Synthesis and characterization of novel water soluble amphotericin B-arabinogalactan conjugates.

The coupling of amphotericin B (AmB), a water-insoluble antifungal agent, to arabinogalactan (AG) via an imine or amine bond was systematically investigated. AG was oxidized using potassium periodate, purified from the oxidizing agent using ion-exchange chromatography, and reacted with AmB to form the Schiff base. The Schiff base was reduced to the amine using borohydride. All reactions took place in aqueous media. The purification of the oxidized AG from the oxidizing agent was essential to prevent oxidative degradation of AmB at the coupling step. We investigated the effects of AmB to AG ratio, buffer type, and reaction pH on the reaction yield, molecular weight, conjugate activity against pathogenic yeast and hemolytic activity. The optimum coupling conditions were buffer borate 0.1 M, pH 11 at room temperature for 48 h. Lower toxicity in vivo was achieved by using low-pressure gel permeation chromatography and applying the solution of AmB-AG conjugate through a Sephadex column. Both amine and imine AmB-AG conjugates were soluble in water and exhibited improved stability in aqueous solutions as compared to the unbound drug. The conjugates showed comparable minimum inhibitory concentration (MIC) values against Candida albicans. The conjugates were about 60 times less hemolytic against sheep erythrocytes than the free drug, and about 40 times less toxic in BALB/c mice.

Synthesis and biodegradation of arabinogalactan sponges prepared by reductive amination.

The synthesis of polysaccharide-based sponges for the use in tissue engineering was systematically investigated. A comparison study of the branched polysaccharide arabinogalactan (AG) and the linear polysaccharide dextran in the formation of sponges by the reaction with diamines or polyamines was conducted. Three AG-based sponges were synthesized from the crosslinking reaction with different amine molecules. The sponges obtained were highly porous, rapidly swelled in water, and were stable in vitro for at least 11 weeks in aqueous media at 37 degrees C. AG-chitosan sponges were chosen as most suitable to serve as scaffolds for cell growth in tissue engineering. The biocompatibility in vivo of these sponges was evaluated by histological staining and non-invasive MRI technique after implantation in BALB/c mice. The sponge evoked an inflammatory response with vascularization of the implant. The inflammatory reaction decreased with time, indicating a healing process.