The cell tracing agent Cell Sense (CS-1000) is an inert, non-metabolizable tracer. As CS-1000 is taken-up and incorporated into the cell traditional pharmacodynamic and pharmacokinetic analyses in animals and humans are not appropriate, as adsorption and biodistribution will vary with cell type, and therefore have not been done. In vitro studies of toxicity towards various cell types did not yield evidence of adverse effects on various cell functions. Cell Sense also was shown to be non-mutagenic using the Ames and Forward thymidine kinase (TK) assays. Some limited skin irritation was observed when >2,500 fold more Cell Sense than expected to be maximally injected into humans was injected intradermally into rats.