Synthesis of novel DDSA-modified levans and comparison study of environmental and biological evaluation with OSA-modified levans

Abstract

Hydrophobic modification of polysaccharides enhances their potential as emulsion stabilizers and encapsulating agents, but their biocompatibility and biodegradability must be assessed first. In this study levan polysaccharide was modified by dodecenyl succinic anhydride (DDSA) for the first time, and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and thermogravimetric and differential thermal analysis (TGA/DTA). The mentioned methods confirmed the grafting reaction and showed that the modification increases the roughness of the polysaccharide film, while thermostability and porosity of the levan stays preserved. Environmental behaviour and biocompatibility were compared for modified levans with a degree of substitution in the range of 0.032 to 0.048 prepared by octenyl succinic anhydride (OSA) or DDSA treatment at concentrations of 5 to 10 % (w/w). In a 28-day soil biodegradation test, the overall degradation of modified levans was in the range of 63–78 %. Modified levans at a concentration of up to 40 mg/mL had no adverse effects on A. fischeri bioluminescence. Also, in a test with a normal foetal lung fibroblast MRC-5 cell line, no cytotoxicity was measured for OSA- and DDSA-modified levans at concentrations up to 1 mg/mL.