A standardized in vivo protocol for ocular biodistribution of gold nanoparticles

Effective drug administration plays a pivotal role in the treatment of eye diseases. Each route of ocular administration has its advantages and limitations, but a common challenge is the low bioavailability of drugs at the target sites. New delivery nanosystems are required to ensure sufficient drug concentration over time at the target in order to improve therapeutic efficacy. Gold nanoparticles represent a promising strategy for improving drug delivery to the eye, but they can be difficult to track in biological systems. To optimize the formulations, it is crucial to understand the biodistribution profiles of nanoparticles in the eye. Designing, interpreting and compiling research on the ocular biodistribution of nanoparticles raise major challenges, particularly considering the various nanoparticle-based ocular delivery systems and the multiple available animal models. The in vivo spatiotemporal distribution of nanoparticles in the eye is generally measured at specific time points after animal euthanasia and eye collection. In this technical article, we propose a detailed standardization of in vivo protocols for ocular biodistribution studies of gold-based delivery systems in rabbits following topical application. The protocol covers all steps, including enucleation, eye dissection of various ocular tissues and their digestion, as well as ex vivo analysis of gold (Au) atom content from gold nanoparticles by inductively coupled plasma-mass spectrometry (ICP-MS) at specific time points.