Efficient in vitro gene delivery by hybrid biopolymer/virus nanobiovectors

Recombinant retroviruses provide highly efficient gene delivery and the potential for sustained gene expression, but suffer from significant disadvantages including low titer, expensive production, poor stability and limited flexibility for modification of tropism. In contrast, polymer-based vectors are more robust and allow cell- and tissue-specific deliveries via conjugation of ligands, but are comparatively inefficient. The design of hybrid gene delivery agents comprising both virally derived and synthetic materials (nanobiovectors) represents a promising approach to development of safe and efficient gene therapy vectors. Non-infectious murine leukemia virus-like particles (M-VLPs) were electrostatically complexed with chitosan (χ) to replace the function of the viral envelope protein. At optimal fabrication conditions and compositions, ranging from 6 to 9 μg chitosan/10⁹ M-VLPs at 10 × 10⁹ M-VLPs/ml to 40 μg chitosan/10 ⁹ M-VLPs at 2.5 × 10⁹ M-VLPs/ml, χ/M-VLPs were ∼ 300-350 nm in diameter and exhibited efficient transfection similar to amphotropic MLV vectors. In addition, these nanobiovectors were non-cytotoxic and provided sustained transgene expression for at least three weeks in vitro. This combination of biocompatible synthetic agents with inactive viral particles to form a highly efficient hybrid vector is a significant extension in the development of novel gene delivery platforms.