The in vitro evaluation of 'azo containing polysaccharide gels' for colon delivery

J Control Release. 2001 Jul 10;75(1-2):103-14. doi: 10.1016/s0168-3659(01)00367-4.

Abstract

This study reports on 'azo-polysaccharide gels', more specifically azo-inulin and azo-dextran gels, for colon drug delivery. Compared with azo-hydrogels which can be only degraded by reduction of the azo-groups, this study evaluates whether, in vitro, azo-polysaccharide gels can be degraded through both reduction of the azo-groups in the crosslinks as well as enzymatic break down of the polysaccharide backbone. The azo-polysaccharide gels were synthesized by radical crosslinking of a mixture of methacrylated inulin or methacrylated dextran and N,N'-bis(methacryloylamino)azobenzene (B(MA)AB) and were characterized by dynamic mechanical analysis and swelling measurements. Azo-dextran gels could be obtained from methacrylated dextran having low degree of substitution but not from lowly substituted methacrylated inulin. Increasing the amount of B(MA)AB resulted in denser azo-inulin and azo-dextran networks. Compared with their swelling in dimethylformamide, all azo-dextran gels became more swollen in water while azo-inulin gels shrank upon exposure to water, indicating a more hydrophobic character of the azo-inulin gels. Break down of the inulin and dextran chains in the azo-polysaccharide gels by inulinase and dextranase, respectively, was observed. However, the degradation of azo-dextran gels by dextranase seemed to be more pronounced than the degradation of the azo-inulin gels by inulinase. In rat caecal content medium, reduction of the azo function in azo-inulin gels was not observed. This may be attributed to a low partitioning of nicotinamide-adenine dinucleotide phosphate (NADP(+)) in the gels.

MeSH terms

  • Algorithms
  • Animals
  • Azo Compounds / chemistry*
  • Cecum / metabolism
  • Colon / metabolism*
  • Dextrans / chemistry
  • Drug Delivery Systems*
  • Flavin-Adenine Dinucleotide / chemistry
  • Gels
  • Hydrolysis
  • In Vitro Techniques
  • Inulin / chemistry
  • Male
  • NADP / chemistry
  • Polysaccharides / chemistry*
  • Rats
  • Rats, Wistar

Substances

  • Azo Compounds
  • Dextrans
  • Gels
  • Polysaccharides
  • Flavin-Adenine Dinucleotide
  • NADP
  • Inulin