Biodegradable intraoperative system for bone infection treatment .I. The drug/polymer interaction

In order to design and evaluate an implantable device of calcium alginate spheres releasing gentamicin sulphate to prevent or treat bone infections, the interaction between the cationic gentamicin and the polyanionic alginate was examined. Such an interaction took place, both in sodium alginate solution-as shown by rheological study, and during the Ca-induced polymer gelation which led to the formation of the calcium alginate spheres. Gentamicin sulphate was found to interact selectively on the mannuronic residues of alginate without competition with calcium ions involved in the polymer gelation. In contrast, calcium ions were found to interact preferentially at the level of the polyguluronic sequences, though polymannuronic sequences can also play a role. This prevented the saturation of the polymannuronic sequences by the drug. Therefore, the alginate having a higher mannuronic acid content, i.e. capable of associating a greater amount of drug, could be considered the more suitable material for the implant design.