Testing nanoparticles for angiogenesis-related disease: charting the fastest route to the clinic

Recently, nanoparticles (NPs) have been established as ideal drug delivery vehicles for treating cancer. This is due to the enhanced permeability and retention (EPR) effect that is a direct result of the angiogenic nature of the tumor tissue and its ability to sequester chemotherapeutics from healthy tissues. Ideal drug delivery nanocarriers will exploit the EPR effect, accumulate in the tumorous tissue, and be able to release the drugs at a high concentration where needed, thereby reducing undesirable side effects. In order to determine ideal NP qualities that enable drugs to be delivered in such a manner, extensive testing in biological systems is required. However, it is impractical to study new potential nanocarriers in humans or in mammalian models due to the potential adverse consequences, low throughput, and high cost. Simpler models would allow for higher throughput screening of nanocarrier vehicles. This review outlines the most recent advances in alternative model assays and their significance in testing NPs en route to the clinic. In decreasing complexity, we examine zebrafish embryos, the chorioallantoic membrane of the chicken embryo, multicell static and flow-based assays, and single cell assays for efficacy, accuracy and utility as predictors for human therapeutic outcomes.