by infrared spectra, and the properties of the hydrogels were characterized by swelling measurements and scanning electron microscopy analysis. It was found that changing the concentration of 5,5 0 -azodisalicylic acid affected the crosslinking density of the hydrogels and resulted in significant differences in the water swelling property and degradability of the hydrogels. Compared with their degradability, the degradation of the hydrogels seemed to be more pronounced by azoreductase in cecum content medium than that by hydrolysis in phosphate buffer solution (PBS). Also, the release rate of the protein in cecum content medium was faster than that in PBS. Attributing to the results of the resultant hydrogels described earlier, it could be concluded that dextran/ 5,5 0 -azodisalicylic acid hydrogels could be used as a potential enzyme-based carrier for colon-specific drug delivery.

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Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

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Enzyme‐based hydrogels containing dextran as drug delivery carriers: Preparation, characterization, and protein release

Lai

Fang

Wang

et al. 2009

J of Applied Polymer Sci

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“…In our previous cecum bacterial whole-cell experiments, 15 when BV was added as a redox mediator to the cecum incubation medium, the azo bonds in OLZ were reduced up to about 90%, and the azo bonds in the PEG-OLZ copolymers were reduced by more than 50% within 4 h. At the same time, following the azo bond degradation, 5-ASA was released when the ester linkages hydrolyzed. It was found that 5-ASA was released in a sustained fashion from the aqueous PEG-OLZ copolymer solution with cecum contents in a period of more than 32 h. It was also found that the PEG 4000 -OLZ copolymer exhibited less degradation activity than the PEG 10000 -OLZ copolymer, and this was attributed mainly to the difference in their hydrophilicity (see the hydration data in Table I).…”

Section: In Vitro Degradability Of the Peg-olz Copolymersmentioning

confidence: 94%

Degradability of the linear azo polymer conjugated 5,5′‐azodisalicylic acid segment in the main chain for colon‐specific drug delivery

Lai

Wang

et al. 2008

J of Applied Polymer Sci

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A novel type of linear copolymer composed of poly(ethylene glycol) (PEG) with 5, 5 0 -azodisalicylic acid [olsalazine (OLZ)] was developed for colon-specific drug delivery. These copolymers contained azo bonds that would be degraded by the azoreductase activities in the colon. The resultant condensation polymers were characterized with Fourier transform infrared, nuclear magnetic resonance, and gel permeation chromatography. The degradation behavior of the polymer was evaluated in vitro and in vivo. The in vitro results indicated that the active 5-aminosalicylic acid (5-ASA), one of the degradation products, could be released in the medium of the cecum contents specifically. In an in vivo test, there was a 8-h lag time before 5-ASA could be detected in urine samples, and this indicated that the conjugate could remain intact in the upper part of the gastrointestinal tract. In comparison with OLZ, the release profiles of 5-ASA from PEG-OLZ copolymers were significantly prolonged. In addition, the release profiles of 5-ASA from PEG-OLZ copolymers could be adjusted by changes in the molecular weight of the PEG segment. Because of these advantages of PEG-OLZ copolymers, it could be concluded that PEG-OLZ copolymers could be promising candidates for colon-specific polymeric prodrugs of 5-ASA.

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“…The incorporation of various degradable groups into the polymer backbone allows tailoring the degradation conditions and kinetics. Azo linkages have drawn a lot of attention due to their thermal, chemical, photochemical, and biological properties. − Aromatic azo groups confer biodegradability, which enables to use them as a delivery vehicle in targeted drug delivery. − Aliphatic azo groups are thermally cleavable, creating free radicals which are used for the synthesis of block or graft copolymers . The incorporation of azo compounds into a polymer backbone opens the way to thermo- and photodegradable polymers. − …”

Section: Introductionmentioning

confidence: 99%

Polyacrylamide Containing Weak Temperature Labile Azo Links in the Polymer Backbone

Kot

Bismarck

2010

Macromolecules

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Degradable polyacrylamide (PAAm) was prepared by incorporating temperature-sensitive azo groups into the polymer backbone. Ceric ions (Ce(IV)) and 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] were used as a redox couple to initiate the polymerization of acrylamide. The presence of azo groups in the backbone of the synthesized polyacrylamide was confirmed by 1H NMR spectra, DSC, and by the fact that the polymerization of acrylonitrile could be initiated using the synthesized polyacrylamide with built-in azo groups as a macroinitiator. Drag reduction properties of the synthesized polyacrylamide with incorporated azo groups were quantified. It was found that polyacrylamide with azo links in the polymer backbone is as good a drag reducing agent as pure polyacrylamide. However, PAAm with azo links in the backbone degrades into smaller molecular weight fragments and, therefore, loses its drag reduction properties once subjected to elevated temperature, which for some applications is seen as an advantage. The degradation behavior of the PAAm with temperature-sensitive azo groups was characterized using GPC.

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Linear Azo Polymer Containing Conjugated 5,5′‐Azodisalicylic Acid Segments in the Main Chain: Synthesis, Characterization, and Degradation

Cited by 11 publications

References 22 publications

Enzyme‐based hydrogels containing dextran as drug delivery carriers: Preparation, characterization, and protein release

Enzyme‐based hydrogels containing dextran as drug delivery carriers: Preparation, characterization, and protein release

Degradability of the linear azo polymer conjugated 5,5′‐azodisalicylic acid segment in the main chain for colon‐specific drug delivery

Polyacrylamide Containing Weak Temperature Labile Azo Links in the Polymer Backbone

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