The negatively charged heparin and heparin-biotin were complexed with the positively charged PAMAM/DNA via electrostatic interactions to prepare PAMAM/DNA/heparin and PAMAM/DNA/heparin-biotin complexes

respectively.By using a fast degrading cholic acid functionalized star poly(DL-lactide) as a matrix and a water soluble polymer

-poly(N-2-hydroxyethyl)-L-aspartamide (PHEA) as an additive

thin films loaded with PAMAM/DNA

PAMAM/DNA/heparin or PAMAM/DNA/heparin-biotin complexes were prepared.The in vitro substrate-mediated gene transfections were carried out in HeLa cells and 293T cells.The results indicated that the complexes loaded polymer films could effectively mediate sustained transfections.The PAMAM/DNA/heparin-biotin complexes loaded polymer films exhibited improved transfection efficiency because the existence of heparin-biotin on the complex surface resulted in an enhanced cellular uptake for HeLa cells due to the specific interaction between the biotin moiety and the biotin-specific receptors on HeLa cells.By adding the water soluble polymer PHEA

which could keep the bioactivity of DNA during the film fabrication

the gene expression levels could be significantly improved.During the cellular transfection

the degradation of the polymer films did not show any negative effects on the gene transfection.