Stem cell therapy has shown great potential in treating a wide range of diseases including cancer. The real-time tracking of stem cells with high spatiotemporal resolution and stable imaging signals remains the bottleneck to evaluate and monitor therapeutic outcomes once transplanted into patients. Here, we developed a photosensitive mesenchymal stem cell (MSC) loaded with mesoporous silica-coated gold nanostars (MGNSs) integrated with indocyanine green for spatiotemporal tracking and imaging-guided photothermal therapy (PTT) in treating breast cancers. The MGNS served as a stable imaging probe with multifunctional properties for photoacoustic imaging (PAI), fluorescence imaging, and PT imaging. Owing to the excellent PT stability of MGNSs, long-term three-dimensional (3D) PAI was achieved to monitor stem cells in real time at the tumor site, while the tumor structure was imaged using 3D B-mode ultrasound imaging. PAI revealed that the photosensitive stem cells reached the widest distribution area at the tumor site post 24 h of intratumoral injection, which was further confirmed via two-dimensional (2D) PT and fluorescence imaging. With this optimal cell distribution window, in vivo studies showed that the photosensitive stem cells via both intratumoral and intravenous injections successfully inhibited breast cancer cell growth and decreased the tumor recurrence rate post PTT. Our results support that this photo-integrated platform with stable optical properties is promising to achieve real-time tracking and measure the cell distribution quantitatively with high spatiotemporal resolution for stem cell therapy.
Keywords: gold nanostar; photoacoustic imaging; photostable nanoprobe; photothermal therapy; stem cell tracking.