WRAP-based nanoparticles for siRNA delivery in zebrafish embryos by simple bath immersion

The use of RNA interference (RNAi) is becoming more widespread in several areas of biomedical research. However, the success of RNAi depends on the effective delivery of siRNA <i>in vitro</i> or <i>in vivo</i>. Efforts are under way to identify universally effective delivery systems. Promising candidates include cell-penetrating peptides, such as the WRAP (tryptophan and arginine-rich amphipathic peptide) family, which forms nanoparticles in the presence of short interfering RNA (siRNA). Here, we optimized the WRAP-based nanoparticles for zebrafish embryo transfection by first determining the ideal formulation compatible with the saline solution required for zebrafish embryo care. We found that adding 20% polyethylene glycol (PEG) to the WRAP1 nanoparticles provided the best nanoparticles in terms of size (around 100 nm) and uniformity (PdI ≤0.3), compared with other nanoparticles tested. We then performed a simple soaking procedure in which we exposed dechorionated zebrafish embryos expressing GFP in their vascular cells to siRNA-loaded 20% PEG-WRAP1 nanoparticles. Under these conditions, we showed dose-dependent siRNA internalization and efficient GFP silencing. Although still in its early stages, this proof-of-concept study provides promising prospects for further <i>in vivo</i> research in zebrafish embryos to evaluate the efficacy of gene silencing using PEGylated WRAP1 nanoparticles by skin transfection in a pathophysiological context.