Gd2O3-mesoporous silica/gold nanoshells: A potential dual T1/T2 contrast agent for MRI-guided localized near-IR photothermal therapy

A promising clinical trial utilizing gold-silica core-shell nanostructures coated with poly-ethylene glycol (PEG) has been reported for near-infrared (NIR) photothermal therapy (PTT) of prostate cancer. The next critical step for PTT is the visualization of therapeutically relevant nanoshell (NS) concentrations at the tumor site. Here we report the synthesis of PEGylated Gd2O3-mesoporous silica/gold core/shell NSs (Gd2O3-MS NSs) with NIR photothermal properties that also supply sufficient MRI contrast to be visualized at therapeutic doses (>= 10(8) NSs per milliliter). The nanoparticles have r(1) relaxivities more than three times larger than those of conventional T-1 contrast agents, requiring less concentration of Gd3+ to observe an equivalent signal enhancement in T-1-weighted MR images. Furthermore, Gd2O3-MS NS nanoparticles have r(2) relaxivities comparable to those of existing T-2 contrast agents, observed in agarose phantoms. This highly unusual combination of simultaneous T-1 and T-2 contrast allows for MRI enhancement through different approaches. As a rudimentary example, we demonstrate T-1/T-2 ratio MR images with sixfold contrast signal enhancement relative to its T-1 MRI and induced temperature increases of 20 to 55 degrees C under clinical illumination conditions. These nanoparticles facilitate MRI-guided PTT while providing real-time temperature feedback through thermal MRI mapping.

Automated summary

A promising clinical trial using gold-silica core-shell nanostructures for near-infrared photothermal therapy of prostate cancer has been reported. In this study, PEGylated Gd2O3-mesoporous silica/gold core/shell nanoparticles were synthesized, which not only have near-infrared photothermal properties but also provide sufficient MRI contrast for visualization at therapeutic doses.