Gene therapy is emerging as the next generation of therapeutic modality with United States Food and Drug Administration approved gene-engineered therapy for cancer and a rare eye-related disorder, but the challenge of real-time monitoring of on-target therapy response remains. In this study, we have designed a theranostic nanoparticle composed of shortwave-infrared-emitting rare-earth-doped nanoparticles (RENPs) capable of delivering genetic cargo and of real-time response monitoring. We showed that the cationic coating of RENPs with branched polyethylenimine (PEI) does not have a significant impact on cellular toxicity, which can be further reduced by selectively modifying the surface characteristics of the PEI coating using counter-ions and expanding their potential applications in photothermal therapy. We showed the tolerability and clearance of a bolus dose of RENPs@PEI in mice up to 7 days after particle injection in addition to the RENPs@PEI ability to distinctively discern lung tumor lesions in a breast cancer mouse model with an excellent signal-to-noise ratio. We also showed the availability of amine functional groups in the collapsed PEI chain conformation on RENPs, which facilitates the loading of genetic cargo that hybridizes with target gene in an in vitro cancer model. The real-time monitoring and delivery of gene therapy at on-target sites will enable the success of an increased number of gene- and cell-therapy products in clinical trials.
Keywords: gene therapy; optical-imaging contrast agent; polyethylenimine; shortwave infrared; tumor imaging.