Theranostic nanomaterials for image-guided gene therapy

Theranostics was proposed as a combined process of therapeutics and diagnostics methodology for increasing treatment efficacy and safety with simultaneous monitoring of the response to treatment. In the past two decades, nanotechnology has been the focus of developing strategies for drug delivery and imaging functions, and it has expanded to the design of multifunctional nanoparticles and the creation of nanotheranostics (i.e., theranostic nanomedicines). Nanotheranostics also shows potential in gene therapy; however, nanoparticle-mediated delivery of genes still faces major obstacles related to (1) the uptake by the reticuloendothelial system, (2) the ability to get across the target cell membranes through endocytosis, and (3) the ability to accumulate in organs with permeable vasculature. Here, we review the development and application of nanotheranostics, highlighting their relevance to gene therapy as well as molecular imaging.