In Vivo Micro-CT Imaging of Human Mesenchymal Stem Cells Labeled with Gold-Poly- l -Lysine Nanocomplexes

Developing in vivo cell tracking is an important prerequisite for further development of cell-based therapy. So far, few computed tomography (CT) cell tracking studies have been described due to its notoriously low sensitivity and lack of efficient labeling protocols. A simple method is presented to render human mesenchymal stem cells (hMSCs) sufficiently radiopaque by complexing 40 nm citrate-stabilized gold nanoparticles (AuNPs) with poly-l-lysine (PLL) and rhodamine B isothiocyanate (RITC). AuNP-PLL-RITC labeling does not affect cellular viability, proliferation, or downstream cell differentiation into adipocytes and osteocytes. Labeled hMSCs can be clearly visualized in vitro and in vivo with a micro-CT scanner, with a detection limit of ≈2 × 104 cells per µL in vivo. Calculated Hounsfield unit values are 2.27 per pg of intracellular Au, as measured with inductively coupled plasma ma…