Biocompatibility and biodistribution of surface-enhanced Raman scattering nanoprobes in zebrafish embryos: in vivo and multiplex imaging

Nanoparticles are increasingly being used to investigate biological processes in various animal models due to their versatile chemical, unique optical, and multifunctional properties. In this report we address the biocompatibility and biodistribution of nanoparticle sensors used for Raman chemical imaging in live zebrafish (Danio rerio) embryos. Surface-enhanced Raman scattering (SERS) nanoprobes (NPs) comprising gold nanoparticles (AuNPs) as enhancing substrate and nonfluorescent Raman labels were synthesized and microinjected into zebrafish embryos at the one-cell stage. Raman mapping was performed to assess their distribution in various cell-types and tissues of developing embryo at five different stages between 6 and 96 hpf (hours post-fertilization). Biocompatibility and toxicity studies indicate that the NPs are not toxic and the embryos were found to exhibit normal morphological and gene expression in addition to the proper form and function of major organs such as the heart and vasculature (of 7 day old NPs injected zebrafish embryos). A multiplex in vivo detection protocol was developed by SERS imaging to demonstrate that multiple labels can be detected by Raman mapping in undifferentiated cells as they develop into distinct cell- and tissue-types. The present work is the first to report on multiplex Raman imaging of zebrafish embryos with potential implications in tracking tissue development and biological processes at single molecule sensitivity using appropriate target molecules in vivo.