Abstract
Silica based multifunctional heterostructures, exhibiting near infrared (NIR) absorption (650–1200 nm) and luminescence in the visible region, represent innovative nanosystems useful for diagnostic or theranostic applications. Herein, colloidal synthetic procedures are applied to design a photoactive multifunctional nanosystem. Luminescent silica (SiO2) coated quantum dots (QDs) have been used as versatile nanoplatforms to assemble on their surface gold (Au) seeds, further grown into Au spackled structures. The synthesized nanostructures combine the QD emission in the visible region, and, concomitantly, the distinctive NIR absorption of Au nanodomains. The possibility of having multiple QDs in a single heterostructure, the SiO2 shell thickness, and the extent of Au deposition onto SiO2 surface have been carefully controlled. The work shows that a single QD entrapped in 16 nm thick SiO2 shell, coated with Au speckles, represents the most suitable geometry to preserve the QD emission in the visible region and to generate NIR absorption from metal NPs. The resulting architectures present a biomedical potential as an effective optical multimodal probes and as promising therapeutic agents due to the Au NP mediated photothermal effect.
Highlights
Engineered photoactive nanomaterials represent a great promise for the advance of the generation of nanomedicine tools, such as tags for imaging and early-stage diagnostic and therapeutic monitoring of diseases [1,2,3]
The work aims at preparing nanostructures, with size of a few tens of nanometers, having visible light emission and near infrared (NIR) absorption, as potential colloidal systems for multimodal imaging and photothermal therapy
A visible-NIR photoactive heterostructure based on Au nanodomain decorated luminescent quantum dots (QDs)@SiO2 NPs with size in the submicrometer range have been successfully fabricated by suitably tailored colloidal strategies
Summary
Engineered photoactive nanomaterials represent a great promise for the advance of the generation of nanomedicine tools, such as tags for imaging and early-stage diagnostic and therapeutic monitoring of diseases [1,2,3]. Current research efforts are focused on the design, development and application of multifunctional nanoparticles (NPs) that simultaneously provide cancer diagnostics and therapy, such as nanostructures able to locate and selectively destroy cancer cells. Efforts to create these multicomponent nanostructures have largely been driven by their specific chemical and physical properties and by their expected functionality, which make them advantageous in applications otherwise inaccessible by their single components. Several gold (Au) based NIR absorbing materials have recently been developed, such as Au NPs of different shapes (nanorods, nanocages, agglomerates, hollow, pentagons, and large prisms) and Au composites (SiO2@Au nanoshells and superparamagnetic iron oxide nanoshells) [4,5,6,7,8], which can be investigated by different imaging modalities, such as confocal microscopy, photoacoustic tomography, computed tomography, and dark-field light scattering imaging, and can be used to deliver localized photothermal therapy [9,10,11]
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