Synthesis of (99m)Tc-labeled polyaspartic acid/silica nanoassembly as a potential probe for bone imaging.

PURPOSE: Due to the efficient bone targeting of mesoporous silica nanoparticles (MSNs) and polyaspartic acid (PASP), (99m)Tc- labeled polyaspartic acid coated mesoporous silica nanoparticles (PASP-mSiO(2)-DTPA-(99m)Tc) are proposed as a potential probe for bone imaging. METHODS: Polyaspartic acid-conjugated silica nanoparticles (PASP-mSiO(2)) were synthesized using aqueous carbodiimide chemistry and characterized by ATR-FTR, FE-SEM, EDX, TEM, TGA and XRD. Radiolabeling of the produced nanoassembly with (99m)Tc was carried out via a simple DTPA chelation procedure. Aqueous dispersion of the radiolabeled nanoparticles was intravenously injected into normal mice and the bone targeting efficiency was evaluated. RESULTS: The PASP-mSiO(2) nanoassembly was efficiently synthesized and radiolabeled with (99m)Tc with a high radiochemical yield (92 ± 0.5%) and sufficient in vitro stability in PBS and FBS for up to 24 h. In vivo biodistribution studies revealed a significant enhancement of radioactivity bone uptake after intravenous injection of PASP-mSiO(2)-DTPA-(99m)Tc compared to radiolabeled uncoated MSNs (mSiO(2)-DTPA-(99m)Tc), (13 ± 0.6% IA/gram and 5.4 ± 0.4, respectively). CONCLUSION: PASP endowed MSNs with enhanced biocompatibility and highly selective bone targeting. Therefore, the proposed PASP-mSiO(2)-DTPA-(99m)Tc nanoassembly has immense potential in the field of bone- imaging via single photon emitting computed tomography (SPECT).