Sulfated fucan as support for antibiotic immobilization

Xylofucoglucuronan from Spatoglossum schroederi algae was tested as a support for antibiotic immobilization. The polysaccharide (20 mg in 6 ml) was first activated using carbodiimide, 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide methiodide (20 mg in 2 ml), under stirring for 1 h at 25degreesC and pH from 4.5 to 5.0. After adjusting the pH to 8.0, either gentamicin or amikacin (62.5 mg in 1.25 ml) was then immobilized on this chemically modified polysaccharide with shaking for 24 h in a cold room. Infrared spectra of the activated carbodiimide xylofucoglucuronan showed two bands to carbonyl (C = O at 1647.9 and 1700.7 cm(-1)) and to amide (C-double up arrow-NH2) groups (1662.8 and 1714.0 cm(-1)). Microbial characterization of the derivatives was carried out by the disk diffusion method using Staphylococcus aureus or Klebsiella pneumoniae incorporated in Muller Hinton medium. Inhibition halos of bacterial growth were observed for the antibiotics immobilized on this sulfated heteropolysaccharide before and after dialysis. However, the halos resulting from the samples after dialysis were much smaller, suggesting that dialysis removed either non-covalently bound antibiotic or other small molecules. In contrast, bacterial growth was not inhibited by either xylofucoglucuronan or its activated form or by gentamicin or amikacin after dialysis. An additional experiment was carried out which demonstrated that the sulfated heteropolysaccharide was hydrolyzed by the microorganism. Therefore, the antibiotic immobilized on xylofucoglucuronan can be proposed as a controlled drug delivery system. Furthermore, this sulfated heteropolysaccharide can be extracted easily from sea algae Spatoglossum schroederi.