MECHAnized NANOmachines for two-photon activation – MECHANANO

The proposed research program is a multi-faceted study of multifunctional mechanized nanoparticles. It is a collaborative effort between ICGM, UR1 and UCLA and combines the expertise of the French groups (2-photon photochemistry and photophysics and organic/inorganic mesoporous materials) with that of the U.S. group (multifunctional mesoporous silica nanoparticles with pore openings controlled by molecular machines). The primary objective is to design, synthesize and operate nanoparticles that trap and release molecules by 2-photon activation which is motivated by potential applications in biological photodynamic therapy.
Multifunctional nanomaterials which carry out two or more functions simultaneously, are attracting increasing attention. Of particular importance to this proposal are materials activated by light that are luminescent (for imaging) and respond to light in useful ways. Well known monofunctional nanomaterials are quantum dots for imaging, and gold nanorods for hyperthermal effects. The new function to be explored in this proposal is trapping and photo-stimulated release of cargo molecules with applications to drug delivery. Photo-functional materials offer the advantages of non-invasive external control, temporal (on and off) control, and spatially localized control (in illuminated regions). The mesostructure of the particles provides the cargo-carrying function, and grafting of fluorescent molecules provides the imaging function.
The recent resurgence in 2-photon photophysical and photochemical research is motivated in part by biological applications. Visible and UV light do not penetrate biological tissue very deeply, thus limiting applications to surfaces. Red and near-IR light has much deeper tissue penetration and is not as damaging to biomolecules, but lacks the energy to carry out many desired photochemical and photophysical functions. 2-photon activation (TPE) has the properties of deep tissue penetration (due to the long wavelengths used) and energetic excitation (due to the additive nature of the process). Another advantage is the increased spatial (3D) control at the focal point of the excitation (e.g. 3D lithography).
In all cases, the TPE is the “trigger” that causes the nanomachine to respond with a large amplitude motion that allows trapped molecules in the pores of the mesoporous nanoparticle to escape into the external solution.
The 1st goal in the research towards TPE of mechanized nanoparticles is direct activation of the nanomachine itself. The limitations are that the machine must be photoactive and must also be designed to have a large 2-photon cross section.
The 2nd goal is indirect activation where a molecule with a large 2-photon cross section is excited and then passes the excitation energy along to the nanomachine. Forster energy transfer from the transducer (acting as the energy donor) to the nanomachine (acting as the acceptor) will be used to power nanomachines.
The third goal is to use the particle itself as the transducer. We will design and synthesize organic/inorganic nanoparticles with high 2-photon cross sections. The results of the proposed studies will be a new generation of functional mechanized nanomaterials that are stimulated by 2-photon photochemical and photophysical processes. By combining the strengths of the French and American research groups, both new understanding and new materials will be developed. These materials may have important biological applications (including on-command drug delivery) because of the deep tissue penetration and the 3D spatial control of the TPE