Multifunctional mesoporous silica nanocomposite nanoparticles for theranostic applications. 
Clever combinations of different types of functional nanostructured materials will enable the development of multifunctional nanomedical platforms for multimodal imaging or simultaneous diagnosis and therapy.  Mesoporous silica nanoparticles (MSNs) possess unique structural features such as their large surface areas, tunable nanometer-scale pore sizes, and well-defined surface properties.  Therefore, they are ideal platforms for constructing multifunctional materials that incorporate a variety of functional nanostructured materials.  In this Account, we discuss recent progress by our group and other researchers in the design and fabrication of multifunctional nanocomposite nanoparticles based on mesoporous silica nanostructures for applications to simultaneous diagnosis and therapy.  Versatile mesoporous silica-based nanocomposite nanoparticles were fabricated using various methods.  Here, we highlight two synthetic approaches: the encapsulation of functional nanoparticles within a mesoporous silica shell and the assembly of nanoparticles on the surface of silica nanostructures.  Various nanoparticles were encapsulated in MSNs using surfactants as both phase transfer agents and pore-generating templates.  Using MSNs as a scaffold, functional components such as magnetic nanoparticles and fluorescent dyes have been integrated within these systems to generate multifunctional nanocomposite systems that maintain their individual functional characteristics.  For example, uniform mesoporous dye-doped silica nanoparticles immobilized with multiple magnetite nanocrystals on their surfaces have been fabricated for their use as a vehicle capable of simultaneous magnetic resonance (MR) and fluorescence imaging and drug delivery.  The resulting nanoparticle-incorporated MSNs were then tested in mice with tumors.  These in vivo experiments revealed that these multifunctional nanocomposite nanoparticles were delivered to the tumor sites via passive targeting.  These nanocomposite nanoparticles served as successful multimodal imaging probes and also delivered anticancer drugs to the tumor site.  With innumerable combinations of imaging modalities and drug delivery available within these vehicles, multifunctional nanocomposite nanoparticles provide new opportunities for clinical diagnostics and therapeutics.