Dual Modality Semiconducting Polymer Nanoparticles for Use in Optical and Magnetic Resonance Imaging

Semiconducting polymer nanoparticles (SPNs) hold great promise as fluorescent nanoparticles with many advantageous optical and biological properties. However, their potential for optical imaging in clinical applications is currently restricted by limited tissue penetration, compared to the depth offered by magnetic resonance imaging (MRI). Multimodal SPN‐based contrast agents that integrate different, complementary imaging modalities into one platform allow the strengths to be combined and the weaknesses mitigated. This study presents an accessible route to modular, well‐defined, and versatile dual modality SPNs composed of red‐emitting SPNs functionalized with novel gadolinium‐based contrast agents (GBCAs). The Gd unit is attached to the surface of the SPN using a rigid linker, providing a robust attachment point as well as enhancing the MRI performance. Preliminary in vitro studies show that the SPNs are nontoxic across all concentrations tested and are readily taken up by cells, illustrating their potential as imaging probes. Anchoring the GBCA unit to the surface of the SPN yields a dramatic increase in the relaxivity compared to the unattached contrast agent unit. The dual modality probe shows a fourfold relaxivity enhancement over the clinical standard, Dotarem, at clinical field strengths, making this dual modality platform a promising design for combined optical and MR imaging.