Biodistribution of Stealth and Non-stealth Solid Lipid Nanospheres after Intravenous Administration to Rats

Drug‐free stealth and non‐stealth solid lipid nanospheres (SLNs) were administered intravenously to rats to evaluate their tissue distribution and their transport across the blood‐brain barrier. Two types of experiments were performed using unlabelled and labelled SLNs. Rats were administered labelled non‐stealth or stealth nanospheres (NSSLNs and SSLNs) and their tissue distribution was monitored for 60 min. In another experiment, rats were injected with unlabelled NSSLNs or SSLNs and the cerebrospinal fluid (CSF) was analysed using transmission electron microscopy (TEM) to confirm the presence of the SLNs. Some differences were found in the biodistribution between labelled NSSLNs and SSLNs. In particular, the radioactivity in the liver and the lung was much lower for SSLNs than for NSSLNs, confirming a difference in their uptake. Both types of SLNs were detected in the brain. TEM analysis showed both types of SLNs in rat CSF.