Purpose. A novel siRNA carrier was formulated between chitosan (CS) and thiamine pyrophosphate (TPP). Their ability to deliver siRNAwere evaluated in stable and constitutive EGFP-expressing HepG2 cells.

Methods. CS-TPP was prepared by dissolvingCS in TPP solution at a CS:TPPmolar ratio of 1.5:1. Complexes of CS-TPP/siRNA were formed at varying weight ratios and characterized using gel electrophoresis. Their morphologies and particle sizes were evaluated, and the transfection efficiency and cytotoxicity of CS-TPP/siRNA complexes were examined in stable and constitutive EGFP-expressing HepG2 cells.

Results. Gel electrophoresis results indicated that binding of CS-TPP and siRNA depended on the molecular weight (MW) and weight ratio of CS, and the particle sizes of CS-TPP/siRNA complexes were in nano-size. The CS-TPP-mediated siRNA silencing of the endogenous EGFP gene occurred maximally with 70–73% efficiency. The CS-TPP/siRNA complex with the lowest MW of CS (20 kDa) at a weight ratio of 80 showed the strongest inhibition of gene expression, which was higher than Lipofectamine 2000™. Over 90% the average cell viabilities of the complexes were observed by MTT assay.

Conclusions. This study suggests that CS-TPP is straightforward to prepare, safe and exhibits significantly improved siRNA delivery potential in vitro.