Over the past decade, the capability of double-stranded RNAs to interfere with gene expression has driven new therapeutic approaches. Since small interfering RNA (siRNAs, 21 base pair double-stranded RNA) was shown to be able to elicit RNA interference (RNAi), efforts were directed toward the development of efficient delivery systems to preserve siRNA bioactivity throughout the delivery route, from the administration site to the target cell. Here we provide evidence of RNAi triggering, specifically silencing c-myc protooncogene, via the synthesis of a library of novel multifunctional gold nanoparticles (AuNPs). The efficiency of the AuNPs is demonstrated using a hierarchical approach including three biological systems of increasing complexity: in vitro cultured human cells, in vivo invertebrate (freshwater polyp, Hydra ), and in vivo vertebrate (mouse) models. Our synthetic methodology involved fine-tuning of multiple structural and functional moieties. Selection of the most active functionalities was assisted step-by-step through functional testing that adopted this hierarchical strategy. Merging these chemical and biological approaches led to a safe, nonpathogenic, self-tracking, and universally valid nanocarrier that could be exploited for therapeutic RNAi.

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Light polymer nanotransducers control cell functions in vivo.

Gold nanoparticles have emerged as novel safe and biocompatible tools for manifold applications, including biological imaging, clinical diagnostics, and therapeutics. The understanding of the mechanisms governing their interaction with living systems may help the design and development of new platforms for nanomedicine. Here we characterized the dynamics and kinetics of the events underlying the interaction of gold nanoparticles with a living organism, from the first interaction nanoparticle/cell membrane, to the intracellular trafficking and final extracellular clearance. By treating a simple water invertebrate (the cnidarian Hydra polyp) with functionalized gold nanoparticles, multiple inward and outward routes were imaged by ultrastructural analyses, including exosomes as novel undescribed carriers to shuttle the nanoparticles in and out the cells. From the time course imaging a highly dynamic picture emerged in which nanoparticles are rapidly internalized (from 30 min onward), recruited into vacuoles/endosome (24 h onward), which then fuse, compact and sort out the internalized material either to storage vacuoles or to late-endosome/lysosomes, determining almost complete clearance within 48 h from challenging. Beside classical routes, new portals of entry/exit were captured, including exosome-like structures as novel undescribed nanoparticle shuttles. The conservation of the endocytic/secretory machinery through evolution extends the value of our finding to mammalian systems providing dynamics and kinetics clues to take into account when designing nanomaterials to interface with biological entities.

The possibility to remotely manipulate intracellular pathways in single cells is among the current goals of biomedicine, demanding new strategies to control cell function and reprogramming cell fate upon external triggering. Optogenetics is one approach in this direction, allowing specific cell stimulation by external illumination. Here, we developed optical switchers of an ancient and highly conserved system controlling a variety of developmental and adult processes in all metazoans, from Hydra to mammals, the Wnt/β-catenin signaling pathway. An intracellular modulator of the Wnt pathway was enclosed into polyelectrolyte multilayer microcapsules engineered to include self-tracking (i.e., fluorescence labeling) and light mediated heating functionalities (i.e., plasmonic nanoparticles). Capsules were delivered in vivo to Hydra and NIR triggered drug release caused forced activation of the Wnt pathway. The possibility to remotely manipulate the Wnt pathway by optical switchers may be broadly translated to achieve spatiotemporal control of cell fate for new therapeutic strategies.