A General Strategy to Encapsulate Semiconducting Polymers within PEGylated Mesoporous Silica Nanoparticles for Optical Imaging and Drug Delivery

Although semiconducting polymers (SPs) have become an important category for optical imaging and phototherapy, their biomedical application is still facing a number of challenges. Herein, a cationic surfactant–assisted approach to encapsulate hydrophobic SPs within highly PEGylated mesoporous silica (mSiO₂) nanoparticles with excellent colloidal stability and enhanced fluorescence in aqueous solution is reported. In comparison to the previously reported amphiphilic polymer coating and silification method, this universal strategy not only suppresses the formation of empty polymer micelles and free silica nanoparticles, but also provides high specific surface area for drug loading. As a proof of concept, furan-containing diketopyrrolopyrrole-based semiconducting polymers (PDFT) are coated with mesoporous silica and utilized for fluorescence imaging in the second near-infrared region (NIR-II, 1000–1700 nm) and drug delivery. In vivo blood vessel imaging and tumor imaging are achieved with high resolution (0.21 mm) and signal-to-background ratio (≈4.2). Additionally, pH-responsive drug release and improved therapeutic effect are observed. By choosing desired SPs, different optical imaging and therapeutic modalities can also be achieved, thus the SP@mSiO₂ nanostructures obtained here provide numerous opportunities for theranostic applications.