Effect of Pluronic‐block copolymers on the reduction of serum‐mediated inhibition of gene transfer of polyethyleneimine–DNA complexes

Serum stability of non‐viral vectors is a crucial factor for successful in vivo gene delivery. Pluronic‐block copolymers consisting of hydrophilic ethylene oxide and hydrophobic propylene oxide blocks were tested to prevent the reduction of serum‐mediated inhibition of gene transfer of polyethyleneimine (PEI)–DNA complexes in NIH/3T3 cells. The order of hydrophilic–lipophilic balance (HLB) of six different types of Pluronics used in this study was F68>F127>P105>P94>L122>L61. Transfection activities of NIH/3T3 cells with PEI–DNA complexes containing Pluronics with higher HLB showed marked improvement of gene‐expression levels in serum media from 10 to 50% fetal bovine serum compared with PEI–DNA complexes alone. Also, higher concentrations (1 and 3%) of Pluronics with higher HLB in the PEI/DNA dispersion provided a stronger steric hindrance in resisting serum components than those obtained in a lower concentration (0.1%). These results suggested that non‐viral vectors incorporated with higher HLB of Pluronics may be used as potential vehicles for in vivo delivery of DNA.