The problem with cationic liposome/micelle-based non-viral vector systems for gene therapy

Gene therapy research is in crisis owing to the lack of acceptable vector systems to deliver nucleic acids to patients for therapy. Viral vectors are efficient but currently appear to be too dangerous for routine clinical use. Synthetic non-viral vectors are inherently much safer but are currently not efficient enough to be clinically viable. The solution for gene therapy lies with improved synthetic non-viral vectors based upon well-found platform technologies and a thorough understanding of the barriers to efficient gene delivery and expression (transfection) relevant to clinical applications of interest. In this review, the current status and prospects for cationic liposome/micelle-based synthetic non-viral vector systems are discussed including a description of the barriers to efficient transfection, a summary of the main structure/activity studies and mention of ternary cationic liposome/micelle-nucleic acid (LD) systems. The review culminates with a description of two promising cationic liposome/micelle-based non-viral vector platform systems known as liposome:mu:DNA (LMD) and stabilised plasmid-lipid particles (SPLP) that should create a real opportunity for the development of clinically viable synthetic vector systems within the next few years.