Fabrication Of Multifunctional Mesoporous Silica Nanoparticles For The Drug Delivery And Fluorescence Imaging

Nanomaterials have played a propitious role in the noninvasive detection and treatmentof tumors because of their unique characteristics inherent to the nanoscale. In recent years, theapplication of mesoporous silica nanoparticles in drug delivery has attracted much attention,attributing to their mesoporous structure, non-toxic nature, large surface areas and porevolumes, high chemical and thermal stabilities, and versatile surface medication. In addition,multifunctional nanoparticle delivery system can be fabricated by encapsulating, coating, andincorporating diverse functional moieties (such as Au nanoparticles, superparamagneticparticles, dye molecules) onto/into silica matrices. The multifunctional nanomaterial deliverysystem with fluorescence and magnetic resonance imaging agents, pathology-specifictargeting, and drug delivery has provided a new platform for multi-mode imaging,simultaneous cancer diagnosis and therapy.In this paper, we synthesized multifunctional mesoporous silica nanomaterials possessinghollow structures and investigated their potential applications in drug delivery, cancerdiagnosis and therapy. All the relative studies are outline as follows.(1) Multifunctional hollow and rattle-type nanocapsules composed of spindle-shaped Aunanoparticles and fluorescent mesoporous silica shells have been developed by controllableetching Au nanorods coated with mesoporous SiO2 via a small amount of aqua regia as anetching agent. The etching process can be tracked by UV-Vis absorption and fluorescencespectroscopy and the size of cavities in the hollow/rattle-type nanocapsules can be tuned bycontrolling the reaction time. The dye molecules incorporated in the silica matrices enabledthe nanocapsules to be utilized as fluorescence imaging agents. In addition, thehollow/rattle-type nanocapsules were used as efficient carriers for drug loading and delivery.(2) Based on a template-coating-etching process, monodisperse hollow mesoporoussilica (HMS) nanocages with uniform size and high stability were fabricated, whichpossessing a hollow cubic core and mesoporous silica shell. Their cubic cavities and porousshells endow them with much higher drug storage capacity and sustained release property. Invitro assays demonstrated that the drug-loaded HMS nanocages have good cell uptake andcan induce efficient cell death. Additionally, in vivo experiments indicated that HMSnanocages are biocompatible and can act as carriers to deliver drugs to the tumors andsuppress tumor growth.(3) Multifunctional HMS nanocages were synthesized that combined excellent properties(fluorescence imaging, drug delivery, chemotherapy and photodynamic therapy). Dyemolecules labeled in the nanocages could be used as traceable detectors in fluorescence imaging. Chemotherapeutic drugs have been loaded into the nanocages with a high storagecapacity due to the large cubic cavities and could be released through the penetratingmesoporous channels in a sustained fashion. Photosensitizer molecules were covalently dopedin the nanocages and allow for photodynamic therapy. More importantly, a cooperative,synergistic therapy combing chemotherapy and photodynamic therapy exhibited hightherapeutic efficacy for cancer therapy in vitro.(4) Yolk-shell structured nanocapsules composed of superparamagnetic particles andfluorescent mesoporous silica shells were prepared via a facile method and the nanocapsuleswere further functionalized with biomolecular ligands for highly-targeted particles delivery.Traceable imaging of nanocapsules by fluorescence microscopy to detect liver cancer cellswere greatly enhanced under both receptor-mediated and external magnetic field-guidedtargeting.