Low molecular weight chitosan-g-l-phenylalanine: Preparation, characterization, and complex formation with DNA

The grafting of l-phenylalanine onto low molecular weight chitosan is accomplished by using carbodiimide as a coupling agent. As increase in the amount of phenylalanine in feed, the grafting chain length increases, while a number of grafting chains hardly change. The obtained product, LMWCts-g-Phe, performs sphere with an average size of ∼80 nm when the % grafting is less than 123. The complexes of the LMWCts-g-Phe and DNA (LMWCts-g-Phe/DNA) prepared by a complex coacervation method possess various shapes with an average size of ∼50–150 nm and a negatively charged surface. The LMWCts-g-Phe and its complex show very reduced toxicity to fibroblast cells. The release of DNA from the complex is very fast in high pH media (tris buffer, pH 8.0 and carbonate buffer, pH 9.5), and relatively slow or more sustainable in neutral and low pH ones (PBS, pH 7.4 and citric acid/trisodium citrate buffer, pH 3.0). The results suggest that the LMWCts-g-Phe be an alternative promising carrier for negatively charged active molecules.